Publications by authors named "Ghazale Geraily"

36 Publications

Gold-nanoparticle-enriched breast tissue in breast cancer treatment using the INTRABEAM® system: a Monte Carlo study.

Radiat Environ Biophys 2021 Dec 3. Epub 2021 Dec 3.

Department of Physics, College of Natural and Computational Sciences, Aksum University, Axum, Ethiopia.

Using a 50-kV INTRABEAM system after breast-conserving surgery, breast skin injury and long treatment time remain the challenging problems when large-size spherical applicators are used. This study has aimed to address these problems using gold (Au) nanoparticles (NPs). For this, surface and isotropic doses were measured using a Gafchromic EBT3 film and a water phantom. The particle propagation code EGSnrc/Epp was used to score the corresponding doses using a geometry similar to that used in the measurements. The simulation was validated using a gamma index of 2%/2 mm acceptance criterion in the gamma analysis. After validation Au-NP-enriched breast tissue was simulated to quantify any breast skin dose reduction and shortening of treatment time. It turned out that the gamma value deduced for validation of the simulation was in an acceptable range (i.e., less than one). For 20 mg-Au/g-breast tissue, the calculated Dose Enhancement Ratio (DER) of the breast skin was 0.412 and 0.414 using applicators with diameters of 1.5 cm and 5 cm, respectively. The corresponding treatment times were shortened by 72.22% and 72.30% at 20 mg-Au/g-breast tissue concentration, respectively. It is concluded that Au-NP-enriched breast tissue shows significant advantages, such as reducing the radiation dose received by the breast skin as well as shortening the treatment time. Additionally, the DERs were not significantly dependent on the size of the applicators.
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http://dx.doi.org/10.1007/s00411-021-00954-2DOI Listing
December 2021

Feasibility of 18-MV grid therapy from radiation protection aspects: unwanted dose and fatal cancer risk caused by photoneutrons and scattered photons.

Comput Methods Programs Biomed 2022 Jan 12;213:106524. Epub 2021 Nov 12.

Department of Radiation Oncology, Advocate Lutheran General Hospital, 1700 Lutheran, Park Ridge, Illinois, USA. Electronic address:

Purpose: Photoneutron production is a common concern when using 18-MV photon beams in radiation therapy. In Spatially Fractionated Grid Radiation Therapy (SFGRT), the grid block in the collimation system modifies the neutron production, photon scattering, and electron contamination in and out of the radiation field. Such an effect was studied with grids made of different high-Z materials by Monte Carlo simulations. The results were also used to evaluate the lifetime risk of fatal cancers.

Methods: MCNPX® code (2.7.0 extensions) was employed to simulate an 18-MV LINAC (Varian 2100 C/D). Three types of grid made of brass, cerrobend, and lead were used to study the neutron and electron fluence. Output factors for each grid with different field sizes were calculated. A revised female MIRD phantom with an 8-cm spherical tumor inside the liver was used to estimate the dose to the tumor and the critical organs. A 20-Gy SFGRT plan with Anterior Posterior (AP) - Posterior Anterior (PA) grid beams was compared with a Conventional Fractionated Radiation Therapy (CFRT) plan which delivered 40-Gy to the tumor by AP-PA open beams. Neutron equivalent dose, photon equivalent dose, as well as lifetime risks of fatal cancer were calculated in the organs at risk.

Results: The grid blocks reduced the fluence of contaminant electrons inside the treatment field by more than 50%. The neutron fluences per electron-history in SFGRT plans with brass, cerrobend and lead were on average 55%, 31% and 31% less than that of the CFRT plan, respectively. However, when converting to fluences per delivered dose (Gy), the cerrobend and lead grid may incur higher neutron dose for 20 × 20 cm field size and above. The changes in neutron mean energy, as well as the correlated radiation weighting factors, were insignificant. The total risk due to the photoneutrons in the SFGRT plans was 87% or lower than that in the CFRT plans. In both SFGRT and CFRT plans, the contribution of the primary and scattered photons to the fatal cancer risk was 2 times or more than the photoneutrons. The total risks from photons in SFGRT with brass, cerrobend, and lead blocks were 1.733, 1.374, and 1.260%, respectively, which were less than 30% of the total photon-risk in CFRT (5.827%).

Conclusion: In the brass, cerrobend, and lead grids, the attenuation of photoneutrons outweighs its photoneutron production in 18-MV SFGRT. The total cancer risks from photons and photoneutrons in the SFGRT plans were 30% or less of the risks in the CFRT plans (5.911%). Using 18 MV photon beams with brass, cerrobend, and lead grid blocks is still a feasible option for SFGRT.
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http://dx.doi.org/10.1016/j.cmpb.2021.106524DOI Listing
January 2022

A review study on application of gel dosimeters in low energy radiation dosimetry.

Appl Radiat Isot 2022 Jan 3;179:110015. Epub 2021 Nov 3.

Medical Physics and Medical Engineering Department, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran. Electronic address:

Introduction: The accuracy of dose delivered to tumors and surrounding normal tissues is vital in either radiotherapy using low energy photons and radiological techniques as well as radiotherapy with mega voltage energies. This systematic review focuses on applications of gel dosimetry in low energy radiation contexts applied either through radiotherapy or interventional radiology.

Methods: Literature was reviewed based on electronic databases: Google Scholar, Scopus, Embase, PubMed, Science Direct, Research Gate and IOP science. The search was conducted on relevant terms in the title and keywords. 82 articles related to our criteria has been extracted and included in the study.

Results: The findings demonstrated that almost all types of gel dosimeters had an acceptable accuracy and high resolution in low energy radiation contexts with their own limitations and advantages.

Conclusion: Gel dosimeters compete well with other conventional dosimeters in terms of tissue equivalence and energy dependence; however, choosing the best gel dosimeter for use in low energy radiation dosimetry depends on their different limitation and advantages. There are some general features about each gel group which can help to select the suitable gel related to our work. For example, methacrylic acid based gel dosimeters show higher sensitivity compared to other types of gel dosimeters but have more toxicity and are dose rate dependent in the range of dose rates applied in low energy contexts. In addition, Fricke gel dosimeters exhibit less sensitivity while they are independent of dose rate and energy applied in low energy situations.
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http://dx.doi.org/10.1016/j.apradiso.2021.110015DOI Listing
January 2022

Monte Carlo evaluation of out-of-field dose in 18 MV pelvic radiotherapy using a simplified female MIRD phantom.

