Integration of ultrasound‐guided motion management into proton therapy treatment plans for ventricular tachycardia non‐invasive radio ablation

Stereotactic arrhythmia radioablation (STAR) is an emerging, non-invasive treatment for refractory ventricular arrhythmias. The technology requires target motion management. We studied the integration of a novel ultrasound probe and holder for heart motion management into proton-beam STAR treatment plans. Data were collected in eight of the 23 patients enrolled to-date, in an ongoing prospective, multicenter, observational in silico study comparing treatment planning with photons versus proton radiotherapy in patients affected by Ventricular Tachycardia with indication for catheter ablation procedure. In such subgroup of patients hands-free transthoracic echocardiography was performed in apical and parasternal positions, followed by planning Computed Tomography with ultrasound probe positions marked on the chest. A total of eleven targets were contoured and, for the proton therapy part, pencil beam scanning intensity-modulated proton therapy plans were optimized, assuming cardio-respiratory (dual) gated delivery. In all eleven cases, it was possible to avoid beams intercepting the probe and the dosimetric constraints were fulfilled. In four cases, the position of the probe did not interfere with the beam angles defined a-priori. In four cases, beam angles had to be modified to avoid intercepting the probe but the modified plan was equivalent to the a-priori plan. In three cases, the modified plans included beams with longer penetration depth compared to the a-priori plan, but all planning constraints were fulfilled. These results support the feasibility of using the novel ultrasound probe and holder for heart motion management. The technology would facilitate dedicated patient setup, monitoring and cardiorespiratory gating for STAR using proton beams.