اساتید - دانشکده پزشکی دانشگاه علوم پزشكي و خدمات بهداشتی درمانی تبريز

دانشکده پزشکی دانشگاه علوم پزشكي و خدمات بهداشتی درمانی تبريز - اصغر مصباحي

اصغر مصباحي

فیزیک پزشکی

درجه علمی : استاد

تحصیلات : Ph.D

رشته تحصیلی : فیزیک پزشکی

محل تحصیل : دانشگاه علوم پزشکی تهران

تلفن : 33364660

توضیحات :

آدرس پست الکترونیکی : amesbahi2010@gmail.com

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عنوان مقاله : Experimental evaluation of ALFARD treatment planning system for 6 MV photon irradiation: A lung case study

نویسنده رابط : Asghar mesbahi

عنوان مجله و شماره مجله : Reports of Practical Oncology and Radiotherapy [Internet]. 2004;9(6):217-21.

نویسندگان : Mesbahi A, Allahverdi M, Gheraati H, Mohammadi E

سال انتشار : 2004

چکیده : Purpose: Simple inhomogeneity correction methods available in a number of currently applied treatment planning systems are not accurate enough for dose calculations in lung irradiations. The purpose of this study was to evaluate the accuracy of the ALFARD treatment planning system in dose calculations for lung irradiation. Material and methods: An anatomic thorax phantom and a 6 MV photon beam were used for our irradiation. Our set-up consisted of an anterior single field for the left lung of a thorax phantom with field sizes of 5 +ù 5 cm² and 10 +ù 10 cm². The percentage depth doses for each point in the lung were measured by a Pinpoint ionization chamber and calculated by the ALFARD treatment planning system. The results of calculations and measurements were compared. Results: The ALFARD calculations overestimated measurements at all points and field sizes. The magnitude of error increased with depth of the calculation point from 2.7% to 17.3% for the field size of 5 +ù 5 cm². The error for 5 +ù 5 cm² was approximately twice as high as that for 10 +ù 10 cm². Conclusions: The ALFARD treatment planning system cannot calculate the dose in the lung accurately. This may be due to inherent deficiencies of the effective path length method, which is implemented in the ALFARD treatment planning system

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عنوان مقاله : Monte carlo calculation of varian 2300C/D linac photon beam characteristics: A comparison between MCNP4C, GEANT3 and measurements

نویسنده رابط : Asghar mesbahi

عنوان مجله و شماره مجله : Applied Radiation and Isotopes [Internet]. 2005;62(3):469-77

نویسندگان : Mesbahi A, Fix M, Allahverdi M, Grein E, Garaati H

سال انتشار : 2005

چکیده : Different codes are used for Monte Carlo (MC) calculations in radiation therapy. In this research, MCNP4C and GEANT3 codes have been compared in calculations of dosimetric characteristics of Varian Clinac 2300C/D. The parameters of influence in the differences seen in dosimetric features were discussed. This study emphasizes that both MCNP4C and GEANT3 MC can be used in radiation therapy computations and their differences in photon spectra calculations have a negligible effect on percentage depth dose computations in radiation therapy

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عنوان مقاله : Monte carlo dose calculations in conventional thorax fields for 60Co photons.

نویسنده رابط : Asghar mesbahi

عنوان مجله و شماره مجله : Radiation Medicine - Medical Imaging and Radiation Oncology [Internet]. 2005;23(5):341-50

نویسندگان : Mesbahi A, Allahverdi M, Gheraati H

سال انتشار : 2005

چکیده : Purpose: Our purpose was to apply the MCNP4C Monte Carlo (MC) code for dose calculations in the thorax region and compare the results with those of measurements and a conventional treatment planning system (TPS). Materials and Methods: We modeled a Theratron 780E ⁶⁰Co unit and benchmarked our modeling with percent depth doses (PDDs), beam profiles, and output factors measured in a water phantom. For PDDs and beam profiles, the differences between measurements and MC calculations were less than 1% and 2%, respectively. We used an anatomic thorax phantom for evaluation of a conventional TPS and our MC calculation results. Results: In comparing the results of calculations and measurements for our thorax geometries, the errors of conventional and MC methods were 20% and 2%, respectively. For the anterior mediastinal field and large thorax field the accuracy of the conventional method was acceptable, but for small fields of lateral thorax irradiation, the error of the conventional method was as high as to 20%. In all MC calculations, discrepancy from the measurements was less than 2%. Conclusion: Our results showed that the MCNP4C MC code could be used in dose calculations in treatment planning for ⁶⁰Co photon irradiation. In addition, the application of the MC method for dose calculations in radiotherapy with ⁶⁰Co photons was recommended

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عنوان مقاله : Monte carlo dose calculations for a 6-MV photon beam in a thorax phantom.

