Evaluation of Superficial Dosimetry in Postmastectomy Radiotherapy using High-energy Electromagnetic Radiation Treatment

Abstract

The present study evaluated surface and superficial doses delivered by high-energy electromagnetic radiation treatment in patients who received postmastectomy radiotherapy. Computed tomography was performed using an RW3 slab phantom, and hypothetical target volumes were delineated. 6MV electromagnetic radiation beams were generated with five treatment plans: 2-field 3-dimentional conformal radiation therapy, 4-field intensitymodulated radiation therapy, 7-field intensity-modulated radiation therapy, TomoHelical 3-dimentional conformal radiation therapy, and TomoHelical intensity-modulated radiation therapy. Film dosimetry was performed with Gafchromic EBT3 film for dose measurement of high-energy electromagnetic radiation. The dose profile at the surface and superficial regions (1-6 mm depth) of the phantom obtained for each treatment technique. Compared to other techniques, Tomo 3-dimentional conformal radiation therapy had the highest surface dose (47-71 %). The superficial doses of TomoHelical 3-dimentional conformal radiation therapy and TomoHelical intensity-modulated radiation therapy were > 75 %, 80 %, and 90 % of the prescribed dose at 1, 2, and 5 mm depths, respectively. For postmastectomy radiotherapy, TomoHelical 3-dimentional conformal radiation therapy and TomoHelical intensity-modulated radiation therapy had higher surface and superficial doses than linear accelerator-based treatment techniques, with a sufficient dose of ≥ 75 % being delivered to the skin region at depths of 1 mm.