Characterisation of heart and diaphragm motion: Implications for treatment planning and delivery of radiotherapy for ventricular tachycardia

Abstract

A novel use of radiotherapy to treat ventricular tachycardia (VT) delivers large doses of high energy x-rays to the VT substrate: STereotactic Arrhythmia Radioablation (STAR). This treatment has only recently been developed for the clinic and characterisation of cardiac and respiratory motion in radiotherapy is of interest but is not yet generally achieved. This thesis examines the feasibility and utility of tracking both the distal electrode (pacing lead tip) of implantable cardioverter defibrillators (ICD) and the diaphragm in STAR patients. Lead tip and diaphragm positions are identified in kV planar images of the patient, acquired on a linear accelerator before radiotherapy treatment planning and immediately prior to treatment, and tracked across the image sequence. A coding toolkit was constructed for this purpose and was shown to track both objects to within 0.5 mm. The toolkit was able to identify the pacing lead tip and diaphragm in 84.9% and 94.4% of tested frames respectively. Data from 3 patients treated at South Tees NHS Hospitals Foundation Trust showed full amplitude lead tip displacements of 7.7, 9.7 and 11.8 mm in left-right, ant-post and sup-inf directions respectively. Average diaphragm displacement amplitudes were reported between 8.5 and 22.3 mm. The utility of the data was shown to be twofold: (1) providing quantitative information useful for informing target volume dimensions, and (2) providing quality assurance at the point of delivery; ensuring that cardiac and respiratory cycles are the same when delivering radiotherapy as when it was planned. This work provides a method for assessing cardiac and respiratory motion in STAR patients, and discusses the implications of those measured data.

Date of Award	31 Dec 2021
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Philip Whitehurst (Supervisor)