Room: Track 2
Purpose: Stereotactic Arrhythmic Radioablation (STAR) is an emerging indication for patients suffering from malignant cardiac arrhythmia. The target volume and surrounding critical structures experience a complex interplay between respiratory motion and cardiac deformation. Yet, current treatment planning accounts for either respiratory motion alone (4D-CT) or requires multiple scans at the cost of time and excess imaging dose. Here, we have developed an in-house software and demonstrated CT image reduction feasibility by accounting for dual respiratory-cardiac motion in real-time.
Method: Dual-Gated CT imaging was simulated on a deformable digital phantom (XCAT) for three sets of patient-measured ECG and respiratory traces. Our in-house software monitored motion in real-time, triggering a simulated CT acquisition with a 0.36s gantry rotation speed and a 2cm/1s couch translation. Ten respiratory phases during cardiac diastole (60-80% through cardiac cycle) were acquired for each scan. Image artifacts were quantified for cardiac substructures using the normalized cross correlation (NCC) between axial slices (NCCdiff). The total scan times and the beam-on times were recorded. A conventional respiratory 4D-CT protocol was implemented using the same software where the NCC and time metrics were compared to the Dual-Gated images.
Results: NCCdiff was reduced by 52%, 39%, 8%, 16%, 25% and 17% on average using Dual-Gated CT compared to conventional 4D-CT for the left ventricle wall, right ventricle wall, left atrium wall, right atrium wall, coronary artery and coronary vein respectively. The total scan time was increased for each simulation using Dual-Gated CT (average 3.5min) compared to 4D-CT (average 1min). The total beam-on time was reduced from an average of 40s in 4D-CT to 29s with Dual-Gated CT.
Conclusion: Our in-house software for Dual-Gated CT successfully reduced cardiac image artifacts while reducing beam-on time as compared to conventional respiratory 4D-CT. This study provides a crucial first step towards dual-motion management for STAR treatments.
Funding Support, Disclosures, and Conflict of Interest: This work was supported by grant #123068 awarded through the Priority driven Collaborative Cancer Research Scheme and funded by Cancer Australia. RO would like to acknowledge the support of a Cancer Institute of NSW Career Development Fellowship.