نویسنده رابط : Asghar mesbahi

عنوان مجله و شماره مجله : Radiation Medicine - Medical Imaging and Radiation Oncology [Internet]. 2006;24(4):269-76

نویسندگان : Farajollahi A, Mesbahi A

سال انتشار : 2006

چکیده : Purpose. In this study we evaluated the accuracy of the Monte Carlo (MC) and effective path length (EPL) methods for dose calculations in the inhomogeneous thorax phantom. Materials and methods. The Philips SL 75/5 linear accelerator head was modeled using the MCNP4C Monte Carlo code. An anatomic inhomogeneous thorax phantom was irradiated with a 6-MV photon beam, and the doses along points of the central axis of the beam were measured by a small ionization chamber. The central axis relative dose was calculated by the MCNP4C code and the EPL method in a conventional treatment planning system. The results of calculations and measurements were compared. Results. For all measured points on the thorax phantom the results of the MC method were in agreement with the actual measurement (local difference was less than 2%). For the EPL method, the amount of error was dependent on the field size and the point location in the phantom. The maximum error was +19.5 and +26.8 for field sizes of 10 +ù 10 and 5 +ù 5 cm² for lateral irradiation. Conclusion. Our study showed large, unacceptable errors for EPL calculations in the lung for both field sizes. The accuracy of the MC method was better than the recommended value of 3%. Thus, application of this method is strongly recommended for lung dose calculations, especially for small field sizes

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عنوان مقاله : Development and commissioning of a monte carlo photon beam model for varian clinac 2100EX linear accelerator

نویسنده رابط : asghar mesbahi

عنوان مجله و شماره مجله : Applied Radiation and Isotopes [Internet]. 2006;64(6):656-62.

نویسندگان : Mesbahi A, Reilly AJ, Thwaites DI

سال انتشار : 2006

چکیده : Monte Carlo modeling of a linear accelerator is the first and most important step in Monte Carlo dose calculations in radiotherapy. We developed a photon beam model for Varian 2100EX for dose calculation purposes using MCNP4C Monte Carlo code. Results of our modeling were in close agreement with our measurements. The effect of beam width on percentage depth doses and beam profiles was studied. Our results showed that electron beam width could be tuned using large field beam profile at the depth of maximum dose

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عنوان مقاله : Dosimetric properties of a flattening filter-free 6-MV photon beam: A monte carlo study

نویسنده رابط : asghar mesbahi

عنوان مجله و شماره مجله : Radiation Medicine - Medical Imaging and Radiation Oncology [Internet]. 2007;25(7):315-24.

نویسندگان : Mesbahi A, Mehnati P, Keshtkar A, Farajollahi A

سال انتشار : 2007

چکیده : Abstract Purpose. The dosimetric features of an unﬂ attened 6-MV photon beam of an Elekta SL-25 linac was calculated by the Monte Carlo (MC) method. Material and methods. The head of the Elekta SL-25 linac was simulated using the MCNP4C MC code. The accuracy of the model was evaluated using measured dosimetric features, including depth dose values and dose proﬁ les in a water phantom. The ﬂ attening ﬁ lter was then removed, and beam dosimetric properties were calculated by the MC method and compared with those of the ﬂ attened photon beam. Results. Our results showed a signiﬁ cant (twofold) increase in the dose rate for all ﬁ eld sizes. Also, the photon beam spectra for an unﬂ attened beam were softer, which led to a steeper reduction in depth doses. The decrease in the out-of-ﬁ eld dose and increase in the contamination electrons and a buildup region dose were the other consequences of removing the ﬂ attening ﬁ lter. Conclusion. Our study revealed that, for recent radio- therapy techniques, the use of multileaf collimators for beam shaping removing the ﬂ attening ﬁ lter could offer some advantages, including an increased dose rate and decreased out-of-ﬁ eld dose.

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عنوان مقاله : Monte carlo study on the impact of spinal fixation rods on dose distribution in photon beams

نویسنده رابط : asghar mesbahi

عنوان مجله و شماره مجله : . Reports of Practical Oncology and Radiotherapy [Internet]. 2007;12(5):261-6.

نویسندگان : Mesbahi A, Nejad FS

سال انتشار : 2007

چکیده : Background Metal spinal rods are used as ﬁ xation devices in spinal surgery. The attenuation effect of these rods has not been completely studied for patients with spinal rods and requiring spinal radiotherapy. Aim The purpose of the current study was to investigate the dosimetric perturbation effect of metallic spinal rods in different photon beams. Materials/Methods Three photon beams of 6, 9 and 15MV were modelled using MCNP4C Monte Carlo (MC) code. The geometry consisted of two spinal rods at a depth of 4cm and a water phantom was used for MC calculations. The beam proﬁ les at depths of 5.5, 6.5 and 7.5cm were calculated. Results Dose reductions of 10.2–11.2% and 5–6.2% were observed for steel and titani- um rods respectively. The insertion of metallic rods into the photon beams did not change the spinal cord received dose but the effect of both types of rods on the target region behind the rods cannot be ignored, especially for steel rods. Conclusions Our results suggest that for reliable spinal radiotherapy the dose attenuation ef- fect of spinal rods must be taken into account in treatment planning calcula- tions.

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عنوان مقاله : Monte carlo study on the impact of spinal fixation rods on dose distribution in photon beams

نویسنده رابط : asghar mesbahi

عنوان مجله و شماره مجله : . Reports of Practical Oncology and Radiotherapy [Internet]. 2007;12(5):261-6.

نویسندگان : Mesbahi A, Nejad FS

سال انتشار : 2007

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عنوان مقاله : . Monte carlo simulation of TLD response function: Scattered radiation field application

نویسنده رابط : Dr. Shirazi

عنوان مجله و شماره مجله : . Reports of Practical Oncology and Radiotherapy [Internet]. 2008;13(1):23-8.

