Analysis of target motion in STereotactic Arrhythmia Radioablation for atrial fibrillation
PO-2283
Abstract
Analysis of target motion in STereotactic Arrhythmia Radioablation for atrial fibrillation
Authors: Fiorella Cristina Di Guglielmo1, Giuseppe Sanfrancesco1, Christian De Pascali1, Fabiana Gregucci1, Alessia Surgo1, Roberta Carbonara1, Maria Paola Ciliberti1, Morena Caliandro1, Eleonora Paulicelli1, Imma Romanazzo2, Antonio Di Monaco3, Massimo Grimaldi3, Ilaria Bonaparte1, Alba Fiorentino1
1General Regional Hospital "F. Miulli", Department of Radiation Oncology, Acquaviva delle Fonti, Italy; 2G. Rodolico Polyclinic, Department of Cardiology , Catania , Italy; 3General Regional Hospital "F. Miulli", Department of Cardiology, Acquaviva delle Fonti, Italy
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Purpose or Objective
Current guidelines recommend Pulmonary Veins (PVs) isolation with catheter ablation (CA) in patients affected by atrial fibrillation, refractory to antiarrhythmic therapy. A non-invasive Linac-based approach was studied in the phase II trial on STereotactic Arrhythmia Radioablation for atrial fibrillation. The present analysis aims to evaluate the displacements of targets motion during respiratory phases.
Material and Methods
A vac-lock bag was used for patients’ immobilization in the supine position. Three Computed Tomography (CT, 1mm slice-thickness) were performed: 1) free-breathing CT for dose calculation; 2) 4-Dimension CT (4D-CT) for moving evaluation; 3) CT with contrast for anatomical accuracy.
The clinical target volume (CTV) was identified by radiation oncologist and cardiologist and was defined as the area around PVs, generating 2 separate target volumes, one around the left PVs and the other one on the right PVs. All CTVs were propagated to all respiratory phases scans.
Based on 4D-CT, the internal target volume (ITV) was generated from CTVs to encompass heart and respiratory movements. Medial-lateral (M-L), anteriors-posterior (A-P) and superior-inferior (S-I) displacements for center of mass of CTVright and CTVleft were evaluated during all respiratory phases on 4D-CT.
Results
From May 2021 to July 2022, 18 elderly patients were treated: median age was 77,6 years old (range 71-90). In terms of 4D-CT data, a total of 288 CTVs were analyzed (144 CTVS right and 144 CTVs left). the average M-L, A-P and superior-inferior S-I displacements for CTVright and CTVleft were -0.008; 0.001; 0.05; 0.004; -0.04; 0.03 cm, respectively, However, only S-I movements reported a maximum amplitude of 0.6 cm, while for M-L and A-P an amplitude of 0.1 cm was documented.
Conclusion
CTVleft and CTVright displace laterally, A-P and S-I on average of few millimeters (max amplitude 0-0.6 cm). The displacements of CTVLeft and CTVRight were similar during respiratory phases, even if it seems than CTVright was more mobile respect to left for M-L and A-P displacements. In the present cohort of patients treated with STereotactic Arrhythmia Radioablation for atrial fibrillation, 4D-CT emerged as an effective and sufficient tool to valuate target displacement due to internal motion. Consequently, Deep Inspiration Breath Hold or Respiratory gated radiotherapy may be unnecessary.