ربیع مهدوی
فیزیک پزشکی، دانشکده پزشکی، دانشگاه علوم پزشکی ایران، ،تهران
[ 1 ] - بررسی شبیه سازی اثرات هایپرترمیای ناشی از کاربرد نانوذرات مغناطیسی بربافت همگن واقع در میدان مغناطیسی خارجی
چکیدهدر مطالعات کلینیکی , مشخص کردن توزیع دما درون بافت سالم و نیز بافت تومورال در طی درمان هایپرترمیا دشوار است. از آن جایی که باحس گر های مرسوم دما تنها در تعداد محدودی مکان اندازه گیری می شود مطالعات شبیه سازی کمک می کند که پزشکان به درک بهتری از این روش درمانی دست پیدا کنند. در این مطالعه، سه مدل تومور دو بعدی بر اساس تصاویر توزیع های نانو ذره در تومورهای PC3، DU145 وLAPC4 در محیط COM...
[ 2 ] - The Effect of Breast Reconstruction Prosthesis on Photon Dose Distribution in Breast Cancer Radiotherapy
Introduction: Siliconeprosthetic implants are commonlyutilizedfor tissue replacement and breast augmentation after mastectomy. On the other hand, some patients require adjuvant radiotherapy in order to preventlocal-regional recurrence and increment ofthe overall survival. In case of recurrence, the radiation oncologist might have to irradiate the prosthesis.The aim of this study was to evaluate...
[ 3 ] - Size Effects of Gold and Iron Nanoparticles on Radiation Dose Enhancement in Brachytherapy and Teletherapy: A Monte Carlo Study
Introduction In this study, we aimed to calculate dose enhancement factor (DEF) for gold (Au) and iron (Fe) nanoparticles (NPs) in brachytherapy and teletherapy, using Monte Carlo (MC) method. Materials and Methods In this study, a new algorithm was introduced to calculate dose enhancement by AuNPs and FeNPs for Iridium-192 (Ir-192) brachytherapy and Cobalt-60 (Co-60) teletherapy sources, using...
[ 4 ] - Physical Properties of Ethyl Methacrylate as a Bolus in Radiotherapy
Introduction Bolus is a soft and resilient material which is used for increasing skin dose or to even out the irregular patient contour. The main property of various materials used presently as bolus is the water-equivalent electron density. Ethyl methacrylate is used as a soft-liner in dentistry and its physical and chemical properties are proved to be nontoxic for human body. The goal of this...
[ 5 ] - The Role of MRSI in Target Volume Definition for Radiation Therapy of Prostate Cancer
Introduction: Recently, magnetic resonance spectroscopic imaging (MRSI), as a functional imaging method, has been used for clinical target volume definition. In this study, we used this method to define the target volume in prostate radiotherapy. Material and Method: In this study, we used images of 20 prostate cancer cases. MRSI and MRI images were fused with CT images. Then, treatment plannin...
[ 6 ] - The influence of using different reconstruction algorithms on sensitivity of quantitative 18F-FDG-PET volumetric measures to background activity variation
Introduction: This study aims to investigate the influence of background activity variation on image quantification in differently reconstructed PET/CT images. Methods: Measurements were performed on a Discovery-690 PET/CT scanner using a custom-built NEMA-like phantom. A background activity level of 5.3 and 2.6 kBq/ml 18F-FDG were applied. Ima...
[ 7 ] - مروری بر تکنیک هادرون درمانی
Despite major progress in radiotherapy, exponential attenuation of initial photons due to the nature of their interaction with matter has remained as the most important challenge. Photons have no well-defined range and their doses are reduced exponentially. Therefore, tissues located before and after the tumors receive a significant dose. Today, new techniques based on proton and carbon charged...
[ 8 ] - Development of an Advanced Optical Coherence Tomography System for Radiation Dosimetry
Introduction: According to the literature, optical coherence tomography (OCT) can be used measure radiation absorbed dose. This study was carried out to design a computed tomography system for the calculation of absorbed dose and optimization of dose delivery in radiotherapy using gel dosimeters. Material and Methods: An advanced charge-coupled device based OCT system was developed in laborator...
