Erik J. Offerman¹, Christopher B. Glielmi², Michael Markl³, Ioannis Koktzoglou^1,4, and Robert R. Edelman^1,3
1Radiology, NorthShore University HealthSystem, Evanston, IL, United States, ²Siemens Healthcare, Chicago, IL, United States, ³Radiology, Feinberg School of Medicine, Northwestern Univeresity, Chicago, IL, United States, ⁴Radiology, Pritzker School of Medicine, University of Chicago, Chicago, IL, United States

Flow-encode only (FEO) is a new time-resolved phase contrast (PC) method that benefits from a doubled time resolution over the traditional PC method, and does not require background phase correction. FEO quantifies blood-flow velocity by performing only flow-encoded acquisitions. FEO was compared to the traditional PC method in ten volunteers and two patients with peripheral artery disease. Flow measurements were compared between methods with flow profiles, linear correlation, and Bland-Altman analysis. Net flow, peak flow, reverse flow, and average flow metrics were compared as well. Blood-flow measurements showed no statistically significant difference between methods (paired t-test, p > 0.05).

Christoph Benk¹, Alexander Mauch¹, Friedhelm Beyersdorf¹, Rolf Klemm¹, Jan G. Korvink², Michael Markl³, and Bernd A. Jung^4
1Dept. of Cardiovascular Surgery, University Medical Center, Freiburg, Germany, ²IMTEK – Department of Microsystems Engineering, Laboratory for Simulation, Albert-Ludwigs University, Freiburg, Germany, ³Dept. of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States, ⁴Dept. of Radiology, Medical Physics, University Medical Center, Freiburg, Germany

Left ventricular assist devices (LVAD) has become an important treatment option for heart failure patients. However, altered blood flow patterns are suspected to affect perfusion in the aorta or cause structural changes leading to valve dysfunction or thrombus formation. An MR-compatible model system was developed consisting of an aorta connected to a LVAD simulating the pulsatile flow of the native heart. An LVAD was connected to the aorta model using different cannula positions and flow patterns were evaluated in predefined positions. The results indicate that the cannula position strongly influence flow patterns and flow rates in the aorta.

Yunpeng Zou^1,2, Matthew J. Middione^3,4, Subashini Srinivasan³, and Daniel B. Ennis^1,5
1Department of Bioengineering, University of California, Los Angeles, CA, United States, ²Sino-Dutch Biomedical and Information Engineering School, Northeastern University, Shenyang, China, ³Department of Radiological Sciences, University of California, Los Angeles, CA, United States, ⁴Biomedical Physics Interdepartmental Program, University of California, Los Angeles, CA, United States, ⁵Department of Radiological Sciences, University of California Los Angeles, Los Angeles, CA, United States

PC-MRI experiments are typically performed using spoiled gradient recalled echo (GRE) experiments in which incremental RF phase cycling and a dephasing gradient are used to eliminate any residual transverse magnetization prior to the application of the subsequent RF pulse. The effect of gradient spoiling on artifact suppression in GRE magnitude images has been studied in detail, but an analysis of gradient spoiling in phase contrast MRI (PC-MRI) phase images has not been described. The objective was to define time-optimal gradient spoiling for GRE-based PC-MRI to reduce the TR and improve temporal resolution.

David A. Saloner¹, Evan Kao², Gabriel Acevedo-Bolton², Andrew Lee², Petter Dyverfeldt², and Vitaliy L. Rayz^2
1Radiology and Biomedical Imaging, VA/UCSF, San Francisco, CA, United States, ²Radiology and Biomedical Imaging, UCSF, San Francisco, CA, United States

MR methods can be used to assess changes in aneurysm morphology over time. In addition vascular geometry and inlet flow conditions that are needed for Computational Fluid Dynamics can be determined using MRA and MR velocimetry. These methods were used in the evaluation of 78 aneurysms that were followed over time. CFD predictions indicate that there is an increased rate of growth in aneurysms where a large fraction of the aneurysm surface is exposed to low wall shear stress.

Gabriel Acevedo-Bolton¹, Andrew Lee¹, Vitaliy L. Rayz¹, Alastair Martin¹, and David A. Saloner^2
1Radiology and Biomedical Imaging, UCSF, San Francisco, CA, United States, ²Radiology and Biomedical Imaging, VAMC/UCSF, San Francisco, CA, United States

MR velocimetry reproducibility was mesured in a cohort of 88 subjects with untreated aneurysms that were evaluated repeatedly over periods of time as long as 7 years. Reproducibility was also measured in exact replicas of the complex geometries of a subset of these subjects. Good agreement was found between experimental and computational flow measurements. In vivo studies were found to be reproducible with an error of measurement of 10%.

