Measurement and comparison of prostate treatment dose to the femoral heads with 6-MV versus 10-MV photon energies

Abstract

The purpose of this paper is to compare the femoral head dose distribution of 6-MV x-rays vs. 10-MV x-rays when treating prostate patients using a 4-field initial box technique with a Michigan technique boost. First, tissue maximum ratio (TMR) calculations were utilized to project the expected dose contributions to the femoral heads from each energy based upon the average male pelvis. Then, plans for both the 6- and 10-MV energies were developed for 5 prostate patients using the ADAC Pinnacle 3 (Milpitas, CA) treatment planning computer. Average doses and dose gradients were determined by examination of isodose curves. The dose contributions to the femoral heads were analyzed and compared with the tolerance dose (TD) 5/5 for this region. No significant dose differences existed between the 6- and 10-MV photon energies. This conclusion was supported by examination of point doses at depths of 3, 6, 12, and 15 cm for each energy.