[ 9 ] - Cancer Risk Assessment due to Accidental Exposure inside Neutron Laboratories using BEIR VII Model
Introduction: Environmental and occupational human exposure from neutron source can lead to the serious biologic effects. The aim of this study is to evaluate the cancer incidence risk for various human organs at different neutron dose levels due to exposure from an Americium-241/Beryllium (Am-241/Be), a standard neutron source for calibration purposes. Material and Methods: We measured ambient...
[ 10 ] - Megavoltage X-ray Dose Enhancement with Gold Nanoparticles in Tumor Bearing Mice
One of the applications of gold nanoparticles (GNPs) in medicine is radiation dose-enhancing effect. Although there are many simulations, in vitro and in vivo evidence that GNPs can enhance significantly the radiation dose effect of orthovoltage beams. These beams compared with megavoltage (MV) beams, have limited applications in radiotherapy. In order to evaluate GNPs radiosensitization perfor...
[ 11 ] - Optimization of clinical target volume delineation using magnetic resonance spectroscopic imaging (MRSI) in 3D conformal radiotherapy of prostate cancer
Background: For the purpose of individual clinical target volume assessment in radiotherapy of prostate cancer, MRSI was used as a molecular imaging modality with MRI and CT images. Materials and Methods: The images of 20 prostate cancer patients were used in this study. The MR and MRSI images were registered with CT ones using non-rigid registration technique. The CT based planning (BP), CT/MR...
[ 12 ] - Monte Carlo study on beam hardening effect of physical wedges
Background: Physical wedges are still widely used as beam modifiers in external beam radiotherapy. However the presence of them in the beam trace may cause beam hardening which may not be considered in many treatment planning systems. The aim of this study is to investigate the beam hardening effect generated by physical wedges via different beam quality indexes as photon spectrum, half value l...
[ 13 ] - Megavoltage dose enhancement of gold nanoparticles for different geometric set-ups: Measurements and Monte Carlo simulation
Background: Gold nanoparticles (GNPs) have been shown as a good radiosensitizer. In combination with radiotherapy, several studies with orthovoltage X-rays have shown considerable dose enhancement effects. This paper reports the dose enhancement factor (DEF) due to GNPs in 18 megavoltage (MV) beams. Materials and Methods: Different geometrical 50-nm GNPs configurations at a concentrati...
[ 14 ] - Chronological response of prostacyclin changes to moderately low doses of radiation in Rat cervical spinal cord
Background: Study of vascular and its secretory profile changes is an important issue in pathogenesis of radiation myelopathy. This paper reports the prostacyclin concentration changes after low-moderate doses of X-irradiation within a short period of time. Materials and Methods: Cervical cords of Wistar rats were irradiated to doses of 0.5, 1, 2, 4 and 6 Gy X-rays. After 24 hours, 2 and 13 ...
[ 15 ] - ارزیابی سطح دوز مرجع تشخیصی ناشی از آزمایشات سی‌تی‌اسکن در گروه سنی بزرگ‌سالان در تهران: گزارش کوتاه
Background: Today, a CT scan examination play an important role in disease diagnosis and thus allocates a significant dose of medical X-ray examinations. One of the important principles in the use of ionizing radiations is to observe radiation protection principles. Evaluating patient's absorbed dose and implementing the strategies for reducing dose are prior in safety issues. To achieve this p...
[ 16 ] - Siemens primus accelerator simulation using EGSnrc Monte Carlo code and gel dosimetry validation with optical computed tomography system by EGSnrc code
Monte Carlo method is the most accurate method for simulation of radiation therapy equipment. The linear accelerators (linac) are currently the most widely used machines in radiation therapy centers. Monte Carlo modeling of the Siemens Primus linear accelerator in 6 MeV beams was used. Square field size of 10 × 10 cm2 produced by the jaws was compared with TLD. Head simulation of Siemens accele...
