Dosimetric Impact of Fine Dose Grid Calculations In Leksell Gamma Knife SRS
Abstract
Purpose
A steep dose gradient between the target and surrounding normal brain is the hallmark of Leksell Gamma Knife stereotactic radiosurgery (LGK-SRS). However, the impact of fine-dose grid calculations on dose metrics and prescription dose spill into normal brain tissue remains unclear. This study evaluates the dosimetric effects of fine-dose grid and non-fine-dose calculations (0.5 mm and 1.0 mm) on brain metastases of varying target sizes.
Methods
Forty-six patients (n=46), including both framed and frameless procedures, with a total of 192 brain metastases ranging from 0.003 to 13.0 cc were retrospectively analyzed. Treatment plans were generated using Leksell Gamma Plan with and without fine-dose grid calculations. Dose metrics evaluated included the Paddick conformity index (PI), Gradient index (GI), effective fall-off distance (EFOD) from the 100% to 50% isodose lines (IDL), volume of the 100% isodose line (V100%IDL), and intermediate dose spill (R50%), defined as the ratio of the 50% isodose volume (V50%IDL) to the PTV volume.
Results
Statistically significant differences (p0.05 cc. Considering the associated increase in V100%IDL and the planning constraints of single-shot treatments for punctate lesions, fine-dose grid calculations are strongly recommended, with careful consideration of target size and adjacent organs at risk.