title: Apparent diffusion coefficient: a quantitative parameter for in vivo tumor characterization.
abstract: OBJECTIVE
  The purpose of the this study was to evaluate the potential of diffusion weighted imaging (DWI) to distinguish different tissue compartments in early, intermediate and advanced tumor stages.
  
  
  METHODS
  Twenty-two male mice were induced with squamous cell tumor (SCCVII) and scanned with a clinical 1.5 T scanner. T1-SE, T2-FSE, diffusion weighted Line-Scan-MRI and contrast enhanced T1-SE were obtained from mice with early (tumor volume 10-100 mm(3)), intermediate (200-600 mm(3)), advanced tumors (600-1000 mm(3)) and tumor necrosis (>1500 mm(3)). The apparent diffusion coefficient (ADC) of different tumor compartments was calculated offline with a pixel-by-pixel method. The animals were sacrificed immediately after scanning and histopathologic correlation was performed.
  
  
  RESULTS
  In early stages of tumor development, tumors appeared homogeneous on diffusion weighted images with an ADC of 0.64+/-0.06 x 10(-3) mm(2)/s. With tumor progression the ADC in the rim areas of tumor increased significantly (intermediate stage: 0.70+/-0.11 x 10(-3) mm(2)/s; advanced stage: 0.88+/-0.11 x 10(-3) mm(2)/s; tumor necrosis 1.03+/-0.06 x 10(-3) mm(2)/s), whereas the ADC in viable tumor remained constant. Histologically the areas with an increased ADC correlated well with areas of necrosis (reduced cell density).
  
  
  CONCLUSIONS
  The ADC is a non-invasive technique to monitor changes in the biological structure of tumor tissue during tumor progression. Thus, DWI is a potential diagnostic tool for in-vivo tissue characterization.
authors.affiliation: Department of Radiology, Division of Muskulo Skeletal Radiology, University of Vienna, AKH-7F Währinger Gürtel 18-20, A-1090 Vienna, Austria. andreas.herneth@univie.ac.at
authors.forename: Andreas M
authors.initials: AM
authors.lastname: Herneth
authors.forename: Samira
authors.initials: S
authors.lastname: Guccione
authors.forename: Mark
authors.initials: M
authors.lastname: Bednarski
mesh_terms: D000818:Animals; D002294:Carcinoma, Squamous Cell / Q000175:diagnosis* / Q000473:pathology; D038524:Diffusion Magnetic Resonance Imaging; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D009368:Neoplasm Transplantation; D012983:Soft Tissue Neoplasms / Q000175:diagnosis* / Q000473:pathology; D014407:Tumor Cells, Cultured