Author: Hongyu An, Phillip Cuculich, H Michael Gach, Yao Hao, Trevor McKeown, Clifford Robinson, Yuhao Wang, Deshan Yang 👨🔬
Affiliation: Washington University School of Medicine in St. Louis, Washington University School of Medicine, Duke University, Department of Radiation Oncology, Duke University, Washington University in St. Louis, Department of Radiation Oncology, Washington University School of Medicine in St. Louis 🌍
Purpose: This study investigated cardiac motion characteristics of ventricular tachycardia patients to support patient-specific motion management for stereotactic arrhythmia radiotherapy (STAR) treatments.
Methods:
Breath-hold cardiac 4DCTs (c4DCT) from 11 STAR-treated patients were retrospectively analyzed. Each c4DCT included ten 3DCTs representing the full cardiac cycle. A group-wise deformable image registration (DIR) method registered the 3DCTs, producing ten 3D deformation vector fields and an average position 3DCT. Metal artifacts from Implantable Cardioverter-Defibrillator leads were reduced using diffusion before DIR. Heart chambers were segmented on the average 3DCT using AI segmentation and manual corrections. Cardiac motion characteristics were computed, including magnitude and direction on myocardium walls and STAR targets.
Results: Cardiac motion characteristics were found to be highly patient-specific. The maximum, 99th percentile and 95th percentile of myocardium wall motion referring to the average position ranged from 9.9 to 17.7 mm, 6.3 to 11.2 mm, and 2.9 to 8.9 mm respectively. The same metrics for STAR target motion ranged from 3.0 mm to 11.6 mm, 2.6 to 5.9 mm, and 2.4 to 5.2 mm respectively. The motion distributions were also strongly patient-specific. Common features were: 1) The motion magnitudes in the myocardium wall and STAR target followed a left-skewed distribution and the 95th percentile of the motion magnitudes were within 5 mm for 10 out of 11 patients; 2) The largest motion always appeared near the ventricle-atrium (AV) valves; and 3) The targets had a smaller maximum motion than the myocardium because STAR targets are commonly located at the outside myocardium wall, away from the AV valves.
Conclusion: A novel image processing method was developed to analyze cardiac motion in c4DCT images. Application on 11 patients revealed that cardiac motion is predominantly patient-specific, though some high-level attributes are shared. Patient-specific management is crucial for STAR treatments.