The diagnostic value of biexponential apparent diffusion coefficients in myopathy

Abstract

To investigate the performance of a biexponential signal decay model using DWI in myopathies and to differentiate Polymyositis (PM)/Dermatomyositis (DM), Glycogen Storage Diseases (GSDs) and Muscular Dystrophies (MDs) utilizing diffusion-weighted imaging. 11 healthy volunteers (control group) and 46 patients with myopathy were enrolled in the retrospective study. 27 of 46 patients had PM/DM, 7 patients GSDs and 12 patients MDs. After conventional MR sequences, diffusion weighted imaging with a b-factor ranging from 0 to 1200 s/mm(2) was performed on both thighs. The intra-muscular signal-to-noise ratios (SNRs) on multiple-b DWI images were measured for 7 different muscles and compared among the different groups. The median T2 signal intensity and biexponential apparent diffusion coefficients (ADC), including standard ADC, fast ADC, and slow ADC values, were compared among the different groups. The intra-muscular SNRs were statistically significantly different depending on the b value, and also found among the 4 groups (p < 0.05). The median T2 signal intensity of the normal muscles in control group was statistically significantly lower than that of edematous muscles in the PM/DM, GSDs and MDs groups (p = 0.000), while there were no statistically significant differences among the PM/DM, GSDs, and MDs groups (p > 0.05). The median standard ADC value of the edematous muscles in GSDs was statistically significantly lower than that of normal muscles in the control group (p = 0.000) and the median ADC value of the edematous muscles in PM/DM patients was statistically significantly greater than that of the GSDs (p = 0.000) and MDs groups (p = 0.005). The median slow ADC value of the edematous muscles in MDs patients and PM/DM patients was statistically significantly greater than that of GSDs patients (p < 0.05). Intra-muscular SNR decay curves and biexponential ADC parameters are useful in distinguishing among PM/DM, GSDs, and MDs.

Associations between apparent diffusion coefficient and electromyography parameters in myositis—A preliminary study

“…As mentioned above, Ran et al. () reported a significantly lower ADC value than the control group, which supports our result.…”

“…Later, the diffusion might be elevated due to necrosis of the muscle fibers with more free diffusion space for water molecules. Previously, only few studies investigated possible diagnostic value for DWI in myositis (Meyer et al., ; Qi et al., ; Ran et al., ). One study showed a lower ADC value for diseased muscles compared to nondiseased control muscles (Ran et al., ), whereas two studies identified a higher ADC value in affected muscles (Meyer et al., ; Qi et al., ).…”

“…For example, it is commonly mentioned in oncologic imaging that ADC min reflects different microstructural aspects in tumors better than ADC mean or ADC max (Surov et al., ). However, in the above‐mentioned myositis studies, only a mean ADC value was used (Meyer et al., ; Qi et al., ; Ran et al., ). In the present study, ADC max did not show significant correlations, whereas ADC mean and ADC min did so.…”

Advancements in magnetic resonance imaging‐based biomarkers for muscular dystrophy

“…Various investigators have examined the use of DWI in muscle . Although acute ischemia is not a pathologic feature of most muscle diseases, the replacement of muscle with fat can similarly restrict the directionality of water flow within the muscle.…”

Diffusion‐weighted magnetic resonance imaging is useful for assessing inflammatory myopathies

“…In inflammatory myopathies, the pathological changes are characterized by degeneration and regeneration of muscle fibers, necrosis, inflammatory cell infiltration, and fibrous hyperplasia that could affect the diffusion of water molecules within muscles . The increased diffusion of water molecules in edematous muscles reflects active inflammation, which can result in an increase in water content and an increase in the transmembrane movement of water molecules across endomysium and sarcolemma within muscles …”