FSPGR

[scottgloverjohnson]

I work at an animal hospital and I'm currently in an MR program. No protocols have been set up for our magnet that are appropriate for the variations in patient size/tissue differences, so I have been trying to set them up as best I can.

We have a 1.5T GE Brivo- the radiologists here have been interested in reformattable 3d acquisitions for T1 weighting. I suggested the FSPGR for better grey/white contrast, as our T1 FSE's have tended to look pretty washed out. However, when I acquire the images (15 lb patient, 8 channel knee coil, .8mm slice, 224x224, 180mm FOV, 2 NEX, out of phase TE, 30 FA), There is an sometimes an awful gibbs artifacts on the reformats! What might be the cause for that? Is there anything I can do to resolve this?

[stshea]

Gibbs ringing is normally caused by truncation of data before the Fourier transform. From a MR protocol perspective, this results from low spatial resolution (i.e. large voxels) and/or zero-filling interpolation methods that do not smooth the transition from k-space regions that have signal to the zero-filled regions that do not.

You did not list the number of partitions or slices that you were acquiring. If it's a very small number (10 or less), it's possible that this is the cause of your Gibbs ringing. In addition, many scanner manufacturers' software automatically interpolates in the "z" or slice direction for 3D scans. So, you may be thinking you are acquiring 16 slices at 0.8 mm resolution but you are actually only acquiring 8 slices at 1.6 mm. Adding partial fourier accelerations can further complicate this. I would suggest increasing the number of slices/partitions that you are acquiring and possibly consider increasing your through-plane resolution to see if that solves the problem.

[AndrewBworth]

This is veterinary MRI? You could post the images somewhere then so we could see them.

(04-02-2015 10:41 AM)scottgloverjohnson Wrote:  I work at an animal hospital and I'm currently in an MR program. No protocols have been set up for our magnet that are appropriate for the variations in patient size/tissue differences, so I have been trying to set them up as best I can.

We have a 1.5T GE Brivo- the radiologists here have been interested in reformattable 3d acquisitions for T1 weighting. I suggested the FSPGR for better grey/white contrast, as our T1 FSE's have tended to look pretty washed out. However, when I acquire the images (15 lb patient, 8 channel knee coil, .8mm slice, 224x224, 180mm FOV, 2 NEX, out of phase TE, 30 FA), There is an sometimes an awful gibbs artifacts on the reformats! What might be the cause for that? Is there anything I can do to resolve this?