Po-04-095 accurate eam-based target delineation in stereotactic arrhythmia radioablation of vt

Stereotactic Arrhythmia Radiotherapy (STAR) aided by precise image-guided delivery and respiratory motion management has been used successfully for experimental treatment of refractory VT. However, accurate target selection remains challenging. Current methods often rely on manual delineation and/or visual estimation of predefined cardiac segments. Develop a systematic process for registering VT targets from electroanatomic maps (EAM) to reference imaging coordinates of the planning CT (pCT) used for radiation treatment. The goal is to minimize potential variations in target site selection as well as treated volumes. In patients on antiarrhythmic treatment and undergoing a 2nd unsuccessful VT ablation, EA maps of the LV (and LA/RV when possible) and more focal maps of VT target sites were acquired (CARTO®3, Biosense-Webster, CA, USA) and exported. In-house software was used to register these to a planning image set and convert them to DICOM structure files (Fig 1). Dice similarity coefficients were calculated between ventricular mesh data and corresponding reference contours. Initial targets (GTV) were expanded to include internal target volumes (ITV) and planning target volumes (PTV) to account for respiratory and cardiac motion and residual uncertainties, with minor manual adjustments guided by consensus among electrophysiologists, radiation oncologists and medical physicists. STAR was delivered as a single fraction of 25 Gy using volumetric-modulated arc therapy or dynamic conformal arc therapy depending on the target shape. 7 patients with refractory VT were treated by defining targets based on registering individualized EAM maps on the planning images. Dice similarity indices between transferred reference map and reference contours were 0.83 ± 0.04 and 0.72 ± 0.04 for LV and LA/RV, respectively (table 1). The median clinical target was 22cc, with PTVs ranging from 62.4 to 199.6 cc. All patients demonstrated a significant reduction in VT events by 6 weeks post STAR. We have developed an effective methodology for direct registration of VT targets selected for STAR, based on direct anatomic registration of individualized EA maps acquired during ablation procedures. This process offers a way to efficiently delineate variable target boundaries in a semi-automated way, which is advantageous when unusual contours make standard segmentation inaccurate and visual estimation difficult. However, rigorous comparison with other approaches remains to be done.Tabled 1Patient-specific metrics1234567Dice, LV0.8680.8450.7910.8060.7210.8720.794Dice, LA/RV0.7520.6670.734N/A0.382N/A0.338GTV (cc)22.313.526.520.759.863.927.2ITV (cc)45.529.142.230.959.8127.829.6PTV (cc)98.662.488.275.5166.8199.672.8 Open table in a new tab