## 4 Discussion  
In the present research work, the problem of segmentation in planning MR images for the HIFU therapy was addressed. A set of methods and parameters to perform identification of objects in the planning MR images was analyzed in a parametric study supported by the evaluation of segmentation quality with F-measure and the analysis of means of the measurement variables with [PERSON]'s ANOVA. For the segmentation of the air region, the results given by the threshold method yielded a greater median value than the WSAM in both the transverse and sagittal images. Moreover, there was a significant difference between the groups of results given by both the threshold method and the WSAM. This fact leads to consider the threshold method as the more convenient choice over the WSAM to perform the segmentation of this region. For the segmentation of the gel-pad region, the results given by the WSAM did not present significant differences between the groups of results obtained with the GAC method in transverse images and with the DRLSE method in the sagittal images. Despite this fact, the results given by the WSAM yielded F-measure values that were higher than those obtained with the other methods. WSAM was then considered as a suitable choice to perform the segmentation of this region. For the segmentation of the tissue region, the WSAM is the choice to carry out the segmentation of this region, given the fact that this segmentation strongly depends on the gel-pad region where WSAM was deemed the most appropriate method. For the segmentation of the transducer region, the results given by the WSAM did not present significant difference with the group of results obtained with the DRLSE method in transverse images. However, the WSAM yielded a higher F-measure median value than the obtained with the DRLSE method, so the WSAM was considered the most appropriate choice to perform the segmentation. For sagittal images, the GAC method was the most suitable choice as it yielded a greater F-measure median value than the WSAM with a significant difference between the groups of results given by both methods. The planning MR images for the treatment of abscesses with MRgHIFU in a murine model, used in the present research work, have specific characteristics such as a FOV of \(120\times 120\times 48\) mm, a pixel size of 0.5 mm and the presence of intensity inhomogeneity and five regions of interest. However, the planning MR images for other experimental setups may present differences. The dimensions of the FOV and the pixel size may be different from those used in the current experimental setup. Moreover, the tissue region may be larger if another animal model is used in the experimental setup, and the gel-pad region may be absent or if the target region is located a different anatomical area of the animal model. In addition, the problem of intensity inhomogeneity may be absent. These conditions may facilitate the application of the implemented segmentation methods and even better results could be achieved. Level set methods (GAC and DRLSE) and WSAM proved to have enough capacity to solve the problem of segmentation in the current experimental setup, with functional results. However, there are limitations in the implemented segmentation methods such as the need to establish an initial contour for both the GAC and the DRLSE methods. Currently, this procedure is performed after the division of the MR image, an action that is performed by the user. Another limitation is the relative complexity in the procedure for the definition of markers of the WSAM. There is no limitation in the shape for the required markers for the WSAM, so simpler markers could be defined in a less complex procedure. Once this action has been achieved, an image segmentation solution based on a single method, the WSAM, would be available. However, the definition of markers is a procedure that previously requires the division of the MR image.