I Work as an associate professor in the field of Medical Physics at Tarbiat Modares University in Tehran, Iran.
My teaching and research interests are focused mainly on the Physics of Radiology and Radiotherapy namely on the development of radiological and radiotheraputical practices based on their underlying principles of physics such as Radiation Dosimetry, Monte Carlo and Finite Element Simulation, ... .
Journal of Mazandaran University of Medical Sciences, 2016
Background and purpose: The human body is composed of various inhomogenous tissues with a variety... more Background and purpose: The human body is composed of various inhomogenous tissues with a variety of physical and radiological properties. These inhomogeneities could change isodose distributions, increase the probability of geometric errors, and eventually lead to missing of the target irradiation or incorrect isodose coverage in conformal radiation therapy (CRT) due to the uncertainties resulted from the effect of such inhomogeneties on isodose curves. In this study, the effect of inhomogeneities on dosimetric accuracy of the CRT of prostate was investigated using Monte Carlo simulation method. Materials and methods: An anthropomorphic pelvis phantom was used in two modes representing a homogeneous and heterogeneous phantom. Three dimensional (3D) CRT planning composed of five fields were performed on the CT images of the phantoms using the CorPLAN treatment planning system (TPS) of a 2100C/D Varian linac. Delivery of 3DCRT was also simulated by EGSnrc Monte Carlo code for the sam...
2023 IEEE Nuclear Science Symposium, Medical Imaging Conference and International Symposium on Room-Temperature Semiconductor Detectors (NSS MIC RTSD), Nov 3, 2023
Radiation-induced hemorrhagic cystitis (RIHC) is a common side effect in prostate cancer patients... more Radiation-induced hemorrhagic cystitis (RIHC) is a common side effect in prostate cancer patients. In this study, we aim to investigate the feasibility of using radiomics and dosiomics from CT and 3D Dose distribution data to predict RIHC in patients with prostate cancer undergoing pelvic radiation therapy. We used 59 patients with CT and Dose images and follow-up. First, radiomic and dosimic features were extracted from the bladder. Following, we proceeded with various feature selection (FS) and classifier algorithms on the training dataset and evaluated on test dataset with Specificity (SPE), Sensitivity (SEN), and Balance Accuracy (BAC) metrics. For CT radiomic features, the Boruta+XGB model performed best with BAC=0.75, SEN=0.80, and SPE=0.70; while in the Dose dataset, the RFE+DT model had the highest performance with BAC=0.71, SEN=0.85, and SPE=0.57. Finally, by combining CT and Dose datasets, we obtained BAC=0.67, SEN=0.6, and SPE=0.75. The findings of our study suggest the potential for using radiomic and dosomic features could predict acute RIHC in prostate cancer patients.
Introduction: After surgery, radiotherapy is the most common technique to treat breast cancer. Ov... more Introduction: After surgery, radiotherapy is the most common technique to treat breast cancer. Over the past decades, the thermal effects of radiofrequency-wave hyperthermia combined with radiotherapy have been used to increase radiosensitivity in cancer treatment. The cells have various radiation and thermal sensitivities at different stages of the mitotic cycle. Furthermore, ionizing radiation and the thermal effect of hyperthermia affect the cells' mitotic cycle and can partly induce cell cycle arrest. However, the time interval between hyperthermia and radiotherapy, as an essential factor influencing hyperthermia effect on cancer cells' cycle arrest, has not been studied before. In this study, we investigated the effect of hyperthermia on the MCF7 cancer cell cycle arrest in mitotic cycles at various selected time intervals after hyperthermia to find and propose appropriate time intervals between hyperthermia and radiotherapy. Method and Materials: In this experimental study, we used the MCF7 breast cancer cell line to investigate the effect of 13.56 MHz hyperthermia (at a temperature of 43°C for a period of 20 min) on their cell cycle arrest. We performed the flowcytometry assay to assess the changes in the mitotic phases of the cell population at different time intervals (1, 6, 24, and 48 h) after hyperthermia. Results: Our flowcytometry results indicated the 24-h time interval has the most significant effect on the cell population at S and G2/M phases. Therefore, the 24-h time interval can be proposed as the most appropriate time after hyperthermia for carrying out combinational radiotherapy procedure. Conclusion: Among various investigated time intervals examined in our research, the 24-h time interval can be proposed as the most appropriate time between hyperthermia and radiotherapy for combinational therapy of breast cancer cells. Kerwords: Radiotherapy, Hyperthermia, Gold Nanoparticles, MCF‑7 cancer cells
