I have installed and set up the HERMES and HERCULES sequences based on the Siemens VE11A–C, E, P installation guide from June 2020. As for setting up water reference scans for i. HERMES: GABA&GSH editing and ii. HERCULES, attached is a quick breakdown of the parameters I selected for each water ref. I am hoping someone on here may be able to let me know if these changes are correct, or what may need amending. Please let me know if I can help provide any further information.
Lastly, for a new study I am setting up, we are interested in quantifying: NAA, Ins, GABA+, Glx, GSH. Given that, would you anticipate that HERCULES and HERMES (GABA and GSH) would perform similarly for these metabs? If not, which sequence would you recommend?
Thank you for your help; it is greatly appreciated.
In the VE11A-C version, there is a note mentioning that the editing pulses are switched off during the unsuppressed water acquisition (page 6). As per these new guidelines, they will be applied, just in a different place as compared to the metabolite acquisition.
What is the impact of having the same editing pulses in the metabolite and unsuppressed water scans? As per VE11A-C, they would be switched off and thus would not be applied anyway, this is a bit confusing.
Will changing the unsuppressed editing pulses as recommended differently impact the eddy currents correction?
Does this hinder the comparison with previous datasets using the typical same parameters for metabolite and water scans?
In the HERMES literature, I still haven’t found any mention of a different edit frequency pulse scheme in the unsupp water. Do you anticipate that this can be a critical source of variability in results across different studies?
Starting from the VE11 sequences on, editing pulses are turned off for unsuppressed water acquisitions. In the earlier versions, these editing pulses were not turned off, but were applied in the downfield of the spectrum (7-10 ppm), so that it wouldn’t affect the observed metabolites in the upfield range.
Regarding the Eddy currents between the two acquisitions, they would be the same since the same gradients scheme are played out for both water unsuppressed and suppressed acquisitions. So this will not impact the Eddy current correction.
Thank you for your reply. So, we don’t have to worry about changing the editing pulses in the unsuppressed water scans. Also, all is good with previous datasets where these pulses were unchanged, as long as they were acquired with a V11 sequence. Do you confirm this?
I ran VE11A simulations to make sure there are no editing pulses when ‘Only RF off’ is selected for Routine >> Water supr. This settings correspond to unsuppressed water and there are no editing pulses in the simulation. So, ideally it should be okay not to change the editing pulses for the unsuppressed scans since the editing pulses are completely off.
If you have already acquired HERMES data with these settings in VE11A, it should be okay as well.
