ESTRO 2024 - Abstract Book

S3392

Physics - Detectors, dose measurement and phantoms

ESTRO 2024

Fig.1: Data Pipeline: The treatment planning system (a) generates the treatment plan, executed by a C-arm linear accelerator (b). During treatment, multi-leaf collimator movements are recorded in a trajectory log file and, along with images acquired by the MV-imager (c), are transferred to the RadCalc software (LAP, Germany) for backward projection 3D dose calculation.

Fig.2: Phantom Measurement: Panel (a) displays the intended treatment plan. Panel (b) illustrates the Alderson phantom's placement on the treatment couch, highlighting the direction of structured misalignment.

Results:

Each scheduled IVD fraction underwent automatic analysis, resulting in six false positive alerts. One instance occurred due to a missing EPID images from the LINAC, with no discernible cause, and five instances were due to a single-day imager defect promptly rectified. The phantom study results are shown in Table1. In the clinical phase, the approach proved instrumental in detecting anatomical shifts, mirroring insights from CBCT evaluations. The period witnessed no incidents of misirradiation or significant dosimetric aberrations (>5% mean dose in PTV). A case in point involved a prostate patient, where EPID-IVD unveiled two instances of underdosage, attributable to pronounced intestinal filling deviations from the planning CT, corroborated by CBCT.

Gamma3%/3mm [%]

Dose-File

delta [%]

D50%[Gy] delta [%]

D98%[Gy]

delta [%]