your TR will increase and hence T2* contrast will change for more slices
when you are using 2DEPI based DTI acquisition (the common thing).
According to the Ernst angle, you will have to adapt your flip angle as
a function of the TR to achieve 90 magnetization again (ie in the
transversal plane).
I would have second thoughts mixing these 2 contrasts in one analysis...
Unless you use 3D EPI based DTI acquisition, in that case TR is really
short (in the order of 60 ms or so) and not depending on the number of
slices.
Cheers,
Bas
Op 17-09-10 14:39, Michel Thiebaut de Schotten schreef:
> As far as you solely add some slices I don't see any problem.
> cheers,
>
> michel
>
> On Sep 17, 2010, at 2:34 PM, Xu, Ben (NIH/NINDS) [E] wrote:
>
>
>> Hi,
>>
>> I have acquired DTI scans on a couple of subjects. Now, I'd like to increase a few slices for the rest of the subjects. The scan parameters and image dimension (i.e., FOV and slice thickness, etc) are otherwise identical. Will it be a problem to include scans with different slices later in data processing?
>>
>> Thanks much for your help in advance.
>>
>> Ben
>> -------------------------
>> Benjamin Xu, Ph.D.
>> 7D51 Bldg 10 Center Dr.
>> Human Cortical Physiology Section/NINDS
>> The National Institutes of Health
>> Bethesda, MD 20892
>> Tel: 301-402-7968
>> Fax: 301-480-2286
>> Email: [log in to unmask]
>>
> Michel Thiebaut de Schotten, PhD
> NATBRAINLAB
> ANR-CAFORPFC/ANR-HMTC
> CRICM-INSERM UMRS 975
> Pavillon de l'Enfance et l'Adolescence
> 47 Bd de l'Hôpital
> 75651 Paris Cedex 13, France
> www.natbrainlab.com
> +33 613579133
>
>
--
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Dr. S.F.W. Neggers
Division of Brain Research
Rudolf Magnus Institute for Neuroscience
Utrecht University Medical Center
Visiting : Heidelberglaan 100, 3584 CX Utrecht
Room B.01.1.03
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