Biomed Phys Eng Express 2021 Nov 11;8(1). Epub 2021 Nov 11.

Department of Medical Physics and Biomedical Engineering, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.

This study was devoted to determining the unwanted dose due to scattered photons to the out-of-field organs and subsequently estimate the risk of secondary cancers in the patients undergoing pelvic radiotherapy. A typical 18 MV Medical Linear Accelerator (Varian Clinac 2100 C/D) was modeled using MCNPXcode to simulate pelvic radiotherapy with four treatment fields: anterior-posterior, posterior-anterior, right lateral, left lateral. Dose evaluation was performed inside Medical Internal Radiation Dose (MIRD) revised female phantom. The average photon equivalent dose in out-of-field organs is 8.53 mSv Gy, ranging from 0.17 to 72.11 mSv Gy, respectively, for the organs far from the Planning Treatment Volume (Brain) and those close to the treatment field (Colon). Evidence showed that colon with 4.3049% and thyroid with 0.0020% have the highest and lowest risk of secondary cancer, respectively. Accordingly, this study introduced the colon as an organ with a high risk of secondary cancer which should be paid more attention in the follow-up of patients undergoing pelvic radiotherapy. The authors believe that this simple Monte Carlo (MC) model can be also used in other radiotherapy plans and mathematical phantoms with different ages (from childhood to adults) to estimate the out-of-field dose. The extractable information by this simple MC model can be also employed for providing libraries for user-friendly applications (e.g. '.apk') which in turn increase the public knowledge about fatal cancer risk after radiotherapy and subsequently decrease the concerns in this regard among the public.
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http://dx.doi.org/10.1088/2057-1976/ac35a1DOI Listing
November 2021

Dosimetric comparison of AP/PA and bilateral geometries for total body irradiation treatment.

Radiat Environ Biophys 2021 Nov 6;60(4):663-672. Epub 2021 Sep 6.

Department of Medical Radiation Engineering, Central Tehran Branch, Islamic Azad University, Tehran, Iran.

Total body irradiation (TBI) is an external radiotherapy technique. Its aim is to deliver a therapeutic dose uniformly within ± 10% of the absorbed dose to the prescription point. In the present study, the TBI technique was implemented in anterior/posterior (AP/PA), and bilateral geometry with photons from a 6 [Formula: see text] and 18 [Formula: see text] accelerator. The TBI technique was implemented on an Alderson Rando phantom at 312 [Formula: see text] source surface distance. During bilateral fraction, rice bags were applied as tissue compensators. To reduce the lung's absorbed dose to the acceptance level, in AP/PA geometry lung blocks made of Cerrobend were used. The required monitor unit (MU) for each fraction was calculated regarding depending on the prescribed dose and beam output. Gafchromic EBT films were used for dosimetry between the phantom layers in eight selected points. It is demonstrated that dose uniformity for AP/PA geometry with 6 [Formula: see text] and 18 [Formula: see text] photons was within ± 10%. In contrast, for the bilateral geometry the dose uniformity was not acceptable for both studied energies; However, the results for 18 [Formula: see text] were better than those for 6 [Formula: see text]. Dose accuracy for all measurements was within ± 5 of the prescribed dose. The absorbed dose to the lungs was successfully reduced using the lung blocks. By combining different therapeutic geometries and energies over six fractions, the results of uniformity and accuracy of dose delivery could be improved. It is concluded that the introduced TBI method achieved good dose accuracy and acceptable dose uniformity. Lungs absorbed dose was lower than 10 [Formula: see text] using the lungs blocks. Based on these results, the TBI technique can now be implemented in radiotherapy at Tehran's Imam Hospital. The approach developed in the present study can be used and adapted to match with the conditions at other hospitals.
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http://dx.doi.org/10.1007/s00411-021-00933-7DOI Listing
November 2021

Evaluation of Dose Distribution in Optimized Stanford Total Skin Electron Therapy (TSET) Technique in Rando Anthropomorphic Phantom using EBT3 Gafchromatic Films.

J Biomed Phys Eng 2021 Aug 1;11(4):425-434. Epub 2021 Aug 1.

PhD, Department of Anatomy, Tehran University of Medical Sciences, Tehran, Iran.

Background: The Total Skin Electron Therapy (TSET) targets the whole of skin using 6 to 10 MeV electrons in large field size and large Source to Surface Distance (SSD). Treatment in sleeping position leads to a better distribution of dose and patient comfort.

Objective: This study aims to investigate the uniformity of absorbed dose in the sleeping Stanford technique on the Rando phantom using dosimetry.

Material And Methods: It is an experimental study which was performed using 6 MeV electron irradiation produced by Varian accelerator in the AP and PA positions with gantry angles of 318/3, 0 and 41/5 degrees, and RAO, LAO, RPO and LPO with 291/4 gantry angle and 45 degrees of collimator angle in the sleeping position.

Results: The results show that the dose uniformity achieved in this technique is in the range of (100 ± 25%) and, the dose accuracy was 6%.

Conclusion: Total Skin Electron Therapy (TSET) technique in sleeping position is very suitable for elderly and disabled patients, and meets the required dose uniformity. Furthermore, the use of a flattening filter is recommended for the more dose distribution uniformity.
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http://dx.doi.org/10.31661/jbpe.v0i0.1035DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8385220PMC
August 2021

Commissioning and quality assurance of Euromechanics add-on multileaf collimator.

Biomed Phys Eng Express 2020 12 21;7(1). Epub 2020 Dec 21.

Department of Medical Physics, Tehran University of Medical Science, Tehran, Iran.

In this study, the beam characteristics of a Euromechanics add-on MLC that has been installed on a Varian CLINAC 2100 C/D linear accelerator are presented. This was the first installation of 60-leaf PMLC from Euromechanics Company worldwide and all mechanical and dosimetric parameters were measured before clinical use of this kind of MLC. Mechanical tests were executed for different gantry and collimator angles. Leaf position accuracy and leaf gap reproducibility were checked with four different tests. The leaf transmissions, collimator (Sc), phantom (Sp), total (Sc,p) scatter factors, output of the machine, beam profiles for off-axis ratios, central axis depth dose, flatness, symmetry and penumbra have been measured for different field sizes pre and post MLC installation in 6 and 18 MV-mode. To evaluate the effect of new data on clinical plans, different beam setup configurations conformed with MLC and custom blocks were planned on CT images of thorax a CIRS phantom model 002LFC in the same treatment planning system. Leaf position in picket fence test found to be in range between 4.89-5.02 cm instead of nominal 5 cm, however the results of this test with EPIDs image and PIPSpro software showed the higher deviation rather than the results reported from the tests with EBT3 films. The measured data showed that on average Sc,p and Sc were increased 0.22% (P = 0.86) and 0.34% (P = 0.86) for 6 MV and 0.37% (P = 0.84) and 0.42% (P = 0.88) for 18 MV beams for different field sizes, respectively. Good agreement was observed between the PDD and profile curves pre and post MLC installation that was expected based on no changes in beam energy and geometry of the collimators. Based on the mechanical and dosimetry results which have been achieved from our different standard tests, it was found no significant differences between pre and post MLC installation values. This indicates, installation and using this system is clinically acceptable.
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http://dx.doi.org/10.1088/2057-1976/abbd23DOI Listing
December 2020

Comparison of dosimetric characteristics of physical wedge and enhanced dynamic wedge in inhomogeneous medium using Monte Carlo simulations.

