functional Magnetic Resonance Imaging, where functional areas of the brain are revealed.
Silver's fMRI Panel
fMRI images functional areas of the brain, for example left motor, right motor, language acquisition, etc.
A few sketchy notes...
- Blood flow increases to active regions of the brain - saturates it with oxygen.
- Deoxyhemoglobin is paramagnetic (no O2) and can be imaged with fMRI.
- While in scanner, subject exercises mental functions.
- This is extremely useful in neurosurgical planning.
fMRI volume data
- 2 volumes + one for each functional area
- Example has three functional areas
- Right hand motor
- Language acquisition
- Verbal Generation
- Each volume is 256x256x124 = 8MB.
Packing Activation data
Overlap Display, notice the merged color where the pink and the green overlap.
- Language Acquisition and Verbal Generation share part of the brain.
- When an overlap is detected a new "activation" area is created - using a single voxel value.
- Displayed as blend if both areas are visible, else in the color of the visible activation.
- -VG-AC 36 36 4
Needed to clearly see the activation area.
Use a masking LUT for the activations
Diagram shows VP1000 classifier method
Channel Masking on Radeon
- Activation as RGBA
- Read Gray and Vascular channels, pass Act
- Setup dependent read of 1D textures (LUT)
- Read LUTs for Gray&Vasc, + Act RGBA
- Subtract Act's Alpha from all channels of Gray/LUT result
- Add result + Act RGBA + Vasc/LUT
Examples from Radeon, IC below - we interpolate through other activation areas. This is really distracting and unusable.
We can do a hack with nearest neighbor (as seen up to right) still very distractions.
For "real" CI, we need to create RGBA on Radeon/NVIDIA, however, to do so doubles the amount of data. On VP1000, CI mode is built in.
Panel allows each area to be turned on and off.
Window/Level allows easy modification of transparency
Clip Plane is easy.
Radeon and VP1000
Demo data with RGBA does not fit on the Radeon with 64MB
VP1000 (below) image quality better. Much faster.
More Pretty Pictures
last: May 31, 2003