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A multiparameter approach involving classification of breast masses in ultrasonic B-scan images is described and discussed.

Breast cancer diagnosis through ultrasound tissue characterization was studied using receiver operating characteristic (ROC) analysis of combinations of acoustic features, patient age, and radiological findings. A feature fusion method was devised that operates even if only partial diagnostic data are available. The ROC methodology uses ordinal dominance theory and bootstrap resampling to evaluate [A.sub.z] and confidence intervals in simple as well as paired data analyses. The combined diagnostic feature had an [A.sub.z] of 0.96 with a confidence interval of [0.93, 0.99] at a significance level of 0.05. The combined features show statistically significant improvement over prebiopsy radiological findings. These results indicate that ultrasound tissue characterization, in combination with patient record and clinical findings, may greatly reduce the need to perform biopsies of benign breast lesions. Index Terms--Bootstrap, breast ultrasonic imaging, ROC analysis, tissue characterization.

An ultrasound single-element transducer is modeled using the PSpice circuit simulation software. The PSpice modeling technique includes electrical and mechanical matching as well as the focusing lens and allows the formulation of a relation between the electrical driving source and the acoustic velocity on the transducer surface. This boundary condition leads to the calculation of the acoustic field by numerical methods. It was shown that experimental data obtained with two different transducers are consistent with previous results predicted by related models.

Higher-order statistics (HOS)-based estimated distortions were used to deconvolve ultrasound images of the breast. Imaging distortions were estimated based on second-order statistics (SOS) of radio frequency ultrasound data. Deconvolution using HOS-based distortion estimates resulted in much higher resolution gains compared to SOS-based distortion estimates.

We model tissue as a collection of point scatterers embedded in a uniform media, and show that the higher-order statistics (HOS) of the scatterer spacing distribution can be estimated from digitized radio frequency (RF) scan line segments and be used in obtaining tissue signatures. We assume that RF echoes are non-Gaussian, on the grounds of empirical/theoretical justifications presented in the literature. Based on our model for tissue microstructure, we develop schemes for the estimation of resolvable periodicity as well as correlations among nonperiodic scatterers. Using HOS of the scattered signal, we define as tissue 'color' a quantity that describes the scatterer spatial correlations, show how to evaluate it from the higher-order correlations of the digitized RF scan line segments, and investigate its potential as a tissue signature. The tools employed, i.e., HOS, were chosen as the most appropriate ones because they suppress Gaussian processes, such as the one arising from the diffused scatterers. HOS, unlike second-order statistics, also preserve the Fourier-phase of the signature, the color of the tissue response. Working on simulated and clinical data, we show that the proposed periodicity estimation technique is superior to the widely used power spectrum and cepstrum techniques in terms of the accuracy of estimations. We also show that even when there is no significant periodicity in data, we are still able to characterize tissues using signatures based on the higher-order cumulant structure of the scatterer spacing distribution.

Hypoxia increases the cerebral blood flow (CBF) and the level of extracellular potassium (K)+e in anesthetized rats, though the increase in K+e is not essential for the increase in CBF. Glibenclamide decreases both CBF and (K+)e. Ouabain increases (K+)e but has no effect on the hypoxia-induced increase in (K+)e. Glibenclamide-sensitive potassium channels are involved in the accumulation of (K+)e during hypoxia. There is no increase in CBF despite a large increase in (K+)e if the arterial blood pressure falls below a lower limit of autoregulation.

A higher-order spectra-based deconvolution method estimates lateral and axial distortion in radio frequency (RF) ultrasound images. A two-dimensional convolutional model, which can indirectly incorporate the attenuation of beam aberration effects and of the pulse-echo wavelet is used to describe image formation in the RF domain. Two hypothetical single-dimension blurring kernels represent distortions along the axial and lateral axes.

The synthesis of nitric oxide mainly controls the cerebral blood flow in hypercapnia and hypoxia. The cerebral blood flow is reduced by sulfonylureas in hypoxia and not in hypercapnia. The cerebral blood flow from eucapnia becomes double in both hypoxia and hypercapnia. Glibenclamide and l-NMMA can not produce further reductions in the hypoxic dilation. The nitric oxide blockers decrease the hypercapnic cerebral blood flow. The cerebral blood flow in eucapnia is increased by cromakalim.

Computer simulations with a one-dimensional discrete scattering model of the properties of an echo envelope show that in the presence of nonuniformities in scattering volume the ultrasonic backscattered signals display non-Rayleigh satistics. The K-distribution facilitates the modeling of the density function of the envelope while its parameters provide data on the nature of scattering region. A general non-Rayleigh model involving the K-distribution helps represent the dependence of the backscattered signal statistics on the uniformity of scattering volume.

Computer simulation and experimental results are used to study the statistical characteristics of speckle in medical ultrasound B-scan images. The nonuniform phase distribution of the speckle caused by the scatterer's nearly uniform spacing is verified. A demodulator frequency sweeping approach for predicting the mean scatterer spacing using only phase information is presented. However, it is still under study for implementation in tissue characterization and nondestructive testing.

Computer simulation and experimental results are used to analyze the statistical characteristics of speckle in medical ultrasound B-scan images. It is shown that nonuniform phase distribution results when the scatterers have a nearly uniform distribution. The nonuniform speckle phase under conditions of multiples of a half wavelength and odd multiples of a quarter wavelength of the demodulation frequency are given.

Objective: The Clock Drawing Test (CDT) is commonly used as a screening tool for the assessment of dementia. The association between the CDT in acute stroke and long-term functional and cognitive outcomes in this population is unknown. The present prospective study is the first to examine if CDT scores in the acute stage after stroke are related to long-term outcomes and to compare the predictive ability of two scoring systems in a large sample of stroke patients. Method: A total of 340 patients admitted to an acute stroke unit were included in the present study. Separate stepwise multiple linear regression analyses were performed with eight independent variables (demographic/pre-stroke variables – age, sex, premorbid functioning; stroke-related variables – stroke severity, localization; cognitive variables – Orientation Test, CDT [2 scoring systems]), and four dependent variables administered one year post-stroke (Barthel Index, modified Rankin Scale, Reintegration to Normal Living index, Global Deterioration Scale). Results: Although both CDT scoring methods were related to all long-term outcome measures, the more comprehensive scoring system was the only baseline variable that significantly explained the variance in outcome measures in all four multiple regression models. Conclusion: Performance on the CDT in acute stroke is related to long-term outcomes including patients' degree of independence in performing activities of daily living, the degree to which they achieved reintegration into daily occupations, and the degree of cognitive decline observed one-year post-stroke. Future studies are needed to clarify the nature of the relationship between different CDT scoring systems and post-stroke outcomes. [ABSTRACT FROM AUTHOR]