Water Bath and Contact Methods in Ultrasonic Evaluation of Bone

Abstract

Ultrasonic devices for the measurement of speed of sound (SOS) and broadband ultrasonic attenuation (BUA) generally use either a contact or water bath method. The aim of this study was to compare these two methods while determining the influence of soft tissue, pathlength (heel width and bone width), and a fixed heel dimension on SOS (m/second) and BUA (dB/MHz). Ultrasonic measurements were made using a CUBA Research system utilizing a pair of 1 MHz unfocused transducers with mean precision CV = 0.7% and 6.0% for all SOS and BUA measurements, respectively. SOS and BUA were determined in 24 human cadaveric heels under three conditions: contact method (heel intact), water bath method (heel intact), water bath method (no soft tissue). Although there were significant differences between measurements using contact and water bath techniques (heel intact), their correlations were high (r = 0.858 for SOS and r = 0. 937 for BUA; P < 0.001). After removal of soft tissue, SOS significantly increased (78 m/second; P < 0.001) whereas there was no change in BUA (P > 0.05). Heel width correlated with SOS measurements (-0.224 < r < -0.347; P < 0.001) and bone width correlated with BUA measurements (0.198 < r < 0.276; P < 0.001). The practice of using a fixed heel dimension (Lunar Achilles) was investigated by comparing SOS calculated with measured heel thickness and a value of 4 cm (Lunar Achilles). SOS increased by 42 m/second (2.7%) using the fixed heel dimension compared with measured heel widths. This study demonstrates the similarity between contact and water bath-based methods, while showing that the presence of soft tissue reduces SOS but has no effect on BUA. The use of a fixed heel dimension for calculation of SOS overestimates values obtained when using measured heel dimensions, though the values correlate highly (r = 0.98, P < 0.001). In addition, an increase in heel width tends to cause an underestimation of SOS whereas an increase in bone width tends to overestimate BUA, although the effects are relatively small.

Discordant effect of body mass index on bone mineral density and speed of sound

“…Therefore, the meaning of varying Z-scores of BMD Z and SOS in the Lean group and to lesser degree in the Overweight group is uncertain. Our data of similar SOS in both the Overweight and Lean groups is in accordance with a previous study of excised bone [33] and a clinical [34], and is only slightly affected by BMI revealing a lack of correlation between BMI percentiles and SOS using the same QUS system.…”

“…Several qualitative ultrasound (QUS) studies reported that soft tissue slows the speed of sound (SOS) transmitted across bones, both clinical- [29-31], and in vivo situations [32,33]. On the contrary, SOS measured in vivo along bone is corrected for soft tissue thickness [34], and is only slightly affected by BMI [35].…”

Longitudinal assessment of bone loss using quantitative ultrasound in a blood‐induced arthritis rabbit model

“…Similar results were found in two in vitro studies [30,31] and one clinical study [32]. Results of this study showed that postmortem SOS measurements obtained without soft tissues were statistically significantly higher than in vivo SOS measurements with overlying soft tissues, suggesting that soft tissues can be confounding factors for SOS measurements in bone.…”

Comparison of Six Calcaneal Quantitative Ultrasound Devices: Precision and Hip Fracture Discrimination

“…2b) is mainly affected by the definition of transit time (first deviation from zero, first zero crossing) and velocity [8,45]. For example gelcoupled devices measure the heel thickness, and watercoupled devices use a fixed value [44,46]. However, these differences might not be clinically significant when the measurements are normalized and expressed as Tscores.…”