Spatially-confined arterial spin-labeling with FAIR

Area of Science:

• Magnetic Resonance Imaging
• Medical Physics
• Physiology

Background:

• Pulsed arterial spin labeling (PASL) is a non-invasive MRI technique for measuring tissue perfusion.
• Large vessel signal contamination can compromise the accuracy of PASL-derived perfusion quantification.
• Body coil excitation is commonly used in PASL but can lead to significant inflow effects from large arteries.

Purpose of the Study:

• To evaluate the efficacy of slab-selective inversion in PASL using body coil excitation.
• To determine if this technique can effectively minimize signal contamination from large blood vessels.
• To compare spatially-confined tagging with conventional nonselective tagging.

Main Methods:

• Multislice flow-sensitive alternating inversion recovery (FAIR) sequences were employed on a 1.5-T MRI scanner.
• Tagging width was varied to achieve slab-selective inversion.
• Spatially-confined tagging was compared to nonselective tagging, with and without a bipolar gradient crusher, to assess vascular signal suppression.

Main Results:

• A 6-8 cm wide arterial blood bolus reached the capillary bed at a 1.4-second inversion time.
• Arterial blood flow velocities varied among subjects, averaging 10.1-13.9 cm/second.
• A 11.2-16.5 cm wide bolus entered the imaging region, highlighting the need for selective tagging.

Conclusions:

• Slab-selective tagging in FAIR perfusion imaging with body coil excitation is superior to nonselective tagging.
• This method effectively reduces residual tagged blood in large vessels, improving signal specificity.
• Spatially-confined tagging is recommended for more accurate perfusion measurements in PASL.