مرتب سازی بر اساس: سال انتشار
(نزولی)
Magnetic Resonance Materials in Physics, Biology and Medicine (13528661) 38(2)pp. 299-315
Objective: This study presents a novel deep learning-based framework for precise brain MR region segmentation, aiming to identify the location and the shape details of different anatomical structures within the brain. Materials and methods: The approach uses a two-stage 3D segmentation technique on a dataset of adult subjects, including cognitively normal participants and individuals with cognitive decline. Stage 1 employs a 3D U-Net to segment 13 brain regions, achieving a mean DSC of 0.904 ± 0.060 and a mean HD95 of 1.52 ± 1.53 mm (a mean DSC of 0.885 ± 0.065 and a mean HD95 of 1.57 ± 1.35 mm for smaller parts). For challenging regions like hippocampus, thalamus, cerebrospinal fluid, amygdala, basal ganglia, and corpus callosum, Stage 2 with SegResNet refines segmentation, improving mean DSC to 0.921 ± 0.048 and HD95 to 1.17 ± 0.69 mm. Results: Statistical analysis reveals significant improvements (p-value < 0.001) for these regions, with DSC increases ranging from 1.3 to 3.2% and HD95 reductions of 0.06–0.33 mm. Comparisons with recent studies highlight the superior performance of the performed method. Discussion: The inclusion of a second stage for refining the segmentation of smaller regions demonstrates substantial improvements, establishing the framework’s potential for precise and reliable brain region segmentation across diverse cognitive groups. © The Author(s), under exclusive licence to European Society for Magnetic Resonance in Medicine and Biology (ESMRMB) 2025.
Scientific Reports (20452322) 15(1)
In PET systems, the SNR relies on the coincidence time resolution (CTR) of 511 keV photon pairs. This research investigates the impact of reflectors, surface treatments, materials, and scintillation crystal length on the CTR of a brainPET detector using dual-layer offset scintillators (DLOs). This study is based on a brainPET, under development at the University of Manitoba, to propose a new design to achieve an improved CTR. Four different pairs of LYSO crystals with distinct optical compositions, surface treatments, and reflective materials were simulated (using GATEv9.3). Each model comprises two LYSO crystal with dimensions of 3 × 3 × 10 mm3. Considering the initial experimental data from the brainPET lab, simulation results showed that the crystal with a roughened surface and ESR reflector demonstrated 13.6% energy resolution and an average 17.8% improvement in CTR compared to other models. In addition, a more comprehensive model, including a dual-layer offset detector was designed. The bottom and top layers have 25 × 19 and 24 × 18 crystals with thickness of 12 and 8 mm, respectively in the DLO model. The simulation investigation showed that the DLO configuration could enhance the time resolution by 17.5% and the energy resolution by 5.4% which are considerably comparable to the state-of-the-art brainPET systems. © The Author(s) 2025.
This study aims to evaluate the performance of transformer-based models learned on segmenting cardiac systolic abnormalities using a dataset comprising 1717 cardiac catheterization X-ray images. This study evaluated the segmentation performance of seven transformer architectures, including Swin-UNet, MaskFormer, AgileFormer, Swin Transformer, DETR, MaxViT, and SETR. Swin-UNet and MaskFormer had the best dice coefficients and accuracy among all models tested. Swin-UNet achieved an accuracy of 9 9. 3 1% and a dice coefficient of 9 8. 5 4%, and MaskFormer achieved an accuracy of 9 8. 4 9% and a dice coefficient of 99.78%, indicating their high segmentation performance. The results thus show the substantial benefits transformer-based models offer in medical imaging, with improvements in diagnostic accuracy and potential for clinical practice. The research allows future studies to develop these models and examine their wider cardiological use. © 2024 IEEE.
Journal Of Medical Signals And Sensors (22287477) 14(3)
Background: Brain tumor segmentation is highly contributive in diagnosing and treatment planning. Manual brain tumor delineation is a time-consuming and tedious task and varies depending on the radiologist's skill. Automated brain tumor segmentation is of high importance and does not depend on either inter- or intra-observation. The objective of this study is to automate the delineation of brain tumors from the Fluid-attenuated inversion recovery (FLAIR), T1-weighted (T1W), T2-weighted (T2W), and T1W contrast-enhanced (T1ce) magnetic resonance (MR) sequences through a deep learning approach, with a focus on determining which MR sequence alone or which combination thereof would lead to the highest accuracy therein. Methods: The BraTS-2020 challenge dataset, containing 370 subjects with four MR sequences and manually delineated tumor masks, is applied to train a residual neural network. This network is trained and assessed separately for each one of the MR sequences (single-channel input) and any combination thereof (dual- or multi-channel input). Results: The quantitative assessment of the single-channel models reveals that the FLAIR sequence would yield higher segmentation accuracy compared to its counterparts with a 0.77 ± 0.10 Dice index. As to considering the dual-channel models, the model with FLAIR and T2W inputs yields a 0.80 ± 0.10 Dice index, exhibiting higher performance. The joint tumor segmentation on the entire four MR sequences yields the highest overall segmentation accuracy with a 0.82 ± 0.09 Dice index. Conclusion: The FLAIR MR sequence is considered the best choice for tumor segmentation on a single MR sequence, while the joint segmentation on the entire four MR sequences would yield higher tumor delineation accuracy. © 2024 Journal of Medical Signals & Sensors.
Ghane, B. ,
Karimian, A.R. ,
Mostafapour, S. ,
Gholamiankhak, F. ,
Shojaerazavi, S. ,
Arabi, H. Journal Of Medical Signals And Sensors (22287477) 13(2)pp. 118-128
Background: Computed tomography (CT) scan is one of the main tools to diagnose and grade COVID-19 progression. To avoid the side effects of CT imaging, low-dose CT imaging is of crucial importance to reduce population absorbed dose. However, this approach introduces considerable noise levels in CT images. Methods: In this light, we set out to simulate four reduced dose levels (60% dose, 40% dose, 20% dose, and 10% dose) of standard CT imaging using Beer-Lambert's law across 49 patients infected with COVID-19. Then, three denoising filters, namely Gaussian, bilateral, and median, were applied to the different low-dose CT images, the quality of which was assessed prior to and after the application of the various filters via calculation of peak signal-To-noise ratio, root mean square error (RMSE), structural similarity index measure, and relative CT-value bias, separately for the lung tissue and whole body. Results: The quantitative evaluation indicated that 10%-dose CT images have inferior quality (with RMSE = 322.1 ± 104.0 HU and bias = 11.44% ± 4.49% in the lung) even after the application of the denoising filters. The bilateral filter exhibited superior performance to suppress the noise and recover the underlying signals in low-dose CT images compared to the other denoising techniques. The bilateral filter led to RMSE and bias of 100.21 ± 16.47 HU and-0.21% ± 1.20%, respectively, in the lung regions for 20%-dose CT images compared to the Gaussian filter with RMSE = 103.46 ± 15.70 HU and bias = 1.02% ± 1.68% and median filter with RMSE = 129.60 ± 18.09 HU and bias =-6.15% ± 2.24%. Conclusions: The 20%-dose CT imaging followed by the bilateral filtering introduced a reasonable compromise between image quality and patient dose reduction. © 2023 Isfahan University of Medical Sciences(IUMS). All rights reserved.
Journal Of Medical Signals And Sensors (22287477) 12(2)pp. 171-175
The purpose of this study is to assess a rare case of fetal radiation absorbed dose here through 18 F-Fludeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) in early pregnancy (5-week-old fetus). The fetal absorbed dose due to the radiation emitted from the mother's body, the fetus self-dose, and the dose received from CT were computed. The 35-year-old patient, weighing 85 kg, was injected with 370 MBq of 18 F-FDG. Imaging started at 1 h with CT acquisition followed by PET imaging. The photon and positron self-dose was calculated by applying the Monte Carlo (MC) GATE (GEANT 4 Application for Tomographic Emission) code. The volume of absorbed dose from the mother's body organs and the absorbed dose from the CT were added to the self-dose to obtain the final dose. The volume of self-dose obtained through MC simulation for the fetus was 3.3 × 10-2 mGy/MBq, of which 2.97 × 10-2 mGy/MBq was associated with positrons and 0.33 × 10-2 mGy/MBq was associated with photons. Biologically, the absorbed dose from CT, 7.3 mGy, had to be added to the total dose. The absorbed dose by the fetus during early pregnancy was higher than the standard value of 2.2 × 10-2 mGy/MBq (MIRD DER) because, during the examinations, the mother's bladder was full. This issue was a concern during updating standards. © 2022 Isfahan University of Medical Sciences(IUMS). All rights reserved.
Iranian Journal of Physics Research (16826957) 21(4)pp. 821-832
Proton therapy is one of the best methods of treatment for liver cancer. In this research, the main parts of proton therapy system, with passive scattering nozzle, including range-modulating wheel, energy-compensated contoured scatterer and collimators were simulated. Then the proton absorbed dose in healthy and tumoral tissues was calculated by simulating the proton therapy of liver tumors. Furthermore the secondary neutron dose, that increases the risk of secondary cancers, was calculated. For this purpose, the neutron equivalent absorbed dose in tumor and healthy tissues were calculated. Furthermore, the MIRD phantom was located in front of the output of the proton therapy system. By simulating the proton therapy for tumor in depth of 11 cm in the liver with mean source energy of 200 MeV, the absorbed dose of proton in tumor estimated as 3.32 × 10-12 Gy/particle that is 7.26 times more than proton dose in healthy parts of liver. This ratio showed that tumor absorbs the maximum dose, while the healthy tissue absorbs the minimum dose. In the next step, the same procedure was done with mean source energy of 180 MeV for tumor in depth of 6 Cm. According to the results, the proton absorbed dose in tumor was 1.94 × 10-12 Gy/particle that is 9 times more than proton absorbed dose in healthy tissue. Also the maximum neutron equivalent absorbed dose in healthy tissue is of the order of 10-14 Sv that can be ignorable in comparison with proton treatment effects of proton therapy. © 2022, Isfahan University of Technology. All rights reserved.
Given the potential performance of deep learning-based systems, there are various approaches for medical image analysis, particularly attention-based semantic segmentation models. Attention-based techniques will facilitate more accurate predictions in medical image segmentation by concentrating on the correct region. The purpose of this study is to analyze multiple attention-based deep learning methods for semantic segmentation tasks in the medical imaging field. Since the attention mechanism was introduced, independent of its structure, it has been progressively applied to enhance the performance of deep learning systems in a variety of medical image processing applications. In addition, different deep learning networks for liver and tumor segmentation have been proposed utilizing an attention mechanism. Three deep learning models for liver and tumor segmentation were evaluated in this study to provide a baseline for comparing the performance of the various models. A total of 131 computed tomography (CT) volumes were included in this investigation (104 subjects for training and 27 subjects for validation). The segmented images with varying degrees of tumor contrast were evaluated using a variety of different evaluation metrics. The performance of implemented models was evaluated on LiTS 2017 Challenge dataset. Compared to two other implemented models, the attention-based U-Net with 2.32 million parameters was more accurate. The liver and tumor segmentation dice coefficients in the best model were 0.934 and 0.778, respectively. Experimental results on the LiTS datasets showed that the attention mechanism is potentially capable of producing improved performance. © 2022 IEEE.
Skeletal bone age assessment is a conventional clinical method used to determine adolescent maturity in orthodontics, kinematics, pediatrics, forensic science, and other professions. Bone age is typically determined using the Greulich and Pyle (GP) or Tanner Whitehouse (TW2 or TW3) procedures from radio-graphs of the hand. Because GP and TW methods are subjective and rely on the practitioner's skill, they demand long analysis time, as well as experienced staff. This indicates the necessity for a fully automated approach to determine bone age. In this study, we proposed a robust model to jointly detect wrist area and estimate the bone age from radiograph data. To this end, we initially examined several state-of-the-art Convolution Neural Networks (CNN) models to specify bone age. Then, we proposed the hybrid model, involving two stages. In the first stage, the object detection module selects the key regions of input image to aid the bone age estimation. In the second stage, an attention mechanism based on Residual Neural Networks (ResNet) was included to increase the accuracy of bone age estimation within the classification phase. The mean absolute error for the hybrid model was 0.75 years compared to 1.03, 1.23, 1.08 years obtained from Resnet 18, Resnet 50, and Mobilenet, respectively. The proposed model for joint detection of wrist area and estimation of bone age exhibited superior performance over the conventional networks. This model could be used a decision support tool to reduce the workload/processing time in clinical practice. © 2022 IEEE.
