thank you, Dr. Susumu. I will give it a try.<br><br>Pom<br><br><div class="gmail_quote">On Wed, Apr 7, 2010 at 2:25 PM, susumu mori <span dir="ltr"><<a href="mailto:susumu@mri.jhu.edu">susumu@mri.jhu.edu</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">Here is what I would do;<br><br>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.<br>
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<br>
<br>2mm: 112x112 matrix for 224x224 mm FOV. 96x96 for 192x192mm FOV could be too small for some subjects. 2mm slice<br><br>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.<br>
<br>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.<br><br>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. <br>
<br>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.<br><br>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.<br>
<br>Susumu<br><br><div class="gmail_quote"><div><div></div><div class="h5">On Thu, Apr 1, 2010 at 7:42 PM, Pom Sailasuta <span dir="ltr"><<a href="mailto:sailasuta@hmri.org" target="_blank">sailasuta@hmri.org</a>></span> wrote:<br>
</div></div><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;"><div><div></div><div class="h5">
Dear Dr. Susumu,<br> <br>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?<br> <br>thanks<br> <br>Napapon
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