Integration of an echocardiographic motion-management system into photon-based stereotactic arrhythmia radioablation...

Cardiorespiratory ultrasound motion monitoring may enhance the precision of dose delivery for stereotactic arrhythmia radioablation (STAR) of ventricular tachycardia. This treatment planning study aimed to evaluate the feasibility of photon-based STAR planning in the presence of an ultrasound probe.

For sixteen targets in fourteen patients, three treatment plans were retrospectively created and compared: a reference plan without an ultrasound probe and two plans in which the ultrasound probe was spared from the primary treatment beam (apical or parasternal probe positions). Descriptive and statistical analyses were performed for target/organ dose-volume and treatment beam metrics, conformity-indices and maximum probe exposure.

The ultrasound probe could be spared from the primary beam in all cases with D_{0.035 cm³} < 1 Gy (median 0.2 Gy with apical and 0.4 Gy with parasternal placement) with slightly elevated organ dose-volume metrics and no significant differences in target dose-volume metrics. The conformity-index (50 % isodose line) differed significantly for apical and parasternal probe position (median reference plan 4.0 vs. 5.0 and 4.5, respectively; p < 0.01). The parasternal position gave slightly superior results compared to the apical position (e.g., heart minus planning target volume V_{12.5 Gy} 7.6 % [4.7-13.3] vs. 8.2 % [6.4-12.5]; left lung V_{10 Gy} 3.4 % [1.0-4.5] vs. 4.2 % [1.6-6.8]), albeit in all plans dose guidance parameters remained within clinically acceptable limits.

The ultrasound probe could be spared from the primary beam without compromising photon-based STAR plan quality beyond clinically acceptable deviations. The results support further investigation of ultrasound-based STAR motion management.