title: Dynamic measurement of pennation angle of gastrocnemius muscles during contractions based on ultrasound imaging.
abstract: BACKGROUND
  Muscle fascicle pennation angle (PA) is an important parameter related to musculoskeletal functions, and ultrasound imaging has been widely used for measuring PA, but manually and frame by frame in most cases. We have earlier reported an automatic method to estimate aponeurosis orientation based on Gabor transform and Revoting Hough Transform (RVHT).
  
  
  METHODS
  In this paper, we proposed a method to estimate the overall orientation of muscle fascicles in a region of interest, in order to complete computing the orientation of the other side of the pennation angle, but the side found by RVHT. The measurements for orientations of both fascicles and aponeurosis were conducted in each frame of ultrasound images, and then the dynamic change of pennation angle during muscle contraction was obtained automatically. The method for fascicle orientation estimation was evaluated using synthetic images with different noise levels and later on 500 ultrasound images of human gastrocnemius muscles during isometric plantarflexion.
  
  
  RESULTS
  The muscle fascicle orientations were also estimated manually by two operators. From the results it's found that the proposed automatic method demonstrated a comparable performance to the manual method.
  
  
  CONCLUSIONS
  With the proposed methods, ultrasound measurement for muscle pennation angles can be more widely used for functional assessment of muscles.
authors.affiliation: Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China. yj.zhou@siat.ac.cn
authors.forename: Yongjin
authors.initials: Y
authors.lastname: Zhou
authors.forename: Ji-Zhou
authors.initials: JZ
authors.lastname: Li
authors.forename: Guangquan
authors.initials: G
authors.lastname: Zhou
authors.forename: Yong-Ping
authors.initials: YP
authors.lastname: Zheng
mesh_terms: D000328:Adult; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008297:Male; D009119:Muscle Contraction; D018485:Muscle Fibers, Skeletal / Q000000981:diagnostic imaging* / Q000502:physiology*; D013710:Tendons / Q000502:physiology; D014463:Ultrasonography / Q000379:methods*