| A model based on the microstructure-accounting mechanical theory (doublet/nano mechanics) was developed, in combination with the use of a characterization-mode ultrasound method, for the reconstruction of otherwise inaccessible information on the physical properties of biological tissue samples. Changes in tissue physical properties are well recognized as associated with disease inception. Quantitative characterization on these properties, however, has been elusive. This study investigated a novel theoretical model, in comparison with that built upon conventional mechanical theories, to test the hypothesis that a discrete representation that takes into account the complex but intrinsic micro-architecture of biological tissue, could offer beneficial implications for separating normal tissue from the abnormal.; Surgical remnant, snap-frozen breast tissue from multiple subjects were obtained and prepared as very thin sections embedded between two pieces of glass. The samples were tested on a novel ultrasonic non-destructive evaluation system that records the mechanical responses of the inspected samples through their reflection coefficients within a broad range of frequencies. One broadband non-focal ultrasound transducer was employed to generate ultrasonic pulses that impinge from an oblique angle onto the tissue samples. Another transducer with same characteristics was used to acquire the reflections. Theoretical models that depict plane, elastic wave propagation in a three-layered medium were constructed to predict the reflection responses of the thin tissue layer. The quantitative information on the micro-level mechanical and structural properties was made available through an inverse algorithm that finds the optimal combination of the parameter values that allows for the best agreement between the model prediction and the experimental data. The results from the doublet and continuum mechanics models were compared.; The experimental data showed that the spectra from normal and malignant tissue were appreciably and consistently different. The statistic analysis on the quantitative reconstruction of tissue parameters presented significant difference on certain properties. The study has demonstrated that the adopted ultrasonic system was sensitive in detecting the differences in the mechanical responses from normal and malignant tissue. The microstructure-accounting mechanical model may provide an advantageous approach for quantitative analysis of tissue towards the goal of cancer detection and diagnosis. |
