MR-Based Assessment of Bone Marrow Fat in Osteoporosis, Diabetes, and Obesity

Abstract

Bone consists of the mineralized component (i.e., cortex and trabeculae) and the non-mineralized component (i.e., bone marrow). Most of the routine clinical bone imaging uses X-ray-based techniques and focuses on the mineralized component. However, bone marrow adiposity has been also shown to have a strong linkage with bone health. Specifically, multiple previous studies have demonstrated a negative association between bone marrow fat fraction (BMFF) and bone mineral density. Magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) are ideal imaging techniques for non-invasively investigating the properties of bone marrow fat. In the present work, we first review the most important MRI and MRS methods for assessing properties of bone marrow fat, including methodologies for measuring BMFF and bone marrow fatty acid composition parameters. Previous MRI and MRS studies measuring BMFF and fat unsaturation in the context of osteoporosis are then reviewed. Finally, previous studies investigating the relationship between bone marrow fat, other fat depots, and bone health in patients with obesity and type 2 diabetes are presented. In summary, MRI and MRS are powerful non-invasive techniques for measuring properties of bone marrow fat in osteoporosis, obesity, and type 2 diabetes and can assist in future studies investigating the pathophysiology of bone changes in the above clinical scenarios.

Quantitative MRI and spectroscopy of bone marrow

“…Multiple studies demonstrated the ability of bone microstructure parameters as surrogate marker of bone quality to improve fracture risk prediction beyond BMD . The bone marrow as a nonmineralized bone component has recently drawn attention with regard to the pathogenesis of osteoporosis . The bone marrow affects bone metabolism in several ways.…”

Quantitative imaging methods in osteoporosis

“…Protonmagnetic resonance spectroscopy ( 1 H-MRS) is considered the MRI gold standard for bone marrow fat quantification, and point-resolved spectroscopy (PRESS) and stimulated echo acquisition mode (STEAM) single-voxel 1 H-MRS pulse sequences have been commonly used for the characterization of the fat spectrum in the bone marrow at the pelvis, spine, and hip (95). Images are acquired using dedicated coils to detect and quantify frequency signals of water, lipids, and other metabolites, expressed as universal ppm (parts per million) units with evaluation of areas under the peaks.…”

Unsaturation level decreased in bone marrow fat of postmenopausal women with low bone density using high resolution magic angle spinning (HRMAS) 1H NMR spectroscopy

“…Some evidence suggests that bone marrow adipocytes inhibit osteoblast activity and may promote osteoclast differentiation (5–7). Clinically, increased marrow fat measured by magnetic resonance imaging (MRI) or 1 H-MR spectroscopy ( 1 H-MRS) has been reported in subjects with decreased bone mineral density (BMD) (8–11), as well as in other pathologies including anorexia nervosa and diabetes, which were nicely reviewed in references (12–14). …”