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
Background: Conventional electron beam radiotherapy used for treating super cial cancer tumors su... more Background: Conventional electron beam radiotherapy used for treating super cial cancer tumors suffers from the disadvantage of low skin sparing effect. Furthermore, increasing electron energy for treating deeper-seated tumors leads to signi cant increase of skin dose. To overcome this, various grids are recommended for electron beam radiotherapy of subcutaneous tumors. However, appropriate grids are required to be designed for decreasing skin dose while delivering uniform high doses to deep-seated super cial tumors. Our goal was to design, examine and propose appropriate grid(s) for optimum electron beam radiotherapy of subcutaneous tumors with the best skin sparing with 6 and 18 MeV energies. Materials and Methods: Relevant dosimetric characteristics were determined and analyzed for ve grids manufactured from dry lead having various cavity diameters (1.5, 2.0, 2.5, 3.0, 3.5 cm) and shielded areas (0.3, 0.4, 0.5, 0.6, 0.7 cm) among the cavities but the same fraction of cavity/open (68%) and shielded/closed (38%) areas under the grid plates. Isodose distributions and dose pro les resulted from the grids were investigated using EDR2 lms and MATLAB software. Results: The grids with 2 and 2.5 cm diameter cavities and 0.4 and 0.5 cm shielded areas were the most appropriate grids for 6 and 18 MeV radiotherapy, respectively. With these grids, the 100% PDDs (percentage depth doses) located at 1.25 and 2.5 cm for an open led (without the grids) were moved down to 1.87 and 5.4 cm for 6 and 18 MeV energies, respectively. Furthermore, the proposed grids provided the least peak to valley dose variations hence the most uniform doses delivered at their relevant depths of treatment. Conclusions: To decrease the skin dose in 6 and 18 MeV electron beam radiotherapy of super cial subcutaneous tumors, various home-made grids were designed and investigated. The most appropriate
Iranian Journal of Radiation Research, Oct 10, 2021
Background: Comparing three whole pelvic radiotherapy (WPRT) procedures as well as two local radi... more Background: Comparing three whole pelvic radiotherapy (WPRT) procedures as well as two local radiotherapy (LRT) procedures with each other for the treatment of prostate cancer patients using dosimetric parameters and radiobiological models: tumor control probability (TCP), normal tissue complication probability (NTCP), and equivalent uniform dose (EUD). Materials and Methods: Two groups of prostate cancer patients underwent WPRT (n=16) and LRT (n=16) procedures. In the WPRT group, the patients treated with two intensity modulated radiation therapy (IMRT+IMRT) procedures at two consecutive phases. Then, two other techniques including a three dimensional (3D) conformal radiation therapy (3DCRT) phase followed by an IMRT phase (3DCRT+IMRT) and also two consecutive 3DCRT procedures (3DCRT+3DCRT) were carried out on the patients' data. In the LRT group, the patients treated with just an IMRT technique. Then a 3DCRT technique was also performed on the patients' data. All the WPRT and LRT procedures compared with each other based on the dosimetric parameters and radiobiological models. Results: The mean of dosimetric parameters did not exceed the specified dose constraints for the bladder and femoral heads in the 3DCRT+ IMRT, and for the bladder in the 3DCRT technique. In the WPRT and LRT procedures, the TCP values for the prostate did not reveal any significant differences (P>0.05). The NTCP results in accordance with the dosimetric results for the organs at risk (OARs) showed a significant decrease in the IMRT+IMRT (WPRT) and the IMRT (LRT) techniques (P<0.05). However, the EUD results were dependent on the type of the procedure and OARs. Conclusion: For selecting the appropriate treatment technique for each prostate cancer patient, a compromise between the dosimetric and radiobiological evaluation of the WPRT and LRT procedures should be considered.