Although the clonogenic assay is the traditional method in determination of the response of cell ... more Although the clonogenic assay is the traditional method in determination of the response of cell lines to irradiation and in drawing the survival curves, but this method has some important defects such as the time taken to form clonies, inability to measure survival in cells which do not grow as clonies, and low sample throughput. Therefore, investigating other methods to situate this method is needed. One of the easy methods used widely in investigation of the effect of different treatments on cell lines, is the MTT assay. The MTT assay is a sensitive and accurate method and some researchers have used this method, considering its' several advantages such as relative low cost, short time to assess the samples and the possibility of acquiring the results semi-automatically. However, for this method, there are some restrictions/limitations and some important factors that should be discussed. In this paper, firstly, the standard procedure in using the clonogenic and MTT assay is described according to the standard protocols, then, different methods proposed in diverse researches in using MTT assay in calculating the cell survival instead of the clonogenic assay have been explained and compared. Jeywoeds: MTT assay, Clonogenic Aassay, Dose Response, Survival Curve
Journal of Mazandaran University of Medical Sciences, 2023
Background and purpose: Radiation therapy is one of the most important methods in treatment of ca... more Background and purpose: Radiation therapy is one of the most important methods in treatment of cancer. Targeted metal nanoparticles (NPs) play an effective role in reducing ionizing radiation side effects through increasing the effect of ionizing radiation on cancer cells and controlling the harmful effect of radiation on healthy cells. The purpose of this study was to investigate the effect of targeted folic acid gold NPs (GNPs) using linker bovine serum albumin in the absorption and sensitivity of gold NPs in HeLa cervical cancer cells compared to non-targeted gold NPs. Materials and methods: In this study, GNPs were conjugated with folic acid by bovine serum albumin as the linker. The binding of bovine serum albumin and folic acid to GNPs was investigated by infrared (IR) spectroscopy. Toxicity was measured by the MTT method and based on the results, the GNPs' non-toxic concentration was determined. The effect of targeted synthesized GNPs on their absorption and sensitivity were evaluated on HeLa cells. Results: The non-toxic concentration of GNPs was 12 μg/ml. Incubation of the cells with this concentration was performed for 2, 4, and 24 hours and it was observed that in 4 hours, the absorption rate of targeted GNPs was about 4 times higher than that of non-targeted GNPs. The radiosensitization ratios of targeted and non-targeted GNPs in the studied cancer cells relative to the control group (without NPs) exposed to 6 MV photon radiation were 1.32±0.02 and 1.19±0.02, respectively. Conclusion: The use of bovine serum albumin linker to target GNPs has a significant effect on increasing the absorption of GNPs and the effect of ionizing radiation on HeLa cells under 6 MV photon beams. Ketwords: Radiation Therpay, Radiation sentisizers, Targeted Radiotherapy, Gold Nanoparticles (GNPSs), Cervical Cancer
Journal of Mazandaran University of Medical Sciences, 2016
Background and purpose: The human body is composed of various inhomogenous tissues with a variety... more Background and purpose: The human body is composed of various inhomogenous tissues with a variety of physical and radiological properties. These inhomogeneities could change isodose distributions, increase the probability of geometric errors, and eventually lead to missing of the target irradiation or incorrect isodose coverage in conformal radiation therapy (CRT) due to the uncertainties resulted from the effect of such inhomogeneties on isodose curves. In this study, the effect of inhomogeneities on dosimetric accuracy of the CRT of prostate was investigated using Monte Carlo simulation method. Materials and methods: An anthropomorphic pelvis phantom was used in two modes representing a homogeneous and heterogeneous phantom. Three dimensional (3D) CRT planning composed of five fields were performed on the CT images of the phantoms using the CorPLAN treatment planning system (TPS) of a 2100C/D Varian linac. Delivery of 3DCRT was also simulated by EGSnrc Monte Carlo code for the same conditions used in the CorPLAN TPS. The dose distributions resulted from the MC simulations were compared with those of the CorPLAN TPS for both of the phantoms based on the "dose difference (DD) percentages" and "distance to agreement (DTA)" parameters. Results: Findings indicated that the heterogeneity leads to an overdose estimation at the target location up to 2.8% and 4.4% for the 6 and 18 MV energies, respectively by the CorPLAN TPS compared with the MC simulation data. The average DD and DTA for the homogeneous phantom were 2.7%-3.4mm and 1.6%-2.3 mm while for the inhomogeneous phantom they were 5.5%-3.7 mm and 6.0%-2.5 mm at the 6 and 18 MV energies, respectively. Conclusion: Our r esults indicates that the accuracy of the dosimetry parameters estimated by the CorPLAN TPS at 18 MV is more than that of 6 MV energy. But, the heterogeneity deteriorates more the accuracy level of such dosimetry parameters estimated by this commercial TPS at 18 MV energy.
