Evaluation Of ADC Values In The Early Diagnosis Of Children With Viral Encephalitis

Purpose:The objective of the study was to evaluate the role of apparent diffusion coefficient(ADC)values in the early diagnosis of viral encephalitis in children.And to discuss the rule of the ADC values and CNR.Methods:34 children with viral encephalitis were studied from 2005 to 2007,age range 2 months to 14 years,mean age 51.6 months.The time from the onset of neurologic symptoms to the MR examination were 10 hours to 33 days.There are 8 patients with contrast examination,5 patients with MRA,and 4 patients with examination some days later too.We performed conventional magnetic resonance imaging(MRI)including T1WI, T2WI and fluid attenuated inversion recovery(FLAIR)sequences and DWI(b=1000s/mm²)in the encephalitis group.Another 34 patients from the control group(age similar to study group,without any MR unnormal)also received the same examination.Based on the qualitative and quantitative comparison of the conventional MRI and DWI,the patients were divided into three groups.Apparent diffusion coefficient values of the involved and normal brain tissues were computed and compared for each group.And The absolute values of CNRs of the involved brain tissues were computed and compared for each serie.The degree of correlation between the time from the onset of neurologic symptoms to the MR examination and ADC values was determined.Statistical analysis were made by SPSS11.5.Results:â‘ In groupâ… (n=10)DWI was superior to conventional MRI in showing the encephalitic involved sites,and the interval time of the illness was(3.1±1.4)days;In groupâ…¡(n=9)DWI was similar to conventional MRI,time was(5.6±1.9)day;In groupâ…¢(n=15)conventional MRI was superior to DWI,time was(15.3±7.7)days. Mean ADC values of affected and normal brain tissues were(61.8±15.6×10^-5) mm²/s,(89.7±11.6×10^-5)mm²/s in groupâ… ;(85.2±11.5×10^-5)mm²/s,(84.6±5.8×10^-5)mm²/s in groupâ…¡;(119.9±11.3×10^-5)mm²/s,(85.6±5.2×10^-5) mm²/s in groupâ…¢.Patients in groupâ… had significantly lower ADC values than those in groupâ…¡(P＜0.05),while patients in groupâ…¢had the highest ADC values(P＜0.05). The ADC values were significantly lower in the study sites than in the control sites in groupsâ… ,but were significantly higher in the study sites than in the control sites of patients in groupâ…¢(P＜0.05).The study sites of the ADC values in groupâ…¡were not significantly different from the control sites.In groupâ… ,The absolue CNRs on DW images were significantly higher than those on T1W,T2W and FLAIR images(P＜0.01);In groupâ…¡,absolute CNRs on DW images have no significantly different from those on other imges(P＞0.05);however,lesions on DW images in groupâ…¢have significantly lower CNRs than on T2W(P=0.022＜0.05),but have no significantly different from those on T1W and FLAIR images(P＞0.05).â‘¡There was a linear correlation between ADC values of viral encephalitis in children and the interval time of the illness(r_s=0.820,p＜0.001).â‘¢There was a negative correlation between ADC values of viral encephalitis in children and age,but no statistically significant difference was among study sites (r=-0.464,P=0.006＜0.05)in control group.Conclusion:The apparent diffusion coefficient decreased in the early stage of viral encephalitis in children and increased with the duration of the disease.The absolue CNRs on DW images were significantly higher than those on T1W,T2W and FLAIR images in the early stage of viral encephalitis in children and lower than T2WI with the duration of the disease.Diffusion-weighted images and ADC values had an important role in the early diagnosis of viral encephalitis in children.