Merlin Fair¹, Peter David Gatehouse¹, Peter Drivas¹, and David N. Firmin^1
1Royal Brompton Hospital, London, UK, United Kingdom

A modified phase-contrast method gave increased SNR for static tissue for baseline velocity offset correction, using one extra breath-hold after each flow study. In 18 flow studies, this improved accuracy in offset corrections using higher order fits, but gave no significant improvement over the standard linear correction of background offsets.

Ning Jin¹, Juliana Serafim da Silveira², and Orlando P. Simonetti^2,3
1Siemens Healthcare, Columbus, Ohio, United States, ²Department of Radiology, Ohio State University, Columbus, Ohio, United States, ³Department of Internal Medicine, Ohio State University, Columbus, Ohio, United States

Velocity measurement based on ECG-triggered, segmented phase-contrast imaging (PC-MRI) is a valuable and accurate technique to assess hemodynamics in a variety of clinical applications. However, this method requires reliable cardiac gating, regular cardiac rhythm, and some means to suppress respiratory motion artifacts. Real-time PC-MRI (RT-PCMRI) overcomes these limitations and can measure hemodynamic variations across cardiac cycles. While the accuracy and utility of through-plane RT-PCMRI has been previously demonstrated, in this study we describe a technique for real-time measurement of in-plane velocities and demonstrate the equivalence of real-time in-plane peak velocity measurements with results obtained using conventional, ECG-triggered, segmented k-space PC-MRI.

Arun Antony Joseph¹, Jan Sohns², Johannes Kowallick², Klaus-Dietmar Merboldt¹, Joachim Lotz², and Jens Frahm^1
1Biomedizinische NMR Forschungs GmbH am Max-Planck-Institut für biophysikalische Chemie, Göttingen, Niedersachsen, Germany, ²University Medical Center Georg-August-University, Göttingen, Niedersachsen, Germany

Real-time PC imaging with highly undersampled FLASH and regularized nonlinear inversion reconstruction was used for imaging Valsalva maneuver. High temporal resolution of 40 ms per phase contrast map aid in visualizing and analyzing the dynamic changes to flow parameters during the Valsalva maneuver. Variations of flow parameters in ascending aorta for through plane flow at preparation, maneuver and rest phases were analyzed.

Eric Mathew Schrauben¹, Ashley Anderson², Kevin M. Johnson¹, and Oliver Wieben^1,3
1Medical Physics, University of Wisconsin - Madison, Madison, Wisconsin, United States, ²Medical Physics, University of Wisconsin - Madison, Madison, WI, United States,³Radiology, University of Wisconsin - Madison, Madison, WI, United States

Many strategies are employed to compensate for respiratory motion in PC MR exams, yet its effects on blood flow are often neglected. This study demonstrates the feasibility of a 4D radially-undersampled respiratory resolved acquisition and reconstruction for the characterization of respiratory induced blood flow changes in the great vessels.

Frank Ong¹, Martin Uecker¹, Umar Tariq², Albert Hsiao², Marcus T. Alley², Shreyas S. Vasanawala², and Michael Lustig^1
1University of California, Berkeley, Berkeley, CA, United States, ²Stanford University, Palo Alto, CA, United States

A novel noise reduction processing for 4D flow MRI data using divergence-free wavelet transform is presented. Divergence-free wavelets have the advantage of enforcing soft divergence-free conditions when discretization and partial voluming result in numerical non-divergence-free components and at the same time, provide sparse representation of flow in a generally divergence-free field. Efficient denoising is achieved by appropriate shrinkage of divergence-free and non-divergence-free wavelet coefficients. To verify its performance, the proposed processing was applied on in vivo data sets and was demonstrated to improve visualization of flow data without distorting quantifications.

Zhiyue J. Wang^1,2, Jonathan M. Chia³, David M. Higgins⁴, Youngseob Seo^2,5, and Nancy K. Rollins^1,2
1Childrens Medical Center, Dallas, Texas, United States, ²Univeristy of Texas Southwestern, Dallas, Texas, United States, ³Philips Healthcare, Cleveland, OH, United States, ⁴Philips Healthcare, Guildford, Surrey, United Kingdom, ⁵Division of Convergence Technology, Korea Research Institute of Standards and Science, Daejeon, Korea

This work looks at the feasibility of performing sparse sampling in high resolution phase contrast imaging using a unique subtraction reconstruction algorithm. Images were sparsely sampled at 45, 36, and 30% and compared against a fully sampled image through region of interest analysis. Under sampled data showed slight underestimation of quantitative values while still maintaining an accurate flow curve behavior. Physiologic fluctuations and the intrinsic nature of under sampling, most likely, lead to this discrepancy. Sparse sampling techniques have been shown to be very promising in achieving accurate quantitative data while reducing scan times significantly.

