General image quality
fMRI quality control
*fMRI data. Quality: 4/4. Notice that the color range reveals that there is a major bug in the numerical range. So, look at your data!!!
*These are raw images, direct comparison of gradient-echo EPI and spin-echo EPI in the same subject. Notice this is low-resolution (3mm? 4mm?), and notice the ghosts. Notice the major different in signal dropout across the sequences. This is likely left-right phase encode direction. Notice that there is major distortion in the spin-echo image.
**OLD images. Major inhomogenity (asymmetry across hemisphere). Gray/white contrast is surprisingly high. Notice left-right distortion.
*Raw (or minimally preprocessed) 0.8-mm fMRI volumes. Notice strange phase artifacts on right side (concentric circle stuff). Notice thermal noise is relatively high. Notice clear signs of dropout. There is an overall dynamic artifact that is very prominent in the center of the brain (notice this affects only PART of the volume). (Breathing / field related?). Overall quality (for sub-mm data): pretty good!
*A pretty good quality modern conventional 2mm fMRI (raw data). Notice field of view cuts off the back of the brain.
*0.8-mm mean volume after pre-processing fMRI. Notice the black holes likely indicating vessels. Notice that overall, the fidelity/quality of these images is quite good. Also, visually compare this to the raw 0.8mm images above.
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Watch an entire fMRI scan session (after data pre-processing). The white square in the upper left indicates the start of a new run.
*Signal dropout in T2* weighted fMRI images. This is typical and inevitable (for gradient-echo EPI).
3D anatomical acquisition motion artifacts
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*Big head motion/displacements for a long 3D sequence give rise to weird blurry/artifacted anatomical images. It's brain-like, but the finer scale details are messed up. (Navigators can be effective to help compensate for small shifts over the course of a scan.)
Thermal noise visible in white matter
*T1-weighted volume. Notice that there is visible thermal noise in the white matter (which may be fine/sufficient/expected, depending on what you are doing).
Uncommon vessel formations
The crosshair indicates a big vessel (?) that lives inside of the white matter. Not an artifact; it's a real biological occurrence.
T2* analogue for the image above.
Phantom imaging for quality control
*Compare and contrast the low-res and the high-res images. Fun.
Tissue signals differ across contrasts
*T1- vs. T2- comparison. Notice that white matter, gray matter, and CSF have different relative intensities across these two different tissue contrasts. Notice the CSF is very very bright in the T2. Notice the sagittal sinus at the very top (very bright in the T1 (looks similar to gray matter) and very dark in the T2).
*Rapid fMRI movie of raw data. Check image stability, subject head stability, thermal noise. Notice there is some fluid/CSF dynamics near the brain stem and that is expected. If you scrub quickly, you can see the slow change in head position.
*Lots of distortion, big dropout. Thermal noise is relatively high (at least compared to the previous example).
*Notice strange nonlinear dynamic shifts and jumps. Notice the brain distortion.