Study on the application of three-dimensional arterial spin labeling in diagnosis of viral encephalitis

Abstract

Objective To evaluate the role of three-dimensional arterial spin labeling (3D-ASL) in the diagnosis of viral encephalitis.  Methods MRI [T₁WI, T₂WI, diffusion-weighted imaging (DWI) and 3D-ASL] was performed in 41 patients with clinically diagnosed viral encephalitis, including 28 cases in acute phase and subacute phase with duration < 10 d and 13 cases in late subacute phase and chronic phase with duration ≥ 10 d. The positive outcomes of each MRI sequence for each patient were accounted and compared. The cerebral blood flow (CBF) and apparent diffusion coefficient (ADC) images were extracted from 3D-ASL imaging and regions of interest (ROIs) were selected. CBF and ADC values between ipsilateral side and contralateral side, between normal brain regions of ipsilateral side and contralateral side were compared respectively.  Results Among 41 cases, 28 (68.29% ) showed abnormalities: T₁WI hypointense signal in 3 cases, T₂WI hyperintense signal in 8 cases, DWI hyperintense signal in 14 patients, 3D-ASL hyperperfusion in 27 cases and hypoperfusion in one case. The positive rates for 3D-ASL [68.29% (28/41)] were significantly higher than that of T₁WI [7.32% (3/41); χ² = 32.416, P = 0.000], T₂WI [19.51% (8/41); χ² = 19.807, P = 0.000] and DWI [34.15% (14/41); χ² = 9.567, P = 0.004] respectively. CBF value of ipsilateral side in acute phase and subacute phase (< 10 d) was significantly higher than that of contralateral side [(83.61 ± 7.19) ml/(min·100 g) vs. (63.32 ± 4.83) ml/(min·100 g); t = 2.690, P = 0.012], while there was no significant difference in ADC value (P > 0.05). There was no significant difference for both CBF and ADC values in late subacute phase and chronic phase (≥ 10 d) between ipsilateral side and contralateral side (P > 0.05, for all). There was no significant difference for both CBF and ADC values between normal brain regions of ipsilateral side and contralateral side (P > 0.05, for all).  Conclusions The main manifestation of viral encephalitis in 3D-ASL imaging was hyperperfusion in the early stage. 3D-ASL is superior to conventional MRI sequences in detection of encephalitis lesion and may contribute to the diagnosis of early viral encephalitis in clinical practice.

DOI: 10.3969/j.issn.1672-6731.2018.03.006