Enhancement of muscle fibers in ultrasound images using Gabor filters

In this study, the Gabor filter bank technique was applied to the biceps and gastrocnemius ultrasound images to longitudinally enhance the coherently oriented and hyperechoic perimysiums regions. The method involved three steps, orientation field estimation, frequency map computation and Gabor filtering. The method was evaluated using a simulated image distorted with multiplicative speckle noises, where the “muscles” were arranged in a bipennate fashion with a central “aponeurosis”. After the enhancement using the proposed method, most of the original hyperechoic bands in the simulated image could be recovered and the noises in other locations were greatly reduced. The proposed method was also tested on biceps sonograms collected from 4 healthy adult subjects. Based on the filtering results, the hyperechoic regions, especially the fibroadipose septas, could be enhanced in several aspects, such as the completion of broken but coherently oriented regions. It is believed that the proposed method have potentials in assisting the visualization of strongly oriented patterns in ultrasound images and especially the quantitative estimation of muscle thickness, muscle fiber pennation angle and fascicle length.