title: [Flair and diffusion weighted MR imaging in differentiating epidermoid cysts from arachnoid cysts].
abstract: OBJECTIVE
  To explore the use of fluid-attenuated inversion recovery (FLAIR) and diffusion-weighted echo planar imaging sequences in imaging of the intracranial epidermoid and arachnoid cysts and assess the efficiency of those sequences in differentiation of epidermoid cysts from arachnoid cysts.
  
  
  METHODS
  This study was performed prospectively by using two different MR devices in 24 patients (12 epidermoid cysts, 12 arachnoid cysts). T1-weighted spin echo, T2-weighted fast spin echo, FLAIR and diffusion-weighted echo planar imaging sequences were used. Lesions were evaluated qualitatively and quantitatively. In qualitative evaluation, the signal intensity of the lesions were compared with cerebral spinal flow. Quantitative evaluation was made from the diffusion-weighted images by measuring values of apparent diffusion coefficient (ADC) from the cystic spaces and cerebral white matters. In statistic analyses, Mann-Whitney U test was used.
  
  
  RESULTS
  Arachnoid cysts had the same intensity with cerebral spinal flow in all sequences. Mean ADC value was 3.41 +/- 0.17 x 10(-3) mm2/sn. All epidermoid cysts on diffusion-weighted trace images were more hyperintense than brain parenchyma. The mean ADC value of the epidermoid cysts was 1.15 +/- 10(-3) mm2/sn. The ADC values of the epidermoid cysts were lower than the arachnoid cysts (p < 0.001), but were higher than the cerebral white matter (p < 0.01).
  
  
  CONCLUSIONS
  FLAIR sequences were superior to conventional sequences in imaging of epidermoid cysts and in differentiation of epidermoid cysts from arachnoid cysts. It was also shown that diffusion-weighted trace imaging and measurement of ADC values might be used as problem solving tools. Furthermore, those sequences may be a guide to demonstrate postoperative residual lesions.
authors.affiliation: Uludağ Universitesi Tip Fakültesi, Radyoloji Anabilim Dali, Bursa.
authors.forename: Bahattin
authors.initials: B
authors.lastname: Hakyemez
authors.forename: Harun
authors.initials: H
authors.lastname: Yildiz
authors.forename: Necdet
authors.initials: N
authors.lastname: Ergin
authors.forename: Sait
authors.initials: S
authors.lastname: Uysal
authors.forename: Müfit
authors.initials: M
authors.lastname: Parlak
mesh_terms: D000293:Adolescent; D000328:Adult; D016080:Arachnoid Cysts / Q000175:diagnosis* / Q000473:pathology; D001927:Brain Diseases / Q000175:diagnosis* / Q000473:pathology; D002648:Child; D003937:Diagnosis, Differential; D004814:Epidermal Cyst / Q000175:diagnosis* / Q000473:pathology; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000295:instrumentation / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000295:instrumentation* / Q000379:methods; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies