KEY POINTS
- This computational validation study compared the Radiance treatment planning system with the independent penEasy PENELOPE Monte Carlo code across 88 virtual phantoms, including water and heterogeneous tissue-equivalent materials surrounding eight spherical Intrabeam applicators.
- Agreement between Radiance and penEasy was consistently high: average gamma passing rates remained above 95% for every material using both 5%/0.5 mm and 3%/0.5 mm criteria.
- Tissue composition substantially altered absorbed dose relative to water. Depending on applicator size and geometry, deviations ranged from approximately −45% in adipose tissue to +369% in cortical bone.
- Dose absorption followed a consistent material-dependent pattern, with cortical bone receiving the highest dose and adipose tissue the lowest. Effective atomic number influenced absorption more strongly than density alone at these low photon energies.
- The authors estimated that uncertainty in the absorbed dose near the applicator may reach approximately ±50%after accounting for tissue composition and calibration, even before geometric uncertainties are considered.
CLINICAL TAKEAWAY
Radiance produced dose calculations consistent with an independent Monte Carlo reference, supporting its technical accuracy for low-energy X-ray intraoperative radiotherapy. However, prescribing dose to water does not reliably represent dose absorbed by adjacent tissues, making patient-specific tissue assignment and careful evaluation of nearby bone and adipose tissue important for planning and interpretation.