title: Shear-wave sonoelastography for assessing masseter muscle hardness in comparison with strain sonoelastography: study with phantoms and healthy volunteers.
abstract: Objectives Shear-wave sonoelastography is expected to facilitate low operator dependency, high reproducibility and quantitative evaluation, whereas there are few reports on available normative values of in vivo tissue in head and neck fields. The purpose of this study was to examine the reliabilities on measuring hardness using shear-wave sonoelastography and to clarify normal values of masseter muscle hardness in healthy volunteers. Methods Phantoms with known hardness ranging from 20 to 140 kPa were scanned with shear-wave sonoelastography, and inter- and intraoperator reliabilities were examined compared with strain sonoelastography. The relationships between the actual and measured hardness were analyzed. The masseter muscle hardness in 30 healthy volunteers was measured using shear-wave sonoelastography.
  
  
  RESULTS
  The inter- and intraoperator intraclass correlation coefficients were almost perfect. Strong correlations were seen between the actual and measured hardness. The mean hardness of the masseter muscles in healthy volunteers was 42.82 ± 5.56 kPa at rest and 53.36 ± 8.46 kPa during jaw clenching.
  
  
  CONCLUSIONS
  The hardness measured with shear-wave sonoelastography showed high-level reliability. Shear-wave sonoelastography may be suitable for evaluation of the masseter muscles.
authors.affiliation: 1 Department of Oral and Maxillofacial Radiology, School of Dentistry, Aichi Gakuin University, Nagoya, Japan.
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Ariji
authors.affiliation: 2 Division of Oral and Maxillofacial Radiology, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan.
authors.forename: Miwa
authors.initials: M
authors.lastname: Nakayama
authors.affiliation: 1 Department of Oral and Maxillofacial Radiology, School of Dentistry, Aichi Gakuin University, Nagoya, Japan.
authors.forename: Wataru
authors.initials: W
authors.lastname: Nishiyama
authors.affiliation: 1 Department of Oral and Maxillofacial Radiology, School of Dentistry, Aichi Gakuin University, Nagoya, Japan.
authors.forename: Michihito
authors.initials: M
authors.lastname: Nozawa
authors.affiliation: 1 Department of Oral and Maxillofacial Radiology, School of Dentistry, Aichi Gakuin University, Nagoya, Japan.
authors.forename: Eiichiro
authors.initials: E
authors.lastname: Ariji
mesh_terms: D000328:Adult; D055119:Elastic Modulus; D054459:Elasticity Imaging Techniques / Q000379:methods* / Q000706:statistics & numerical data; D005260:Female; D006244:Hardness; D006801:Humans; D008297:Male; D008406:Masseter Muscle / Q000000981:diagnostic imaging*; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology; D015588:Observer Variation; D019047:Phantoms, Imaging; D012016:Reference Values; D015203:Reproducibility of Results
keywords: masseter muscle; muscle hardness; reliability; shear-wave sonoelastography; sonography