My pleasure :)
>This is phase contrast tomography, so you can get the refractive index of the materials inside, and their speed.
This is way outside of my domain of competence, but if I understand correctly, this would not constitute a BOLD signal?
I'm skeptical of the idea that blood diffusion alone correlates with cerebral activity. With fMRI, you're looking at temporary gradients of de-oxygenated hemoglobin rather than a net direction of blood movement. This is sometimes confused with "blood flow", and I've been guilty of interchanging the two terms myself :/ I suspect the fluid dynamics of blood in the head is outrageously noisy and difficult to contrast out or filter though statistical means (because it's roughly random).
Concerning the relationship between neural activity and BOLD signal this paper [https://www.nature.com/articles/35084005] is a good starting point. I'll see if I can dig up the PDF for you.
I was hoping the brain was able somehow to vaso-constrict to direct its oxygen supply toward some region and that we could observe that. But from what I'm picking from you is that it's more like there is fluid everywhere, and cells are just consuming more or less kind of an open-buffet (versus cells waiting at the table and asking for more or less food).
^^found your paper without paywall but haven't read it yet [http://wexler.free.fr/library/files/logothetis%20(2001)%20ne...]
Holy shit, I am laughing my ass off. That domain belongs to a guy in my former lab :'D
http://casemed.case.edu/clerkships/neurology/Web%20Neurorad/...
Thank you so much (I have no medical knowledge and that is some key domain-knowledge I've missed). How much correlation with blood flow is there ? Maybe the BOLD signal can be reconstructed from the graphs of all mixed blood flow.
>What would we gain from using RF-diffraction as opposed to MR?
Main gain is practicality. Main usage would be for brain interface. This is phase contrast tomography, so you can get the refractive index of the materials inside, and their speed.
It won't be as precise as MRI, but it will be more practical. More portable. It doesn't use magnets so not limited by maximum magnetic fields. It is more scalable if you have compute power, meaning you can add some SDR to increase the resolution and bandwidth if necessary. Time resolution would probably be better as it doesn't need moving parts (if beam forming). It's cheaper. It's non invasive and usable 24/7.
We already have wifi imaging, so this is just putting it in favorable condition so as to extract more info from the brain. Basically until we can get the full connectome activation real time, we are just side-channel attacking the brain to extract some info. I'm just trying to grasp how much and how useful is the info we can get using existing techniques.
For example you put this device inside every monitor screen (for 60Ghz or in a TV sized box for 5Ghz) and a software controlled radio emitter behind the back of your head. And if the useful info bandwidth is sufficient we could have vastly better interface to the computer.
This can probably be adapted for room-sized continuous body health monitoring if the resolution is not sufficient or if the info extracted is not relevant enough.