title: Three-dimensional ultrasound molecular imaging of angiogenesis in colon cancer using a clinical matrix array ultrasound transducer.
abstract: OBJECTIVE
  We sought to assess the feasibility and reproducibility of 3-dimensional ultrasound molecular imaging (USMI) of vascular endothelial growth factor receptor 2 (VEGFR2) expression in tumor angiogenesis using a clinical matrix array transducer and a clinical grade VEGFR2-targeted contrast agent in a murine model of human colon cancer.
  
  
  METHODS
  Animal studies were approved by the Institutional Administrative Panel on Laboratory Animal Care. Mice with human colon cancer xenografts (n = 33) were imaged with a clinical ultrasound system and transducer (Philips iU22; X6-1) after intravenous injection of either clinical grade VEGFR2-targeted microbubbles or nontargeted control microbubbles. Nineteen mice were scanned twice to assess imaging reproducibility. Fourteen mice were scanned both before and 24 hours after treatment with either bevacizumab (n = 7) or saline only (n = 7). Three-dimensional USMI data sets were retrospectively reconstructed into multiple consecutive 1-mm-thick USMI data sets to simulate 2-dimensional imaging. Vascular VEGFR2 expression was assessed ex vivo using immunofluorescence.
  
  
  RESULTS
  Three-dimensional USMI was highly reproducible using both VEGFR2-targeted microbubbles and nontargeted control microbubbles (intraclass correlation coefficient, 0.83). The VEGFR2-targeted USMI signal significantly (P = 0.02) decreased by 57% after antiangiogenic treatment compared with the control group, which correlated well with ex vivo VEGFR2 expression on immunofluorescence (ρ = 0.93, P = 0.003). If only central 1-mm tumor planes were analyzed to assess antiangiogenic treatment response, the USMI signal change was significantly (P = 0.006) overestimated by an average of 27% (range, 2%-73%) compared with 3-dimensional USMI.
  
  
  CONCLUSIONS
  Three-dimensional USMI is feasible and highly reproducible and allows accurate assessment and monitoring of VEGFR2 expression in tumor angiogenesis in a murine model of human colon cancer.
authors.affiliation: From the Departments of *Radiology, Molecular Imaging Program at Stanford, School of Medicine, †Health, Research and Policy, and ‡Radiation Oncology, Stanford University, Stanford, CA.
authors.forename: Huaijun
authors.initials: H
authors.lastname: Wang
authors.forename: Osamu F
authors.initials: OF
authors.lastname: Kaneko
authors.forename: Lu
authors.initials: L
authors.lastname: Tian
authors.forename: Dimitre
authors.initials: D
authors.lastname: Hristov
authors.forename: Jürgen K
authors.initials: JK
authors.lastname: Willmann
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000150:complications / Q000000981:diagnostic imaging / Q000378:metabolism*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000295:instrumentation / Q000379:methods*; D051379:Mice; D008819:Mice, Nude; D057054:Molecular Imaging / Q000295:instrumentation / Q000379:methods*; D009389:Neovascularization, Pathologic / Q000150:complications / Q000000981:diagnostic imaging / Q000378:metabolism*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014463:Ultrasonography / Q000295:instrumentation / Q000379:methods*; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000378:metabolism*
chemical_list: D015415:Biomarkers; C000592875:Kdr protein, mouse; D040301:Vascular Endothelial Growth Factor Receptor-2