title: Improved cerebral time-of-flight magnetic resonance angiography at 7 Tesla--feasibility study and preliminary results using optimized venous saturation pulses.
abstract: OBJECTIVE
  Conventional saturation pulses cannot be used for 7 Tesla ultra-high-resolution time-of-flight magnetic resonance angiography (TOF MRA) due to specific absorption rate (SAR) limitations. We overcome these limitations by utilizing low flip angle, variable rate selective excitation (VERSE) algorithm saturation pulses.
  
  
  METHODS
  Twenty-five neurosurgical patients (male n = 8, female n = 17; average age 49.64 years; range 26-70 years) with different intracranial vascular pathologies were enrolled in this trial. All patients were examined with a 7 Tesla (Magnetom 7 T, Siemens) whole body scanner system utilizing a dedicated 32-channel head coil. For venous saturation pulses a 35° flip angle was applied. Two neuroradiologists evaluated the delineation of arterial vessels in the Circle of Willis, delineation of vascular pathologies, presence of artifacts, vessel-tissue contrast and overall image quality of TOF MRA scans in consensus on a five-point scale. Normalized signal intensities in the confluence of venous sinuses, M1 segment of left middle cerebral artery and adjacent gray matter were measured and vessel-tissue contrasts were calculated.
  
  
  RESULTS
  Ratings for the majority of patients ranged between good and excellent for most of the evaluated features. Venous saturation was sufficient for all cases with minor artifacts in arteriovenous malformations and arteriovenous fistulas. Quantitative signal intensity measurements showed high vessel-tissue contrast for confluence of venous sinuses, M1 segment of left middle cerebral artery and adjacent gray matter.
  
  
  CONCLUSIONS
  The use of novel low flip angle VERSE algorithm pulses for saturation of venous vessels can overcome SAR limitations in 7 Tesla ultra-high-resolution TOF MRA. Our protocol is suitable for clinical application with excellent image quality for delineation of various intracranial vascular pathologies.
authors.affiliation: Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany; Department of Neurosurgery, University Hospital Essen, Essen, Germany.
authors.forename: Karsten H
authors.initials: KH
authors.lastname: Wrede
authors.affiliation: Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany; Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, Germany.
authors.forename: Sören
authors.initials: S
authors.lastname: Johst
authors.affiliation: Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany; Department of Neurosurgery, University Hospital Essen, Essen, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Dammann
authors.affiliation: Department of Neurosurgery, University Hospital Essen, Essen, Germany.
authors.forename: Neriman
authors.initials: N
authors.lastname: Özkan
authors.affiliation: Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Mönninghoff
authors.affiliation: Department of Neurology, Alfried Krupp von Bohlen und Halbach Hospital, Essen, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Kraemer
authors.affiliation: Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany; Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Maderwald
authors.affiliation: Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany; Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, Germany; Division of Medical Physics in Radiology (E020), German Cancer Research Center (DKFZ), Heidelberg, Germany.
authors.forename: Mark E
authors.initials: ME
authors.lastname: Ladd
authors.affiliation: Department of Neurosurgery, University Hospital Essen, Essen, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Sure
authors.affiliation: Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany; Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, Germany.
authors.forename: Lale
authors.initials: L
authors.lastname: Umutlu
authors.affiliation: Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, Germany.
authors.forename: Marc
authors.initials: M
authors.lastname: Schlamann
mesh_terms: D000328:Adult; D000368:Aged; D002533:Cerebral Angiography / Q000379:methods*; D002561:Cerebrovascular Disorders / Q000000981:diagnostic imaging*; D054022:Cerebrum / Q000098:blood supply / Q000000981:diagnostic imaging*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D002532:Intracranial Aneurysm / Q000000981:diagnostic imaging; D002538:Intracranial Arteriovenous Malformations / Q000000981:diagnostic imaging; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009072:Moyamoya Disease / Q000000981:diagnostic imaging; D011446:Prospective Studies