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Punervasu:
I am not familiar with the diffusion toolbox, but I have some questions and comments. Are you sure about the directions in the attachment? Directions 6 and 12 seem to be identical; I think that in #12 the +0.5 should be -0.5. If the 12th direction was actually -0.5, then putting +0.5 into the calculation would produce an incorrect result. If you actually used +0.5 (repeated), then your directional sampling is not ideal, but your tensor calculations should be correct if you use the correct directions in the calculations.
Once you know the 12 directions, ADC in each direction can be calculated from the DW image and the b=0 image, D = {ln[S(b=0)/S(b>0)]}/b. Therefore, if the diffusion toolbox can calculate ADC maps, I assume the diffusion toolbox needs to know b, the direction file, and the b=0 and DW images.
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Peter B. Kingsley, MRI Physicist [log in to unmask]
Department of Radiology / MRI
North Shore University Hospital
300 Community Drive, Manhasset, NY 11030, USA
Tel (516) 562-2842 Fax (516) 562-3561
-----Original Message-----
From: SPM (Statistical Parametric Mapping) [mailto:[log in to unmask]] On Behalf Of Punervasu Vyas
Sent: Monday, August 21, 2006 4:57 PM
To: [log in to unmask]
Subject: [SPM] ADC Values
Dear All
I would like to know the way to evaluate the ADC values from diffusion
weighted images in SPM5. I need to check the reproducibility and accuracy of
apparent diffusion coefficient (ADC)
I have the diffusion toolbox needed for diffusion calculations. I have a set
of DW images acquired on a Siemens 1.5T scanner. The gradient direction file
is attached. Is there any thing else required. Anyhelp in this would be
useful.
Thanking you
Punervasu Vyas