نویسندگان : Shirazi A, Mahdavi SR, Khodadadee A, Ghaffory M, Mesbahi A

سال انتشار : 2008

چکیده : Thermoluminescent dosimeters (TLDs) have various applications in non-primary beam dosimetry. Monte Carlo simulation of TLD response was done in low energy beams to improve its clinical use in scattered beam dosimetry. Materials/Methods TLD material made from LiF doped with Mg and Ti sized 3.1×3.1×1mm3 was used for experimental measurements as well as modelling by MCNP-4c Monte Carlo simulation. TLDs were irradiated for different doses of beam qualities ranging from 120, 180, 200, 250 to 300kVp x-rays generated from an orthovoltage machine and 1.25MeV gamma rays from a Co-60 teletherapy unit at reference depth in a water phantom. The simulation conditions were the same as experimental conditions. The calibration factor, (CF)q, and its quality dependence factor, (F X Co), were defi ned as: (CF)q = Calibration Dose/TL, (F X Co) = TL(X)/Dmed (X) TL(X)/Dmed (Co) Results The normalized values of measured quality dependence factors for different x-ray beams were 1.28, 1.24, 1.16, 1.07 and 1.03 for different beam qualities, respectively. Comparatively, the MCNP simulated fi ndings were 1.134, 1.96, 1.139, 1.052 and 1.034. The change of calibration factor with energy followed the equation CF=B0+B1E+B2E2+B3E3, where CF and E are calibration factor and energy (keV), respectively. B0, B1, B2, B3 are constants. Conclusions Our fi ndings showed signifi cant deviation of true dose value when TLDs are calibrated at different beam qualities. The greatest deviation was 19.9±2.1% in beam quality of 120kVp. Obtaining a dose response curve may be helpful to calculate the calibration factor with more precision.

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عنوان مقاله : . A comparative monte carlo study on 6MV photon beam characteristics of varian 21EX and elekta SL-25 linacs

نویسنده رابط : Asghar mesbahi

عنوان مجله و شماره مجله : Iranian Journal of Radiation Research [Internet]. 2007;5(1):23-30.

نویسندگان : Mesbahi A, Mehnati P, Keshtkar A

سال انتشار : 2007

چکیده : Background: Monte Carlo method (MC) has played an important role in design and optimization of medical linacs head and beam modeling. The purpose of this study was to compare photon beam features of two commercial linacs, Varian 21EX and Elekta SL-25 using MCNP4C MC code. Materials and Methods: The 6MV photon beams of Varian 21EX and Elekta Sl- 25 linacs were simulated based on manufacturers provided information. Photon energy spectra and absolute absorbed dose values were calculated for field sizes of 10×10 and 20×20 cm2. Also, contamination electron spectra for field size of 20 ×20 cm2 were scored for both linacs. Results: Our results showed that the relative absorbed dose values and contamination electron spectrum were similar and comparable, but photon fluence and absolute absorbed dose values were 17% and 13% higher for Varian linac respectively for the field size of 10×10 cm2. Conclusion: Despite the differences in head components of two commercial linacs, their relative depth dose values were very close to each other. The absolute dose per incident electron showed some discrepancy, as well. Thus, this study suggests the use of absolute absorbed dose values as an invaluable factor when different linacs head are compared using Monte Carlo Method. Iran. J. Radiat. Res., 2007; 5 (1):

عنوان مقاله : Track detection on the cells exposed to high LET heavy-ions by CR-39 plastic and terminal deoxynucleotidyl transferase (TdT).

نویسنده رابط : Dr. Mehnati

عنوان مجله و شماره مجله : Iranian Journal of Radiation Research [Internet]. 2006;4(3):137-41.

نویسندگان : Mehnati P, Keshtkar A, Mesbahi A, Sasaki H

سال انتشار : 2006

چکیده : Background: The fatal effect of ionizing radiation on cells depends on Linear Energy Transfer (LET) level. The distribution of ionizing radiation is sparse and homogeneous for low LET radiations such as X or |γ, but it is dense and concentrated for high LET radiation such as heavy-ions radiation. Materials and Methods: Chinese hamster ovary cells (CHO-K1) were exposed to 4 Gy Fe-ion 2000 keV/|μ|m. The CR-39 is a special and sensitive plastic used to verify exact position of heavy-ions traversal. Terminal deoxynucleotidyl transferase (TdT) is an enzyme labeled with [3H] dATP for detection of cellular DNA damage by autoradiography assay. Results: The track of heavy ions traversals presented by pit size was almost similar for all different doses of radiation. No pits to show the track of traversal were found in 20% of the cell nuclei of the irradiation. Apparently these fractions of cells wave not hit by heavy ions. Conclusion: This study indicated the possible usefulness of both the CR-39 plastics and DNA labeling with TdT method for evaluating the biological effect of heavy-ions in comparison with low LET ionizing radiation. Iran. J. Radiat. Res., 2006; 4 (3): 137- 141 Keywords: Track detector, heavy ions, CR-39 plastic,

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عنوان مقاله : Dosimetric characteristics of unflattened 6 MV photon beams of a clinical linear accelerator: A monte carlo study

نویسنده رابط : Asghar Mesbahi

عنوان مجله و شماره مجله : Applied Radiation and Isotopes [Internet]. 2007;65(9):1029-36.

