Table 3. Result of multiple regression analysis between EC and diffusion indices, and CSF BTV index.
| EC and ROI | Age (β/P) | MMSE (β/P) | Diffusion (β/P) | CSF BTV (β/P) | ANOVA (F/P) |
|---|---|---|---|---|---|
| Hippocampus | |||||
| AxD | −0.0003/0.824 | 0.002/0.360 | 309.3/0.0001* | −0.076/0.605 | 13.93/<0.0001 |
| MD | −0.0003/0.856 | 0.002/0.355 | 333.7/<0.0001* | −0.122/0.414 | 14.72/<0.0001 |
| RD | −0.0002/0.877 | 0.002/0.355 | 341.8/<0.0001* | −0.138/0.357 | 15.04/<0.0001 |
| ED EV | −0.001/0.442 | 0.001/0.617 | 296.8/0.0001* | −0.079/0.611 | 13.23/<0.0001 |
| Amygdala | |||||
| AxD | 0.002/0.467 | −0.003/0.284 | 379.8*/0.009* | −0.263/0.735 | 4.165/0.004 |
| MD | 0.002/0.438 | −0.003/0.274 | 394.4/0.015 | −0.078/0.918 | 3.900/0.006 |
| RD | 0.002/0.420 | −0.004/0.269 | 381.0/0.023 | 0.073/0.921 | 3.669/0.009 |
| ED EV | 0.002/0.276 | −0.002/0.472 | 378.8/0.0005* | 0.030/0.963 | 5.906/0.0004 |
| Thalamus | |||||
| AxD | 0.002/0.363 | 0.002/0.397 | 145.3/0.144 | 1.065/0.028 | 2.918/0.027 |
| MD | 0.002/0.328 | 0.002/0.365 | 181.8/0.058 | 1.022/0.030 | 3.351/0.014 |
| RD | 0.002/0.322 | 0.002/0.356 | 194.7/0.037 | 1.013/0.030 | 3.583/0.010 |
| ED EV | 0.001/0.499 | 0.003/0.107 | 366.1/<0.0001* | 0.782/0.050 | 10.02/<0.0001 |
| Insula | |||||
| AxD | −0.001/0.462 | −0.002/0.273 | 324.1*/0.0009* | 0.027/0.898 | 15.22/<0.0001 |
| MD | −0.001/0.518 | −0.002/0.190 | 270.4/0.010* | 0.176/0.397 | 13.27/<0.0001 |
| RD | −0.001/0.573 | −0.002/0.160 | 227.3/0.032 | 0.270/0.187 | 12.37/<0.0001 |
| ED EV | −<0.0001/0.981 | −0.001/0.563 | 403.0/<0.0001* | 0.003/0.988 | 20.45/<0.0001 |
| Corpus callosum | |||||
| AxD | −0.0003/0.813 | −0.002/0.317 | 180.3/0.006* | 0.213/0.007* | 10.08/<0.0001 |
| MD | −0.0001/0.927 | −0.002/0.376 | 174.9/0.003* | 0.184/0.023 | 10.59/<0.0001 |
| RD | −<0.0001/0.977 | −0.001/0.395 | 163.2/0.003* | 0.178/0.029 | 10.63/<0.0001 |
| ED EV | 0.0006/0.659 | −0.001/0.384 | 145.7/0.0005* | 0.144/0.076 | 12.00/<0.0001 |
In this analysis, we used the model as EC ≈ β1 * age + β2 * MMSE + β3 * diffusion index + β4 * CSF BTV index + ε (error). For the diffusion indices, we used AxD (ADC), MD, RD, and ED at EV. For the BTV index, we used CSF volume. Therefore, the four tested models were ADC and CSF, MD and CSF, RD and CSF, and ED_EV and CSF for each ROI. For EC ROI, α<0.05 divided by 4 tested models (0.05/4=0.0125) was used to determine the significance level. *, significant association between conductivity value and other indices. AxD (ADC), axial diffusivity; ANOVA, analysis of variance; BTV, boundary tissue volume; CSF, cerebrospinal fluid; EC, extra-neurite conductivity; ED, extra-neurite diffusivity; EV, extracellular volume; MD, mean diffusivity; MMSE, mini-mental state examination; RD, radial diffusivity; ROI, region of interest.