Perfusion Signal Analysis Using Multi-pulsed Arterial Spin Labeling (mPASL) with Multiple Post-labeling Delays: Phantom Validation and Application to the Human Foot.

Purpose: This study aims to extend the general kinetic model (GKM) for perfusion signal analysis using multi-pulsed arterial spin labeling (mPASL) acquisitions with multiple post-labeling delays (mPLD). The approach aims to improve accuracy and gain potential for broader experimental and clinical applications.

Methods: The magnetization vector evolution of the mPASL technique was analyzed using sequence diagrams and numerical simulation, supplemented by static phantom experiments. The GKM was adapted to support different configurations of mPASL tagging pulses in "dark" and "bright" methods. The proposed approach was validated on a constant-flow phantom and applied to in-vivo foot perfusion measurements in a cohort of 5 healthy subjects.

Results: Simulations showed that the ratio between "dark" and "bright" mPASL methods is determined by fluid T relaxation time, the number of selective pulses, and labeling efficiency. Experiments with a constant-flow phantom demonstrated that GKM with mPASL enables semi-quantitative perfusion analysis, providing high-temporal-resolution perfusion curves. Estimated perfusion coefficients of constant flow phantom were consistent across acquisitions (5.1% variation), confirming the robustness of the GKM extension for mPASL with multiple post-labeling delays. However, in-vivo results deviated from simulation and constant flow experiments, highlighting potential physiological complexities, and model limitations.

Conclusion: Extending the GKM to mPASL acquisitions demonstrates reliable performance under controlled constant flow conditions. Phantom experiments confirmed the accuracy of the approach, while in-vivo measurements in feet revealed deviations from simulation and constant flow results, suggesting the need to account for physiological factors and potential model extension due to pulsatile flow.