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Biomedical subjects

E J Feleppa

Publications and source records attributed to E J Feleppa.

24 records · Page 2Linked to original sources
PubMed1988

Comparison of theoretical scattering results and ultrasonic data from clinical liver examinations.

A theoretical analysis of soft-tissue ultrasonic scattering has been used to formulate specific results describing spectral parameters for tissue characterization. Results are applicable to clinical liver examinations. Three spectral parameters are mathematically expressed in terms of acoustic attenuation and the effective sizes, concentrations, and relative acoustic impedances of tissue scatters. Results from a clinical data base are shown to agree well with analytical results for each spectral parameter. Agreement is found for: spectral shapes; effects of attenuation; and correlations between parameters. Images of three spectral parameters are presented and their gray-scale features are evaluated with reference to analytical results.

Humans↗
PubMed1985

Focal and diffuse liver disease studied by quantitative microstructural sonography.

Quantitative microstructural sonography differs from conventional sonography in several ways. The frequency as well as the amplitude of echoes is recorded and assessed using spectral analysis techniques. The effects of diffraction of the ultrasound beam are calibrated, as are the transfer characteristics of the system. Studies of patients with alcoholic liver disease revealed significantly increased attenuation, heterogeneity of scatterers, and local scattering strength in those with severe disease; in contrast, patients with mild cirrhosis exhibited decreased local scattering strength compared to normal individuals. Using retrospective three-parameter discriminant analysis, 23 out of 24 patients were successfully categorized, suggesting that the parameters used were capable of measuring microstructural changes associated with these disease states. Parameters varied widely among 6 types of hepatic tumors, suggesting that this method may offer promise in distinguishing tumors from normal cases and alcoholic liver disease as well as from each other. Further applications and evaluation of this method appear justified.

Adenoma, Bile Duct↗
PubMed1983

Theoretical framework for spectrum analysis in ultrasonic tissue characterization.

An analytic model is described for application in ultrasonic tissue characterization. The model is applicable to clinical broadband pulse echo systems. It treats spectra derived from received echo signals and relates them to physical tissue properties. The model can be applied to deterministic tissue structures (e.g., retinal detachments, larger blood vessels, and surface layers of the kidney) and to stochastic tissue structures (e.g., various tumors). The beam patterns included in the model are those generated by focused transducers typically used in high-resolution clinical ultrasound. Appropriate calibration procedures are also treated; these are needed for interpretation of absolute spectral parameters. The results obtained with the analytic model have been used to design a digital processing system and the associated techniques which are now being applied during examinations of the eye and abdominal organs. The results have proven useful in interpreting data from various types of tissues. To illustrate the application of these results, representative clinical data, obtained from the digital system, are presented for two types of tissue architectures. The first case is a detached retina representing a deterministic structure characterized by well-defined thickness and reflection coefficients. The second case is asteroid hyalosis and represents a stochastic entity in which the positions of small scattering particles are best described in statistical terms, and characterization is accompanied by means of normalized power spectra.

Eye Diseases↗