Whole-cerebrum three-dimensional pseudo-continuous arterial spin labeling at 5T: reproducibility and preliminary application in moyamoya

Pseudo-continuous arterial spin labeling (PCASL) at 7T benefits from increased signal-to-noise ratio (SNR) and prolonged T1, but suffers from field inhomogeneities and increased specific absorption rate (SAR). We proposed that 5T magnetic resonance imaging (MRI) system may be a balanced choice for PCASL imaging. The aim of this study was to achieve whole-cerebrum PCASL imaging at ultra-high field 5T MRI system, assess the reproducibility and preliminarily explore its clinical application in moyamoya disease/syndrome. Twenty healthy volunteers were prospectively recruited for the reproducibility analysis. Both single-delay and multi-delay PCASL sequences were scanned twice on the 5T MRI scanner separated by a 10-minute period. Uncorrected cerebral blood flow (uCBF) from single-delay arterial spin labeling (ASL), corrected cerebral blood flow (cCBF) and arterial transit time (ATT) from multi-delay ASL were computed. The reproducibility of uCBF, cCBF and ATT were evaluated by calculating intraclass correlation coefficient (ICC), within-subject coefficient of variation (wsCV) and Pearson correlation coefficients between twice scans in grey matter regions and white matter (WM). Also, 26 patients diagnosed with moyamoya disease/syndrome were included and underwent multi-delay PCASL. The severity of intracranial arteries was graded as magnetic resonance angiography (MRA) score using time-of-flight (TOF) MRA. The relationship between MRA score and cCBF/ATT were assessed by one-way analysis of variance and Pearson correlation analysis. uCBF, cCBF and ATT showed excellent reliability in all regions with ICCs ranging from 0.856 to 0.962, wsCVs ranging from 2.39% to 6.76% and Pearson correlation coefficients ranging from 0.865 to 0.966. Multi-delay ASL demonstrated superior reproducibility of CBF quantification compared to single-delay ASL in regions with heterogeneous transit time, including WM, occipital lobe, limbic system and subcortical region. In patients with moyamoya disease/syndrome, those with higher anterior cerebral artery (ACA) or middle cerebral artery (MCA) scores exhibited lower cCBF (P<0.05). Correlation analysis showed that MRA score was negatively associated with cCBF (r=-0.540, P<0.001) and positively associated with ATT (r=0.515, P<0.001). Whole-cerebrum PCASL imaging at 5T ultra-high field was achieved with good reproducibility and applied well in patients with moyamoya disease/syndrome, which offers a promising tool in the assessment of hemodynamic conditions in cerebrovascular diseases.