MRI assessment of bone structure and microarchitecture

Abstract

Osteoporosis is a disease of weak bone and increased fracture risk caused by low bone mass and microarchitectural deterioration of bone tissue. The standard-of-care test used to diagnose osteoporosis, dual-energy x-ray absorptiometry (DXA) estimation of areal bone mineral density (BMD), has limitations as a tool to identify patients at risk for fracture and as a tool to monitor therapy response. Magnetic resonance imaging (MRI) assessment of bone structure and microarchitecture has been proposed as another method to assess bone quality and fracture risk in vivo. MRI is advantageous because it is noninvasive, does not require ionizing radiation and can evaluate both cortical and trabecular bone. In this review article, we summarize and discuss research progress on MRI of bone structure and microarchitecture over the last decade, focusing on in vivo translational studies. Single center, in vivo studies have provided some evidence for the added value of MRI as a biomarker of fracture risk or treatment response. Larger, prospective, multicenter studies are needed in the future to validate the results of these initial translational studies.

Diffusion MRI for Assessment of Bone Quality; A Review of Findings in Healthy Aging and Osteoporosis

“…Trabecular bone is predominantly present at the ends of long bones around joints and within the axial skeleton with a 3D network of plates and struts immersed in bone marrow and encased with a relatively thin layer of compact bone . The microarchitecture of trabecular bone delivers tissue resistance against the applied loading forces and contributes to bone strength independently of bone mass …”

“…Changes to the microstructure of trabecular bone in osteoporosis can be detected indirectly by visualizing signal voids within the hyperintense signal of the bone marrow. With development of new acquisition methods, motion compensation, and postprocessing techniques in MRI, analysis of the 3D meshwork of the trabecular bone in resolutions of 100–200 μm has become possible …”

“…The roles of various MRI methods for characterization of cortical and trabecular bone, and bone marrow, have been described in several review articles (quantitative MRI(/S) of bone marrow; cortical and/or trabecular bone imaging) . Table provides various characteristics of bone during aging and osteoporosis that can be identified by different MRI methods.…”

The robustness of T2 value as a trabecular structural index at multiple spatial resolutions of 7 Tesla MRI

“…However, trabecular bone is typically about 100‐150‐µm thick with a complex structure, and resolving 3D micro‐architectural information for accurate image quantification via CT is limited by elevated radiation doses . Recent advances in 3D micro‐MRI (in‐plane resolution < 250 µm 2 and slice thickness < 1.5mm, approximately 15‐minute scan time) acquisition is attractive with no risk associated with radiation exposure, and promising results for trabecular microstructural quantifications were reported . However, motional degradation during elongated 3D scan times along with the required SNR (>10) often limit the spatial resolution and pose burdens on the post‐image processing and reproducibility of MR trabecular quality assessments, primarily because the quality of structural indices, via 3D MRI acquisition and subsequent image processing, quickly degrade with worsening spatial resolution, as demonstrated in the previous investigations …”

What is changed in the diagnosis of osteoporosis: the role of radiologists

“…MRI findings may correlate to the clinical aspects of OP and predict the risk of bone fracture (34)(35)(36)(37)(38)(39)(40)(41).…”