A Unified Framework for Brain Segmentation in MR Images.

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.

Assessment of physician and patient (child and adult) equivalent doses during renal angiography by Monte Carlo method.

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 7.9E-4 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.

Absorbed dose assessment of cardiac and other tissues around the cardiovascular system in brachytherapy with 90Sr/90Y source by Monte Carlo simulation.

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. (90)Sr/(90)Y, 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 (90)Sr/(90)Y IVBT was also performed in the study.

Experimental simulation of personal dosimetry in production of medical radioisotopes by research reactor.

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 µSv h(-1); breast, 3.68-0.77 µSv h(-1); and eyes, 33.74-7.01 µSv h(-1).

Assessment of personnel absorbed dose at production of medical radioisotopes by a cyclotron.

The medical radioisotope (201)Tl is produced by a cyclotron through the (203)Tl(p, 3n)(201)Pb reaction in the nuclear medicine research group of Agricultural, Medical and Industrial Research Schools in Iran. The produced (201)Pb decays to (201)Tl 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.

Reducing the absorbed dose in analogue radiography of infant chest images by improving the image quality, using image processing techniques.

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.