Techniques and applications of skeletal muscle diffusion tensor imaging: A review

Abstract

Diffusion tensor imaging (DTI) is increasingly applied to study skeletal muscle physiology, anatomy, and pathology. The reason for this growing interest is that DTI offers unique, noninvasive, and potentially diagnostically relevant imaging readouts of skeletal muscle structure that are difficult or impossible to obtain otherwise. DTI has been shown to be feasible within most skeletal muscles. DTI parameters are highly sensitive to patient-specific properties such as age, body mass index (BMI), and gender, but also to more transient factors such as exercise, rest, pressure, temperature, and relative joint position. However, when designing a DTI study one should not only be aware of sensitivity to the above-mentioned factors but also the fact that the DTI parameters are dependent on several acquisition parameters such as echo time, b-value, and diffusion mixing time. The purpose of this review is to provide an overview of DTI studies covering the technical, demographic, and clinical aspects of DTI in skeletal muscles. First we will focus on the critical aspects of the acquisition protocol. Second, we will cover the reported normal variance in skeletal muscle diffusion parameters, and finally we provide an overview of clinical studies and reported parameter changes due to several (patho-)physiological conditions.

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.…”

“…Diffusion tensor magnetic resonance imaging (DT-MRI) is a method that has been used to noninvasively measure the anisotropic restricted diffusion of water in tissue, which is related to its underlying microstructure. [5][6][7] For example, muscle cells are long columnar structures with a surrounding membrane Departments of 1 Bioengineering, 2 Nanoengineering, 3 Radiology, and 4 Orthopaedic Surgery, University of California San Diego, La Jolla, California.…”

“…However, the relationship between the DT-MRI signals and the tissue microstructure and physiology is exceedingly complex. Thus, while DT-MRI parameters have been shown to be sensitive to skeletal muscle changes associated with injury, age, and chronic pathology, 7 these studies are nonspecific and, therefore, of limited clinical value. Microstructural and microfluidic changes associated with these conditions include fiber atrophy, fibrosis, edema, and increased sarcolemma permeability, all of which theoretically change diffusion of water in muscle.…”

“…Microstructural and microfluidic changes associated with these conditions include fiber atrophy, fibrosis, edema, and increased sarcolemma permeability, all of which theoretically change diffusion of water in muscle. 7,[10][11][12][13] In vivo, the presence of increased extracellular water due to edema/inflammation in injured muscle has been shown to strongly effect and may dominate the diffusion signal even when concurrent microstructural changes have an opposing diffusion profile. 10,12,14,15 Increased extracellular water content is normally observed on MRI as an increase in the T 2 relaxation value of the tissue.…”

A MRI-Compatible Combined Mechanical Loading and MR Elastography Setup to Study Deformation-Induced Skeletal Muscle Damage in Rats

“…Exactly how anisotropy is reflected in analyses based on isotropic inversion methods is currently unknown, and may also relate to the directions wave happen to locally follow. However, when combined with MRI-compatible force sensing, diffusion tensor-based fiber architecture assessment, and inverse FEA, the presented methods do offer a means to assess such effects in the future [86,90,96–98]. This is because the initial anisotropy and non-linear elastic behavior would be accurately reflected in FEA based on such measurements, and elastic tensor data for any state of deformation can be directly compared to MRE findings.…”