Caracterização da resposta acústica por vibro-acustografia em fêmures de camundongos em um modelo experimental ex-vivo

Abstract

Introduction: This study aimed to evaluate the potential of vibro-acustography (VA) technique to detect bone alterations associated with osteoporosis, using an animal model. Methods: The experimental protocol included three groups of mice: a) control group, b) group with osteoporosis and c) group with osteoporosis and treated with pamidronate, an antiresorptive drug. The evaluation of bone by the VA technique was conducted in an acoustic tank. A confocal ultrasonic transducer generated two high frequency (MHz) focused beams, with a difference frequency of 65 KHz between them. These two beams interact with each other and with the bone sample, producing a low frequency acoustic response registered by a hydrophone. The VA spectral curves were processed with the fast Fourier transform, in order to obtain numerical values that are weighted in the mechanical properties of the samples. VA acquisition was repeated three times. We used microCT as the reference technique and estimated the correlation of VA and microCT parameters. Statistical analysis included Interclass Correlation Coefficient (ICC), ANOVA multiple comparisons and Spearman's rank correlation coefficient. Results: VA spectral analysis and area under the curve values (mean; st. desv.) were, respectively, 1.29e-07 and 9.32e-08 for the control group, 3.25e-08 and 2.16e-08 for the group with osteoporosis; and 1.50e-07 and 8.37e-08 for the group with osteoporosis treated with pamidronate. VA differentiate the experimental groups (p<0.01) and the results were reproducible (ICC = 0.43 [95%CI = 0.15-0.71]). There was a statistically significant relationship between VA and MicroCT in connectivity (p<0.01; r=0.80) and connectivity density (p<0.01; r=0.76) and a trend between VA and trabecular number (Tb.N) and trabecular s Tb.Sp (p=0.06). Conclusion: VA differentiated the bones from the control group and the osteoporotic group. In addition, we found a strong positive correlation between VA and bone connectivity measured by microCT.