. 2023 Dec 16;23(24):9873.
doi: 10.3390/s23249873.
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Sensors (Basel).
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Abstract
Myofascial pain syndrome is a chronic pain disorder characterized by myofascial trigger points (MTrPs). Quantitative ultrasound (US) techniques can be used to discriminate MTrPs from healthy muscle. In this study, 90 B-mode US images of upper trapezius muscles were collected from 63 participants (left and/or right side(s)). Four texture feature approaches (individually and a combination of them) were employed that focused on identifying spots, and edges were used to explore the discrimination between the three groups: active MTrPs (n = 30), latent MTrPs (n = 30), and healthy muscle (n = 30). Machine learning (ML) and one-way analysis of variance were used to investigate the discrimination ability of the different approaches. Statistically significant results were seen in almost all examined features for each texture feature approach, but, in contrast, ML techniques struggled to produce robust discrimination. The ML techniques showed that two texture features (i.e., correlation and mean) within the combination of texture features were most important in classifying the three groups. This discrepancy between traditional statistical analysis and ML techniques prompts the need for further investigation of texture-based approaches in US for the discrimination of MTrPs.
Keywords:
machine learning; myofascial trigger point; texture features; ultrasound.
Conflict of interest statement
The authors declare no conflict of interest.
Figures

Figure 1
US transducer location from upper trapezius muscle (x = C7, y = acromion).

Figure 2
(A) An example of a B-mode US image from a participant with active MTrP. The red arrows show the MTrP, a hypoechoic region. (B) An example of a corresponding Gabor-filtered image (at θ = 0 degree) from the same participant. (C) An example of a corresponding LBP from the same participant.

Figure 3
This chart shows a summary of the methods that were used for feature extraction. The red color connections represent the SEGL method, a combination of statistical, edge, and gray-level co-occurrence matrices (GLCM), and local binary pattern (LBP). Note: The numbers in each circle represent each approach.

Figure 4
Confusion matrices of the ML algorithms with the best performance for (A) each approach (B-mode, LBP, Gabor feature, and SEGL) and each approach with the majority vote; (B) a single statistical feature; and (C) the removal of a single statistical feature for discriminating the three groups: A-MTrPs, L-MTrPs, and healthy controls.
References
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Suputtitada A. Myofascial Pain Syndrome and Sensitization. Phys. Med. Rehabil. Res. 2016;1:1–4. doi: 10.15761/PMRR.1000127.
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DOI
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Simons D., Travell J.G., Simons L. Travell & Simons’ Myofascial Pain and Dysfunction: The Trigger Point Manual. 2nd ed. Volume 1 Williams & Wilkins; Baltimore, MD, USA: 1999.
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