Compartmental relaxation and diffusion tensor imaging measurements in vivo in λ‐carrageenan‐induced edema in rat skeletal muscle

Abstract

Integrated diffusion tensor-T 2 measurements were made on normal and edematous rat muscle, and the data were fitted with one-and two-compartment models, respectively. Edematous muscle exhibited a short-lived component (T 2 = 28 ± 6 ms) with diffusion characteristics similar to that of normal muscle and a long-lived component (T 2 = 96 ± 27 ms) with greater mean apparent diffusion coefficient (ADC) and lower fractional anisotropy (FA). With this two-component description of diffusion and relaxation, values of ADC and FA estimated with a conventional pulsed-gradient spin echo sequence will depend on the echo time, relative fraction of short-and long-lived water signals, as well as the intrinsic ADC and FA values within the tissue. Based on the relative differences in water diffusion properties between long-lived and short-lived water signals, as well as the similarities between the short-lived component and normal tissue, it is postulated that these two signal components are largely reflective of intra-and extra-cellular water.

A 3D Tissue-Printing Approach for Validation of Diffusion Tensor Imaging in Skeletal Muscle

“…The FA and T 2 relaxation values of the phantoms were similar to what has previously been found in normal and edematous muscle, while MD was slightly below what has been previously reported (FA: 0.30 -0.08; MD: 1.52 -0.20*10 -3 mm 2 /s; T 2 : 28 ms-96 ms). 7,17,41 Our results demonstrate that as fiber size decreased, an increase in the FA and a decrease in MD were measurable, which is consistent with in vivo findings. 13 Similarly, the differences in measured diffusion parameters between phantoms generated from normal and denervated muscle geometries are consistent with expected results from the literature and further support the idea that DLP-based 3D printing can be used to fabricate realistic skeletal muscle phantoms or constructs.…”

“…In real tissue, intra-and extracellular diffusions have been separated based on differences in T 2 relaxation between the two compartments using a multiecho DTI sequence. 16,17 In our study, we attempted to replicate these findings using a similar sequence, but were unsuccessful. The different diameter sizes chosen for these models were designed to mimic a range of fiber sizes typically found in human muscles.…”

“…Multiecho DT-MRI techniques have been implemented to compartmentalize diffusion from intra-and extracellular water by combining traditional DT-MRI and T 2 -relaxometry techniques. 16,17 This technique leverages the difference in T 2 -relaxation of water in the intraand extracellular space, theoretically limiting the parameter estimate errors found in traditional single-compartment (single-echo) diffusion techniques. However, uncoupling local inflammation/edema from the underlying microstructural changes in muscle is nearly impossible in vivo because multiple biological processes occur in parallel.…”

Diffusion tensor imaging of the human calf muscle: distinct changes in fractional anisotropy and mean diffusion due to passive muscle shortening and stretching

“…She found clear differences in the fractional anisotropy (FA) and mean diffusivity in injured skeletal muscle compared to healthy subjects. These studies indicate that DTI could play an important role in understanding skeletal muscle organization (8) and pathology (9)(10)(11). DTI has also been applied to the mapping of the myocardium (12)(13)(14)(15)(16).…”

Diffusion-tensor MRI-based skeletal muscle fiber tracking

“…Anisotropic water diffusion in skeletal muscle was subsequently confirmed using the tensor model [46]. Importantly, in a model of muscle inflammation, Fan and Does [75] observed greater diffusion anisotropy in a more slowly diffusing, short transverse relaxation time ( T 2 ) water component (the presumptive intracellular component) than in a more rapidly diffusing, long T 2 water component (the presumptive interstitial water compartment).…”