Hossein Rajabi
Associate Professor, Medical Physics Dept., Faculty of Medicine, Tarbiat Modares University, Tehran, Iran
[ 1 ] - Attenuation Correction in SPECT during Image Reconstruction using an Inverse Monte Carlo Method: A Simulation Study
Introduction: The main goal of SPECT imaging is to determine activity distribution inside the organs of the body. However, due to photon attenuation, it is almost impossible to do a quantitative study. In this paper, we suggest a mathematical relationship between activity distribution and its corresponding projections using a transfer matrix. Monte Carlo simulation was used to find a precise tr...
[ 2 ] - Estimating Tumor/Non-Tumor Uptake from Radiolabeled Monoclonal Antibodies using Scintigraphic Images and Dissecting the Animal Models
Introduction: Biodistribution study in animal models bearing tumors is one of the most important procedures in evaluation of fractional uptake of radiopharmaceuticals in the tumor and non-tumor organs. The aim of this study was to develop a new software-based method to determine activities that accumulate in the main organs as well as the tumor based on scintigraphy images, thereby obviating th...
[ 3 ] - Compensation of Cross-Contamination in Simultaneous 201Tl/99mTc Myocardial Perfusion SPECT Imaging
Introduction: It is a common protocol to use 201Tl for the rest and 99mTc for the stress cardiac SPECT imaging. Theoretically, both types of imaging may be performed simultaneously using different energy windows for each radionuclide. However, a potential limitation is the cross-contamination of scattered photons from 99mTc and collimator X-rays into the 201Tl energy window. We used a middle en...
[ 4 ] - Assessment of the Wavelet Transform for Noise Reduction in Simulated PET Images
Introduction: An efficient method of tomographic imaging in nuclear medicine is positron emission tomography (PET). Compared to SPECT, PET has the advantages of higher levels of sensitivity, spatial resolution and more accurate quantification. However, high noise levels in the image limit its diagnostic utility. Noise removal in nuclear medicine is traditionally based on Fourier decomposition o...
[ 5 ] - Cellular S-value of beta emitter radionuclide’s determined using Geant4 Monte Carlo toolbox, comparison to MIRD S-values
Introduction: Spatial dose distribution around the radionuclides sources is required for optimized treatment planning in radioimmunotherapy. At present, the main source of data for cellular dosimetry is the s-values provided by MIRD. However, the MIRD s-values have been calculated based on analytical formula in which no electrons straggling is taken to account. In this study, we used Geant4-DNA...
[ 6 ] - Preparation and biodistribution study of 99mTc-EC-Annexin-SPIO as a tracer of radiation induced apoptosis in mice model
Introduction: Apoptosis is a major consequence of ionizing radiation in proliferative tissues and quantification of the apoptotic cells could be helpful for noninvasive assessment and estimation of the radiation absorbed dose. Annexin V conjugated with super paramagnetic iron oxide nanoparticles (ANX-SPIO) is a biological probe for detection of apoptotic cells using magnetic resonance imaging. ...
[ 7 ] - A model based, anatomy dependent method for ultra-fast creation of primary SPECT projections
Introduction: Monte Carlo (MC) is the most common method for simulating virtual SPECT projections. It is useful for optimizing procedures, evaluating correction algorithms and more recently image reconstruction as a forward projector in iterative algorithms; however, the main drawback of MC is its long run time. We introduced a model based method considering the eff...
[ 8 ] - Reducing the respiratory motion artifacts in PET cardiology: A simulation study
Introduction: There are several technical features that make PET an ideal device for the noninvasive evaluation of cardiac physiology. Organ motion due to respiration is a major challenge in diagnostic imaging, especially in cardiac PET imaging. These motions reduce image quality by spreading the radiotracer activity over an increased volume, distorting apparent les...
[ 9 ] - Energy window setting for optimum Tl-201 cardiac imaging [Persian]
Introduction: Poor sensitivity and poor signal to noise ratio because of low injected thallium dose and presence of scattered photons are the main problems in using thallium in scintigraphic imaging of the heart. Scattered photons are the main cause of degrading the contrast and resolution in SPECT imaging that result in error in quantification. Thallium decay is ve...
