resting state fMRI protocol at 3T and 7T

Submitted by jlcanlor on Thu, 08/27/2009 - 01:15

Hi there,

I am trying to setup a resting-state fMRI protocol to run in scanners of 3T and 7T with dementia patients, but I have not experience with BOLD sequences. I was wondering if anybody could help me to choose the best acquisition parameters for this purpose.

Thank you very much in advance.

Best regards,
Jose

Submitted by YAN Chao-Gan on Thu, 08/27/2009 - 23:26

My parameters in 3T scanner:




Image Acquisition. MRI data were acquired using a SIEMENS TRIO 3-Tesla scanner in the Beijing Normal University Imaging Center for Brain Research. The participants lay supine with the head snugly fixed by straps and foam pads to minimize head movement. The functional images were obtained using an echo-planar imaging sequence with the following parameters: 33 axial slices, thickness/gap = 3/0.6 mm, in-plane resolution = 64 × 64, TR = 2000 ms, TE = 30 ms, flip angle = 90º, FOV = 200 × 200 mm. In addition, a T1-weighted sagittal three-dimensional magnetization-prepared rapid gradient echo (MPRAGE) sequence was acquired, covering the entire brain: 128 slices, TR = 2530 ms, TE = 3.39 ms, slice thickness = 1.33 mm, flip angle = 7º, inversion time = 1100 ms, FOV = 256 × 256 mm, and in-plane resolution = 256 × 192.


Could Dr. Huang give more comments on 7T parameters please?

Submitted by jlcanlor on Fri, 08/28/2009 - 19:03

Thanks a lot, Chao-Gan. Could you tell me the acquisition time of this EPI sequence?

Optimized acquisition parameters for a 7T scanner (Siemens) would also be very useful for our purposes.

Best regards,
Jose

Submitted by YAN Chao-Gan on Sat, 08/29/2009 - 00:56

Hi!
Our acquisition time is 8 minutes.
I have no experience on 7T scanner.
You may refer to http://restfmri.net/forum/node/72 and ask Dr. Ruiwang Huang for some suggestion.
Best wishes!

Submitted by rh on Sat, 09/05/2009 - 13:28

 Hi,

I don't have any experience of performing fMRI study at 7T MR scanner. But I would like to add some points to remind you to consider when you want to use 7T to carry out the resting state fMRI study. 

Usually, BOLD-based images are acquired with gradient-echo (GE) EPI sequence. The signal depends on T2* value and other parameters, exp(-T2*/TE). 

T2*-value becomes short at high magnetic field. For gray matter, T2* value is about 40-60ms at 3T and 25-33 ms at 7T (Yacoub et al, MRM 2007, 45:588; Peters et al, MRI 2007, 25: 748 ). All methods to acquire T2*-weighted images needed to comply with the boundary condition of shortened T2* at 7T and thus the need for short echo times. For example, you can choose TE =35~50ms at 3T, but you have to choose TE ~ 25 ms at 7T (Speck et al, MAGMA 2008, 21:73-86). In addition, the optimized voxel size at 7T is also different from that at 3T. At 3T, the voxel size can be set around 3mm*3mm*3mm. At 7T, the voxel size need to be reduced in order to reduce the influence of susceptibility on the signal (Speck et al, MAGMA 2008, 21:73-86). 

Due to these reasons, some groups are trying to use spin-echo sequence to acquire BOLD signal (Schaefer et al, MAGMA 2008, 21:112) or use segmented GE-EPI sequence to acquire BOLD signal at 7T (Speck et al, MAGMA 2008, 21:73-86). 

If you have got a multi-channel head coil (for instance, 32 channels), it deserves to try to perform resting state fMRI study using the single-shot GE-EPI sequence or spin-echo EPI sequence .

By the way, which scanner are you using, Siemens or Phillips?

rh

Submitted by wdh on Mon, 08/31/2009 - 16:37

Is it possible to attach the protocol, like *.edx file? Or just one dicom file, so that other people can retrieve the protocol via Phoenix tool.