Cyberknife Dosimetric Planning Using a Dose-Limiting Shell Method for Brain Metastases
- Author:
Kyoung Jun YOON
1
;
Byungchul CHO
;
Jung Won KWAK
;
Doheui LEE
;
Do Hoon KWON
;
Seung Do AHN
;
Sang Wook LEE
;
Chang Jin KIM
;
Sung Woo ROH
;
Young Hyun CHO
Author Information
- Publication Type:Original Article
- Keywords: Radiosurgery; Brain; Neoplasm metastasis
- MeSH: Brain; Dataset; Methods; Neoplasm Metastasis; Prescriptions; Radiosurgery
- From:Journal of Korean Neurosurgical Society 2018;61(6):753-760
- CountryRepublic of Korea
- Language:English
- Abstract: OBJECTIVE: We investigated the effect of optimization in dose-limiting shell method on the dosimetric quality of CyberKnife (CK) plans in treating brain metastases (BMs).METHODS: We selected 19 BMs previously treated using CK between 2014 and 2015. The original CK plans (CKoriginal) had been produced using 1 to 3 dose-limiting shells : one at the prescription isodose level (PIDL) for dose conformity and the others at lowisodose levels (10–30% of prescription dose) for dose spillage. In each case, a modified CK plan (CKmodified) was generated using 5 dose-limiting shells : one at the PIDL, another at intermediate isodose level (50% of prescription dose) for steeper dose fall-off, and the others at low-isodose levels, with an optimized shell-dilation size based on our experience. A Gamma Knife (GK) plan was also produced using the original contour set. Thus, three data sets of dosimetric parameters were generated and compared.RESULTS: There were no differences in the conformity indices among the CKoriginal, CKmodified, and GK plans (mean 1.22, 1.18, and 1.24, respectively; p=0.079) and tumor coverage (mean 99.5%, 99.5%, and 99.4%, respectively; p=0.177), whereas the CKmodified plans produced significantly smaller normal tissue volumes receiving 50% of prescription dose than those produced by the CKoriginal plans (p < 0.001), with no statistical differences in those volumes compared with GK plans (p=0.345).CONCLUSION: These results indicate that significantly steeper dose fall-off is able to be achieved in the CK system by optimizing the shell function while maintaining high conformity of dose to tumor.
