Dosimetric Comparison and Plan Evaluation of Different Stereotactic Radiosurgery Plans for Treatment Multiple Brain Metastasis Using Single and Dual Isocenter

Abstract

Introduction: stereotactic radiosurgery (SRS)is the most proper treatment for multi brain metastasis for enhanced good coverage and minimizing dose to organs at risk (OARs). This study aims to compare single and dual isocenter SRS plans and discuss which technique we can use with a range distance between two lesions was 4-8cm and maximum of total planning target volumes was 36cc.

Material and Methods: twelve patients with multi brain metastasis underwent two different SRS treatment planning techniques including single isocenter and dual isocenter. We quantitatively assessed plans qualities by dose-volume metrics for two groups according to distance between targets less or more than 6 cm. Conformity index (CI), Confirmation Number (CN), heterogeneity index (HI), gradient distance (GD), Gradient index (GI), and selectivity index. OARs were evaluated and the dose to the normal brain was evaluated using V6, and V12 Gy.

 Results: There is an insignificant difference between single and dual isocenter plans in CI, CN, HI, GD, GI, for two plans with separate distance less than 6 cm.in addition to second group have a significant difference in CN, GI, and GD. Dual isocenter plan have lower volume of normal brain received 6Gy than single isocenter plan with separate distance more than 6 cm.

 Conclusion: Plan quality of single isocenter was equal to dual isocenter for SRS treatment of multi brain lesions. Dual isocenter took time during setup and matching for CBCT and has little difference in dose spillage for more than 6cm distance between targets.