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

BACKGROUNDANDPURPOSE: 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.