Journal Of Medical Signals And Sensors (22287477) 11(1)pp. 24-30
Background: Bone age assessment (BAA) is a radiological process with the aim of identifying growth disorders in children. The objective of this study is to assess the bone age of Iranian children in an automatic manner. Methods: In this context, three computer vision techniques including histogram of oriented gradients (HOG), local binary pattern (LBP), and scale-invariant feature transform (SIFT) are applied to extract appropriate features from the carpal and epiphyseal regions of interest. Two different datasets are applied here: The University of Southern California hand atlas for training this computer-Aided diagnosis (CAD) system and Iranian radiographs for evaluating the performance of this system for BAA of Iranian children. In this study, the concatenation of HOG, LBP, and dense SIFT feature vectors and background subtraction are applied to improve the performance of this approach. Support vector machine (SVM) and K-nearest neighbor are used here for classification and the better results yielded by SVM. Results: The accuracy of female radiographs is 90% and of male is 71.42%. The mean absolute error is 0.16 and 0.42 years for female and male test radiographs, respectively. Cohen's kappa coefficients are 0.86 and 0.6, P < 0.05, for female and male radiographs, respectively. The results indicate that this proposed approach is in substantial agreement with the bone age reported by the experienced radiologist. Conclusion: This approach is easy to implement and reliable, thus qualified for CAD and automatic BAA of Iranian children. © 2021 Isfahan University of Medical Sciences(IUMS). All rights reserved.
Physica Medica (11201797) 90pp. 99-107
Purpose: Among the different available methods for synthetic CT generation from MR images for the task of MR-guided radiation planning, the deep learning algorithms have and do outperform their conventional counterparts. In this study, we investigated the performance of some most popular deep learning architectures including eCNN, U-Net, GAN, V-Net, and Res-Net for the task of sCT generation. As a baseline, an atlas-based method is implemented to which the results of the deep learning-based model are compared. Methods: A dataset consisting of 20 co-registered MR-CT pairs of the male pelvis is applied to assess the different sCT production methods' performance. The mean error (ME), mean absolute error (MAE), Pearson correlation coefficient (PCC), structural similarity index (SSIM), and peak signal-to-noise ratio (PSNR) metrics were computed between the estimated sCT and the ground truth (reference) CT images. Results: The visual inspection revealed that the sCTs produced by eCNN, V-Net, and ResNet, unlike the other methods, were less noisy and greatly resemble the ground truth CT image. In the whole pelvis region, the eCNN yielded the lowest MAE (26.03 ± 8.85 HU) and ME (0.82 ± 7.06 HU), and the highest PCC metrics were yielded by the eCNN (0.93 ± 0.05) and ResNet (0.91 ± 0.02) methods. The ResNet model had the highest PSNR of 29.38 ± 1.75 among all models. In terms of the Dice similarity coefficient, the eCNN method revealed superior performance in major tissue identification (air, bone, and soft tissue). Conclusions: All in all, the eCNN and ResNet deep learning methods revealed acceptable performance with clinically tolerable quantification errors. © 2021 Associazione Italiana di Fisica Medica
Accurate segmentation of the hippocampus head and body from MR images is routinely performed to examine the link between the hippocampus deformation and neurological diseases, such as Alzheimer's and epilepsy. State-of-the-art seminal segmentation methods (including hippocampus segmentation) are based on deep learning algorithms. Most studies focused on developing robust deep learning algorithms to achieve satisfactory performance in hippocampus body and head segmentation. A critical aspect that has been overlooked in these studies is the strategy adopted to train deep learning algorithms when there are two or more target structures. In this work, we examine which deep learning training strategies would be more effective. These strategies include simultaneous (parallel segmentation of the head and body), serial (first head and then body), independent, and attention-based training and segmentation of the target structures. To this end, the hippocampus dataset from the Decathlon challenge and a residual neural network (Resnet) were employed to compare the above-mentioned strategies for hippocampus head and body segmentation. The Dice similarity coefficient and Hausdorff distance were calculated for the outcome of each strategy versus the manually defined hippocampus head and body masks. The quantitative analysis of the outcomes of different training frameworks demonstrated the superior performance of the attention-based training framework with Dice index of 0.89±0.03 (body) and 0.88±0.04 (head) compared to simultaneous, serial, and independent training frameworks with Dice indices of 0.88±0.04 (body) and 0.87±0.04 (head), 0.88±0.04 (body) and 0.87±0.04 (head), and 0.88±0.04 (body) and 0.86±0.04 (head), respectively. The statistical analysis demonstrated the significantly superior performance of the attention-based training framework (p-value<0.0001). In conclusion, the attention-based training framework is recommended for multi-structure seminal segmentation. © 2021 IEEE.
Measurement: Journal of the International Measurement Confederation (02632241) 171
In this study, the impact of anatomical changes on radiation dose variations of the prostate and bladder (as an organ at risk) was assessed for a potential scenario of magnetic resonance imaging-guided carbon-ion radiotherapy (MRgCT) of prostate cancer. To achieve this goal, carbon-ion beams perpendicular to a pelvis phantom affected by 1.5 T perpendicular magnetic field were simulated using the FLUKA code. Prostate diameter change from 6 to 1 cm leads to a prostate dose reduction of 88%. Bladder diameter change from 10 to 5 cm leads to a reduction of 92% in bladder dose. The set-up error of 5 mm leads to a decrease of 5% in the prostate dose. Rectum diameter change from 5 to 3 cm leads to reductions of 20% and 26% in prostate and bladder dose, respectively. In conclusion, anatomical changes impact on dose variations in MRgCT of prostate cancer. © 2020 Elsevier Ltd
Medical Physics (24734209) 47(10)pp. 5158-5171
Purpose: Despite the proven utility of multiparametric magnetic resonance imaging (MRI) in radiation therapy, MRI-guided radiation treatment planning is limited by the fact that MRI does not directly provide the electron density map required for absorbed dose calculation. In this work, a new deep convolutional neural network model with efficient learning capability, suitable for applications where the number of training subjects is limited, is proposed to generate accurate synthetic computed tomography (sCT) images from MRI. Methods: This efficient convolutional neural network (eCNN) is built upon a combination of the SegNet architecture (a 13-layer encoder-decoder structure similar to the U-Net network) without softmax layers and the residual network. Moreover, maxpooling indices and high resolution features from the encoding network were incorporated into the corresponding decoding layers. A dataset containing 15 co-registered MRI-CT pairs of male pelvis (1861 two-dimensional images) were used for training and evaluation of MRI to CT synthesis process using a fivefold cross-validation scheme. The performance of the eCNN model was compared to an atlas-based sCT generation technique as well as the original U-Net model considering CT images as reference. The mean error (ME), mean absolute error (MAE), Pearson correlation coefficient (PCC), structural similarity index (SSIM), and peak signal-to-noise ratio (PSNR) metrics were calculated between sCT and ground truth CT images. Results: The eCNN model exhibited effective learning capability using only 12 training subjects. The model achieved a ME and MAE of 2.8 ± 10.3 and 30.0 ± 10.4 HU, respectively, which is substantially lower than values achieved by the atlas-based (−0.8 ± 35.4 and 64.6 ± 21.2) and U-Net (7.4 ± 11.9 and 44.0 ± 8.8) methods, respectively. Conclusion: The proposed eCNN model exhibited efficient convergence rate with a low number of training subjects, while providing accurate synthetic CT images. The eCNN model outperformed the original U-Net model and showed superior performance to the atlas-based technique. © 2020 American Association of Physicists in Medicine
Journal of Digital Imaging (1618727X) 33(2)pp. 399-407
Bone age assessment (BAA) is a radiological process to identify the growth disorders in children. Although this is a frequent task for radiologists, it is cumbersome. The objective of this study is to assess the bone age of children from newborn to 18 years old in an automatic manner through computer vision methods including histogram of oriented gradients (HOG), local binary pattern (LBP), and scale invariant feature transform (SIFT). Here, 442 left-hand radiographs are applied from the University of Southern California (USC) hand atlas. In this experiment, for the first time, HOG–LBP–dense SIFT features with background subtraction are applied to assess the bone age of the subject group. For this purpose, features are extracted from the carpal and epiphyseal regions of interest (ROIs). The SVM and 5-fold cross-validation are used for classification. The accuracy of female radiographs is 73.88% and of the male is 68.63%. The mean absolute error is 0.5 years for both genders’ radiographs. The accuracy a within 1-year range is 95.32% for female and 96.51% for male radiographs. The accuracy within a 2-year range is 100% and 99.41% for female and male radiographs, respectively. The Cohen’s kappa statistical test reveals that this proposed approach, Cohen’s kappa coefficients are 0.71 for female and 0.66 for male radiographs, p value < 0.05, is in substantial agreement with the bone age assessed by experienced radiologists within the USC dataset. This approach is robust and easy to implement, thus, qualified for computer-aided diagnosis (CAD). The reduced processing time and number of ROIs facilitate BAA. © 2019, Society for Imaging Informatics in Medicine.
Iranian Journal of Physics Research (16826957) 20(4)pp. 599-613
Brachytherapy is a kind of cancer treatment in which radiation sources are implanted inside or close to the cancerous tissue. The purpose of this research is to calculate the absorbed dose uncertainty of prostate tissue, due to its swelling, displacement of the implanted seed sources and also, to address the effect of these factors simultaneously, in brachytherapy of prostate. In this research, MCNPX2.6 code, the TG-43U1 protocol and ORNL body phantom were used to simulate the brachytherapy of prostate using iodine-125 seed sources. In the first study, 84 sources of iodine with the shapes of seed and then points were implanted inside the prostate with the volume of 38.01 cm3. The radiation absorbed dose was found to be 110.59 and 110.57 Gy, respectively. Considering the 50% prostate inflation after implantation, the radiation absorbed doses of prostate showed a reduction of more than of 17%. In the second therapeutic plan, by using 76 seed sources of I-125, considering 12% swelling of prostate and applying the displacement of seed sources in three directions: left–right (1.8mm), front-back (2.1mm) and top–down (3.4mm)), the radiation dose amount of the cancerous tissue was reduced about 21%. So, the results of seed and point sources of brachytherapy were very close to each other. Therefore, in simulation studies, point sources can be used instead of seed sources to reduce the computational complexity. Also, this research showed the effects of swelling and displacement of brachytherapy sources on the amount of the absorbed dose of prostate and its treatment were noteworthy. © 2020, Isfahan University of Technology. All rights reserved.
Journal of Instrumentation (17480221) 15(5)
The correct estimation of water equivalent ratio (WER) and the associated errors is highly important for the delivery of carbon-ion (C-ion) beams. In the case of MRI-guided C-ion radiotherapy (MRgCT) scenario, as a therapeutic approach for future potential MR-guided particle therapy, C-ion beam will be deflected in the presence of the magnetic field. The curvature of the track causes a retraction of the range. This range variation might be different in various materials, which leads to change the WER values. To evaluate the WER variations versus magnetic field strength, in this research work, WER of some materials, including bladder, brain, prostate, muscle, bone, polymethylmethacrylate (PMMA), polyoxymethylene (POM), polyethyleneterephthalate (PET), titanium (Ti), gold (Au), platinum (Pt); potentially encountered in C-ion radiotherapy dosimetry were assessed. A mono-energetic C-ion beam, incident on a volume containing materials as mentioned above, was simulated using the FLUKA Monte Carlo code. To validate the simulated C-ion beams, the ion ranges in the water at the calculated energies (100-400 MeV/n) were compared with experimental and analytical data reported in the literature. Moreover, the calculated WER results were compared with available experimental data in the absence of the magnetic field. The WER values were calculated for the materials mentioned above in the presence of 0.35, 1.5, and 3 T magnetic fields and compared to the case without a magnetic field. Good agreement with the experimental data regarding range prediction in water was achieved. No change in the WER value was observed at 100 MeV/n and 0.35 T for all the studied materials and energies. In the case of bladder, brain, and prostate, and muscle materials, no change in WER values was observed by changing the magnetic field strength up to 3 T at the range of the studied energies. The maximum change in WER values by applying the magnetic fields is relevant to the Ti material (-0.4%), which occurs at 400 MeV/n energy and 3 T magnetic field. Considering the potential encounter of the studied materials in the clinical practice of MRgCT, in the form of phantoms, dosimeters, detectors, fiducial markers, radio-opaque clips, patient anatomies, etc., the results of this study highly contribute to assess the variation of WER values of the studied dosimetric materials and the changes in C-ion ranges within these materials when the transverse magnetic fields are applied to the materials subject to study. © 2020 IOP Publishing Ltd and Sissa Medialab.
