Test-retest Reliability Of An Ultrasound Probe Guide System

Brightness mode (B-mode) ultrasound is a popular, non-invasive imaging modality used to assess skeletal muscle size. While popular, it is paramount for accuracy and reliability that these images are acquired by a trained and experienced technician. Otherwise, it is difficult to obtain high-quality and repeatable scans. A recent custom-built ultrasound probe guide (PGT) has recently been developed, which may reduce measurement error and increase the reliability of ultrasound imaging. PURPOSE: The purpose of this study was to assess the test-retest reliability between the PGT and traditional (TRAD) ultrasound imaging for the measurement of muscle volume of the vastus lateralis (VL). METHODS: 40 participants (mean ± SD: age = 21 ± 3 yrs; BMI = 24.5 ± 4.2 kg/m2) completed one visit to the laboratory where each participant underwent non-invasive B-mode imaging on their VL across four separate image acquisition sessions, each separated by 10 minutes. Two trials utilized the PGT while the other two trials used the TRAD method. The PGT consisted of a customized cradle which was 3D printed to fit the exact dimensions of the ultrasound probe used in this study. To acquire images, the cradle, which controlled the pitch and yaw of the probe, was then placed on custom-designed tracks on which it glided during a cross-sectional plane ultrasound scan. Anatomical cross-sectional area (ACSA) was quantified every 1.5 cm along the length of the VL, which was standardized based on the capabilities of the PGT. During the two TRAD trials, scans occurred in the same locations as the PGT trials. Muscle volume was estimated using the Cavalieri technique with the ACSA scans. Test-retest reliability statistics (i.e., interclass correlation coefficients [ICC] model 2,1, standard error of measurement as a percentage of the mean [SEM], and the minimal difference [MD] values needed to be considered real) were quantified. RESULTS: Both the PGT method (ICC2,1 = 0.96, SEM = 3.56%, MD = 6.98 cm3) and TRAD (ICC2,1 = 0.98, SEM = 2.41%, MD = 4.73 cm3) demonstrated good reliability. CONCLUSIONS: The findings from the present investigation suggest that the TRAD and PGT have excellent reliability when used to quantify VL muscle volume, but the TRAD may have less error and variability between scans compared to PGT.