title: Intramuscular changes of soft and hard areas after low-level static contraction of the masseter muscle and the correlations with muscle hardness and increase in water content: evaluations with sonographic elastography and magnetic resonance imaging.
abstract: OBJECTIVE
  To investigate the intramuscular changes on sonographic elastography (SE) after low-level static contraction of the masseter muscle, and to clarify the relationship with the total hardness and edematous change.
  
  
  METHODS
  Ten healthy volunteers performed sustained bilateral biting at 20% of maximal voluntary contraction for 10 min. The SE and magnetic resonance (MR) scans of the masseter muscles were performed before, immediately after, and 10 min after exercise. The masseter muscle elasticity index (MEI) ratio, muscle thickness, and intramuscular soft and hard areas distribution were evaluated on SE images. The signal to noise ratio (SNR), indicating the water content, was measured on MR images.
  
  
  RESULTS
  The soft area ratio showed significant correlations with the water content expressed as SNR. The hard area ratio showed significant correlations with the total muscle hardness expressed as the MEI ratio.
  
  
  CONCLUSIONS
  Intramuscular soft and hard areas could be used both clinically and experimentally.
authors: Department of Oral and Maxillofacial Radiology, Aichi-Gakuin University School of Dentistry, Nagoya, Japan. yoshiko@dpc.agu.ac.jp
authors: Yoshiko
authors: Y
authors: Ariji
authors: Miwa
authors: M
authors: Nakayama
authors: Akira
authors: A
authors: Taguchi
authors: Akihiko
authors: A
authors: Gotoh
authors: Yoshitaka
authors: Y
authors: Kise
authors: Aakitoshi
authors: A
authors: Katsumata
authors: Kenichi
authors: K
authors: Kurita
authors: Eiichiro
authors: E
authors: Ariji
mesh_terms: D000328:Adult; D001732:Bite Force; D004487:Edema / Q000000981:diagnostic imaging; D054459:Elasticity Imaging Techniques / Q000379:methods*; D005157:Facial Pain / Q000000981:diagnostic imaging; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008406:Masseter Muscle / Q000000981:diagnostic imaging / Q000502:physiology*; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology*; D018709:Statistics, Nonparametric; D013705:Temporomandibular Joint Disorders / Q000503:physiopathology