Cerebral TOF angiography at 7T: Impact of B1+ shimming with a 16‐channel transceiver array

Time‐of‐flight (TOF) MR imaging is clinically among the most common cerebral noncontrast enhanced MR angiography techniques allowing for high spatial resolution. As shown by several groups TOF contrast significantly improves at ultrahigh field of B0 = 7T, however, spatially varying transmit B1 (B1+) fields at 7T reduce TOF contrast uniformity, typically resulting in suboptimal contrast and reduced vessel conspicuity in the brain periphery.

[1]  David Saloner,et al.  Intracranial time‐of‐flight MR angiography at 7T with comparison to 3T , 2007, Journal of magnetic resonance imaging : JMRI.

[2]  Alexis Amadon,et al.  Parallel-transmission-enabled magnetization-prepared rapid gradient-echo T1-weighted imaging of the human brain at 7T , 2012, NeuroImage.

[3]  Mark E Ladd,et al.  Time-of-Flight Magnetic Resonance Angiography at 7 T Using Venous Saturation Pulses With Reduced Flip Angles , 2012, Investigative radiology.

[4]  A. Macovski,et al.  Variable-rate selective excitation , 1988 .

[5]  Kâmil Uğurbil,et al.  Dynamically applied B1+ shimming solutions for non‐contrast enhanced renal angiography at 7.0 tesla , 2013, Magnetic resonance in medicine.

[6]  Jullie W Pan,et al.  RF shimming for spectroscopic localization in the human brain at 7 T , 2010, Magnetic resonance in medicine.

[7]  G. Metzger,et al.  Local B1+ shimming for prostate imaging with transceiver arrays at 7T based on subject‐dependent transmit phase measurements , 2008, Magnetic resonance in medicine.

[8]  R. Goebel,et al.  7T vs. 4T: RF power, homogeneity, and signal‐to‐noise comparison in head images , 2001, Magnetic resonance in medicine.

[9]  T. Ibrahim,et al.  Effect of RF coil excitation on field inhomogeneity at ultra high fields: a field optimized TEM resonator. , 2001, Magnetic resonance imaging.

[10]  T. Vaughan,et al.  Calibration Tools for RF Shim at Very High Field with Multiple Element RF Coils : from Ultra Fast Local Relative Phase to Absolute Magnitude B 1 + Mapping , 2007 .

[11]  Lin Tang,et al.  Studies of RF Shimming Techniques with Minimization of RF Power Deposition and Their Associated Temperature Changes. , 2011, Concepts in magnetic resonance. Part B, Magnetic resonance engineering.

[12]  D. Hoult.  Sensitivity and Power Deposition in a High‐Field Imaging Experiment , 2000, Journal of magnetic resonance imaging : JMRI.

[13]  Essa Yacoub,et al.  Spin echo functional MRI in bilateral auditory cortices at 7T: An application of B1 shimming , 2012, NeuroImage.

[14]  Michael B. Smith,et al.  Signal‐to‐noise ratio and absorbed power as functions of main magnetic field strength, and definition of “90°” RF pulse for the head in the birdcage coil , 2001, Magnetic resonance in medicine.

[15]  S. Maderwald,et al.  Pre-interventional assessment of a vertebrobasilar aneurysm with 7 tesla time-of-flight MR angiography. , 2009, RoFo : Fortschritte auf dem Gebiete der Rontgenstrahlen und der Nuklearmedizin.

[16]  Kawin Setsompop,et al.  Slice‐selective RF pulses for in vivo B  1+ inhomogeneity mitigation at 7 tesla using parallel RF excitation with a 16‐element coil , 2008, Magnetic resonance in medicine.

[17]  Johannes T Heverhagen,et al.  Time-of-Flight Magnetic Resonance Angiography at 7 Tesla , 2008, Investigative radiology.

[18]  W. Teeuwisse,et al.  Simulations of high permittivity materials for 7 T neuroimaging and evaluation of a new barium titanate‐based dielectric , 2012, Magnetic resonance in medicine.

[19]  Gülin Öz,et al.  Regional neurochemical profiles in the human brain measured by 1H MRS at 7 T using local B1 shimming , 2012, NMR in biomedicine.