نویسندگان : Asghar Mesbahi

سال انتشار : 2007

چکیده : The purpose of this study is to evaluate the dosimetric properties of a flattening filter free 6MV photon beam. The 6MV photon beam of a Varian Clinac 21EX linac was modeled using the MCNP4C Monte Carlo (MC) code. Dosimetric features including central axis absorbed doses, beam profiles and photon energy spectra were calculated for flattened and unflattened 6MV photon beams. A substantial increase in the dose rate was seen for the unflattened beam, which was decreased with field size and depth. The penumbra width was decreased less than 0.2mm (about 5%) and a 25% decrease in out-of-field dose was observed for the unflattened beam. The photon energy spectra were softer for the unflattened beam and the mean energies of spectra were higher for smaller field size. Our study showed that increase in the dose rate and lower out-of-field dose could be considered as practical advantages for unflattened 6MV beams.

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عنوان مقاله : The effect of bladder volume changes on the measured electrical impedance of the urothelium

نویسنده رابط : asghar mesbahi

عنوان مجله و شماره مجله : International Journal of Biomedical Engineering and Technology [Internet]. 2008;1:287-92.

نویسندگان : 35. Keshtkar A, Mesbahi A, Mehnati P

سال انتشار : 2008

چکیده : Abstract: The bio-impedance of the urinary bladder in both benign and malignant areas can be measured using the electrical impedance spectroscopy system. In this procedure, the bladder volume changes using some liquids which were expected to affect the resulting electrical impedance of the urinary bladder (in vivo and ex vivo). Different volumes of bladders were assessed to measure their impedance using different solutions. The solution volume was changed and repeated readings were made for different volumes. Despite the measured impedance demonstrated no significant relation between the impedance and the degree of the bladder existed, but there was a little dependence between them.

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عنوان مقاله : In-air calibration of new high dose rate 60Co brachytherapy sources: Results of measurements on a GZP6 brachytherapy afterloading unit

نویسنده رابط : Asghar Mesbahi

عنوان مجله و شماره مجله : Reports of Practical Oncology and Radiotherapy [Internet]. 2008;13(2):69-73.

نویسندگان : Mesbahi A, Naseri A

سال انتشار : 2008

چکیده : SUMMARY BACKGROUND: The air kerma rate of brachytherapy sources should be determined accurately by the manufacturer and medical physicists before clinical use. AIM: In the current study the air kerma rate of three new 60Co high dose rate (HDR) brachytherapy sources was obtained by in-air measurements and a Farmer type ionization chamber. MATERIALS/METHODS: Three 60Co sources of a brachytherapy afterloading unit, GZP6, were calibrated in free air using a Farmer type chamber which was calibrated in terms of air kerma in an external teletherapy 60Co beam. Several correction factors including scatter correction and non-uniformity correction factors were derived and used for in-air calibrations. RESULTS: The measured air kerma rates for all sources were in good agreement (less than 2.5%) with manufacturer-provided data, and the reliability of the air kerma rates of sources was validated for clinical application. CONCLUSION: In-air calibration of 60Co HDR sources can be performed using a Farmer type ionization chamber with acceptable accuracy. However, accurate distance measurement and reproducible measurement setup are required.

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عنوان مقاله : Monte carlo study on a flattening filter-free 18-MV photon beam of a medical linear accelerator

نویسنده رابط : Asghar Mesbahi

عنوان مجله و شماره مجله : Radiation Medicine - Medical Imaging and Radiation Oncology [Internet]. 2008;26(6):331-6

نویسندگان : Mesbahi A, Nejad FS

سال انتشار : 2008

چکیده : Monte Carlo study on a fl attening fi lter-free 18-MV photon beam of a medical linear accelerator

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عنوان مقاله : A study on the impact of operator experience on the patient radiation exposure in coronary angiography examinations

نویسنده رابط : Asghar Mesbahi

عنوان مجله و شماره مجله : Radiat Prot Dosimet [Internet]. 2008;132(3):319-23.

نویسندگان : Mesbahi A, Aslanabadi N, Mehnati P.

سال انتشار : 2008

چکیده : The aim of the current study was to investigate the effect of cardiologists’ experience on the patient received dose during coronary angiography. The exposure parameters including fluoroscopy time, total kerma-area product (KAP), total air-kerma, fluoroscopy and cine acquisition KAP and air-kerma for five senior cardiologists with the experience of 6–10 y were recorded. The range of values for fluoroscopy time and total KAP were 2.17– 4.19 min and 12.06–21.06 Gy cm2, respectively, in our diagnostic coronary examinations, which was below the recommended reference values. The differences among cardiologists were analysed statistically using one-way ANOVA test. The fluoroscopy KAP and air-kerma results showed statistically significant differences between cardiologists. However, the experience of the cardiologists showed no relation with patient received dose. According to the results, training in radiation protection as a requisite for interventional cardiologists was recommended.

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عنوان مقاله : Radial dose functions of GZP6 intracavitary brachytherapy 60Co sources: Treatment planning system versus monte carlo calculations

نویسنده رابط : Asghar Mesbahi

عنوان مجله و شماره مجله : Iranian Journal of Radiation Research [Internet]. 2008;5(4):181-6.

نویسندگان : Asghar Mesbahi

سال انتشار : 2008

چکیده : Background: The Monte Carlo (MC) method is not only used for dose calculations around brachytherapy sources but also for benchmarking treatment planning systems (TPS) calculations. Materials and Methods: Three 60Co sources of GZP6 brachytherapy unit were simulated using MCNP4C MC Code. The radial dose functions were calculated by MC method and GZP6 TPS and were compared. Results: There was a good agreement between MC and TPS calculations for all sources. Discrepancies up to 10% were observed for points close to the sources, but for those farther than 7mm from source center, differences were less than 2% for all sources. Conclusion: Our results showed that GZP6 TPS calculations can accurately be used for dose calculations in brachytherapy treatments for points farther than 7mm from the source center.

