Sorry, I must have forgot to attach the image.
Hedok
Hedok Lee wrote:
> Dear FSLers:
>
> This is regarding intensity variation in our DTI scan. We acquired
> 2.5x2.5x2.5mm(40 slices b=0,b=1250 12 directions) using Siemens 3.0T
> machine. After going through a FDT pipeline and compute ADC and FA maps,
> we noticed there is a small reduction in ADC near frontal lobe. The
> intensity of b=0 image also seems to suggest intensity reduction in the
> same area. I assumed this kind of intensity variation is due to bias-filed
> originated from inhomogenuity of a B0 field, and thus I tried to estimate
> the amount of bias-field by FAST. I segmented the b=0(T2W) image into 3
> compartments, and selected bias-field option. From what I understand the
> bias field image intensity represents a correction factor between I
> (observed)=I(ideal)*b(correction) as stated in the eq20 of the FAST
> technical note. To correct for the bias-field, I multiplied BOTH b=0 and
> b=1250 images by b(correction) image acquired from FAST, and reran the FDT
> pipeline again.
>
> I’m attaching ADC maps of before and after making the correction for the
> bias-field.
>
> I appreciate if someone can help me with this method. Is method valid?, ok
> but needs more work?, or definitely wrong?
>
> Any suggestion would be appreciated.
>
> Hedok
>
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