Optimization of post-label delay in single-phase arterial spin labeling (ASL) using multi-phase ASL in four-dimensional magnetic resonance angiography

Purpose: To optimize the post-label delay in single-phase arterial spin labeling (SP-ASL) using multi-phase ASL in 4-dimensional magnetic resonance angiography (4D-MRA). Methods: Ten healthy volunteers (six men, four women; age range, 24–37 years; mean, 29.1) were enrolled. 4D-MRA and SP-ASL were performed on a 3T magnetic resonance imaging (MRI) scanner. Signal intensities in four cerebral arterial territories (anterior cerebral artery, middle cerebral artery, posterior cerebral artery, and whole area) were measured using both 4D-MRA and SP-ASL, and peak time of maximum intensity through each technique was recorded. Regression analysis was used to determine the correlation between the peak times using 4D-MRA and those using SP-ASL, and the regression function obtained was used to estimate the peak time for SP-ASL (optimum post-label delay) from that obtained for 4D-MRA. Results: The peak time in anterior cerebral artery territory for SP-ASL was expressed as 1.19 + 0.30 × (peak time of 4D-MRA) s, (p = 0.017, r² = 0.14). The peak time in middle cerebral artery territory for SP-ASL was 0.96 + 0.58 × (peak time of 4D-MRA) s, (p < 0.001, r² = 0.32). The peak time in posterior cerebral artery territory for SP-ASL was expressed as 0.92 + 0.58 × (peak time of 4D-MRA) s, (p < 0.001, r² = 0.33). The peak time in whole brain for SP-ASL was expressed as 1.04 + 0.46 × (peak time of 4D-MRA) s, (p < 0.001, r² = 0.25). Conclusion: The peak time values at 4D-MRA showed potential for use in predicting the optimum post-label delay of SP-ASL.