To compare spiral computed tomography (CT) performed at increased pitch with spiral CT performed ... more To compare spiral computed tomography (CT) performed at increased pitch with spiral CT performed at standard pitch in the detection of pulmonary nodules. Spiral CT scanning of the thorax was performed with a pitch of 1.0 in 109 patients with pulmonary nodules due to metastases. The patients were also randomly assigned to undergo further scanning with a pitch of 1.2 (n = 34), 1.5 (n = 37), 2.0 (n = 38) at the same scanning session. The scan pairs were analysed for number, size, and distribution of nodules. A bias toward undercounting was noted on scans with a pitch of 1.5 and 2.0; however, this was not statistically significant. Correlation coefficients were r = .982, r = .977, and r = .989 for scans of pitch 1.2, 1.5, and 2.0, respectively. Disease in one patient would have been prospectively understaged from findings on a scan of pitch 2.0 because of poor conspicuity of a small solitary nodule. Findings from scans with increased pitch generally agree well with those from scans with standard pitch; however, there is a greater risk of understaging of disease in patients with solitary nodules as pitch increases. Pitch should be limited to no greater than 1.5 for initial staging of pulmonary metastatic disease.
Recent advances in radiation therapy have made obvious the need for dosimeters that can measure t... more Recent advances in radiation therapy have made obvious the need for dosimeters that can measure three-dimensional (3-D) dose distributions. Currently, radiosensitive gel dosimeters have provided 3-D dose measurements using the MRI technique. However, this method has some limitations. Recently, a novel transparent polymer dosimeter, PRESAGE, has been introduced which exhibits a radiochromic response when exposed to ionizing radiation. This dosimetry technique has some advantages compared with other gel dosimeters. In this study, the dose response, linearity, sensitivity, and stability of this type of dosimeter were investigated for different levels of the activator, and leuco dye concentration. In this regard, the PRESAGE dosimeters were made with different formulations and were irradiated by gamma-rays of Cobalt-60 in the dose range of 0-50 Gy. Then, the optical absorption changes of the dosimeters were measured by a spectrophotometer over a period of 14 days after the irradiation. The results indicated that increasing the activator concentration leads to the increase of the sensitivity, but decreases the stability of the dosimeter response. Furthermore, it was noted that the dosimeter shows a linear response to the radiation dose with a high level of correlation (R^2>0.99).
Journal of Mazandaran University of Medical Sciences, Jun 10, 2016
Background and purpose: The human body is composed of various inhomogenous tissues with a variety... more Background and purpose: The human body is composed of various inhomogenous tissues with a variety of physical and radiological properties. These inhomogeneities could change isodose distributions, increase the probability of geometric errors, and eventually lead to missing of the target irradiation or incorrect isodose coverage in conformal radiation therapy (CRT) due to the uncertainties resulted from the effect of such inhomogeneties on isodose curves. In this study, the effect of inhomogeneities on dosimetric accuracy of the CRT of prostate was investigated using Monte Carlo simulation method.
Materials and methods: An anthropomorphic pelvis phantom was used in two modes representing a homogeneous and heterogeneous phantom. Three dimensional (3D) CRT planning composed of five fields were performed on the CT images of the phantoms using the CorPLAN treatment planning system (TPS) of a 2100C/D Varian linac. Delivery of 3DCRT was also simulated by EGSnrc Monte Carlo code for the same conditions used in the CorPLAN TPS. The dose distributions resulted from the MC simulations were compared with those of the CorPLAN TPS for both of the phantoms based on the "dose difference (DD) percentages" and "distance to agreement (DTA)" parameters.
Results: Findings indicated that the heterogeneity leads to an overdose estimation at the target location up to 2.8% and 4.4% for the 6 and 18 MV energies, respectively by the CorPLAN TPS compared with the MC simulation data. The average DD and DTA for the homogeneous phantom were 2.7%-3.4mm and 1.6%-2.3 mm while for the inhomogeneous phantom they were 5.5%-3.7 mm and 6.0%-2.5 mm at the 6 and 18 MV energies, respectively.
Conclusion: Our results indicates that the accuracy of the dosimetry parameters estimated by the CorPLAN TPS at 18 MV is more than that of 6 MV energy. But, the heterogeneity deteriorates more the accuracy level of such dosimetry parameters estimated by this commercial TPS at 18 MV energy.
