Session Item

To evaluate the congruence of detectors response for base data measurements for the ZAP-X system (ZAP Surgical Systems, San Carlos, USA) benchmarked against corresponding Monte Carlo (MC) synthetic data (Scientific RT GmbH, Munich, D).

All data were acquired in a water tank MP3-XS (PTW, Freiburg, Germany), using a microSilicon PTW60023 (mS60023), a micro diamond PTW60019 (mD60019), ionisation chambers PTW31010 & PTW31021 (IC31010 & IC31021), a plastic scintillation detector (PSD) (Blue Physics LLC, Tampa, USA) and EBT-XD Gafchromic film (Ashland, Covington, USA)

At SSD 450mm and 30mm depth, output factors (OF) and cross-profiles were acquired for all collimators s (25, 20, 15, 12.5, 10, 7.5, 5, 4mm) with the mS60023, mD60019, IC31021, EBT-XD and PSD, while depth-dose-curves (DDC) were measured with the mS60023, mD60019, PSD and, only for the collimator of 25mm, with the IC31021.

Agreement between MC synthetic data and all cross-profiles was well within 2%/0.2mm after tuning the nominal collimator diameters in the range of 0.1-0.2 mm.

Similarly, a MC match with the DDC IC31021 data for the collimator 25mm could be achieved if the nominal 3MV spectrum is shifted to a max energy of 3,7MV.

OF measurements indicate that the PSD is closest to the MC calculated data and that all the detectors would require correction factors to account for their field- effects (uo to 5%,). If the nominal energy is increased to 3,7MV we observe that no correction factor would have to be applied for the OFs, as for the solid state detectors the oversensitivity tends to be compensated by partial volume effects.

The very compact design of the ZAP-X creates a challenge for measurements set-ups and acquisition of a consistent datasets. Our findings show good congruence of measurements methods and robust benchmarking against MC synthetic data.

The combination of IC31021 DDC and of OFs measurements clearly indicate that the beam spectrum is shifted towards higher energies (with MC showing the max at 3,7MV). Furthermore, correction factors are not needed for OFs acquired with the PSD and that satisfactory (below 1%) results are reached with diamond detector.