Investigation of the RayPilot Tracking System for use in dose escalated Prostate SBRT

Abstract

Aim: To investigate the use of the RayPilot tracking system to help treat prostate SBRT with a dose escalated boost of 45Gy in 5#. Method and materials: Seven patients in the PRINToUT trial received prostate SBRT (36.25Gy in 5#) treated using 3 VMAT arcs delivered on Truebeam linacs and planned using the Eclipse TPS (v13.6). Pre-treatment imaging was with kV orthogonal and CBCT and tumour tracking using the RayPilot system. RayPilot uses an electromagnetic transmitter inserted into the prostate. The position of the transmitter was analysed retrospectively using the RayPilot system readout and the transmitter position on CBCT images. A planning study, adding a dose escalated boost (45Gy in 5#) to the prostate SBRT plans was carried out, with additional plans simulating degrees of patient displacement from the clinical imaging data. All new plans were assessed against the PRINToUT protocol. Results: From the CBCT images, the mean displacement of the RayPilot transmitter comparing the CT and the CBCT scans was -0.04cm(x), 0.07cm(y) & 0.16cm(z). The RayPilot system recorded all treatments except #3, 4 & 5 for patient 4 due to technical issues with the mean displacement of the transmitter within 0.03cm. In the planning study the PTV, CTV and PTV(boost) dose coverage was acceptable with dose escalation but only two patients in the study met all of the rectum dose constraints. Simulating the CBCT positional data, PTV coverage was not met on four patients and for the RayPilot data the plan dosimetry was not significantly affected by the displacements. Conclusion: The RayPilot tracking system could be used in the treatment of prostate SBRT with a dose escalated boost. Further studies would be required before this could be used as a primary imaging method for patient positioning.

Date of Award	1 Aug 2022
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Michael Kirby (Supervisor)