Thank you Ivana!
Ivana Drobnjak wrote:
> Hello Bjorn,
>
> No it is not a structural image. The first volume will have the
> strongest signal strength due to saturation effects i.e. spins will not
> be fully recovered (the Mz component will not reached its maximum) at
> the time of the RF pulse of the following volumes. In addition, the
> contrast is different because different tissue types require different
> amount of time to recover, so some take short time (T1 for white tissue
> type is around 500ms for 1.5T scanner) and some take long time (T1 for
> CSF is around 2500ms for 1.5T scanner) which means that you get less
> contrast between them in the volumes after the first. If you play with
> your T1 values and your TR you can change your contrasts... Also note
> that if your TR is large then the spin density becomes also quite
> prominent in the contrast. All these parameters are in the file called
> MRpar.
>
> Hope this helps,
> Ivana
>
>
> On 17 Apr 2008, at 13:48, Bjorn Roelstraete wrote:
>
>> Dear all,
>>
>> i noticed that, when i simulate several volumes in POSSUM, the first
>> volume is always much more detailed than the next ones. Is the first
>> volume some kind of structural image, perhaps?
>>
>> Thank you,
>> --
>> Bjorn Roelstraete
>> Ghent University
>> Department of Data-analysis
>> H. Dunantlaan 1, B-9000 Gent, Belgium
>> Tel: 32-9-2646434
>> E-mail: [log in to unmask]
>>
--
Bjorn Roelstraete
Ghent University
Department of Data-analysis
H. Dunantlaan 1, B-9000 Gent, Belgium
Tel: 32-9-2646434
E-mail: [log in to unmask]
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