Scott L. Roth

Echocardiographically guided electrophysiologic testing in pregnancy.

Electrophysiologic testing is usually performed with fluoroscopy to guide catheter positioning. This method of visualizing catheter placement may not be ideal for patients who are pregnant. We report four cases of echocardiographically guided placement of catheters for electrophysiologic testing because of the consideration of pregnancy. Adequate visualization of catheters was possible, allowing for proper catheter positioning and complete electrophysiologic testing, including the recording of atrial, His-bundle, and ventricular potentials, as well as cardiac stimulation and induction of tachycardia. This method holds promise for patients in whom fluoroscopy may be relatively contraindicated, such as pregnant patients, as well as patients in whom it is desirable to avoid x-ray exposure such as women of childbearing age and young children.

Spectral Analysis of Demodulated Ultrasound Returns: Detection of Scatterer Periodicity and Application to Tissue Classification

Ultrasound returns from tissue display variations in amplitude on several spatial scales. Although large-scale variations result from factors such as attenuation, variations on smaller scales are caused by tissue characteristics such as variations in scatterer spacing and reflectance. These small scale variations cause a corresponding variation in the amplitude of the ultrasound return. A simple and direct method for detecting and quantifying periodicity in these variations in the presence of attenuation is described. The radiofrequency ultrasound return is first demodulated by full-wave rectification. The normalized power spectrum of the demodulated return then yields an index that we call the relative Fourier energy. Both computer simulations and in vitro experiments were performed in order to study how relative Fourier energy performed in discriminating between periodic and random scatterer distributions. Computer simulations demonstrated significant differences between the returns from periodic and random scatterer distributions. Ultrasound returns from aortic tissue yielded a relative Fourier energy index that was significantly different between normal vs. atherosclerotic tissue (normal: 0.868 ± 0.076, mean ± s.d., fibrofatty plaque: 0.705 ±0.109, p< 0.01 vs. normal, calcified plaque: 0.753 ± 0.078, p < 0.01 vs. normal). In contrast, no difference was found in comparisons of overall reflectance. SUMMARY

Early and rapid prediction of patency of the infarct-related coronary artery by using left ventricular wall thickness as measured by two-dimensional echocardiography.

OBJECTIVES The aim of this study was to determine whether echocardiography can distinguish between persistent coronary occlusion and reperfusion. BACKGROUND There are no adequate clinical or noninvasive laboratory markers to accurately predict successful reperfusion in an acute myocardial infarction. METHODS In a closed chest swine model, the effect of reperfusion on myocardial wall thickness was studied by comparing a 150-min total coronary artery occlusion (group 1) with 120 min of occlusion followed by 30 min of reperfusion (group 2) in the area of risk as measured by echocardiography. Wall thickness was measured at baseline and at 90 and 150 min. RESULTS In group 1 (n = 4), there was no appreciable change in mean wall thickness from 90 min to 150 min of occlusion at either end-diastole or end-systole (0.54 +/- 0.02 to 0.52 +/- 0.03 cm, 0.55 +/- 0.03 to 0.54 +/- 0.03 cm, respectively; p = NS). In contrast, in group 2 (n = 6), an increase in mean wall thickness from 0.53 +/- 0.02 to 0.97 +/- 0.05 cm at end-diastole and from 0.56 +/- 0.04 to 1.04 +/- 0.07 cm at end-systole was found from 90 min of occlusion to 30 min of reperfusion (p < 0.001). Reperfusion resulted in an increase in wall thickness of 83 +/- 11% at end-diastole and 92 +/- 17% at end-systole. In contrast, persistent coronary occlusion showed minimal changes of -3.0 +/- 5% at end-diastole and -2.0 +/- 6% at end-systole. CONCLUSIONS This study confirms the hypothesis that an increase in wall thickness can accurately distinguish between reperfusion and permanent coronary occlusion.

Signal processing for ultrasound imaging

The visibility of features in ultrasound images that include at least two types of tissue can be improved by processing the images using a variety of algorithms. In one such algorithm, the ratio of power in a first spatial frequency band to power in a second spatial frequency band is computed for a plurality of samples of a received ultrasound return signal that are associated with a given pixel. In another such algorithm, the ratio of power in a first spatial frequency band to total power is computed. With both algorithms, the computed ratio is then mapped to a gain for the given pixel, the raw intensity of the given pixel is modified in accordance with the gain, and the pixel is displayed with the modified intensity.