Results and Conclusions

The goal of automatic tissue characterization is to identify the different kind of plaques in IVUS images. This process requires two tasks: identification of what the plaque is and labelling of the different areas of the plaque. Figure 2.18 illustrates roughly the procedure of supervised tissue characterization. The IVUS image (see Fig. 2.18(a)) is preprocessed and sent to the automatic tissue characterization system. Figure 2.18(b) illustrates the physicians-assisted segmentation of IVUS, which will constitute a part of the training dataset. Figure 2.18(c) shows the first step, the accurate location of the lumen-plaque border and the adventitia border. Between both borders, the plaque is the region of interest to be classified. Figure 2.18(d) exemplifies the tissue characterization process. We are focussed on the plaque, and try to find and label areas corresponding to different plaques. In the figure, light gray areas are soft plaque, white areas are fibrotic plaque, and dark gray areas are calcium plaque. At the end of the process we obtain the tissue characterized IVUS (Fig. 2.18(e)) to be used by

Figure 2.18: The tissue characterization process can be done manually by physicians (a) and (b) or by an automatic process (a), (c), (d), and (e). (c) Segmentation of the lumen-plaque border and adventitia border. (d) Processed image of the plaque characterization. (e) Final IVUS tissue characterization.

Figure 2.18: The tissue characterization process can be done manually by physicians (a) and (b) or by an automatic process (a), (c), (d), and (e). (c) Segmentation of the lumen-plaque border and adventitia border. (d) Processed image of the plaque characterization. (e) Final IVUS tissue characterization.

the physicians. These results have been used to validate against the manually segmented plaque regions (Fig. 2.18(b)).

Therefore, though we are concerned with tissue characterization, we cannot forget the segmentation of the plaque. A brief review on how to segment the plaque is exposed in the next section.

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