fMRI Visualization

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.

fMRI Intro

A few sketchy notes...

fMRI Background

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

8 channels is hard (especially with masking)
40 MB of texture memory is getting smaller, but, still hard to fit in 64MB.
Pack the 3 activation datasets into 1.

Offset the voxel values (remember how)

RHM 2 4 9 AC 14 16 5 VG 22 24 9  -VG-AC 36 36 4

Overlapping Activations

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

Overlap Display, notice the merged color where the pink and the green overlap.

Channel Masking

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

Interpolate First?

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.

fmripanl