I have encountered an interesting issue: our sequence (3T MEGA-PRESS, Siemens product sequence) has an edit-off frequency of 4.7 ppm, whereas most of the literature I’ve read indicates an edit-off frequency of 7.5 ppm.
Is this discrepancy normal? Can anyone provide clarification or assistance?
It’s all good and normal. This isn’t the edit-off frequency itself, it’s the edit mirror frequency. The OFF and ON pulses are arranged symmetrically around that value.
For example, the difference between mirror frequency 4.7 ppm and edit frequency 1.9 ppm is 2.8 ppm, so the OFF pulse is at 4.7+2.8 = 7.5 ppm.
Thank you! But when I read the protocol from others, I saw they set it as 7.5 ppm.
SO_AC_049[Allen Cheong]64 _new.pdf (60.8 KB)
I mean, in that case it’d just be an edit-off at 7.5+(7.5-1.9) = 13.1 ppm (for conventional GABA editing, what matters only is that it’s far away from any metabolite signals)
