Browsing by Author "Miller, James G."

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    Conventional, Bayesian, and Modified Prony's methods for characterizing fast and slow waves in equine cancellous bone
    (AIP Publishing, 2015-08) Groopman, Amber M.; Katz, Jonathan I.; Fujita, Fuminori; Matsukawa, Mami; Mizuno, Katsunori; Wear, Keith A.; Miller, James G.; Department of Radiology and Imaging Sciences, IU School of Medicine
    Conventional, Bayesian, and the modified least-squares Prony's plus curve-fitting (MLSP + CF) methods were applied to data acquired using 1 MHz center frequency, broadband transducers on a single equine cancellous bone specimen that was systematically shortened from 11.8 mm down to 0.5 mm for a total of 24 sample thicknesses. Due to overlapping fast and slow waves, conventional analysis methods were restricted to data from sample thicknesses ranging from 11.8 mm to 6.0 mm. In contrast, Bayesian and MLSP + CF methods successfully separated fast and slow waves and provided reliable estimates of the ultrasonic properties of fast and slow waves for sample thicknesses ranging from 11.8 mm down to 3.5 mm. Comparisons of the three methods were carried out for phase velocity at the center frequency and the slope of the attenuation coefficient for the fast and slow waves. Good agreement among the three methods was also observed for average signal loss at the center frequency. The Bayesian and MLSP + CF approaches were able to separate the fast and slow waves and provide good estimates of the fast and slow wave properties even when the two wave modes overlapped in both time and frequency domains making conventional analysis methods unreliable.
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    Patients with Diabetes and Significant Epicardial Coronary Artery Disease have Increased Systolic Left Ventricular Apical Rotation and Rotation Rate at Rest
    (Wiley, 2016-04) Rasalingam, Ravi; Holland, Mark R.; Cooper, Daniel H.; Novak, Eric; Rich, Michael W.; Miller, James G.; Pérez, Julio E.; Department of Radiology and Imaging Sciences, IU School of Medicine
    Objective The purpose of this study was to determine whether resting myocardial deformation and rotation may be altered in diabetic patients with significant epicardial coronary artery disease (CAD) with normal left ventricular ejection fraction. Design A prospective observational study. Setting Diagnosis of epicardial CAD in patients with diabetes. Patients and Methods Eighty-four patients with diabetes suspected of epicardial CAD scheduled for cardiac catheterization had a resting echocardiogram performed prior to their procedure. Echocardiographic measurements were compared between patients with and without significant epicardial CAD as determined by cardiac catheterization. Main Outcome Measures Measurement of longitudinal strain, strain rate, apical rotation, and rotation rate, using speckle tracking echocardiography. Results Eighty-four patients were studied, 39 (46.4%) of whom had significant epicardial CAD. Global peak systolic apical rotation was significantly increased (14.9 ± 5.1 vs. 11.0 ± 4.8 degrees, P < 0.001) in patients with epicardial CAD along with faster peak systolic apical rotation rate (90.4 ± 29 vs. 68.1 ± 22.2 degrees/sec, P < 0.001). These findings were further confirmed through multivariate logistic regression analysis (global peak systolic apical rotation OR = 1.17, P = 0.004 and peak systolic apical rotation rate OR = 1.05, P < 0.001). Conclusions Patients with diabetes with significant epicardial CAD and normal LVEF exhibit an increase in peak systolic apical counterclockwise rotation and rotation rate detected by echocardiography, suggesting that significant epicardial CAD and its associated myocardial effects in patients with diabetes may be detected noninvasively at rest.
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    Toward three-dimensional echocardiographic determination of regional myofiber structure
    (Elsevier, 2016-02) Milne, Michelle L.; Singh, Gautam K.; Miller, James G.; Wallace, Kirk D.; Holland, Mark R.; Department of Radiology and Imaging Sciences, IU School of Medicine
    As a step toward the goal of relating changes in underlying myocardial structure to observed altered cardiac function in the hearts of individual patients, this study addresses the feasibility of creating echocardiography-derived maps of regional myocardial fiber structure for entire, intact, excised sheep hearts. Backscatter data were obtained from apical echocardiographic images acquired with a clinical ultrasonic imaging system and used to determine local fiber orientations in each of seven hearts. Systematic acquisition across the entire heart volume provided information sufficient to give a complete map for each heart. Results from the echocardiography-derived fiber maps compare favorably with corresponding results derived from diffusion tensor magnetic resonance imaging. The results of this study provide evidence of the feasibility of using echocardiographic methods to generate individualized whole heart fiber maps for patients.