¹ Nuclear Science Department, Heron Neutron Medical Corporation, Zhubei, Taiwan² Strategy Office, Heron Neutron Medical Corporation, Zhubei, Taiwan³ Department of Heavy Particles and Radiation Oncology, Taipei Veterans General Hospital, Taipei, Taiwa

   

   

Abstract

This study is a retrospective analysis of the effectiveness of bolus placement for superficial oral cancer treated with boron neutron capture therapy (BNCT) using the THORplan treatment planning system. Three treatment plans were performed: one without bolus, one with the bolus placed directly on the skin surface, and one with the bolus positioned at the collimator exit as an alternative to overcome potential challenges in patient setup using bolus. The results indicate that applying a 1 cm-thick bolus directly on the skin surface significantly increases the mean tumor dose by 60 %, owing to the forward shift of the thermal neutron flux peak into the tumor region. Conversely, this benefit was not observed when the bolus was placed at the collimator exit. The air gap between the bolus and the skin surface reduced the epithermal neutron flux entering the skin by 40 %, diminishing its therapeutic effectiveness.