Disclaimer: This isn't an April Fool!
I'd like to
use the collective wisdom of the Internet to discuss the pros and cons of
a general approach to simultaneous multislice (SMS) EPI that I've been thinking about recently,
before anyone wastes time doing any actual programming or data acquisition.
Multi-echo EPI for de-noising fMRI data
There has been quite a lot of interest in using multi-echo EPI to characterize and de-noise time series data, e.g.
http://www.ncbi.nlm.nih.gov/
http://www.ncbi.nlm.nih.gov/
These methods rest
on one critical aspect: they use in-plane parallel imaging (GRAPPA or
SENSE, usually depending on the scanner vendor) to render the per slice
acquisition time reasonable. For example, with R=2 acceleration it's possible to get
three echo planar images per slice at TEs of around 15, 40 and 60 ms. The multiple
echoes can then be used to characterize BOLD from non-BOLD signal
variations, etc.
The immediate problem with this scheme is that the per
slice acquisition time is still a lot longer than for normal EPI, meaning less brain coverage. The
suggestion has been to use MB/SMS to regain speed in the slice
dimension. This results in the combination of MB/SMS in the slice
dimension and GRAPPA/SENSE in-plane, thereby complicating the
reconstruction, possibly (probably) amplifying artifacts, enhancing motion sensitivity, etc. If we could eliminate the in-plane parallel imaging and
do all the acceleration through MB/SMS then that would possibly reduce some of the
artifact amplification, might simplify (slightly) the necessary
reference data, etc.
A different approach?
