Optimized RF excitation for anatomical brain imaging of the occipital lobe using the 3D MDEFT sequence and a surface transmit coil

An RF excitation scheme is presented for anatomical imaging of occipital brain areas at 3T using the 3D modified driven equilibrium Fourier transform (MDEFT) sequence and a transmit‐receive surface coil. Surface coils operated in the transmit mode usually display a high B1 inhomogeneity. This causes variations of the flip angle and impairs fat saturation, resulting in blurring, signal losses, and artifacts due to high scalp intensities. A composite binomial pulse with one spectral component for water selective excitation and one spatial component for B1 inhomogeneity compensation is presented. It is shown experimentally that the pulse prevents image blurring and reduces the scalp signal considerably. The total pulse duration of only 2.4 ms is compatible with the relatively short repetition times (TRs) required for MDEFT imaging. The method is particularly useful for certain applications in neuroimaging that require technical equipment that is too large for standard coils or should not be exposed to RF fields. Magn Reson Med 53:1212–1216, 2005. © 2005 Wiley‐Liss, Inc.

[1]  M. Garwood,et al.  B1-insensitive, single-shot localization and water suppression. , 1996, Journal of magnetic resonance. Series B.

[2]  M. S. Silver,et al.  Highly selective {π}/{2} and π pulse generation , 1984 .

[3]  J. Ashburner,et al.  Multimodal Image Coregistration and Partitioning—A Unified Framework , 1997, NeuroImage.

[4]  Klaas Nicolay,et al.  Adiabatic rf pulses: applications to in vivo NMR , 1997 .

[5]  R Turner,et al.  RF inhomogeneity compensation in structural brain imaging , 2002, Magnetic resonance in medicine.

[6]  P A Bottomley,et al.  In vivo nuclear magnetic resonance chemical shift imaging by selective irradiation. , 1984, Proceedings of the National Academy of Sciences of the United States of America.

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

[8]  C D Claussen,et al.  Highly selective water and fat imaging applying multislice sequences without sensitivity to B1 field inhomogeneities , 1997, Magnetic resonance in medicine.

[9]  J. Hogg.  Magnetic resonance imaging. , 1994, Journal of the Royal Naval Medical Service.

[10]  V. Tronnier,et al.  Active deep brain stimulation during MRI: A feasibility study , 2004, Magnetic resonance in medicine.

[11]  M. Raichle,et al.  Anatomic Localization and Quantitative Analysis of Gradient Refocused Echo-Planar fMRI Susceptibility Artifacts , 1997, NeuroImage.

[12]  Jorge Gonzalez-Martinez,et al.  MR imaging-related heating of deep brain stimulation electrodes: in vitro study. , 2002, AJNR. American journal of neuroradiology.

[13]  A Macovski,et al.  Three‐dimensional spectral‐spatial excitation , 1997, Magnetic resonance in medicine.

[14]  Single‐shot, B1‐insensitive slice selection with a gradient‐modulated adiabatic pulse, BISS‐8 , 1996, Magnetic resonance in medicine.

[15]  D W Piraino,et al.  Fat suppressed MRI of articular cartilage with a spatial‐spectral excitation pulse , 1998, Journal of magnetic resonance imaging : JMRI.

[16]  R Turner,et al.  Optimisation of the 3D MDEFT sequence for anatomical brain imaging: technical implications at 1.5 and 3 T , 2004, NeuroImage.

[17]  D. Rothman,et al.  Adiabatic slice-selective excitation for surface coils. , 1997, Journal of magnetic resonance (San Diego, Calif. 1997 : Print).

[18]  F Schick.  Simultaneous highly selective MR water and fat imaging using a simple new type of spectral‐spatial excitation , 1998, Magnetic resonance in medicine.

[19]  Ravi S. Menon,et al.  Imaging at high magnetic fields: initial experiences at 4 T. , 1993, Magnetic resonance quarterly.