Technical Note Nonenhanced Arterial Spin Labeled Carotid MR Angiography Using Three-Dimensional Radial Balanced Steady-State Free Precession Imaging Ioannis Koktzoglou, PhD, 1,2 * Joel R. Meyer, MD, 1,2 William J. Ankenbrandt, MD, 1,2 Shivraman Giri, PhD, 3 Davide Piccini, PhD, 4,5 Michael O. Zenge, PhD, 6 Oisin Flanagan, MD, 1,7 Tina Desai, MD, 2,8 NavYash Gupta, MD, 2,8 and Robert R. Edelman, MD 1,7 Purpose: To optimize and preliminarily evaluate a three- dimensional (3D) radial balanced steady-state free preces- sion (bSSFP) arterial spin labeled (ASL) sequence for non- enhanced MR angiography (MRA) of the extracranial carotid arteries. Materials and Methods: The carotid arteries of 13 healthy subjects and 2 patients were imaged on a 1.5 Tesla MRI system using an undersampled 3D radial bSSFP sequence providing a scan time of 4 min and 1 mm 3 isotropic resolution. A hybridized scheme that com- bined pseudocontinuous and pulsed ASL was used to maximize arterial coverage. The impact of a post label delay period, the sequence repetition time, and radiofre- quency (RF) energy configuration of pseudocontinuous labeling on the display of the carotid arteries was assessed with contrast-to-noise ratio (CNR) measure- ments. Faster, higher undersampled 2 and 1 min scans were tested. Results: Using hybridized ASL MRA and a 3D radial bSSFP trajectory, arterial CNR was maximized with a post label delay of 0.2 s, repetition times  2.5 s (P < 0.05), and by eliminating RF energy during the pseudocontinuous control phase (P < 0.001). With higher levels of undersam- pling, the carotid arteries were displayed in  2 min. Conclusion: Nonenhanced MRA using hybridized ASL with a 3D radial bSSFP trajectory can display long lengths of the carotid arteries with 1 mm 3 isotropic resolution. Key Words: carotid; angiography; arterial spin labeling; radial; nonenhanced J. Magn. Reson. Imaging 2014;00:000–000. V C 2014 Wiley Periodicals, Inc. MR ANGIOGRAPHY (MRA) is often used in the screen- ing and diagnosis of carotid artery stenosis. Conven- tional methods for nonenhanced MRA (NEMRA) of the carotid arteries include two-dimensional (2D) and 3D time of flight (TOF). TOF MRA methods are reasonably accurate (1), but artifacts and limitations in vascular coverage have rendered gadolinium based contrast- enhanced MRA (CEMRA) the preferred approach (2–4). Due to the prevalence of renal insufficiency in patients with carotid artery stenosis (5) and the asso- ciation of gadolinium based contrast with nephrogenic systemic fibrosis (6), however, there has been a spurt of interest in the development of more sophisticated NEMRA techniques (7,8). One method for high contrast NEMRA is to use arte- rial spin labeling (ASL) (9–11) in combination with a balanced steady-state free precession (bSSFP) readout (12). In performing ASL on commercial MRI systems with standard hardware, pulsed ASL (PASL) (11) or pseudocontinuous ASL (pCASL) (13) methods are typi- cally used. For carotid NEMRA in particular, pCASL was recently found to provide better signal-to-noise ratio (SNR) than PASL (14). Shortcomings of this work, which used a 3D Cartesian bSSFP imaging sequence, included anisotropic spatial resolution, the need for signal averaging to reduce sensitivity to motion arti- fact, and limited anatomical coverage providing poor display of the proximal common carotid arteries. 1 Department of Radiology, NorthShore University HealthSystem, Evanston, Illinois, USA. 2 The University of Chicago Pritzker School of Medicine, Chicago, Illi- nois, USA. 3 Siemens Healthcare, Chicago, Illinois, USA. 4 Advanced Clinical Imaging Technology, Siemens Healthcare IM BM PI, Lausanne, Switzerland. 5 Department of Radiology, University Hospital (CHUV) and University of Lausanne (UNIL)/Center for Biomedical Imaging (CIBM), Lau- sanne, Switzerland. 6 MR Product Innovation and Definition, Healthcare Sector, Siemens AG, Erlangen, Germany. 7 Northwestern University Feinberg School of Medicine, Chicago, Illi- nois, USA. 8 Department of Surgery, NorthShore University HealthSystem, Evan- ston, Illinois, USA. Contract grant sponsor: American Heart Association; Contract grant number: 12GRNT12080013. *Address reprint requests to: I.K., NorthShore University HealthSys- tem, Walgreen Jr. Building, G507, 2650 Ridge Avenue, Evanston, IL 60201. E-mail: ikoktzoglou@northshore.org Received January 11, 2014; Accepted March 26, 2014. DOI 10.1002/jmri.24640 View this article online at wileyonlinelibrary.com. JOURNAL OF MAGNETIC RESONANCE IMAGING 00:00–00 (2014) CME V C 2014 Wiley Periodicals, Inc. 1