title: Diffusion-weighted MR imaging of viral encephalitis.
abstract: BACKGROUND
  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 T1-W, T2-W and fluid attenuated inversion recovery (FLAIR) sequences and DWI in 18 patients with viral encephalitis diagnosed on the basis of laboratory, clinical and radiologic findings. 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. The degree of correlation between the time (TI) from the onset of neurologic symptoms to the MR examination and ADC values was determined.
  
  
  RESULTS
  In group I (n=11) 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=4) DWI was similar to conventional MRI. In group III (n=3) conventional MRI was superior to DWI. Mean ADC values of affected versus contralateral normal brain tissues were 0.458+/-0.161 x 10(-3) versus 0.86+/-0.08 x 10(-3) in group I, 0.670+/-0.142 x 10(-3) versus 0.93+/-0.07 x 10(-3) in group II, and 1.413+/-0.211 x 10(-3) versus 1.05+/-0.06 x 10(-3) 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).
  
  
  CONCLUSIONS
  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 contribute to the determination of the disease phase.
authors.affiliation: Department of Radiology, Pamukkale University School of Medicine, TR-20070 Denizli, Turkey. drkiroglu@yahoo.com
authors.forename: Yilmaz
authors.initials: Y
authors.lastname: Kiroğlu
authors.forename: Cem
authors.initials: C
authors.lastname: Calli
authors.forename: Nilgun
authors.initials: N
authors.lastname: Yunten
authors.forename: Omer
authors.initials: O
authors.lastname: Kitis
authors.forename: Ayse
authors.initials: A
authors.lastname: Kocaman
authors.forename: Nevzat
authors.initials: N
authors.lastname: Karabulut
authors.forename: Hasan
authors.initials: H
authors.lastname: Isaev
authors.forename: Baki
authors.initials: B
authors.lastname: Yagci
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D018792:Encephalitis, Viral / Q000175:diagnosis*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D018709:Statistics, Nonparametric