Rep Pract Oncol Radiother 2021 25;26(1):59-65. Epub 2021 Feb 25.

Pars Hospital, Tehran, Islamic Republic of Iran.

Background: Widely used physical wedges in clinical radiotherapy lead to beam intensity attenuation as well as the beam hardening effect, which must be considered. Dynamic wedges devised to overcome the physical wedges (PWs) problems result in dosimetry complications due to jaw movement while the beam is on. This study was aimed to investigate the usability of physical wedge data instead of enhanced dynamic wedge due to the enhanced dynamic wedge (EDW) dosimetry measurement hardships of Varian 2100CD in inhomogeneous phantom by Monte Carlo code as a reliable method in radiation dosimetry.

Materials And Methods: A PW and EDW-equipped-linac head was simulated using BEAMnrc code. DOSXYZnrc was used for three-dimensional dosimetry calculation in the CIRS phantom.

Results: Based on the isodose curves, EDW generated a less scattered as well as lower penumbra width compared to the PW. The depth dose variations of PWs and EDWs were more in soft tissue than the lung tissue. Beam profiles of PW and EDW indicated good coincidence in all points, except for the heel area.

Conclusion: Results demonstrated that it is possible to apply PW data instead of EDW due to the dosimetry and commissioning hardships caused by EDW in inhomogeneous media.
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http://dx.doi.org/10.5603/RPOR.a2021.0012DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8086706PMC
February 2021

Investigation of the Scaling Formula Accuracy for Poly-energetic Kernel Calculation in 6 MV Photon Beam.

J Biomed Phys Eng 2021 Apr 1;11(2):135-142. Epub 2021 Apr 1.

PhD Candidate, Department of Medical Physics, Isfahan University of Medical Sciences, Isfahan, Iran.

Background: Dose distribution can be obtained from total energy released per unit mass (TERMA) and inhomogeneous energy deposition kernel (EDK) convolution. Since inhomogeneous EDK data is location-dependent, it is calculated by employing the density scaling method rather than Monte Carlo based user code EDKnrc.

Objective: The present study aimed at investigating EDK scaling formula accuracy in the presence of lung and bone inhomogeneities.

Material And Methods: In this theoretical-practical study, six EDKs datasets with lung and bone inhomogeneity in different radii were generated using EDKnrc user code and density scaling formula. Then the scaling method data and corresponding EDKnrc-generated ones were compared to enhance the calculations, and some correction factors for error reduction were also derived to create more consistency between these data.

Results: The study has shown that the errors in the theoretical method for calculating inhomogeneous EDKs were significantly reduced based on the attenuation coefficient and parameter, with α equal to 1.2 and 0.8 for bone and lung voxels, respectively.

Conclusion: Although the density scaling method has acceptable accuracy, the error values are significant at the location of lung or bone voxels. By using the mentioned correction factors, the calculation inaccuracy of heterogeneous EDKs can be reduced down to 5%. However, the lung heterogeneity results corrected by the method are not as good as the bone cases.
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http://dx.doi.org/10.31661/jbpe.v0i0.2009-1196DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8064139PMC
April 2021

Dosimetric effect of nanoparticles in the breast cancer treatment using INTRABEAMsystem with spherical applicators in the presence of tissue heterogeneities: A Monte Carlo study.

Biomed Phys Eng Express 2021 04 28;7(3). Epub 2021 Apr 28.

Department of Medical Physics and Biomedical Engineering, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.

Using the 50 kV INTRABEAMIORT system after breast-conserving surgery: tumor recurrence and organs at risk (OARs), such as the lung and heart, long-term complications remain the challenging problems for breast cancer patients. So, the objective of this study was to address these two problems with the help of high atomic number nanoparticles (NPs). A Monte Carlo (MC) Simulation type EGSnrc C++ class library (egspp) with its Easy particle propagation (Epp) user code was used. The simulation was validated against the measured depth dose data found in our previous study (Tegaw,2020 Dosimetric characteristics of the INTRABEAMsystem with spherical applicators in the presence of air gaps and tissue heterogeneities,. (10.1007/s00411-020-00835-0)) using the gamma index and passed 2%/2 mm acceptance criteria in the gamma analysis. Gold (Au) NPs were selected after comparing Dose Enhancement Ratios (DERs) of bismuth (Bi), Au, and platinum (Pt) NPs which were calculated from the simulated results. As a result, 0.02, 0.2, 2, 10, and 20 mg-Au/g-breast tissue were used throughout this study. These particles were not distributed in discrete but in a uniform concentration. For 20 mg-Au/g-breast tissue, the DERs were 3.6, 0.420, and 0.323 for breast tissue, lung, heart, respectively, using the 1.5 cm-diameter applicator (AP) and 3.61, 0.428, and 0.335 forbreast tissue, lung, and heart using the 5 cm-diameter applicator, respectively. DER increased with the decrease in the depth of tissues and increase in the effective atomic number (Z) and concentration of Au NPs, however, there was no significant change as AP sizes increased. Therefore, Au NPs showed dual advantages such as dose enhancement within the tumor bed and reduction in the OARs (heart and lung).
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http://dx.doi.org/10.1088/2057-1976/abf6a9DOI Listing
April 2021

Bismuth oxide nanoparticles as agents of radiation dose enhancement in intraoperative radiotherapy.

Med Phys 2021 Mar 1;48(3):1417-1426. Epub 2021 Feb 1.

Radiation Oncology Research Center, Cancer Institute, Tehran University of Medical Sciences, Tehran, Iran.

