Parallel imaging of head with a dedicated multi-coil on a 0.4T open MRI.
BACKGROUND
Parallel imaging is widely used for cylindrical magnetic resonance imaging (MRI); however, few studies apply parallel imaging to open MRI. We previously developed a parallel method called "RAPID" (rapid acquisition through a parallel imaging design) for imaging the heart on a 0.7T open MRI apparatus, and we have now developed a RAPID head coil and shading correction algorithm for imaging the brain with a 0.4T open MRI apparatus. Images acquired with RAPID were compared with those acquired using a conventional quadrature-detection (QD) head coil.


METHODS
The images were acquired using a dedicated 4-channel RF receiving coil consisting of a solenoid coil and surface coils. For MRI of the brain, we developed 2 methods to acquire the necessary calibration data: a pre-scan method that acquires the calibration data before the main scans and a self-calibration method that acquires the calibration data and imaging data simultaneously. We also modified the algorithm for calculating the shading distribution so that it only uses acquired image data and then corrects the shading.


RESULTS
RAPID was applied for T1-weighted, T2-weighted, fluid-attenuation inversion recovery (FLAIR), time-of-flight (TOF), and diffusion-weighted echo-planar (DW-EPI) imaging. The RAPID images had no visible unfolded artifacts or motion artifacts. Images with the same contrast as that with a conventional QD coil were acquired using the RAPID coil and shading correction.


CONCLUSIONS
These preliminary results show that RAPID can be applied to imaging of the head using a 0.4T open MRI apparatus.
Takizawa
Masahiro
M
Research and Development Center, Hitachi Medical Corporation, Shintoyofuta, Kashiwa, Chiba 277-0804, Japan. takizawa@rd.hitachi-medical.co.jp
Shimoda
Takahide
T
Nonaka
Masayuki
M
Mochizuki
Hiroyuki
H
Kawasaki
Shinji
S
Takeuchi
Hiroyuki
H
Tachibana
Miki
M
Takahashi
Tetsuhiko
T
D000465:Algorithms; D001931:Brain Mapping / Q000379:methods*; D004867:Equipment Design; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D019047:Phantoms, Imaging