1Ultrasound imaging has been frequently used for the study of muscle contraction, 2 including measurements of pennation angles and fascicle orientations. However, these 3 measurements were traditionally conducted by manually drawing lines on the 4 ultrasound images. In this study, we proposed a modified Hough transform (HT), 5 aiming at automatically estimating orientations of straight-line-shaped patterns, such 6 as muscle fibers and muscle-bone interface in ultrasound images. The new method 7 first located the global maximum in the HT accumulator matrix, which corresponded 8 to the most dominant collinear feature points globally, using the standard HT; then the 9 pixels close to the detected line were removed from the edge map, the HT 10 accumulator matrix was calculated again, i.e. revoting, and a new line was detected; 11 the iteration was repeated until the predefined termination conditions were satisfied.
12The performance of the algorithm was tested using computer-generated images with