Cancer Research (00085472) 80(4)pp. 868-876
Preclinical studies, in vivo, and in vitro studies, in combination with mathematical modeling can help optimize and guide the design of clinical trials. The design and optimization of alpha-particle emitter radiopharmaceutical therapy (αRPT) is especially important as αRPT has the potential for high efficacy but also high toxicity.Wehave developed a mathematical model that may be used to identify trial design parameters that will have the greatest impact on outcome. The model combines Gompertzian tumor growth with antibody-mediated pharmacokinetics and radiation-induced cell killing. It was validated using preclinical experimental data of antibody-mediated 213Bi and 225Ac delivery in a metastatic transgenic breast cancer model. In modeling simulations, tumor cell doubling time, administered antibody, antibody specific-activity, and antigen-site density most impacted median survival. The model was also used to investigate treatment fractionation. Depending upon the time-interval between injections, increasing the number of injections increased survival time. For example, two administrations of 200 nCi, 225Ac-labeled antibody, separated by 30 days, resulted in a simulated 31% increase in median survival over a single 400 nCi administration. If the time interval was 7 days or less, however, there was no improvement in survival; a one-day interval between injections led to a 10% reduction in median survival. Further model development and validation including the incorporation of normal tissue toxicity is necessary to properly balance efficacy with toxicity. The current model is, however, useful in helping understand preclinical results and in guiding preclinical and clinical trial design towards approaches that have the greatest likelihood of success. Significance: Modeling is used to optimize αRPT. © 2019 American Association for Cancer Research.
Synthetic CT (sCT) generation from MR images is yet one of the major challenges in the context of MR-guided radiation planning as well as quantitative PET/MR imaging. Deep convolutional neural networks have recently gained special interest in large range of medical imaging applications including segmentation and image synthesis. In this study, a novel deep convolutional neural network (DCNN) model is presented for synthetic CT generation from single T1-weighted MR image. The proposed method has the merit of highly accelerated convergence rate suitable for applications where the number of training da-taset is limited while highly robust model is required. This algorithm exploits a Visual Geometry Group (VGG16) model without fully connected layer coupled to a residual network in the form of encoder-decoder structure. The training of the proposed algorithm was performed using pelvis image of only 15 patients in a five-fold cross-validation scheme. No network pre-training and data augmentation was used. The outcome of the proposed algorithm was compared to an atlas-based approach in terms of accuracy of CT intensity estimation within different body tissues. After only 100 epochs, the proposed algorithm resulted in mean absolute error (MAE) and mean error (ME) of 40.64 ± 12.66 and-2.80 ± 10.98 (HU) for the entire pelvis region, respectively. While atlas-based method led to MAE of 82.06 ± 52.59 and ME of-13.00 ± 60.19 (HU). Within the soft-tissue the atlas-based method and the proposed algorithm achieved MAEs of 51.01±14.3 and 25.51±7.72 (HU), respectively. Likewise in bony tissue, MAEs of 212.65±78.45 and 221.99±76.28 (HU) were obtained when using DCNN and atlas-based methods, respectively. The proposed algorithm showed superior performance to the atlas-based method with only relying on a limited number of training subjects. The proposed algorithm is suitable for the clinical applications where accurate models are required while accessing a large number of training cases is limited. © 2019 IEEE.
International Journal Of Radiation Research (23223243) 17(4)pp. 651-657
Background: Clinical application of PET imaging for diagnosis, staging, re-staging treatment planning and treatment response assessment have become a major focus of studies in the past decades. Fetus is more sensitive to ionizing radiation, consequently, radiation absorption risks need to be assessed carefully. The objective of this article is to accurately estimate the absorbed dose during pregnancy in PET examinations. The method adopted in this article is simulative-analytic. Materials and Methods: The absorbed dose from administrating 18F-FDG during pregnancy is estimated through the BodyBuilder anthropomorphic mathematical phantom (inexpensive) together with Monte Carlo simulations in order to obtain a reliable and feasible methodology. In this simulation, the Specific Absorbed Fractions (SAF) is estimated for organs of 3, 6 and 9-months fetal. Results: The obtained results indicate that the absorbed dose of 18F-FDG PET imaging the fetal is 2.50×10-2 mGy/MBq early; 2.04×10-2 mGy/MBq first three months of pregnancy, 1.80 ×10-2 mGy/MBq second three months, and 1.50 ×10-2 mGy/MBq in the third three months of pregnancy. Maternal absorbed dose estimation here is (R2=0.965) which perfectly corresponds to ICRP publication. Conclusion: The results from Monte Carlo code with BodyBuilder anthropomorphic phantoms and ICRP recommendation are of acceptable correlation. Applying the pure BodyBuilder anthropomorphic phantoms in this simulation, which yields agreeable results in addition to its low time consumption, corresponds to the available finding by other researchers while reducing calculation times. Moreover, the fetal & maternal absorbed doses remain however well below the threshold for any deterministic effects. © 2019 Novin Medical Radiation Institute. All rights reserved.
Physica Medica (11201797) 64pp. 323-323
The authors regret there was an error in the formula of Eq. (3) in the above-mentioned published article. The corrected formula is now shown below. [Formula presented] The authors would like to apologise for any inconvenience caused due to the typesetting. © 2019 Associazione Italiana di Fisica Medica
Medical Physics (24734209) 46(11)pp. 5273-5283
Purpose: To evaluate the effect of beam configuration with inaccurate or incomplete small field output factors on the accuracy of dose calculations in treatment planning systems. Methods: Output factors were measured using various detectors and for a range of field sizes. Three types of treatment machines were configured in two treatment planning systems. In the first (corrected) machine, the Exradin W1 scintillator was used to determine output factors. In the second (uncorrected) machine, the measured output factors by the A1SL ion chamber without considering output correction factors for small field sizes were utilized. In the third (clinical) machine, measured output factors by the Exradin W1 were used but not for field sizes smaller than 2 × 2 cm2. The dose computed by the anisotropic analytical algorithm (AAA), Acuros XB (AXB) and collapsed cone convolution/superposition (CCC) algorithms in the three machines were delivered using static (jaw-, MLC-, and jaw/MLC-defined), and composite [intensity modulated radiation therapy (IMRT), volumetric modulated arc therapy (VMAT)] fields. The differences between measured and calculated dose values were analyzed. Results: For static fields, the percentage differences between measured and calculated doses by the three algorithms in three configured machines were <2% for field sizes larger than 2 × 2 cm2. In jaw- and jaw/MLC-defined fields smaller than 2 × 2 cm2, the corrected machine presented better agreement with measurement. Considering output correction factors in MLC-defined fields, among the three configured machines, the accuracy of calculation improved to within ±0.5%. For MLC-defined field size of 1 × 1 cm2, AXB showed the smallest percentage difference (1%). In IMRT and VMAT plans, the percentage differences between measured and calculated doses at the isocenter, as well as the gamma analysis of different plans, which include field sizes larger than 3 × 3 cm2, did not vary noticeably. For smaller field sizes, using the corrected machine influences dose calculation accuracy. Conclusion: Configuration with corrected output factors improves accuracy of dose calculation for static field sizes smaller than 2 × 2 cm2. For very small fields, the robustness of the dose calculation algorithm affects the accuracy of dose as well. In IMRT and VMAT plans, which include small subfields, the size of the jaw-defined field is an important factor and using corrected output factors increases dose calculation accuracy. © 2019 American Association of Physicists in Medicine
Physica Medica (11201797) 61pp. 33-43
Purpose: To evaluate beam deflection and dose equivalent perturbation of carbon-ion (C-ion) versus depth in a perpendicular magnetic field with the motivation of application to potential future development of MRI-guided carbon therapy. Methods: A therapeutic beamline, a rectangular water phantom (homogeneous) and a multi-layer tissue phantom were simulated by applying the FLUKA Monte Carlo simulation code. The C-ion beam deflection variation against depth inside the water phantom at 100, 220 and 310 MeV/nucleon (MeV/n) was calculated in the presence of 0.5, 1.5 and 3 T magnetic fields. The 220 MeV/n primary ion depth dose equivalent variations induced by a 1.5 T field were calculated inside the homogeneous and multi-layer phantoms. Results: The calculated deflections were ranging from 0 to 10.5 mm. The Bragg depth did not change by applying a 1.5 T field to both phantoms under study at 220 MeV/n energy. The dose equivalent in the Bragg depth inside the homogeneous and multi-layer tissue phantoms was found to be reduced by 5.1% and 2.95%, respectively. A dose equivalent reduction of 5.77% in the Bragg depth was obtained when an air layer of 1.8 cm thick was added to the multi-layer phantom. Conclusion: Dose equivalent perturbation and beam deflection become important at energies above 100 MeV/n, in both phantoms affected by a 1.5 T magnetic field. © 2019 Associazione Italiana di Fisica Medica
Iranian Journal of Medical Physics (17357241) 15(3)pp. 169-175
Introduction: Crosstalk is a leakage of X-ray or light produced in a matrix of X-ray detectors or array of photodiodes in one element to other elements affecting on image contrast and spatial resolution. In this study, we assessed X-ray crosstalk in a computed tomography (CT) scanner with small detector elements to estimate the effect of various parameters such as X-ray tube voltage, detector element sizes, scintillator material, impurities in the scintillator material, and the material of detector separators on X-ray crosstalk. Materials and Methods: This study was performed using Monte Carlo simulation. In the first step, X-ray tube and its energy spectrum at the energies of 80, 100, 120, and 140 keV were simulated and validated by using SpekCalc and t-test. Then, other important parts of CT scanner, namely filters, detectors, and grids were simulated. X-ray crosstalk between CT detectors was calculated in air and in the presence of water phantom (as a simulator of human body) to compare the effect of scattered photons. Finally, the influence of some important parameters on X-ray crosstalk was evaluated. Results: In CT scanner with small elements, when using phantom, crosstalk increases by 16-50%. Using the lowest possible energies of X-ray, decreases the crosstalk up to 43% of its initial amount. Furthermore coating a 10 or 20 μm layer of tungsten or lead on the detector separators, decreases the X-ray crosstalk significantly. Conclusion: Choosing the proper high voltage, detectors' material and its dimensions, scintillator impurities and septa material can decrease X-ray crosstalk. © 2018, Mashhad University of Medical Sciences.
