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

Abstract

Purpose To describe a semi-automated program that will segment subcutaneous fat, muscle, and adipose tissue in the foot using magnetic resonance (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 r2 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.

Acquired midfoot deformity and function in individuals with diabetes and peripheral neuropathy

“…(Supplementary table) The measurement methods for calf and foot muscle and fat are reported in detail in previous publications. 32, 33 Briefly, calf muscle and fat images were acquired while the participant lay supine with a Siemens extremity coil surrounding the involved leg. Images with and without fat saturation were collected beginning at the tibiofemoral joint and continued distal.…”

Muscle and Joint Factors Associated With Forefoot Deformity in the Diabetic Neuropathic Foot

“…7 Few studies have investigated the relationship between intrinsic foot muscle deterioration and MTPJ deformity, and with conflicting results. 9,10,13,32 We hypothesized that there were other factors that combine with muscle deterioration to cause MTPJ deformity and these are depicted in Figure 1. In particular, we hypothesized that limited ankle mobility combines with intrinsic foot muscle deterioration to contribute to MTPJ hyperextension deformity.…”

Imaging near orthopedic hardware

“…The effects of magnetic susceptibility artifact are commonly manifested in 3 forms: signal voids, voxel pileup, and distortion, the magnitude of which is proportional to the susceptibility differences between water and the offending material (43). Voxel pileup results from in-plane and through plane geometric shifting of signal from its original location to be superimposed with spins of similar frequencies, increasing the amplitude of the recorded signal.…”

“…Where d is the calculated theoretical through-plane displacement, Δ υ is the frequency offset at the point of interest (kHz), FOV is the in-plane field-of-view (mm), R BW is the receiver bandwidth (kHz), ST is the slice thickness (mm), and S BW is the slice-select bandwidth (kHz) (43). As an example, a total hip arthroplasty device composed of a cobalt-chromium alloy within the field of view will create off resonance effects of approximately 5kHz (43).…”

“…As an example, a total hip arthroplasty device composed of a cobalt-chromium alloy within the field of view will create off resonance effects of approximately 5kHz (43). Using imaging parameters recommended for in vivo 2D fast-spin-echo (FSE) imaging of THA (38) (field-of-view of 18cm, receiver bandwidth of ±100 kHz (390 Hz/pixel), excitation bandwidth of 1 kHz and slice thickness of 4 mm, one can anticipate an in-plane distortion of 4.5 mm, and associated through-plane distortion of 20.5 mm near the implanted metallic device.…”