Keywords: prostate cancer, conformal radiation therapy, Monte Carlo, treatment planning system
Introduction: We aimed to investigate the effect of variation of beam angle and field of view (FO... more Introduction: We aimed to investigate the effect of variation of beam angle and field of view (FOV) on organs’ and effective doses for patients undergoing interventional cardiology examinations by using Monte Carlo simulations and ICRP110 phantom. Materials and Methods: Simulations were done for energies obtained from experimental measurements on the left ventricle phantom of the Axiom Artis model of an angiography system by Monte Carlo N- Particle System code (MCNP). The ICRP110 voxelized whole body model representing an average patient was employed at posterior anterior (PA) position. To guide the x-ray source, the approximate spherical coordinates were set at: 27, 27.135. The collimated x-rays beam was directed toward the patient's body over 16´16 and 25´25 cm2 field sizes for twenty alternative proposed techniques and their resulting effective doses were estimated and compared with those obtained for six relevant routine techniques of coronary angiography including LAO40-CAUD40, LAO45, LAO60-CRA20, PA-CRA45, RAO20-CAUD20 and RAO30, used at a hospital. Results: Variation of the angle and FOV for the 25´25 cm2 field size resulted in dose reduction for some of the proposed techniques including the LAO20-CAUD20, LAO20-CAUD45, LAO60- CAUD20, LAO60-CAUD45, LAO30, LAO60-CRA30, RAO10-CAUD30, RAO30-CAUD30, RAO20 and RAO40 with an amount of 12, 15, 27, 74, 40, 54, 50, 56, 13 and 38 percent respectively. But, for the 16´16 cm2 field size, the dose reduction was observed just for the LAO60-CRA30, RAO10-CAUD30 and RAO30-CAUD30 proposed techniques with an amount of 41, 16 and 38 percent respectively. Conclusion: By appropriate variation of the beam angle and FOV, the number/volume of the critical organs exposed directly to primary x-rays can be reduced and lead to the reduction of effective dose while keeping the target organ within the radiation field.
Journal of Mazandaran University of Medical Sciences, 2016
Background and purpose: The human body is composed of various inhomogenous tissues with a variety... more Background and purpose: The human body is composed of various inhomogenous tissues with a variety of physical and radiological properties. These inhomogeneities could change isodose distributions, increase the probability of geometric errors, and eventually lead to missing of the target irradiation or incorrect isodose coverage in conformal radiation therapy (CRT) due to the uncertainties resulted from the effect of such inhomogeneties on isodose curves. In this study, the effect of inhomogeneities on dosimetric accuracy of the CRT of prostate was investigated using Monte Carlo simulation method. Materials and methods: An anthropomorphic pelvis phantom was used in two modes representing a homogeneous and heterogeneous phantom. Three dimensional (3D) CRT planning composed of five fields were performed on the CT images of the phantoms using the CorPLAN treatment planning system (TPS) of a 2100C/D Varian linac. Delivery of 3DCRT was also simulated by EGSnrc Monte Carlo code for the sam...
2023 IEEE Nuclear Science Symposium, Medical Imaging Conference and International Symposium on Room-Temperature Semiconductor Detectors (NSS MIC RTSD), Nov 3, 2023
Radiation-induced hemorrhagic cystitis (RIHC) is a common side effect in prostate cancer patients... more Radiation-induced hemorrhagic cystitis (RIHC) is a common side effect in prostate cancer patients. In this study, we aim to investigate the feasibility of using radiomics and dosiomics from CT and 3D Dose distribution data to predict RIHC in patients with prostate cancer undergoing pelvic radiation therapy. We used 59 patients with CT and Dose images and follow-up. First, radiomic and dosimic features were extracted from the bladder. Following, we proceeded with various feature selection (FS) and classifier algorithms on the training dataset and evaluated on test dataset with Specificity (SPE), Sensitivity (SEN), and Balance Accuracy (BAC) metrics. For CT radiomic features, the Boruta+XGB model performed best with BAC=0.75, SEN=0.80, and SPE=0.70; while in the Dose dataset, the RFE+DT model had the highest performance with BAC=0.71, SEN=0.85, and SPE=0.57. Finally, by combining CT and Dose datasets, we obtained BAC=0.67, SEN=0.6, and SPE=0.75. The findings of our study suggest the potential for using radiomic and dosomic features could predict acute RIHC in prostate cancer patients.
