Quantitative MRI of Muscle
Gustav Strijkers1,2

1Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, Netherlands, 2Translational and Molecular Imaging Institute, Mount Sinai School of Medicine, New York, NY, United States

Synopsis

In this educational I will introduce the use of quantitative MRI to study muscle injury and disease and discuss various applications.

Target audience

Clinicians, technologists, and scientists who are interested in applying quantitative MRI techniques to study healthy and diseased skeletal muscle.

Objectives

Participants will learn about the basics of quantitative MRI to probe structure, function, and pathology of skeletal muscle.

Introduction

Skeletal muscles serve critical mechanical and physiological roles in the body. Combined, the approximately 600 muscles in your body are the largest organ in your body comprising about 40% of your body mass. Muscles generate motion and therefore facilitate walking, running, eating, breathing, blood circulation, and peristaltic movements. Additionally, muscles play an important role in the body’s metabolism. Muscle injury and disease therefore often have a direct and profound influence on the quality of life.

Muscle injury and disease

Muscle overuse injury is the most common sports-related injury. It can lead to muscle strains/tears and rupture of the myotendinous junction by overstraining of the myofibers and excessive tensile and shear forces. These types of injury are often accompanied by intra- and intermuscular hematoma and edema. Fortunately, skeletal muscle has a high regenerative capacity but recovery time depends on the severity of the injury.

A pressure ulcer is a form of muscle injury occurring when muscle is subjected to prolonged mechanical load and is particularly common in subjects who are bedridden or wheelchair bound. Typical for a so-called deep tissue injury is that damage formation starts under intact skin at the bone-muscle interface. Deep tissue injuries are difficult to detect and treat and are associated with high treatment costs and increased morbidity and mortality.

Neuromuscular diseases are broadly defined as those that affect the muscles and the peripheral nerves. They are often, particularly at chronic stages, characterized by progressive muscle degeneration and muscle weakness resulting in functional disabilities. Many of them result in chronic disability. Even though neuromuscular diseases have very different causes and pathogenic mechanisms, fibrosis, edema, and fat replacement are frequently observed histological features. There are more than 600 known neuromuscular diseases. Although individually rare, as a group they pose a significant healthcare burden for society, and most of them lack an effective therapy.

Imaging biomarkers

The MRI soft-tissue contrast can be manipulated to sensitize the signal to many different parameters relevant to muscle injury and disease, from edema, fat, fibrosis, perfusion, and oxygenation, to elasticity, motion, and strain. These tissue contrasts can be used as imaging biomarkers of muscle injury and may serve to establish diagnosis, prognosis, or therapeutic response. They may indicate the normal or diseased biological state and serve to investigate disease mechanisms. A drawback of many MRI contrasts is that most of them provide sensitivity without specificity and changes in contrast may reflect a downstream consequence of a more fundamental pathological process.

Quantitative MRI

Quantitative MRI seeks to quantify the fundamental anatomical, structural, biological, or functional tissue properties using MRI. Often, the quantification of tissue relaxation parameters, such as T1, T2, and T2*, is considered quantitative MRI. In a stricter definition, quantitative MRI implicates the quantification of fundamental structural, physiological, metabolic, or functional (non-MRI) tissue parameters, examples of which are: fat-fraction, amount of edema, cell size, vessel wall permeability, tissue elasticity, strain, and tissue perfusion.

Quantitative MRI of muscle

In this educational I will introduce the use of quantitative MRI to study muscle injury and disease and discuss various applications.

Acknowledgements

No acknowledgement found.

References

  1. Strijkers GJ et al. Exploration of New Contrasts, Targets, and MR Imaging and Spectroscopy Techniques for Neuromuscular Disease – A Workshop Report of Working Group 3 of the Biomedicine and Molecular Biosciences COST Action BM1304 MYO-MRI. Journal of Neuromuscular Diseases. 2019 Jan 30;6(1):1–30.
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  6. Li K et al. Multi-parametric MRI characterization of healthy human thigh muscles at 3.0 T - relaxation, magnetization transfer, fat/water, and diffusion tensor imaging. NMR Biomed. 2014 Sep;27(9):1070–84.
Proc. Intl. Soc. Mag. Reson. Med. 27 (2019)