Arterial Spin-Labeling Parameters Influence Signal Variability and Estimated Regional Relative Cerebral Blood Flow in Normal Aging and Mild Cognitive Impairment: FAIR versus PICORE Techniques

BACKGROUND AND PURPOSE: Arterial spin-labeling is a noninvasive method to map cerebral blood flow, which might be useful for early diagnosis of neurodegenerative diseases. We directly compared 2 arterial spin-labeling techniques in healthy elderly controls and individuals with mild cognitive impairment. MATERIALS AND METHODS: This prospective study was approved by the local ethics committee and included 198 consecutive healthy controls (mean age, 73.65 +/- 4.02 years) and 43 subjects with mild cognitive impairment (mean age, 73.38 +/- 5.85 years). Two pulsed arterial spin-labeling sequences were performed at 3T: proximal inversion with a control for off-resonance effects (PICORE) and flow-sensitive alternating inversion recovery technique (FAIR). Relative cerebral blood flow maps were calculated by using commercial software and standard parameters. Data analysis included spatial normalization of gray matter-corrected relative CBF maps, whole-brain average, and voxelwise comparison of both arterial spin-labeling sequences. RESULTS: Overall, FAIR yielded higher relative CBF values compared with PICORE (controls, 32.7 +/- 7.1 versus 30.0 +/- 13.1 mL/min/100 g, P = .05; mild cognitive impairment, 29.8 +/- 5.4 versus 26.2 +/- 8.6 mL/min/100 g, P < .05; all, 32.2 +/- 6.8 versus 29.3 +/- 12.3 mL/min/100 g, P < .05). FAIR had lower variability (controls, 36.2% versus 68.8%, P < .00001; mild cognitive impairment, 18.9% versus 22.9%, P < .0001; all, 34.4% versus 64.9% P < .00001). The detailed voxelwise analysis revealed a higher signal for FAIR, notably in both convexities, while PICORE had higher signal predominantly in deep cerebral regions. CONCLUSIONS: Overall, FAIR had higher estimated relative CBF and lower interindividual variability than PICORE. In more detail, there were regional differences between both arterial spin-labeling sequences. In summary, these results highlight the need to calibrate arterial spin-labeling sequences.