Sensitivity comparison of multiple vs. single inversion time pulsed arterial spin labeling fMRI

Area of Science:

• Neuroimaging
• Functional Magnetic Resonance Imaging (fMRI)
• Physiology

Background:

• Pulsed arterial spin labeling (PASL) is a non-invasive MRI technique used to measure cerebral blood flow (CBF).
• Functional MRI (fMRI) detects brain activity by measuring changes in blood flow.
• Inversion time (TI) is a critical parameter in PASL that influences signal detection.

Purpose of the Study:

• To compare the sensitivity of multiple inversion time (TI) PASL versus single TI PASL for detecting brain activation.
• To evaluate the utility of multiple TI PASL in functional MRI (fMRI) studies.
• To investigate the impact of transit time changes on CBF quantification.

Main Methods:

• Five volunteers underwent visual stimulation (alternating checkerboard) during fMRI scans.
• Both multiple and single TI PASL sequences were employed using transfer insensitive labeling technique (TILT) and TURBO-TILT.
• The number of activated voxels and mean t-statistic were measured to assess activation detection sensitivity.

Main Results:

• Individual TI acquisitions within a multiple TI sequence showed lower sensitivity than single TI acquisitions of equal duration.
• Averaging data across all TIs (600-1400 msec) in the multiple TI sequence yielded comparable results to single TI acquisitions.
• Single TI PASL fMRI was found to overestimate CBF changes due to transit time variations.

Conclusions:

• Multiple TI PASL is suitable for fMRI when activation detection is performed on data averaged between 600 and 1400 msec.
• Averaged multi-TI PASL data allows for accurate quantification of cerebral blood flow (CBF) changes.
• Single TI PASL may lead to overestimation of CBF changes, highlighting the advantage of multi-TI approaches.