FIGURE 5.

Association between AD biomarkers and CBF. A–C, Scatterplots illustrating the association between global median GM perfusion and CSF Aβ1–42/Aβ1–40 ratio (A), CSF p‐tau181 (B), and hippocampal volume (adjusted by TIV; C). Data points represent individual subject values, regression lines depict group‐specific trends, with the dotted line for the association in the overall participants and the purple‐dashed line for the non‐eCU population only. Shaded areas indicate 95% confidence intervals. Shapes represent the diagnostic groups: eCU as triangles, aDS as circles, sDS as squares, uDS as crosses, and sAD as diamonds. Panels (D–F) and (G–I) show voxelwise (top) and ROI (bottom) analyses of the correlation between CBF and CSF Aβ1–42/Aβ1–40 ratio (D, G), CSF p‐tau181 (E, H), and hippocampal volume adjusted by TIV (F, I) in the entire population (D–F) and the non‐eCU group (G–I), respectively. Images are presented in neurological orientation and were generated using the SurfIce tool (top panel) or the ggseg R library (bottom panel). On top, the color scale indicates t values for both FWE‐corrected significance thresholds (p < 0.05, k > 500 mm³) and uncorrected thresholds (p < 0.005, k > 500 mm³). On the bottom, the color scale indicates the coefficient of determination (R ² values). For detailed statistical values, see Table S4 in supporting information. Aβ, amyloid beta; AD, Alzheimer's disease; aDS, asymptomatic Down syndrome; ATT, arterial transit time; CBF, cerebral blood flow; CSF, cerebrospinal fluid; eCU, euploid cognitively unimpaired; FWE, family wise error; GM, gray matter; ROI, region of interest; p‐tau, phosphorylated tau; sAD, sporadic Alzheimer's disease; sDS, symptomatic Down syndrome; TIV, total intracranial volume; uDS, uncertain Down syndrome.