[Mristudio-users] B0 averages

[Theo van Erp]

Domenico,

You should be able to fully customize your sequence by scanning in free
mode, though I think this may require a research agreement.

Here are some instructions that may be helpful (you need Advanced User
access on your scanner for this):

1) Gain Advanced User access:

To gain Advanced User access, press the [escape]+[control] keys
simultaneously. If Windows Explorer is visible in the menu, then Advanced
User is already on. If not, turn on Advanced User mode on by going to:
[Programs]--->[Advanced User], then enter the Advanced User password.

2) Create DiffusionVectors.txt file:

Go to: [Windows Explorer]--->[My Computer]--->[MedSystem
C]--->[MedCom]--->[MriCustomer]--->[seq], and create a custom
"DiffusionVectors.txt"  (correct capitalization is important).

3) Verify the sequence parameters and copy sequence to scheduled scans:

Go back to exam window and to verify that:
*  DiffusionMode=Free
*  b=1000, or what you plan to specify for you non b=0 weighed images

If settings are correct, copy sequence to the list of scheduled scans. Once
the scan is completed, rename the "DiffusionVectors.txt" file so other Users
do not accidentally run your custom DTI sequence.

Your DiffusionVectors.txt file should look something like this:

---
# My custom diffusion vector set
# 5 b=0 images
# 4 diffusion weighted images

[directions=9]
CoordinateSystem = xyz
 
vector[0] = (  0.000000,  0.000000,  0.000000)
vector[1] = (  0.000000,  0.000000,  0.000000)
vector[2] = (  0.000000,  0.000000, 0.000000)
vector[3] = (  0.000000,  0.000000,  0.000000)
vector[4] = (  0.000000,  0.000000,  0.000000)
vector[5] = ( -0.525731, -0.850651, 0.000000)
vector[6] = ( -0.525731,  0.850651,  0.000000)
vector[7] = (  0.000000,  0.525731,  0.850651)
vector[8] = (  0.000000, -0.525731,  0.850651)
---

Best, Theo


On 12/4/09 8:10 AM, "Domenico Zaca" <domenico.zaca at gmail.com> wrote:

> Hi,
> 
> Does anyone know if there is a way to set up on a 3T Siemens Trio scanner
> a DTI sequence with a number of B0 acquisitions different than the number of
> acquisitions for each gradient direction (e.g 4 B0 averages and 2 averages for
> each of the other directions)?
> 
> Thanks,
> Domenico 
> 
> 
> 
> 
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Best, Theo

_____________________________________________________________
Theo G.M. van Erp, Ph.D.

Assistant Researcher
Associate Director of the Clinical Neuroscience Lab
NAPLS MRI Task Force Scientific Project Coordinator
Clinical Neuroscience Lab
Department of Psychology                vanerp at psych.ucla.edu
University of California Los Angeles    voice (310) 206-4902
1285 Franz Hall, room 5562              fax (310) 794-9740
Los Angeles, California,  90095-1563
http://www.bol.ucla.edu/~vanerp
http://napls.psych.ucla.edu
_____________________________________________________________



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