Mahmoudi, Atefeh, Geraily, Ghazale, Shirazi, Alireza, Bakhshi, Masoume. (1397). Study the effect of source to diaphragm distance (SDD) on beam penumbra width of Gamma Knife machine model 4C using Monte Carlo simulation. , 15(Special Issue-12th. Iranian Congress of Medical Physics), 363-363. doi: 10.22038/ijmp.2018.13027
Atefeh Mahmoudi; Ghazale Geraily; Alireza Shirazi; Masoume Bakhshi. "Study the effect of source to diaphragm distance (SDD) on beam penumbra width of Gamma Knife machine model 4C using Monte Carlo simulation". , 15, Special Issue-12th. Iranian Congress of Medical Physics, 1397, 363-363. doi: 10.22038/ijmp.2018.13027
Mahmoudi, Atefeh, Geraily, Ghazale, Shirazi, Alireza, Bakhshi, Masoume. (1397). 'Study the effect of source to diaphragm distance (SDD) on beam penumbra width of Gamma Knife machine model 4C using Monte Carlo simulation', , 15(Special Issue-12th. Iranian Congress of Medical Physics), pp. 363-363. doi: 10.22038/ijmp.2018.13027
Mahmoudi, Atefeh, Geraily, Ghazale, Shirazi, Alireza, Bakhshi, Masoume. Study the effect of source to diaphragm distance (SDD) on beam penumbra width of Gamma Knife machine model 4C using Monte Carlo simulation. , 1397; 15(Special Issue-12th. Iranian Congress of Medical Physics): 363-363. doi: 10.22038/ijmp.2018.13027

Study the effect of source to diaphragm distance (SDD) on beam penumbra width of Gamma Knife machine model 4C using Monte Carlo simulation

Iranian Journal of Medical Physics
مقاله 356، دوره 15، Special Issue-12th. Iranian Congress of Medical Physics، بهمن و اسفند 2018، صفحه 363-363
نوع مقاله: Conference Proceedings
شناسه دیجیتال (DOI): 10.22038/ijmp.2018.13027
نویسندگان
Atefeh Mahmoudi1؛ Ghazale Geraily2؛ Alireza Shirazi3؛ Masoume Bakhshi1
1Master Student, Medical Physics and Biomedical Engineering Department, Tehran University of Medical Sciences, Tehran, Iran
2Assistant Professor, Medical Physics and Biomedical Engineering, Department, Tehran University of Medical Sciences, Tehran, Iran
3Full Professor, Medical Physics and Biomedical Engineering, Department, Tehran University of Medical Sciences, Tehran, Iran
چکیده
Introduction: Stereotactic radiosurgery (SRS) is one of the conformal radiotherapy methods and Gamma Knife is a non-invasive SRS technique to treat intracranial lesions with 201 Co- 60 sources without need to surgery and bleeding. Beam penumbra phenomenon leads to irradiation outside the field and normal tissues. Therefore, considering it is momentous to attain the acceptable treatment plan.
 
Materials and Methods: In this study, Gamma Knife unit was modeled using EGSnrc/BEAMnrc Monte Carlo code. SDD (Source to Diaphragm Distance) parameter that is one of the affecting factors on physical penumbra width was studied. For this purpose, SDD was increased for 4, 8, 14 and 18 mm collimator sizes in five steps and each step as much as one centimeter. Single beam profiles were calculated using EGSnrc/DOSXYZnrc code at isocentre depth in a cubic Plexiglas phantom. MATLAB and EXCEL software were used to plot profiles and measure physical penumbra width
.
Results: Based on the results, physical penumbra width (90%-50%) does not show a regular trend with increasing SDD. This may be attributed to scatter radiation which is due to the low distance between the Gamma Knife collimator end and phantom surface. Best results were observed for 4 and 8 mm collimators in 1 cm increase in which penumbra width decreased from 0.785 and 0.790 mm to 0.749 and 0.736 mm for 4 and 8 mm collimator sizes, respectively.
Conclusion: It is recommended to increase SDD of Gamma Knife 4C around 1 centimeter to reduce penumbra width for small tumor sizes located near the critical nerves.
کلیدواژه‌ها
Gamma Knife Monte Carlo code SDD؛ Physical penumbra
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