Investigation of physical penumbra definition in IMRT applications
محل انتشار: مجله فیزیک پزشکی ایران، دوره: 15، شماره: 0
سال انتشار: 1397
نوع سند: مقاله ژورنالی
زبان: انگلیسی
مشاهده: 35
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شناسه ملی سند علمی:
JR_IJMP-15-0_167
تاریخ نمایه سازی: 29 آذر 1402
چکیده مقاله:
Introduction: Because of small size of the beamlets in IMRT, physical penumbra is one of the important dosimetric parameters and small changes in the penumbra will have a great impact on the results. The physical penumbra width is defined as the lateral distance between two specified isodose curves at a specified depth of phantom. In this study, after demonstrating the inconsistency of conventional physical penumbra definition for non-uniform MLC fields, two new dosimetric parameters proposed, those are intended to be suitable for MLC fields Materials and Methods: Physical penumbra evaluation was obtained using IAEA phase space data for a Varian IX and EGSnrc Monte Carlo code package. The homogenous water phantom is located at SSD=۱۰۰ cm. Results: With conventional definition, physical penumbra widths for all MLC setups on right and left sides of isodose curves (parallel to X and Y axes) are not equal. With the proposed dosimetric parameters, the effect of MLC setup is taken into consideration. Conclusion: The intended purpose from physical penumbra in its conventional definition is not satisfied for non-uniform MLC setups. For such cases, the newly defined surface penumbra and uniformity index are demonstrated to be more suitable and indicative of the field non-uniformity. It is also shown that for an idle treatment planning system, the uniformity index approaches unity.
کلیدواژه ها:
Physical Penumbra Dosimetric Parameters DOSXYZnrc EGSnrc ، CTV
نویسندگان
Hajar Alipour
Department of Nuclear Engineering, Shiraz University, Faculty of Mechanical Engineering, Email: halipour@shirazu.ac.ir Tel: +۹۸ ۹۳۸۵۷۴۱۹۴۹
Kamal Hadad
۱Department of Nuclear Engineering, Shiraz University, Faculty of Mechanical Engineering,
Reza Faghihi
Department of Nuclear Engineering, Shiraz University, Faculty of Mechanical Engineering,