TABLE4.
Mean corrected SNR (CSNR: cm−3 min−1/2) values and percentage of voxels with detectable lipid for all combination techniques for NAA in NAWM in patients.* CSNR values were calculated according to Equation 12 to account for differences in acquisition and repetition times and the effective spatial resolution. Voxels were considered to have either ‘low to moderate’ aliased lipid if the lipid SNR was greater than 25% of the mean NAA SNR in NAWM or an ‘extreme’ amount of aliased lipid as defined by a lipid SNR equal to or greater than the mean NAA SNR in NAWM. The extreme lipid case negatively influences the result of the WSVD and FPphasing combination, causing this to fail to combine signals from contaminated voxels properly†
| Cycle with residual water | Cycle without residual water | ||||||
|---|---|---|---|---|---|---|---|
| Methods | CSNR | %voxels (Lip>25%NAA) | % voxels (Lip≥NAA) | Methods | CSNR | % voxels (Lip>NAA) | % voxels (Lip≥NAA) |
| RWvoxel | 8.0±1.5 | 25.4±19.9 | 1.4±3.7 | NAAvoxel | – | – | – |
| GLSRW | 7.8±1.5 | 26.1±20.4 | 1.2±3.5 | GLSNAA | – | – | – |
| FPphasing | 8.0±1.5 | 25.4±20.0 | 1.4±3.9 | FPphasing | 8.2±1.7 | 31.3±21.8 | 2.4±6.3 |
| WSVD | 7.7±1.4 | 25.5±19.4 | 1.5±3.9 | WSVD | 8.0±1.8 | 33.5±23.8 | 4.3±2.7 |
| RWcentral | 7.3±1.3 | 26.1±19.2 | 1.1±3.2 | NAAcentral | – | – | – |
| RWvoxel‡ | 8.6±1.6 | 28.8±20.9 | 1.0±2.8 | ||||
Standard deviations between scans are shown as mean±SD. N = 105 exams, 51 patients.
30% of all patients had extreme lipid contamination.
Combination parameters estimated from the other cycle.