Introduction: After surgery, radiotherapy is the most common technique to treat breast cancer. Ov... more Introduction: After surgery, radiotherapy is the most common technique to treat breast cancer. Over the past decades, the thermal effects of radiofrequency-wave hyperthermia combined with radiotherapy have been used to increase radiosensitivity in cancer treatment. The cells have various radiation and thermal sensitivities at different stages of the mitotic cycle. Furthermore, ionizing radiation and the thermal effect of hyperthermia affect the cells' mitotic cycle and can partly induce cell cycle arrest. However, the time interval between hyperthermia and radiotherapy, as an essential factor influencing hyperthermia effect on cancer cells' cycle arrest, has not been studied before. In this study, we investigated the effect of hyperthermia on the MCF7 cancer cell cycle arrest in mitotic cycles at various selected time intervals after hyperthermia to find and propose appropriate time intervals between hyperthermia and radiotherapy. Method and Materials: In this experimental study, we used the MCF7 breast cancer cell line to investigate the effect of 13.56 MHz hyperthermia (at a temperature of 43°C for a period of 20 min) on their cell cycle arrest. We performed the flowcytometry assay to assess the changes in the mitotic phases of the cell population at different time intervals (1, 6, 24, and 48 h) after hyperthermia. Results: Our flowcytometry results indicated the 24-h time interval has the most significant effect on the cell population at S and G2/M phases. Therefore, the 24-h time interval can be proposed as the most appropriate time after hyperthermia for carrying out combinational radiotherapy procedure. Conclusion: Among various investigated time intervals examined in our research, the 24-h time interval can be proposed as the most appropriate time between hyperthermia and radiotherapy for combinational therapy of breast cancer cells. Kerwords: Radiotherapy, Hyperthermia, Gold Nanoparticles, MCF‑7 cancer cells
Although the clonogenic assay is the traditional method in determination of the response of cell ... more Although the clonogenic assay is the traditional method in determination of the response of cell lines to irradiation and in drawing the survival curves, but this method has some important defects such as the time taken to form clonies, inability to measure survival in cells which do not grow as clonies, and low sample throughput. Therefore, investigating other methods to situate this method is needed. One of the easy methods used widely in investigation of the effect of different treatments on cell lines, is the MTT assay. The MTT assay is a sensitive and accurate method and some researchers have used this method, considering its' several advantages such as relative low cost, short time to assess the samples and the possibility of acquiring the results semi-automatically. However, for this method, there are some restrictions/limitations and some important factors that should be discussed. In this paper, firstly, the standard procedure in using the clonogenic and MTT assay is described according to the standard protocols, then, different methods proposed in diverse researches in using MTT assay in calculating the cell survival instead of the clonogenic assay have been explained and compared. Jeywoeds: MTT assay, Clonogenic Aassay, Dose Response, Survival Curve
Journal of Mazandaran University of Medical Sciences, 2023
Background and purpose: Radiation therapy is one of the most important methods in treatment of ca... more Background and purpose: Radiation therapy is one of the most important methods in treatment of cancer. Targeted metal nanoparticles (NPs) play an effective role in reducing ionizing radiation side effects through increasing the effect of ionizing radiation on cancer cells and controlling the harmful effect of radiation on healthy cells. The purpose of this study was to investigate the effect of targeted folic acid gold NPs (GNPs) using linker bovine serum albumin in the absorption and sensitivity of gold NPs in HeLa cervical cancer cells compared to non-targeted gold NPs. Materials and methods: In this study, GNPs were conjugated with folic acid by bovine serum albumin as the linker. The binding of bovine serum albumin and folic acid to GNPs was investigated by infrared (IR) spectroscopy. Toxicity was measured by the MTT method and based on the results, the GNPs' non-toxic concentration was determined. The effect of targeted synthesized GNPs on their absorption and sensitivity were evaluated on HeLa cells. Results: The non-toxic concentration of GNPs was 12 μg/ml. Incubation of the cells with this concentration was performed for 2, 4, and 24 hours and it was observed that in 4 hours, the absorption rate of targeted GNPs was about 4 times higher than that of non-targeted GNPs. The radiosensitization ratios of targeted and non-targeted GNPs in the studied cancer cells relative to the control group (without NPs) exposed to 6 MV photon radiation were 1.32±0.02 and 1.19±0.02, respectively. Conclusion: The use of bovine serum albumin linker to target GNPs has a significant effect on increasing the absorption of GNPs and the effect of ionizing radiation on HeLa cells under 6 MV photon beams. Ketwords: Radiation Therpay, Radiation sentisizers, Targeted Radiotherapy, Gold Nanoparticles (GNPSs), Cervical Cancer
