Correlation study of scanning acoustic microscope reflection coefficients and image brightness intensities of micrographed osteons

Abstract

Scanning acoustic microscopy (SAM) of Haversian bone at high frequency clearly shows differences in the brightness (gray) levels of individual osteons, which were observed to correspond to the differences in reflection coefficients measured with the SAM technique: the darker the bony regions on the SAM micrographs, the lower the SAM reflection coefficient values, and vice versa. We studied the correlation between differences in brightness and the related reflection coefficients of osteons on undecalcified transverse sections of goat tibial diaphysis using a 400-MHz burst mode lens on the Olympus UH3 SAM. Results showed that there was a strong linear correlation between brightness intensities and the corresponding reflection coefficients, with a correlation coefficient r = 0.99 ( P << 0.001) using gray level 210 as cutoff. This result suggested that the image brightness intensity of osteonic bone could be measured retrospectively to provide information on the stiffness of the corresponding bone matrix.

Imaging Mineralized Tissues in Vertebrates

“…206 Frequencies of 400 MHz and 1 GHz are commonly used, providing a resolution of 3-1 mm. 202,207 The frequency of 2 GHz (2000 MHz), being the highest practical frequency available, results in a resolution of about 0.4 mm. For sample preparation, it is crucial that the surface roughness is smaller than the wave length of the acoustic probe, because scratches and local inclination will change the propagation of the incident waves.…”

“…The amplitude and the timing of the echo pulses allow mapping local mechanical (elastic) properties of the specimen with spatial resolution up to 1 mm (see Figure 12). [202][203][204][205] Three different approaches can be used for assessing elastic properties of bone. 205 (1) Time of flight measurements of pulse echoes from the frontal and backside sample surface in thin tissue sections.…”