Need clarification

Submitted by Ramesh on Sat, 09/21/2013 - 01:12

 Dear Members

We have Philips Acheiva 1.5 T fMRI scanner. For my rs fMRI study I wnat to set the scan parameters as follows. Please give your suggession if there is any mistake.

EPI, TR=2 s, TE=30ms, dynamics=120, slices=50, Flip angle=90 degree, FOV=250x250, Matrix=64x64,  Voxel dimensions=3x3x3.  It will run for anout 8 minutes. 

I am getiing confusion in scan dynamics. Is it represents time point? If it is time point then TR(2) x time point (120) should take around 240 seconds (4 minutes). But when we set dynamics (time point) to 120, it shows 8 minutes. I didn't understand where I am doing mistake?

Please clear my doubt.

Thanks in advance
Ramesh


Submitted by ZHANG_RESTadmin on Mon, 09/23/2013 - 12:22

 as i undertood i will also consider dynamics as how many volumes in a run. 
 so please check your TR setting ag? 

 another question is, since your machine is 1.5T scanner, i doubt you can achieve a setting with slice number = 50, slice thickness = 3 in a TR = 2s.

 and, since your FOV is 250 250, your matrix is 64 *64, how comes your voxel dim is 3*3?

Submitted by Ramesh on Mon, 09/23/2013 - 23:51

Dear Sir, 

FOV and Matrix we set it as 250 250 and matrix is 64 64. Thought we set voxel dimention as 3 3 3 it assumes little different value. Please see the attached file and give your suggesion.

When TR is 2s and dynamic (volume) is180 the total duration should be TR x Dynamics ie 2x180=360s (6 min). But when I set 180 dynamics the system automatically shows 10.7 minutes. Whether my understanding wrong or machine is assuming some default value?

Please inform me.

With Thanks
Ramesh

Submitted by ZHANG_RESTadmin on Tue, 09/24/2013 - 10:57

 Sorry  I have not run Philip before, in Siemens the dynamic is exactly the volume number, but I don't know why it is not in Philip. Maybe you should consult your MR engineer.