Mo Kadbi¹, M.J. Negahdar¹, Melanie S. Traughber², Peter Martin², and Amir A. Amini^1
1Elect. and Comp. Eng., University of Louisville, Louisville, KY, United States, ²Philips healthcare, Cleveland, OH, United States

A 4-D flow MRI has been investigated to quantify carotid artery hemodynamics and to visualize the temoral motion of fluid particles in detail . In addition to comprehensive anatomical and flow information in both in-plane and through-plane directions, 4D flow imaging results in shorter total scan time compared to 3-D flow imaging Conventional 4D PC-MRI based on the Cartesian trajectory results in a very long scan. Herein, a 4D spiral PC MRI technique was designed to reduce the scan time compared to conventional technique. 4D spiral PC MRI has the added advantage of reducing the phase error and signal loss due to long TE.

Sebastian Schmitter¹, Bharathi D. Jagadeesan², Andrew W. Grande³, Julien Sein¹, Kamil Ugurbil¹, and Pierre-Francois Van de Moortele^1
1Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States, ²Departments of Radiology and Neurosurgery, University of Minnesota, Minneapolis, MN, United States, ³Departments of Radiology, Neurosurgery and Neurology, University of Minnesota, Minneapolis, MN, United States

Trigeminal Neuralgia is characterized by episodic severe facial pain possibly from “pulsatile” compression of the nerve Root Entry Zone of the Trigeminal Nerve (REZ) by the adjacent superior cerebellar artery (SCA). The exact role of pulsatility of SCA loops in the etiology of TN remains unknown since similar anatomical proximity of SCA and REZ can be found in normal individuals and there are no methods to measure the pulsatility of the SCA currently available. Herein we report the feasibility of measuring the Pulsatility Index (PI) of the SCA using 4D MRA in a normal volunteer at 7 Tesla.

Jelena Bock¹, Julia Geiger¹, Raoul Arnold², Daniel Hirtler¹, Hans Burkhardt¹, and Michael Markl^3
1University of Freiburg, Freiburg, Germany, ²University of Heidelberg, Heidelberg, Germany, ³Northwestern University, Chicago, IL, United States

Pressure gradients are an important clinical marker for the severity of cardiovascular disease such as aortic valve stenosis or aortic coarctation. It was the aim of this study to evaluate the potential of an optimized data analysis strategy based on 4D flow MRI for the assessment of aortic 3D pressure difference maps compared to the gold standard invasive catheter measurements in patients with aortic coarctation. Differences between MRI, echocardiography and catheter measurements demonstrate the potential of MRI to non-invasively determine pressure gradients in aortic coarctation and indicate the importance of dynamic aortic boundary conditions for accurate pressure difference estimation.

Edouard Michel Semaan¹, Michael Markl¹, Bradley D. Allen¹, Alex Baker¹, Chris Malaisrie², Patrick McCarthy³, James C. Carr⁴, and Jeremy D. Collins^4
1Radiology Department, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States, ²Surgery Department, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States, ³Surgery-Cardiac Surgery Department, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States,⁴Radiology Department, Northwestern University, Chicago, Illinois, United States

This study evaluates the impact of aortic root repair on aortic hemodynamic flow in subjects with bicuspid and tricuspid aortic valve morphology without stenosis or significant insufficiency using 4D flow MRI. Aortic root repair results in a more homogeneous flow profile, reduced helical flow patterns, and resolution of forward flow jets impacting the aortic wall compared to control subjects matched with pre-surgical thoracic aortic aneurysm size, age, and aortic valve morphology. These changes occur at the expense of increased peak systolic velocities and regurgitation; the long-term impact of these changes on vascular physiology is unknown.

