Comparison of the Dose of the Normal Tissues among Various Conventional Techniques for Whole Brain Radiotherapy

Kang, Min Kyu

Abstract

PURPOSE
To compare radiation dose of the brain and lens among various conventional whole brain radiotherapy (WBRT) techniques.
MATERIALS AND METHODS
Treatment plans for WBRT were generated with planning computed tomography scans of 11 patients. A traditional plan with an isocenter located at the field center and a parallel anterior margin at the lateral bony canthus was generated (P1). Blocks were automatically generated with a 1 cm margin on the brain (5 mm for the lens). Subsequently, the isocenter was moved to the lateral bony canthus (P2), and the blocks were replaced into the multileaf collimator (MLC) with a 5 mm leaf width in the craniocaudal direction (P3). For each patient plan, 30 Gy was prescribed at the isocenter of P1. Dose volume histogram (DVH) parameters of the brain and lens were compared by way of a paired t-test.
RESULTS
Mean values of D(max) and V(105) of the brain in P1 were 111.9% and 23.6%, respectively. In P2 and P3, D(max) and V(105) of the brain were significantly reduced to 107.2% and 4.5~4.6%, respectively (p<0.001). The mean value of Dmean of the lens was 3.1 Gy in P1 and 2.4~2.9 Gy in P2 and P3 (p<0.001).
CONCLUSION
WBRT treatment plans with an isocenter located at the lateral bony canthus have dosimetric advantages for both the brain and lens without any complex method changes.