# MUSIC: Cardiac Imaging, Modelling and Visualisation Software for Diagnosis and Therapy
## 4 Functionalities
### MRI-Guided Radiofrequency Ablation of Cardiac Arrhythmias  
Radiofrequency (RF) ablation procedures performed under MRI offer the advantage of a non-ionising imaging, providing that appropriate MR-compatible instrumentation (e.g., Vision-MR Ablation Catheter, Imricor Medical Systems, Burnsville, MN, USA) be used. MRI can provide 3D anatomical images of the heart at the beginning of the therapeutic session prior to real-time catheter navigation, online monitoring of therapy and immediate assessment of lesion transmurality. Therefore, such an integrated workflow does not require 3D registration between data acquired prior to and during the therapeutic procedure. Figure 13 shows an example of the use of MUSICardio in such a scenario on a preclinical study. Three-dimensional (3D) images (balanced ssfp sequence) acquired at the beginning of the session served as a road map and were loaded and processed in MUSICardio application (Figure 13a) in less than 5 min to segment (using the polygon ROI feature) right and left ventricle cavities. The resulting volumes were converted into meshes and then loaded in the prototype Monte Carlo platform provided by the MRI manufacturer (Siemens Healthcare, Erlangen, Germany). Real-time 3D catheter navigation was then performed using a dedicated tip-tracking MRI sequence (measuring X, Y and Z positions of MRI micro coils embedded into the catheter tip at an update rate of 40 ms) to precisely position the catheter at a desired location within the cavity (Figure 13b). Catheter position was displayed online in transparency over the original images and the previously computed 3D meshes. Then, RF energy was delivered under MRI thermometry ([15], data not shown) to monitor treatment progression on the fly. After several RF shots performed at different locations within the heart (positioned under 3D real-time tip tracking sequence), a 3D post  
Figure 12: The output results at the end of the pipeline. The VA classification result is shown in the bottom right corner at 98%. The two views show the mesh of the LV wall thickness and classification attention map. The views could be linked together, showing that higher attention (red on left mesh) was placed within the thinning region of the LV (yellow/green on right mesh). The interactive side-by-side display of the thickness and attention map helps to explain the model prediction and increases the user’s confidence in the AI tool.  
ablation T1-weighted MRI sequence (long TI without injection of contrast agent [16]) was run to visualise the lesion core (irreversible thermal coagulation) and surrounding oedema. Then, the wall thickness map of the left ventricle was computed from the epicardium and endocardi masks using a similar pipeline presented in Section 4.6. The segmentation was initially performed manually with MUSICardio, then a dual-UNet segmentation network was trained on the TI-weighted images to accelerate and automate the segmentation during the intervention (<1 min). An arbitrary threshold was applied on TI-weighted 3D images on the LV wall to automatically extract the mask of the RF lesions. This mask was then multiplied by the wall thickness map to create a measure of the lesion transmurality (expressed in percentage), which is a major parameter to assess the therapeutic success of RF ablation. The output result was finally displayed on the interface (Figure 13c), allowing the user to visualise native T1-weighted images and transmurality map within a single graphical interface.