Gabriele Krombach

Contrast enhanced and non-contrast enhanced MR angiography represent the two main methods for delineation of vessels. In contrast enhanced MRA, classically spatial resolution and temporal resolution have to be balanced against each other. View sharing and central read out of k-space have been introduced for subsecond acquisition of high resolution dynamics. This technique has a broad spectrum of clinical applications. In non-contrast MRA the classical approaches time-of-flight and phase contrast angiography suffered from long acquisition time and were prone to flow artifacts in regions with non-laminar flow. Application of balanced steady state free precession with flow sensitive dephasing allows for selective delineation of arteries with high signal intensity and high spatial resolution without flow related artefacts. This technique has already been demonstrated to be of high clinical impact in many vessel territories including the upper and lower extremities.  

Marc Kouwenhoven¹, Silke Hey¹, Christine Nabuurs¹, Alan Huang¹, Adri Duijndam¹, Elwin de Weerdt¹, Holger Eggers², Niels Blanken³, and Tim Leiner^3
1Philips, Best, Netherlands, ²Philips Research, Hamburg, Germany, ³Radiology Dept., University Medical Center, Utrecht, Netherlands

In this work, the feasibility is explored for subtractionless first-pass time-resolved contrast enhanced MRA of the lower legs on 1.5T using Dixon, viewsharing and parallel imaging with high acceleration factors. Results in seven consecutive patients are analyzed and compared with the conventional subtraction method.  It is demonstrated that with the subtractionless method, bulk motion artifacts are eliminated, and SNR is significantly increased.

Jeremy Collins¹, Eric Keller², Edouard Semaan³, Riad Salem², Maria Carr², Michael Markl², and James C Carr^2
1Radiology, Northwestern University, Chicago, IL, United States, ²Northwestern University, Chicago, IL, United States, ³Chicago, IL, United States

Assessment of the hepatic vasculature is critical as part of the pre-liver transplant evaluation. The prevalence of renal insufficiency and concerns regarding gadolinium administration in this cohort has created a need for a non-contrast alternative for vascular assessment. We evaluated the clinical performance of a non-contrast MRA (NCMRA) protocol at 3T in the assessment of the hepatic vasculature in patients with cirrhosis, with contrast-enhanced MRA (CEMRA) as the reference standard. The NCMRA protocol was diagnostic in 94% of subjects, identifying all relevant variant anatomy. Clinically available NCMRA techniques when combined into a comprehensive protocol enable assessment of the hepatic vasculature. 

Michael Hope^1
1UCSF

We will focus on the emerging applications of multidimensional MR flow imaging (4D Flow). The techniques and hemodynamic biomarkers that we will discuss can be applied broadly throughout the cardiovascular system. Two key issues must be addressed when considering these applications: 1) clear advantages over ultrasound/echocardiography and 2) matching advanced imaging capabilities with clinical questions that change the management of patients with cardiovascular disease. The goal is to provide a unique understanding of how abnormal flow promotes or exacerbates disease. This understanding, in turn, could allow patients to be risk-stratified based on flow, guide medical therapy, and identify new pathways to target with drug therapy and patients that may benefit from early intervention. The outline of the talk is 1) review of two current clinical applications for MRI flow imaging and 2) discussion of four emerging applications for 4D Flow. 

Alex J Barker¹, Pim van Ooij², Emilie Bollache¹, David Guzzardi³, S. Chris Malaisrie⁴, Patrick M McCarthy⁴, Jeremy D Collins¹, James Carr¹, Paul WM Fedak³, and Michael Markl^1,5
1Radiology, Northwestern Univeristy, Chicago, IL, United States, ²Academic Medical Center, Amsterdam, Netherlands, ³University of Calgary, Calgary, AB, Canada, ⁴Cardiac Surgery, Northwestern Univeristy, Chicago, IL, United States, ⁵Bioengineering, Northwestern University, Chicago, IL, United States

Bicuspid aortic valve (BAV) morphology will alter transvalvular blood flow patterns and vessel wall shear stress (WSS). These hemodynamic changes have been associated with the regional expression of BAV aortopathy. However, the presence of aortic stenosis can confound the regional expression of WSS. The purpose of this study was to use aortic WSS atlases to understand the role of aortic valve morphology and stenosis on the expression of WSS in the ascending aorta of a large control and BAV patient cohort (n=312).

Jacob Macdonald¹, Omid Forouzan², Naomi Chesler², Christopher Francois³, and Oliver Wieben^1,3
1Medical Physics, University of Wisconsin - Madison, Madison, WI, United States, ²Biomedical Engineering, University of Wisconsin - Madison, Madison, WI, United States, ³Radiology, University of Wisconsin - Madison, Madison, WI, United States

Cardiopulmonary exercise testing is gaining increased recognition as a useful tool for assessing pulmonary hypertension (PH). Using an MRI-compatible exercise device that allows subjects to exercise in the bore of the magnet, we investigated the effects of exercise stress on blood flow in the ascending aorta in healthy controls and patients with PH. The measurements we obtained demonstrated a decreased exercise capacity in PH subjects and in older controls. Some parameters, such as cardiac output, demonstrated statistically significant changes between rest and stress, while others were unclear due to the relatively low exercise power tolerated by the PH patients.