Reliability of assessing skeletal muscle architecture and tissue organization of the gastrocnemius medialis and vastus lateralis muscle using ultrasound and spatial frequency analysis

Abstract

IntroductionThe purpose of this study was to investigate inter- and intra-rater reliability as well as the inter-rater interpretation error of ultrasound measurements assessing skeletal muscle architecture and tissue organization of the gastrocnemius medialis (GM) and vastus lateralis (VL) muscle.MethodsThe GM and VL of 13 healthy adults (22 ± 3 years) were examined thrice with sagittal B-mode ultrasound: intraday test-retest examination by one investigator (intra-rater) and separate examinations by two investigators (inter-rater). Additionally, images from one investigator were analysed by two interpretators (interpretation error). Muscle architecture was assessed by muscle thickness [MT], fascicle length [FL], as well as superior and inferior pennation angle [PA]. Muscle tissue organization was determined by spatial frequency analysis (SFA: peak spatial frequency radius, peak −6 dB width, PSFR/P6, normalized peak value of amplitude spectrum [Amax], power within peak [PWP], peak power percent). Reliability of ultrasound examination and image interpretation are presented as intraclass correlation coefficient (ICC), test-retest variability, standard error of measurement as well as bias and limits of agreement.ResultsGM and VL demonstrated excellent ICCs for inter- and intra-rater reliability, along with excellent ICCs for interpretation error of MT (0.91–0.99), showing minimal variability (<5%) and SEM% (<5%). Systematic bias for MT was less than 1 mm. For PA and FL poor to good ICCs for inter- and intra-rater reliability were revealed (0.41–0.90), with moderate variability (<12%), low SEM% (<10%) and systematic bias between 0.1–1.4°. Tissue organization analysis indicated moderate to good ICCs for inter- and intra-rater reliability. Notably, Amax and PWP consistently held the highest ICC values (0.77–0.87) across all analyses but with higher variability (<24%) and SEM% (<18%), compared to lower variability (<9%) and SEM% (<8%) in other tissue organization parameters. Interpretation error of all muscle tissue organization parameters showed excellent ICCs (0.96–0.999) with very low variability (≤1%) and SEM% (<2%), except Amax & PWP (TRV%: <6%; SEM%: <7%).ConclusionOur findings demonstrated excellent inter- and intra-rater reliability for MT. However, agreement for PA, FL, and SFA parameters was not as strong. Additionally, MT and all SFA parameters exhibited excellent agreement for inter-rater interpretation error. Therefore, the SFA seems to offer the possibility of objectively and reliably evaluating ultrasound images.

Reproducibility of freehand vs. foam cast as well as the intrarater reliability of foam cast ultrasound scans assessing the muscle architecture and tissue organization of the gastrocnemius medialis and vastus lateralis muscles

“…Initially, the measurement locations of GM and VL were marked on the dominant (right) leg of all participants. To recover the marked measurement location in the ultrasound images, a thin strip of echoabsorptive tape was placed 1.5 cm proximal to the previously marked measurement location ( 5 ). GM and VL were assessed under the resting condition.…”

“…The FL was calculated from the visible FL (FL1) plus the calculated FL (FL2), according to Baudry et al ( 17 ). Subsequently, all ultrasound images were imported into MATLAB (MathWorks, USA, R2016a) to conduct SFA to analyze muscle tissue organization as described by Bashford et al ( 4 ) and recently updated ( 5 ). The ROI was selected in a standardized manner by measuring a 1 cm wide rectangular area of the GM and VL from the upper to the lower aponeuroses at the measurement location ( 5 ).…”

“…Subsequently, all ultrasound images were imported into MATLAB (MathWorks, USA, R2016a) to conduct SFA to analyze muscle tissue organization as described by Bashford et al ( 4 ) and recently updated ( 5 ). The ROI was selected in a standardized manner by measuring a 1 cm wide rectangular area of the GM and VL from the upper to the lower aponeuroses at the measurement location ( 5 ). The six resulting spatial frequency parameters were peak spatial frequency radius (PSFR), peak −6 dB width (P6), PSFR/P6 (Q6), normalized peak value of amplitude spectrum (Amax), power within peak (PWP), and peak power percent (PPP) ( 5 ).…”

“…Recently, not only the muscle architecture but also the muscle tissue organization ( 2 , 3 ) has been quantified for acute and chronic adaptations in muscles indicating the overall tissue integrity at the micromorphological level. To analyze muscle tissue organization, spatial frequency analysis (SFA) can be conducted, following the methodology outlined by Bashford et al ( 4 , 5 ). SFA is a quantitative ultrasound method that examines the anisotropic B-mode speckle pattern produced by a tissue type in the spatial frequency domain.…”

“…To obtain meaningful information on muscle architecture and tissue organization from ultrasound imaging, standardization of image acquisition [i.e., probe placement, probe rotation, probe orientation (e.g., angle), and probe pressure] is necessary ( 7 – 9 ). In a previous report ( 5 ), the inter- and intrarater reliability of freehand (FH) ultrasound measurements assessing the skeletal muscle architecture and tissue organization of the gastrocnemius medialis (GM) and vastus lateralis (VL) muscle was assessed. The findings demonstrated poor to excellent intraclass correlation coefficients (ICCs: 0.41–0.99) with very low to moderate test–retest variability (TRV, 3%–11%) for the inter- and intrarater reliability of muscle architecture as well as poor to good ICCs (0.29–0.87) with very low to moderate TRV (3%–14%).…”