Usually, one-slice single-shot imaging takes less than 150ms, I believe. 50 slices thus should take about 50 x 150ms = 7.5 s.<div>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.</div>
<div><br></div><div>If you use repetition time of 17s, your total imaging time will be 17s x 36 = 10 min.</div><div><br></div><div>So, I would say, 17s is a bit too long and I recommend you to use the shortest TR, if possible.</div>
<div>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. </div><div><br></div>
<div>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<br><br><div class="gmail_quote">On Thu, Sep 23, 2010 at 11:51 AM, Lucas Lessa <span dir="ltr"><<a href="mailto:lucas_lessa@yahoo.com.br">lucas_lessa@yahoo.com.br</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><table cellspacing="0" cellpadding="0" border="0"><tbody><tr><td valign="top" style="font:inherit">Dear friends,<br><br>
I made a new protocol for a GE 1,5T HDX, using 33 directions and 50 slices with 2.2 mm thickness.<br>I did this because the vendor programmed a sequence that uses only 12 directions, 20 slices with 5 mm tichness and 1 NEX.<br>
I tried to obtain an isotropic image with more signal.<br>But to to this I've changed the TR to 17000 (the maximum).<br>Is there any problem?<br>And, if is possible, can anyone explain for me the significance of this?<br>
Thank you very much.<br><br>Lucas Lessa.<br></td></tr></tbody></table><br>
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