Purpose: Each dynamic elastography contains multiple images; therefore, physicians need to determine the most representative image from the scanned sequence to make diagnosis. To eliminate interobserver variations on diagnoses and help doctors providing correct treatments, the authors developed an objective computer-aided diagnostic scheme without requiring manually selecting representative images for diagnosis.
Methods: About 112 histological-proven lesions including 66 benign and 46 malignant tumors were involved as the material database. Suspicious lesions were automatically segmented on the first B-mode images on each captured dynamic elastography. Tissue strains inside lesions on elastograms were classified by utilizing the fuzzy c-means algorithm. In order to reduce the influence of image quality, important tumor characteristics were computed from every strain images in elastography and regressed to a probability of being malignant. Since tumor boundaries changed slightly between adjacent slices, a tumor boundary tracking scheme based on template matching was applied on slices excepting the first one.
Results: The diagnostic accuracy, sensitivity, specificity, positive predictive value, and negative predictive value are 85.71% (96∕112), 86.96% (40∕46), 84.85% (56∕66), 80.00% (40∕50), and 90.32% (56∕62). In addition, the area under the receiver operating characteristic curve is 0.9016.
Conclusions: The authors' proposed study provides a reliable computer-aided system which helps physicians to make diagnoses according to features computed from entire elastographic sequence. Experimental results illustrate that the diagnostic scheme is sufficient in distinguishing benign and malignant tumors. It is not necessary for physicians to spend a lot of time to determine the most suitable image for diagnosis. The tumor boundary tracking mechanism effectively eliminates the computation time since it slightly adjusts tumor boundaries between neighboring slices instead of segmenting the tumor contour on each image in the dynamic elastography. The system sufficiently reduces the variations of diagnosis caused by operator dependencies and image qualities and furthermore save physicians' workloads.