Three dimensional impedance map analysis of rabbit liver.

One challenge of quantitative ultrasound is the identification of the scattering sites in tissue. Three dimensional (3‐D) impedance maps (3DZMs) created from a series of histological tissue slide images are a useful tool to identify the scattering structures. 3DZMs are virtual (computational) data sets of real tissue that can be used to study fundamental ultrasonic properties. In this work fatty rabbit liver was chemically fixed and thinly sliced (3 μm) to create a series of H&E histology images. These images were realigned to one another using a registration scheme and pixels were assigned an impedance value to create a 3‐D map of acoustic impedance. Through a power spectral analysis of the reconstructed 3‐D volume, the effective scatterer diameter was estimated for the tissue using the fluid filled sphere form factor model. The results showed that when weighting the estimation toward smaller scatterer sizes, the effective scatterer diameter was 7.04 ± 1.30 μm. In the actual tissue this diameter corresponds closely to the size of the liver cell nucleus. These results provide encouragement that the reconstructed 3‐D volume is an accurate acoustic representation of the tissue, and suggest that the nucleus could be a primary source of scattering in fatty liver. [Work supported by NIH Grant No. CA111289.]