Test-Retest Reliability of Arterial Spin Labeling With Common Labeling Strategies

Purpose: To compare the test-retest reproducibility of three variants of arterial spin labeling (ASL): pseudo-continuous (pCASL), pulsed (PASL) and continuous (CASL). Materials and Methods: Twelve healthy subjects were scanned on a 3.0T scanner with PASL, CASL, and pCASL. Scans were repeated within-session, after 1 hour, and after 1 week to assess reproducibility at different scan intervals. Results: Comparison of within-subject coefficients of variation (wsCV) demonstrated high within-session reproducibility (ie, low wsCV) for CASL-based methods (gray matter [GM] wsCV for pCASL: 3.5% +/- 0.02%, CASL: 4.1% +/- 0.07%) compared to PASL (wsCV: 7.5% +/- 0.06%), due to the higher signal-to-noise ratio (SNR) associated with continuous labeling, evident in the 20% gain in temporal SNR and 58% gain in raw SNR for pCASL relative to PASL. At the 1-week scan interval, comparable reproducibility between PASL (GM wsCV 9.2% +/- 0.12%) and pCASL (GM wsCV 8.5% +/- 0.14%) was observed, indicating the dominance of physiological fluctuations. Conclusion: Although all three approaches are capable of measuring cerebral blood flow within a few minutes of scanning, the high precision and SNR of pCASL, with its insensitivity to vessel geometry, make it an appealing method for future ASL application studies.