Advanced MR Imaging Techniques for Skeletal Muscle Evaluation

Abstract

Diagnostic imaging procedures for muscle evaluation have typically provided basic information concerning gross anatomical change resulting from pathology. Up until recently the musculoskeletal radiologist has been fairly limited to using simple proton-density weighted fat-saturated and short tau inversion recovery magnetic resonance imaging scans for assessment of skeletal muscle. Recent advances, however, have resulted in development of newer scans and postprocessing methods that provide much more than gross muscle structure. Scans providing fine structure, muscle function, and metabolism can easily be done using clinical scanners. Here we describe how diffusion tensor imaging (DTI) and blood oxygenation level-dependent (BOLD) imaging together can provide detailed information on muscle structural and functional changes. DTI is useful for visualizing muscle tears, and BOLD can be used for vascular insufficiency (e.g., compartment syndrome). In clinical sites that are gaining experience using these techniques, imaging of muscle pathology is becoming increasingly thorough. In the future, these methods will reduce the need for invasive approaches to study muscle pathology.

Blood oxygenation level‐dependent (BOLD) MRI of human skeletal muscle at 1.5 and 3 T

“…T2* changes in gradient-echo (GE) echo-planar-imaging (EPI) sequences can mainly be attributed to changes in the intravascular ratio of oxy-to deoxyhemoglobin of the muscle microvasculature (1)(2)(3)(4)(5). Muscle BOLD imaging has been shown to be capable of detecting disturbances of muscle microperfusion in diseases such as peripheral arterial occlusive disease, chronic compartment syndrome, and ischemic heart disease (6)(7)(8)(9).…”

Diffusion-Weighted Magnetic Resonance Imaging of the Musculoskeletal System: An Emerging Technology With Potential to Impact Clinical Decision Making

“…Because of its relatively high cost and limited availability, DWI of the musculoskeletal is currently used primarily for research and for the clarification of diagnoses that are hard to detect with physical examination and conventional imaging. 8,57 Because of this, the immediate clinical impact of DWI is limited. Numerous studies are currently underway and will provide valuable information regarding the extent to which DWI can influence clinical decision making.…”

“…In some cases, this change might be a favorable event, such as the rapid and short-lived increase in diffusion within the extra-cellular components of muscle that occurs following exercise. 57 In other instances, changes in diffusion can be an unfavorable event, resulting from disease or trauma, and manifests as hematomas, inflammatory responses, edema, neovascularity, or solid tumors. [7][8][9][10]16,24,25 The application of DWI can help to clarify the presence and nature of these events.…”

“…8,57 Measurable differences in the DWI signal intensity between and within different regions of interest selected from an image can reflect differences in the rate of movement of water between and within those regions. 8,28 The signals produced by DWI can, therefore, be thought of as reflecting the velocity of water movement and are thus different from commonly used T1-, T2-, and proton density-weighted spin echo MRI, in which signal intensity is strongly linked to the concentration of water (specifically H+ ions) rather than its actual movement (FIGURE 2).…”

“…For example, it is believed that factors such as variations in capillary density and the concentration of circulating proteins, as well as events such as tissue injury, inflammation, edema, hematoma, electrolyte imbalances, and elevated temperature, can influence diffusion in muscles. 30,35,57,74 The ability to detect and quantify these events will allow clinicians and researchers to determine associations between these findings and patient symptoms, as well as their response to intervention.…”