Pre- and post-skeletal muscle biopsy quantitative magnetic resonance imaging reveals correlations with histopathological findings

Background and purpose: Quantitative muscle magnetic resonance imaging (MRI) is a promising non- invasive method in the diagnostic workup as well as follow- up of neu-romuscular disorders. The aim of this study was to correlate quantitative MRI (qMRI) parameters to histopathological changes in skeletal muscle tissue and thus to verify the data from our pilot study. Methods: Twenty-six patients (eight females, 46.4 +/- 15.1 years) were examined within 72 h before and within 24 h after a skeletal muscle biopsy using quantitative muscle MRI. Post- biopsy MRI was employed to pinpoint the exact localization of the biopsy. qMRI parameters including fat fraction, water T2 relaxation time and diffusion metrics includ -ing fractional anisotropy, mean diffusivity, axial diffusivity and radial diffusivity were ex -tracted from the localization of the biopsy and correlated with histopathological findings. Additionally, three different segmentation masks were applied to the qMRI dataset, to evaluate whether the whole muscle represents the exact biopsy location. Results: Fat fraction and water T2 relaxation time in qMRI correlated significantly with the fat fraction in the muscle biopsy and histopathological inflammatory markers. Fractionalanisotropy correlated with the quantity of type 2 fibres, whilst mean diffusivity corre -lated with p62. No differences were found using different segmentation masks in qMRI. Conclusions: In this follow- up study, the results from our previous study were verified regarding the correlation of qMRI parameters with histopathological features in muscle biopsies, indicating that qMRI serves as a suitable non- invasive method in the follow- up of patients with neuromuscular disorders. If post- biopsy MRI is not available, whole mus -cle volume can be used for histopathological correlations.