[ 17 ] - Estimation of diagnostic reference levels for children computed tomography: A study in Tehran, Iran
Background: The Diagnostic reference levels (DRLs) play a critical role in the optimization of radiation dose especially, in some conditions like pediatrics. They are useful indicators by which the radiologists can be aware of delivered excess radiation doses to the patients, and take corrective actions if necessary. In order to meet some requirements for establishing the national computed tomo...
[ 18 ] - Physical and Dosimetric Aspect of Euromechanics Add-on Multileaf Collimator on Varian Clinac 2100 C/D
Background:Â Before treatment planning and dose delivery, quality assurance of multi-leaf collimator (MLC) has an important role in intensity-modulated radiation therapy (IMRT) due to the creation of multiple segments from optimization process.Objective: The purpose of this study is to assess the quality control of MLC leaves using EBT3 Gafchromic films.Material and Methods: Leaf Position accur...
[ 19 ] - Estimation of Dosimetric Parameters based on KNR and KNCSF Correction Factors for Small Field Radiation Therapy at 6 and 18 MV Linac Energies using Monte Carlo Simulation Methods
Background: Estimating dosimetric parameters for small fields under non-reference conditions leads to significant errors if done based on conventional protocols used for large fields in reference conditions. Hence, further correction factors have been introduced to take into account the influence of spectral quality changes when various detectors are used in non-reference conditions at differen...
[ 20 ] - Monte Carlo Simulation of Electron Beams produced by LIAC Intraoperative Radiation Therapy Accelerator
Background: One of the main problems of dedicated IORT accelerators is to determine dosimetric characteristics of the electron beams. Monte Carlo simulation of IORT accelerator head and produced beam will be useful to improve the accuracy of beam dosimetry.Materials and Methods: Liac accelerator head was modeled using the BEAMnrcMonte Carlo simulation system. Phase-space files were generated at...
[ 21 ] - Studying Effects of Gold Nanoparticle on Dose Enhancement in Megavoltage Radiation
Background: Gold nanoparticles are emerging as promising agents for cancer therapy and are being investigated as drug carriers, photothermal agents, contrast agents and radiosensitisers.Objective: The aim of this study is to understand characteristics of secondary electrons generated from interaction of gold nanoparticles GNPs with x-rays as a function of nanoparticle size and beam energy and ...
[ 22 ] - Effect of Gold Nanoparticles on Prostate Dose Distribution under Ir-192 Internal and 18 MV External Radiotherapy Procedures Using Gel Dosimetry and Monte Carlo Method
Background: Gel polymers are considered as new dosimeters for determining radiotherapy dose distribution in three dimensions.Objective: The ability of a new formulation of MAGIC-f polymer gel was assessed by experimental measurement and Monte Carlo (MC) method for studying the effect of gold nanoparticles (GNPs) in prostate dose distributions under the internal Ir-192 and external 18MV radiothe...
[ 23 ] - Comparison of the presence and non-presence states of magnetite nanoparticles in tissue-equivalent breast phantom via radiofrequency hyperthermia
Objective(s): Breast cancer is a fatal disease and the leading cause of mortality in women. Radiofrequency hyperthermia is an approach to the treatment of cancer cells through increasing their temperature. The present study aimed to investigate breast tumor ablation via radiofrequency hyperthermia in the presence and non-presence states of magnetite nanoparticles and assess the effects of magne...
[ 24 ] - A Review on the Application of 3D Printing Technology in Radiotherapy for Breast Cancer
Breast cancer is considered as one of the main causes of cancer death in women. Early diagnosis and treatment, especially by modern technologies play major roles in management of breast cancer. Radiation therapy is known as one of the main treatment options for breast cancer. Nowadays, 3D printing technology is also used to rapidly construct objects with high quality. Many studies have shown th...
[ 25 ] - Determination of the absorbent dose increase factor for different concentrations of gold nanoparticles using a dosimetry gel
with the advancement of nanotechnology, high-atomic materials such as gold nanoparticles can be used to increase the amount of absorbed doses and use this property to eliminate cancer cells. In this study, the dose enhancement factor (DEF) derived from different concentrations of gold nanoparticles was calculated to show an increase in absorbed dose from gold nanoparticles. At first, a tissue e...
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