Okay, so an MRI aligns all the hydrogen protons' axes with some EM coils, then RF pulses pull them out of alignment. Then when the RF is gone, the axes move back to being aligned. Axes re-align in different tissues at different speeds, creating a signal. This movement is measured by other EM coils and an image is made.
I've got a few questions I'm having trouble with.
A. I thought MRIs captured a 3d image all at once, but I've been reading that it builds it by taking cross sections. So it's just capturing a number of planes? What orientation, or can they modify that?
B. How do the 'other' coils measure the changes? Don't the coils creating the field interfere?
C. I thought atoms were at a scale too small to be affected by tissue differences. How is it that some re-orient more slowly than others at that scale?
Are there any good papers that describe the functioning of an MRI in more detail than wiki or howstuffworks? I'm kinda using this interest as a catalyst for learning calculus/vector calculus.
Pic related, it's my spine.
I'm more of an EEG sort of guy but I'll take a crack at it (there's an intro infopic on the /sci/ wiki if you look hard enough).
Yes, but remember that, for example, water density/pH value can change the amount of hydrogen ions (protons) somewhere. The alignment creates the field and the differential field impedence is what's measured. DTI is very similar, though it aligns water molecules and not protons and measures that as opposed to the impedence to get at internal structures rather than whole-body stuff. The former is what's at play in the human body, as well as impedance from denser objects like bone, thus making it for seeing dense visceral tissue (organs) and hard tissue like bone. I may have really cocked this up but I tried.
Dunno what that is. I'm an econ guy, but I used to be /3/. I had some MRIs and realized how fucking cool they are. MFW etc.
>answer about planes
so they pick one of those and move it through the body? How do they handle resolution/ number of times it takes an image? I always thought MRIs used some sort of voxel data (which I don't fully understand desu. something something vector field)
>Also, your spine is too straight and lacks lumbar lordosis.
Actually I think I've got anterior pelvic tilt (lordosis). But on the whole, you're right, everything L4 and up is too straight, while L5 and down is tilted too far forward. Should be smooth curves. I dunno what to do about it, all the doctors I've seen haven't noticed any of that and are too preoccupied telling me about the bulged disc I can't do much about.
Thanks for trying man, I'll go digging for that infopic.
Anyone else care to weigh in? Even if you don't really know it well, as long as you know it better than I do, it gives me more to go on/search about.
A: it captures frequecies and with the frequenties a PC can recreate all planes
The magnet in the MRI scanner has a range Lets say 1.00002T at the one end and 0.99998 Tat the opposit end
The larmor frequenties of the protons is affected by the magnet so at one end of te magnet they spin faster then at the other end
So when the scanner gets his echo the PC can recreate all of the planes but
(Thats how i thougt it worked)
Sorry for the bad english