Spatial-frequency Analysis of the Anatomical Differences in Hamstring Muscles

Spatial frequency analysis (SFA) is a quantitative ultrasound method that characterizes tissue organization. SFA has been used for research involving tendon injury, but may prove useful in similar research involving skeletal muscle. As a first step, we investigated if SFA could detect known architectural differences within hamstring muscles. Ultrasound B-mode images were collected bilaterally at locations corresponding to proximal, mid-belly, and distal thirds along the hamstrings from 10 healthy participants. Images were analyzed in the spatial frequency domain by applying a two-dimensional Fourier Transform in all 6.5 × 6.5 mm kernels in a region of interest corresponding to the central portion of the muscle. SFA parameters (peak spatial frequency radius [PSFR], maximum frequency amplitude [Mmax], sum of frequencies [Sum], and ratio of Mmax to Sum [Mmax%]) were extracted from each muscle location and analyzed by separate linear mixed effects models. Significant differences were observed proximo-distally in PSFR ( p = .039), Mmax ( p < .0001), and Sum ( p < .0001), consistent with architectural descriptions of the hamstring muscles. These results suggest that SFA can detect regional differences of healthy tissue structure within the hamstrings—an important finding for future research in regional muscle structure and mechanics.

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Spatial frequency analysis detects altered tissue organization following hamstring strain injury at time of injury but not return to sport

BMC Medical Imaging ◽

10.1186/s12880-021-00721-1 ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Scott K. Crawford ◽

Christa M. Wille ◽

Mikel R. Stiffler-Joachim ◽

Kenneth S. Lee ◽

Greg R. Bashford ◽

...

Keyword(s):

Spatial Frequency ◽

Frequency Analysis ◽

Return To Sport ◽

Collegiate Athletes ◽

Muscular Tissue ◽

Injured Limb ◽

Contralateral Limb ◽

Hamstring Strain ◽

Tissue Organization ◽

Spatial Frequency Analysis

Abstract Background Hamstring strain injury (HSI) diagnosis is often corroborated using ultrasound. Spatial frequency analysis (SFA) is a quantitative ultrasound method that has proven useful in characterizing altered tissue organization. The purpose of this study was to determine changes in muscular tissue organization using SFA following HSI. Methods Ultrasound B-mode images were captured at time of injury (TOI) and return to sport (RTS) in collegiate athletes who sustained an HSI. Spatial frequency parameters extracted from two-dimensional Fourier Transforms in user-defined regions of interest (ROI) were analyzed. Separate ROIs encompassed injured and adjacent tissue within the same image of the injured limb and mirrored locations in the contralateral limb at TOI. The ROIs for RTS images were drawn to correspond to the injury-matched location determined from TOI imaging. Peak spatial frequency radius (PSFR) and the fascicular banded pattern relative to image background (Mmax%) were compared between injured and adjacent portions within the same image with separate paired t-tests. Within-image differences of SFA parameters in the injured limb were calculated and compared between TOI and RTS with Wilcoxon rank sum tests. Results Within the injured limb at TOI, PSFR differences in injured and healthy regions did not strictly meet statistical significance (p = 0.06), while Mmax% was different between regions (p < 0.001). No differences were observed between regions in the contralateral limb at TOI (PSFR, p = 0.16; Mmax%, p = 0.30). Significant within-image differences in PSFR (p = 0.03) and Mmax% (p = 0.04) at RTS were detected relative to TOI. Conclusions These findings are a first step in determining the usefulness of SFA in muscle injury characterization and provide quantitative assessment of both fascicular disruption and edema presence in acute HSI.

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