Optimization of Magnetization-Prepared 3-Dimensional Fluid Attenuated Inversion Recovery Imaging for Lesion Detection at 7 T

PurposeThe aim of this study was to optimize the 3-dimensional (3D) fluid attenuated inversion recovery (FLAIR) pulse sequence for isotropic high-spatial-resolution imaging of white matter (WM) and cortical lesions at 7 T. Materials and MethodsWe added a magnetization-prepared (MP) FLAIR module to a Cube 3D fast spin echo sequence and optimized the refocusing flip angle train using extended phase graph simulations, taking into account image contrast, specific absorption rate (SAR), and signal-to-noise ratio (SNR) as well as T1/T2 values of the different species of interest (WM, grey matter, lesions) at 7 T. We also effected improved preparation homogeneity at 7 T by redesigning the refocusing pulse used in the MP segments. Two sets of refocusing flip angle trains—(a) an SNR-optimal and (b) a contrast-optimal set—were derived and used to scan 7 patients with Alzheimer disease/cognitive impairment and 7 patients with multiple sclerosis. Conventional constant refocusing flip MP-FLAIR images were also acquired for comparison. Lesion SNR, contrast, and lesion count were compared between the 2 optimized and the standard FLAIR sequences. ResultsWhole brain coverage with 0.8 mm3 isotropic spatial resolution in ∼5-minute scan times was achieved using the optimized 3D FLAIR sequences at clinically acceptable SAR levels. The SNR efficiency of the SNR-optimal sequence was significantly better than that of conventional constant refocusing flip MP-FLAIR sequence, whereas the scan time was reduced more than 2-fold (∼5 vs >10 minutes). The contrast efficiency of the contrast-optimal sequence was comparable with that of the constant refocusing flip sequence. Lesion load ascertained by lesion counting was not significantly different among the sequences. ConclusionMagnetization-prepared FLAIR-Cube with refocusing flip angle trains optimized for SNR and contrast can be used to characterize WM and cortical lesions at 7 T with 0.8 mm3 isotropic resolution in short scan times and without SAR penalty.

[1]  Mike P. Wattjes,et al.  Lesion detection at seven Tesla in multiple sclerosis using magnetisation prepared 3D-FLAIR and 3D-DIR , 2011, European Radiology.

[2]  D Le Bihan,et al.  kT‐points: Short three‐dimensional tailored RF pulses for flip‐angle homogenization over an extended volume , 2012, Magnetic resonance in medicine.

[3]  T. Benner,et al.  Focal cortical lesion detection in multiple sclerosis: 3 tesla DIR versus 7 tesla FLASH‐T2* , 2012, Journal of magnetic resonance imaging : JMRI.

[4]  Julien Cohen-Adad,et al.  In vivo evidence of disseminated subpial T2* signal changes in multiple sclerosis at 7T: A surface-based analysis , 2011, NeuroImage.

[5]  B. Trapp,et al.  Subpial Demyelination in the Cerebral Cortex of Multiple Sclerosis Patients , 2003, Journal of neuropathology and experimental neurology.

[6]  Philip M Robson,et al.  Brain MR imaging at ultra-low radiofrequency power. , 2011, Radiology.

[7]  D. Hoult,et al.  Selective population inversion in NMR , 1984, Nature.

[8]  Joseph V. Hajnal,et al.  Use of Fluid Attenuated Inversion Recovery (FLAIR) Pulse Sequences in MRI of the Brain , 1992, Journal of computer assisted tomography.

[9]  A. C. Brau,et al.  A Method for Autocalibrating 2-D Accelerated Volumetric Parallel Imaging with Clinically Practical Reconstruction Times , 2007 .

[10]  Peter R Luijten,et al.  High‐resolution magnetization‐prepared 3D‐FLAIR imaging at 7.0 Tesla , 2010, Magnetic resonance in medicine.

[11]  David Pitt,et al.  T1 and proton density at 7 T in patients with multiple sclerosis: an initial study. , 2012, Magnetic resonance imaging.

[12]  T. Parrish,et al.  3-D FLASH imaging using a single surface coil and a new adiabatic pulse, BIR-4. , 1990, Investigative radiology.

[13]  Robert A. Gross,et al.  Consensus recommendations for MS cortical lesion scoring using double inversion recovery MRI , 2011 .

[14]  Eric E. Smith,et al.  Cerebral White Matter , 2008, Annals of the New York Academy of Sciences.

[15]  Rohit Bakshi,et al.  Optimized double inversion recovery for reduction of T1 weighting in fluid‐attenuated inversion recovery , 2012, Magnetic resonance in medicine.

[16]  Richard Kijowski,et al.  Effects of refocusing flip angle modulation and view ordering in 3D fast spin echo , 2008, Magnetic resonance in medicine.

[17]  L. Pantoni.  Cerebral small vessel disease: from pathogenesis and clinical characteristics to therapeutic challenges , 2010, The Lancet Neurology.

[18]  R C Grimm,et al.  Initial clinical experience in MR imaging of the brain with a fast fluid-attenuated inversion-recovery pulse sequence. , 1994, Radiology.

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

[20]  Mandy M. A. Conijn,et al.  Cerebral Microbleeds on MR Imaging: Comparison between 1.5 and 7T , 2011, American Journal of Neuroradiology.

[21]  David H. Miller,et al.  MRI and the diagnosis of multiple sclerosis: expanding the concept of “no better explanation” , 2006, The Lancet Neurology.

[22]  Robin M Heidemann,et al.  Controlled aliasing in volumetric parallel imaging (2D CAIPIRINHA) , 2006, Magnetic resonance in medicine.

[23]  F Barkhof,et al.  Multicontrast Mr Imaging at 7 T in Multiple Sclerosis: Highest Lesion Detection in Cortical Gray Matter with 3d-flair 2.2 Multicontrast Mri at 7 T in Ms , 2022 .

[24]  F A Jolesz,et al.  Optimized single-slab three-dimensional spin-echo MR imaging of the brain. , 2000, Radiology.

[25]  Albert Macovski,et al.  Coronary Angiography with Magnetization‐Prepared T2 Contrast , 1995, Magnetic resonance in medicine.

[26]  Manojkumar Saranathan,et al.  Hippocampal CA1 apical neuropil atrophy and memory performance in Alzheimer's disease , 2012, NeuroImage.

[27]  Nikos Evangelou,et al.  Central veins in brain lesions visualized with high-field magnetic resonance imaging: a pathologically specific diagnostic biomarker for inflammatory demyelination in the brain. , 2013, JAMA neurology.

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

[29]  Jeffrey A. Cohen,et al.  Diagnostic criteria for multiple sclerosis: 2010 Revisions to the McDonald criteria , 2011, Annals of neurology.

[30]  S. Nelson,et al.  Quantitative in vivo magnetic resonance imaging of multiple sclerosis at 7 Tesla with sensitivity to iron , 2008, Annals of neurology.

[31]  À. Rovira,et al.  Brainstem lesions in clinically isolated syndromes , 2010, Neurology.

[32]  Wook Jin,et al.  Diagnosis of acetabular labral tears: Comparison of three-dimensional intermediate-weighted fast spin-echo MR arthrography with two-dimensional MR arthrography at 3.0 T , 2013, Acta radiologica.