title: Quantitative mapping of tumor vascularity using volumetric contrast-enhanced ultrasound.
abstract: OBJECTIVE
  The goal of this research project was to develop a volumetric strategy for real-time monitoring and characterization of tumor blood flow using microbubble contrast agents and ultrasound (US) imaging.
  
  
  METHODS
  Volumetric contrast-enhanced US (VCEUS) imaging was implemented on a SONIX RP US system (Ultrasonix Medical Corp, Richmond, BC) equipped with a broadband 4DL14-5/38 probe. Using a microbubble-sensitive harmonic imaging mode (transducer transmits at 5 MHz and receives at 10 MHz), acquisition of postscan-converted VCEUS data was achieved at a volume rate of 1 Hz. After microbubble infusion, custom data processing software was used to derive microbubble time-intensity curve-specific parameters, namely, blood volume (IPK), transit time (T1/2PK), flow rate (SPK), and tumor perfusion (AUC).
  
  
  RESULTS
  Using a preclinical breast cancer animal model, it is shown that millimeter-sized deviations in transducer positioning can have profound implications on US-based blood flow estimators, with errors ranging from 6.4% to 40.3% and dependent on both degree of misalignment (offset) and particular blood flow estimator. These errors indicate that VCEUS imaging should be considered in tumor analyses, because they incorporate the entire mass and not just a representative planar cross-section. After administration of an antiangiogenic therapeutic drug (bevacizumab), tumor growth was significantly retarded compared with control tumors (P > 0.03) and reflects observed changes in VCEUS-based blood flow measurements. Analysis of immunohistologic data revealed no differences in intratumoral necrosis levels (P = 0.70), but a significant difference was found when comparing microvessel density counts in control with therapy group tumors (P = 0.05).
  
  
  CONCLUSIONS
  VCEUS imaging was shown to be a promising modality for monitoring changes in tumor blood flow. Preliminary experimental results are encouraging, and this imaging modality may prove clinically feasible for detecting and monitoring the early antitumor effects in response to cancer drug therapy.
authors: Department of Radiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA. hoyt@uab.edu
authors: Kenneth
authors: K
authors: Hoyt
authors: Anna
authors: A
authors: Sorace
authors: Reshu
authors: R
authors: Saini
mesh_terms: D000818:Animals; D003287:Contrast Media; D005260:Female; D006439:Hemodynamics; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D045423:Microbubbles; D009369:Neoplasms / Q000098:blood supply* / Q000473:pathology; D009389:Neovascularization, Pathologic / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000473:pathology*; D055420:Perfusion Imaging / Q000295:instrumentation* / Q000379:methods; D014463:Ultrasonography / Q000295:instrumentation* / Q000379:methods
chemical_list: D003287:Contrast Media