Journal of Mazandaran University of Medical Sciences, 2016
Background and purpose: The human body is composed of various inhomogenous tissues with a variety... more Background and purpose: The human body is composed of various inhomogenous tissues with a variety of physical and radiological properties. These inhomogeneities could change isodose distributions, increase the probability of geometric errors, and eventually lead to missing of the target irradiation or incorrect isodose coverage in conformal radiation therapy (CRT) due to the uncertainties resulted from the effect of such inhomogeneties on isodose curves. In this study, the effect of inhomogeneities on dosimetric accuracy of the CRT of prostate was investigated using Monte Carlo simulation method. Materials and methods: An anthropomorphic pelvis phantom was used in two modes representing a homogeneous and heterogeneous phantom. Three dimensional (3D) CRT planning composed of five fields were performed on the CT images of the phantoms using the CorPLAN treatment planning system (TPS) of a 2100C/D Varian linac. Delivery of 3DCRT was also simulated by EGSnrc Monte Carlo code for the same conditions used in the CorPLAN TPS. The dose distributions resulted from the MC simulations were compared with those of the CorPLAN TPS for both of the phantoms based on the "dose difference (DD) percentages" and "distance to agreement (DTA)" parameters. Results: Findings indicated that the heterogeneity leads to an overdose estimation at the target location up to 2.8% and 4.4% for the 6 and 18 MV energies, respectively by the CorPLAN TPS compared with the MC simulation data. The average DD and DTA for the homogeneous phantom were 2.7%-3.4mm and 1.6%-2.3 mm while for the inhomogeneous phantom they were 5.5%-3.7 mm and 6.0%-2.5 mm at the 6 and 18 MV energies, respectively. Conclusion: Our r esults indicates that the accuracy of the dosimetry parameters estimated by the CorPLAN TPS at 18 MV is more than that of 6 MV energy. But, the heterogeneity deteriorates more the accuracy level of such dosimetry parameters estimated by this commercial TPS at 18 MV energy.
To compare spiral computed tomography (CT) performed at increased pitch with spiral CT performed ... more To compare spiral computed tomography (CT) performed at increased pitch with spiral CT performed at standard pitch in the detection of pulmonary nodules. Spiral CT scanning of the thorax was performed with a pitch of 1.0 in 109 patients with pulmonary nodules due to metastases. The patients were also randomly assigned to undergo further scanning with a pitch of 1.2 (n = 34), 1.5 (n = 37), 2.0 (n = 38) at the same scanning session. The scan pairs were analysed for number, size, and distribution of nodules. A bias toward undercounting was noted on scans with a pitch of 1.5 and 2.0; however, this was not statistically significant. Correlation coefficients were r = .982, r = .977, and r = .989 for scans of pitch 1.2, 1.5, and 2.0, respectively. Disease in one patient would have been prospectively understaged from findings on a scan of pitch 2.0 because of poor conspicuity of a small solitary nodule. Findings from scans with increased pitch generally agree well with those from scans with standard pitch; however, there is a greater risk of understaging of disease in patients with solitary nodules as pitch increases. Pitch should be limited to no greater than 1.5 for initial staging of pulmonary metastatic disease.
Recent advances in radiation therapy have made obvious the need for dosimeters that can measure t... more Recent advances in radiation therapy have made obvious the need for dosimeters that can measure three-dimensional (3-D) dose distributions. Currently, radiosensitive gel dosimeters have provided 3-D dose measurements using the MRI technique. However, this method has some limitations. Recently, a novel transparent polymer dosimeter, PRESAGE, has been introduced which exhibits a radiochromic response when exposed to ionizing radiation. This dosimetry technique has some advantages compared with other gel dosimeters. In this study, the dose response, linearity, sensitivity, and stability of this type of dosimeter were investigated for different levels of the activator, and leuco dye concentration. In this regard, the PRESAGE dosimeters were made with different formulations and were irradiated by gamma-rays of Cobalt-60 in the dose range of 0-50 Gy. Then, the optical absorption changes of the dosimeters were measured by a spectrophotometer over a period of 14 days after the irradiation. The results indicated that increasing the activator concentration leads to the increase of the sensitivity, but decreases the stability of the dosimeter response. Furthermore, it was noted that the dosimeter shows a linear response to the radiation dose with a high level of correlation (R^2>0.99).
