MRI-guided cardiac-induced target motion tracking for atrial fibrillation cardiac radioablation

Suzanne Lydiard; Beau Pontré; Nicholas Hindley; Boris S Lowe; Giuseppe Sasso; Paul Keall

doi:10.1016/j.radonc.2021.09.025

MRI-guided cardiac-induced target motion tracking for atrial fibrillation cardiac radioablation

Radiother Oncol. 2021 Nov:164:138-145. doi: 10.1016/j.radonc.2021.09.025. Epub 2021 Sep 28.

Authors

Suzanne Lydiard¹, Beau Pontré², Nicholas Hindley³, Boris S Lowe⁴, Giuseppe Sasso⁵, Paul Keall³

Affiliations

¹ ACRF Image X Institute, University of Sydney, Eveleigh, Australia. Electronic address: slyd6788@uni.sydney.edu.au.
² Department of Anatomy and Medical Imaging, University of Auckland, New Zealand.
³ ACRF Image X Institute, University of Sydney, Eveleigh, Australia.
⁴ Green Lane Cardiovascular Service, Auckland City Hospital, New Zealand.
⁵ Department of Anatomy and Medical Imaging, University of Auckland, New Zealand; Radiation Oncology Department, Auckland City Hospital, New Zealand; Department of Oncology, University of Auckland, New Zealand.

PMID: 34597739
DOI: 10.1016/j.radonc.2021.09.025

Abstract

Background and purpose: Atrial fibrillation (AF) cardiac radioablation (CR) challenges radiotherapy tracking: multiple small targets close to organs-at-risk undergo rapid differential cardiac contraction and respiratory motion. MR-guidance offers a real-time target tracking solution. This work develops and investigates MRI-guided tracking of AF CR targets with cardiac-induced motion.

Materials and methods: A direct tracking method (Tracking_direct) and two indirect tracking methods leveraging population-based surrogacy relationships with the left atria (Tracking_{indirect_LA}) or other target (Tracking_{indirect_target}) were developed. Tracking performance was evaluated using transverse ECG-gated breathhold MRI images from 15 healthy and 10 AF participants. Geometric and volumetric tracking errors were calculated, defined as the difference between the ground-truth and tracked target centroids and volumes respectively. Transverse, breath-hold, noncardiac-gated cine images were acquired at 4 Hz in 5 healthy and 5 AF participants to qualitatively characterize tracking performance on images more comparable to MRILinac acquisitions.

Results: The average 3D geometric tracking errors for Tracking_direct, Tracking_{indirect_LA} and Tracking_{indirect_target} respectively were 1.7 ± 1.2 mm, 1.6 ± 1.1 mm and 1.9 ± 1.3 mm in healthy participants and 1.7 ± 1.3 mm, 1.5 ± 1.0 mm and 1.7 ± 1.2 mm in AF participants. For Tracking_direct, 88% of analyzed images had 3D geometric tracking errors <3 mm and the average volume tracking error was 1.7 ± 1.3 cc. For Tracking_direct on non-cardiac-gated cine images, tracked targets overlapped organsat-risk or completely missed the target area on 2.2% and 0.08% of the images respectively.

Conclusion: The feasibility of non-invasive MRI-guided tracking of cardiac-induced AF CR target motion was demonstrated for the first time, showing potential for improving AF CR treatment efficacy.

Keywords: Atrial fibrillation; Cardiac arrhythmias; MRI-Linac; Non-invasive; Radioablation; Stereotactic radiotherapy.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Atrial Fibrillation* / diagnostic imaging
Heart / diagnostic imaging
Humans
Magnetic Resonance Imaging
Motion