COMPARISON OF NON-UNIFORMITY-CORRECTION ALGORITHMS USING
MULTIPLE REPEAT T1-WEIGHTED MRI SCANS OF A SINGLE SUBJECT
Six T1-weighted brain volumes of a normal volunteer were acquired over
a six-month period on a Siemens Vision 1.5T MRI scanner using the 3DFLASH
protocol (TR 35 msec, TE 6 msec, flip angle 45 degrees, one excitation,
165 x 220 mm FOV, 192 x 256 matrix, 100 slices, voxel dimensions 0.86 x
0.86 x 2.0 mm). Stripping (cortical isolation) masks were created for each
volume as described above, and the raw volumes and their corresponding
masks were aligned to a common coordinate system using the AIR 3.0 algorithm;
to insure that data interpolation effects were similar for the six test
volumes, for each volume an average transform to a Talairach reference
volume was employed. After the non-uniformity-correction algorithms were
run on the six aligned brain volumes, each corrected data volume was mean-normalized
to the corresponding input volume to facilitate quantitative comparisons
between algorithms.
- Biased Brain Phantom Data
(Figs. 1-4)
- High-Resolution T1-weighted
MRI Scans from Two Different Centers (Figs. 11-12)
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Figure 5
Figure 6 Figure
7 Figure 8
Figure 9 Figure
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Figure 8
Images of non-uniformity "extracted " by the six different correction
algorithms (one slice from each of six repeat scans). The n3,
bfc and spm images exhibit a low-spatial-frequency pattern;
however, the spm pattern appears to reflect the underlying brain
anatomy. The eq, hum and cma apatterns include
higher spatial frequencies and appear to be significantly influenced by
brain anatomy.
