In Vivo Assessment of Bone Quality Without X-rays

Abstract

Purpose of review: This review summarizes recent advances in the assessment of bone quality using non-X-ray techniques.

Recent findings: Quantitative ultrasound (QUS) provides multiple measurements of bone characteristics based on the propagation of sound through bone, the attenuation of that sound, and different processing techniques. QUS parameters and model predictions based on backscattered signals can discriminate non-fracture from fracture cases with accuracy comparable to standard bone mineral density (BMD). With advances in magnetic resonance imaging (MRI), bound water and pore water, or a porosity index, can be quantified in several long bones in vivo. Since such imaging-derived measurements correlate with the fracture resistance of bone, they potentially provide new BMD-independent predictors of fracture risk. While numerous measurements of mineral, organic matrix, and bound water by Raman spectroscopy correlate with the strength and toughness of cortical bone, the clinical assessment of person's bone quality using spatially offset Raman spectroscopy (SORS) requires advanced spectral processing techniques that minimize contaminating signals from fat, skin, and blood. Limiting exposure of patients to ionizing radiation, QUS, MRI, and SORS has the potential to improve the assessment of fracture risk and track changes of new therapies that target bone matrix and micro-structure.

Keywords: Bone quality; Bound water; Fracture risk; Magnetic resonance imaging; Pore water; Quantitative ultrasound; Radiofrequency echographic multi-spectrometry; Raman spectroscopy.

Figure 1:. Clinical tools for the assessment of bone mass (mineral density) and bone quality (micro-structure and various tissue characteristics) with and without ionizing radiation.

The hierarchical arrangement of bone, ranging from the macro-structure (left) to the ultra-structure (right), confers multiple ‘toughening’ mechanisms to keep bone from breaking upon a fall to the ground or due to daily cyclic loading that accumulates damage over time (A). As such, multiple techniques are being developed to quantify different attributes of bone at key length scales of the bone hierarchy (B). The μMRI image was reproduced from Rajapakse, C.S., Leonard, M.B., Bhagat, Y.A., Sun, W., Magland, J.F., and F.W. Wehrli. Micro–MR Imaging–based Computational Biomechanics Demonstrates Reduction in Cortical and Trabecular Bone Strength after Renal Transplantation. Radiology. 262(3):912-20, 2012 (published by the Radiological Society of North America). The QUS image was reproduced from Raum, K., Laugier, P. (2022). Clinical Devices for Bone Assessment. In: Laugier, P., Grimal, Q. (eds) Bone Quantitative Ultrasound. Advances in Experimental Medicine and Biology, vol 1364. (published by Springer)