Nicolas Charalambous¹, Kristis Michaelides¹, Elias Psimolofitis², Vasilis Tzangarakis³, Demos Michaelides³, Stelios Angeli⁴, and Christakis Constantinides^4
1Hydrus Ltd, Limassol, Cyprus, ²CNE Limited, Nicosia, Cyprus, ³α-Evresis Diagnostic Center, Nicosia, Cyprus, ⁴U. of Cyprus, Nicosia, Cyprus

Myocardial tissue characterization, pre- and post-implantation or following therapy, has becoming an elusive and active research area in clinical practice and basic science work. Prior efforts have focused on the invasive [Stuyvers 1997] and non-invasive MRI characterization of the left ventricular (LV) muscle elasticity [Kolinpaka 2010] to document energetic status, rates and extent of filling and relaxation [Aletras 1999, Wen 2005]. Diastolic filling, in particular, is regarded as the dynamic outcome of myocardial re-lengthening post-contraction and ventricular flow. The pressure fields developed within the intra-ventricular cavity are the determinants of wall stress and the transmural strain gradients. The temporal evolution of such gradients is ultimately dependent on tissue viscoelasticity and its mechanical material properties. Transmural stress and strain, are therefore, direct manifestations of structure-function, the muscle’s material properties, and the active and passive fiber force generation, as a result of sarcomeric contraction-relaxation, intra-cavity blood pressure changes, and their effects on the endocardial wall [Hu 2003]. This work develops a comprehensive noninvasive imaging protocol for computational modeling, and estimation of global cardiac stress and strain fields of an elastomeric heart of a dynamically controlled cardiac phantom using ex-vivo testing, functional MRI and computational fluid dynamics (CFD). The elicited results are validated based on the computational solutions of the Navier-Stokes (NS) equations for the elastomer and flow velocity fields, in comparison with bench experimentation and phase contrast (PC) MRI.

Kelly Jarvis¹, Susanne Schnell¹, Ramona Lorenz², Alejandro Roldán-Alzate³, Kevin M. Johnson³, Maya Gabbour⁴, Joshua D. Robinson^4,5, Cynthia K. Rigsby^1,4, and Michael Markl^1
1Radiology, Northwestern University Feinberg School of Medicine, Chicago, IL, United States, ²Radiology, University Medical Center Freiburg, Freiburg, Germany, ³Radiology and Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States, ⁴Medical Imaging and Cardiology, Ann & Robert H. Lurie Children’s Hospital of Chicago, Chicago, IL, United States, ⁵Pediatrics, Northwestern University Feinberg School of Medicine, Chicago, IL, United States

Single ventricle patients have a complex form of congenital heart disease and undergo multiple surgeries, resulting in the Fontan vasculature geometry. There is growing evidence that underlying hemodynamics in the Fontan circulation may play an important role in patient outcome. The aim of this study was to isolate flow at the Fontan connection by integrating anatomical image segmentation into the 4D flow MR analysis work flow for improved flow visualization and mixing quantification.

Zoran Stankovic^1,2, Jury Fink¹, Maximilian Russe¹, Michael Markl², and Bernd A. Jung^3
1Dept. of Radioloy, University Medical Center, Freiburg, Germany, ²Dept. of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States,³Dept. of Radiology, Medical Physics, University Medical Center, Freiburg, Germany

The purpose of this study was to evaluate the utility of k-t parallel imaging for the acceleration of 4D flow MRI in the portal system by systematically investigating the impact of different acceleration factors R on quantification of hemodynamics parameters such as peak velocities, flow rates or wall shear stress. K-t-GRAPPA accelerated 4D flow MRI with a temporal resolution of 82 ms was performed in 16 healthy volunteers with R=3, 5 and 8 and compared to conventional GRAPPA with R=2. Additionally, a k-t accelerated scan with R=5 with a temporal resolution of 41 ms was performed.

Jesús Urbina^1,2, Julio Sotelo^2,3, Marcelo Andía^2,4, Cristián Tejos^2,3, Daniel Hurtado², Pablo Irarrázabal^2,3, and Sergio Uribe^2,4
1Medical School, Pontificia Universidad Católica de Chile, Santiago, Santiago, Chile, ²Biomedical Imaging Center, Pontificia Universidad Católica de Chile, Macul, Santiago, Chile,³Electrical Engineering Department, Pontificia Universidad Católica de Chile, Macul, Santiago, Chile, ⁴Radiology Department, Pontificia Universidad Católica de Chile, Santiago, Santiago, Chile

In this work we propose to use 4D Flow sequence to obtain and compare pressure maps in Ao and PA of healthy volunteer and patients with rTOF. rTOF patients had relative pressure differences between maximum and minimum values higher than volunteer in PA (P<0,05). Additionally, relative pressure of the Ao shown in this work had excellent correlation with other published values using 4D Flow and catheterization. The differences of maximum and minimum relative pressures in TOFr patients could be a novel parameter that can be used to study right ventricular function.