Medical Physics (24734209) 45(5)pp. 2329-2336
Purpose: To evaluate dependence of measured dose on size and location of region of interest (ROI) in Gafchromic EBT3 film dosimetry. Methods: Gafchromic EBT3 films were irradiated perpendicularly using the 6MV beam from a linear accelerator at 10 cm depth (100 cm SSD) of a 30 × 30 × 20 cm3 solid water phantom for a range of field sizes of 6 × 6 to 100 × 100 mm2. ImageJ software was used for reading pieces of film. The appropriate location of ROIs in scanned films was found by two methods. First, the ROI was visually placed at the center of image. Second, the profile of pixel value versus distance was plotted and the center of profile was used for drawing ROI. Each scanned film was read using both methods and for three ROI sizes (1, 2, and 4 mm). A plastic scintillator, Exradin W1, was used as the reference dosimeter. Results: Comparing the three ROI sizes using both methods showed that there was less than 2% difference from reference in output factor measurements for field sizes larger or equal to 10 × 10 mm2. The percentage differences were increased in field sizes smaller than 10 × 10 mm2 and for ROI size of 4 × 4 mm2 for both centered-ROI and profiled-ROI methods. The mean percentage differences from reference measurements, for field sizes of 100 × 100 to 20 × 20 mm2, were smaller than 1% in both methods of ROI positioning. For field sizes of 15 × 15 and 10 × 10 mm2, the smaller mean percentage differences were observed in profiled-ROI (4 × 4 mm2) and centered-ROI (4 × 4 mm2). For the field sizes of 8 × 8 and 6 × 6 mm2, the profiled-ROI (2 × 2 mm2) had smallest mean percentage difference, which was 0.88%. Conclusion: The ROI size of 4 × 4 mm2 is appropriate for dose measurements in field sizes of 100 × 100 mm2 to 10 × 10 mm2, regardless of the method of finding location of ROI. In field sizes smaller than 10 × 10 mm2, finding location of the ROI by profile of pixel values increases the accuracy of measurement, and ROI size of 2 × 2 mm2 has the smallest difference from the reference dose measurements. © 2018 American Association of Physicists in Medicine
International Journal Of Radiation Research (23223243) 15(4)pp. 383-390
Background: In CT systems, the machine utilizes a bowtie filter to shape the X -ray beam and remove lower energy photons. The shape of this bowtie filter is complicated and its geometry is o!en not available in detail. These renders the CT dose index (CTDI) to have different values in measurement versus Monte Carlo simulation studies and other analytical calculations especially in dosimetry of internal organs. In existing literature, the bowtie filter shape is extracted by using expensive sensors Materials and Methods: In the present work, the shape of the bowtie filter of the Biograph 6 PET/CT was derived by using Thermolumenecence dosimeters (TLDs). Subsequently, to evaluate the accuracy of the body bowtie filter shape as generated by TLDs, Monte Carlo simulation of CT was performed. 16 X-ray sources in various angles were used within the Monte Carlo code (MCNP-4C) to simulate the CT section of the PET -CT Biograph 6 system and to calculate dose. Results: The relative difference between simulated and measured CTDI value for the PET/CT Siemens Biograph 6 at 80, 110 and 130 kVp were 4.2, 2.9 and 2.3%, respectively. Conclusion: In this study, we demonstrate that it is possible to calculate the bowtie filter shape by using an inexpensive TLD method. The results showed that it is possible to determine the shape of the bowtie filter in PET/CT using TLDs with acceptable accuracy.
Image segmentation of medical images is a challenging problem with several still not totally solved issues, such as noise interference and image artifacts. Region-based and histogram-based segmentation methods have been widely used in image segmentation. Problems arise when we use these methods, such as the selection of a suitable threshold value for the histogram-based method and the over-segmentation followed by the time-consuming merge processing in the region-based algorithm. To provide an efficient approach that not only produce better results, but also maintain low computational complexity, a new region dividing based technique is developed for image segmentation, which combines the advantages of both regions-based and histogram-based methods. The proposed method is applied to the challenging applications: Gray matter (GM), White matter (WM) and cerebrospinal fluid (CSF) segmentation in brain MR Images. The method is evaluated on both simulated and real data, and compared with other segmentation techniques. The obtained results have demonstrated its improved performance and robustness. © 2016 Yazdani et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Tehran University Medical Journal (17357322) 74(8)pp. 597-600
Background: Cooling is one of the main processes in bone temperature decrement, while drilling. this experiment was conducted for examination of alcohol effect as cooler in prevention of thermal necrosis. Methods: Bovine femur bone was considered as specimen and inclusions criteria for this study were: femur bone, cortical area and without bone periosteum. Drilling process was conducted by two types of k-wire-Trocar and Diamond, three speeds and three feed rates and in the time of march, 2016 in the place of university of Isfahan, Iran. Two type of thermometer-K-thermocouple and infrared thermometer- were used for temperature measurement, and all data were logged by data logger. Drilling processes were conducted by milling machine with ability of table movement for feed rate parameter. Method of alcohol usage in cooling was in form of conducting alcoholic gauze with k-wire while rotating. Results: Totally in the cases of trocar and diamond wires, while were cooled by alcohol, the risk of bone necrosis decreased about 44.44% and 66.66%. All temperature data were logged by changing parameters. maximum temperature, 94.5 °C, belonged to trocar wire in a non-cooling condition and after usage of cooler it decreased to 75 °C. In the usage of diamond wires, the maximum temperature was recorded 71 °C and the temperature while using alcohol was 51 °C. Diamond wire had better result in both conditions of cooling and no cooling, and this is related to geometric differences between two types of wires. Conclusion: Due to obtained data from examination, utilization alcohol can have an important influence on final bone temperature decreasing. The way of using alcohol was in the style of attrition soaked gauze onto wire while insertion. © 2016, Tehran University of Medical Sciences. All rights reserved.
White blood cells protect the immune system against viruses and bacteria. Data extraction from white blood cells may cause problems such as loosing form, dimensions and edges. In this study, a complete and automatic method to identify and classify white blood cells using microscopic images has been presented. In the proposed method, in the first step, white blood cells are identified using color space conversion models. Then leukocytes group are separated using division of watershed conversion. In the next step image cleanup is done and all leukocytes available on the edge of images and abnormal components are removed. This is accomplished by cutting the image with the smallest rectangle that has connected components. The second level of division relates to the detection of the nucleus and cytoplasm. In the last step feature extraction is performed which causes the pathologists can have the best interpretation of them. All the above steps have been performed in MATLAB software. At the end, the proposed method was examined by a database belonging to Imam Reza (AS) hospital in Mashhad, consisting of 29 images of blood cells, and showed the accuracy of 93% in the detection of white blood cells. © 2016 IEEE.
Shokouhian, S.B. ,
Karimian, A.R. ,
Mohammad-zadeh, M. ,
Salighe-rad, H.R. Iranian Journal Of Medical Physics (23453672) 13(3)pp. 193-202
Introduction Radiofrequency planar microcoils are used to increase the resolution of magnetic resonance images of small samples. In this study, we aimed to design and fabricate a spiral planar microcoil constructed on a double-sided printed circuit board (PCB). It has four rings with an internal diameter of 241 microns tuned and matched at 63.8 MHz. Materials and Methods To achieve the maximum signal-to- noise ratio (SNR) and quality factor of the coil, its geometry was optimized based on parameters such as width (w) and thickness (h) of the copper rings, the distance between the rings, inner radius of the microcoil (Ri), and the number (N) of coil rings by using COMSOL, ADS, and MATLAB software packages. Results Our findings indicated that the Q factor and SNR of the coil at resonance frequency of 63.8 MHz are 63.149 and 168.23, respectively, which are higher than the equivalent features of the pervious coils. In addition, to evaluate the function of matching and tuning circuit, reflection coefficient factor (S11) of the coil was experimentally measured to be -48 dB at resonance frequency of 63.8 MHz, which is consistent with the simulated value. Conclusion In this study, a new microcoil was designed and fabricated to produce images of very small samples and volumes in microliter dimensions. The results showed that this new microcoil has superior capability in imaging very small samples compared to the conventional coils applied in magnetic resonance imaging devices.
We proposed an automatic hybrid image segmentation model that integrates the modified statistical expectation maximization (EM) method and the spatial information combined with Support Vector Machines (SVM). To improve the overall segmentation performance different types of information are integrated in this study, which are, voxel location, textural features, MR intensity and relationship with neighboring voxels. The modified EM method is used for intensity based classification as an initial segmentation stage. Secondly simple and beneficial features are extracted from target area of segmented image using gray-level co-occurrence matrix (GLCM) technique. Subsequently, we applied Support Vector Machine (SVM) to rank computed features from the extracted features, which is an enhancement step. To evaluate the performance of the proposed method, experiments carried out on real MRI. The results of proposed method are evaluated against manual segmentation results on real scans. The K-index is calculated to evaluate the performance of the proposed model relative to the expert segmentations. The results demonstrate that the proposed technique has satisfactory results. © 2015 IEEE.
Journal Of Medical Signals And Sensors (22287477) 5(4)pp. 238-244
Automatic segmentation of multiple sclerosis (MS) lesions in brain magnetic resonance imaging (MRI) has been widely investigated in the recent years with the goal of helping MS diagnosis and patient follow-up. In this research work, Gaussian mixture model (GMM) has been used to segment the MS lesions in MRIs, including T1-weighted (T1-w), T2-w, and T2-fluid attenuation inversion recovery. Usually, GMM is optimized by using expectation-maximization (EM) algorithm. The drawbacks of this optimization method are, it does not converge to optimal maximum or minimum and furthermore, there are some voxels, which do not fit the GMM model and have to be rejected. So, GMM is time-consuming and not too much efficient. To overcome these limitations, in this research study, at the first step, GMM was applied to segment only T1-w images by using 100 various starting points when the maximum number of iterations was considered to be 50. Then segmentation results were used to calculate the parameters of the other two images. Furthermore, FAST-trimmed likelihood estimator algorithm was applied to determine which voxels should be rejected. The output result of the segmentation was classified in three classes; White and Gray matters, cerebrospinal fluid, and some rejected voxels which prone to be MS. In the next phase, MS lesions were detected by using some heuristic rules. This new method was applied on the brain MRIs of 25 patients from two hospitals. The automatic segmentation outputs were scored by two specialists and the results show that our method has the capability to segment the MS lesions with dice similarity coefficient score of 0.82. The results showed a better performance for the proposed approach, in comparison to those of previous works with less time-consuming. © 2015 Journal of Medical Signals & Sensors.
Computational and Mathematical Methods in Medicine (discontinued) (17486718) 2015
Brain MRI segmentation is an important issue for discovering the brain structure and diagnosis of subtle anatomical changes in different brain diseases. However, due to several artifacts brain tissue segmentation remains a challenging task. The aim of this paper is to improve the automatic segmentation of brain into gray matter, white matter, and cerebrospinal fluid in magnetic resonance images (MRI). We proposed an automatic hybrid image segmentation method that integrates the modified statistical expectation-maximization (EM) method and the spatial information combined with support vector machine (SVM). The combined method has more accurate results than what can be achieved with its individual techniques that is demonstrated through experiments on both real data and simulated images. Experiments are carried out on both synthetic and real MRI. The results of proposed technique are evaluated against manual segmentation results and other methods based on real T1-weighted scans from Internet Brain Segmentation Repository (IBSR) and simulated images from BrainWeb. The Kappa index is calculated to assess the performance of the proposed framework relative to the ground truth and expert segmentations. The results demonstrate that the proposed combined method has satisfactory results on both simulated MRI and real brain datasets. Copyright © 2015 S. Yazdani et al.
Jurnal Teknologi (21803722) 72(2)pp. 29-32
Automatic segmentation of brain images is a challenging problem due to the complex structure of brain images, as well as to the absence of anatomy models. Brain segmentation into white matter, gray matter, and cerebral spinal fluid, is an important stage for many problems, including the studies in 3-D visualizations for disease detection and surgical planning. In this paper we present a novel fully automated framework for tissue classification of brain in MR Images that is a combination of two techniques: GLCM and SVM, each of which has been customized for the problem of brain tissue segmentation such that the results are more robust than its individual components that is demonstrated through experiments. The proposed framework has been validated on brainweb dataset of different modalities, with desirable performance in the presence of noise and bias field. To evaluate the performance of the proposed method the Kappa similarity index is computed. Our method achieves higher kappa index (91.5) compared with other methods currently in use. As an application, our method has been used for segmentation of MR images with promising results. © 2015 Penerbit UTM Press. All rights reserved.
