ECG-based 4D-dose reconstruction of cardiac arrhythmia ablation with carbon ion beams: application in a porcine model

Abstract

Noninvasive ablation of cardiac arrhythmia by scanned particle radiotherapy is highly promising, but especially challenging due to cardiac and respiratory motion. Irradiations for catheter-free ablation in intact pigs were carried out at the GSI Helmholtz Center in Darmstadt using scanned carbon ions. Here, we present real-time electrocardiogram (ECG) data to estimate time-resolved (4D) delivered dose. For 11 animals, surface ECGs and temporal structure of beam delivery were acquired during irradiation. R waves were automatically detected from surface ECGs. Pre-treatment ECG-triggered 4D-CT phases were synchronized to the R-R interval. 4D-dose calculation was performed using GSI's in-house 4D treatment planning system. Resulting dose distributions were assessed with respect to coverage (D95 and V95), heterogeneity (HI = D5-D95) and normal tissue exposure. Final results shown here were performed offline, but first calculations were started shortly after irradiation The D95 for TV and PTV was above 95% for 10 and 8 out of 11 animals, respectively. HI was reduced for PTV versus TV volumes, especially for some of the animals targeted at the atrioventricular junction, indicating residual interplay effects due to cardiac motion. Risk structure exposure was comparable to static and 4D treatment planning simulations. ECG-based 4D-dose reconstruction is technically feasible in a patient treatment-like setting. Further development of the presented approach, such as real-time dose calculation, may contribute to safe, successful treatments using scanned ion beams for cardiac arrhythmia ablation.

Biological Cardiac Tissue Effects of High-Energy Heavy Ions – Investigation for Myocardial Ablation

“…The mid-SOBP dose-averaged LET ranged 55–75 keV/µm depending on the size of the SOBP and the initial energy. Two opposing field were optimized separately to deliver the target dose to the AVJ while specifically considering doses to trachea, esophagus and aorta 12 .…”

Image gradient L0-norm based PICCS for swinging multi-source CT reconstruction

“…Third, the L 0 -PICCS is first proposed for SMCT system in this study. In fact, it can be also applied to cardiac CT (4DCT) [1,32,33], spectral CT [34,35]. Particularly, when the proposed L 0 -PICCS is applied to spectral CT reconstruction, the averaged image can be considered as the prior image.…”

Management of organ motion in scanned ion beam therapy

“…Prior animal irradiation the treatment plans were delivered into a water tank using the robotic 4D phantom developed by Steidl et al [ 55 ]. During delivery of these treatment plans and especially during treatment of the animals, the log files of the beam delivery sequence and the ECG trace were recorded such that the delivered 4D dose could be reconstructed [ 56 ].…”

“…No severe radiation induced side effects were seen. Concerning 4D reconstruction of the delivered dose using TRiP4D, Richter et al showed that within 30 min after irradiation a preliminary dose assessment of individual fields was possible [ 56 ]. Target volume D95 dose levels were >95% in all but one animal for which technical reasons could be identified to explain the deviation.…”