Polish Journal of Medical Physics and Engineering, Sep 1, 2017
Purpose: It is well known that the main portion of artificial sources of ionizing radiation to hu... more Purpose: It is well known that the main portion of artificial sources of ionizing radiation to human results from X-ray imaging techniques. However, reports carried out in various countries have indicated that most of their cumulative doses from artificial sources are due to CT examinations. Hence assessing doses resulted from CT examinations is highly recommended by national and international radiation protection agencies. The aim of this research has been to estimate the effective and organ doses in an average human according to 103 and 60 ICRP tissue weighting factor for six common protocols of Multi-Detector CT (MDCT) machine in a comprehensive training general hospital in Tehran/Iran. Methods: To calculate the patients' effective dose, the CT-Expo2.2 software was used. Organs/tissues and effective doses were determined for about 20 patients (totally 122 patients) for every one of six typical CT protocols of the head, neck, chest, abdomen-pelvis, pelvis and spine exams. In addition, the CT dosimetry index (CTDI) was measured in the standard 16 and 32 cm phantoms by using a calibrated pencil ionization chamber for the six protocols and by taking the average value of CT scan parameters used in the hospital compared with the CTDI values displayed on the console device of the machine. Results: The values of the effective dose based on the ICRP 103 tissue weighting factor were: 0.6, 2.0, 3.2, 4.2, 2.8, and 3.9 mSv and based on the ICRP 60 tissue weighting factor were: 0.9, 1.4, 3, 7.9, 4.8 and 5.1 mSv for the head, neck, chest, abdomen-pelvis, pelvis, spine CT exams respectively. Relative differences between those values were-22, 21, 23,-6,-31 and 16 percent for the head, neck, chest, abdomen-pelvis, pelvis, spine CT exams, respectively. The average value of CTDI v calculated for each protocol was: 27.32 ± 0.9, 18.08 ± 2.0, 7.36 ± 2.6, 8.84 ± 1.7, 9.13 ± 1.5, 10.42 ± 0.8 mGy for the head, neck, chest, abdomen-pelvis and spine CT exams, respectively. Conclusions: The highest organ doses delivered by various CT exams were received by brain (15.5 mSv), thyroid (19.00 mSv), lungs (9.3 mSv) and bladder (9.9 mSv), bladder (10.4 mSv), stomach (10.9 mSv) in the head, neck, chest, and the abdomen-pelvis, pelvis, and spine respectively. Except the neck and spine CT exams showing a higher effective dose compared to that reported in Netherlands, other exams indicated lower values compared to those reported by any other country.
Background and purpose: Estimating dosimetric parameters for small fields at non-reference condit... more Background and purpose: Estimating dosimetric parameters for small fields at non-reference conditions lead to significant errors if they are done based on the conventional protocols used for large fields and reference conditions. The aim of this study was to determine and compare small fields correction factors (K NR and K NCSF) based on a novel protocol by using different types of detectors. Materials and methods: Specific circular cones were constructed and attached to a medical linac head to produce small field sizes down to 30 and 5mm diameters. Then, the K NR and K NCSF correction factors based on a recent protocol (TG155), proposed for small field dosimetry formalism, were determined for different active detectors (a pinpoint chamber, EDP20 and EDP10 diodes) in a homogeneous and a nonhomogeneous phantom at the above fields when irradiated to 6 and 18 MV beams of a Varian linac. Results: The K NR correction factors for the circle field of 30mm estimated for the pinpoint chamber, EDP20 and EDP10 diodes were 0.993, 1.
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.
Iranian Journal of Radiation Research, Jan 15, 2015
Background: Increasing the complexity in modern radiotherapy techniques have increased the delive... more Background: Increasing the complexity in modern radiotherapy techniques have increased the delivery me lowering consequently the treatment efficacy. Through simula ng the delivery me delay encountered in such techniques, its' effect on two cancer cell lines and the compensa ng doses given to prevent such effect was inves gated. Materials and Methods: F10B16 and 4T1 cancer cell lines were exposed to simulated clinical frac onated radiotherapy procedures commonly used in complex techniques. The survival rate of the cells exposed to 2, 4, and 6 Gy of ionizing radia on with two equal subfrac ons given at various me intervals between the frac ons (0.25-4 hours) were determined using the MTT assay. Then, relevant compensa ng doses were calculated and their efficacy in counterbalancing the me delay was assessed. Results: The cells' survival was increased with prolonged treatment mes in the frac onated groups being more significant at the lower me intervals (up to 2 hours) and for the higher radiosensi ve cells (4T1). Giving the compensated doses decreased the survival of the cells. Conclusion: Delivering appropriate compensa ng doses to the prolonged frac onated groups can counterbalance the effect of me delays encountered in complex radiotherapy techniques.