Purpose: Intraoperative radiotherapy (IORT) technique is an advanced radio therapeutic method used for delivery of a single high-dose radiation during surgery while removing healthy tissues from the radiation field. Nowadays, growing attention is being paid to IORT for its low-energy (kilovoltage) delivery as it requires less radiation protection, but suffers several disadvantages, including high-dose delivery and prolonged treatment time. The application of nanoparticles with high atomic number and high attenuation coefficients in kilovoltage energy may help overcome the mentioned shortcomings. This study was designed to investigate and quantify the mean dose enhancement factor (DEF) in the presence of nanoparticles using IORT method.

Methods: Bismuth oxide nanoparticles (Bi O NPs), both in sheet and spherical formats, were synthesized using a novel hydrothermal method and characterized with x-ray diffraction (XRD), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) analysis. Genipin-gelatin gel dosimeter (GENIPIN) was produced in three batches of pure with sheet and with spherical nanoparticles in concentration of 46.596 µg/ml, and irradiated with 50 kV x-rays.

Results: Samples were scanned by a spectrophotometer, which indicated a DEF of 3.28   0.37 and 2.50   0.23 for sheet and spherical NPs, respectively. According to the results of this study, GENIPIN is a suitable dosimeter for the evaluation of three-dimensional dose distribution in the presence Bi O NPs.

Conclusion: As a result, IORT along with Bi O NPs has the potential to reduce treatment time and/or normal tissue dose; moreover, it could provide localized dose enhancement.
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http://dx.doi.org/10.1002/mp.14697DOI Listing
March 2021

Evaluation of ferrous benzoic methylthymol-blue gel as a dosimeter via magnetic resonance imaging.

Phys Med 2020 Dec 20;80:47-56. Epub 2020 Oct 20.

Brain and Spinal Cord Injury Research Center, Neuroscience Institute, Tehran University of Medical Science, Tehran, Iran; Radiation Oncology Research Center, Department of Radiation Ocology, Cancer Institute, Tehran Universty of Medical Science, Tehran, Iran.

Purpose: In previous studies, methylthymol-blue and benzoic acid have been introduced as a diffuser limiter and sensitivity enhancer in the gel dosimeter composition, respectively. This work focused on analyzing a formulation of the Fricke gel dosimeter consisting of methylthymol-blue and benzoic acid through magnetic resonance imaging.

Methods: The gel dosimeter samples were irradiated using 6, 10, and 15 MV photons with different levels of doses and read using a 1.5 T scanner in order to evaluate the dose-response sensitivity and to study the effect of benzoic acid concentration, diffusion coefficient and temperature and to determine the temporal stability of the gel dosimeter.

Results: Inspection of radiological properties revealed that this gel dosimeter can be considered as a tissue equivalent medium. Within the dose range 0 to 1000 cGy, the R1 sensitivity and R2 sensitivity of the gel dosimeter equaled 0.058 ± 0.003 and 0.092 ± 0.004 sGy, respectively. The diffusion coefficient was less than 0.85 ± 0.02mmh for doses higher than 200 cGy. In addition, by changing the temperature from 15C to 25, the R1 sensitivity and R2 sensitivity decreased about 5 and 11%, respectively. Further, no significant energy and dose rate dependence were observed over photon energies of 6, 10, and 15 MV and over the range 65 to 525 cGy min.

Conclusions: Based on our observation, the ferrous benzoic acid methylthymol-blue gel dosimeter can be suggested to measure the dose distribution. Further analysis is required to clarify its performance in clinical situations.
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http://dx.doi.org/10.1016/j.ejmp.2020.10.006DOI Listing
December 2020

Evaluation of lung heterogeneity effects on dosimetric parameters in small photon fields using MAGIC polymer gel, Gafchromic film, and Monte Carlo simulation.

Appl Radiat Isot 2020 Dec 9;166:109233. Epub 2020 Aug 9.

Department of Radiology, Faculty of Para-Medicine, Hormozgan University of Medical Sciences, Bandar Abbas, Iran. Electronic address:

In this work, the performance of MAGIC polymer gel in measuring dosimetric parameters beyond lung heterogeneity in small fields was investigated. All data were obtained using MAGIC, EBT2, and MC in four small field sizes. The maximum local differences between MAGIC and MC were less than 5.1, 3.9, 3.1, and 2.6% for PDD values behind lung heterogeneity at 5, 10, 20, and 30 mm field sizes, respectively. The findings showed that MAGIC is a suitable tool for dosimetry behind low-density heterogeneity.
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http://dx.doi.org/10.1016/j.apradiso.2020.109233DOI Listing
December 2020

Dosimetric characteristics of the INTRABEAM ® system with spherical applicators in the presence of air gaps and tissue heterogeneities.

Radiat Environ Biophys 2020 05 31;59(2):295-306. Epub 2020 Mar 31.

Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, Tehran, Iran.

The main aim of this study was to investigate the dosimetric characteristics of the INTRABEAM ® system in the presence of air gaps between the surface of applicators (APs) and tumor bed. Additionally, the effect of tissue heterogeneities was another focus. Investigating the dosimetric characteristics of the INTRABEAM® system is essential to deliver the required dose to the tumor bed correctly and reduce the delivered dose to the ribs and lung. Choosing the correct AP size and fitting it to the lumpectomy cavity is essential to remove the effect of air gaps and avoid inaccurate dose delivery. Consequently, the Geant4 toolkit was used to simulate the INTRABEAM ® system with spherical APs of various sizes. The wall effect of the ion chamber (IC) PTW 34013 used in the present study was checked. The simulations were validated in comparison with measurements, and then used to calculate any inaccuracies in dose delivery in the presence of 4- and 10-mm air gaps between the surface of the APs and the tumor bed. Also, the doses received due to tissue heterogeneities were characterized. It turned out that measurements and simulations were approximately in agreement (± 2%) for all sizes of APs. The perturbation factor introduced by the IC due to differences in graphite-coated polyethylene and air as compared to the phantom material was approximately equal to one for all AP. The greatest relative dose delivery difference was observed for an AP with a diameter of 1.5 cm, i.e., 44% and 70% in the presence of 4- and 10-mm air gaps, respectively. In contrast, the lowest relative dose delivery difference was observed for an AP with a diameter of 5 cm, i.e., 24% and 42% in the presence of 4- and 10-mm air gaps, respectively. Increasing APs size showed a decrease in relative dose delivery difference due to the presence of air gaps. In addition, the undesired dose received by the ribs turned out to be higher when a treatment site closer to the ribs was assumed. The undesired dose received by the ribs increased as the AP size increased. The lung dose turned out to be decreased due to the shielding effect of the ribs, small lung density, and long separation distance from the AP surface.
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http://dx.doi.org/10.1007/s00411-020-00835-0DOI Listing
May 2020

Beam penumbra reduction of Gamma Knife machine model 4C using Monte Carlo simulation.

