title: Diffusion-weighted MRI of metastatic liver lesions: is there a difference between hypervascular and hypovascular metastases?
abstract: BACKGROUND
  Different perfusion characteristics and histopathologic features of liver metastasis may potentially lead to different diffusion-weighted magnetic resonance imaging (DW-MRI) characteristics which can affect the performance of DW-MRI in their diagnosis.
  
  
  OBJECTIVE
  To compare ADC values of hypervascular and hypovascular metastases and the added value of DW-MRI to T2-weighted (T2-w) images in their detection.
  
  
  METHODS
  In this retrospective study, 46 patients (21 with hypervascular, 25 with hypovascular liver metastases) who had undergone abdominal MRI were included. Two independent observers first reviewed T2-w images only and then T2-w+DW-MR images and recorded number of metastases in each session. Lesion detection rate was compared using McNemar test. ADC of metastases in each patient was measured and compared between hypo- and hypervascular lesions using t-test.
  
  
  RESULTS
  A total of 153 hypervascular and 187 hypovascular metastases were detected at consensus review. Two observers detected significantly more hypervascular metastases on T2-w+DW-MR image review session compared to T2-w image only review session (reader 1: 148 [96.7%] vs. 129 [84.3%], P=0.002; reader 2: 125 [81.9%] vs. 113 [73.8%], P=0.004). Detection rate of hypovascular metastases was similar between two sessions for both observers (reader 1: 180 [96.2%] vs. 184 [98.4%]; reader 2: 176 [94.1%] vs. 180 [96.2%], P>0.05). The mean ADC value of hypervascular metastases was significantly lower than mean ADC value of hypovascular metastases (1.23+/-0.31 × 10(-3)mm(2)/s vs. 1.49+/-0.19 × 10(-3)mm(2)/s) (P=0.001).
  
  
  CONCLUSIONS
  Liver metastases are not a homogenous group of lesions with uniform DW-MRI features. Hypervascular metastases demonstrate significantly lower ADC values compared to hypovascular metastases. DW-MRI improved detection of hypervascular metastases compared to T2-w images alone and is a useful adjunct to T2-w images for their detection.
authors.affiliation: The University of Chicago, Department of Radiology, Chicago, IL, USA Ludwig-Maximilians-University Hospital Munich, Institute for Clinical Radiology, Munich, Germany christine.schmid-tannwald@med.uni-muenchen.de.
authors.forename: Christine
authors.initials: C
authors.lastname: Schmid-Tannwald
authors.affiliation: The University of Chicago, Department of Radiology, Chicago, IL, USA.
authors.forename: Stephen
authors.initials: S
authors.lastname: Thomas
authors.affiliation: The University of Chicago, Department of Radiology, Chicago, IL, USA Philips Healthcare, MR Clinical Science, Cleveland, OH, USA.
authors.forename: Marko K
authors.initials: MK
authors.lastname: Ivancevic
authors.affiliation: The University of Chicago, Department of Radiology, Chicago, IL, USA.
authors.forename: Farid
authors.initials: F
authors.lastname: Dahi
authors.affiliation: Ludwig-Maximilians-University Hospital Munich, Institute for Clinical Radiology, Munich, Germany.
authors.forename: Carsten
authors.initials: C
authors.lastname: Rist
authors.affiliation: The University of Chicago, Department of Radiology, Chicago, IL, USA.
authors.forename: Ila
authors.initials: I
authors.lastname: Sethi
authors.affiliation: The University of Chicago, Department of Radiology, Chicago, IL, USA.
authors.forename: Aytekin
authors.initials: A
authors.lastname: Oto
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001706:Biopsy; D003287:Contrast Media; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D019786:Gadolinium DTPA; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008113:Liver Neoplasms / Q000098:blood supply* / Q000556:secondary*; D008297:Male; D008875:Middle Aged; D009389:Neovascularization, Pathologic / Q000175:diagnosis*; D012189:Retrospective Studies
chemical_list: D003287:Contrast Media; C064925:gadodiamide; D019786:Gadolinium DTPA
keywords: ADC measurements; Diffusion-weighted MRI; hypovascular and hypovascular liver metastases