3D Whole-Brain Perfusion Quantification using Pseudo-ContinuousArterial Spin Labeling MRI at Multiple Post-Labeling Delays: Accounting for BothArterial Transit Time and Impulse Response Function

摘要

Measurement of cerebral blood flow (CBF) with whole-brain coverage is challenging in terms of both acquisition and quantitative analysis. In order to fit the ASL-based perfusion kinetic curves, an empirical 3-parameter model that characterizes the effective impulse response function (IRF) is introduced, which allows determination of CBF, arterial transit time (ATT), and T1,eff. The accuracy and precision of the proposed model is compared with more complicated models with 4 or 5 parameters through Monte Carlo simulations. Pseudo-continuous arterial spin labeling (PCASL) images were acquired on a clinical 3 Tesla scanner in 10 normal volunteers using a 3D multi-shot gradient- and spin-echo (GRASE) scheme at multiple post-labeling delays to sample the kinetic curves. Voxel-wise fitting was performed using the 3-parameter model and other models that contain 2, 4 or 5 unknown parameters. For the 2-parameter model, T1,eff values close to tissue and blood were assumed separately. Standard statistical analysis was conducted to compare these fitting models in various brain regions. The fitted results indicate that: 1) the estimated CBF values using the 2-parameter model show appreciable dependence on the assumed T1,eff values; 2) the proposed 3-parameter model achievesthe optimal balance between the goodness of fit and the model complexity whencompared among the models with explicit IRF fitting; 3) both the 2-parametermodel using fixed blood T1 values for T1,eff and the3-parameter model provide reasonable fitting results. Using the proposed3-parameter model, the estimated CBF values (46±14 mL/100g/min) and ATTvalues (ATT = 1.4±0.3 s) averaged from different brain regionsare close to the literature reports; the estimated T1,eff values(T1,eff = 1.9±0.4 s) are higher than the tissueT1 values, possibly reflecting a contribution from themicrovascular arterial blood compartment.