Ziheng Zhang¹, Donald P. Dione², Ben A. Lin², Albert J. Sinusas², and Smita Sampath^1
1Department of Diagnositc Radiology, Yale University, School of Medicine, New Haven, CT, United States, ²Section of Cardiovascular Medicine, Yale University, School of Medicine, New Haven, CT, United States

Early diastolic filling is tightly coupled to regional myocardial relaxation patterns. Here, we track the 2D pseudo pathlines of blood emitter particles that are dynamically released from the mitral valve plane during early diastole. Results in normal volunteers demonstrate a distinct pattern of filling that corresponds closely with myocardial relaxation patterns. Further, results in an infarcted animal demonstrate significant abnormality, underlining the sensitivity of this method as an indicator of diastolic filling abnormalities.

Michael Markl¹, Julia Geiger¹, Lena Herzer², Brigitte Stiller², and Raoul Arnold^2
1Radiology, Medical Physics, University Medical Center, Freiburg, Germany, ²Pediatric Cardiology, University Medical Center, Freiburg, Germany

The aim of this study was to apply flow-sensitive 4D MRI for the comprehensive characterizations of flow pattern changes in clinically unsuspicious Marfan patients (without aortic disease) and to evaluate the effect of aortic geometry on hemodynamic alterations. Results were compared to findings in healthy volunteers and patients with suspected Marfan syndrome. Helix and vortex flow was clearly enhanced in the descending aorta of Marfan patients and was associated with significantly increased valve and aortic diameters. Flow-sensitive 4D MRI may help to identify Marfan patients at risk for cardiovascular complications and to assign appropriate therapies prior to these complications.

Pablo Bächler¹, Natalia Pinochet¹, Gérard Crelier², Cristián Tejos^3,4, Pablo Irarrazaval^3,4, and Sergio Uribe^4,5
1School of Medicine, Pontificia Universidad Católica, Santiago, Chile, ²Institute for Biomedical Engineering, University and ETH, Zurich, Switzerland, ³Electrical Engineering Department, Pontificia Universidad Católica, Chile, ⁴Biomedical Imaging Center, Pontificia Universidad Católica, Chile, ⁵Radiology Department, Pontificia Universidad Católica, Chile

4D Flow has been used to study blood flow patterns, mainly in the aorta. We performed a flow pattern analysis in the Pulmonary Artery (PA). 4D Flow depicted complex flow patterns in the PA, revealing two vortices in the main PA and one in the right PA in healthy subjects. Abnormal blood flow patterns were seen in patients with different Congenital Heart Diseases (CHD), revealing complex hemodynamics in the pulmonary circuit. Knowledge of abnormal flow patterns in the PA in patients with CHD has the potential to contribute to improve current surgical interventions in this group of patients.

Octavia Biris^1,2, Sanjiv Shah^3,4, Jeremy Collins¹, Amir Davarpanah¹, James Carr^1,3, and Timothy J Carroll^1,2
1Radiology, Northwestern University, Chicago, IL, United States, ²Biomedical Engineering, Northwestern University, Evanston, IL, United States, ³Feinberg School of Medicine, Northwestern University, Chicago, IL, United States, ⁴Cardiology, Northwestern University, Chicago, IL, United States

Pulmonary arterial hypertension, a disease of proliferation of the pulmonary arteries, is currently diagnosed by right heart catheterization. We propose to develop a non-invasive alternative to catheterization, by which pulmonary artery pressure is calculated according to the Windkessel model by direct convolution of the pulmonary artery flow wave with an exponential function of time and vessel parameters compliance and vascular resistance. While flow in the pulmonary artery branches can be measured directly by MRI, compliance must be estimated from measurements of flow and vessel cross-section throughout the cardiac cycle. Pulmonary vascular resistance is estimated from measures of right ventricular function.

Alejandro Roldán-Alzate¹, Alex Frydrychowicz¹, Eric J Niespodzany¹, Benjamin R Landgraf¹, Oliver Wieben^1,2, and Scott B Reeder^1,2
1Radiology, University of Wisconsin, Madison, WI, United States, ²Medical Physics, University of Wisconsin, Madison, WI, United States

Accurate quantification of hepatic blood flow would facilitate improved understanding of the hemodynamic mechanisms by which portal hypertension affects the function of the liver. In this retrospective analysis, data acquired with an efficient 4D phase velocity imaging method was analyzed to assess flow to the hepatic vasculature. Data from 17 participants, 10 with portal hypertension and 7 controls were evaluated. Compared to healthy controls, patients with portal hypertension demonstrated increased blood flow through the portal vein.

