On the validity of the superposition principle in dose calculations for intracavitary implants with shielded vaginal colpostats

摘要: Intracavitary vaginal applicators typically incorporate internal shielding to reduce dose the bladder and rectum. While distributions about a single colpostat have been extensively measured calculated, these studies neglect dosimetric perturbations arising from contralateral or intrauterine tandem. Dosimetric effects of inhomogeneities in brachytherapy is essential for both dose-based implant optimization as well comparison with alternate modalities, such intensity modulated radiation therapy. We used Monte Carlo calculations model Fletcher–Suit–Delclos (FSD) low dose-rate system microSelectron high remote afterloading system. evaluated errors, relative simulation based upon complete applicator system, superposition precalculated shielded unshielded source distributions. Errors were largely dominated by primary photon attenuation, largest behind shields For FSD applicators, showed differences ranging mean 2.6% at doses (>Manchester Point A dose) 4.3% (