End-to-end dosimetric verification of Cardiac Stereotactic Ablative Body Radiotherapy using a novel dynamic anthropomorphic cardiac model

Abstract

Introduction Clinical evidence demonstrating the potential of SABR to treat cardiac arrhythmic indications is growing. Despite additional risks arising from the challenging nature of cardiac SABR and a strong history of quality assurance in radiotherapy, there remains a scarcity of evidence demonstrating end-to-end dose delivery accuracy for this novel indication. Methods An anthropomorphic cardiac insert was produced to measure dose delivery accuracy in cardiac SABR using radiochromic film. Radiotherapy treatment plans reflective of clinical cardiac SABR practice were examined for the CyberKnife VSI and Varian Truebeam platforms, including respiratory tracking and gating, respectively. Results For all techniques and platforms, maximal spatial corrections of 1 mm were required in up to three orthogonal directions to achieve median global gamma 5% / 1 mm pass-rates above 99 %. Following spatial correction, median doses were within 2.5 % (Varian Truebeam) and 1.5 % (Accuray CyberKnife) of calculated dose. Gamma pass-rates were sensitive to high out-of-plane dose gradients, which must be considered when assessing 3D plan delivery accuracy with 2D methodology. Conclusions Cardiac SABR dosimetric accuracy is deliverable to levels commensurate with the requirements of this indication even when employing sophisticated respiratory motion management techniques. These techniques should be explored further to reduce the treated volume. This methodology facilitates direct, independent system accuracy quality assurance for cardiac SABR which, if utilised by centralised quality assurance services, could benefit standardisation and the establishment and maintenance of minimum quality standards for future cardiac SABR clinical trials and beyond.

Date of Award	1 Aug 2023
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Michael Taylor (Supervisor)