[ 10 ] - Qualitative evaluation of filter function in brain SPECT [Persian]
Introduction: Filtering can greatly affect the quality of clinical images. Determining the best filter and the proper degree of smoothing can help to ensure the most accurate diagnosis. Methods: Forty five patient’s data aquired during brain phantom SPECT studies were reconstructed using filtered back-projection technique. The ramp, Shepp-Logan, Cosine, Hamming, Hanning, Butterworth, Metz...
[ 11 ] - Comparison of 6 PET scanners, a simulation study [Persian]
Introduction: Due to the large number of PET systems available in the market, it is not very easy to decide about the scanner of choice. Conducting a research in order to compare all different PET scanners is very time consuming and expensive and practically impossible. However, such comparison may be conducted using PET simulators. In this study, the performance of 6 different PET scanne...
[ 12 ] - Attenuation correction in myocardial perfusion SPECT using sequential transmission - emission scanning with 99mTc [Persain]
Introduction: Nowadays, Imaging of the myocardial perfusion (MPI) using the single photon emission tomography (SPET) in the diagnosis of coronary artery disease, especially myocardial ischemia, is of great importance. In contrast to the coronary artery angiography, MPI is non-invasive, less expensive and more physiological. Unfortunately, this image is affected by the some artifacts. Thes...
[ 13 ] - Feasibility of using statistical tests in evaluation of non-uniformity [Persian]
Introduction: Non-uniformity test is essentially the only required daily QC procedure in nuclear medicine practice. Noise creates statistical variation or random error in a flood image. Non-uniformity on the other hand does not have statistical nature and may be regarded as systemic error. The present methods of non-uniformity calculation do not distinguish between these two types of erro...
[ 14 ] - Comparison of acceptance tests for SPECT systems in Tehran [Persian]
Introduction: Acceptance test is a necessary procedure after SPECT system installation. The goal of this test is to reveal system's present condition, to compare it with manufacturer's specifications and also as a base for later tests. Methods: This study investigated four SPECT systems in Tehran. All of the quality control tests are performed on the basis of NEMA and IAEA recommendations...
[ 15 ] - Tissue uptakes of 67Ga-bleomycin and carrier free 67Ga in fibrosarcoma-bearing mice
67Gallium-bleomycin complex (67Ga-BLM) was prepared using Thakour method. Radio-thin-layer-chromatography of prepared complex showed A2 and B2 radiopeaks with Rf at 0.7 and 0.4 respectively with a purity of above % 95. Tissue uptake of 67Ga-BLM and 67GaCl3 in twelve tissues including tumor, blood, liver, lung, spleen, muscle, skin, heart, kidney, colon, colon content ,bladder and the tota...
[ 16 ] - Assessment of deconvolution technique for diagnosis of hydronephrosis in infants (under 6 months) [persian]
Introduction: Hydronephrosis is one of the major causes of referring infants for nuclear medicine investigation. Renal dynamic study is the most reliable investigation for such children. However direct evaluation of renogram leads to generation of parameters that have no physiological interpretation. The configuration of renogram is very much dependent upon the rate at which radiopharmace...
[ 17 ] - A camera based calculation of 99mTc-MAG3 clearance using conjugate views method [Persian]
Background: Measurement of absolute or differential renal function using radiotracers plays an important role in the clinical management of various renal diseases. Gamma camera quantitative methods in approximation of renal clearance may potentially be as accurate as plasma clearance methods. However some critical factors such as kidney depth and background counts are still troublesome in...
[ 18 ] - Appropriate energy window width for gamma camera [Persian]
Introduction: Scatter radiation is one of the major sources of error in nuclear medicine data processing. Different methods of scatter correction have been introduced in order to improve the quality of data. However the best method is to avoid recording of scatter photons in acquisition. The only difference between scattered and non-scattered photons is the energy. Pulse height analyzer i...
[ 19 ] - Calculation of 99mTc-DTPA transit times in normal kidney [Persian]
Introduction: Renal dynamic study is a well-established and popular test in routine practice of nuclear medicine. The test is non-invasive, rapid and unique in evaluation of the kidney function. In despite of its clinical values, the parameters derived from renogram are physiologically meaningless. That is due to the fact that renogram is not the true kidney function. From mathematical po...
