Perfusion Signal Analysis Using Multi-pulsed Arterial Spin Labeling (mPASL) with Multiple Post-labeling Delays:...

Area of Science:

• Magnetic Resonance Imaging
• Biomedical Engineering
• Physiology

Background:

• Accurate perfusion quantification is crucial for diagnosing and monitoring various medical conditions.
• Arterial spin labeling (ASL) is a non-invasive MRI technique for measuring tissue perfusion.
• Multi-pulsed ASL (mPASL) offers potential advantages in signal-to-noise ratio and temporal resolution.

Purpose of the Study:

• To extend the general kinetic model (GKM) for perfusion signal analysis.
• To adapt GKM for multi-pulsed arterial spin labeling (mPASL) with multiple post-labeling delays (mPLD).
• To enhance accuracy and applicability of mPASL in experimental and clinical settings.

Main Methods:

• Analyzed mPASL magnetization vector evolution using sequence diagrams and numerical simulation.
• Adapted GKM for "dark" and "bright" mPASL configurations.
• Validated the approach using constant-flow phantom experiments and in-vivo foot perfusion measurements in healthy subjects.

Main Results:

• Simulations revealed "dark"/"bright" mPASL ratio depends on fluid T1 relaxation, pulse number, and labeling efficiency.
• GKM with mPASL enabled semi-quantitative perfusion analysis with high temporal resolution in phantoms.
• Phantom perfusion coefficients showed high consistency (5.1% variation), confirming GKM extension robustness.
• In-vivo results deviated from simulations and phantom data, indicating physiological complexities and model limitations.

Conclusions:

• The extended GKM for mPASL demonstrates reliable performance in controlled constant flow conditions.
• Phantom validation confirmed the accuracy of the GKM extension for mPASL.
• In-vivo foot perfusion measurements highlighted deviations, suggesting the need to incorporate physiological factors and pulsatile flow into the model.