Comput Methods Programs Biomed 2020 May 5;188:105261. Epub 2019 Dec 5.

Department of Radiology, Faculty of Para-Medicine, Hormozgan University of Medical Sciences, Bandar Abbas, Islamic Republic of Iran.

Background And Objective: In small radiation fields used in stereotactic radiosurgery penumbra is an important portion of the field size especially when critical organs at risk are located near the treatment sites. This study was aimed to reduce penumbra width (90%-50% isodose lines) of Gamma Knife (GK) machine by investigating of source to diaphragm distance (SDD) and designing compensating filter.

Methods: Compensating filters at the end of the helmet collimators with the aim of reducing penumbra as well as reducing hot spots appeared near the edge of beam were modeled using Monte Carlo simulation code. Moreover, the SDD parameter was increased as one of the effective factors on penumbra width.

Results: Results showed that single beam penumbra width using optimal design of filters was decreased by 59.49%, 42.50%, 39.02% and 34.44% with attenuation of 30.53%, 13.67%, 11.43% and 9.82% for 4, 8, 14 and 18 mm field sizes, respectively.

Conclusions: The designed filters lead to considerable reductions in single beams penumbra width as well as a noticeable reduction in maximum dose emerged near the beam edge due to the curved lateral surface of filters.
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http://dx.doi.org/10.1016/j.cmpb.2019.105261DOI Listing
May 2020

Different Methods of Measuring Neutron Dose/Fluence Generated During Radiation Therapy with Megavoltage Beams.

Health Phys 2020 01;118(1):65-74

Medical Physics and Medical Engineering Department, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran.

Medical linear accelerators (linacs) are the most frequently applied radiation therapy machines in the locoregional treatment of cancers by producing either high-energy electron or photon beams. However, with high-energy photons (>8 MeV), interaction of these photons with different high-Z nuclei of materials in components of the linac head unavoidably generates neutrons. On the other hand, the average energy of these generated neutrons has almost the highest radiation-weighting factor. Therefore, the produced neutrons should not be neglected. There are various tools for the measurement of neutron dose/fluence generated in a megavoltage linac, including thermoluminescent dosimeters, solid-state nuclear track detectors, bubble detectors, activation foils, Bonner sphere systems, and ionization chamber pairs. In this review article, each of the above-mentioned dosimetric methods will be described in detail.
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http://dx.doi.org/10.1097/HP.0000000000001130DOI Listing
January 2020

Evaluating the Expression of NOX2 and NOX4 Signaling Pathways in Rats' Lung Tissues Following Local Chest Irradiation; Modulatory Effect of Melatonin.

Int J Mol Cell Med 2018 21;7(4):220-225. Epub 2018 Nov 21.

Research Center for Molecular and Cellular Imaging, Tehran University of Medical Sciences (International Campus), Tehran, Iran.

Lung injury is one of the major concerns for chest cancer patients that undergo radiotherapy as well as persons exposed to an accidental radiological event. Reduction/oxidation (redox) system plays a key role in lung injury via chronic upregulation of pro-oxidant enzymes. and are two important reactive oxygen species generating enzymes that are involved in radiation toxicity in some organs such as the bone marrow. In this study, we aimed to evaluate the expression of and signaling in rat's lung tissues. Upregulation of these genes may be involved in radiation-induced lung injury. Moreover, we evaluated the role of pre-treatment with melatonin on the expression of these genes. Twenty male rats were divided into 4 groups as control; melatonin treated; irradiation; and irradiation with melatonin pre-treatment. Rats were exposed to 15 Gy Co gamma rays and sacrificed after 10 weeks for evaluation of , , , , and gene expression by real-time PCR. Results showed the upregulation of all five genes. The expression of was more obvious compared to other genes. Administration of melatonin before irradiation could attenuate the expression of all mentioned genes. Results indicate that upregulation of NADPH oxidase genes such as and may be involved in the late effects of lung exposure to ionizing radiation. Melatonin via downregulation of these pro-oxidant genes is able to attenuate radiation toxicity in the lung.
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http://dx.doi.org/10.22088/IJMCM.BUMS.7.4.220DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6709931PMC
November 2018

Evaluating the effectiveness of combined radiotherapy and hyperthermia for the treatment response of patients with painful bony metastases: A phase 2 clinical trial.

J Therm Biol 2019 Aug 27;84:129-135. Epub 2019 Jun 27.

Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, Tehran, Iran. Electronic address:

Introduction: Since the survival time of patients with bony metastases has noticeably improved in recent years, these patients are at high risk of complications associated with this metastasis. Hence, the appropriate choice of treatment modality or combination of therapeutic approaches can lead to increasing bone pain relief, improving quality of life, etc. This study is aimed to evaluate the effectiveness of combined radiotherapy and hyperthermia for the treatment response of patients with painful bony metastases.

Patients And Methods: In a single-arm clinical trial, 23 eligible patients (14 female and 9 male) with the mean age of 67 years old and suffering from bony metastases were enrolled in the study. Two hours after radiotherapy, the patients underwent hyperthermia for 1 h in the supine position. All the patients completed the brief pain inventory (BPI) assessment tool and quality of life questionnaire (QLQ-C30) from the European Organization for Research and Treatment of Cancer (EORTC) at the baseline, end of the treatment and 1, 2 and 3 months thereafter. The response to the treatment was assessed as the zero score (complete response) or two or more than two-point drop of the worst pain within the preceding 24 h (partial response) during the 3-month posttreatment.

Results: All the pain intensity and interference scores, except the pain interference with the enjoyment of life score, significantly decreased. A total of 18 out of 23 patients (78%) achieved complete or partial response. The number of patients using pain relief medications decreased from 74% (n=17) at the baseline to 48% (n=11) 3 months later. Moreover, except for nausea and vomiting, appetite loss, diarrhea and financial impact problems, the patients' quality of life improved significantly in all the functional scales and symptoms within 3 months.

Conclusion: This study showed that using hyperthermia in combination with radiotherapy significantly ameliorated bone pain among the patients suffering from cancer with painful bony metastases.
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http://dx.doi.org/10.1016/j.jtherbio.2019.06.003DOI Listing
August 2019

Measurement of eye and lens doses in the presence and absence of shield during whole brain irradiation.

