Comments on: Fat Suppression

By: fMRIguy

fMRIguy — Wed, 21 Dec 2011 18:26:50 +0000

I don’t know if I agree that fat saturation is mandatory for effective fMRI studies. It is true that fat will be incorrectly mapped spatially. However, we need to remember that signal variance through time is the most critical feature to preserve in fMRI data, and fat will contribute little to this. The argument that fat signal will decrease your sensitivity to true activation, and result in more false positives is only true if (1) fat increases the level of noise in the voxels in which it is mapped on top of brain tissue, or (2) fat exhibits task related variance. The first is possible, but the contribution of fat to noise through time is probably small considering its relatively poor vascularization. The second is highly unlikely, and can be virtually eliminated from possibility with appropriate fMRI task designs.

By: practiCalfMRI

practiCalfMRI — Wed, 16 Nov 2011 00:55:14 +0000

Re. Fat-Sat for fMRI?

Yes, it’s imperative that you have some sort of fat suppression (or avoidance) scheme with EPI for fMRI. You might be tempted to disable fatsat to save some time per slice, thus increasing the number of slices/TR. However, because the fat protons are always several hundred Hz off resonance from water, the N/2 ghosts from the fat will be VERY intense without fat signal suppression. If you could ensure that these intense ghosts don’t overlap brain signal then you would be okay, but if your image field-of-view is typical (below 24×24 cm) then overlap will be unavoidable, and you will have low statistical power in overlap regions (and probably a high number of false positive “activations” in these regions).

By: Fat-Sat for fMRI?

Fat-Sat for fMRI? — Sun, 15 May 2011 15:44:59 +0000

I see that I was mistaken in my previous post: Our center’s default fat suppression technique is in fact Spectral Presaturation with Inversion Recovery (SPIR – aka “fat-sat”). We also have the option of SPAIR or ProSet composite RF Pulses. I have read the that SPIR is mostly used for T1w imaging, while SPAIR is used for T2w imaging. However, for functional brain imaging we use T2* for measuring blood-oxygen-level- dependent (BOLD) signal. More specifically, we use fast-field echo (FFE) echo-planar imaging (EPI), with TR/TE 2000/35 msec, and flip angle of 90deg.

So my question is still: Is fat suppression appropriate or necessary for good T2* imaging of BOLD signal for fMRI?

thanks again!

By: Fat-Sat for fMRI?

Fat-Sat for fMRI? — Sun, 15 May 2011 14:52:42 +0000

I want to know if there is much advantage to using fat-sat for T2* EPI brain imaging — or really if there is a marked disadvantage to not using it. Within my desired scanning parameters, I get full brain coverage when I turn off fat-sat, but I miss the top of the brain when it is turned on. From what I have been reading, fat-sat is most beneficial for musculoskeletal imaging. I realize that sometimes – especially in obese patients – there may be fat on the forehead that can cause artifacts in EPI images, but mostly I scan healthy young adults. The STIR (called SPIR by Philips) fat-sat is turned on by default at our center, but I would like to turn it off to get better brain coverage.

Any opinions? Much thanks in advance.

By: Dave Higgins

Dave Higgins — Thu, 21 Apr 2011 09:15:52 +0000

That sentence means that the doctor’s opinion of the change in signal intensity is that it is not disease/pathology/damage etc.

In MRI we sometimes try to make signal from fat go away so signal from other tissues can be seen. Then signal which is abnormal can indicate a problem. The sentence is saying that the signal at your medial malleolus on a particular MRI scan is abnormal, but it’s not because your medial malleolus is abnormal, but because the fat signal wasn’t properly suppressed.

Of course this doesn’t completely rule out a problem with your medial malleolus, but (from that sentence alone) it seems that no problem was seen there in that proton density MRI scan.

By: G

Tue, 19 Apr 2011 19:50:00 +0000

Can somebody explain this sentence to me:

“Apparent increased signal intensity along the medial malleolus on proton density sequence is attributed to poor fat suppression”.

The “big knobby part” of my ankle (which I believe is the malleolus) is my concern. I don’t understand if this means that the MRI shows something wrong there or if it is inconclusive for some reason.

Thanks in advance.

By: Jane Redworth

Jane Redworth — Sun, 06 Feb 2011 15:58:01 +0000

Finally, i spent so much time looking digging for facts about fat suppression. I have been wanting to know the difference between composite and Spectrally-Selective RF Pulses. Way the go!thanks.

By: Ab the fat loss guy

Ab the fat loss guy — Sun, 17 Oct 2010 09:35:28 +0000

Does that mean that there is a chance that even if you apply any of fat suppression methods then it is still possible for the MRI to mess up results?

My mother has weight problem and she also developed Knee Tears of the meniscus, that’s what the first MRI showed.

But months later her second MRI showed that there is no tear in the knee, which the doctors say that is impossible, since tears cannot go away.

Reading this articles makes me believe may be fat in her body messed up the results