◆In Neurosurgery The pyramidal tract is a crucial structure of motor function. Since brain shift occurs during neurosurgery ,
the intraoperative position of the pyramidal tract may change from that depicted on preoperative images. ◆Diffusion tensor imaging (DTI) Intraoperative high-magnetic-field MRI (1.5~3.0T) allows the visualization of the pyramidal tract bundle by employing DTI. However… It is difficult to take DTI using low-magnetic-field MRI (~0.5T). ◆Low magnetic field MRI It is...
Methods and Materials
1. Phantom study ◆ Phantom ① We created a brain parenchyma phantom. ② Using 0.4T vertical open MRI (APERTO,
Hitachi Medical Co.,
we tried various values of the EPI-DWI parameters. For example… TR,
Inter echo time (IET), Shot number ; ADA order,
centric order ③ The signal-to-noise ratio (SNR),
and distortion ratio (DR) were measured for each DWI. ◆ SNR measurement ① The region of interest (ROI) was set on the center of the phantom and subtraction image. ② We measured the signal...
1. Phantom study ◆ SNR measurement An increase in the NSA[Fig4.1.1,
(b)] and shot number (ADA order) [Fig4.1.2,
(d)] increased the SNR.
the SNR was saturated when the shot number (ADA order) was 5 to 6 [Fig4.1.2,
(d)]. ◆ DR measurement DR increased with the IET [Fig4.1.1,
(c)] and shot number (ADA and centric order) [Fig4.1.2] ,
but not with TR and NSA [Fig4.1.1,
Comparison between the shot number of the ADA order and centric order revealed that the centric order,
The pyramidal tract was clearly visualized when we applied the selected parameter values in a clinical case. The scan duration could be reduced by settingthe TR to 2000 msec,
and the NSA and shot numbercould be increased.
IET did not correlate with SNR,but it allowed the reduction of TE and bandwidth.Setting an optimal value of shot number and IETcould reduce the DR and provide better image quality.The pyramidal tract was clearly visualized when weapplied the selected parameter values in a...
Arya Nabavi ,
et al.: Serial Intraoperative Magnetic Resonance Imaging of Brain Shift.
Med Image Anal,
337-59 (2002). N.
Iseki : Intraoperative Diffusion-Weighted imaging for Visualization of the Pyramidal Tracts.
Part 1: Pre-Clinical Validation of the Scanning Protocol.
Minim Invasive Neurosurg,
(2008). Akio Ogura ,