Open benoitberanger opened 2 years ago
pvelasco
commented
2 years ago What happens if you change the TR? Is the artifact still there? If so, does it change the frequency, or is it still the same?
Does the artifact go away if you disable the MB keeping the TR the same (reducing the number of slices)?
benoitberanger
commented
2 years ago @pvelasco I will try theses interesting tests when I have the opportunity.
However, I just had the occasion to verify the same RF spoiling on vs off on Prisma magnet. So, I can confirm the same artifact is present with theses hardware settings :
3T Prisma_fit @ VE11E
Sequence version : R016
julfou81
commented
1 year ago @benoitberanger , I had some time to do some in vivo tests on my side and +I could reproduce your observation:
3T Prisma in VE11C, sequence version: R017pre5 TR/TE=800/33.4 ms, 2.4mm iso, 60 slices, no gap, no GRAPPA, no partial Fourier, BW =2380 Hz/pix, fat saturation activated. 64CH Head/Neck coil, elements HC1-6 activated, Leak-Block kernel: on, SENSE reconstruction.
It was a short test, only 20 volumes per sequence: One with, and one without rf-spoiling. The GIF image below shows the TSNR between the acquisitions with, and without rf-spoiling.
Magnet & Software
3T Verio @ VB17A Sequence version : R016
Sequence parameters
The sequence is set for BOLD Multi-Echo on a Verio using the 32 channels headcoil. General parameters are : 3mm iso, 3 echos from [14 33 52]ms, mb=2, grappa=3, TR=1250ms I share the complete parameters if needed, as well as the images.
The artifact
The only parameter that changed here is the checkbox RF spoiling Showing you the 4D data is a bit tricky, but some stat maps make it clearly visible. When RF spoiling is checked, an artifact is present on the 4D data. Disabling the option removes the artifact.
stdev
tsnr
timeseries
Subject dependent ?
The pattern has been seen on 2 different subject just to check if it's subject depend or not. And no, the artifact is present on both subjects.
Going forward
From what I understood, RF spoiling is important to remove some stationary effects when TR << T1. Here with a BOLD sequence, TR is in the range of T1, so the option is not supposed to be necessary. However, I did not expect the option to actually cause an artifact I'm just curious about the root cause of this artifact.
Best, Benoît