Pranav Bhagirath

67 Evaluation of state-of-the-art segmentation algorithms for left ventricle infarct from late Gadolinium enhancement MR images from 2D images, a patient could be subjected to certain therapeutic strategies, such as an implantable cardioverter defibrillator (ICD) implantation or ventricular ablation. 3D images provide more detailed quantification of infarct and only the porcine dataset within this framework are 3D non-isotropic acquisitions. A third limitation is the manner in which the Dice metric is computed individually on each region of infarction labeled by the consensus. The Dice is computed only within ROIs enclosing each consensus- labeled infarct. Outside these regions, the Dice is not accountable. Thus, algorithms which over-segment can still exhibit a good Dice but poor volume error. The Dice need to be combined with the volume error to give a clearer understanding. Intensity variation across the images due to coil shading may have an impact on segmentation, especially for methods which process absolute signal intensities. A coil sensitivity scan is a routine part of the acquisition protocol used to acquire the datasets of this study. However, no further coil sensitivity correction was carried out. This was in- line with the principal of this study to use only routine MRI scans. A final limitation is that only one observer was employed to segment the myocardial masks. The observer was a cardiologist with several years of experience in CMR assessment of LV function assessment and ischemic heart diseases. The issue of variability with different myocardial masks is counteracted by providing the human observers with these masks. The algorithms are also provided with the same masks. This ensures that infarct within the mask are labeled and computed. Thus, the evaluation is only carried out in the myocardial mask space. Evaluated algorithms Quantifying infarct in the LV can have important clinical implications. A 3D rendering of the LVwith infarct areas canbe integrated into electro-anatomical systems for facilitating catheter ablation. As the resolution and SNR of LGE CMR continues to improve, detailed quantification of infarct is becoming possible. The pitfalls of fixed thresholding models advocated in past literature (Amado et al., 2004; Kim et al., 1999) have been highlighted in recent studies (Harrison et al., 2014). Fixed thresholdmodel makes crude assumptions about the contrast levels between nulled blood pool and infarct, deeming a fixed cut- off threshold. However, as these contrast levels are directly dependent on the inversion time selected in LGE CMR, the preset threshold often requires user readjustments. The algorithms were evaluated based on the slice position (basal, mid and apical) (see figure 7 ). In the analysis, there was no significant difference between the basal and mid slices. The apical slices showed better overlap for some algorithms. However, apical slices enclose a smaller myocardial area and thus the overlap assessments in these