Incorporating Electroanatomic Mapping Data into Radiation Treatment Planning for Stereotactic Cardiac Radioablation

Summary: Catheter-based conventional radiofrequency ablation, a state-of-the-art treatment for ventricular tachycardia (VT), can be challenging, with a 30 percent failure rate in initial treatments and about 50 percent in the long term. Utilizing stereotactic body radiation therapy (SBRT) for refractory patients or those not suitable for conventional ablation is an evolving therapeutic paradigm with promising early results. However, accurately localizing the target area in the treatment planning system (TPS), a prerequisite for precise image-guided treatment, remains a significant challenge. Seamlessly and consistently incorporating Electroanatomic Mapping (EAM) into SBRT is complicated by image formats that are not readily interoperable across vendors and platforms. We offer a step-by-step tutorial to facilitate offline fusion of standard Digital Imaging and Communications in Medicine (DICOM) CT simulation images with non-DICOM EAM maps in open-source 3D Slicer to bridge the interoperability divide between EAM and TPS software. In two patients with VT, we used EA Map Reader, an open-source 3D Slicer plugin, to import and read carefully annotated EAM data containing outlines of the scar, the ventricle, and any identifiable cardiac substructures into a DICOM format. Upon conversion, the software creates a closed surface representing the outlined cardiac scar and other cardiac substructures. The imported structure set is then fused with CT image slices and the mapped scar representing the arrhythmogenic endocardial/epicardial substrate is defined as our treatment target. A DICOM RT structure file is then exported as a linked dataset for use within the routine fusion platform/module of the TPS. Once fused, radiation treatment planning proceeds as standard practice and treatment is delivered as per standard of care. We focused on two patients who were ideal candidates for SBRT to treat refractory VT. Both patients experienced recurrent VT episodes, as indicated by data from their Implantable Cardioverter Defibrillators (ICDs). They had previously undergone radiofrequency ablation but remained refractory. We used the EAM data from their ablation procedures, converted it to DICOM format, and fused it with CT images in the TPS to target the ablation via SBRT. These patients responded to treatment quickly and effectively based on follow-up evaluations. Accurate incorporation of EAM maps into radiation TPSs facilitates utilization of EAM-defined cardiac substructures and targets as additional aids in defining target volumes for stereotactic cardiac radioablation. Our pipeline for EAM incorporation into the TPS serves as a critical bridge between functional information gathered by electrophysiologists and anatomic information used by radiation oncologists in delineating a treatment target with confidence, enhancing the effectiveness of SBRT and fostering closer collaboration between electrophysiology and radiation oncology, ultimately leading to more accurate and effective treatment outcomes. Khashayar Fattah, MD (Presenting Author) - University of Tennesse Medical center Knoxville; Sunil Krishnan, MD, FACP, FASTRO, FAIMBE, FRSC, FInstP (Co-Author) - UTHealth Houston; Alejandro Vidal Margenat, MD (Co-Author) - UTHealth Houston/ UT Physicians EP Heart – Complex Arrhythmia Center; Khashayar Hematpour, MD (Co-Author) - UTHealth Houston/ UT Physicians EP Heart – Complex Arrhythmia Center; Ramesh Hariharan, MD, MRCP (UK) FACC, FHRS (Co-Author) - UTHealth Houston/ UT Physicians EP Heart – Complex Arrhythmia Center