title: Tomographic fluorescence imaging of tumor vascular volume in mice.
abstract: OBJECTIVE
  To prospectively determine the feasibility of imaging vascular volume fraction (VVF) and its therapeutic inhibition in mouse models of cancer with three-dimensional fluorescence molecular tomography (FMT).
  
  
  METHODS
  All studies were approved by the institutional animal review committee and were in accordance with National Institutes of Health guidelines. CT26 colon tumor-bearing mice were imaged with FMT after intravenous administration of long-circulating near-infrared fluorescent blood-pool agents optimized for two nonoverlapping excitation wavelengths (680 and 750 nm). A total of 58 mice were used for imaging VVF to evaluate the following: (a) differences in ectopically and orthotopically implanted tumors (n = 10), (b) cohorts of mice (n = 24) treated with anti-vascular endothelial growth factor (VEGF) antibody, (c) serial imaging in same animal to determine natural course of angiogenesis (n = 4), and (d) dose response to anti-VEGF therapy (n = 20). To compare groups receiving antiangiogenic chemotherapy, analysis of variance was used.
  
  
  RESULTS
  Fluorochrome concentrations derived from FMT measurements were reconstructed with an accuracy of +/-10% at 680 nm and +/-7% at 750 nm and in a depth-independent manner, unlike at reflectance imaging. FMT measurements of vascular fluorescent probes were linear, with concentration over several orders of magnitude (r > 0.98). VVFs of colonic tumors, which varied considerably among animals (3.5% +/- 1.5 [standard deviation]), could be depicted with in vivo imaging in three dimensions with less than 5 minutes of imaging and less than 3 minutes of analysis. The natural course of angiogenesis and its inhibition could be reliably imaged and depicted serially in different experimental setups.
  
  
  CONCLUSIONS
  FMT is a tomographic optical imaging technique that, in conjunction with appropriate fluorescent probes, allows quantitative visualization of biologic processes.
authors.affiliation: Center for Molecular Imaging Research, Massachusetts General Hospital and Harvard Medical School, Building 149, 13th St, Room 5403, Charlestown, MA 02129, USA.
authors.forename: Xavier
authors.initials: X
authors.lastname: Montet
authors.forename: Jose-Luiz
authors.initials: JL
authors.lastname: Figueiredo
authors.forename: Herlen
authors.initials: H
authors.lastname: Alencar
authors.forename: Vasilis
authors.initials: V
authors.lastname: Ntziachristos
authors.forename: Umar
authors.initials: U
authors.lastname: Mahmood
authors.forename: Ralph
authors.initials: R
authors.lastname: Weissleder
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000098:blood supply* / Q000473:pathology*; D007089:Image Enhancement / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D051379:Mice; D008819:Mice, Nude; D008856:Microscopy, Fluorescence / Q000379:methods*; D009389:Neovascularization, Pathologic / Q000473:pathology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D041622:Tomography, Optical / Q000379:methods*