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Jelena Bock¹, Alex Frydrychowicz¹, Thorsten A. Bley¹, Aurelien F. Stalder¹, Max F. Russe¹, Manuela Keckeis¹, Juergen Hennig¹, Michael Markl¹

¹University Hospital Freiburg, Freiburg, Germany

Flow sensitive 4D MRI permits the measurements of three directional blood flow velocities. These data can be used to derive additional information on vascular geometry by phase contrast (PC) angiography. Detailed evaluation of PC angiography image quality in the thoracic aorta compared to the reference standard CE-MRA was performed in a study in 3 groups (without contrast agent, with extravascular and with blood pool contrast agent) on a collective of 31 volunteers. Quantitative and qualitative evaluation of image quality demonstrated that PC-MRA can provide reliable angiography of the thoracic aorta of good quality compared to CE-MRA.

Maggie M. Fung¹, Ehud J. Schmidt², Maureen N. Hood³, Godtfred Holmvang⁴, Raymond Y. Kwong⁵, Vincent B. Ho³

¹GE Healthcare, Bethesda, Maryland, USA; ²GE Healthcare, Boston, Massachusetts, USA; ³National Naval Medical Center, Bethesda, Maryland, USA; ⁴Massachusetts General Hospital, Boston, Massachusetts, USA; ⁵Brigham and Women’s Hospital, Boston, Massachusetts, USA

A novel multiple-temporal-phase ECG-gated 3D contrast enhanced MRA approach with automatic triggering is presented. The efficient use of cardiac cycle for imaging, and a variable-center slice ordering scheme, enable the acquisition of high resolution, motion suppressed, temporally-selective contrast-enhanced images in a parallel manner, thus allowing completion within a single breathhold. This increases the robustness of ceMRA and streamlines workflow in the clinical setting. The flexible temporal selectivity enables visualization of arterial and venous phase with short temporal separation. This technique can also be used to evaluate morphological changes of the vasculatures in different cardiac phases.

Clifton R. Haider¹, Nobert G. Campeau¹, James F. Glockner¹, John Huston¹, Stephen J. Riederer¹

¹Mayo Clinic, Rochester, Minnesota, USA

The purpose of this work is to describe how 2D SENSE with 2D homodyne processing can be applied to peripheral MRA to provide an order of magnitude (>10X) reduction of acquisition time.  It is hypothesized that a 2D SENSE-accelerated CArtesian Projection Reconstruction-Like acquisition can provide a time series of diagnostic quality, 1 mm3 isotropic spatial resolution images of the lower legs with 5 sec update times and 20 sec image acquisition times. Results demonstrate high temporal fidelity, high spatial resolution, and the robust nature of the highly accelerated CE-MRA sequence which can readily distinguish arterial from and venous phase.

Gilwoo Choi¹, Nathan M. Wilson¹, Christopher P. Cheng¹, Robert J. Herfkens¹, Charles Anthony Taylor¹

¹Stanford University, Stanford, California , USA

The interaction between the musculoskeletal system and the vasculature in the lower extremities plays a major role in determining superficial femoral artery (SFA) deformation. We used magnetic resonance imaging to investigate whether the location of the SFA with respect to the femur contributes to the observed shortening of the SFA with hip and knee flexion. Volume coregistration between two different image acquisitions was performed using the femur geometry as a reference. We found that the proximal part of the SFA moved more inferiorly than the distal segment, which contributed to shortening of the SFA.

Xiaoming Zhang¹, Honglei Zhang², Hsien Wang³, Yi Wang², Martin R. Prince²

¹Shandong University Qilu Hospital, Jinan, People's Republic of China; ²Weill Medical College of Cornell University, New York, New York, USA; ³Columbia College, New York, New York, USA

To compare the utility of 3D time resolved MRA and 3D bolus chase MRA for evaluating infra-popliteal arteries, data from 113 patients were reviewed retrospectively.  The image quality was determined.   Among all of the factors(age, gender, weight, ulcer/gangrene/cellulitis, diabetes, hypertension, CHF and arterial phase duration), only U/G/C and arterial phase duration had statistically significant partial effects indicating TRICKS provides more information in calves with fast flow due to ulceration, gangrene or cellulitis.  In patients with slower flow and longer arterial phase with late venous enhancement, TRICKS is unnecessary and may be eliminated to reduce the total Gd dose.

