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Dosimetry Comparison of Gamma Knife and Linac Based External Beam SRS

L Lu

C Klinker , C Jett , C Barney , E Allan , N Gupta , L Lu*, Ohio State Univ, Columbus, OH


SU-I-GPD-T-587 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: To compare dosimetric results of treatment planning with Gamma Knife and Linac Based External Beam stereotactic radiosurgery (SRS).

Methods: We retrospectively retrieved the CT/MRI images and contours of the targets and the organs at risk of the treatment plans of previous patients treated with Linac-based SRS (or vice versa, treated with Gamma Knife) from Eclipse (Gamma Knife LGP system) and exported them to the Gamma Knife (Linac-based SRS) treatment planning system, then used the same images and contours to simulate the patient’s treatment with Gamma Knife (Linac-based SRS). For Gamma Knife treatment plans, before we compared them with Linac-based plans, we first studied the plans of TMR10 (without inhomogeneous correction) and Convolution (with inhomogeneous correction), and then we used the Gamma Knife convolution plans to compare with the Linac-based SRS plans. By comparing the dosimetry quantities in the treatment plans, we could evaluate the advantages and disadvantages on dosimetry of each treatment modality based on the tumor locations in the brain and disease types.

Results: We studied three different types of tumors: (1) metastatic tumors, (2) pituitary tumors, and (3) acoustic schwannomas. For Gamma Knife plans, the dosimetric difference on targets between the inhomogeneity correction and without inhomogeneity correction is found to have considerable significance. The dosimetric difference on targets between Gamma Knife plans and Linac-based plans is relatively significant when dose is prescribed to GTV for Gamma Knife while for Linac-based SRS prescribed to PTV which indicates the margin set for different modality treatments would impact the dosimetric results.

Conclusion: The results indicate that either Gamma Knife or Linac-based SRS has its own advantages and disadvantages on dosimetry which depend on disease type and location. To choose the proper treatment modality for patients we may need to consider other factors besides dosimetry only, which is worth further investigation.

Funding Support, Disclosures, and Conflict of Interest: Mr. Cody Klinker is supported with Arts and Sciences Undergraduate Research Scholarship from the Ohio State University.

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