Whether or not you ultimately select GRAPPA for your experiment, it is important to make your determination objectively, taking into account your experimental needs, the benefits of the method, its failure modes and prior studies you can rely on for validation. (See "Beware of physicists bearing gifts!")
** Please note that the following information pertains to the GRAPPA implementation available as product on the Siemens Trio/TIM platform with VB15 software. If you have a different Siemens platform or a different vendor's scanner there may be significant differences in the implementation. **
A brief review of the GRAPPA method
If you don't have even a rudimentary understanding of parallel imaging (PI) generally or the GRAPPA method specifically, I would encourage you to stop reading this post now and go read at least one of these articles: Larkman & Nunes (2007) or Blaimer et al. (2004). Then come back when you're ready to proceed with a speedy review.