Publications

Daniel Bruce Ennis
Daniel Bruce Ennis
Professor of Radiology (Veterans Affairs)
dbe@stanford.edu

Bio

Daniel Ennis {he/him} is a Professor in the Department of Radiology. As an MRI scientist for nearly twenty years, he has worked to develop advanced translational cardiovascular MRI methods for quantitatively assessing structure, function, flow, and remodeling in both adult and pediatric populations. He began his research career as a Ph.D. student in the Department of Biomedical Engineering at Johns Hopkins University during which time he formed an active collaboration with investigators in the Laboratory of Cardiac Energetics at the National Heart, Lung, and Blood Institute (NIH/NHLBI). Thereafter, he joined the Departments of Radiological Sciences and Cardiothoracic Surgery at Stanford University as a postdoc and began to establish an independent research program with an NIH K99/R00 award focused on “Myocardial Structure, Function, and Remodeling in Mitral Regurgitation.” For ten years he led a group of clinicians and scientists at UCLA working to develop and evaluate advanced cardiovascular MRI exams as PI of several NIH funded studies. In 2018 he returned to the Department of Radiology at Stanford University as faculty in the Radiological Sciences Lab to bolster programs in cardiovascular MRI. He is also the Director of Radiology Research for the Veterans Administration Palo Alto Health Care System where he oversees a growing radiology research program.

Publications

  • Assessing the Impact of Cardiac Output and Valve Orientation on Bioprosthetic Pulmonary Valve Hemodynamics Using In Vitro 4D-Flow MRI and High-Speed Imaging. Cardiovascular engineering and technology Schiavone, N. K., Nair, P. J., Elkins, C. J., McElhinney, D. B., Ennis, D. B., Eaton, J. K., Marsden, A. L. 2024

    Abstract

    Pulmonary valve replacement (PVR) using bioprosthetic valves is a common procedure performed in patients with repaired Tetralogy of Fallot and other conditions, but these valves frequently become dysfunctional within 15 years of implantation. The causes for early valve failure are not clearly understood. The purpose of this study was to explore the impact of changing cardiac output (CO) and valve orientation on local hemodynamics and valve performance.A 25 mm bioprosthetic valve was implanted in an idealized 3D-printed model of the right ventricular outflow tract (RVOT). The local hemodynamics at three COs and two valve orientations were assessed using 4D-Flow MRI and high-speed camera imaging.Noticeable differences in jet asymmetry, the amount of recirculation, leaflet opening patterns, as well as the size and location of reversed flow regions were observed with varying CO. Rotation of the valve resulted in drastic differences in reversed flow regions, but not forward flow.Flow features observed in the valve with low CO in this study have previously been correlated with calcification, hemolysis, and leaflet fatigue, indicating their potential negative impact on local hemodynamics and leaflet performance.

    View details for DOI 10.1007/s13239-024-00762-x

    View details for PubMedID 39633206

    View details for PubMedCentralID 5516054

  • MRI-Based Circumferential Strain in Boys with Early Duchenne Muscular Dystrophy Cardiomyopathy. Diagnostics (Basel, Switzerland) Liu, Z. Q., Maforo, N. G., Magrath, P., Prosper, A., Renella, P., Halnon, N., Wu, H. H., Ennis, D. B. 2024; 14 (23)

    Abstract

    Background: In boys with Duchenne muscular dystrophy (DMD), cardiomyopathy has become the primary cause of death. Although both positive late gadolinium enhancement (LGE) and reduced left ventricular ejection fraction (LVEF) are late findings in a DMD cohort, LV end-systolic circumferential strain at middle wall (Ecc) serves as a biomarker for detecting early impairment in cardiac function associated with DMD. However, Ecc derived from cine Displacement Encoding with Stimulated Echoes (DENSE) has not been quantified in boys with DMD. We aim to: (1) use cine DENSE to quantify regional Ecc in LGE negative (-) boys with DMD and healthy controls; and (2) compare Ecc with LVEF in terms of differentiating DMD boys with LGE (-) from healthy boys. Methods: 10 LGE (-) boys with DMD and 12 healthy boys were enrolled prospectively in an IRB-approved study for CMR at 3T. Navigator-gated cine DENSE was used to obtain short-axis mid-ventricular data and estimate global and regional Ecc. Group-wise differences were tested via a Wilcoxon rank-sum test. Within-group differences were tested via a Skillings-Mack test followed by pairwise Wilcoxon signed-rank tests. A binomial logistic regression model was adopted to differentiate between DMD boys with LGE (-) and healthy boys. Results: When compared to healthy boys, LGE (-) boys with DMD demonstrated significantly impaired septal Ecc [-0.13 (0.01) vs. -0.16 (0.03), p = 0.019]. In comparison to the Ecc in other segments, both groups of boys exhibited significantly reduced septal Ecc and significantly elevated lateral Ecc. Septal Ecc outperformed LVEF in distinguishing DMD boys with LGE (-) from healthy boys. Conclusions: Reduced septal Ecc may serve as an early indicator of cardiac involvement in LGE (-) DMD boys prior to reduced LVEF and a positive LGE finding.

    View details for DOI 10.3390/diagnostics14232673

    View details for PubMedID 39682580

  • Phase contrast MRI with minimized background phase errors. Magnetic resonance in medicine Loecher, M., Ennis, D. B. 2024

    Abstract

    Phase contrast MRI (PC-MRI) is used clinically to measure velocities in the body, but systematic background phase errors caused by magnetic field imperfections corrupt the velocity measurements with offsets that limit clinical utility. This work aims to minimize systematic background phase errors in PC-MRI, thereby maximizing the accuracy of velocity measurements.The MRI scanner's background phase errors from eddy currents and mechanical oscillations were modeled using the gradient impulse response function (GIRF). Gradient waveforms were then numerically optimized using the GIRF to create pulse sequences that minimize the background phase errors. The pulse sequences were tested in a static phantom where the predicted response could be compared directly to the measured background velocity. The optimized acquisitions were then tested in human subjects, where flow rates and background errors were compared to conventional PC-MRI.When using the GIRF-optimized gradient waveforms, the predicted background phase was within 0.6 [95% CI = -3.4, 5.4] mm/s of the measured background phase in a static phantom. Excellent agreement was seen for in vivo blood flow values (flow rate agreement r 2

  • Diffusion Tensor MRI of the Heart: Now Feasible on Your Neighborhood Scanner. Journal of cardiovascular magnetic resonance : official journal of the Society for Cardiovascular Magnetic Resonance Sosnovik, D. E., Ennis, D. B. 2024: 101101

    View details for DOI 10.1016/j.jocmr.2024.101101

    View details for PubMedID 39326559

  • Design and implementation of a cost-effective, open-source, and programmable pulsatile flow system HARDWAREX Herwald, S. E., Sze, D. Y., Ennis, D. B., Vezeridis, A. M. 2024; 19

    View details for DOI 10.1016/j.ohx.2024.e00561

    View details for Web of Science ID 001280912400001

Daniel B. Ennis, PhD

Professor Department of Radiology

Director of Radiology Research VA Palo Alto Healthcare System