Table 3.
Post hoc regression models
| Variable | R2* (s−1) Model 1 (full model) | R2* (s−1) Model 2 | R2* (s−1) Model 3 | QSM (ppb) Model 1 (full model) | QSM (ppb) Model 2 | QSM (ppb) Model 3 |
|---|---|---|---|---|---|---|
|
| ||||||
| Constant | 8.85 (8.81) | −5.92 (8.29) | 43.89 (3.28) | −27.58 (53.38) | −74.25 (46.46) | 176.30 (19.54) |
| Glial density (cells/mm2) | 0.049** (0.012) | 0.062*** (0.012) | - | 0.286** (0.072) | 0.318** (0.071) | - |
| log (%AO tau) | 3.80* (1.32) | - | 5.94* (1.59) | 15.59 (8.02) | - | 28.05* (9.47) |
|
| ||||||
| Observations | 25 | 27 | 25 | 25 | 27 | 25 |
| R 2 | 0.651 | 0.487 | 0.378 | 0.580 | 0.445 | 0.276 |
| Adjusted R2 | 0.619 | 0.466 | 0.350 | 0.541 | 0.423 | 0.245 |
| F-statistic | 20.50 | 23.69 | 13.95 | 15.16 | 20.03 | 8.77 |
| P-value | <0.00001 | <0.0001 | 0.001 | <0.0001 | 0.0001 | 0.007 |
Linear regression models with R2* and QSM as dependent variables, predicted by glial density and log-transformed %AO tau. In Model 1 (full model), MRI metrics were predicted by both glial density and log-transformed %AO tau; in Model 2, MRI metrics were predicted by only glial density; In Model 3, MRI metrics were predicted by only log-transformed %AO tau. All data were obtained from the substantia nigra pars compacta.
*
P < 0.01
**
P < 0.001
***
P < 0.0001
Abbreviations: NM+ = neuromelanin-positive; %AO = percent of area occupied by positive staining; R2* = apparent transverse relaxation rate; QSM = quantitative susceptibility mapping.