Quantitative sodium magnetic resonance imaging of cartilage, muscle, and tendon

Abstract

Sodium magnetic resonance imaging (MRI), or imaging of the 23Na nucleus, has been under exploration for several decades, and holds promise for potentially revealing additional biochemical information about the health of tissues that cannot currently be obtained from conventional hydrogen (or proton) MRI. This additional information could serve as an important complement to conventional MRI for many applications. However, despite these exciting possibilities, sodium MRI is not yet used routinely in clinical practice, and will likely remain strictly in the domain of exploratory research for the coming decade. This paper begins with a technical overview of sodium MRI, including the nuclear magnetic resonance (NMR) signal characteristics of the sodium nucleus, the challenges associated with sodium MRI, and the specialized pulse sequences, hardware, and reconstruction techniques required. Various applications of sodium MRI for quantitative analysis of the musculoskeletal system are then reviewed, including the non-invasive assessment of cartilage degeneration , imaging of tendinopathy, applications in the assessment of various muscular pathologies, and assessment of muscle response to exercise.

Biomarkers for equine joint injury and osteoarthritis

“…Sodium MR imaging is also correlated to GAG, but requires special equipment and high field strength for scanning . T2 and T2* imaging can be used to characterize collagen content within articular cartilage, but often require long scan times . Diffusion weighted techniques measure water diffusion through the matrix and appear to have promise in best characterizing matrix integrity …”

“…65 T2 and T2 Ã imaging can be used to characterize collagen content within articular cartilage, but often require long scan times. 66 Diffusion weighted techniques measure water diffusion through the matrix and appear to have promise in best characterizing matrix integrity. 67 Standing low-field MRI systems have been useful in the horse for identifying osseous pathology, which appears to carry various (but ill-defined) risks of sustaining catastrophic injury, 68,69 but their usefulness is limited to the distal limb; because of low quality resolution only rudimentary visualization of the articular cartilage is possible limiting early identification of cartilage pathology.…”

Quantitative techniques for musculoskeletal MRI at 7 Tesla

“…While all of the above techniques are based on the NMR signal from the 1H nucleus in tissues, it is also possible to form MRI images from other nuclei, such as 23Na (sodium) (48). However, each nucleus has a unique characteristic frequency of the NMR signal (called the Larmor frequency).…”

A new RF transmit coil for foot and ankle imaging at 7T MRI

“…Magnetic resonance imaging (MRI) has been used to investigate a wide range of abnormalities, injuries and diseases related to musculoskeletal tissues, such as cartilage degeneration [1,2], bone marrow edemas [3], osteoarthritis [2–5], osteoporosis [2,6], and ligament/tendon insures [5,7]. While most of the clinical applications relies on images acquired at 1.5 or 3 Tesla (T) scanners, the enhanced contrast and signal-to-noise ratio (SNR) provided by ultra-high field (UHF, ≥7T) MRI can be highly attractive for musculoskeletal imaging [8].…”