Reliability and validity of a MR-based volumetric analysis of the intrinsic foot muscles

Purpose To describe a semi-automated program that will segment subcutaneous fat, muscle, and adipose tissue in the foot using MR imaging, determine the reliability of the program between and within raters, and determine the validity of the program using MR phantoms. Materials and Methods MR images were acquired from 19 subjects with and without diabetes and peripheral neuropathy. Two raters segmented and measured volumes from single MR slices at the forefoot, midfoot, and hindfoot at two different times. Intra- and inter-rater correlation coefficients were determined. Muscle and fat MR phantoms of known volumes were measured by the program. Results Most ICC reliability values were over 0.950. Validity estimates comparing MR estimates and known volumes resulted in r ² values above 0.970 for all phantoms. The root mean square error was less than 5% for all phantoms. Conclusion Subcutaneous fat, lean muscle, and adipose tissue volumes in the foot can be quantified in a reliable and valid way. This program can be applied in future studies investigating the relationship of these foot structures to functions in important pathologies, including the neuropathic foot or other musculoskeletal problems. J. Magn. Reson. Imaging 2013;38:1083-1093. © 2013 Wiley Periodicals, Inc.