ESTRO 2025 - Abstract Book

S2611

Physics - Detectors, dose measurement and phantoms

ESTRO 2025

Results: In phase 1, silica beads demonstrated agreement with TPS calculations within,-0.2% to +2.8% across four treatment plans. Bead measurements in low-dose regions agreed more closely with the TPS values than radiochromic film, which is known to suffer from reduced signal-to-noise-ratio at lower doses. Phase 2 results showed large discrepancies between TPS and bead measurements in out-of-field regions, with TPS reporting lower doses with mean disagreement of 50% and 70% at distances beyond 4 cm from the field edge compared to beads and film respectively. Beads and film doses were in reasonable agreement, with film and bead measurements showing less than a 17% difference out of field, and 3% in-field, supporting the assertion of underestimation by TPS for out-of field doses (See fig 2).