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عنوان مقاله : The effect of electronic disequilibrium on the received dose by lung in small fields with photon beams: Measurements and Monte Carlo study

نویسنده رابط : Asghar Mesbahi

عنوان مجله و شماره مجله : Iranian Journal of Radiation Research [Internet]. 2008;6(2):71-7.

نویسندگان : Asghar Mesbahi

سال انتشار : 2008

چکیده : Background: Prediction of the absorbed dose in irradiated volume plays an important role in the outcome of radiotherapy. Application of small fields for radiotherapy of thorax makes the dose calculation process inaccurate due to the existence of electronic disequilibrium and intrinsic deficiencies in dose calculation algorithms. To study the lung absorbed dose in radiotherapy with small fields, the central axis absorbed dose in heterogeneous thorax phantom was measured by ionization chamber and calculated for small fields by Monte Carlo (MC) method. Materials and Methods: A solid slab phantom consisting of unit and low density materials was used for dose measurements. The 6 and 18 MV photon beams of Elekta SL25 linac were simulated using MCNP4C MC Code. The model was validated by comparing the calculated depth dose and beam profiles with measurements in a water phantom. The MC model was used to calculate the depth doses in unit density and low density materials resembling the soft tissue and lung, respectively. Two small field sizes including 5×5 and 2×2 cm2 were used in this study. Results: The measured depth dose values were in good agreement with MC results and the difference less than 2% was observed. A large dose reduction was seen in lung for field size of 2×2 cm2 due to the lateral electronic disequilibrium and it reached up to 16.2% and 33.3% for 6 and 18 MV beams, respectively. Dose build up and down at material interfaces was predicted by MC method. Conclusion: Our study showed that the dose reductions with small fields in lung and dose variations at interfaces was very considerable, and inaccurate prediction of absorbed dose in lung using small fields and photon beams may lead to critical consequences for patients.

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عنوان مقاله : A study on patients' radiation doses from interventional cardiac procedures in tabriz, iran

نویسنده رابط : Asghar Mesbahi

عنوان مجله و شماره مجله : Radiat Prot Dosimet [Internet]. 2008;132(4):375-80

نویسندگان : Mesbahi A, Aslanabadi N

سال انتشار : 2008

چکیده : Interventional cardiac procedures produce a large amount of X-ray exposures to the patients in comparison with other conventional X-ray imaging procedures. In the current study, the exposure parameters of 580 patients referred to a cardiac angiography department were recorded. The mean values of total kerma–area product (KAP) were 18.6 Gy cm2 for coronary angiography (CA) and 55 Gy cm2 for percutaneous transluminal coronary angioplasty (PTCA). The mean fluoroscopy time was 3.2 and 11.6 min, respectively, for CA and PTCA. The patients’ exposure parameters during electrophysiological studies were 15.5 min for mean fluoroscopy time and 33.9 Gy cm2 for total KAP. For paediatrics, the mean fluoroscopy time of 5.4 min and total KAP of 2 Gy cm2 were recorded. Comparing the proposed reference values, the authors think that the exposure level of patients in their department is at an acceptable level.

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عنوان مقاله : Comparison of radiation dose to patient and staff for two interventional cardiology units: A phantom study

نویسنده رابط : Asghar Mesbahi

عنوان مجله و شماره مجله : Radiat Prot Dosimet [Internet]. 2008;131(3):399-403.

نویسندگان : Mesbahi A, Mehnati P, Keshtkar A, Aslanabadi N.

سال انتشار : 2008

چکیده : The purpose of this investigation was to measure the patient and staff dose during routine interventional cardiology procedures for an image intensifier-based and a flat detector system using a water phantom. The Integris BH3000 image intensifier-based (Philips) and the Axiom Artis flat detector-based (Siemens) angiography units were used in this study. The accuracy of tubes potential and irradiation timers and also internal dosimeters were verified and confirmed. A water phantom with a thickness of 18 cm was used for patient and staff dose measurements. For the Philips system, phantom entrance dose rates were 2.77 and 38.97 mGym2 s21 during fluoroscopy and cineangiography. The respective dose rates for the Siemens were 1.98 and 13.46 mGym2 s21. Phantom entrance dose rate was 28.5 and 65% higher for the Philips system during fluoroscopy and cineangiography, respectively. Comparing the scattered dose rates at the operator location showed that the flat detector-based Siemens system delivers five times lower dose to the operator in comparison with the image intensifier-based Philips unit. The results suggest that the decrease in received dose of the patient and staff is achievable using the flat detector system. In addition, application of lead curtain and glass is recommended to lower the cardiologist dose especially for the image intensifier- based Philips system.

