Quantitative Transport Mapping Derived Tracer Velocity for Alzheimer’s Disease

Abstract

AbstractBackgroundThe Alzheimer’s disease (AD), featured with extracellular beta‐amyloid plaque and intracellular tau tangles, are considered caused by the brain clearance function deficits. One anatomical representation of the fluid stasis is the enlargement of the perivascular space. Our hypothesis is that the fluid stasis will reduce the fluid velocity, and the reduced fluid velocity will drive the PET tracer slower than normal. We used the velocity map from our proposed quantitative transport mapping (QTM, L. Zhou MRM 2020.) to evaluate the PET tracer velocity in Alzheimer’s disease.MethodFifty‐seven subjects (age: 69.7±9.1, Female/male = 37/20, NL/MCI = 45/12) went through both 11C‐PIB and 18F‐MK‐6240 PET scan for Aβ and tau deposit measurements, and MRI scan for ROI parcellation. PIB SUVR, MK vCSF‐Slope (Y. Li Fluids Barriers CNS 2022), MK QTM are processed for the following analysis. Specifically, vCSF‐Slope was computed as the tracer turnover rate in lateral ventricle using the dynamic MK data between 10 to 30min, normalized by the whole brain AUC in 1 to 4min. QTM velocity was processed using the dynamic MK data between 40 to 55min using mass conservation equation. Regression model for predicting Aβ using QTM was conducted by controlling for age and sex. The relationship between QTM and vCSF was evaluated. The use of QTM to distinguish subjects groups are tested.ResultOur preliminary results showed that quantitative transport mapping(QTM) based on fluid mechanics is significantly associate the ventricular CSF clearance(vCSF) measured by dynamic PET data and brain amyloid(PiB PET). The regression model shows that cerebral cortex (GM) QTM velocity (p<0.01, t = ‐2.76) and age (p<0.05, t = 2.55) are significantly associated with the GM PIB SUVR as shown in Figure 1. This indicates that high Aβ deposit is associated with lower QTM velocity, i.e., clearance deficits. Figure 2 shows that in GM QTM velocity is correlated with the vCSF‐Slope (p<0.05, r = 0.37). Figure 3 shows that QTM velocity in both GM and lateral ventricle are able to distinguish normal and MCI/AD groups.ConclusionThe tracer velocity in the brain tissue measured by QTM is associated with ventricular CSF turnover rate and brain amyloid burden. Acknowledgement: This study is supported by NIA grant AG057848