[Mristudio-users] What is the difference between a TR 7500 and a TR 17000?

[susumu mori]

Usually, one-slice single-shot imaging takes less than 150ms, I believe. 50
slices thus should take about 50 x 150ms = 7.5 s.
This is the repetition time; within this time you are done with one 3D
volume. With 33 directions and 3 b0s, for example, you spend 7.5s x 36
images = 4.5 min.

If you use repetition time of 17s, your total imaging time will be 17s x 36
= 10 min.

So, I would say, 17s is a bit too long and I recommend you to use the
shortest TR, if possible.
I noticed that some older GE scanners do not allow to use the minimum TR
such as 7.5s probably due to gradient heating. So, if the 17s is the
shortest you can do, then, that is your only option.

Other than that, 2.2 mm isotropic could be a bit too small for 1.5T with 33
DWIs. The SNR may be a noisy side depending on your coil performance. We do
2.5 mm for 1.5T

On Thu, Sep 23, 2010 at 11:51 AM, Lucas Lessa <lucas_lessa at yahoo.com.br>wrote:

> Dear friends,
>
> I made a new protocol for a GE 1,5T HDX, using 33 directions and 50 slices
> with 2.2 mm thickness.
> I did this because the vendor programmed a sequence that uses only 12
> directions, 20 slices with 5 mm tichness and 1 NEX.
> I tried to obtain an isotropic image with more signal.
> But to to this I've changed the TR to 17000 (the maximum).
> Is there any problem?
> And, if is possible, can anyone explain for me the significance of this?
> Thank you very much.
>
> Lucas Lessa.
>
>
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