Alireza Karimian
Department of Biomedical Engineering - Faculty of Engineering- University of Isfahan
[ 1 ] - Assessment of X-Ray Crosstalk in a Computed Tomography Scanner with Small Detector Elements Using Monte Carlo Method
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 e...
[ 2 ] - Designing and Fabrication of a New Radiofrequency Planar microcoil for mini-Nuclear Magnetic Resonance
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 ...
[ 3 ] - Contrast Enhancement of Mammograms for Rapid Detection of Microcalcification Clusters
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 t...
[ 4 ] - Dose Assessment of Eye and Its Components in Proton Therapy by Monte Carlo Method
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 radiotherap...
[ 5 ] - A New Method for Metal Artifact Reduction in CT Scan Images
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) sinog...
[ 6 ] - روشی جدید جهت بخش‌بندی ضایعات مالتیپل اسکلروزیس (MS) در تصاویر MR مغزی
بخش‌بندی ضایعات مالتیپل اسکلروزیس (MS) در تصاویر MR مغزی به منظور کمک به تشخیص و پیگیری این بیماری در سالهای اخیر مورد توجه قرار گرفته است. در این مطالعه از مدل ترکیب گوسی (GMM) برای قطعه‌بندی ضایعات MS در تصاویر MR استفاده شد. به منظور بهینه‌سازی GMM از الگوریتم بیشینه‌سازی امید ریاضی (EM) استفاده می‌شود اما این الگوریتم معمولاً به یک نقطه بهینه محلی همگرا می‌شود که برای رهایی از گیر افتادن در ...
[ 7 ] - A TLD based method to estimate bowtie filter shape in PET/CT
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 often 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 ...
[ 8 ] - روشی جدید جهت بهینه‌سازی تصحیح اثر تضعیف پرتوهای گاما در تصویرگیری از قلب با روش SPECT
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 cor...
[ 9 ] - روشی جدید جهت بخش‌بندی ضایعات مالتیپل اسکلروزیس (MS) در تصاویر MR مغزی
بخش‌بندی ضایعات مالتیپل اسکلروزیس (MS) در تصاویر MR مغزی به منظور کمک به تشخیص و پیگیری این بیماری در سالهای اخیر مورد توجه قرار گرفته است. در این مطالعه از مدل ترکیب گوسی (GMM) برای قطعه‌بندی ضایعات MS در تصاویر MR استفاده شد. به منظور بهینه‌سازی GMM از الگوریتم بیشینه‌سازی امید ریاضی (EM) استفاده می‌شود اما این الگوریتم معمولاً به یک نقطه بهینه محلی همگرا می‌شود که برای رهایی از گیر افتادن در ...
[ 10 ] - Estimation of fetal absorbed dose from low-dose attenuation-correction CT in PET / CT imaging by using the Body Builder Phantom
One of the methods of studying the physiology and metabolism of important tissues such as the heart, brain and cancer tumors is the use of PET/CT System. A small number of patients are pregnant women who undergo a PET/CT scan due to lack of knowledge about pregnancy or due to dire clinical need. The final dose received by the fetus is based on three factors: the absorbed dose of the fetal tissu...
[ 11 ] - Calculation of the Equivalent Dose of the First and the Most Important Secondary Particles in Brain Proton Therapy by Monte Carlo Simulation
Introduction: Due to nuclear interactions between the tissues and high-energy protons, the particles, including neutrons, positrons, and photons arise during proton therapy. This study aimed at investigating the dose distribution of proton and secondary particles, such as positrons, neutrons, and photons using the Monte Carlo method. Material and Methods:<...
[ 12 ] - stimate bowtie filter shape in PET/CT scan with TLD
Introduction: The CT machine utilizes a bowtie filter to shape the X-ray beam and remove lower energy photons. Configuration of this bowtie filter is complex and its geometry is often not available in detail. It causes the CT dose index (CTDI) be with the different values in measurement versus Monte Carlo simulation studies and other analytical calculations. It is important esp...
[ 13 ] - Estimate bowtie filter shape in PET/CT scan with TLD
Introduction: The CT machine utilizes a bowtie filter to shape the X-ray beam and remove lower energy photons. Configuration of this bowtie filter is complex and its geometry is often not available in detail. It causes the CT dose index (CTDI) be with the different values in measurement versus Monte Carlo simulation studies and other analytical calculations. It is important esp...
[ 14 ] - Impact of region of interest size and location in Gafchromic film dosimetry
Introduction: Accurate film dosimetry requires careful consideration of sources of uncertainty. Some of the sources of uncertainty are dependent on the size and location of region of interest (ROI), especially in small fields. Avoiding the penumbra is often a reason for using a small ROI. In contrast, choosing very small ROIs may increase uncertainty due to the reduction of th...
[ 15 ] - Calculation of total dose and dose equivalent distribution in the treatment of lung cancer using MR-guided carbon therapy
Nowadays, in order to improve the accuracy of treatment in radiation therapy, there are many attempts to use magnetic resonance imaging (MRI) due to the advantages of excellent soft tissue contrast and ultra-fast pulse sequences. On the other hand, carbon-ion radiation therapy is developing rapidly due to the benefits of greater relative biological effectiveness (RBE) and the application in the...
[ 16 ] - Absorbed dose of Fetus in SPECT-CT Imaging of Mother's Abdomen Regions using Monte Carlo method
SPECT-CT is an imaging method for diagnosing diseases and studying physiology of the body. In this type of imaging, due to the use of radiopharmaceutical for imaging (SPECT) and X-rays (CT), a relatively high dose of radiation is introduced into the patient. If the patient is pregnant, considering that the developing fetus is sensitive to any radiation in the uterus throughout the entire period...
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