title: Assessment of contractile and noncontractile components in human skeletal muscle by magnetic resonance imaging.
abstract: A magnetic resonance imaging (MRI) technique for the assessment of contractile and noncontractile components of human skeletal muscle is described, and the inter-rater and intra-rater test-retest reliability for repeated measurements from the same MR image are examined. Twenty cross-sectional MR images from the right lower leg were obtained from 30 healthy young men and women (mean age 24.1 years, SD 3.3). The anatomical cross-sectional area (aCSA; cm2), the cross-sectional area of noncontractile components (Noncon; cm2), the contractile cross-sectional area (cCSA = aCSA minus Noncon; cm2), and the relative amount of Noncon (%), of the ankle dorsiflexor muscle compartment were determined for each slice using a computer-based image analysis system. Reliability for repeated measurements of the slice with the largest aCSA for the 30 subjects was analyzed by two raters on two different occasions. Inter-rater reliability on both occasions, assessed by the intraclass correlation coefficient (ICC), was excellent for cCSA (ICC3.1 = 0.99) and Noncon (ICC(3.1) > 0.82). Intra-rater (between occasions) reliability was excellent for the two raters for measurements of cCSA (ICC1.1 = 0.99) and Noncon (ICC1.1 > 0.94). Bland and Altman analyses did not identify any clinically relevant bias in the measurements. Method errors were acceptable: within subjects coefficients of variation (CV) was less than 1.8% for cCSA and less than 16.3% for Noncon. It is concluded that repeated measurements of contractile and noncontractile components of the ankle dorsiflexor muscle compartment, obtained from the same MR image, are highly reliable.
authors.affiliation: Department of Physical Therapy, Lund University Hospital, SE-22185 Lund, Sweden. Anna_Maria.Holmback@sjukgum.lu.se
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Holmbäck
authors.forename: Krister
authors.initials: K
authors.lastname: Askaner
authors.forename: Stig
authors.initials: S
authors.lastname: Holtås
authors.forename: David
authors.initials: D
authors.lastname: Downham
authors.forename: Jan
authors.initials: J
authors.lastname: Lexell
mesh_terms: D000328:Adult; D000842:Ankle; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D018482:Muscle, Skeletal / Q000033:anatomy & histology* / Q000502:physiology*; D015588:Observer Variation