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- Title
Estimation of the Maximum Number of Lesions Able to be Treated with Single Session Stereotactic Radiosurgery with Contemporary Planning Systems.
- Authors
Tolakanahalli, Ranjini; Wieczorek, D Jay; Lee, YongSook; Hall, Matthew; Tom, Martin; Mehta, Minesh; McDermott, Michael; Gutierrez, Alonso; Kotecha, Rupesh
- Abstract
Purpose: Emerging evidence supports the role of stereotactic radiosurgery alone in patients with up to 15 brain metastases. As modern technology and evidence develops to allow treatment to numerous brain metastases, a re-evaluation of the capability of modern radiosurgery treatment planning systems is warranted. The objective of this study is to explore the number and volume of lesions that can be treated with the latest Gamma Knife(GK) and CyberKnife(CK) treatment modalities in a single treatment setting. Methods: 200 target contours with volumes varying from 0.001 cc to 1.1 cc were simulated on a model MRI scan of a normal brain. Target volumes were derived from clinically treated contours superimposed on the model brain scan. All lesions were planned to 20Gy/1 fraction with the exception of brainstem lesions planned to 15 Gy/1 fraction per institutional clinical treatment guidelines. For GK treatment plans, due to limitations in the planning system, individual plans with 52 lesions each were generated ensuring greater than 99% target coverage and maximizing conformity. Subsequently, number of lesions were progressively increased until the threshold mean dose to the brain (including target volumes) of 8Gy was reached. Similarly, CK plans were generated with 11-30 lesions each using fixed cones and prescribed such that at least 99.6% of the target volume received prescription dose. Composite dose distribution was generated to calculate the dose metrics from all plans. Results: The maximum number of target lesions and total tumor volume (TTV) corresponding to a mean brain dose to a pre-specified threshold of 8 Gy for GK treatment plans was 156 lesions and 8.4 cc, and 66 lesions and 7.3 cc for CK plans, respectively. Corresponding V12cc to brain was 142.8 cc for GK and 225.5 cc for CK modalities. The increase in V12cc is mainly attributed from the inability to optimize all lesions simultaneously. Conclusion: Approximately 156 lesions of mixed sizes can be treated on GK in a single session totaling a target volume of 8.4 cc before exceeding a brain mean dose of 8 Gy. CK plans were found to allow a fewer number of lesions (66) and target volume (7.3 cc) for the same 8Gy brain mean dose while resulting in a higher V12Gy. V12Gy for both technologies showed a correlation to the TTV. Proximity of the lesions may result in overlap of low dose volume resulting in increased V12Gy.
- Subjects
STEREOTACTIC radiosurgery; BRAIN metastasis; BRAIN imaging; RADIOSURGERY
- Publication
Journal of Radiosurgery & SBRT, 2022, Vol 8, p94
- ISSN
2156-4639
- Publication type
Article