Breast cancer is one of the most prevalent cancers among women. Mammography, as one of the primary studies, is used for diagnosis of breast disease. In addition, MR images can depict most of the significant changes of breast during the time. For the first step of breast disease detection, the density measurement of the breast on MR images may provide very useful information. MR images have some instinctive limitations like the strongly dependence of contrast upon the way the image is acquired, noise, partial volumes, intensity inhomogeneities (bias field), etc. For these reasons, an effective normalization on breast MR images is very important issue for detecting breast disease signs. The first important step for quantitative analysis of breast density on MRI is preprocessing step including noise reduction and bias field correction. In this study, N3 algorithm is used for correcting the field inhomogeneity in MR images. We used T1-weighted images, using a 1.5-T MRI scanner. The results demonstrate effectiveness and efficiency of the proposed method. © 2015 Elsevier Inc. All rights reserved.
IETE Technical Review (Institution of Electronics and Telecommunication Engineers, India) (02564602) 32(6)pp. 413-427
Medical image segmentation plays an important role in medical-imaging applications and they provide a large amount of functional and anatomical information, which improve and facilitate diagnosis and disease therapy planning. However, the existence of image artifacts, such as intensity inhomogeneity, noise and partial volume in magnetic resonance images (MRIs), can adversely affect the quantitative image analysis. There are different segmentation methods in the literature, which segment brain MRI into white matter (WM), gray matter (GM) and cerebrospinal fluid (CSF). However, there is not a common algorithm that can be used for all types of images. We present a critical appraisal of the current status of techniques for MRI segmentation. In this paper, commonly used segmentation algorithms are reviewed and summarized with an emphasis on their characteristics, advantages and disadvantages of these techniques. These are categorized into five different groups based on their workflows and segmentation principles. Different solutions are also proposed to compensate the existing problems in each algorithm. This paper also addresses the issue of quantitative evaluation of segmentation results. © 2015 by the IETE.
Electromagnetic threats are considered to be among the latest threats to electrical devices. Therefore, it appears essential to identify such threats and their deployment scenarios in order to present electromagnetic shielding solutions and prevent disruption in the functioning of electrical devices. The aim of this paper was to introduce electromagnetic threats and propose solutions to shield electrical devices from such threats. Therefore, a sort of cavity was proposed to shield a computer unit from electromagnetic waves. Placing apertures on different sides of such cavities for air conditioning and cable accessories was inevitable. Thus, CST was employed to simulate such cavities with respect to the positions of apertures, their geometrical shapes, and their quantity. The simulations were performed in the 1-5 GHz frequency range. The SE value for a casing with circular apertures is initially calculated. Finally, the SE value is calculated for a case where gaps are added to the casing in order to understand the effect of gaps. The simulation results indicated that the proposed method could reduce the effect of waves in a completely successful way. © 2015 IEEE.
Radiation Protection Dosimetry (17423406) 162(1-2)pp. 120-124
Renal angiography is one of the medical imaging methods in which patient and physician receive high equivalent doses due to long duration of fluoroscopy. In this research, equivalent doses of some radiosensitive tissues of patient (adult and child) and physician during renal angiography have been calculated by using adult and child Oak Ridge National Laboratory phantoms and Monte Carlo method (MCNPX). The results showed, in angiography of right kidney in a child and adult patient, that gall bladder with the amounts of 2.32 and 0.35 mSv, respectively, has received the most equivalent dose. About the physician, left hand, left eye and thymus absorbed the most amounts of doses, means 0.020 mSv. In addition, equivalent doses of the physician's lens eye, thyroid and knees were 0.023, 0.007 and 7.9E24 mSv, respectively. Although these values are less than the reported thresholds by ICRP 103, it should be noted that these amounts are related to one examination. © The Author 2014.
Nuclear Technology and Radiation Protection (14513994) 29(4)pp. 289-295
Nowadays, dual energy X-ray absorptiometry is used in bone mineral density systems to assess the amount of osteoporosis. The purpose of this research is to evaluate patient organ doses from dual X-ray absorptiometry by thermoluminescence dosimeters chips and Monte Carlo method. To achieve this goal, in the first step, the surface dose of the cervix, kidney, abdomen region, and thyroid were measured by using TLD-GR 200 at various organ locations. Then, to evaluate the absorbed dose by simulation, the BMD system, patient's body, X-ray source and radiosensitive tissues were simulated by the Monte Carlo method. The results showed, for the spine (left femur) bone mineral density scan by using thermoluminescence dosimeters, the absorbed doses of the cervix and kidney were 4.5 (5.64) and 162.17 (3.99)(μGy), respectively. For spine (left femur) bone mineral density scan in simulation, the absorbed doses of the cervix and kidney were 4.19 (5.88) and 175 (3.68)(μGy), respectively. The data obtained showed that the absorbed dose of the kidney in the spine scan is noticeable. Furthermore, because of the small relative difference between the simulation and experimental results, the radiation absorbed dose may be assessed by simulation and software, especially for internal organs, and at different depths of otherwise inaccessible organs which is not possible in experiments. © 2014 Vinca Inst Nuclear Sci. All rights received.
Journal Of Medical Signals And Sensors (22287477) 4(4)pp. 281-290
In order to distinguish between benign and malignant types of pigmented skin lesions, computerized procedures have been developed for images taken by different equipment that the most available one of them is conventional digital cameras. In this research, a new procedure to detect malignant melanoma from benign pigmented lesions using macroscopic images is presented. The images are taken by conventional digital cameras with spatial resolution higher than one megapixel and by considering no constraints and special conditions during imaging. In the proposed procedure, new methods to weaken the effect of nonuniform illumination, correction of the effect of thick hairs and large glows on the lesion and also, a new threshold-based segmentation algorithm are presented. 187 features representing asymmetry, border irregularity, color variation, diameter and texture are extracted from the lesion area and after reducing the number of features using principal component analysis (PCA), lesions are determined as malignant or benign using support vector machine classifier. According to the dermatologist diagnosis, the proposed processing methods have the ability to detect lesions area with high accuracy. The evaluation measures of classification have indicated that 13 features extracted by PCA method lead to better results than all of the extracted features. These results led to an accuracy of 82.2%, sensitivity of 77% and specificity of 86.93%. The proposed method may help dermatologists to detect the malignant lesions in the primary stages due to the minimum constraints during imaging, the ease of usage by the public and nonexperts, and high accuracy in detection of the lesion type.
Iranian Journal of Medical Physics (17357241) 11(2-3)pp. 260-269
Introduction: Breast cancer is one of the most common types of cancer among women. Early detection of breast cancer is the key to reducing the associated mortality rate. The presence of microcalcifications clusters (MCCs) is one of the earliest signs of breast cancer. Due to poor imaging contrast of mammograms and noise contamination, radiologists may overlook some diagnostic signs, specially the presence of MCCs. In order to improve cancer detection, image enhancement methods are often used to aid radiologists. In this paper, a new enhancement method was presented for the accurate and early detection of MCCs in mammograms. Materials and Methods: The proposed system consisted of four main steps including: 1) image scaling;2) breast region segmentation;3) noise cancellation using a filter, which is sensitive to MCCs; and 4) contrast enhancement of mammograms using Contrast-Limited Adaptive Histogram Equalization (CLAHE) and wavelet transform. To evaluate this method, 120 clinical mammograms were used. Results: To evaluate the performance of the image enhancement algorithm, contrast improvement index (CII) was used. The proposed enhancement method in this research achieved the highest CII in comparison with other methods applied in this study. The Validity of the results was confirmed by an expert radiologist through visual inspection. Conclusion: Detection of MCCs significantly improved in contrast-enhanced mammograms. The proposed method could be helpful for radiologists to easily detect MCCs; it could also decrease the number of biopsies and reduce the frequency of clinical misdiagnosis. Moreover, it could be useful prior to segmentation or classification stages.
Breast cancer is one of the most prevalent cancers among women[1]. Mammography, as one of the primary studies, is used for diagnosis of breast disease. In addition MR images can depict most of the significant changes of breast during the time . For the first step of breast disease detection, the density measurement of the breast on MR Images may provide very useful information. MR images have some instinctive limitations like the strongly dependence of contrast upon the way the image is acquired, intensity inhomogeneities (Bias Field), etc. For these reasons, an effective normalization on breast MR Images is very important issue for detecting breast disease signs. The first important step for quantitative analysis of breast density on MRI is Bias Field Correction. In this study, N3 algorithm is used for correcting of field inhomogeneity in MR images.We used T1-weighted images, using a 1.5 T MRI scanner .The results demonstrate effectiveness and efficiency of the proposed method. © 2014 CSREA Press.
Iranian Journal of Medical Physics (17357241) 10(1-4)pp. 205-214
Introduction: Proton therapy is used to treat malignant tumors such as melanoma inside the eye. Proton particles are adjusted according to various parameters such as tumor size and position and patient's distance from the proton source. The purpose of this study was to assess absorbed doses in eyes and various tumors found in the area of sclera and choroid and the adjacent tissues in radiotherapy while changing most important proton therapy parameters such as moderators thickness (1.5-1.9 cm), exposure radius (0.5-0.8 cm), and proton energy beam (53.5-65 MeV). Materials and Methods: A proton therapy system of Laboratori Nazionali del Sud-INFNwas simulated by Monte Carlo method. Moreover, the eye and its components were simulated using concentric spheres. To obtain a more accurate results, real density of eye components such as cornea and lens, were applied for simulation. Then, the absorbed dose of eye and eye tumor, in choroid and sclera areas, were calculated by Monte Carlo method. Results: The absorbed dose in tumoral region of eye was calculated to be about 12.5 ±0.006Gy in one day with energy 62 MeV for a therapy session, which is suitable for treatment. However, normal eye cells received at most 11.01 Gy which is high. Conclusion: The amount of absorbed dose in tumoral cells is noticeable. Therefore, accurate treatment planning, patient immobility and fine calibration of proton-therapy system and its simulator are very important to reduce the absorbed dose of healthy cells.
Nuclear Technology and Radiation Protection (14513994) 29(1)pp. 34-39
Exposure to radiation is one of the main sources of risk to staff employed in reactor facilities. The staff of a tokamak is exposed to a wide range of neutrons and photons around the tokamak hall. The International Thermonuclear Experimental Reactor (ITER) is a nuclear fusion engineering project and the most advanced experimental tokamak in the world. From the radiobiological point of view, ITER dose rates assessment is particularly important. The aim of this study is the assessment of the amount of radiation in ITER during its normal operation in a radial direction from the plasma chamber to the tokamak hall. To achieve this goal, the ITER system and its components were simulated by the Monte Carlo method using the MCNPX 2.6.0 code. Furthermore, the equivalent dose rates of some radiosensitive organs of the human body were calculated by using the medical internal radiation dose phantom. Our study is based on the deuterium-tritium plasma burning by 14.1 MeV neutron production and also photon radiation due to neutron activation. As our results show, the total equivalent dose rate on the outside of the bioshield wall of the tokamak hall is about 1 mSv per year, which is less than the annual occupational dose rate limit during the normal operation of ITER. Also, equivalent dose rates of radiosensitive organs have shown that the maximum dose rate belongs to the kidney. The data may help calculate how long the staff can stay in such an environment, before the equivalent dose rates reach the whole-body dose limits.
Diagnostic Pathology (17461596) 9pp. 207-207
BACKGROUND: Brain segmentation in magnetic resonance images (MRI) is an important stage in clinical studies for different issues such as diagnosis, analysis, 3-D visualizations for treatment and surgical planning. MR Image segmentation remains a challenging problem in spite of different existing artifacts such as noise, bias field, partial volume effects and complexity of the images. Some of the automatic brain segmentation techniques are complex and some of them are not sufficiently accurate for certain applications. The goal of this paper is proposing an algorithm that is more accurate and less complex).
