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)

    - Return to Introduction Page

Figure 5     Figure 6     Figure 7     Figure 8       Figure 9     Figure 10

Figure 6
(A) Intensity histograms of an MRI volume before and after non-uniformity correction. (B) Individual intensity histograms of the six non-uniformity-corrected volumes. The histograms of the n3-, bfc-, eq-, hum- and cma-corrected volumes are similar to each other and to that of the uncorrected volume, whereas the histogram of the spm-corrected volume demonstrates a reduction of the gray-matter peak, and a global shift of the white-matter peak to lower intensity values.
 

A
 
 
B 
 

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