Limit on number of averages (1024) in scanner console?

I’d like to run an hour long MRS scan, but the when I try to change the number of averages at the scanner console, I am limited to 1024 (~ 34 minutes, TR=2 sec). Is there a way around this? Or is there a reason not to run an hour long scan? I want to look at dynamic changes over time over the course of the scan

I am on a 3T Siemens MAGNETOM Prisma MRI scanner using the HERCULES sequence from Oeltzchner et al (Advanced Hadamard-encoded editing of seven low-concentration brain metabolites: Principles of HERCULES - ScienceDirect)

thank you!

Hi @sdw,

I believe this may be a hard limit on some platforms.

Depends a bit on what you’re trying to achieve… generally in-vivo, much over 10-15 minutes the cumulative effects of drift, subject motion etc may begin to outweigh any benefit of the longer scan. Some of these might be partially mitigated by breaking the scan into smaller chunks and doing a new prescan/shim in between.

However, if you specifically want to characterise drift for example, I’d suggest just sticking a couple of identical acquisitions in a row, without a new prescan in between.

In either scenario, if you’re collecting unsuppressed water reference data then also consider whether you want this to be updated too, or if doing so will disrupt the continuity…


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