Non-Contrast-Enhanced 4D Intracranial MR Angiography: Optimizations Using a Variable Flip Angle Approach
Peter Schmitt¹, Peter Speier¹, Xiaoming Bi², Peter Weale², Edgar Mueller^1
1MR Application & Workflow Development, Siemens AG, Healthcare Sector, Erlangen, Germany; ²Cardiovascular MR R&D, Siemens Healthcare, Chicago, IL, United States

A novel concept is presented to optimize a FAIR-type spin-labeling technique for non-contrast-enhanced 4D intracranial MR angiography, which is based on an ECG-triggered CINE-like b-SSFP acquisition of multiple 3D phases after selective and non-selective inversion, respectively. Based on numerical Bloch simulations and a volunteer study, it is shown that a variable flip angle scheme, with the flip angle continuously increasing from lower to higher values, results in a significantly longer persistence of the spin labeling. This in turn leads to an improved visualization of late-filling vasculature if compared to the standard approach with constant flip angle.

Initial Experience with Non-Contrast Enhanced Renal Angiography at 7.0 Tesla
Gregory John Metzger¹, Josh Simonson², Xiaoming Bi³, Peter Weale³, Sven Zuehlsdorff³, Eddie J. Auerbach¹, Kamil Ugurbil¹, Pierre-Francois Van de Moortele^1
1Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, United States; ²Radiology, University of Minnesota, Minneapolis, MN, United States; ³Siemens Medical Solutions, Chicago, IL, United States

The potential of non-contrast enhanced renal angiography at 7T was explored. In order to obtain consistent bilateral visualization of the renal arteries transmit B1 homogeneity was optimized using a subject dependent, three slice, small flip angle calibration scan acquired in a single breathold. High quality visulizaiton of proximal and distal renal arteries was obtained despite system limits on achievable transmit B1.

Comparison of Different Techniques for Non-Contrast –enhanced and  Contrast-Enhanced Magnetic Resonance Angiography of the Carotid Arteries
Harald Kramer¹, Val M. Runge², Kenneth D. Williams², L Gill Naul², Konstantin Nikolaou¹, Maximilian F. Reiser¹, Bend J. Wintersperger^1
1Department of Clinical Radiology, University Hospital Munich, Munich, Germany; ²Scott and White Memorial Hospital, Temple, TX, United States

For imaging of the carotid arteries several non contrast enhanced (non CE) and contrast enhanced (CE) techniques for MRA exist. Since the discovery nephrogenic systemic fibrosis possibly caused by Gd-contrast agents non CE techniques for MRA experience a renaissance. This study compares established and newly developed non CE and CE techniques for imaging of the carotid arteries including TOF, T2w darkblood, TrueFISP, dynamic CE MRA and high resolution CE MRA in an intraindividual setting. Image quality (IQ) as well as accuracy is evaluated. Standard CE MRA exhibits best IQ and accuracy directly followed by ECG gated non CE TrueFISP MRA.

Non-Contrast-Enhanced Hand MRA Using Multi-Directional Flow-Sensitive Dephasing
Zhaoyang Fan^1,2, Philip Hodnett¹, John Sheehan¹, Xiaoming Bi³, Sven Zuehlsdorff³, James Carr¹, Debiao Li^1,2
1Radiology, Northwestern University, Chicago, IL, United States; ²Biomedical Engineering, Northwestern University, Evanston, IL, United States; ³Cardiac MR R&D, Siemens Healthcare, Chicago, IL, United States

Noncontrast hand MRA using ECG-triggered 3D bSSFP with flow-sensitive dephasing (FSD) preparation has recently been demonstrated in patients with Raynauds disease. However, a conventional FSD module with flow-sensitizing gradient pulses applied in both readout and phase-encoding direction simultaneously is only sensitive to one-direction flow. We proposed a new FSD preparative module with two FSD sub-modules combined in series. In each submodule, gradient pulses are applied in one direction only. Its effectiveness was verified on a flow phantom and healthy volunteer hands. Additionally, a volunteer study was performed to investigate the MRA quality with FSD bSSFP using contrast-enhance MRA as reference.

Initial Evaluation of a New NCE Angiography Method in Patients and Comparison with TRICKS
Andrew Nicholas Priest¹, Ilse Joubert¹, Andrew P. Winterbottom¹, Teik Choon See¹, Martin John Graves¹, David John Lomas^1
1Radiology, Addenbrookes Hospital and University of Cambridge, Cambridge, United Kingdom

A recently demonstrated non-contrast-enhanced MRA technique (VANESSA) uses a controllable, modified MSDE preparation module to obtain bright- and dark-blood images, which are subtracted to give an image showing only flowing blood. In this study, the method is evaluated for the first time in patients: the peripheral vasculature is assessed and compared to standard contrast-enhanced imaging using TRICKS. The new sequence has lower artefact levels, and most vessels are fully visualised. However the popliteal arteries are often poorly seen, possibly because the distorted flow profiles in patients were not adequately accounted for in the determination of the sequence timing.