Nuclear Technology and Radiation Protection (14513994) 28(3)pp. 278-283
Ionizing particles have been used for the treatment of atherosclerosis. Internal irradiation is commonly carried out by means of several methods (catheter-based systems, radioactive stents or balloons) to reduce the probability of restenosis. 90Y, due to some of its characteristics, is an appropriate radioisotope for intravascular brachytherapy. However, since there are some critical tissues in the vicinity of the heart like the breast and lymph nodes, it is necessary to perform a dosimetry calculation around the artery under radiotherapy to justify the treatment method. In this study, a 3-D dose distribution was obtained for the coronary vessel and its surrounding tissues for a standard 90Y stent in a MCNPX program. The results were compared with other investigations on restenosis prevention using 90Y-coated stents. The calculations represented a 28-day cumulative dose between 1230 cGy and 2400 cGy at 0.1 mm from the stent surface, while this quantity was about 23.8 cGy at 8.5 mm from the stent surface. An assessment of the dose equivalent and effective dose was also performed at r = 8.5 mm for the mentioned surrounding tissues which may be located in the area, based on the latest changes in ICRP recommendations. Additionally, the dose equivalent calculated within the treatment period for these organs was compared with published dotimetry data for 90Sr/90Y seed sources in order to evaluate radiation protection concerns about these two radiotherapy methods. It has been found that, depending on stent parameters, 90Y stent implantation might increase the unfavorable side effects for the patient, but to a much lesser degree than the other methods.
Iranian Journal of Medical Physics (17357241) 10(3)pp. 139-146
Introduction: In CT imaging, metallic implants inside the tissues cause metal artifact that reduce the quality of image for diagnosis. In order to reduce the effect of this artifact, a new method with more appropriate results has been presented in this research work. Materials and Methods: The presented method comprised of following steps: a) image enhancement and metal areas extraction, b) sinogram transform of original image, c) metal segments and metal traces inside the sinogram transform of original image segmented by using Fuzzy C means, d) interpolation of metal traces inside the original image sinogram and filtering, and e) adding the image of metal parts to the filtered image to obtain the corrected image. Results: Fifty CT scan images from Alzahra Hospital in Isfahan were used to evaluate the proposed method. The proposed method was applied to images which had implants in regions such as femur, hip, tooth, brain, and stomach. The results showed an intensively reduced in metal artifact and quality improvement of images till 90% for accuracy, compared with the radiologist report. Conclusion: The proposed method reduced the effect of metal artifact by maintaining the specification of other tissues. Furthermore, the consumed time to process the suggested algorithm in this study was less than conventional methods. For instance, the consumed time for CT image, including a metal in the femur region was about 20% of the conventional method.
Mahmoudian, S. ,
Farhadi, M. ,
Gholami, S. ,
Saddadi, F. ,
Jalesi, M. ,
Karimian, A.R. ,
Darbeheshti, M. ,
Momtaz, S. ,
Fardin, S. International Tinnitus Journal (09465448) 18(1)pp. 20-28
Objectives: Subjective tinnitus has associated with abnormal brain metabolism and perfusion found in functional imaging studies by fluorodeoxyglucose (FDG) and technetium99m (TC99m). But there is no study evaluating the association of brain metabolism and perfusion abnormalities in a group of these subjects. The aim of this study was to investigate if there is any significant correlation between the brain perfusion and metabolism abnormalities in subjects with tinnitus. Materials and Methods: In this cross-sectional study, 52 patients were undergone TC99m-ECD single photon emission computerized tomography (SPECT) scan and F18-FDG positron emission tomography (PET). The results of PET and SPECT scanning were fused with MRI to accurate anatomical localization of abnormalities. The analysis was performed using Kendal's correlation, t-test and chi square. Results: Assessing these 52 tinnitus subjects (containing 42 males [76.4%]) showed that a significant correlation was found between the brain metabolic function and perfusion (p value 0.001).
Nukleonika (15085791) 57(3)pp. 407-410
Cyclotron accelerators are used to produce medical radioisotopes. One of the most important problems which may be encountered is malfunction of a part of the target or beam line which requires stopping of the bombardment and making a repair. The decision about doing the repair depends on the whole body dose rate in a target room. In this work, dosimetric conditions related to the production of 18FDG radiopharmaceutical were simulated by the Monte Carlo (MC) method. Independently, the dose rates were measured by 7 ICRU spherical body phantoms placed inside the liquid target room and the maze of the cyclotron. The radiation dose rate inside the target room depends on the duration of the bombardment and the time passed after stopping the bombardment. The correlation between duration of the bombardment and required time after stopping the bombardment to reach the absorbed dose rate less than 25 μSv/h, was calculated for the presence and absence of the irradiated target. The results showed that the repair can be started immediately after stopping of the proton bombardment only if the target has been ejected from the target room and the duration of bombardment has not taken more than 10 min.
Moradmand, H. ,
Setayeshi, S. ,
Karimian, A.R. ,
Sirous, M. ,
Akbari, M.E. 5(2)pp. 61-68
Background: Mammography is the primary imaging technique for detection and diagnosis of breast cancer; however, the contrast of a mammogram image is often poor, especially for dense and glandular tissues. In these cases the radiologist may miss some diagnostically important microcalcifications. In order to improve diagnosis of cancer correctly, image enhancement technology is often used to enhance the image and help radiologists. Methods: This paper presents a comparative study in digital mammography image enhancement based on four different algorithms: wavelet-based enhancement (Asymmetric Daubechies of order 8), Contrast-Limited Adaptive Histogram Equalization (CLAHE), morphological operators and unsharp masking. These algorithms have been tested on 114 clinical digital mammography images. The comparison for all the proposed image enhancement techniques was carried out to find out the best technique in enhancement of the mammogram images to detect microcalcifications. Results: For evaluation of performance of image enhancement algorithms, the Contrast Improvement Index (CII) and profile intensity surface area distribution curve quality assessment have been used after any enhancement. The results of this study have shown that the average of CII is about 2.61 for wavelet and for CLAHE, unsharp masking and morphology operation are about 2.047, 1.63 and 1.315 respectively. Conclusion: Experimental results strongly suggest that the wavelet transformation can be more effective and improve significantly overall detection of the Computer-Aided Diagnosis (CAD) system especially for dense breast. Compare to other studies, our method achieved a higher CII.
RAD Conference Proceedings (24664626) 2012pp. 187-189
Photon attenuation in cardiac single photon emission computed tomography (SPECT) is a well recognized problem, leading to artifacts and inaccuracies in reconstructed images therefore the attenuation correction in SPECT images is necessary. Most of the attenuation correction methods are available in clinics use attenuation map which obtained with different transmission scanning sources. Using transmission source in this correction method increases the received dose by cardiac and other tissues around it. The object of this study is to assess the extra absorbed dose of cardiac and other tissues around it during the Transmission Attenuation Correction (TAC) of cardiac SPECT imaging. So using Monte Carlo method the cardiac and torso were simulated in cylindrical coordinate then the extra absorbed dose of cardiac and its surrounding tissues during TAC were calculated. The results showed cardiac, its surrounding tissues and skin have absorbed non-considerable extra absorbed dose which are much lower than the reported limits by ICRP103. © 2012 RAD Conference Proceedings. All rights reserved.
RAD Conference Proceedings (24664626) 2012pp. 59-62
ITER (International Thermonuclear Experimental Reactor) is an international nuclear fusion research and engineering project, which is the largest international science project and most advanced experimental tokamak nuclear fusion reactor. Dose rates assessment and gamma radiation due to the neutron activation of the solid structures in ITER is important from the radiological point of view. Therefore, the gamma dosimetry considered in this case is based on neutron activation due to the Deuterium-Tritium (DT) plasma burning with neutrons production rate at 14.1 MeV. The aim of this study is the assessment of gamma dose rates around ITER by considering neutron activation and delay gammas. To achieve the aim, the ITER system and its components were simulated by Monte Carlo method. Also to increase the accuracy and precision of the absorbed dose assessment the activation of walls around the ITER system were considered in the simulation. The results of this research showed that the total dose rate level near to the outside of bio-shield wall of Tokamak hall is not more than dose limits. © 2012 RAD Conference Proceedings. All rights reserved.
Mahmoudian, S. ,
Farhadi, M. ,
Gholami, S. ,
Saddadi, F. ,
Karimian, A.R. ,
Mirzaei, M. ,
Ghoreyshi, E. ,
Ahmadizadeh, M. ,
Lenarz, T. Journal Of Research In Medical Sciences (17357136) 17(3)pp. 55-60
Background and Purpose: Tinnitus is associated with an increased activity in central auditory system as demonstrated by neuroimaging studies. Brain perfusion scanning using single photon emission computed tomography (SPECT) was done to understand the pattern of brain blood perfusion of tinnitus subjects and find the areas which are mostly abnormal in these patients. Materials and Methods: A number of 122 patients with tinnitus were enrolled to this cross-sectional study. They underwent SPECT and magnetic resonance imaging (MRI) of brain, and the images were fused to find the regions with abnormal perfusion. Results: SPECT scan results were abnormal in 101 patients (83%). Most patients had bilateral abnormal perfusion (N = 65, 53.3%), and most subjects had abnormality in middle-temporal gyrus (N = 83, 68%) and temporoparietal cortex (N = 46, 37.7%). Patients with multifocal involvement had the least mean age than other 2 groups (patients with no abnormality and unifocal abnormality) (P value = 0.045). Conclusions: Brain blood perfusion pattern differs in patient with tinnitus than others. These patients have brain perfusion abnormality, mostly in auditory gyrus (middle temporal) and associative cortex (temporoparietal cortex). Multifocal abnormalities might be due to more cognitive and emotional brain centers involvement due to tinnitus or more stress and anxiety of tinnitus in the young patients.
Radiation Protection Dosimetry (17423406) 147(1-2)pp. 296-299
Cardiac disease is one of the most important causes of death in the world. Coronary artery stenosis is a very common cardiac disease. Intravascular brachytherapy (IVBT) is one of the radiotherapy methods which have been used recently in coronary artery radiation therapy for the treatment of restenosis. 90Sr/ 90Y, a beta-emitting source, is a proper option for cardiovascular brachytherapy. In this research, a Monte Carlo simulation was done to calculate dosimetry parameters and effective equivalent doses to the heart and its surrounding tissues during IVBT. The results of this study were compared with the published experimental data and other simulations performed by different programs but with the same source of radiation. A very good agreement was found between results of this work and the published data. An assessment of the risk for cardiac and other sensitive soft tissues surrounding the treated vessel during 90Sr/ 90Y IVBT was also performed in the study. © The Author 2011. Published by Oxford University Press. All rights reserved.
Radiation Protection Dosimetry (17423406) 147(1-2)pp. 250-253
The medical radioisotope 201Tl is produced by a cyclotron through the. 203Tl(p, 3n) 201Pb reaction in the nuclear medicine research group of Agricultural, Medical and Industrial Research Schools in Iran. The produced 201Pb decays to 201Tl by electron capture. One of the most important problems that may occur is malfunction of a part of target or beam line, so that it needs the bombardment to be stopped and the problem fixed. In this work, induced radioactivity of the target, aluminium case of target, beam line and concrete walls of the thallium target room were calculated by Monte Carlo method. Then by using the results of the Monte Carlo simulation, the whole body absorbed dose to cyclotron personnel during repair and after stopping the bombardment, were assessed at different places of target room. © The Author 2011. Published by Oxford University Press. All rights reserved.
Mossadegh n., ,
Karimian, A.R. ,
Shahhosseini e., ,
Mohammadzadeh a., ,
Sheibani s., S. Radiation Protection Dosimetry (17423406) 147(1-2)pp. 267-271
Due to their work conditions, research reactor personnel are exposed to ionising nuclear radiations. Because the absorbed dose values are different for different tissues due to variations in sensitivity, in this work personal dosimetry has been performed under normal working conditions at anatomical locations relevant to more sensitive tissues as well as for the whole body by employing a Rando phantom and thermoluminescent dosemeters (TLDs). Fifty-two TLDs-100H were positioned at high-risk organ locations such as the thyroid, eyes as well as the left breast, which was used to assess the whole-body dose in order to study the absorbed doses originating from selected locations in the vicinity of the reactor. The results have employed the tissue weighting factors based on International Commission on Radiological Protection ICRP 103 and ICRP 60 and the measured results were below the dose limits recommended by ICRP. The mean effective dose rates calculated from ICRP 103 were the following: whole body, 30.64-6.44 μSv h -1; thyroid, 1.22-0.23 μSv h -1; prostate, 0.085-0.045 μSv h -1; gonads, 1.00-0.51 mSv h -1; breast, 3.68-0.77 μSv h -1; and eyes, 33.74-7.01 μSv h -1. © The Author 2011. Published by Oxford University Press. All rights reserved.
