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

Background and Purpose 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. Materials and methods 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. Results The ultrasound probe could be spared from the primary beam in all cases with D 0.035 cm 3 < 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-PTV V 12.5 Gy 7.6% [4.7–13.3] vs. 8.2% [6.4–12.5]; left lung V 10 Gy 3.4% [1.0–4.6] vs. 4.2% [1.6–6.8]), albeit in all plans dose guidance parameter remained within clinically acceptable limits. Conclusions 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.