Investigation of physical penumbra definition in IMRT applications | ||
| Iranian Journal of Medical Physics | ||
| مقاله 167، دوره 15، Special Issue-12th. Iranian Congress of Medical Physics، بهمن و اسفند 2018، صفحه 167-167 | ||
| نوع مقاله: Conference Proceedings | ||
| شناسه دیجیتال (DOI): 10.22038/ijmp.2018.12674 | ||
| نویسندگان | ||
| Hajar Alipour* 1؛ Kamal Hadad2؛ Reza Faghihi3 | ||
| 1Department of Nuclear Engineering, Shiraz University, Faculty of Mechanical Engineering, Email: halipour@shirazu.ac.ir Tel: +98 9385741949 | ||
| 21Department of Nuclear Engineering, Shiraz University, Faculty of Mechanical Engineering, | ||
| 3Department of Nuclear Engineering, Shiraz University, Faculty of Mechanical Engineering, | ||
| چکیده | ||
| 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=100 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. | ||
| کلیدواژهها | ||
| Physical Penumbra Dosimetric Parameters DOSXYZnrc EGSnrc؛ CTV | ||
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