Beam data commissioning, validation and clinical implementation of SRS gyroscopic system

The very unconventional design and features of the new gyroscopic radiosurgery ZAP-X® system (ZAP Surgical Systems) generates a challenge for beam data acquisition, characterization and validation. Treatment Planning System commissioning was performed with different detectors, filling the absence of methodologies and correction factors published in international guidelines. The congruence of detectors response was compared with corresponding SciMoCa^TM Monte Carlo (MC) synthetic data (Scientific RT GmbH). A machine and patient-specific quality assurance (QA) protocol was also implemented.

All data were acquired using a microsilicon and a microdiamond detectors, three ionization chambers (PTW Freiburg) and a plastic scintillation detector (PSD) (Blue Physics LLC). For patient-specific QA, an anthropomorphic phantom (RT Safe Inc), a 2D array (Sun Nuclear Corporation) and SciMoCa^TM were used for 1D dose verification, 2D and 3D evaluation gamma assessment, respectively.

Agreement between detectors, for all PDDs, was better than 1% beyond the depth of dmax. For profiles, the microsilicon detector showed steeper penumbras due to the smaller detector width. A good congruence with MC data was found for the solid-state detectors. Output factors measurements demonstrated strong agreement between SciMoCa^TM data and PSD data, with a maximum difference of 2.1%. The patient QA results validated the quality of the commissioning data.

Our results showed strong agreement between different measurement methods. MC simulations proved to be an important tool for commissioning validation. The methods and materials discussed in this article may be of use to other facilities where this SRS gyroscope system is installed.