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SU‐F‐P‐60: Optimization of Cyberknife Treatment Planning Using a Dose‐Limiting Auto‐Shells Method for Brain Metastases
Author(s) -
Yoon K,
Cho B,
Kwak J,
Lee D,
Kwon D,
Ahn S,
Lee S,
Kim C,
Roh S,
Cho Y
Publication year - 2016
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4955768
Subject(s) - cyberknife , nuclear medicine , radiosurgery , limiting , medicine , dosimetry , radiation treatment planning , radiation therapy , mechanical engineering , engineering
Purpose: In pursuit of high precision in target localization and steeper dose fall‐off in stereotactic radiosurgery, we investigated the impact of optimizing dose‐limiting auto‐shell function on the quality of Cyberknife (CK) plans in treating brain metastases (BMs). Methods: Nineteen BMs previously treated using CK were selected for this study. The original CK plans (CK_original) had been produced using one to three dose‐limiting auto‐shells at prescription dose (PD) level and low dose levels of 10 to 30% of PD. In each case, a modified CK plan (CK_modified) was generated using five dose‐limiting shells at PD level, intermediate dose level of 50% of PD, and low dose levels with an optimal shell‐dilation size based on our experience. In addition, a Gamma Knife plan (GK) was also produced using the original contour set. Thus, a triplet data set of dosimetric parameters was generated and analyzed. Results: While no differences in conformity index (mean±SD 1.22 ± 0.1, 1.18 ± 0.1, and 1.24 ± 0.1 in CK_original, CK_modified, and GK, respectively; over all P > 0.05) and tumor coverage (mean±SD 99.5 ± 0.4%, 99.5 ± 0.3%, and 99.4 ± 0.2% in CK_original, CK_modified, and GK, respectively; over all P > 0.05) were observed among the plans, the normal tissue volume receiving 50% of PD was significantly decreased in CK_modified and GK compared with CKoriginal by 1.28 and 1.27‐fold, respectively (P < 0.001, each). No significant differences in dose fall‐off were observed between CK_modified and GK (P = 0.345). Conclusion: By optimizing auto‐shell function, a significantly steeper dose fall‐off can be achieved in CK system, while maintaining high precision in target localization.