VESPA ASL: VElocity and SPAtially Selective Arterial Spin Labeling

Area of Science:

• Medical Imaging
• Neuroimaging
• Cardiovascular Imaging

Background:

• Arterial spin labeling (ASL) perfusion MRI accuracy is limited by arterial transit times (ATT).
• Velocity-selective ASL improves robustness to ATT but cannot measure it.
• Accurate measurement of cerebral blood flow (CBF) and ATT is clinically important for vascular diseases.

Purpose of the Study:

• Introduce VESPA ASL, a novel pulse sequence combining velocity-selective and pseudo-continuous ASL.
• Enable simultaneous and robust measurement of CBF and ATT.
• Address limitations of existing ASL techniques in the presence of long ATTs.

Main Methods:

• Developed the VESPA ASL sequence, integrating spatially selective velocity-labeling with pseudo-continuous ASL.
• Optimized sequence parameters, including inflow time.
• Validated VESPA ASL against multi-delay pseudo-continuous ASL and velocity-selective ASL using simulations and in vivo test-retest studies in healthy volunteers.

Main Results:

• VESPA ASL accurately quantifies CBF even with prolonged ATTs.
• The technique can measure ATTs shorter than the inversion time (TI).
• Compared to multi-delay pseudo-continuous ASL, VESPA ASL provided more accurate CBF measurements when ATT was long, avoiding underestimation.

Conclusions:

• VESPA ASL is a robust and novel method for simultaneous CBF and ATT measurement.
• This technique offers significant advantages over existing ASL methods.
• Fulfills a critical clinical need for noninvasive perfusion and transit time imaging in conditions with delayed arterial transit.