Assessment of backscatter parameters by simulations and animal experiments

ABSTRACTS,

ULTRASONIC IMAGING AND TISSUE CHARACTERIZATION

SYMPOSIUM

Community Concerted Action Programme on Ultrasonic Tissue Characterization and Echographic Imaging (EUKECH). [l] Verhoef, W.A., Cloostermans, M.J.T.M. and Thijssen, J.M., IEEE Trans. Biomed. Enz. 32, 521-29 (1985). SESSION 2: SCATTERING & WAVE PROPAGATION QUANTITATIVE SCATTERER SIZE IMAGING, M.F. Insana, K.S. Hensley, S.J. Rosenthal and G.G. Cox, Department of Diagnostic Radiology, University of Kansas Medical Center, Kansas City, KS 66103. A method for estimating the size of acoustic scatterers has been incorporated into our quantitative imaging efforts. Using phantoms with well-defined scattering sources, we have shown that it is possible to increase the image contrast between two regions with different size scatterers at the expense of some spatial resolution. The tradeoffs among noise, contrast and spatial resolution for scatterer size images have been studied in the context of a signal-to-noise analysis to compare its performance with that of B-scan imaging. We have found that quantitative scatterer size images at 8x8 mm resolution produced excellent contrast between 39 and 105 pm spheres that was not apparent in the corresponding Bscan image. The noise in the quantitative image was 30 percent as defined by the fractional uncertainty in the pixel estimates. There was contrast enhancement even at 4x4 mm resolution, where the noise was 40 to 70 percent. We expect that scatterer size imaging will offer new quantitative information for studying soft tissue structure in vivo. For example, many pathological conditions of the liver, spleen and kidney are characterized by alterations in the microstructure of the organ. Present methods of ultrasonic image generation are sensitive to macroscopic alterations in organ structure or to gross infiltration. It may be possible, however, to improve ultrasound sensitivity to early, relatively microscopic alterations Preliminary data show that by detecting changes in scatterer size. scatterer size may be estimated at relatively high resolution for imaging applications, and that accurate estimates are possible in physiologically attenuating and weakly aberrating media. This project was supported in part by BRSG SO7 RR05373 awarded through the Division of Research Resources, National Institutes of Health. ASSESSMENT OF BACKSCATTER PARAMETERS BY SIMULATIONS AND ANlMAL EXPERIMENTS, Romijn and J.M. Thijssen, Department of Ophthalmology, St. R.L. Radboudhospital, University of Nijmegen, Nijmegen, The Netherlands. to backscattering by biological Various models have been applied tissues, e.g., discrete scattering and scattering described by continuous acoustic impedance. The spectral autocorrelation functions of the characteristics of the scattering and the scatterer size can be estimated. Simulations were performed to assess accuracy limits for the estimation of these parameters under various assumptions regarding the tissue model (scatterer statistics). The animal model served as a test for the b m applicability of the model employed for data acquisition, (pre)processing and analysis. The special histology of the intraocularly-implanted Greene's hamster melanoma enabled a critical test that was passed quite well. Cancer This work is supported by a grant from the Netherlands' Fo-undation - Queen Wilhelmina Fund and was carried out within the framework of the European Community Concerted Action Programme on Ultrasonic Tissue Characterization and Echographic Imaging (EURECH). ACCURATE BROADBAND DETERElINATION OF ACOUSTIC BACKSGATTER COEFFICIENTS SHORT DURATION PULSES AND TIME GATES, Timothy Hall, Ernest Madsen,

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