BackgroundIn addition to breast imaging, ultrasound offers the potential for characterizing and distinguishing between benign and malignant breast tissues due to their different microstructures and material properties. The aim of this study was to determine if high-frequency ultrasound (20-80 MHz) can provide pathology sensitive measurements for the ex vivo detection of cancer in margins during breast conservation surgery.MethodsUltrasonic tests were performed on resected margins and other tissues obtained from 17 patients, resulting in 34 specimens that were classified into 15 pathology categories. Pulse-echo and through-transmission measurements were acquired from a total of 57 sites on the specimens using two single-element 50-MHz transducers. Ultrasonic attenuation and sound speed were obtained from time-domain waveforms. The waveforms were further processed with fast Fourier transforms to provide ultrasonic spectra and cepstra. The ultrasonic measurements and pathology types were analyzed for correlations. The specimens were additionally re-classified into five pathology types to determine specificity and sensitivity values.ResultsThe density of peaks in the ultrasonic spectra, a measure of spectral structure, showed significantly higher values for carcinomas and precancerous pathologies such as atypical ductal hyperplasia than for normal tissue. The slopes of the cepstra for non-malignant pathologies displayed significantly greater values that differentiated them from the normal and malignant tissues. The attenuation coefficients were sensitive to fat necrosis, fibroadenoma, and invasive lobular carcinoma. Specificities and sensitivities for differentiating pathologies from normal tissue were 100% and 86% for lobular carcinomas, 100% and 74% for ductal carcinomas, 80% and 82% for benign pathologies, and 80% and 100% for fat necrosis and adenomas. Specificities and sensitivities were also determined for differentiating each pathology type from the other four using a multivariate analysis. The results yielded specificities and sensitivities of 85% and 86% for lobular carcinomas, 85% and 74% for ductal carcinomas, 100% and 61% for benign pathologies, 84% and 100% for fat necrosis and adenomas, and 98% and 80% for normal tissue.ConclusionsResults from high-frequency ultrasonic measurements of human breast tissue specimens indicate that characteristics in the ultrasonic attenuation, spectra, and cepstra can be used to differentiate between normal, benign, and malignant breast pathologies.

Real time measurements may assist surgeons in obtaining negative or cancer free margins during lumpectomy to eliminate invasive re-excision. Previous findings show that highfrequency ultrasound can differentiate between a range of breast pathologies in surgical specimens. Two parameters, peak density and second-order spectral slope, are sensitive to histopathology. Our objective was to determine the mechanism linking high-frequency ultrasound to histology. The hypothesis is that ultrasound sensitivity is a function of the microscopic heterogeneity (and thus histology) of the tissue. Ultrasonic results from breast specimens were used to construct a multivariate analysis of the parameters that permitted differentiation of normal, adipose, benign, and malignant breast pathologies.

Measurements of musical instruments in an anechoic chamber at Brigham Young University are yielding high-resolution directivity data and balloon plots that may be analyzed and visualized as functions of time or frequency. Historically, room acoustics calculations involving directivity of sound sources have relied on well-defined radiation characteristics including principal radiation axes, directivity factors, beamwidths, etc. In recent times, room simulation software packages have incorporated more comprehensive steady state directivity data for loudspeakers that vary as functions of proportional frequency bands. However, in contrast to loudspeakers, many musical instruments have directivity patterns that are not well defined and that may vary more erratically as functions of pitch or other musical characteristics. This presentation explores the measured directivity properties of a few musical instruments and discusses how they might be encapsulated and incorporated into predictive room acoustics calculations.

High-frequency (20-80 MHz) ultrasonic measurements have the potential to detect cancer and other pathologies within breast tissues in real time, and thus may assist surgeons in obtaining negative or cancer free margins during lumpectomy. To study this approach, ultrasonic tests were performed on 34 lumpectomy margins and other breast tissue specimens from 17 patients to provide pulse-echo and through-transmission waveforms. Time-domain waveform analysis yielded ultrasonic attenuation, while fast Fourier transforms of the waveforms produced first- and second-order ultrasonic spectra. A multivariate analysis of the parameters derived from these data permitted differentiation of normal, adipose, benign, and malignant breast pathologies. The results provide a strong correlation between tissue microstructure and ultrasonic parameters relative to the morphology and stiffness of microscopic features such as ductules, lobules, and fibrous structures. Ultrasonic testing of bovine heart, liver, and kidney tissues supports this correlation, showing that tissues having stiff fiber-like or filled-duct structures, such as myocardium or ductal carcinomas, display greater peak densities in the ultrasonic spectra than tissues with soft, open duct-like structures, such as kidney tissue or normal breast glands. The sensitivity of high-frequency ultrasound to histopathology may assist in eliminating invasive re-excision for lumpectomy patients. [Work supported by NIH R21CA131798.]

Obtaining negative (cancer-free) margins in breast conservation surgery (BCS) is essential for ensuring all of the cancer has been removed from the excision site. Several rapid, noninvasive cancer detection methods are therefore being investigated for the intraoperative evaluation of margin status. This study investigated high-frequency (HF) ultrasound (20–80 MHz) as an intraoperative margin evaluation technique during BCS. In a 17-patient pilot study at the Huntsman Cancer Institute, Salt Lake City, Utah, through-transmission and pulse-echo measurements were acquired from 53 positions on specimens including margins, tumors, lymph nodes, and fibroadenomas. Measurements were acquired with the use of two 50-MHz transducers, a HF square-wave pulser/receiver, a 500-MHz digital oscilloscope, and a notebook PC. Parameters calculated from the data included peak density (the number of peaks and valleys across the ultrasonic spectrum), attenuation, and the slope of the second Fourier transform. Statistical analysis of the data revealed that a multivariate analysis combining peak density and attenuation provided the highest accuracy and sensitivity for differentiating malignant from nonmalignant tissue. The multivariate analysis showed 81.1% accuracy, 76.9% sensitivity, and 85.2% specificity. The results demonstrate that HF ultrasound is competitive with 2D specimen mammography and radio-frequency spectroscopy for margin evaluations. [Funding provided by Utah Valley University.]