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عنوان مقاله : A study on the radiation dose of the orthopaedic surgeon and staff from a mini c-arm fluoroscopy unit

نویسنده رابط : Asghar Mesbahi

عنوان مجله و شماره مجله : Radiat Prot Dosimet [Internet]. 2008;132(1):98-101

نویسندگان : Mesbahi A, Rouhani A

سال انتشار : 2008

چکیده : In this study, radiation exposure to the surgeon and supporting staff from a mini C-arm unit during fluoroscopically guided orthopaedic surgeries was studied. A Diadose dosemeter and Gamma-Scout meter were used for air-kerma measurements for primary and scattered radiations. The entrance dose of hands, eyes and thyroid of the surgeon was measured during direct observation. Scattered air-kerma rate was measured to quantify the received entrance dose of the supporting staff. During direct observation, the skin-entrance exposure rates of the surgeon’s hand, eye and thyroid gland were 8036, 0.85 and 0.9 mGy min21, respectively. The scattered exposure rate was precipitously dropped beyond the path of the primary radiation beam, and reached 0.51 mGy min21 at a distance of 40 cm from the beam’s central axis. This study showed that the surgeon’s hand was the most dose-limiting organ for fluoroscopically guided orthopaedic surgery procedures when it was exposed to primary radiation. The exposure of supporting staff at a working distance of >20 cm from the beam was minimal during fluoroscopy by mini C-arm unit.

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عنوان مقاله : A Monte Carlo study on neutron and electron contamination of an unflattened 18-MV photon beam

نویسنده رابط : Asgharmesbahi

عنوان مجله و شماره مجله : Applied Radiation and Isotopes [Internet]. 2009;67(1):55-60.

نویسندگان : Asghar Mesbahi

سال انتشار : 2009

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عنوان مقاله : Monte carlo estimation of photoneutrons contamination from high-energy X-ray medical accelerators in treatment room and maze: A simplified model.

نویسنده رابط : zabihzadeh

عنوان مجله و شماره مجله : Radiat Prot Dosimet [Internet]. 2009;135(1):21-32.

نویسندگان : Zabihzadeh M, Ay MR, Allahverdi M, Mesbahi A, Mahdavi SR, Shahriari M

سال انتشار : 2009

چکیده : Despite all advantages associated with high-energy radiotherapy to improve therapeutic gain, the production of photoneutron via interaction of high-energy photons with high atomic number (Z) materials increases undesired dose to the patient and staff. Owing to the limitation and complication of experimental neutron dosimetry in mixed beam environment, including photon and neutron, the Monte Carlo (MC) simulation is a gold standard method for calculation of photoneutron contaminations. On the other hand, the complexity of treatment head makes the MC simulation more difficult and time-consuming. In this study, the possibility of using a simplified MC model for the simulation of treatment head has been investigated using MCNP4C general purpose MC code. As a part of comparative assessment strategy, the fluence, average energy and dose equivalent of photoneutrons were estimated and compared with other studies for several fields and energies at different points in treatment room and maze. The mean energy of photoneutrons was 0.17, 0.19 and 0.2 MeV at the patient plan for 10, 15 and 18 MeV, respectively. The calculated values differed, respectively, by a factor of 1.4, 0.7 and 0.61 compared with the reported measured data for 10, 15 and 18 MeV. Our simulation results in the maze showed that the neutron dose equivalent is attenuated by a factor of 10 for every 4.6 m of maze length while the related factor from Kersey analytical method is 5 m. The neutron dose equivalent was 4.1 mSv Gy21 at the isocentre and decreased to 0.79 mSv Gy21 at a distance of 100 cm away from the isocentre for 40 3 40 cm2. There is good agreement between the data calculated using simplified model in this study and measurements. Considering the reported high uncertainties (up to 50%) in experimental neutron dosimetry, it can be concluded that the simplified model can be used as a useful tool for estimation of photoneutron contamination associated with high-energy photon radiotherapy.

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عنوان مقاله : The impact of automatic wedge filter on photoneutron and photon spectra of an 18-MV photon beam

نویسنده رابط : Asghar mesbahi

عنوان مجله و شماره مجله : Radiat Prot Dosimet [Internet]. 2009;138(2):123-8.

نویسندگان : Ghavami S-, Mesbahi A, Mohammadi E

سال انتشار : 2009

چکیده :

عنوان مقاله : Application of monte carlo calculations for validation of a treatment planning system in high dose rate brachytherapy

نویسنده رابط : Asghar Mesbahi

عنوان مجله و شماره مجله : Reports of Practical Oncology and Radiotherapy [Internet]. 2009;14(6):200-4.

نویسندگان : . Naseri A, Mesbahi A.

سال انتشار : 2009

چکیده : Application of Monte Carlo calculations for validation of a treatment planning system in high dose rate brachytherapy

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عنوان مقاله : Shielding evaluation of a typical radiography department: A comparison between NCRP reports no.49 and 147

نویسنده رابط : Asghar Mesbahi

عنوان مجله و شماره مجله : Iranian Journal of Radiation Research [Internet]. 2009;6(4):183-8.

نویسندگان : Pesianian I, Mesbahi A, Shafaee A.

سال انتشار : 2009

چکیده : Background: Designing and shielding of an appropriate radiography room has been one of the major concerns of radiation scientists since the first decade after the invention of X-rays. Recently, report No.147 of National Council on Radiation Protection and Measurements (NCRP) has been published. In this study the researchers have investigated the effect of new report recommendation on primary and secondary barriers thicknesses in comparison to NCRP 49, and 116 recommendations. Materials and Methods: To calculate the walls thickness of a conventional radiography room, the workload of a radiography room of a university hospital was determined by recording the number of exposures, mAs and kVp for each patient during six months. Three types of calculations were done: (1) Using NCRP 49 formulations and dose limits (2) Using the NCRP 49 formulations and NCRP116 dose limits and (3) Using the NCRP 147 recommendations. Results: The estimated workload was 172 mA min wk-1 for the studied radiography room which was slightly lower than the workload recommended by NCRP147. The results showed that using the NCRP49 formulation and NCRP116 dose limits, the barriers thickness increases substantially. Moreover, the dose limits were lower in NCRP 147, using the third method. The primary barrier thickness is decreased considerably in comparison to two other methods. For the secondary barrier the results of the two methods (1) and (3) did not differ and remained the same. Conclusion: Application of NCRP 49 and NCRP116 dose limits for radiography room shielding (second method) overestimated the primary and secondary barriers thickness, significantly. But, applying NCRP 147, not only the new dose limits were considered, but also the cost of primary barrier construction was reduced. Iran. J. Radiat. Res., 2009; 6 (4): 183188

