title: Diffusion-weighted MRI in the characterization of pleural effusions.
abstract: OBJECTIVE
  To evaluate the value of diffusion-weighted imaging (DWI) in the differential diagnosis of pleural effusions.
  
  
  METHODS
  58 pleural effusions (21 transudative, 37 exudative) were included in this prospective study. Single-shot echo-planar spin echo DWI was performed with two b factors (500 and 1000 s/mm (2)), and apparent diffusion coefficients (ADCs) were calculated. On diffusion- weighted (DW) trace images, signal intensity (SI) of the pleural effusions was visually compared to the SI of the paraspinal muscles with the use of a 3-point scale: 0: isointense, 1: moderately hyperintense, 2: significantly hyperintense. For quantitative evaluation, effusion- to-paraspinal muscle SI ratios, and ADCs of the effusions were compared between the groups.
  
  
  RESULTS
  On visual evaluation, most of the transudative effusions were isointense, while most of the exudative effusions were hyperintense on DWI with b factors of 500 and 1000 s/mm (2). Quantitatively, with a b factor of 500 and 1000 s/mm(2), effusion-to-paraspinal muscle SI ratios of the exudative effusions were significantly higher than those of transudative effusions. The ADCs of the exudative effusions were significantly lower than those of transudative effusions (mean ADC was 3.3 x 10 (-3)+/- 0.7 mm(2)/s for exudative effusions, and 3.7 x 10 (-3)+/-0.3 mm(2)/s for transudative effusions). Setting the cutoff value at 3.6 x 10(-3), ADC had a sensitivity of 71% and a specificity of 63% for differentiating transudative from exudative effusions.
  
  
  CONCLUSIONS
  DWI may help in the differential diagnosis of pleural effusions.
authors.affiliation: Department of Radiology, Kocaeli University School of Medicine, Kocaeli, Turkey. inannagihan@ekolay.net
authors.forename: Nagihan
authors.initials: N
authors.lastname: Inan
authors.forename: Arzu
authors.initials: A
authors.lastname: Arslan
authors.forename: Gür
authors.initials: G
authors.lastname: Akansel
authors.forename: Zeliha
authors.initials: Z
authors.lastname: Arslan
authors.forename: Levent
authors.initials: L
authors.lastname: Elemen
authors.forename: Levent
authors.initials: L
authors.lastname: Eleman
authors.forename: Ali
authors.initials: A
authors.lastname: Demirci
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010994:Pleura / Q000473:pathology; D010996:Pleural Effusion / Q000175:diagnosis* / Q000209:etiology / Q000473:pathology; D011446:Prospective Studies; D012372:ROC Curve; D012680:Sensitivity and Specificity; D055815:Young Adult