Yan Wu¹, Kevin Johnson¹, Oliver Wieben¹, Julia velikina¹, Andres Carrillo², Steven Kecskemeti¹, Charles A. Mistretta¹, Frank R. Korosec¹

¹University of Wisconsin-Madison, Madison, Wisconsin, USA; ²GE Healthcare, Evanston, Illinois, USA

HYPR is a reconstruction algorithm that enables rapid frame update rates while providing high SNR and temporal accuracy. In this study, three time-resolved imaging methods were compared, the stack-of-stars acquisition with HYPR reconstruction, the VIPR acquisition with HYPR reconstruction, and 3D Cartesian TRICKs method. The three methods were used to acquire contrast-enhanced MR angiograms of the peripheral vessels in healthy human volunteers. It has been demonstrated that both HYPR methods provide better spatial and temporal resolution than TRICKs; in comparing the HYPR methods, VIPR permits higher undersampling factors (better spatial or temporal resolution), whereas HYPR stack-of-stars is more geometrically suited.

Jeffrey Harold Maki¹, ², Silke Potthast², David J. Glickerman¹, Cecil E. Hayes², Maisie E. Wang², Gregory J. Wilson³

¹Puget Sound VAHCS, Seattle, Washington, USA; ²University of Washington, Seattle, Washington, USA; ³Philips Medical, Cleveland, Ohio, USA

Through the a-priori knowledge of individual patient bolus kinetics, optimal timing for single-injection moving table peripheral CE-MRA can be determined to avoid venous enhancement.  Knowing this, system specific parameter choices (2D SENSE factor, bandwidth, flip angle, TR and TE) can be uniquely determined to maximize SNR for any given patient at the desired acquisition time.  We describe the theory behind these choices, show how to construct protocols to achieve maximal SNR with minimal venous enhancement, and demonstrate clinical examples (MRA vs DSA).

YiJing Wu¹, Kevin M. Johnson¹, Julia Velikina¹, Patrick Turski², Charles A. Mistretta²

¹University of Wisconsin, Madison, Wisconsin, USA; ²University of Wisconsin Medical School, Madison, Wisconsin, USA

Phase Contrast (PC) HYPR FLOW employs PC VIPR images as the composite and reconstructs the first pass Time Resolved Contrast Enhanced (TR-CE) VIPR acquisition using HYPR LR technique. HYPR FLOW decouples the temporal resolution, which is defined by TR-CE VIPR acquisition, from the spatial resolution and SNR, which depend on the PC VIPR acquisition, resulting in both high temporal resolution and isotropic spatial resolution with preserved SNR from the PC images. In addition, the phase contrast scan will add flow information to the CE-MRA time frames and provide velocity information suitable for the calculation of hemodynamic parameters such as pressure map and wall shear stress (WSS) which are potentially beneficial for understanding of the physiologic conditions behind diseases such as arterio-venous malformation (AVM). This abstract presents our clinical experience with HYPR FLOW including the contrast waveform fidelity, spatial resolution, SNR improvement over the VIPR method, and the physiological information beyond the contrast enhanced angiography.

Stefan Maderwald¹, ², Jens M. Theysohn¹, ², Oliver Kraff¹, ², Susanne C. Ladd¹, ², Karsten Wicklow³, Peter Schmitt³, Mark E. Ladd¹, ², Harald H. Quick¹, ²

¹Erwin L. Hahn Institute for Magnetic Resonance Imaging, Essen, Germany; ²Department of Diagnostic and Interventional Radiology and Neuroradiology, Essen, Germany; ³Siemens Medical Solutions, Erlangen, Germany

Three dimensional contrast-enhanced magnetic resonance angiography (CE-MRA) is a well established, reliable, and accurate technique for the evaluation of vascular pathologies of the intracranial vessels at 1.5T. When performing time-resolved 3D MRA of the intracranial vessels, the signal-to-noise ratio (SNR) achievable at 1.5T can be a limiting factor in simultaneously supporting the desired spatial and temporal resolution. In this study we evaluated the potential of 7-Tesla MRA for time-resolved high-resolution 3D CE-MRA of the intracranial vessels using the TWIST (Time-resolved angiography WIth Stochastic Trajectories) technique.

Henrik Jakob Michaely¹, Ulrike I. Attenberger², Christian Fink¹, Maximilian F. Reiser², Stefan O. Schoenberg¹

¹University Hosptial Mannheim, Mannheim, Germany; ²University of Munich, Munich, Germany

This study investigates the influence of the injection rate of gadofosvest on the image quality and the vessel enhancement during the steady state. In 21 healthy volunteers three different injection rates (1ml/s, 2ml/s, 4ml/s) were applied. No significant differences could be found in peak signal intensity in the thoracic and abdominal aorta as well as in the kidneys. With a slow injection rate of 1ml/s a significantly longer purely arterial imaging window was achieved.