B-mode images of spontaneous rat mammary tumors enhanced by estimated scatterer parameters

B-mode images of tissues enhanced by information about the microstructure can aid in the diagnosis of diseased (cancerous) tissues. Four retired breeder rats were acquired that had developed spontaneous mammary tumors. Tumors were diagnosed microscopically as mammary gland fibroadenomas. Two-dimensional B-mode images of the tumors in the rats were constructed from backscattered echoes using a 8 MHz (90% bandwidth) single element transducer. From the B-mode images, regions-of-interest (ROIs) were selected in the tumors and surrounding tissues. The power spectra of backscattered echoes gated from the ROIs were used to estimate the average scatterer diameter and scatterer concentration. The ROIs are boxes with sides of 10 wavelengths at the central frequency of the signal. The tissue microstructure is related to the average scatterer diameter and concentration. A unique estimation scheme is used to obtain the average scatterer diameter and the scatterer concentration. The average scatterer diameter is related to the slope of the best-fit line to the reduced measured power spectrum versus the frequency squared. The scatterer concentration is determined from the intercept of the best-fit line. The reduced measured power spectrum is the measured power spectrum minus 40 log of the frequency. Enhanced B-mode images are constructed by converting ROI boxes into colored pixels. The color of the pixels is related to the estimated scatterer parameters. For each tumor three images are constructed: the normal B-mode image, the B-mode image with superimposed scatterer diameter pixels, and the B-mode image with superimposed scatterer concentration pixels. The images show a distinct difference between the tumor and surrounding healthy tissues