Physics Procedia (18753892) 22pp. 209-211
Metal artifact is one of the major problems in CT images. To overcome this problem a new algorithm has been suggested in this research. This algorithm has five steps means: a) Extraction the metal region from the image, b) Filtration the extracted metallic region, c) Segmentation and accurate extraction of metallic pieces by FCM (Fuzzy C Means) method, d) Using the interpolation on the sinogram and finally e) Insert the corrected metallic section of image to the original image. The results of this research showed, by using this new algorithm the output image has better contrast, signal to noise ratio and visibility with much less consumed time than the other reported methods. © 2011 Published by Elsevier B.V.
Radiation Protection Dosimetry (17423406) 147(1-2)pp. 176-179
Radiographic inspection is one of the most widely employed techniques for medical testing methods. Because of poor contrast and high un-sharpness of radiographic image quality in films, converting radiographs to a digital format and using further digital image processing is the best method of enhancing the image quality and assisting the interpreter in their evaluation. In this research work, radiographic films of 70 infant chest images with different sizes of defects were selected. To digitise the chest images and employ image processing the two algorithms (i) spatial domain and (ii) frequency domain techniques were used. The MATLAB environment was selected for processing in the digital format. Our results showed that by using these two techniques, the defects with small dimensions are detectable. Therefore, these suggested techniques may help medical specialists to diagnose the defects in the primary stages and help to prevent more repeat X-ray examination of paediatric patients. © The Author 2011. Published by Oxford University Press. All rights reserved.
Iranian Journal of Physics Research (16826957) 10(3)pp. 177-185
In nuclear medicine, studies of important tissues such as cardiac, the emitted photons from the cardiac before reaching the gamma detectors are attenuated and scattered by other tissues inside the thorax. Therefore, the quality and contrast of the image will be reduced. In this research, to improve the quality of cardiac images by SPECT system, the most convenient algorithms for attenuation correction were studied and assessed in the first step. Then the best method using the line source in Transmission Attenuation Correction (TAC) method was modified and the experimental data wase obtained by using this new and modified method, cardiac phantom, Dual Head SPECT system and a line source of 201Tl with the activity of about 0.5 mCi. The data was collected and obtained in two steps: (1) Scanning the cardiac phantom and line source which was beside the cardiac phantom this step involves using emission and transmission simultaneously. (2) Scanning the cardiac phantom in the absence of line source which means using emission data. Next, the suggested attenuation correction formula was used and the calculated attenuation coefficient for each pixel was calculated and applied to each pixel. Our results showed a nice improvement in contrast and visibility of the images by this simple and in imporoved expensive method. The advantages of this method include simplicity, the available radionuclide, improved accuracy, quality and contrast of the final image, and finally, cost - effectiveness. These advantages may help the nuclear medicine centers to improve their ability to detect the physiological and functional defects of the cardiac, especially in the elder and women patients.
Jalilian, A.R. ,
Aboudzadeh, R. ,
Akhlaghi, M. ,
Shirazi, B. ,
Moradkhani, S. ,
Salouti, M. ,
Karimian, A.R. ,
Babaii, M.H. ,
Raisalia, G. Journal of Labelled Compounds and Radiopharmaceuticals (03624803) 53(4)pp. 214-214
Farhadi, M. ,
Mahmoudian, S. ,
Saddadi, F. ,
Karimian, A.R. ,
Mirzaee, M. ,
Ahmadizadeh, M. ,
Ghasemikian, K. ,
Gholami, S. ,
Ghoreyshi, E. ,
Beyty, S. Journal of Cerebral Blood Flow and Metabolism (0271678X) 30(4)pp. 864-870
Tinnitus is often defined as the perception of sounds or noise in the absence of any external auditory stimuli. The pathophysiology of subjective idiopathic tinnitus remains unclear. The aim of this study was to investigate the functional brain activities and possible involved cerebral areas in subjective idiopathic tinnitus patients by means of single photon emission computerized tomography (SPECT) coincidence imaging, which was fused with magnetic resonance imaging (MRI). In this cross-sectional study, 56 patients (1 subject excluded) with subjective tinnitus and 8 healthy controls were enrolled. After intravenous injection of 5mCi F18-FDG (fluorodeoxyglucose), all subjects underwent a brain SPECT coincidence scan, which was then superimposed on their MRIs. In the eight regions of interest (middle temporal, inferotemporal, medial temporal, lateral temporal, temporoparietal, frontal, frontoparietal, and parietal areas), the more pronounced values were represented in medial temporal, inferotemporal, and temporoparietal areas, which showed more important proportion of associative auditory cortices in functional attributions of tinnitus than primary auditory cortex. Brain coincidence SPECT scan, when fused on MRI is a valuable technique in the assessment of patients with tinnitus and could show the significant role of different regions of central nervous system in functional attributions of tinnitus. © 2010 ISCBFM All rights reserved.
IFMBE Proceedings (16800737) 25(2)pp. 414-416
In nuclear medicine imaging systems such as Gamma camera and SPECT, currently uses a mechanical collimator and a scintillation detector to detect distribution of gamma emitter radiopharmaceuticals. The detection technique, however, suffers from spatial resolution and sensitivity trade-off because of mechanical collimation. Compton camera principle is a suggested alternative which avoids the mentioned trade-off. Compton camera consists of one scattering detector and one absorber detector. Compton scattering of emitted photons from the source is detected in a special scattering detector which replaces the mechanical collimator. This research study simulated a Compton camera which is composed of a "Si" scattering detector (dimensions: 22.4 × 22.4 × 14 mm3) in a distance of "D" from an absorber detector (NaI(Tl), dimensions: 20 × 20 × 1 cm3). To evaluate the image quality of the designed Compton camera in different and inside the spread range of energies which uses for nuclear medicine studies, the point sources of Tc-99m (140 keV), I-131 (364.4 keV) and C-11 (511 keV) are assumed to be located in the front of the scattering detector and in the distance of "h= 10 mm" from it, and important parameters which affects on image quality, were calculated, analyzed and the best thickness for scattering detector were found. The thickness of absorber detector was assumed 10 mm which is about the thickness of detectors in SPECT systems. This study modeled the Compton camera realistically with all the details of the Compton camera such as Doppler broadening. Our results showed the spatial resolution would improve while the sensitivity would decrease by increasing the distance between scattering and absorber "D". Also the optimum "D = 20 cm" at "h=1 cm" were found. Furthermore our results showed by increasing the photo peak energy of isotope the spatial resolution and sensitivity would improve significantly. © 2009 Springer-Verlag.
IFMBE Proceedings (16800737) 25(2)pp. 741-744
Brain disorders are divided into two categories: anatomic and metabolic. Since brain disorders initially appear as metabolic abnormalities and ultimately result in anatomic defects, it is necessary to analyze the metabolic along with the anatomic aspect of the brain tissue in the preliminary stages of diagnosis to greatly increase the chances of a cure. It is possible that metabolic abnormalities exist without an anatomic defect such as Alzheimer disease. The brain anatomic images may achieve from MRI and physiologic and metabolic brain data can achieve from DHC-SPECT or PET system when a radiopharmaceutical such as FDG have been injected to the patient. For fusion of the brain MRI and DHC-SPECT images obtained from individual scanners, we developed the userfriendly FMDIB software in the MATLAB environment. With the help of this software, we resolved the geometrical misalignment of the brain images and subsequently co-registered them with a 1 mm precision. This software enabled us to perform the three dimensional rendering of the image, re-slicing the image with thickness of 1 to 3 mm, slicing the two dimensional DHC-SPECT projections into an arbitrary direction. © 2009 Springer-Verlag.
Moghaddam, N.M. ,
Karimian, A.R. ,
Mostajaboddavati, S.M. ,
Vondervoort, E. ,
Sossi, V. Nukleonika (15085791) 54(1)pp. 33-38
Preliminary design of a spherical brain PET (SBPET) using liquid xenon (LXe) as detector is considered in this research work. The major advantage of a spherical design is the large solid angle of acceptance which improves the sensitivity and increases signal-to-noise ratio (SNR) of the image. The use of a liquid active medium enabled us to design a spherical detector. LXe, due to the intrinsic physical properties, is an excellent liquid medium for accurate tracking of gamma rays in the relevant energy range. The performance of SBPET was evaluated by Monte Carlo simulation tools (GATE) and compared to ECAT HRRT. The numerical results showed the SBPET has a sensitivity of 1.14% and spatial resolution of ~2.7 mm FWHM which is superior to ECAT HRRT especially at high-count rates.
Sadeghi m., M. ,
Mirzaee m., ,
Gholamzadeh z., ,
Karimian, A.R. ,
Novin, F.B. Radiochimica Acta (21933405) 97(2)pp. 113-116
Electrodeposition of silver on copper substrate was carried out using alkaline plating baths for production of Cadmium-109 via the natAg(p, n)109Cd nuclear reaction. The target could withstand 15 MeV proton beam currents of up to 150 μA; the 109Cd production yield was 1.88 μCi/μAh (0.069 MBq/(μAh). Cadmium-109 was separated from silver and non-isotopic impurities by ion-exchange chromatography. © by Oldenbourg Wissenschaftsverlag, München.
Nukleonika (15085791) 53(1)pp. 3-6
The main aim of this work is to investigate the use of new lanthanum bromide (LaBr3) in whole body PET (WB-PET) scanners and to compare the obtained results with those for BGO and LSO crystals which are currently used in conventional and dedicated PET systems. Our results show that there is a gain in noise effective count rate (NECR) arising from the reduced scatter and random fractions in a LaBr3 scanner. The spatial resolution of the WB-PET with LaBr3 is slightly worse than the LSO and BGO crystals because of its low density and effective atomic number. But our study showed the increased NECR, excellent energy resolution and low decay time of LaBr 3 which promise a significant improvement in WB-PET performances especially for narrow coincidence windows.
IFMBE Proceedings (16800737) 14(1)pp. 1698-1699
The main aim of this work is the investigation of using new lanthanum bromide (LaBr3) in whole body PET scanners and compares its results with LSO and BGO crystals which are using in conventional and dedicated PET systems. Our results show that there is a gain in noise effective count rate (NECR) arising from the reduced scatter and random fractions in a LaBr3 scanner. © International Federation for Medical and Biological Engineering 2007.
Jalilian, A.R. ,
Garosi, J. ,
Gholami, E. ,
Akhlaghi, M. ,
Saddadi, F. ,
Bolourinovin, F. ,
Karimian, A.R. Nuclear Medicine Review (16444345) 10(2)pp. 71-75
Background: Radiolabelled human recombinant insulin can be used for the imaging of insulin receptors in some tumours where FDG has natural uptake and diminishes the value of its imaging. Material and methods: Insulin was successively labelled with [67Ga]-gallium chloride after conjugation with freshly prepared cyclic DTPA-dianhydride (HPLC radiochemical purity assay > 96%) followed by biodistribution studies in normal rats, white blood cell labelling and preliminary SPECT studies. Results: In vitro studies demonstrated the retention of radiolabelled insulin receptor affinity using freshly prepared human white blood cells at different blood sugar conditions. Preliminary in vivo studies in a normal rat model was performed to determine the biodistribution of the radioimmunoconjugate at up to 44 h. SPECT images revealed high uptake of the liver. Conclusion: Radiolabelled insulin is stable enough to be used in biological studies in order to image insulin receptors in diabetic conditions as well as possible tumour imaging applications. The data was consistent with other radiolabelled insulin studies. Copyright © 2007 Via Medica.