Background: Gold nanoparticles (GNPs) have been used to sensitize cancer cells and enhance the ab... more Background: Gold nanoparticles (GNPs) have been used to sensitize cancer cells and enhance the absorbed dose delivered to such cells. Active targeting can provide specific effect and higher uptake of the GNPs in the tumor cells, while having small effect on healthy cells. The aim of this study was to assess the possible radiosensitiazation effect of GNPs conjugated with AS1411 aptamer (AS1411/GNPs) on cancer cells treated with 4 MeV electron beams. Materials and methods: Cytotoxicity studies of the GNPs and AS1411/GNPs were carried out with MTT and MTS assay in different cancer cell lines of MCF-7, MDA-MB-231 and mammospheres of MCF-7 cells. Atomic absorption spectroscopy confirmed the cellular uptake of the gold particles. Radiosensitizing effect of the GNPs and AS1411/ GNPs on the cancer cells was assessed by clonogenic assay. Result: AS1411 aptamer increased the Au uptake in MCF-7 and MDA-MB-231 cells. Clonogenic survival data revealed that AS1411/GNPs at 12.5 mg/L could result in radiosensitization of the breast cancer cells and lead to a sensitizer enhancement ratio of 1.35 and 1.66 and 1.91 for MCf-7, MDA-MB-231 and mammosphere cells. Conclusion: Gold nanoparticles delivery to the cancer cells was enhanced by AS1411 aptamer and led to enhanced radiation induced cancer cells death. The combination of our clonogenic assay and Au cell uptake results suggested that AS1411 aptamer has enhanced the radiation-induced cell death by increasing Au uptake. This enhanced sensitization contributed to cancer stem cell-like cells to 4 MeV electron beams. This is particularly important for future preclinical testing to open a new insight for the treatment of cancers.
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
Background: Conventional electron beam radiotherapy used for treating super cial cancer tumors su... more Background: Conventional electron beam radiotherapy used for treating super cial cancer tumors suffers from the disadvantage of low skin sparing effect. Furthermore, increasing electron energy for treating deeper-seated tumors leads to signi cant increase of skin dose. To overcome this, various grids are recommended for electron beam radiotherapy of subcutaneous tumors. However, appropriate grids are required to be designed for decreasing skin dose while delivering uniform high doses to deep-seated super cial tumors. Our goal was to design, examine and propose appropriate grid(s) for optimum electron beam radiotherapy of subcutaneous tumors with the best skin sparing with 6 and 18 MeV energies. Materials and Methods: Relevant dosimetric characteristics were determined and analyzed for ve grids manufactured from dry lead having various cavity diameters (1.5, 2.0, 2.5, 3.0, 3.5 cm) and shielded areas (0.3, 0.4, 0.5, 0.6, 0.7 cm) among the cavities but the same fraction of cavity/open (68%) and shielded/closed (38%) areas under the grid plates. Isodose distributions and dose pro les resulted from the grids were investigated using EDR2 lms and MATLAB software. Results: The grids with 2 and 2.5 cm diameter cavities and 0.4 and 0.5 cm shielded areas were the most appropriate grids for 6 and 18 MeV radiotherapy, respectively. With these grids, the 100% PDDs (percentage depth doses) located at 1.25 and 2.5 cm for an open led (without the grids) were moved down to 1.87 and 5.4 cm for 6 and 18 MeV energies, respectively. Furthermore, the proposed grids provided the least peak to valley dose variations hence the most uniform doses delivered at their relevant depths of treatment. Conclusions: To decrease the skin dose in 6 and 18 MeV electron beam radiotherapy of super cial subcutaneous tumors, various home-made grids were designed and investigated. The most appropriate
Iranian Journal of Radiation Research, Oct 10, 2021
