Introduction:
Ultrasound imaging (USI) is useful to evaluate structures of the foot to guide treatment, but the reliability of USI technique needs to be clarified. The goal of the study was to evaluate the intra- and inter-examiner reliability of USI image capture, and measurement of the cross-sectional area (CSA) and thickness of the flexor hallucis longus (FHL) for experienced and novice examiners

Material and methods:
FHL images were captured for 20 healthy adults. Reliability of image capture was evaluated between images repeated at 10-min interval for an experienced and a novice examiner. Reliability of image-based measurements was evaluated for one experienced and one novice rater, using all images. The intra-class correlation coefficient (ICC) and the standard error of measurement (SEM) were calculated

Results:
Intra-examiner reliability of image capture for the FHL muscle examined by USI was excellent for both thickness (ICC3,1, 0.944–0.976; SEM, 6.8%–10.0%) and CSA (ICC3,1, 0.954–0.979; SEM, 10.8%–16.5%), with no effect of examiner experience. Reliability was also excellent for measurement of thickness (ICC3,1, 0.954–0.972; SEM, 1.2%–9.6%) and CSA (ICC3,1, 0.961–0.986; SEM, 9.2%–14.1%), with no effects of experience.

Conclusions:
Reliability of image capture and image-based measurements developed by USI of CSA and thickness for the FHL muscle in healthy individuals was excellent, independent of the examiner experience.