Jalilian, A.R. ,
Aboudzadeh, R. ,
Akhlaghi, M. ,
Shirazi, B. ,
Moradkhani, S. ,
Salouti, M. ,
Karimian, A.R. ,
Babaii, M.H. ,
Raisali g., G. Journal of Labelled Compounds and Radiopharmaceuticals (03624803) 50(5-6)pp. 556-557
Jalilian, A.R. ,
Akhlaghi, M. ,
Saddadi, F. ,
Mirzaii, M. ,
Karimian, A.R. ,
Pouladi m., ,
Yari kamrani y., ,
Moradkhani, S. ,
Shadanpour n., Iranian Journal Of Nuclear Medicine (20082509) 14(26)
Introduction: [18F]-6-thia-14-fluoro-heptadecanoic acid 3b, a free fatty acid, has been used in myocardial PET imaging. In order to establish an automated synthesis module for routine production in the country, a study performed for optimization of the production conditions as well as making modifications. Methods: [18F] Benzyl-14-Fluoro-6-thia-heptadecanoate 2b was prepared in no-carrier-added (n.c.a) form from Benzyl-14-tosyloxy-6-thia- heptadecanoate 1 in one step at 90°C in Kryptofix2.2.2/[18F] and acetonitrile as the solvent followed by Silica column chromatography. The radiolabeled ester 2 was then hydrolyzed to yield [18F]-6-thia-14- fluoro-heptadecanoic 3b. The final solution was concentrated using C 18 SPE system and administered to normal rats for biodistribution as well as co-incidence imaging studies. Results: The synthesis took 15 min with overall radiochemical yield of 15-25% (EOS) and chemical-radiochemical purity more than 94%. Automation was performed using a two-pot synthesis. The best imaging time was shown to be 140-180 minutes post injection. Conclusions: Using this procedure a fast, reliable, automated synthesis for the cordial PET tracer, i.e. [18F]-FTHA can be obtained without HPLC purification step.
Jalilian, A.R. ,
Hosseini, M.A. ,
Karimian, A.R. ,
Saddadi, F. ,
Sadeghi m., M. Nukleonika (15085791) 51(4)pp. 203-208
Thallium-201 (T1/2 = 3.04 days) in Tl+ form was converted to Tl3+ cation in presence of O3 in 6 M HCl controlled by RTLC/gel electrophoresis methods. The final evaporated activity was reacted with vancomycin (VAN) in water to yield [201Tl](III)VAN. The best results were obtained at room temperature in water after 30 min with a radiochemical yield > 99%, after mixing the reactants followed by SPE purification using Si Sep-Pak. The studies showed that thallic ion is mostly incorporated into vancomycin with a radiochemical purity of more than 98 ± 1% by RTLC. A specific activity of about 4.14 × 1010 Bq/mmol was obtained. Radiochemical purity and stability of 201Tl-VAN in the preparation and in presence of human serum was determined up to 5.5 days. Biodistribution study of 201Tl(III)-vancomycin in normal rats was performed up to 52 h.
Nuclear Medicine Review (16444345) 9(2)pp. 108-113
Background: [18F]-6-thia-14-fluoro-heptadecanoic acid 3b, a free fatty acid, has been used in myocardial PET imaging. In order to establish an automated synthesis module for routine production in the country, a study was performed for optimization of the production conditions as well as making modifications. Material and Methods: [18F]Benzyl-14-Fluoro-6-thia- heptadecanoate 2b was prepared in no-carder-added (n.c.a) form from Benzyl-14-tosyloxy-6-thia-heptadecanoate 1 in one step at 90°C in Kryptofix2.2.2/[18F] with acetonitrile as the solvent followed by Silica column chromatography. The radiolabelled ester 2 was then hydrolysed to yield [18F]-6-thia-14-fluoro-heptadecanoic 3b. The final solution was concentrated using the C18 SPE system and administered to normal rats for biodistribution and co-incidence imaging studies. Results: The synthesis took 15 min with overall radiochemical yield of 15-25% (EOS) and chemical-radiochemical purity of more than 90%. Automation was performed using a two-pot synthesis. The best imaging time was shown to be 140-180 minutes post injection. Conclusions: Using this procedure a fast, reliable, automated synthesis for the cardial PET tracer, i.e. [18F]FTHA, can be obtained without an HPLC purification step. Copyright © 2006 Via Medica.
Rowshanfarzad, P. ,
Jalilian, A.R. ,
Kiyomarsi, M. ,
Sabet, M. ,
Karimian, A.R. ,
Moradkhani, S. ,
Mirzaii, M. Nukleonika (15085791) 51(4)pp. 209-215
Rubidium-82m was prepared via 15.4 MeV proton irradiation of a krypton-82 gaseous target (30% enrichment). Washing the target chamber with hot water yielded a Rb-82m containing solution, which was further purified using short column chromatography in order to remove organic/inorganic impurities. The flowthrough was formulated in normal saline for injection. Radionuclide, radiochemical and chemical purity tests were performed prior to administration to rats for imaging (radiochemical yield: 95-97%, radiochemical purity > 97%). Preliminary dual-head coincidence studies were performed to determine the distribution of [82mRb]Rb in normal rats. For biodistribution studies, Rb-81 was injected to rats and tracer accumulation in heart, GI and bladder was determined after sacrification in time intervals. A yield of 1.3 GBq at EOB, 235.7 MBq/μAh was obtained.
Karimian, A.R. ,
Thompson, C.J. ,
Sarkar s., ,
Raisali g., ,
Pani r., ,
Davilu h., ,
Sardari d., Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment (01689002) 545(1-2)pp. 427-435
We propose a Cylindrical Breast PET (CYBPET) system for breast imaging with patients in the prone position. An individual pendulous breast is covered by thin plastic to provide reduced pressure fixation and surrounded by the crystals inside the CYBPET ring. Each breast is imaged separately. The rest of the body is shielded properly to minimize the contribution of scattered photons from the other breast and the rest of the body. To compare the CYBPET with whole-body PET (WB-PET) the simulations of CYBPET and a WB-PET (GE-Advance) for a 10 mm tumor inside the breast with a lesion to background (breast) activity concentration of 6 to 1 were made. The noise effective count rate (NECR) of CYBPET is about twice that of WB-PET at activity concentrations less than 3.1 μCi/cc. The spatial resolution of CYBPET is better by 25% than the WB-PET. © 2005 Elsevier B.V. All rights reserved. All rights reserved.
Jalilian, A.R. ,
Fateh, B. ,
Ghergherehchi, M. ,
Karimian, A.R. ,
Moradkhani, S. ,
Kamali-dehghan, M. ,
Tabeie, F. Nukleonika (15085791) 50(4)pp. 143-148
Bleomycin (BLM), labeled with radioisotopes, is widely used in therapy and diagnosis. In this study, BLM was labeled with 62Zn for oncologic PET studies. The complex was obtained at pH = 2 in saline at 90°C in 25 min. Radio-TLC showed an overall radiochemical yield of 95-97% (radiochemical purity > 97%). Stability of complex was checked in vitro in mice and human plasma/urine. Preliminary in vivo studies were performed to determine complex stability and distribution of 62Zn BLM in normal and fibrosarcoma-bearing mice. 62Zn BLM accumulated significantly in induced fibrosarcoma tumors in mice according to biodistribution/imaging studies. 62Zn BLM can be used in PET oncology studies due to its suitable physicochemical properties as a diagnostic complex in vitro and in vivo. Further studies should be performed for evaluation of the complex behavior in larger mammals.
Karimian, A.R. ,
Thompson, C.J. ,
Sarkar s., ,
Raisali g., ,
Pani r., ,
Davilu h., ,
Sardari d., IEEE Nuclear Science Symposium Conference Record (10957863) 4pp. 2339-2341
Early detection of breast cancer is very important for efficient and effective treatment. Conventional whole body PET (WB-PET) scanners provide metabolic images of breast cancer with several shortcomings related to the general-purpose nature of these systems. We propose a Cylindrical Breast PET (CYBPET) system for breast imaging, for the patients in the prone position. An individual pendulous breast is covered by a thin plastic to make a mild pressure and surrounded by the crystals inside the CYBPET ring and will positioned in the center of field of view. Each breast is imaged separately. The rest of the body has been shielded properly to minimize the contribution of scattered photons from the other breast and the rest of the body. This proposed system configuration has several advantages over the WB-PET system configuration for breast imaging, namely: I) greatly reduced attenuation and scattering effects in breast imaging; II) reduced interference from activity in parts the torso in the FOV; III) elimination a separate attenuation scan due to the homogeneity of breast; IV) reduced number of detectors and its' related electronics to reduce the price of the system. Before building the CYBPET instrument, we have simulated it using the PETSIM Monte Carlo program. Simulations of CYBPET and a (WB-PET) for a 8mm tumor inside the breast with a lesion to background activity concentration of 10 to 1 were made. The NECR (max) for CYBPET (WB-PET) were 203(184) (kcps) in the activity concentration of 3.2(10.4) (μCi/cc). Also the coincidence efficiency show the amounts of 470 and 132 (kcps/μCi/cc) for CYBPET and WB-PET respectively. These results and the advantages listed above suggest improved lesion visualization in the early disease stages. The only shortcoming, like the PEM, SPEM and manunography systems is, this system would not be able to detect the lesions which are very close to chest wall. © 2004 IEEE.
Pani r., ,
Bennati p., ,
Cinti m.n., ,
Pellegrini r., ,
Betti m., ,
Ridolfi s., ,
Lanconelli n., ,
Karimian, A.R. ,
Garibaldi f., ,
Cusanno f., IEEE Nuclear Science Symposium Conference Record (10957863) 6pp. 3748-3751
Although Scintimammography is routinely used in the hospitals it had not the expected large diffusion. The low specificity of SESTAMIBI 99mTc and the geometrical restrictions of prone scintimammography further contributed in limiting the clinical sensitivity for sub centimeter lesions. Researchers aware that to overcome intrinsic limitation of radio-pharmaceutical, they are optimized compact imager able to detect small amount of radioactivity emitted from 5 mm or less tumors. To investigate the overall imaging characteristics of scintillation imagers for scintimammography, a number of small gamma camera prototypes were assembled, based on PSPMT of first and last generation. They were coupled to a number of Nal(Tl) and Csl(Tl) scintillation both planar and pixellated, with different pixel size. Measurements were performed by line and circular source as well as by 3 nun to 10 mm diameter tumor phantoms. Spatial resolution seems the dominant factor, in detection of 5 mm and 3 nun tumor size. The best results were obtained from the scintillation crystals arrays coupled to Hamamatsu Flat Panel PMT. Decreasing crystal pixel size, contrast mean values slightly changed but their accuracy increases, demonstrating the influence of digitization on image quality. MTF curve obtained by planar NaI(Tl) integral assembly shows an improvement with a response at the highest frequency equal to one obtained from collimator parallel hole Monte Carlo simulation © 2004 IEEE.
Pani r., ,
Cinti m.n., ,
De notaristefani f., ,
Pellegrini r., ,
Bennati p., ,
Betti m., ,
Trotta g., ,
Karimian, A.R. ,
Mattioli m., ,
Garibaldi f., IEEE Nuclear Science Symposium Conference Record (10957863) 4pp. 2283-2287
Over the last three years, there is a growing interest in the development of a new class of fast scintillators like LaCl 3:Ce and LaBr 3:Ce. The new scintillation crystals for the first time, have the main characteristic in producing a light photon number higher than NaI(Tl) at a wavelength suited for the photocathode. The most important characteristic of these crystals is represented from the scintillation light to be yield proportionality as a function of incident gamma ray energy. With the aim to investigate on their potential in Single Photon Imaging three one inch square LaCl 3:Ce continuous scintillation crystals with 3 and 6 mm thickness were specifically designed for position measurements. They have been coupled to a Flat panel PMT through a 3 mm thickness glass window. In order to highlight all the characteristics of the detection system the third one, 3 mm thick, was integral assembled with a one inch PSPMT Hamamatsu R5900-C8. Free and collimated point radioactive sources were used for energy resolution measurements as well for scanning crystals to investigate spatial resolution and position response. Energy resolution values were compared with ones obtained from a sample of LaBr 3:Ce with one inch diameter and one thickness designed for spectrometric measurements. LaCl 3:Ce with 3 mm thickness shown energy resolution values worse than expected (13% at 140 KeV) due to the sub-optimal size and configuration for light collection. On the contrary LaBr 3:Ce carried out 6% relative energy resolution at 140 keV. Intrinsic spatial resolution values of 1 mm and 1.3 mm were obtained from 3 mm thickness LaCl 3:Ce crystals in the two configurations investigated. © 2004 IEEE.
