If you have a PET/MR system [0], you can probably do this "gold standard" comparison, and I know that one is used for research studies. I think you can piggy-back off a different study's healthy controls to write a paper like this, if that study already uses PET/MR and if adding an oxygen metabolite scan isn't a big problem. But that's speaking as someone who does not design experiments.

[0] https://www.siemens-healthineers.com/en-us/magnetic-resonanc...