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.

Key words: Encephalitis, viral, Magnetic resonance imaging, Electron spin resonance spectroscopy

摘要：

目的 探讨三维动脉自旋标记（3D-ASL）对病毒性脑炎的诊断价值。方法 共41 例病毒性脑炎患者［急性期和亚急性早期（< 10 d）28 例，亚急性晚期和慢性期（≥ 10 d）13 例］行头部MRI 检查，包括T₁WI、T₂WI、扩散加权成像（DWI）和3D-ASL，计算并比较各序列阳性率；对3D-ASL 图像进行处理获得脑血流量（CBF）图和表观扩散系数（ADC）图并选取兴趣区，比较病灶侧与镜像侧CBF 值和ADC 值，以及病灶所在脑区外脑叶患侧与健侧额颞顶枕叶和小脑CBF 值和ADC 值。结果 41 例患者中28 例（68.29%）呈异常表现，3 例T₁WI 呈低信号，8 例T₂WI 呈高信号，14 例DWI 呈高信号，27 例3D-ASL 呈病灶高灌注、1 例呈病灶低灌注。3D-ASL 阳性率［68.29%（28/41）］高于T₁WI［7.32%（3/41）；χ² = 32.416，P = 0.000］、T₂WI［19.51%（8/41）；χ² = 19.807，P = 0.000］和DWI［34.15%（14/41）；χ² = 9.567，P = 0.004］。急性期和亚急性早期（< 10 d）病灶侧CBF 值高于镜像侧且差异有统计学意义［（83.61 ± 7.19）ml/（min·100 g）对（63.32 ± 4.83）ml/（min·100 g）；t = 2.690，P = 0.012］，而双侧ADC 值差异无统计学意义（P > 0.05）；亚急性晚期和慢性期（≥ 10 d）病灶侧与镜像侧CBF 值和ADC 值差异均无统计学意义（P > 0.05）。病灶所在脑区外脑叶比较，患侧与健侧额颞顶枕叶和小脑CBF 值和ADC 值差异均无统计学意义（P > 0.05）。结论 病毒性脑炎早期3D-ASL 即呈现病灶高灌注，且3D-ASL 诊断病毒性脑炎的阳性率高于其他MRI 序列，故可以作为病毒性脑炎的重要辅助诊断工具。

关键词: 脑炎, 病毒性, 磁共振成像, 电子自旋共振谱学