title: Appearances of colorectal hepatic metastases at diffusion-weighted MRI compared with histopathology: initial observations.
abstract: OBJECTIVE
  To describe the appearances of colorectal liver metastases on diffusion-weighted MRI (DW-MRI) and to compare these appearances with histopathology.
  
  
  METHODS
  43 patients with colorectal liver metastases were evaluated using breath-hold DW-MRI (b-values 0, 150 and 500 s mm(-2)). The b=500 s mm(-2) DW-MRI were reviewed consensually for lesion size and appearance by two readers. 18/43 patients underwent surgery allowing radiological-pathological comparison. Tissue sections were reviewed by a pathologist, who classified metastases histologically as cellular, fibrotic, necrotic or mixed. The frequency of DW-MRI findings and histological features were compared using the χ(2) test.
  
  
  RESULTS
  84 metastases were found in 43 patients. On b=500 s mm(-2) DW-MRI, metastases showed three high signal intensity patterns: rim (55/84), uniform (23/84) and variegate (6/84). Of the 55 metastases showing rim pattern, 54 were >1 cm in diameter (p<0.01, χ(2) test). 25/84 metastases were surgically resected. Of these, 11/22 metastases >1 cm in diameter showed rim pattern and demonstrated central necrosis at histopathology (p=0.04, χ(2) test). No definite relationship was found between uniform and variegate patterns with histology.
  
  
  CONCLUSIONS
  Rim high signal intensity was the most common appearance of colorectal liver metastases >1 cm diameter on DW-MRI at b-values of 500 s mm(-2), a finding attributable to central necrosis.
authors.affiliation: Department of Radiology, Royal Marsden Hospital, Sutton, UK.
authors.forename: E D
authors.initials: ED
authors.lastname: Scurr
authors.forename: D J
authors.initials: DJ
authors.lastname: Collins
authors.forename: L
authors.initials: L
authors.lastname: Temple
authors.forename: N
authors.initials: N
authors.lastname: Karanjia
authors.forename: M O
authors.initials: MO
authors.lastname: Leach
authors.forename: D-M
authors.initials: DM
authors.lastname: Koh
mesh_terms: D000328:Adult; D000368:Aged; D015179:Colorectal Neoplasms; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D006801:Humans; D008099:Liver / Q000473:pathology*; D008113:Liver Neoplasms / Q000473:pathology* / Q000556:secondary; D008297:Male; D008875:Middle Aged; D009336:Necrosis; D015588:Observer Variation