title: Diffusion-weighted imaging in the differential diagnosis of simple and hydatid cysts of the liver.
abstract: OBJECTIVE
  The purpose of our study was to evaluate the value of diffusion-weighted imaging (DWI) in the differential diagnosis of simple and hydatid cysts of the liver, particularly in the completely liquid type of hydatid cyst.
  
  
  METHODS
  Eighty-two cysts (43 simple cysts, 39 hydatid cysts) were included in this prospective study. DWI was performed using a breath-hold single-shot echo-planar spin-echo sequence, and apparent diffusion coefficients (ADCs) were calculated. On DW trace images, the signal intensity of cysts was visually compared with the signal intensity of the liver using a 3-point scale: 0, isointense; 1, moderately hyperintense; and 2, significantly hyperintense. Quantitatively, signal intensity of the cysts, cyst-to-liver signal intensity ratios, ADC of the cysts, and cyst-to-liver ADC ratios were compared between the groups. The statistical significance was determined using the Mann-Whitney U test.
  
  
  RESULTS
  On trace DWI (b = 1,000 s/mm2), most hydatid cysts (37/39, 95%) were hyperintense, whereas most simple cysts (40/43, 93%) were isointense with the liver. Three simple cysts (7%) were moderately hyperintense and two hydatid cysts (5%) were isointense. Quantitatively, both the signal intensity and cyst-to-liver signal intensity ratio of the hydatid cysts were significantly higher than those for simple cysts (p < 0.001). The cutoff value at 1.5 yielded a sensitivity of 77%, a specificity of 86%, and positive predictive value of 83% for the cyst-to-liver signal intensity ratio. The ADC and cyst-to-liver ADC ratio of the hydatid cysts were significantly lower than those of simple cysts (p < 0.005). For the completely liquid type in particular, we observed statistically significant differences in signal intensity, signal intensity ratio, ADC, and ADC ratios from those of simple cysts (p < 0.005). With a cutoff value of 1.5, signal intensity ratio had a sensitivity of 81%, specificity of 86%, and positive predictive value of 74%.
  
  
  CONCLUSIONS
  DWI may help in the differential diagnosis of hydatid and simple cysts of the liver.
authors.affiliation: Department of Radiology, School of Medicine, University of Kocaeli, 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: Gur
authors.initials: G
authors.lastname: Akansel
authors.forename: Yonca
authors.initials: Y
authors.lastname: Anik
authors.forename: H Tahsin
authors.initials: HT
authors.lastname: Sarisoy
authors.forename: Ercument
authors.initials: E
authors.lastname: Ciftci
authors.forename: Ali
authors.initials: A
authors.lastname: Demirci
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D003560:Cysts / Q000175:diagnosis*; D003937:Diagnosis, Differential; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D004444:Echinococcosis, Hepatic / Q000175:diagnosis*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008099:Liver / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity