Official Proceedings - AIUM

American Institute of Ultrasound in Medicine Proceedings J Ultrasound Med 32(suppl):S1–S134, 2013also perform receiver operating characteristic (ROC) analysis of 38 regionsof interest (ROIs) from ex vivo bovine livers. Ultrasound imagingwas performed using a 9L4 transducer on a Siemens S2000 system priorto and following RF thermal ablation in 19 independent samples cut from4 bovine livers. Each ablation was approximately 1 to 2 cm in diameter.Results—In frequency domain Monte Carlo simulations, themultiple taper (MT) method was better able to estimate the MSS ofgamma-distributed scatterers than any single taper (ST) calculations. Inanalyzing 2 different ROI sizes ex vivo, we found that for a gate length of5 mm, we achieved an area under the ROC curve of 0.89, while at a gatelength of 7 mm, we achieved an area under the ROC curve of 0.93 usingMT coherence calculations.Conclusions—ROC analysis indicates that a tissue classifierusing coherence is able to distinguish between ablated and unablatedtissue and that an MT calculation of coherence is a better estimate than anST calculation. (Supported by National Institutes of Health grantsR01CA112192-05, R01CA112192-S103, and T32 CA09206-31).1540510 Acoustic Radiation Force Impulse Delineation of HumanCarotid Atherosclerotic Plaque Composition and StructureIn VivoTomasz Czernuszewicz, 1 Melissa Caughey, 2 Peter Ford, 3Mark Farber, 3 William Marston, 3 Raghuveer Vallabhaneni, 3Jonathon Homeister, 4 Matthew Mauro, 5 Timothy Nichols, 2,4Caterina Gallippi 1 *1 Joint Department of Biomedical Engineering,2 Medicine, 3 Surgery, 4 Pathology and Laboratory Medicine,5 Radiology, University of North Carolina, Chapel Hill,North Carolina USAObjectives—Conventional atherosclerosis imaging methodsrely on detecting luminal obstruction, which may not occur until late stagesof disease progression and does not reflect plaque rupture potential. Plaquedetection may be expedited and risk assessment improved by imagingmethods that describe the plaque composition and structure. We have previouslyso demonstrated acoustic radiation force impulse (ARFI) ultrasoundpreclinically with immunohistochemical validation. The objectiveof this work was to similarly validate ARFI in human atherosclerosis. Wehypothesize that ARFI delineates the fibrous cap, lipid/necrotic components,fibrous tissue, and calcium deposits in human atherosclerotic plaquein vivo.Methods—ARFI imaging was performed using a SiemensAcuson Antares imaging system with modifiable beam sequencing and aVF7-3 transducer in the carotid arteries of 2 patients undergoing clinicallyindicated carotid endarterectomy. Imaging was performed presurgicallyby focusing on the surgical plaque. After surgery, the extracted specimenwas sectioned according to noted arterial geometry for spatial registrationto the imaging plane. The sections were stained with hematoxylin-eosin,Verhoff van Gieson, Masson trichrome, and von Kossa. Parametric 2DARFI images of peak displacement (PD) were rendered.Results—In a fibroatheromatic plaque, 3 times higher ARFIPD was measured in the position of a soft lipid/necrotic region than in theposition of a thick fibrous cap above the region or fibrotic tissue below theregion. ARFI PD was nearly zero in positions of small (5 µm in the adjacent arterial tissue.Conclusions—These spatially matched ARFI and immunohistochemicaldata suggest that ARFI is relevant to describing the atheroscleroticplaque composition and structure in humans in vivo. The resultsalso demonstrate the feasibility of collecting data to perform a larger-scalestatistical reader study to evaluate human ARFI atherosclerosis imagingperformance using spatially matched immunohistochemistry as the validatingstandard.S101539520 Echocardiography-Based Measurements of 3-DimensionalMyocardial Fiber StructureMichelle Milne, 1 Kirk Wallace, 4 Benjamin Johnson, 1 GautamSingh, 2 Ravi Rasalingam, 3 James Miller, 1 Mark Holland 1,2 *1Physics, 2 Pediatrics, 3 Internal Medicine, Washington University,St Louis, Missouri USA; 4 GE Global Research, Niskayuna,New York USAObjectives—Previous studies from our laboratory demonstratedthat quantitative measurements of myocardial fiber structure for individualhearts can be derived from analyses of echocardiographic images.Echocardiography-based measurements of fiber structure at specific transverseplanes agreed well with those obtained using diffusion tensor magneticresonance imaging methods. The objective of this study was toextend the echocardiography-based measurements to produce 3D myocardialfiber structure images of the entire heart.Methods—A series of 2D apical echocardiographic imageswere acquired from each of 7 excised intact sheep hearts using a GE Vivid7 clinical imaging system. Myocardial fiber orientations corresponding tospecific distances from the apex of the heart were generated from analysesof radial line backscatter profiles within the ventricular walls of theheart in conjunction with a previously determined relationship betweenthe backscatter level and the angle of insonification relative to myocardialfiber orientation. The fiber orientations at each measured distancefrom the apex were assembled to produce a 3D fiber orientation image ofthe entire heart. In addition, 3D volumetric apical echocardiographic imageswere acquired from a subset of the excised hearts for comparison.Results—3D images depicting myocardial fiber structure obtainedfrom analyses of echocardiographic data appear consistent with theknown fiber structure of the heart. Images demonstrate left ventricularmid-myocardial fibers oriented within the short-axis plane and graduallybecoming more longitudinally oriented toward the epicardial and endocardialsurfaces. Data from 3D volumetric apical echocardiographic imagessuggest similar results.Conclusions—These results demonstrate that measurementsof 3D myocardial fiber structure of the entire heart can be successfullyderived from analyses of echocardiographic images. Further developmentof this method may provide a method for mapping the myocardial fiberorientation in individual patients over the heart cycle and provide a meansfor assessing potentially altered fiber structure associated with congenitaland acquired heart diseases. (Supported by National Institutes of Healthgrant R01 HL040302.)1541124 Effects of Preprocessing on Reconstructed Shear WaveSpeeds in Human Liver In VivoNed Rouze, 1 * Seung Yun Lee, 1 Michael Wang, 1Mark Palmeri, 1 Manal Abdelmalek, 2 Kathryn Nightingale 11Biomedical Engineering, Duke University, Durham, NorthCarolina USA; 2 Medicine, Division of Gastroenterology, DukeUniversity School of Medicine, Durham, North Carolina USAObjectives—Time-of-flight methods are often employed to providequantitative measurement of shear wave speed (SWS) from ultrasonicallytracked displacements following acoustic radiation forceexcitation in liver. These methods estimate overall group velocities ofpropagating shear waves and generally require filtering to reduce noiseand motion artifacts. In addition, different systems employ different beamgeometries in their push excitations, which also leads to differences in theshear wave frequency content. Differences in the shear wave frequencycontent can lead to differences in the estimated SWS due to the dispersivenature of hepatic tissue. In this study, we investigated the impact of theseeffects in a nonalcoholic steatohepatitis patient population from data obtainedin an Institutional Review Board–approved protocol.Methods—Data from >170 patients with a range of fibrosisstages were processed using multiple filtering algorithms. Three types ofmotion filters were applied, including a quadratic motion filter, a high-