Effect of collagen and mineral content on the high-frequency ultrasonic properties of human cancellous bone.

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.

Low-megahertz ultrasonic properties of bovine cancellous bone.

Ultrasound offers a noninvasive means to detect changes that occur to the density of cancellous bone as a result of degenerative diseases such as osteoporosis. Techniques based on the velocity and frequency dependence of attenuation of ultrasonic pulses propagated through cancellous bone have proven sensitive to bone density. Most previous studies have investigated these two parameters in the frequency range of 0.1-1.0 MHz. The present study had two goals. The first was to measure three ultrasonic parameters: longitudinal mode velocity; broadband ultrasonic attenuation (BUA); and apparent integrated backscatter (AIB), at higher frequencies using a broadband 2.25 MHz measurement system. The second goal was to assess the dependence of these parameters on bone density. Twenty-one specimens of cancellous bone acquired from the proximal end of four bovine tibiae were investigated in this study. The apparent density of the specimens (determined with the bone marrow removed and the specimens thoroughly dry) ranged between 0.3 and 0.9 g/cm(3). Ultrasonic measurements were performed along three mutually perpendicular directions corresponding to the anteroposterior (AP), mediolateral (ML), and superoinferior (SI) axes of the tibia. A linear regression was used to analyze the results of these measurements as a function of apparent density. Velocity demonstrated a highly significant linear increase with density for all three directions (AP: p < 0.001; ML: p < 0.001; SI: p < 0.01). AIB decreased with density in all three directions; however, only the ML and SI directions demonstrated a significant linear correlation (AP: p = n.s.; ML: p < 0.05; SI: p < 0.05). In the frequency range 0.5-1.0 MHz, BUA exhibited a significant linear increase in the AP and ML directions, but not the SI direction (AP: p < 0.05; ML: p < 0.01; SI: p = n.s.). In contrast, in the frequency range 1.0-2.0 MHz, BUA exhibited a highly significant increase with density in the SI direction, but no significant change in the AP and ML directions (AP: p = n.s., ML: p = n.s., SI: p < 0.001).