Journal of Mazandaran University of Medical Sciences, Jun 10, 2016
Background and purpose: The human body is composed of various inhomogenous tissues with a variety... more Background and purpose: The human body is composed of various inhomogenous tissues with a variety of physical and radiological properties. These inhomogeneities could change isodose distributions, increase the probability of geometric errors, and eventually lead to missing of the target irradiation or incorrect isodose coverage in conformal radiation therapy (CRT) due to the uncertainties resulted from the effect of such inhomogeneties on isodose curves. In this study, the effect of inhomogeneities on dosimetric accuracy of the CRT of prostate was investigated using Monte Carlo simulation method.
Materials and methods: An anthropomorphic pelvis phantom was used in two modes representing a homogeneous and heterogeneous phantom. Three dimensional (3D) CRT planning composed of five fields were performed on the CT images of the phantoms using the CorPLAN treatment planning system (TPS) of a 2100C/D Varian linac. Delivery of 3DCRT was also simulated by EGSnrc Monte Carlo code for the same conditions used in the CorPLAN TPS. The dose distributions resulted from the MC simulations were compared with those of the CorPLAN TPS for both of the phantoms based on the "dose difference (DD) percentages" and "distance to agreement (DTA)" parameters.
Results: Findings indicated that the heterogeneity leads to an overdose estimation at the target location up to 2.8% and 4.4% for the 6 and 18 MV energies, respectively by the CorPLAN TPS compared with the MC simulation data. The average DD and DTA for the homogeneous phantom were 2.7%-3.4mm and 1.6%-2.3 mm while for the inhomogeneous phantom they were 5.5%-3.7 mm and 6.0%-2.5 mm at the 6 and 18 MV energies, respectively.
Conclusion: Our results indicates that the accuracy of the dosimetry parameters estimated by the CorPLAN TPS at 18 MV is more than that of 6 MV energy. But, the heterogeneity deteriorates more the accuracy level of such dosimetry parameters estimated by this commercial TPS at 18 MV energy.
Keywords: prostate cancer, conformal radiation therapy, Monte Carlo, treatment planning system
Introduction: We aimed to investigate the effect of variation of beam angle and field of view (FO... more Introduction: We aimed to investigate the effect of variation of beam angle and field of view (FOV) on organs’ and effective doses for patients undergoing interventional cardiology examinations by using Monte Carlo simulations and ICRP110 phantom. Materials and Methods: Simulations were done for energies obtained from experimental measurements on the left ventricle phantom of the Axiom Artis model of an angiography system by Monte Carlo N- Particle System code (MCNP). The ICRP110 voxelized whole body model representing an average patient was employed at posterior anterior (PA) position. To guide the x-ray source, the approximate spherical coordinates were set at: 27, 27.135. The collimated x-rays beam was directed toward the patient's body over 16´16 and 25´25 cm2 field sizes for twenty alternative proposed techniques and their resulting effective doses were estimated and compared with those obtained for six relevant routine techniques of coronary angiography including LAO40-CAUD40, LAO45, LAO60-CRA20, PA-CRA45, RAO20-CAUD20 and RAO30, used at a hospital. Results: Variation of the angle and FOV for the 25´25 cm2 field size resulted in dose reduction for some of the proposed techniques including the LAO20-CAUD20, LAO20-CAUD45, LAO60- CAUD20, LAO60-CAUD45, LAO30, LAO60-CRA30, RAO10-CAUD30, RAO30-CAUD30, RAO20 and RAO40 with an amount of 12, 15, 27, 74, 40, 54, 50, 56, 13 and 38 percent respectively. But, for the 16´16 cm2 field size, the dose reduction was observed just for the LAO60-CRA30, RAO10-CAUD30 and RAO30-CAUD30 proposed techniques with an amount of 41, 16 and 38 percent respectively. Conclusion: By appropriate variation of the beam angle and FOV, the number/volume of the critical organs exposed directly to primary x-rays can be reduced and lead to the reduction of effective dose while keeping the target organ within the radiation field.
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Teaching Documents by Bijan Hashemi
Papers by Bijan Hashemi
Method and Materials: In this experimental study, we used the MCF7 breast cancer cell line to investigate the effect of 13.56 MHz hyperthermia (at a temperature of 43°C for a period of 20 min) on their cell cycle arrest. We performed the flowcytometry assay to assess the changes in the mitotic phases of the cell population at different time intervals (1, 6, 24, and 48 h) after hyperthermia.
Results: Our flowcytometry results indicated the 24-h time interval has the most significant effect on the cell population at S and G2/M phases. Therefore, the 24-h time interval can be proposed as the most appropriate time after hyperthermia for carrying out combinational radiotherapy procedure.
