Prospects for ultrasonic spectroscopy and spectral imaging of abdominal tissues

Abstract

A system for the digitization and frequency spectral analysis of radiofrequency data for ultrasonic waveforms backscattered from abdominal tissues is de· scribed. Studies of phantoms meant to simulate abdominal tissues of differing scattering characteristics indicated that frequency spectral differences due to differences in the frequency dependence of backseat· tering were seen with 5 MHz probes, but not with a 3.5 MHz probe. Studies of a phantom with a simulated lesion of altered scattering characteristics indi· I t has been well established that scattering from tissue scattering centers is a function of fre· quency, with frequency dependence being a function of the size, shape and elastic properties of the individual scatterers.1 The radiofrequency (RF) echo spectrum of backscattered ultrasonic beam encodes information on the frequency dependence of tissue scatterers and has been studied extensively as a tool for noninvasive description of tissue scattering characteristics for a variety of human tissues in vivo?-6 Conventional gray scale ultrasonography employs broadband ultrasonic waveform data and Received April 20, 1992, spatially encodes the distribution of overall (nonfrequency-dependent) backscatter in tissues, but this method is not sensitive to differences in frequencydependent scattering. We have adapted a clinical ultrasound scanner to allow acquisition of the RF signal, in order to explore the possibility that frequency spectra of ultrasound beams backscattered from abdominal tissues might provide useful information on tissue scattering characteristics not present in conventional sonographic images. A variety of phantom studies with the adapted clinical scanner have been performed to help determine the paten· tial of this approach and develop optimal ways for acquiring and processing the ultrasonic spectral information. METHODSA custom data acquisition system was developed to perform both digitization of received ultrasonic signals and narrowband processing of real-time ultrasonic images. The system is designed to allow acqui-

Effects of Inherent Tissue Anisotropy on Measurements Obtained with a Clinical Ultrasonic Imaging System

“…Measurements of time-domain integrated backscatter [10,11] and the centroid frequency ofpower spectra [12][13][14][15][16][17][18][19] were performed on excised specimens of bovine tendon. This tissue type was chosen because the fibers are very weil aligned and one can readily vary the scattering and attenuation properties by changing the angle of insonification with respect to the predominant fiber orientation.…”

Tendinopathy Discrimination by Use of Spatial Frequency Parameters in Ultrasound B-Mode Images

“…Some of these functions include the co-occurrence matrix [23] and the spatial autocorrelation [22]. Methods using the frequency dependence of the backscatter power spectrum have also been applied [24], [25]. The autocorrelation function is related to the squared norm of the Fourier spectrum through the Wiener-Khinchin theorem, and thus methods using the Fourier transform have also been studied.…”

Liver Tumors: Utility of Characterization at Dual-Frequency US

“…In prior studies (13,14) in which narrow-band frequency filtration of ultrasound was used, it was possible to alter the contrast of lesions in their surroundings, owing to the same physical principles discussed earlier for the dualfrequency technique. There have also been a number of prior attempts (1,(3)(4)(5)(6)15) to exploit frequency-dependent backscattering effects to perform regional estimates of the sizes of scatterers in tissue and thus obtain information incremental to that of conventional US imaging.…”