title: Identifying tumor vascular permeability heterogeneity with magnetic resonance imaging contrast agents.
abstract: OBJECTIVE
  Dynamic contrast enhanced (DCE) MR mammography (MRM) uses tumor capillary density differences for prognosis. The heterogeneous response of permeability-surface area products (PS = Kp<-->t) was examined in mammary tumors, as a function of contrast agent size, to determine what effect ROI size might have on PS and prognosis.
  
  
  METHODS
  DCE FLASH signal intensities were converted to gadolinium concentrations by a standard curve, which was fitted by a two-compartment model for the tumor's extravascular extracellular space (EES) volume fraction (ve), and the tumor volume normalized transfer rate between plasma and EES (Kp<-->t/VT).
  
  
  RESULTS
  For Gd-DTPA ve = 9% to 13% Kp<-->t/VT = 0.01 to 0.06 minutes-1, and the macromolecular agent, PAMAM-TU-DTPA G = 4 ve = 0.8% to 1% Kp<-->t/VT = 0.008 to 0.04 minutes(-1). Significant differences in Kp<-->t/VT for local regions were found for both agents relative to the whole tumor and the macromolecular agent had greater dynamic range.
  
  
  CONCLUSIONS
  Smaller ROI values or pixels should yield more accurate assessment of neovascularization.
authors.affiliation: Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, Champaign, Illinois, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Aref
authors.forename: Martin
authors.initials: M
authors.lastname: Brechbiel
authors.forename: Erik C
authors.initials: EC
authors.lastname: Wiener
mesh_terms: D000818:Animals; D002199:Capillary Permeability; D003287:Contrast Media / Q000493:pharmacokinetics; D050091:Dendrimers; D005038:Ethylnitrosourea; D019786:Gadolinium DTPA / Q000493:pharmacokinetics; D046911:Macromolecular Substances; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008325:Mammary Neoplasms, Experimental / Q000098:blood supply* / Q000473:pathology*; D008433:Mathematics; D008833:Microcirculation; D011073:Polyamines / Q000493:pharmacokinetics; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D003287:Contrast Media; D050091:Dendrimers; D046911:Macromolecular Substances; C104700:PAMAM Starburst; D011073:Polyamines; D019786:Gadolinium DTPA; D005038:Ethylnitrosourea