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>BOLD signal is really what you want Thank you so much (I have no medical knowledge and that is some key domain-knowledge I've missed). How much correlation wi

>BOLD signal is really what you want 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.

omginternets 9y ago
>Thank you so much 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 https://www.nature.com/articles/35084005] is a good starting point. I'll see if I can dig up the PDF for you.
- ericjang 9y ago
  Does de-oxygenated blood have a measurably different refractive index w.r.t. radio waves than oxygenated blood?
  - GistNoesis 9y ago
    No, that's why MRI has an undeniable advantage if it's what's important. What I was hoping, was that if the brain is somehow "opening" the various valves to bring more juice to certain area then that would be useful info (regardless of whether or not there is O2 in the blood, and where this O2 is consumed).
    - ericjang 9y ago
      I see, so you are proposing a way to infer capillary expansion/contraction as a way to measure blood flow.
  - omginternets 9y ago
    No, but de-oxygenated hemoglobin is paramagnetic, and therefore detectable using what's called T2*-weignted scan sequences. http://casemed.case.edu/clerkships/neurology/Web%20Neurorad/MRI%20Basics.htm http://casemed.case.edu/clerkships/neurology/Web%20Neurorad/...
- GistNoesis 9y ago
  You are right this is not a BOLD signal. 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)%20neurophysiological%20investigation%20of%20the%20basis%20of%20the%20fmri%20signal.pdf http://wexler.free.fr/library/files/logothetis%20(2001)%20ne...]
  - 9y ago

omginternets 9y ago

>Thank you so much 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 https://www.nature.com/articles/35084005] is a good starting point. I'll see if I can dig up the PDF for you.

ericjang 9y ago
Does de-oxygenated blood have a measurably different refractive index w.r.t. radio waves than oxygenated blood?
- GistNoesis 9y ago
  No, that's why MRI has an undeniable advantage if it's what's important. What I was hoping, was that if the brain is somehow "opening" the various valves to bring more juice to certain area then that would be useful info (regardless of whether or not there is O2 in the blood, and where this O2 is consumed).
  - ericjang 9y ago
    I see, so you are proposing a way to infer capillary expansion/contraction as a way to measure blood flow.
- omginternets 9y ago
  No, but de-oxygenated hemoglobin is paramagnetic, and therefore detectable using what's called T2*-weignted scan sequences. http://casemed.case.edu/clerkships/neurology/Web%20Neurorad/MRI%20Basics.htm http://casemed.case.edu/clerkships/neurology/Web%20Neurorad/...
GistNoesis 9y ago
You are right this is not a BOLD signal. 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)%20neurophysiological%20investigation%20of%20the%20basis%20of%20the%20fmri%20signal.pdf http://wexler.free.fr/library/files/logothetis%20(2001)%20ne...]
- 9y ago