Alex Frydrychowicz¹, Michael Markl², Eric Niespodzany¹, Christian Schlensak³, Mark Schiebler¹, and Christopher J François^1
1Department of Radiology, University of Wisconsin - Madison, Madison, WI, United States, ²Department of Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany, ³Department of Cardiac Surgery, University Hospital Freiburg, Freiburg, Germany

The aim of this study was to evaluate the hemodynamics in patients with chronic aortic dissection using 4D velocity mapping. A large variety of altered flow patterns was observed associated with different extents of disease, vessel dilatation, and post therapeutic anatomy. In contrast to well-described normal aortic flow patterns, a multitude of additional vortices and helices was observed in these patients, indicating a high degree of potentially abnormal, disorganized flow. Changes in secondary flow patterns were also present, such as enhanced retrograde flow. This study demonstrates the feasibility of using 4D velocity mapping for the hemodynamic evaluation of chronic aortic dissection.

Aurelien F Stalder^1,2, Alex Frydrychowicz³, Max F Russe², Jan G Korvink^4,5, Jürgen Hennig², Kun Cheng Li¹, and Michael Markl^2
1Dept. of Radiology, Xuanwu Hospital of Capital Medical University, Beijing, China, People's Republic of, ²Dept. of Radiology - Medical Physics, University Hospital Freiburg, Germany, ³Dept. of Radiology, University of Wisconsin, Madisson, United States, ⁴Dept. of Microsystems Engineering, University of Freiburg, Germany, ⁵Freiburg Institute for Advanced Studies (FRIAS), Freiburg, Germany

Turbulence and velocity fluctuations of the blood flow are believed to play a role in hemolysis, platelet activation and thrombus formation. Based on flow-sensitive MRI, Reynolds, Womersley & Strouhal numbers were measured in-vivo at 8 planes along the thoracic aorta in 30 healthy volunteers. The onset of turbulence (supra-critical Reynolds numbers) was evaluated based on a previous model describing the transition to turbulence for pulsatile flow. Onset of turbulence was most prominent in the ascending aorta and distal descending aorta. The results were shown to be statistically correlated with sex, body weight, aortic diameter and cardiac output.

Daniel Kim¹, Hadrien A Dyvorne¹, Ricardo Otazo¹, Daniel K Sodickson¹, and Vivian S Lee^1
1Radiology, Center for Biomedical Imaging, New York University School of Medicine, New York, New York, United States

Phase-contrast (PC) MRI is a promising modality for studying hemodynamics associated with pathophysiology, such as liver vascular flows in cirrhosis. A major disadvantage of PC MRI, however, is its low data acquisition efficiency, which may limit the achievable spatial and temporal resolutions within a clinically acceptable breath-hold duration. This study describes a method to accelerate PC MRI using compressed sensing and parallel imaging to jointly exploit image sparsity and coil sensitivity encoding. Seven healthy volunteers were imaged in hepatic and portal veins to validate accelerated PC MRI against PC MRI with GRAPPA. The resulting flow measurements were in good agreement.

Daniel Giese^1,2, Tobias Schaeffter¹, and Sebastian Kozerke^1,2
1Division of Imaging Sciences and Biomedical Engineering, King's College London, London, United Kingdom, ²Institute for Biomedical Engineering, Univeristy and ETH Zurich, Zurich, Switzerland

Pulse wave velocity assessment using cine phase-contrast measurements suffers from long scan times due to the required high temporal resolution. We propose the acquisition of highly undersampled phase-contrast data in combination with compartment k-t PCA to enable acquisition of two flow encoded slices through ascending and descending aorta with a temporal resolution of under 10ms in a single breathhold. It is shown that the calculated pulse wave velocities compare well with literature values and show strong correlation with velocities measured using conventional fully sampled data acquisitions.

Andrew D. Gilliam¹, Xiaodong Zhong², Kenneth C Bilchick³, and Frederick H Epstein^4
1Andrew D. Gilliam Consulting, Providence, RI, United States, ²MR R&D Collaborations, Siemens Healthcare, Atlanta, GA, United States, ³Cardiology, University of Virginia, Charlottesville, VA, United States, ⁴Radiology & Biomedical Engineering, University of Virginia, Charlottesville, VA, United States

Displacement encoding with stimulated echoes (DENSE) directly encodes tissue displacement into MR images, providing easy access to vital physiological information such as cardiac strain. Unfortunately, the quantification of displacement and strain from raw cine DENSE imagery currently relies on the manual delineation of cardiac anatomy. In this study, we present the first fully automated solution to estimate cardiac strain from 2D cine DENSE images. Results indicate good agreement between the innovative automated analysis algorithm and previously described methods.