Linac-based STereotactic Arrhythmia Radioablation (STAR) for ventricular tachycardia: a treatment planning study

To analyze geometrical approaches, prescription modalities, and delivery efficiency for linear accelerator (Linac)-based STereotactic Arrhythmia Radioablation (STAR) for ventricular tachycardia. The anatomy and planning target volume (PTV) of the first Italian STAR patient were used. To assess geometrical approaches, 3 plans prescribed to 75% isodose-line, differing for number, length of arcs, and couch rotations, were generated and compared (Plans#1–3). Volumetric-arc with 6-MV flattening-filter-free (FFF) was employed. To evaluate prescription modality and delivery, the best geometrical plan was compared with other plans prescribed on 70%, 65%, and 60% isodose-line and with another one using 10MV-FFF beams (Plans#4–7). For Plans#1–3, PTV coverage, mean cardiac dose, monitor units (MUs), and beam-delivery-time (BDT) were 96–98.5%, 4.9–5.2 Gy, 7047–7790, and 5–6 min, respectively. Plans#4–7 were similar in terms of mean cardiac dose, MUs and BDT to Plans#1–3, except in maximum dose and lower time for 10MV-FFF plan. Linac-based STAR is safe and efficient in terms of BDT and MUs. To ensure high dose to PTV, different dose prescription modalities should be evaluated. The 10FFF approach was the faster but not suitable in patient with cardiac implantable electronic devices.