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Technical Brief

Flow Dynamics in the Aortic Arch and Its Effect on the Arterial Input Function in Cardiac Computed Tomography

[+] Author and Article Information
Parastou Eslami

Department of Radiology, Massachusetts General Hospital, Harvard University, Boston, MA 02114
peslami1@mgh.harvard.edu

Jung-Hee Seo

Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD 21218
jhseo@jhu.edu

Albert C. Lardo

Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21218
lardo21@gmail.com

Marcus Y Chen

National Heart, Lung and Blood Institute (NHLBI), National Institutes of Health, Bethesda, MD 20892
chenmy@nhlbi.nih.gov

Rajat Mittal

Department of Medicine, Division of Cardiology, Johns Hopkins University, Baltimore, MD 21287
mittalr@gmail.com

1Corresponding author.

ASME doi:10.1115/1.4043076 History: Received June 13, 2018; Revised February 08, 2019

Abstract

The arterial input function (AIF)-time-density curve (TDC) of contrast at the coronary ostia-plays a central role in contrast enhanced computed tomography angiography (CTA). This study employs computational modeling in a patient-specific aorta to investigate mixing and dispersion of contrast in the aortic arch (AA) and to compare the TDCs in the coronary ostium and the descending aorta. Here, we examine the validity of the use of TDC in the descending aorta as a surrogate for the AIF. Computational fluid dynamics was used to study hemodynamics and contrast dispersion in a CTA-based patient model of the aorta. Variations in TDC between the aortic root, through the AA and at the descending aorta and the effect of flow patterns on contrast dispersion was studied via post-processing of the results. Simulations showed complex unsteady patterns of contrast mixing and dispersion in the AA that are driven by the pulsatile flow. However, despite the relatively long intra-aortic distance between the coronary ostia and the descending aorta, the TDCs at these two locations were similar in terms of rise-time and up-slope, and the time lag between the two TDCs was 0.19 seconds. TDC in the descending aorta is an accurate analog of the AIF. Methods that use quantitative metrics such as rise-time and slope of the AIF to estimate coronary flowrate and myocardial ischemia can continue with the current practice of using the TDC at the descending aorta as a surrogate for the AIF.

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