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عنوان مقاله : The feasibility of computational modelling technique to detect the bladder cancer

نویسنده رابط : asghar mesbahi

عنوان مجله و شماره مجله : Physica Medica [Internet]. 2010;26(1):34-7.

نویسندگان : Keshtkar A, Mesbahi A, Rasta SH, Keshtkar A

سال انتشار : 2010

چکیده :

عنوان مقاله : Effect of wedge filter and field size on photoneutron dose equivalent for an 18 MV photon beam of a medical linear accelerator.

نویسنده رابط : asghar mesbahi

عنوان مجله و شماره مجله : Applied Radiation and Isotopes [Internet]. 2010;68(1):84-9

نویسندگان : Mesbahi A, Keshtkar A, Mohammadi E, Mohammadzadeh M

سال انتشار : 2010

چکیده : Photoneutrons produced during radiation therapy with high energy photons is the main source of unwanted out-of-field received doses of patients. To analyze the neutron dose equivalent (NDE) for wedged beams and its variation with field size, Monte Carlo (MC) modeling of an 18MV photon beam was performed using MCNPX MC code. The results revealed that the NDE is on average 6.5 times higher for wedged beams. For open beams, the NDE decreased with increasing field size especially for field sizes 42020cm2. While, for wedged beams, the NDE increased with field size. It was suggested that the increase of NDE for wedged beams should be taken into account in radiation-induced secondary cancer risk estimations and radiation protection calculations.

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عنوان مقاله : Photoneutron and capture gamma dose equivalent for different room and maze layouts in radiation therapy

نویسنده رابط : asghar mesbahi

عنوان مجله و شماره مجله : Radiat Prot Dosimet [Internet]. 2010;140(3):242-9.

نویسندگان : Mesbahi A, Ghiasi H, Mahdavi SR

سال انتشار : 2010

چکیده :

عنوان مقاله : Estimation of organs doses and radiation-induced secondary cancer risk from scattered photons for conventional radiation therapy of nasopharynx: A monte carlo study

نویسنده رابط : Asghar mesbahi

عنوان مجله و شماره مجله : Japanese Journal of Radiology [Internet]. 2010;28(5):398-403.

نویسندگان : . Mesbahi A, Seyednejad F, Gasemi-Jangjoo A

سال انتشار : 2010

چکیده :

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عنوان مقاله : A review on photoneutrons characteristics in radiation therapy with high-energy photon beams

نویسنده رابط : asghar mesbahi

عنوان مجله و شماره مجله : Reports of Practical Oncology and Radiotherapy [Internet]. 2010;15(5):138-44.

نویسندگان : . Naseri A, Mesbahi A

سال انتشار : 2010

چکیده : In radiationtherapywithhigh-energyphotonbeams(E > 10MeV)neutronsaregenerated mainlyinlinacsheadthorough(,n) interactionsofphotonswithnucleiofhighatomic numbermaterialsthatconstitutethelinacheadandthebeamcollimationsystem.These neutronsaffecttheshieldingrequirementsinradiationtherapyroomsandalsoincreasethe out-of-field radiationdoseofpatientsundergoingradiationtherapywithhigh-energypho- ton beams.Inthecurrentreview,theauthorsdescribethefactorsinfluencingtheneutron productionfordifferentmedicallinacsbasedontheperformedmeasurementsandMonte Carlo studiesintheliterature.

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عنوان مقاله : MC estimation of out-of-field organ doses from scattered photons, photoneutrons, and capture gamma rays in prostate radiation therapy

نویسنده رابط : asghar mesbahi

عنوان مجله و شماره مجله : Nuclear Technology and Radiation Protection [Internet]. 2010;25(2):78-84

نویسندگان : Mohammadzadeh M, Mesbahi A

سال انتشار : 2010

چکیده : In the cur rent study, the out-of-field or gan and ef fec tive dose for ex ter nal ra di a tion ther apy of pros tate can cer was es ti mated by the MCNPX Monte Carlo code and a math e mat i cal phan tom. Or gan doses from scat tered pho tons, photoneutrons, and cap ture gamma rays were cal cu lated for an 18 MV pho ton beam. Our re sults show that scat tered pho tons are the main con tri bu tors in out-of-field pa tient doses. The re sult ing ef fec tive doses from scat tered pho tons, neu trons and cap ture gamma rays amounted to 723 mSv, 134 mSv, and 45 mSv per a 72 Gy pros tate dose, re spec tively. In con ven tional treat ment, the to tal ef fec tive dose from the three ra di a tions in the cur rent study was 902 mSv per a 72 Gy tu mor dose. Tak ing into ac count that the risk fac - tor for a sec ond ary can cer of an adult male pa tient is 2% per Sv, the prob a bil ity of sec ond ary can cer risks of 1.8% and 6.3% were ob tained for the con ven tional and in ten sity-mod u lated treat ment of the pros tate, re spec tively. Our study sug gests that, tak ing into ac count all con tri - bu tors to or gan doses – in clud ing scat tered pho tons, neu trons, and cap ture gamma rays – out-of- field dose calculations can provide a more realistic estimation for secondary cancer risk anal y sis, as well as a wider range of ther a peu tic tech niques for com par i son.

