Comparison of Brain Dose Metrics Among Multiple Stereotactic Radiosurgery Delivery Platforms for Brain Metastases
Abstract
Purpose
This study compares brain dose metrics evaluated using multiple dedicated stereotactic radiosurgery (SRS) delivery platforms for the treatment of brain metastases.
Methods
Four sets of gross tumor volumes (GTVs), grouped by lesion size (Group1[≤5mm], Group2[>5-10mm], Group3[>10-15mm], and Group4[>15mm]), were contoured. SRS plans (20 Gy in 1 fraction) were generated using Gamma Knife (GK) Leksell GammaPlan Version 11.3.2, Cyberknife (CK) Precision Version 3.3.1.2, and ZAP-X Version DB-1011. Plans for each group started with a nominal number of lesions which were progressively increased until the mean brain threshold dose of 8Gy was reached. The brain volume receiving 8, 10, and 12 Gy (V8Gy, V10Gy and V12Gy), mean brain dose, total GTV volume, and total number of lesions were compared.
Results
Across all simulated plans, the mean brain dose was linearly proportional (correlation coefficient: 0.99) to the number of lesions and total GTV volume. Maximum number of lesions and corresponding GTV volumes needed to reach the mean brain dose of 8 Gy were 177[3.62cc], 57[20.37cc], 29[30.25cc], and 10[57.96cc] for Groups1-4 for GK, 135[2.32cc], 35[12.09cc], 18[18.24cc], and 8[41.52cc] for CK, and 120[2.12cc], 41[14.24cc], 22[22.35cc], and 9[49.03cc] for Zap-X. V8Gy, V10Gy, and V12Gy had a quadratic correlation to the number of lesions and the total GTV volume, with GK giving the least contribution to the normal brain, followed by Zap-X, and CK.
Conclusion
Mean brain dose was found to increase linearly with number of lesions and total GTV volume while select metrics such as V8Gy, V10Gy, and V12Gy showed a quadratic correlation to the number of lesions and the total GTV volume. GK was found to contribute the least to the integral brain dose, followed by Zap-X and then CK.