Interobserver variability in target definition for stereotactic arrhythmia radioablation.

Area of Science:

• Cardiology
• Medical Physics
• Radiotherapy

Background:

• Stereotactic arrhythmia radioablation (STAR) is an emerging therapy for refractory ventricular tachycardia (VT).
• Accurate delineation of the arrhythmogenic substrate is crucial for effective STAR treatment.
• This study assesses the initial interobserver variability in defining the target for STAR.

Purpose of the Study:

• To evaluate the baseline interobserver variability in delineating the ventricular tachycardia (VT) target for STAR.
• To establish a benchmark for future studies aiming to reduce observer variation in STAR procedures.
• To assess the consistency of target definition using different approaches.

Main Methods:

• Ten electrophysiologists participated in a three-phase delineation study using research software.
• Phase 1 involved delineating a spinal canal structure; Phase 2 involved delineating VT targets from case descriptions.
• Phase 3 required delineating predefined segments from the 17-segment model, with basic workflow and no advanced techniques.

Main Results:

• Low interobserver variability (Dice: 0.97) was observed for the well-defined spinal canal structure.
• High interobserver variability (Dice: 0.40 for VT-target, 0.31 for segments) was found for VT-target and ventricular segment delineation.
• Significant variation in distance to the median volume (RMS-SD: 0.52-1.55 cm) indicated poor agreement for VT-related structures.

Conclusions:

• Manual delineation of the VT-target and ventricular segments for STAR exhibits substantial interobserver variability.
• The findings highlight the need for standardized methods and tools to enhance consistency in target definition for STAR.
• This baseline assessment provides a foundation for evaluating interventions designed to reduce observer variability in STAR and catheter ablation.