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عنوان مقاله : A review on gold nanoparticles radiosensitization effect in radiation therapy of cancer

نویسنده رابط : asghar mesbahi

عنوان مجله و شماره مجله : Reports of Practical Oncology and Radiotherapy [Internet]. 2010;15(6):176-80.

نویسندگان : asghar mesbahi

سال انتشار : 2010

چکیده :

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عنوان مقاله : Normoxic polymer gel dosimetry using less toxic monomer of N-isopropyl acrylamide and X-ray computed tomography for radiation therapy applications

نویسنده رابط : asghar mesbahi

عنوان مجله و شماره مجله : Reports of Practical Oncology and Radiotherapy [Internet]. 2010;15(6):172-5.

نویسندگان : Ghavami S-, Mesbahi A, Pesianian I, Shafaee A, Aliparasti M

سال انتشار : 2010

چکیده :

عنوان مقاله : Evaluation of mean glandular dose in a full-field digital mammography unit in tabriz, iran

نویسنده رابط : mehnati

عنوان مجله و شماره مجله : Radiat Prot Dosimet [Internet]. 2010;142(2-4):222

نویسندگان : Riabi HA, Mehnati P, Mesbahi A.

سال انتشار : 2010

چکیده :

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عنوان مقاله : Monte carlo characterization of photoneutrons in the radiation therapy with high energy photons: A comparison between simplified and full monte carlo models.

نویسنده رابط : Asghar mesbahi

عنوان مجله و شماره مجله : Iranian Journal of Radiation Research [Internet]. 2010;8(3):187-93.

نویسندگان : Ghiasi H, Mesbahi A

سال انتشار : 2010

چکیده :

عنوان مقاله : Photoneutron and capture gamma dose calculations for a radiotherapy room made of high density concrete

نویسنده رابط : asghar mesbahi

عنوان مجله و شماره مجله : Nuclear Technology and Radiation Protection [Internet]. 2011;26(2):147-52.

نویسندگان : Mesbahi A, Ghiasi H

سال انتشار : 2011

چکیده :

عنوان مقاله : Photoneutron production and backscattering in high density concretes used for radiation therapy shielding

نویسنده رابط : asghar mesbahi

عنوان مجله و شماره مجله : Ann Nucl Energy [Internet]. 2011;38(12):2752-6.

نویسندگان : Mesbahi A, Azarpeyvand A-, Shirazi A

سال انتشار : 2011

چکیده :

عنوان مقاله : Does concrete composition affect photoneutron production inside radiation therapy bunkers

نویسنده رابط : asghar mesbahi

عنوان مجله و شماره مجله : Japanese Journal of Radiology [Internet]. 2012;30(2):162-6.

نویسندگان : Mesbahi A, Azarpeyvand A-, Khosravi HR

سال انتشار : 2012

چکیده :

عنوان مقاله : Gantry orientation effect on the neutron and capture gamma ray dose equivalent at the maze entrance door in radiation therapy

نویسنده رابط : asghar mesbahi

عنوان مجله و شماره مجله : Nuclear Technology and Radiation Protection [Internet]. 2012;27(1):70-4.

نویسندگان : Ghiasi H, Mesbahi A

سال انتشار : 2012

چکیده :

عنوان مقاله : Optical and NMR dose response of N-isopropylacrylamide normoxic polymer gel for radiation therapy dosimetry

نویسنده رابط : asghar mesbahi

عنوان مجله و شماره مجله : Reports of Practical Oncology and Radiotherapy [Internet]. 2012;17(3):146-50.

نویسندگان : Mesbahi A, Jafarzadeh V, Gharehaghaji N

سال انتشار : 2012

چکیده :

عنوان مقاله : Sensitization of the analytical methods for photoneutron calculations to the wall concrete composition in radiation therapy

نویسنده رابط : asghar mesbahi

عنوان مجله و شماره مجله : Radiat Measur [Internet]. 2012;47(6):461-4.

نویسندگان : Ghiasi H, Mesbahi A

سال انتشار : 2012

چکیده :

عنوان مقاله : A new analytical formula for neutron capture gamma dose calculations in double-bend mazes in radiation therapy

نویسنده رابط : asghar mesbahi

عنوان مجله و شماره مجله : Reports of Practical Oncology and Radiotherapy [Internet]. 2012;17(4):220-5.

نویسندگان : Ghiasi H, Mesbahi A

سال انتشار : 2012

چکیده :

عنوان مقاله : A new barite-colemanite concrete with lower neutron production in radiation therapy bunkers

نویسنده رابط : asghar mesbahi

عنوان مجله و شماره مجله : Ann Nucl Energy [Internet]. 2013;51:107-11.

نویسندگان : Mesbahi A, Alizadeh G, Seyed-Oskoee G, Azarpeyvand

سال انتشار : 2013

چکیده :

دانشکده پزشکی دانشگاه علوم پزشكي و خدمات بهداشتی درمانی تبريز - اصغر مصباحي

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