Refining Muscle Morphometry Through Machine Learning and Spatial Analysis.

Aims: Muscle morphology provides important information in differentiating disease aetiology, but its measurement remains challenging because of the lack of an efficient and objective method. This study aimed to quantitatively refine the morphological features of muscle fibres in neuromuscular diseases using machine learning.

Methods: In this retrospective study, we analysed muscle biopsy specimens on haematoxylin and eosin-staining. Machine learning-based software was developed to segment muscle fibre contours and perform automated muscle morphometry and subsequent graph theory-based spatial analysis of atrophied fibre grouping. A decision tree-based framework, LightGBM, was trained to predict underlying aetiologies based on morphometric and spatial variables.

Results: The study included 100 muscle samples, including 20 normal muscles, 49 myopathies and 19 neuropathies. The fine-tuned segmentation model, YOLOv8, achieved a mask average precision of 0.819. The muscle morphometry revealed the significance of fibre circularity. The mean circularity was higher in the myopathy group, and the SD of circularity was elevated in the neuropathy group. Although most cases were consistent with textbook findings, atypical presentations, such as dermatomyositis with angular atrophy and amyotrophic lateral sclerosis with round atrophy, were objectively documented. Spatial analysis quantified grouped atrophy, showing the potential to feature specific atrophy patterns. The LightGBM model successfully predicted the final clinical diagnosis of the myopathies and neuropathies with an accuracy of 0.852, which exceeded that of 0.808 by human annotation.

Conclusion: Automated muscle morphometry and spatial analysis provide quantification of muscle morphology and patterns of atrophy, which will facilitate objective and efficient investigation of neuromuscular diseases.