The role of diffusion-weighted MR imaging in viral encephalitis of children.

Objective The aim of this study was to evaluate the role of diffusion-weighted imaging(DWI)in the diagnosis of viral encephalitis and its relationship with the stage of the illness.Methods We performed conventional magnetic resonance imaging(MRI)including T1WI,T2WI sequences and DWI in 56 patients with viral encephalitis diagnosed on the basis of laboratory,clinical and radiologic findings,in which 29 patients were abnormal.Thirteen patients have received MRI two times.So,there were 42 case-times of abnormal MRI.Based on the qualitative and quantitative comparison of the conventional MRI and DWI,the patients were divided into three groups.Apparent diffusion coefficient(ADC)values of the involved and contralateral normal brain tissues were computed and compared for each group.Results In group Ⅰ(n = 23)DWI was superior to conventional MRI in detecting the encephalitic involved sites and in depicting the borders of the encephalitic lesions.In group Ⅱ(n = 11)DWI was similar to conventional MRI.In group Ⅲ(n = 8)conventional MRI was superior to DWI.Mean ADC values of affected versus contralateral normal brain tissues were 0.45±0.19×10-3 mm2/sVS 0.93±0.06×10-3 mm2/s in group Ⅰ,0.87±0.31× 103 mm2/s VS 0.97±0.06×10-3 mm2/s in group Ⅱ,and 1.66±0.60×10-3 mm2/s VS 1.08±0.24×10-3 mm2/s in group Ⅲ.Patients in group Ⅰ had significantly lower ADC values than those in group Ⅱ,while patients in group Ⅲ had the highest ADC values(P 0.05).The ADC values were significantly lower in the affected sites than in the unaffected sites of patients in groups I and Ⅱ,but were significantly higher in the affected sites than in the unaffected sites of patients in group Ⅲ(P 0.05).There was an excellent correlation between ADC values and duration of the disease(r = 0.874,P = 0.01).Conclusion DWI is superior to other conventional diagnostic MR sequences in the detection of early viral encephalitic lesions and depiction of the lesion borders and,in combination with other sequences,DWI may contributeto the determination of the disease phase.