Mehmet Akçakaya¹, Praveen Gulaka², Tamer A. Basha¹, Warren J. Manning¹, and Reza Nezafat^1
1Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States, ²Samsung Electronics Co., Suwon, Korea

Phase contrast (PC) cardiac MR (CMR) is widely used to assess blood flow in cardiovascular disease. Clinically, 2D acquisitions are used for measurements of blood flow. Recently 3D PC CMR has been proposed to characterize all three directional components of blood flow. However, these require long, navigator-gated free-breathing scans, which limits its clinical usage, where accuracy and reproducibility of the flow measurements is important. In this study, we hypothesized that respiratory-gating the central k-space only will yield similar measurements to a fully respiratory-gated acquisition, and evaluated these two gating approaches in terms of quantification of cardiac indices and imaging efficiency.

Tetsuro Sekine¹, Yasuo Amano¹, Ryo Takagi¹, Yasuo Murai², Yuriko Suzuki³, and Shinichiro Kumita^1
1Radiology, Nippon Medical School, Tokyo, Japan, ²Neurosurgery, Nippon Medical School, Tokyo, Japan, ³Philips Electronics Japan, Tokyo, Japan

4D Flow assessment was examined in 19 patients after extracranial-intracranial bypass. Analysis: 1, Blood flow volume (BFV). 2, Direction of blood flow. 3, Pressure gradient at the M1. The flow direction correlates with the type of bypass. The pressure gradient at M1 correlates with the BFV difference between BFV of contralateral ICA plus BA and BFV of bypass.

Mark L. Schiebler¹, Phillip Kilgas¹, Elizabeth Janus Nett², Oliver Wieben², Shardha Srinivasen³, Petros Anagnostopoulos⁴, Scott K. Nagle^1,5, Scott B. Reeder^1,6, and Christopher J. François^7
1Radiology, UW-Madison, Madison, Wisconsin, United States, ²Medical Physics, UW-Madison, Madison, Wisconsin, United States, ³Pediatric Cardiology, UW-Madison, Madison, Wisconsin, United States, ⁴Cardiothoracic Surgery, UW-Madison, Madison, Wisconsin, United States, ⁵Medical Physics, UW-Madison, Madison, WI, United States, ⁶Biomedical Engineering, UW-Madison, Madison, WI, United States, ⁷Radiology, University of Wisconsin-Madison, Madison, Wisconsin, United States

Determination of the shunt fraction (Qp/Qs) in patients with partial anomalous pulmonary venous return is needed prior to surgical repair. We found no significant difference between the gold standard 2D PC measurements of Qp/Qs and those derived from 4D flow MRA for 5 patients and 10 normal volunteers. These cases have complex extra cardiac venous connections and atrial septal defects that are more amenable to quantify off line using post processing techniques than they are on the scanner trying to proscribe multiple double oblique 2D PC acquisitions.

Kathryn M. Broadhouse^1,2, Anthony N. Price^1,2, Giuliana Durighel¹, Anna E. Finnemore^1,2, David J. Cox^1,2, A. David Edwards^1,2, Joseph V. Hajnal^1,2, and Alan M. Groves^1,2
1Imaging Sciences Department, MRC Clinical Sciences Centre, Imperial College, London, United Kingdom, ²The Centre for the Developing Brain, Imaging Sciences & Biomedical Engineering Division, King's College, London, United Kingdom

A significant increase in pulse wave velocity (PWV) has been found in paediatric subjects born prematurely at low birth weight when studied at ~8yrs and may explain the increase in cardiac disease in this population. However PWV data does not extend back to preterm infants. The aim of this study was to assess the feasibility of measuring aortic PWV in preterm and term infants using 4D PC MRI, in order to establish a normative range in this population and facilitate comparison with adult values. PWV velocity in neonates was found to be at the lower end of reported adult ranges.

Yanqiu Feng¹, Kenneth Gilmour², Taigang He², Peter Drivas², Isabelle Roussin², Raad Mohiaddin², and David N. Firmin^2
1Southern Medical University, Guangzhou, Guangzhou, China, ²Royal Brompton Hospital, London, UK, United Kingdom

Phase-contrast peak velocity measurement through cardiac valves has important clinical applications, but is widely known to underestimate peak velocity. This abstract evaluated whether Fourier Velocity Imaging (FVI) in aortic stenoses avoids the underestimation by standard phase-contrast cine imaging (PC), and compares FVI with Doppler echocardiography (US).