Max CAPR: Preliminary Clinical Studies with 5 Sec Acquisition Times
Clifton R. Haider¹, Eric A. Borisch¹, James F. Glockner¹, Petrice M. Mostardi¹, Stephen J. Riederer^1
1Radiology, Mayo Clinic, Rochester, MN, United States

In this work a previously described Cartesian Acquisition with Projection Reconstruction-like sampling method (CAPR) is undersampled to provide a net acceleration approaching 40 by eliminating all view sharing, termed Max CAPR, to provide 5 sec acquisition times for bilateral 3D CE-MRA of the calves with 1 mm isotropic spatial resolution. Max CAPR is shown to have improved temporal fidelity as compared to the reference view-shared sequence. Results with the new method from nine volunteer studies and 17 patients with suspected peripheral vascular disease are shown to provide images of improved temporal fidelity and comparable diagnostic quality to the view-shared reference.

MR Angiography in Pre-Operative Evaluation for Fibula Free-Flap Transfer Operation: Application, Branching Pattern Analysis and Septocutaneous Perforator Identification
Gurpreet Singh Sandhu^1,2, Rod P. Rezaee³, Katherine Wright⁴, John A. Jesberger², Mark A. Griswold^1,4, Vikas Gulani^1,2
1Radiology, University Hospitals of Cleveland, Case Western Reserve University, Cleveland, OH, United States; ²Case Center for Imaging Research, Case Western Reserve University, Cleveland, OH, United States; ³Case Center for Imaging Research, University Hospitals of Cleveland, Case Western Reserve University, Cleveland, OH, United States; ⁴Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States

Lower leg magnetic resonance angiography (MRA) images of fibula free-flap transfer operation (FFFTO) candidates are commonly reported only in terms of branching patterns and pathological lesions in the lower leg arterial tree. Recent technical developments have enabled the acquisition of lower leg MRA images with a sub-millimeter spatial resolution that can also be employed to locate peroneal artery septocutaneous perforators (SCPs). Here, we describe an extension of application of MRA for visualization of the SCPs in these patients and compare bolus-chase and time-resolved MRA techniques for identification of the branching patterns and SCPs.

Arterial Flow Characteristics in the Presence of Vascular Disease, and Implications for Non-Contrast MRA
Pippa Storey¹, Ruth P. Lim¹, Manjil Chatterji¹, Jian Xu², Hua Guo¹, David R. Stoffel¹, Vivian S. Lee^1
1Radiology Department, NYU School of Medicine, New York, NY, United States; ²Siemens Medical Solutions USA

Non-contrast techniques for peripheral MRA exploit differences in arterial flow velocity between diastole and systole, and produce exquisite bright-blood arterial images in healthy subjects. We studied the performance of ECG-gated 3D FSE-based MRA in 26 patients with vascular disease, and correlated the results with the patients’ arterial flow characteristics. Notable findings included the observation in 2 patients of reduced pulsatility and increased diastolic flow distal to a stenosis or occlusion. The presence of this ‘tardus parvus’ waveform correlated with poor depiction of the distal segments. Techniques with reduced flow sensitivity in diastole may perform better in such conditions.

Visualization of Acute Atrial Injury by 3 Tesla MRI
Eugene G. Kholmovski^1,2, Sathya Vijayakumar^1,2, Chris McGann^2,3, Nassir F. Marrouche^2,3
1UCAIR, Department of Radiology, University of Utah, Salt Lake City, UT, United States; ²CARMA Center, University of Utah, Salt Lake City, UT, United States; ³Department of Cardiology, University of Utah, Salt Lake City, UT, United States

Imaging protocol has been developed for assessment of acute atrial injury caused by RF ablation by 3T MRI. The protocol has been optimized and applied to study 50 immediately post-ablation cases. The main observations are the following: 1. Significant edema was detected not only in the regions subjected to RF energy (pulmonary veins ostia, posterior wall, septum) but also in distant regions (anterior wall). 2. LGE images demonstrate heterogeneous appearance of LA wall in the regions subjected to RF energy. Significant areas of these regions has minimal enhancement.

Magnetic Resonance Imaging of Pulmonary Embolism: Diagnostic Accuracy of Contrast-Enhanced 3D MRA, Contrast-Enhanced Low Flip Angle 3D Gradient Echo and Noncontrast Steady-State Free Precession Sequences
Bobby Kalb¹, Puneet Sharma¹, Gaye Ray¹, Daniel Karolyi¹, Hiroumi Kitajima¹, Khalil Salman¹, Diego R. Martin^1
1Radiology, Emory University, Atlanta, GA, United States

Magnetic resonance angiography (MRA) has a potential role for PE diagnosis, shown in multiple studies. Alternative MRA-like methods that further improve diagnostic accuracy and simplify the acquisition techniques remain an area of clinically important development.  MRA-like alternatives that produce enhancing signal from the vessel wall provide high contrast without need for bolus timing, and/or provide motion-insensitivity to respiration, with sequences including low flip angle (FA) 3D gradient echo (3D GRE), or steady state free precession (SSFP) sequences. Our study demonstrates the utility of low FA 3D GRE and SSFP sequences in conjunction with MRA for the diagnosis of PE.