J Cancer Res Ther 2019 Jul-Sep;15(3):544-549

Medical Physics and Medical Engineering Department, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran.

Aim: The aim was to measure doses of eyes and lenses in the presence and absence of shield during whole brain irradiation (WBI). In addition, the dose calculations accuracy of radiation therapy dose plan treatment planning system (TPS) in dose calculation of the eyes and lenses in WBI was evaluated.

Materials And Methods: To measure the eyes and lenses doses during WBI, an inhomogeneous phantom of human head was used. Then, the eyes and lenses doses in the presence and absence of shield were measured by EBT3 film.

Results: In single fraction with 200 cGy to reference point, average doses received by the left and right eyes in the absence of shield were 20 ± 1.5 and 22 ± 1.0 cGy, respectively, and for the left and right eyes in the presence of shield were 18 ± 2.2 and 21 ± 2 cGy, respectively. In addition, the average dose received by the left and right lenses in the absence of shield were 19.5 ± 0.5 and 18.5 ± 0.5 cGy, respectively, and for the left and right lenses in the presence of shield were 20.5 ± 1.5 and 19.5 ± 1.5 cGy, respectively. The results showed the TPS compared to the film underestimates doses for the eyes and lenses.

Conclusion: The average dose received by the eyes and lenses during WBI were estimated around 9-11% of prescribed dose. According to the results, there is probability of radiation-induced cataractogenesis during WBI. By investigating the effect of shield on the lenses and eyes doses, using shield during WBI is not recommended. In addition, the results showed dose calculation accuracy of the TPS for the estimation of doses received by the eyes and lenses during WBI is not acceptable.
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http://dx.doi.org/10.4103/0973-1482.191056DOI Listing
November 2019

Melatonin Modulates Regulation of NOX2 and NOX4 Following Irradiation in the Lung.

Curr Clin Pharmacol 2019 ;14(3):224-231

Department of Physiology, College of Medicine, University of Misan, Misan, Iraq.

Background: Exposure to ionizing radiation may lead to chronic upregulation of inflammatory mediators and pro-oxidant enzymes, which give rise to continuous production of reactive oxygen species (ROS). NADPH oxidases are among the most important ROS producing enzymes. Their upregulation is associated with DNA damage and genomic instability. In the present study, we sought to determine the expressions of NADPH oxidases; NOX2 and NOX4, in rat's lung following whole body or pelvis irradiation. In addition, we evaluated the protective effect of melatonin on the expressions of NOX2 and NOX4, as well as oxidative DNA injury.

Methods: 35 male rats were divided into 7 groups, G1: control; G2: melatonin (100 mg/kg) treatment; G3: whole body irradiation (2 Gy); G4: melatonin plus whole body irradiation; G5: local irradiation to pelvis area; G6: melatonin treatment plus 2 Gy gamma rays to pelvis area; G7: scatter group. All the rats were sacrificed after 24 h. afterwards, the expressions of TGFβR1, Smad2, NF- κB, NOX2 and NOX4 were detected using real-time PCR. Also, the level of 8-OHdG was detected by ELISA, and NOX2 and NOX4 protein levels were detected by western blot.

Results: Whole body irradiation led to the upregulation of all genes, while local pelvis irradiation caused upregulation of TGFβR1, NF-κB, NOX2 and NOX4, as well as protein levels of NOX2 and NOX4. Treatment with melatonin reduced the expressions of these genes and also alleviated oxidative injury in both targeted and non-targeted lung tissues. Results also showed no significant reduction for NOX2 and NOX4 in bystander tissues following melatonin treatment.

Conclusion: It is possible that upregulation of NOX2 and NOX4 is involved in radiation-induced targeted and non-targeted lung injury. Melatonin may reduce oxidative stress following upregulation of these enzymes in directly irradiated lung tissues but not for bystander.
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http://dx.doi.org/10.2174/1574884714666190502151733DOI Listing
August 2020

Comparison of thermoluminescent dosimeter calibration irradiated in gamma knife and Co instruments.

J Cancer Res Ther 2019 Mar;15(Supplement):S123-S126

Department of Medical Physics and Medical Engineering, Tehran University of Medical Sciences, Tehran, Iran.

Aim: By necessity of dosimeters calibration for evaluating delivered dose accuracy to organs out of the radiation field in patients undergoing gamma knife radiosurgery, we calibrated thermoluminescence dosimeters in gamma knife and Co instruments, and then, compared both results to investigate when one of these devices was out of reach, can we use one of this instruments instead of the ther.

Materials And Methods: To individual calibration by Co, thermoluminescent dosimeters (TLDs) were placed in a Perspex sheet with conditions of source-skin distance = 80 cm, field size = 10 cm × 10 cm, and dose = 100 cGy. For individual calibration by Gamma knife, TLDs placed in flat Perspex were located in a special sphere and were exposed with conditions of source to axis distance = 40 cm, field size = 18 mm, and dose = 100 cGy, and for group calibration, TLDs were divided into six groups and were exposed with doses of 0-1000 cGy in both devices.

Results: According to Fisher's exact test, calculated P = 0.27, so the difference is not significant.

Conclusions: The result showed despite differences in calibration conditions, Co unit can be used to calibrate TLD dosimeter for estimating the accuracy of measurement of delivered dose to organs of patients undergoing Gamma Knife 4C radiosurgery treatment.
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http://dx.doi.org/10.4103/jcrt.JCRT_1200_16DOI Listing
March 2019

A systematic review of clinical applications of polymer gel dosimeters in radiotherapy.

Appl Radiat Isot 2019 Jan 23;143:47-59. Epub 2018 Aug 23.

Physics Department, Imam Khomeini International University, Qazvin, Iran. Electronic address:

Radiotherapy has rapidly improved because of the use of new equipment and techniques. Hence, the appeal for a feasible and accurate three-dimensional (3D) dosimetry system has increased. In this regard, gel dosimetry systems are accurate 3D dosimeters with high resolution. This systematic review evaluates the clinical applications of polymer gel dosimeters in radiotherapy. To find the clinical applications of polymer gel dosimeters in radiotherapy, a full systematic literature search was performed on the basis of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines in electronic databases up to January 31, 2017, with use of search-related terms in the titles and abstracts of articles. A total of 765 articles were screened in accordance with our inclusion and exclusion criteria. Eventually, 53 articles were included in the study. The findings show that most clinical applications of polymer gel dosimeters relate to external radiotherapy. Most of the gel dosimeters studied have acceptable dose accuracy as a 3D dosimeter with high resolution. It is difficult to judge which is the best polymer gel dosimeter to use in a clinical setting, because each gel dosimeter has advantages and limitations. For example, methacrylic acid-based gel dosimeters have high dose sensitivity and low toxicity, while their dose response is beam energy dependent; in contrast, N-isopropylacrylamide gel dosimeters have low dose resolution, but their sensitivity is lower and they are relatively toxic.
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http://dx.doi.org/10.1016/j.apradiso.2018.08.018DOI Listing
January 2019

Incidence and Mortality of Various Cancers in Iran and Compare to Other Countries: A Review Article.

