Table 2.
3D Acquisition RSI vs. ePE: BRAINO Phantom Sensitivity Comparisona
| No Spatial filter | With Hamming | ||||||
|---|---|---|---|---|---|---|---|
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|
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| RSI | ePE | RSI/ePE | RSI | ePE | RSI/ePE | ||
| FVHM (cm3) | 0.5465 | 1.5955 | 0.34 | 1.5968 | 3.4957 | 0.46 | |
| tSNR (min−1/2) | tNAA | 28.14 (3.37%) | 58.13 (2.23%) | 0.48 | 90.54 (2.22%) | 95.07 (2.08%) | 0.95 |
| tCr | 22.56 (3.65%) | 46.96 (2.47%) | 0.48 | 73.94 (2.36%) | 77.60 (2.21%) | 0.95 | |
| tCho | 21.55 (5.95%) | 45.32 (4.44%) | 0.48 | 71.05 (4.13%) | 74.91 (4.01%) | 0.95 | |
| Ins | 12.57 (6.16%) | 25.39 (4.55%) | 0.49 | 40.78 (3.86%) | 42.03 (3.80%) | 0.97 | |
| Glx | 8.72 (8.27%) | 17.22 (5.01%) | 0.51 | 28.09 (5.14%) | 28.29 (4.67%) | 0.99 | |
Average mean sensitivity tSNR = SNR/√Taq in min−1/2 for all voxels with LCModel Crammer Rao lower bounds CRLB<20%, for the five metabolites listed. Without spatial filtering, for the RSI sequence, 96% of voxels in VOI had CRLB<20% for all five metabolites; the 4% of voxels which did not qualify were all on the edges of VOI. When the spatial Hamming filter was used, 100% of the voxels within VOI had CRLB<20% for all five metabolites. In parentheses, the average CRLB for all voxels included in analysis is shown, for that specific metabolite, sequence and processing. Hamming filter applied for ePE sampling was 3D spherical/ellipsoidal and it goes to zero (0.08) at the edge of the k-space sampled; for RSI, it was a product of a 2D filter covering a disk in XY-dir and a 1D filter in Z-dir. The metabolites analyzed are (LCModel sums used): tNAA (total N-acetyl-aspartate: NAA+NAAG), tCr (total Creatine: Cr+PCr), tCho (total Choline: PCho+GPC), Inositol (Ins+Gly), Glx (Glutamate/Glutamine: Glu+Gln).