Multi-delay arterial spin labeling perfusion MRI in moyamoya disease--comparison with CT perfusion imaging

Abstract

Objectives: To present a multi-delay pseudo-continuous ASL (pCASL) protocol that offers simultaneous measurements of cerebral blood flow (CBF) and arterial transit time (ATT), and to study correlations between multi-delay pCASL and CT perfusion in moyamoya disease.

Methods: A 4 post-labeling delay (PLD) pCASL protocol was applied on 17 patients with moyamoya disease who also underwent CT perfusion imaging. ATT was estimated using the multi-delay protocol and included in the calculation of CBF. ASL and CT perfusion images were rated for lesion severity/conspicuity. Pearson correlation coefficients were calculated across voxels between the two modalities in grey and white matter of each subject respectively and between normalized mean values of ASL and CT perfusion measures in major vascular territories.

Results: Significant associations between ASL and CT perfusion were detected using subjective ratings, voxel-wise analysis in grey and white matter and region of interest (ROI)-based analysis of normalized mean perfusion. The correlation between ASL CBF and CT perfusion was improved using the multi-delay pCASL protocol compared to CBF acquired at a single PLD of 2 s (P < 0.05).

Conclusions: There is a correlation between perfusion data from ASL and CT perfusion imaging in patients with moyamoya disease. Multi-delay ASL can improve CBF quantification, which could be a prognostic imaging biomarker in patients with moyamoya disease.

Key points: • Simultaneous measurements of CBF and ATT can be achieved using multi-delay pCASL. • Multi-delay ASL was compared with CT perfusion in patients with moyamoya disease. • Statistical analyses showed significant associations between multi-delay ASL and CT perfusion. • Multi-delay ASL can improve CBF quantification in moyamoya disease.

Figures

Figure 1

Diagram of the data processing steps to simultaneously obtain ATT and CBF images using the multi-delay pCASL protocol in a 25-year-old female patient with moyamoya disease with low perfusion in the left frontal and occipital lobes. CBF at each PLD is calculated using the measured ATT map and Eq. (2). The final CBF was the average of the estimated CBF at 4 PLDs.

Figure 2

A: Imaging coverage of CT perfusion and pCASL. B: Perfusion maps generated from CTP (a) and ASL (b–f) in 31-year-old man with episodes of dizziness and blurred vision for six months. CTP CBF (a) and ASL CBF (b) show hypoperfusion in the right frontal, occipital, temporal-parietal lobes. CTP MTT (a) and ASL ATT (b) were prolonged with hypoperfusion on CBF images. However, ATT is not or only slightly prolonged in the right posterior portion with extremely low CBF. Abnormal perfusion was also observed in ASL perfusion images in superior slices (c–f) that were not covered in CT perfusion.

Figure 3

Representative moyamoya case with multi-parametric CTP and ASL images. A 24-year-old man with 6 months of transient headache and weakness in the left limb. The time interval between pre-operative CT perfusion and pCASL was 1 day. CTP shows low perfusion areas in the right temporal-parietal lobe with decreased CBF values, elevated MTT and relatively stable CBV. ASL is in concordance with the result of CTP.

Figure 4

Scatterplots and Pearson correlation coefficients between normalized average values of ASL and CTP in major vascular territories of all 17 scans (*P < 0.05, P<0.005).

Figure 5

a From left to right: pCASL CBF images for PLD of 1500, 2000, 2500, 3000 ms. b ASL CBF2000, CBFmean, and ATT and images of the same slice in a 32-year-old female patient with moymoya disease. PCASL with short PLD perfusion maps showed enlarged abnormal perfusion territory (arrows) in bilateral frontal-temporal lobe with prolonged ATT, while the problem is mitigated in perfusion images with long PLDs and in CBFmean image.

Figure 6

A 48-year-old man with a history of paroxysmal weakness in the right limb for 15 years. CTP shows perfusion deficit in bilateral temporal-parietal lobe, posterior of basal ganglia and coronal radiate with decreased CBF values, elevated MTT and slightly increased CBV. ASL perfusion images show almost same perfusion changes as CTP. However, ASL CBF and aCBV shows hypoperfusion with delayed transit effects in the left parietal lobe (arrows).