Conclusion: Among various investigated time intervals examined in our research, the 24-h time interval can be proposed as the most appropriate time between hyperthermia and radiotherapy for combinational therapy of breast cancer cells.
Kerwords: Radiotherapy, Hyperthermia, Gold Nanoparticles, MCF‑7 cancer cells
Jeywoeds: MTT assay, Clonogenic Aassay, Dose Response, Survival Curve
Ketwords: Radiation Therpay, Radiation sentisizers, Targeted Radiotherapy, Gold Nanoparticles (GNPSs), Cervical Cancer
Materials and methods: An anthropomorphic pelvis phantom was used in two modes representing a homogeneous and heterogeneous phantom. Three dimensional (3D) CRT planning composed of five fields were performed on the CT images of the phantoms using the CorPLAN treatment planning system (TPS) of a 2100C/D Varian linac. Delivery of 3DCRT was also simulated by EGSnrc Monte Carlo code for the same conditions used in the CorPLAN TPS. The dose distributions resulted from the MC simulations were compared with those of the CorPLAN TPS for both of the phantoms based on the "dose difference (DD) percentages" and "distance to agreement (DTA)" parameters.
Results: Findings indicated that the heterogeneity leads to an overdose estimation at the target location up to 2.8% and 4.4% for the 6 and 18 MV energies, respectively by the CorPLAN TPS compared with the MC simulation data. The average DD and DTA for the homogeneous phantom were 2.7%-3.4mm and 1.6%-2.3 mm while for the inhomogeneous phantom they were 5.5%-3.7 mm and 6.0%-2.5 mm at the 6 and 18 MV energies, respectively.
Conclusion: Our results indicates that the accuracy of the dosimetry parameters estimated by the CorPLAN TPS at 18 MV is more than that of 6 MV energy. But, the heterogeneity deteriorates more the accuracy level of such dosimetry parameters estimated by this commercial TPS at 18 MV energy.
Keywords: prostate cancer, conformal radiation therapy, Monte Carlo, treatment planning system
Method and Materials: In this experimental study, we used the MCF7 breast cancer cell line to investigate the effect of 13.56 MHz hyperthermia (at a temperature of 43°C for a period of 20 min) on their cell cycle arrest. We performed the flowcytometry assay to assess the changes in the mitotic phases of the cell population at different time intervals (1, 6, 24, and 48 h) after hyperthermia.
Results: Our flowcytometry results indicated the 24-h time interval has the most significant effect on the cell population at S and G2/M phases. Therefore, the 24-h time interval can be proposed as the most appropriate time after hyperthermia for carrying out combinational radiotherapy procedure.
Conclusion: Among various investigated time intervals examined in our research, the 24-h time interval can be proposed as the most appropriate time between hyperthermia and radiotherapy for combinational therapy of breast cancer cells.
Kerwords: Radiotherapy, Hyperthermia, Gold Nanoparticles, MCF‑7 cancer cells
Jeywoeds: MTT assay, Clonogenic Aassay, Dose Response, Survival Curve
Ketwords: Radiation Therpay, Radiation sentisizers, Targeted Radiotherapy, Gold Nanoparticles (GNPSs), Cervical Cancer
Materials and methods: An anthropomorphic pelvis phantom was used in two modes representing a homogeneous and heterogeneous phantom. Three dimensional (3D) CRT planning composed of five fields were performed on the CT images of the phantoms using the CorPLAN treatment planning system (TPS) of a 2100C/D Varian linac. Delivery of 3DCRT was also simulated by EGSnrc Monte Carlo code for the same conditions used in the CorPLAN TPS. The dose distributions resulted from the MC simulations were compared with those of the CorPLAN TPS for both of the phantoms based on the "dose difference (DD) percentages" and "distance to agreement (DTA)" parameters.
Results: Findings indicated that the heterogeneity leads to an overdose estimation at the target location up to 2.8% and 4.4% for the 6 and 18 MV energies, respectively by the CorPLAN TPS compared with the MC simulation data. The average DD and DTA for the homogeneous phantom were 2.7%-3.4mm and 1.6%-2.3 mm while for the inhomogeneous phantom they were 5.5%-3.7 mm and 6.0%-2.5 mm at the 6 and 18 MV energies, respectively.
Conclusion: Our results indicates that the accuracy of the dosimetry parameters estimated by the CorPLAN TPS at 18 MV is more than that of 6 MV energy. But, the heterogeneity deteriorates more the accuracy level of such dosimetry parameters estimated by this commercial TPS at 18 MV energy.
Keywords: prostate cancer, conformal radiation therapy, Monte Carlo, treatment planning system