Table 3.
The coefficient of joint variation (cjv) between gray matter an white matter are presented for eight sets of BrainWeb simulated human brain images. Correct histogram waveforms should have cjv close to that of the standard. A smaller value of cjv implies better tissue contrast. Six sets of volumes had 3% noise level, while two sets of proton density-weighted data had 9% noise level.
| Scan Type | Data Set |
cjv(GM,WM) (%) |
|||||
|---|---|---|---|---|---|---|---|
| Standard | Biased | SPM | BSU | N3 | New | ||
| PDW (3%noise) | Normal | 56.4 | 164.9 | 59.4 | 68.5 | 60.7 | 83.2 |
| MS | 60.8 | 201.6 | 63.6 | 72.6 | 65.4 | 85.8 | |
| PDW (9%noise) | Normal | 157.1 | 250.2 | 153.9* | 212.0 | 154.2* | 179.5 |
| MS | 167.3 | 293.4 | 162.6* | 209.3 | 162.1* | 203.2 | |
| T1 (3%noise) | Normal | 44.6 | 67.2 | 47.4 | 50.0 | 47.0 | 53.7 |
| MS | 44.6 | 66.0 | 47.3 | 50.2 | 46.9 | 53.5 | |
| T2 (3%noise) | Normal | 68.1 | 100.5 | 75.2 | 262.0† | 95.7 | 72.7 |
| MS | 70.2 | 132.7 | 77.1 | 221.8† | 76.8 | 81.4 | |
BSU = BrainSuite, MS = multiple sclerosis, N3 = nonparametric nonuniform intensity normalization, New = the algorithm presented in this study, SPM = statistical parametric mapping,
cjv values of processed data smaller than those of the standard unbiased data (over correction),
cjv values of processed data larger than those of the original biased data (failed correction)