Iran J Public Health 2018 Mar;47(3):309-316

Dept. of Epidemiology and Reproductive Health, Reproductive Epidemiology Research Center, Royan Institute for Reproductive Biomedicine, ACECR, Tehran, Iran.

Background: Iran in recent years had the rapid development of industrialization and modernity, and changes in the people's lifestyles and environment, these changes may affect epidemiological patterns of various types of cancers. In this review, incidence and mortality of various cancers (skin, gastric, esophageal, breast, and prostate) in Iran have been reported.

Methods: The related data about Iran and other countries were collected from databases such as Google Scholar, Scopus, PubMed, EMBASE, and Web of Science. All included studies were published before Jun 2017.

Results: There is an increment trend of incidence and mortality rate for most cancers in Iran.

Conclusion: The plan for control and prevention of cancers must be a high priority for health policy in Iran as well as it is suggested that earlier screening is need for high-risk population.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5971166PMC
March 2018

Mechanisms of inflammatory responses to radiation and normal tissues toxicity: clinical implications.

Int J Radiat Biol 2018 04 7;94(4):335-356. Epub 2018 Mar 7.

d Department of Medical Physics, School of Medicine , Iran University of Medical Sciences , Tehran , Iran.

Purpose: Cancer treatment is one of the most challenging diseases in the present era. Among a few modalities for cancer therapy, radiotherapy plays a pivotal role in more than half of all treatments alone or combined with other cancer treatment modalities. Management of normal tissue toxicity induced by radiation is one of the most important limiting factors for an appropriate radiation treatment course. The evaluation of mechanisms of normal tissue toxicity has shown that immune responses especially inflammatory responses play a key role in both early and late side effects of exposure to ionizing radiation (IR). DNA damage and cell death, as well as damage to some organelles such as mitochondria initiate several signaling pathways that result in the response of immune cells. Massive cell damage which is a common phenomenon following exposure to a high dose of IR cause secretion of a lot of inflammatory mediators including cytokines and chemokines. These mediators initiate different changes in normal tissues that may continue for a long time after irradiation. In this study, we reviewed the mechanisms of inflammatory responses to IR that are involved in normal tissue toxicity and considered as the most important limiting factors in radiotherapy. Also, we introduced some agents that have been proposed for management of these responses.

Conclusions: The early inflammation during the radiation treatment is often a limiting factor in radiotherapy. In addition to the limiting factors, chronic inflammatory responses may increase the risk of second primary cancers through continuous free radical production, attenuation of tumor suppressor genes, and activation of oncogenes. Moreover, these effects may influence non-irradiated tissues through a mechanism named bystander effect.
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http://dx.doi.org/10.1080/09553002.2018.1440092DOI Listing
April 2018

Metformin: Prevention of genomic instability and cancer: A review.

Mutat Res Genet Toxicol Environ Mutagen 2018 Mar 31;827:1-8. Epub 2018 Jan 31.

Department of Medical Physics and Biomedical Engineering, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran.

The diabetes drug metformin can mitigate the genotoxic effects of cytotoxic agents and has been proposed to prevent or even cure certain cancers. Metformin reduces DNA damage by mechanisms that are only incompletely understood. Metformin scavenges free radicals, including reactive oxygen species and nitric oxide, which are produced by genotoxicants such as ionizing or non-ionizing radiation, heavy metals, and chemotherapeutic agents. The drug may also increase the activities of antioxidant enzymes and inhibit NADPH oxidase, cyclooxygenase-2, and inducible nitric oxide synthase, thereby limiting macrophage recruitment and inflammatory responses. Metformin stimulates the DNA damage response (DDR) in the homologous end-joining, homologous recombination, and nucleotide excision repair pathways. This review focuses on the protective properties of metformin against genomic instability.
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http://dx.doi.org/10.1016/j.mrgentox.2018.01.007DOI Listing
March 2018

Gamma Knife Radiosurgery for Cavernous Sinus Meningiomas: Analysis of Outcome in 166 Patients.

Stereotact Funct Neurosurg 2017 11;95(4):259-267. Epub 2017 Aug 11.

Skull Base Research Center, Hazrat Rasoul Akram Hospital, Iran University of Medical Sciences, Tehran, Iran.

Objectives: The outcomes of Gamma Knife radiosurgery (GKRS) for cavernous sinus meningioma (CSM) are presented, and factors possibly affecting outcome are investigated.

Methods: The medical records and imaging and procedural reports of 166 patients with CSM were retrospectively reviewed. Demographic data, procedural data, symptomatic improvement, radiological regression, and progression-free survival (PFS) rates were evaluated.

Results: There were 124 women and 42 men; including 44 postoperative and 122 primary GKRS cases. Mean follow-up was 32.4 months. Mean marginal dose was 13 Gy. Symptomatic improvement was seen in 40.4%, while neurologic deterioration occurred in 9.6%; 50% remained symptomatically stable. Radiological regression was noted in 57.2%; the tumor remained stable in 35.5%, and 7.2% of the patients experienced tumor progression. The actuarial 5- and 10-year PFS rates were 90.1% (±3.3) and 75.8% (±8.8), respectively. History of previous surgery or radiotherapy were associated with lower symptomatic improvement. Higher tumor coverage and isodose lines were accompanied with better radiological prognosis. However, a history of conventional radiotherapy, presence of facial sensory deficits at presentation, a higher tumor volume, and tumor extension to the suprasellar compartment affected the radiologic outcome negatively.

Conclusion: This study revealed a high efficacy and safety for GKRS in both postoperative and primary GKRS patients. Achievability of a good profile of tumor coverage and isodose lines at radiosurgical planning predict a better outcome.
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http://dx.doi.org/10.1159/000478024DOI Listing
August 2018

Technical Note: Construction of heterogeneous head phantom for quality control in stereotactic radiosurgery.