Background: Comparing three whole pelvic radiotherapy (WPRT) procedures as well as two local radi... more Background: Comparing three whole pelvic radiotherapy (WPRT) procedures as well as two local radiotherapy (LRT) procedures with each other for the treatment of prostate cancer patients using dosimetric parameters and radiobiological models: tumor control probability (TCP), normal tissue complication probability (NTCP), and equivalent uniform dose (EUD). Materials and Methods: Two groups of prostate cancer patients underwent WPRT (n=16) and LRT (n=16) procedures. In the WPRT group, the patients treated with two intensity modulated radiation therapy (IMRT+IMRT) procedures at two consecutive phases. Then, two other techniques including a three dimensional (3D) conformal radiation therapy (3DCRT) phase followed by an IMRT phase (3DCRT+IMRT) and also two consecutive 3DCRT procedures (3DCRT+3DCRT) were carried out on the patients' data. In the LRT group, the patients treated with just an IMRT technique. Then a 3DCRT technique was also performed on the patients' data. All the WPRT and LRT procedures compared with each other based on the dosimetric parameters and radiobiological models. Results: The mean of dosimetric parameters did not exceed the specified dose constraints for the bladder and femoral heads in the 3DCRT+ IMRT, and for the bladder in the 3DCRT technique. In the WPRT and LRT procedures, the TCP values for the prostate did not reveal any significant differences (P>0.05). The NTCP results in accordance with the dosimetric results for the organs at risk (OARs) showed a significant decrease in the IMRT+IMRT (WPRT) and the IMRT (LRT) techniques (P<0.05). However, the EUD results were dependent on the type of the procedure and OARs. Conclusion: For selecting the appropriate treatment technique for each prostate cancer patient, a compromise between the dosimetric and radiobiological evaluation of the WPRT and LRT procedures should be considered.
Polish Journal of Medical Physics and Engineering, Sep 1, 2017
Purpose: It is well known that the main portion of artificial sources of ionizing radiation to hu... more Purpose: It is well known that the main portion of artificial sources of ionizing radiation to human results from X-ray imaging techniques. However, reports carried out in various countries have indicated that most of their cumulative doses from artificial sources are due to CT examinations. Hence assessing doses resulted from CT examinations is highly recommended by national and international radiation protection agencies. The aim of this research has been to estimate the effective and organ doses in an average human according to 103 and 60 ICRP tissue weighting factor for six common protocols of Multi-Detector CT (MDCT) machine in a comprehensive training general hospital in Tehran/Iran. Methods: To calculate the patients' effective dose, the CT-Expo2.2 software was used. Organs/tissues and effective doses were determined for about 20 patients (totally 122 patients) for every one of six typical CT protocols of the head, neck, chest, abdomen-pelvis, pelvis and spine exams. In addition, the CT dosimetry index (CTDI) was measured in the standard 16 and 32 cm phantoms by using a calibrated pencil ionization chamber for the six protocols and by taking the average value of CT scan parameters used in the hospital compared with the CTDI values displayed on the console device of the machine. Results: The values of the effective dose based on the ICRP 103 tissue weighting factor were: 0.6, 2.0, 3.2, 4.2, 2.8, and 3.9 mSv and based on the ICRP 60 tissue weighting factor were: 0.9, 1.4, 3, 7.9, 4.8 and 5.1 mSv for the head, neck, chest, abdomen-pelvis, pelvis, spine CT exams respectively. Relative differences between those values were-22, 21, 23,-6,-31 and 16 percent for the head, neck, chest, abdomen-pelvis, pelvis, spine CT exams, respectively. The average value of CTDI v calculated for each protocol was: 27.32 ± 0.9, 18.08 ± 2.0, 7.36 ± 2.6, 8.84 ± 1.7, 9.13 ± 1.5, 10.42 ± 0.8 mGy for the head, neck, chest, abdomen-pelvis and spine CT exams, respectively. Conclusions: The highest organ doses delivered by various CT exams were received by brain (15.5 mSv), thyroid (19.00 mSv), lungs (9.3 mSv) and bladder (9.9 mSv), bladder (10.4 mSv), stomach (10.9 mSv) in the head, neck, chest, and the abdomen-pelvis, pelvis, and spine respectively. Except the neck and spine CT exams showing a higher effective dose compared to that reported in Netherlands, other exams indicated lower values compared to those reported by any other country.
