Effect of Collagen and Mineral Content on the High-Frequency Ultrasonic Properties of Human Cancellous Bone

Abstract

The technology surrounding ultrasonic bone assessment is evolving rapidly as investigators explore the utility of new ultrasonic parameters and different ultrasonic frequencies. This study had three main goals. The first was to perform in vitro measurements of the speed of sound (SOS) and normalized broadband ultrasonic attenuation (nBUA) in specimens of normal human cancellous bone using a 2.25 MHz broadband measurement system. The second was to explore the utility of a backscatter-based parameter called apparent integrated backscatter (AIB). The third goal was to investigate the roles that collagen and mineral content play in affecting each of these three ultrasonic parameters. This was accomplished by chemically treating the specimens to remove one or the other of these two important constituents of bone. Our results showed that in most cases SOS and nBUA correlated well (p < 0.05) with bone mineral density (BMD) as measured by quantitative computed tomography (QCT). In contrast, AIB did not correlate strongly with BMD. When the specimens were demineralized, decreases were produced in SOS (19-39%) and nBUA (44-58%). Changes produced in AIB were not significant except along the superoinferior direction, in which a 12% decrease was measured. When the specimens were decollagenized, decreases were produced in SOS (10-12%). In contrast, increases were produced in both nBUA (35-77%) and AIB (14-15%). From this study we conclude that high-frequency ultrasonic measurements may yield useful information about the content and organization of both collagen and mineral in cancellous bone.

Ability of ultrasound backscattering to predict mechanical properties of bovine trabecular bone

“…A similar relationship between backscattering and BMD was found by Nicholson and Bouxsein (2002) in vitro and by Wear and Garra (1998) in vivo. In contrast to those studies, Hoffmeister et al (2000Hoffmeister et al ( , 2002 found no systematic linear relationship between backscattering and BMD. This discrepancy may be attributed to the varying frequency range used in the determination of backscattering, differences between in vitro and in vivo measurement environments and/or differences between human calcaneus and bovine trabecular bone.…”

“…Most QUS examinations are performed in the calcaneus, which is not a typical site of fracture. As suggested by Chaffai et al (2002) and others (Hoffmeister et al 2002;Roux et al 2001), the direct measurement of QUS parameters at fracture sites such as the hip and wrist would probably improve the diagnostic capability of US.…”

“…Therefore, it is related to density and elastic modulus of trabecular bone framework. On the other hand, the association of US backscatter with bone density Chaffai et al 2002), microstructure (Chaffai et al 2002), anisotropy (Wear 2000) and collagen (Hoffmeister et al 2002) or bone marrow contents (Nicholson and Bouxsein 2002) suggests that backscatter measurement could be useful for the prediction of trabecular bone density, structure and composition. Because it has been shown that the mechanical properties of trabecular bone are strongly correlated with BMD vol (Carter and Hayes 1977) and related to trabecular structure (Zysset 2003) and composition of the organic matrix (Burr 2002), one might suggest that US reflection and backscattering are related to bone mechanical properties.…”

“…These techniques use either a phantom (Yao et al 1990) or a standard plane reflector (Roux et al 2001) as reference for the determination of backscattering. Preliminary studies have suggested that backscattering techniques may be applicable clinically (Wear and Garra 1998), although the results have been somewhat contradictory (Chaffai et al 2002;Hoffmeister et al 2000Hoffmeister et al , 2002Nicholson and Bouxsein 2002;Wear et al 2000). Chaffai et al (2002) revealed a significant correlation between BUB and the density or microstructure of the human calcaneal bone in vitro.…”

“…Wear (2000) found the backscatter coefficient to be significantly lower in the anteroposterior direction than in the mediolateral direction in the human calcaneal bone. Hoffmeister et al (2002) studied the effects of collagen and mineral contents on US properties of human cancellous bone and demonstrated sensitivity of the apparent integrated backscatter (AIB) to the collagen content and insensitivity to demineralization. These results support the hypothesis of the suitability of scattering parameters to indicate changes in tissue structure and organic composition.…”