[Mristudio-users] DTI protocol (resending using my registered email)

[susumu mori]

Here is what I would do;

1) resolution: 2-2.2mm isotropic. The latest RF coils are good enough to
deliver 2mm resolution with decent SNR. The smaller the image matrix, the
less distortion and higher SNR.
2.2mm: 112x112 matrix (zerofilled (interpolated) to 224x224 or 256x256) for
246x246 mm FOV or 96x96 (->192x192 or 256x256) for 211x211 mm FOV. 2.2 mm
slice

2mm: 112x112 matrix for 224x224 mm FOV. 96x96 for 192x192mm FOV could be too
small for some subjects. 2mm slice

2) the total number of DWIs: We do about 60 DWIs which should take 8-9 min.
30 DWI could provide decent SNR with 2.2 mm but a bit push for 2mm. 60 DWIs
mean; 30 orientation x 2, 20 x 3, 15 x 4, 12 x 5. In my opinion, they
provide very similar results but some reviewers believe the more
orientations the better. With simulation or extremely high SNR data (e.g.
>30 min scan), you start to see slight differences among these schemes but
with <10 min scan, they are usually indistinguishable. Add 5-6 b0 images.

3) TR: decided by the number of slices. Choose the shortest. Philips and
Siemens should be in 6-10s range. Old GE may have >10s due to a gradient
duty cycle issue.

4) TE: shortest. Siemens and GE should use double-echo type option (default
for Siemens and option for GE). Philips users may want to add few ms, which
would shorten the scan time drastically and reduce Eddy-current distortion.
Systematically increase the TE until you reach the shortest scan time. The
shortest TE often leads to longer scan time due to gradient duty cycle.

5) SENSE/GRAPPA/ASSET: On, factor = 2 - 2.5. Latest 32-channel head coil
could push to 3 but check the image quality before you decide to use.

6) Partial fourier: I prefer 100% and I feel the image is more robust
against motion, but this is just my subjective experience. Many use 70-80%,
which may improve SNR by using shorter TE.

Susumu

On Thu, Apr 1, 2010 at 7:42 PM, Pom Sailasuta <sailasuta at hmri.org> wrote:

> Dear Dr. Susumu,
>
> I am looking for recommended DTI scanning protocol on a 3T Philips Achieva
> scanner with 8-ch SENSE head coil. Can you point me to the location where I
> can find it?
>
> thanks
>
> Napapon
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