Med Phys 2017 Oct 31;44(10):5070-5074. Epub 2017 Aug 31.

Young Researchers and Elites Club, Science and Research Branch, Islamic Azad University, Tehran, Iran.

Purpose: Stereotactic radiosurgery is a high precision modality for conformally delivering high doses of radiation to the brain lesion with a large dose volume. Several studies for the quality control of this technique were performed to measure the dose delivered to the target with a homogenous head phantom and some dosimeters. Some studies were also performed with one or two instances of heterogeneity in the head phantom to measure the dose delivered to the target. But these studies assumed the head as a sphere and simple shape heterogeneity. The construction of an adult human head phantom with the same size, shape, and real inhomogeneity as an adult human head is needed. Only then is measuring the accurate dose delivered to the area of interest and comparison with the calculated dose possible.

Methods: According to the ICRU Report 44, polytetrafluoroethylene (PTFE) and methyl methacrylate were selected as a bone and soft tissue, respectively. A set of computed tomography (CT) scans from a standard human head were taken, and simplification of the CT images was used to design the layers of the phantom. The parts of each slice were cut and attached together. Tests of density and CT number were done to compare the material of the phantom with tissues of the head. The dose delivered to the target was measured with an EBT3 film.

Results: The density of the PTFE and Plexiglas that were inserted in the phantom are in good agreement with bone and soft tissue. Also, the CT numbers of these materials have a low difference. The dose distribution from the EBT3 film and the treatment planning system is similar.

Conclusions: The constructed phantom with a size and inhomogeneity like an adult human head is suitable to measure the dose delivered to the area of interest. It also helps make an accurate comparison with the calculated dose by the treatment planning system. By using this phantom, the actual dose delivered to the target was obtained. This anthropomorphic head phantom can be used in other modalities of radiosurgery as well.
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http://dx.doi.org/10.1002/mp.12496DOI Listing
October 2017

Dosimetric characteristic of physical wedge versus enhanced dynamic wedge based on Monte Carlo simulations.

J Cancer Res Ther 2017 Apr-Jun;13(2):313-317

Department of Medical Physics and Medical Engineering, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran.

Aim Of Study: Physical wedges (PWs) are widely used in radiotherapy to obtain tilted isodose curves, but they alter beam quality. Dynamic wedges (DWs) using moving collimator overcome this problem, but measuring their beam data is not simple. The main aim of this study is to obtain all dosimetric parameters of DWs produced by Varian 2100CD with Monte Carlo simulation and compare them to those from PWs.

Subjects And Methods: To simulate 6 MV photon beams equipped with PW and DW, BEAMnrc code was used. All dosimetric data were obtained with EDR2 films and two-dimensional diode array detector.

Results: Good agreement between simulated and measured dosimetric data for PW and DW fields was obtained. Our results showed that percentage depth dose and beam profiles at nonwedged direction for DWs are the same as open fields and can be used to each other.

Conclusion: From Monte Carlo simulations, it can be concluded that DWs in spite of PW do not have effect on beam quality and are good options for treatment planning system which cannot consider hardening effect produced by PWs. Furthermore, BEAMnrc is a powerful code to acquire all date required by DWs.
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http://dx.doi.org/10.4103/0973-1482.183562DOI Listing
April 2018

Analysis of Gafchromic EBT3 film calibration irradiated with gamma rays from different systems: Gamma Knife and Cobalt-60 unit.

Med Dosim 2017 Autumn;42(3):159-168. Epub 2017 May 17.

Iran Gamma Knife Center, Tehran, Iran.

In recent years, Gafchromic films are used as an advanced instrument for dosimetry systems. The EBT3 films are a new generation of Gafchromic films. Our main interest is to compare the response of the EBT3 films exposed to gamma rays provided by the Theratron 780C as a conventional radiotherapy system and the Leksell Gamma Knife as a stereotactic radiotherapy system (SRS). Both systems use Cobalt-60 sources, thus using the same energy. However, other factors such as source-to-axis distance, number of sources, dose rate, direction of irradiation, shape of phantom, the field shape of radiation, and different scatter contribution may influence the calibration curve. Calibration curves for the 2 systems were measured and plotted for doses ranging from 0 to 40 Gy at the red and green channels. The best fitting curve was obtained with the Levenberg-Marquardt algorithm. Also, the component of dose uncertainty was obtained for any calibration curve. With the best fitting curve for the EBT3 films, we can use the calibration curve to measure the absolute dose in radiation therapy. Although there is a small deviation between the 2 curves, the p-value at any channel shows no significant difference between the 2 calibration curves. Therefore, the calibration curve for each system can be the same because of minor differences. The results show that with the best fitting curve from measured data, while considering the measurement uncertainties related to them, the EBT3 calibration curve can be used to measure the unknown dose both in SRS and in conventional radiotherapy.
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http://dx.doi.org/10.1016/j.meddos.2017.01.003DOI Listing
May 2018

Comparison of beam hardening effect of physical and enhanced dynamic wedges at bladder inhomogeneity using EBT3 film dosimeter.

J Cancer Res Ther 2017 Jan-Mar;13(1):97-101

Department of Radiotherapy, Shohada Tajrish Hospital, Shahid Beheshti University of Medical Science, Tehran, Iran.

Introduction: Using physical wedges (PWs) to modify dose distribution and more homogeneous target coverage is a well-established technique. However, there are many problems with PWs known as beam hardening, which made them problematic. This can be overcome by dynamic wedges which do not filter beam. Comparison of physical properties of physical and enhanced dynamic wedges (EDWs) restricted to homogeneous medium. Hence, the main aim of this study is to compare dosimetric properties of physical and EDWs at bladder inhomogeneous phantom as a most common case implementing wedges.

Materials And Methods: An inhomogeneous pelvic phantom with homogeneities of uterus, femur, soft tissue, rectum, and bladder was designed. Eclipse treatment planning system with the aim of bladder target was used for calculations. All dose distributions were measured with EBT3 films.

Results: Comparison between beam profiles of physical and EDWs at wedged and nonwedged directions shows a greater difference at near inhomogeneous soft tissue interface and also at heel side of wedges.

Conclusion: Little difference observed between dose distribution of physical and EDWs shows neglectable effect of beam hardening produced by PW compared to EDW at inhomogeneous medium. Furthermore, EBT3 films present good feature to measure dose distributions at EDW fields.
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http://dx.doi.org/10.4103/0973-1482.206244DOI Listing
February 2018
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