Background and purpose: Estimating dosimetric parameters for small fields at non-reference condit... more Background and purpose: Estimating dosimetric parameters for small fields at non-reference conditions lead to significant errors if they are done based on the conventional protocols used for large fields and reference conditions. The aim of this study was to determine and compare small fields correction factors (K NR and K NCSF) based on a novel protocol by using different types of detectors. Materials and methods: Specific circular cones were constructed and attached to a medical linac head to produce small field sizes down to 30 and 5mm diameters. Then, the K NR and K NCSF correction factors based on a recent protocol (TG155), proposed for small field dosimetry formalism, were determined for different active detectors (a pinpoint chamber, EDP20 and EDP10 diodes) in a homogeneous and a nonhomogeneous phantom at the above fields when irradiated to 6 and 18 MV beams of a Varian linac. Results: The K NR correction factors for the circle field of 30mm estimated for the pinpoint chamber, EDP20 and EDP10 diodes were 0.993, 1.
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.
Iranian Journal of Radiation Research, Jan 15, 2015
Background: Increasing the complexity in modern radiotherapy techniques have increased the delive... more Background: Increasing the complexity in modern radiotherapy techniques have increased the delivery me lowering consequently the treatment efficacy. Through simula ng the delivery me delay encountered in such techniques, its' effect on two cancer cell lines and the compensa ng doses given to prevent such effect was inves gated. Materials and Methods: F10B16 and 4T1 cancer cell lines were exposed to simulated clinical frac onated radiotherapy procedures commonly used in complex techniques. The survival rate of the cells exposed to 2, 4, and 6 Gy of ionizing radia on with two equal subfrac ons given at various me intervals between the frac ons (0.25-4 hours) were determined using the MTT assay. Then, relevant compensa ng doses were calculated and their efficacy in counterbalancing the me delay was assessed. Results: The cells' survival was increased with prolonged treatment mes in the frac onated groups being more significant at the lower me intervals (up to 2 hours) and for the higher radiosensi ve cells (4T1). Giving the compensated doses decreased the survival of the cells. Conclusion: Delivering appropriate compensa ng doses to the prolonged frac onated groups can counterbalance the effect of me delays encountered in complex radiotherapy techniques.
Background: Gold nanoparticles (GNPs) have been used to sensitize cancer cells and enhance the ab... more Background: Gold nanoparticles (GNPs) have been used to sensitize cancer cells and enhance the absorbed dose delivered to such cells. Active targeting can provide specific effect and higher uptake of the GNPs in the tumor cells, while having small effect on healthy cells. The aim of this study was to assess the possible radiosensitiazation effect of GNPs conjugated with AS1411 aptamer (AS1411/GNPs) on cancer cells treated with 4 MeV electron beams. Materials and methods: Cytotoxicity studies of the GNPs and AS1411/GNPs were carried out with MTT and MTS assay in different cancer cell lines of MCF-7, MDA-MB-231 and mammospheres of MCF-7 cells. Atomic absorption spectroscopy confirmed the cellular uptake of the gold particles. Radiosensitizing effect of the GNPs and AS1411/ GNPs on the cancer cells was assessed by clonogenic assay. Result: AS1411 aptamer increased the Au uptake in MCF-7 and MDA-MB-231 cells. Clonogenic survival data revealed that AS1411/GNPs at 12.5 mg/L could result in radiosensitization of the breast cancer cells and lead to a sensitizer enhancement ratio of 1.35 and 1.66 and 1.91 for MCf-7, MDA-MB-231 and mammosphere cells. Conclusion: Gold nanoparticles delivery to the cancer cells was enhanced by AS1411 aptamer and led to enhanced radiation induced cancer cells death. The combination of our clonogenic assay and Au cell uptake results suggested that AS1411 aptamer has enhanced the radiation-induced cell death by increasing Au uptake. This enhanced sensitization contributed to cancer stem cell-like cells to 4 MeV electron beams. This is particularly important for future preclinical testing to open a new insight for the treatment of cancers.