[ 20 ] - Filter selection for 99mTc-Sestamibi myocardial perfusion SPECT imaging [Persian]
Myocardial perfusion SPECT imaging with Tc99m-sestamibi is the most accurate non-invasive means of detecting coronary artery disease and assessing the severity of perfusion abnormalities in the patients with coronary stenosis. Though simple and straight forward the results produced by the technique is very much affected by the details being used. One of the main problems with the test, wh...
[ 21 ] - بررسی تاثیر محل تجمع اکتیویته در بیماران درمان شده با رادیوداروی ید-131بر اکسپوژر محاسبه شده در فواصل مختلف از بیمار با استفاده از فانتوم NCAT
مقدمه: یکی از معمول ترین موارد استفاده از ایزوتوپ های پزشکی، درمان سرطان و پرکاری تیروئید با استفاده از ید-131 است. ید-131 در سلول های سرطانی تجمع کرده و واپاشی میکند. بدیهی است که در این روش درمانی، توزیع مکانی و زمانی ماده رادیو اکتیو در بدن به صورت محسوسی می تواند متفاوت باشد. هدف از این مطالعه بررسی تاثیر بالقوه نحوه توزیع ید رادیو اکتیو در بدن بر میزان اکسپوژر محاسبه شده در فوا...
[ 22 ] - ارزیابی کولیماتورهای لایهای در تصویربرداری تابش ترمزی حین رادیو دارو درمانی با فسفر-32
Background and purpose: Imaging which is used in nuclear medicine is done using emit gamma rays whereas therapy in nuclear medicine is performed by applying radionuclide’s which emit beta radiation. Using Bremsstrahlung is a new field which is recently introduced in imaging. In the Bremsstrahlung imaging, collimator design should not be based on energy peak and whole energy spectrum should be c...
[ 23 ] - SPIO-Annexin V, a potential probe for MRI detection of radiation induced apoptosis
Background: Finding a suitable method for rapid, accurate and reliable estimation of absorbed dose has high priority in management of the radiation exposed persons. Shortly after radiation exposure, apoptosis is a major detriment in proliferative tissues such as the hematopoietic system. Therefore, quantification of apoptosis in these tissues could be useful for rapid estimation of radiation ex...
[ 24 ] - A New Approach for Quantitative Evaluation of Reconstruction Algorithms in SPECT
ABTRACT Background: In nuclear medicine, phantoms are mainly used to evaluate the overall performance of the imaging systems and practically there is no phantom exclusively designed for the evaluation of the software performance. In this study the Hoffman brain phantom was used for quantitative evaluation of reconstruction techniques. The phantom is modified to acquire t...
[ 25 ] - A Microdosimetry model of kidney for nephrotoxicity due to internal radiation therapy
Introduction: We describe a nephron-based dosimetry model for renal toxicity for radiopharmaceutical therapy suited to the nonuniform activity distribution of radiopharmaceutical. In radiopharmaceutical therapy, renal toxicity is observed while whole-kidney and renal cortex absorbed dose values are below toxicity thresholds established by external beam and targeted radiope ptid...
[ 26 ] - Radiolabeling and Biodistribution of new dual modality nanoparticle probe in Nuclear Medicine
Introduction: Dual-modality contrast agents, such as radiolabeled nanoparticles, are promising candidates for a number of diagnostic applications, namely SPECT imaging with MR imaging. So the aim of study was evaluating potential of Chitosan-Coated Magnetic Nanoparticles(SPION) labeled with 99mTc as new Dual-modality probes for liver Imaging. Materials and Methods:</st...
[ 27 ] - Cellular dosimetry of beta emitting radionuclides-antibody conjugates for radioimmunotherapy
Introduction: The choice of optimal radionuclides for radioimmunotherapy depends on several factors, especially the radionuclide and antibody. The dosimetric characteristics of a non-internalizing and an internalizing monoclonal antibody (MAb) labeled with beta emitting radionuclides were investigated. Methods: Using Geant4-DNA Monte Carlo simulation, we ...
[ 28 ] - Bremsstrahlung imaging from the liver using the Monte Carlo simulation
Introduction: Most beta and gamma radiation radioisotopes used for treatment are not suitable for imaging. The bremsstrahlung images on a conventional gamma camera helped to localize the radionuclide within and outside of the lesion. Secondary scattering of gamma rays of higher energy and bremsstrahlung causes contamination in the energy window and reducing the contrast and resolution of the im...
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