Nicole Cowan, Utah Valley University
Physical Sciences
Breast cancer is the second most prevalent cancer among women, affecting one out of eight women in their lifetime. The ability to differentiate between malignant and normal tissues during breast cancer surgery would enable the surgeon to remove all of the cancer from the affected region in the breast, thereby reducing the risk of recurrence and the need for subsequent surgeries. A pilot study conducted at the Huntsman Cancer Institute showed that high-frequency ultrasound (20-80 MHz), and in particular the ultrasonic parameter peak density, was sensitive to breast tissue pathology. The objective of this study was to determine the effect of tissue microstructure on peak density using phantoms that mimic the histology of breast tissue. Phantoms were created from a mixture of distilled water, Knox gelatin, and Metamucil fiber. In order to simulate breast tissue histology and terminal ductal lobular units, polyethylene microspheres were embedded into the phantoms in layers, totaling 4 layers per phantom. The volume percent of polyethylene microspheres was kept constant in each phantom while varying microsphere sizes (58-925 μm diameter). Pitch-catch and pulse-echo measurements were acquired using 50-MHz transducers (Olympus NDT, V358-SU, 50 MHz, 0.635-cm diameter active element), a HF pulsar-receiver (UTEX, UT340), and a 1-GHz digital oscilloscope (Agilent DSOX3104A). Glycerol (Genesis Scientific) was used as a coupling agent between the transducers and the phantoms. Spectra were derived from the data, giving peak density (the number of peaks and valleys in a specified spectral range) and attenuation values. In a previous study, histology- mimicking phantoms were fabricated where the weight percent of polyethylene microspheres was kept constant, but the microsphere diameter was varied. The former study showed a clear trend of higher peak density values for smaller diameters, but no trend for attenuation. In contrast, the phantoms from this study showed no trend in peak density, but a clear trend of higher attenuation values for larger microspheres. The results show that specific changes in tissue microstructure affect the parameters of peak density and attenuation differently. Changes in the number of scatterers and in their size, as in the previous study, affected peak density most significantly. In contrast, changes solely in the size of the scatterers, but not in their number, affected attenuation most significantly. These results are consistent with attenuation results for lobular carcinoma in the pilot study. These results show that peak density and attenuation are complementary parameters, and could be used together to characterize a variety of tissue pathologies