Comparison of PASL, PCASL, and background-suppressed 3D PCASL in mild cognitive impairment

Abstract

We compared three implementations of single-shot arterial spin labeled (ASL) perfusion magnetic resonance imaging: two-dimensional (2D) pulsed ASL (PASL), 2D pseudocontinuous ASL (PCASL), and background-suppressed (BS) 3D PCASL obtained in a cohort of patients with mild cognitive impairment (MCI) and elderly controls. Study subjects also underwent ¹⁸ F-fluorodeoxyglucose positron emission tomography (¹⁸ F-FDG PET). While BS 3D PCASL showed the lowest (P < 0.001) gray matter-white matter cerebral blood flow (CBF) contrast ratio, it provided the highest (P < 0.001) temporal signal-to-noise ratio. Mean relative CBF estimated using the PCASL methods in posterior cingulate cortex (PCC), precuneus, and hippocampus showed hypoperfusion in the MCI cohort compared to the controls consistent with hypometabolism measured by ¹⁸ F-FDG PET. BS 3D PCASL demonstrated the highest discrimination between controls and patients with effect size comparable to that seen with ¹⁸ F-FDG PET. 2D PASL did not demonstrate group differentiation with relative CBF in any ROI, whereas 2D PCASL demonstrated significant differences only in PCC and hippocampus. Mean global CBF values did not differ across methods and were highly correlated; however, the correlations were significantly higher (P < 0.001) when either the same labeling (PCASL) or the same acquisition strategy (2D) was used as compared to when both the labeling and readout methods differed. In addition, there were differences in regional distribution of CBF between the three modalities, which can be attributed to differences in sequence parameters. These results demonstrate the superiority of ASL with PCASL and BS 3D readout as a biomarker for regional brain function changes in MCI. Hum Brain Mapp 38:5260-5273, 2017. © 2017 Wiley Periodicals, Inc.

Keywords: 3D spiral acquisition; background suppression; mild cognitive impairment; positron emission tomography; pseudocontinuous ASL; pulsed ASL.

Figure 1

Triaxial view of mean CBF maps using 2D PASL (Row 1), 2D PCASL (Row 2), and BS 3D PCASL (Row 3) of a representative control subject on the left and MCI patient on the right. The bottom row shows the SUVR maps of the same subjects. [Color figure can be viewed at http://wileyonlinelibrary.com]

Figure 2

Bland–Altman plots comparing the global CBF measurements obtained using (top) 2D PASL and 2D PCASL, (middle) 2D PCASL and BS 3D PCASL, and (bottom) 2D PASL and BS 3D PCASL. The three lines in each case show the mean difference and the 95% confidence intervals.

Figure 3

Difference in relative CBF in control subjects between (left) 2D PASL and 2D PCASL, (middle) 2D PCASL and BS 3D PCASL, and (right) 2D PASL and BS 3D PCASL. [Color figure can be viewed at http://wileyonlinelibrary.com]

Figure 4

Triaxial view of (left to right) average CBF maps of the controls, patients, and their differences for 2D PASL (Row 1), 2D PCASL (Row 2), and BS 3D PCASL (Row 3). The bottom row shows the average SUVR maps of the controls, patients, and their differences (left to right). [Color figure can be viewed at http://wileyonlinelibrary.com]

Figure 5

Box plots of mean relative CBFs and mean SUVR in different ROIs shown in blue for controls and red for MCI patients. Within each box, the three horizontal lines represent the first quartile, the median, and the third quartile (bottom to top). The two horizontal lines outside each box represent the minimum and maximum values ignoring outliers. Outliers, determined as 1.5 times the interquartile range above (or below) the third (or first) quartile, are shown separately with “+” symbols. [Color figure can be viewed at http://wileyonlinelibrary.com]