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Biomedical subjects

L J Thomas

Publications and source records attributed to L J Thomas.

63 records · Page 4Linked to original sources
PubMedDate not supplied

Detection of remote myocardial infarction with quantitative real-time ultrasonic characterization.

We have previously shown that the intrinsic properties of myocardium can be characterized quantitatively by the assessment of ultrasonic integrated backscatter. In this study we utilized a novel, real-time, two-dimensional system capable of quantitative integrated backscatter imaging to determine whether zones of remote myocardial infarction in dogs could be delineated definitively by ultrasonic tissue characterization. Detection of such zones in patients is needed as a basis for management decisions related to thrombolysis, angioplasty, and coronary surgery. Integrated backscatter was measured through the closed chest from 25 myocardial sites. Zones of infarction exhibited time-averaged integrated backscatter values approximately 10 dB (9.5 +/- 0.5 dB, standard error of the mean) greater than those in normal regions (p less than 0.001). In addition, the physiologic cardiac cycle--dependent variation of integrated backscatter was blunted significantly in zones of infarction [0.8 dB +/- 0.3 vs. 3.8 +/- 0.6 (p less than 0.01) for normal regions]. Ultrasonic results matched the histopathologic features assessed directly. Thus quantitative ultrasonic tissue characterization can differentiate infarcted tissue from normal myocardium and offers promise for quantitative detection of histopathology in vivo.

Animals↗
PubMedDate not supplied

A detection algorithm for multiform premature ventricular contractions.

This paper reports an algorithm developed to identify and quantify multiform PVCs. The algorithm clusters PVCs of similar morphology using a combination of time-domain and frequency-domain analysis. Initially, PVCs are grouped together on the basis of four time-domain-based morphological feature measurements. However, these time-domain-based clusters many times are nonunique because commonly encountered signal changes can cause substantial variations in the feature measurements of clinically similar beats. These redundant clusters are consolidated using two frequency-domain parameters: The First Spectral Moment (FSM) (center of gravity) of the amplitude spectrum, and the 5-Hz phase angle.

Cardiac Complexes, Premature↗