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Continuous cardiac thermometry via simultaneous catheter tracking and undersampled radial golden angle acquisition for radiofrequency ablation monitoring
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Edité par CCSD ; Nature Publishing Group -
International audience. The complexity of the MRI protocol is one of the factors limiting the clinical adoption of MR temperature mapping for real-time monitoring of cardiac ablation procedures and a pushbutton solution would ease its use. Continuous gradient echo golden angle radial acquisition combined with intra-scan motion correction and undersampled temperature determination could be a robust and more user-friendly alternative than the ultrafast GRE-EPI sequence which suffers from sensitivity to magnetic field susceptibility artifacts and requires ECG-gating. The goal of this proof-of-concept work is to establish the temperature uncertainty as well as the spatial and temporal resolutions achievable in an Agar-gel phantom and in vivo using this method. GRE radial golden angle acquisitions were used to monitor RF ablations in a phantom and in vivo in two sheep hearts with different slice orientations. In each case, 2D rigid motion correction based on catheter micro-coil signal, tracking its motion, was performed and its impact on the temperature imaging was assessed. The temperature uncertainty was determined for three spatial resolutions (1 × 1 × 3 mm 3 , 2 × 2 × 3 mm 3 , and 3 × 3 × 3 mm 3) and three temporal resolutions (0.48, 0.72, and 0.97 s) with undersampling acceleration factors ranging from 2 to 17. The combination of radial golden angle GRE acquisition, simultaneous catheter tracking, intra-scan 2D motion correction, and undersampled thermometry enabled temperature monitoring in the myocardium in vivo during RF ablations with high temporal (< 1 s) and high spatial resolution. The temperature uncertainty ranged from 0.2 ± 0.1 to 1.8 ± 0.2 °C for the various temporal and spatial resolutions and, on average, remained superior to the uncertainty of an EPI acquisition while still allowing clinical monitoring of the RF ablation process. The proposed method is a robust and promising alternative to EPI acquisition to monitor in vivo RF cardiac ablations. Further studies remain required to improve the temperature uncertainty and establish its clinical applicability. Catheter ablation under X-ray fluoroscopy is one of the reference methods for the treatment of arrhythmia 1. Over the past 20 years, tremendous progress 2 have been made in the integration of imaging techniques in these procedures 3,4. The utility of image guidance for atrial fibrillation 5 or ventricular tachycardia 6 ablations has been demonstrated at all stages of the procedures. Nevertheless, clinical outcomes remain conditioned by inherent limitations of the X-ray fluoroscopy modality which cannot depict in real-time the energy delivery to the tissue or the extent of the lesion. Although these markers are governed by the transfer of radiofrequency (RF) energy to the tissue, physiological factors such as the intermittent contact between the catheter and the tissue, the myocardial
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