Journal of biomedical physics & engineering, Jan 30, 2019
Background: Estimating dosimetric parameters for small fields under non-reference conditions lead... more 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 different depths and field sizes. Objective: Determining correction factors (K NR and K NCSF) recommended recently for small field dosimetry formalism by American Association of Physicists in Medicine (AAPM) for different detectors at 6 and 18 MV photon beams. Methods: EGSnrc Monte Carlo code was used to calculate the doses measured with different detectors located in a slab phantom and the recommended K NR and K NCSF correction factors for various circular small field sizes ranging from 5-30 mm diameters. K NR and K NCSF correction factors were determined for different active detectors (a pinpoint chamber, EDP-20 and EDP-10 diodes) in a homogeneous phantom irradiated to 6 and 18 MV photon beams of a Varian linac (2100C/D). Results: K NR correction factor estimated for the highest small circular field size of 30 mm diameter for the pinpoint chamber, EDP-20 and EDP-10 diodes were 0.993, 1.020 and 1.054; and 0.992, 1.054 and 1.005 for the 6 and 18 MV beams, respectively. The K NCSF correction factor estimated for the lowest circular field size of 5 mm for the pinpoint chamber, EDP-20 and EDP-10 diodes were 0.994, 1.023, and 1.040; and 1.000, 1.014, and 1.022 for the 6 and 18 MV photon beams, respectively. Conclusion: Comparing the results obtained for the detectors used in this study reveals that the unshielded diodes (EDP-20 and EDP-10) can confidently be recommended for small field dosimetry as their correction factors (K NR and K NCSF) was close to 1.0 for all small field sizes investigated and are mainly independent from the electron beam spot size.
Background: Dose painting planning would be more complicated due to different levels of prescribe... more Background: Dose painting planning would be more complicated due to different levels of prescribed doses and more complex evaluation with conventional plan quality indices considering uniform dose prescription. Therefore, we tried to introduce new indices for evaluating the dose distribution conformity and homogeneity of treatment volumes based on the tumoral cell density and relative volumes of each lesion in prostate IMRT. Methods: CT and MRI scans of 20 male patients having local prostate cancer were used for IMRT DP planning. Apparent diffusion coefficient (ADC) images were imported to a MATLAB program to identify lesion regions based on ADC values automatically. Regions with ADC values lower than 750 mm 2 /s and regions with ADC values higher than 750 and less than 1500 mm 2 /s were considered CTV 70Gy (clinical tumor volume with 70 Gy prescribed dose), and CTV 60Gy , respectively. Other regions of the prostate were considered as CTV 53Gy. New plan evaluation indices based on evaluating the homogeneity (IOE(H)), and conformity (IOE(C)) were introduced, considering the relative volume of each lesion and cellular density obtained from ADC images. These indices were compared with conventional homogeneity and conformity indices and IOEs without considering cellular density. Furthermore, tumor control probability (TCP) was calculated for each patient, and the relationship of the assessed indices were evaluated with TCP values. Results: IOE (H) and IOE (C) with considering cellular density had significantly lower values compared to conventional indices and IOEs without considering cellular density. (P < 0.05). TCP values had a stronger relationship with IOE(H) considering cell density (R 2 =-0.415), and IOE(C) without considering cell density (R 2 = 0.624). Conclusion: IOE plan evaluation indices proposed in this study can be used for evaluating prostate IMRT dose painting plans. We suggested to consider cell densities in the IOE(H) calculation formula and it's appropriate to calculate IOE(C) without considering cell density values.
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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