Key result
Single-fraction cardiac SABR workflow proves feasible for refractory VT.
Why the study?
Cardiac radioablation for ventricular tachycardia involves a complex procedure requiring a detailed workflow and stringent dose constraints compared to conventional radiation therapy.
Does a specific institutional workflow for single-fraction cardiac VT-SABR ensure robust treatment planning and target motion verification in patients with refractory ventricular tachycardia?
Case Report (n=2)
No
Does a specific institutional workflow for single-fraction cardiac VT-SABR ensure robust treatment planning and target motion verification in patients with refractory ventricular tachycardia?
A dedicated institutional workflow for cardiac VT-SABR ensures robust treatment planning and accurate target motion verification, though meeting dose constraints for adjacent organs can be challenging.
Supports feasibility of single-fraction cardiac SABR in refractory VT; hypothesis-generating and requires prospective validation before practice change.
PURPOSE: Cardiac radioablation is a novel, non-invasive treatment for ventricular tachycardia (VT), involving a single fractional stereotactic ablative body radiotherapy (SABR) session with a prescribed dose of 25 Gy. This complex procedure requires a detailed workflow and stringent dose constraints compared to conventional radiation therapy. This study aims to establish a consistent institutional workflow for single-fraction cardiac VT-SABR, emphasizing robust plan evaluation and quality assurance. MATERIALS AND METHODS: The study developed a consistent institutional workflow for VT-SABR, including computed tomography (CT) simulation, target volume definition, treatment planning, robust plan evaluation, quality assurance, and image-guided strategy. The workflow was implemented for two patients with cardiac arrhythmia. Accurate target volume definition using planning CT images and electronic anatomical mapping was critical. A four-dimensional (4D) cone-beam CT (CBCT) and breath-hold electrocardiographic gated CT images reliably detected target motion. RESULTS: The resulting plans exhibited a conformity index greater than 0.7 and a gradient index around G4.0. Dose constraints for the planning target volume (PTV) aimed for 95% or higher PTV dose coverage, with a maximum dose of 200% or lower. However, one case did not meet the PTV dose coverage due to the proximity of the PTV to gastrointestinal organs. Plans adhered to dose constraints for organs at risk near the heart, but meeting constraints for specific cardiac sub-structures was challenging and dependent on PTV location. CONCLUSION: The plans demonstrated robustness against respiratory motion and patient positional uncertainty through a robust evaluation function. The 4D and intra-fractional CBCT were effective in verifying target motion and setup stability.
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Kim et al. (2024) conducted a case report in Refractory ventricular tachycardia (n=2). Stereotactic ablative body radiotherapy (SABR) was evaluated on Establishment of institutional workflow and plan robustness (conformity index, gradient index, PTV coverage). A single-fraction cardiac stereotactic ablative body radiotherapy workflow delivering 25 Gy was successfully implemented in two patients with refractory ventricular tachycardia.
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