[20]  W. Barber,et al.  Comparison of linear and circular polarization for magnetic resonance imaging , 1985 .

[21]  Jeroen Hendrikse,et al.  MR angiography of the cerebral perforating arteries with magnetization prepared anatomical reference at 7T: Comparison with time‐of‐flight , 2008, Journal of magnetic resonance imaging : JMRI.

[22]  Steen Moeller,et al.  B1 destructive interferences and spatial phase patterns at 7 T with a head transceiver array coil , 2005, Magnetic resonance in medicine.

[23]  M. Ferrari,et al.  Lenticulostriate Arterial Lumina Are Normal in Cerebral Autosomal-Dominant Arteriopathy With Subcortical Infarcts and Leukoencephalopathy: A High-Field In Vivo MRI Study , 2010, Stroke.

[24]  Zang-Hee Cho,et al.  Hypertension Correlates With Lenticulostriate Arteries Visualized by 7T Magnetic Resonance Angiography , 2009, Hypertension.

[25]  P. Börnert,et al.  Transmit SENSE , 2003, Magnetic resonance in medicine.

[26]  Steen Moeller,et al.  A geometrically adjustable 16‐channel transmit/receive transmission line array for improved RF efficiency and parallel imaging performance at 7 Tesla , 2008, Magnetic resonance in medicine.

[27]  K. Uğurbil,et al.  Manipulation of image intensity distribution at 7.0 T: Passive RF shimming and focusing with dielectric materials , 2006, Journal of magnetic resonance imaging : JMRI.

[28]  K. Uğurbil,et al.  Magnetic field and tissue dependencies of human brain longitudinal 1H2O relaxation in vivo , 2007, Magnetic resonance in medicine.

[29]  J. Lagendijk,et al.  7 T body MRI: B1 shimming with simultaneous SAR reduction , 2007, Physics in medicine and biology.

[30]  K Ugurbil,et al.  Simultaneous bilateral hip joint imaging at 7 Tesla using fast transmit B1 shimming methods and multichannel transmission – a feasibility study , 2012, NMR in biomedicine.

[31]  Michael B. Smith,et al.  Exploring the limits of RF shimming for high‐field MRI of the human head , 2006, Magnetic resonance in medicine.

[32]  H H Quick,et al.  Evaluation of Intracranial Aneurysms with 7 T versus 1.5 T Time-of-Flight MR Angiography – Initial Experience , 2009, RoFo : Fortschritte auf dem Gebiete der Rontgenstrahlen und der Nuklearmedizin.

[33]  Yudong Zhu,et al.  Parallel excitation with an array of transmit coils , 2004, Magnetic resonance in medicine.

[34]  Vasily L Yarnykh,et al.  Actual flip‐angle imaging in the pulsed steady state: A method for rapid three‐dimensional mapping of the transmitted radiofrequency field , 2007, Magnetic resonance in medicine.

[35]  Kamil Ugurbil,et al.  Neither Flat Profile Nor Black Spots : A Simple Method to Achieve Acceptable CP-like Mode Transmit B 1 Pattern for Whole Brain Imaging with Transmit Arrays at 7 Tesla , 2011 .

[36]  Michael Garwood,et al.  Localized 1H NMR spectroscopy in different regions of human brain in vivo at 7 T: T2 relaxation times and concentrations of cerebral metabolites , 2012, NMR in biomedicine.

[37]  Xiaoping Wu,et al.  Parallel excitation in the human brain at 9.4 T counteracting k‐space errors with RF pulse design , 2010, Magnetic resonance in medicine.

[38]  Michael Bock,et al.  Contrast enhancement in TOF cerebral angiography at 7 T using saturation and MT pulses under SAR constraints: Impact of VERSE and sparse pulses , 2012, Magnetic resonance in medicine.

[39]  Zang-Hee Cho,et al.  Imaging and analysis of lenticulostriate arteries using 7.0‐Tesla magnetic resonance angiography , 2009, Magnetic resonance in medicine.

[40]  D Atkinson,et al.  Improved MR angiography: magnetization transfer suppression with variable flip angle excitation and increased resolution. , 1994, Radiology.