title: Imaging of blood flow using hyperpolarized [(13)C]urea in preclinical cancer models.
abstract: OBJECTIVE
  To demonstrate dynamic imaging of a diffusible perfusion tracer, hyperpolarized [(13)C]urea, for regional measurement of blood flow in preclinical cancer models.
  
  
  METHODS
  A pulse sequence using balanced steady state free precession (bSSFP) was developed, with progressively increasing flip angles for efficient sampling of the hyperpolarized magnetization. This allowed temporal and volumetric imaging of the [(13)C]urea signal. Regional signal dynamics were quantified for kidneys and liver, and estimates of relative blood flows were derived from the data. Detailed perfusion simulations were performed to validate the methodology.
  
  
  RESULTS
  Significant differences were observed in the signal patterns between normal and cancerous murine hepatic tissues. In particular, a 19% reduction in mean blood flow was observed in tumors, with 26% elevation in the tumor rim. The blood flow maps were also compared with metabolic imaging results with hyperpolarized [1-(13)C]pyruvate.
  
  
  CONCLUSIONS
  Regional assessment of perfusion is possible by imaging of hyperpolarized [(13)C]urea, which is significant for the imaging of cancer.
authors.affiliation: Department of Radiology and Biomedical Imaging, University of California, San Francisco, California 94158-2512, USA.
authors.forename: Cornelius
authors.initials: C
authors.lastname: von Morze
authors.forename: Peder E Z
authors.initials: PE
authors.lastname: Larson
authors.forename: Simon
authors.initials: S
authors.lastname: Hu
authors.forename: Kayvan
authors.initials: K
authors.lastname: Keshari
authors.forename: David M
authors.initials: DM
authors.lastname: Wilson
authors.forename: Jan Henrik
authors.initials: JH
authors.lastname: Ardenkjaer-Larsen
authors.forename: Andrei
authors.initials: A
authors.lastname: Goga
authors.forename: Robert
authors.initials: R
authors.lastname: Bok
authors.forename: John
authors.initials: J
authors.lastname: Kurhanewicz
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Vigneron
mesh_terms: D000465:Algorithms; D000818:Animals; D001783:Blood Flow Velocity; D002247:Carbon Isotopes / Q000494:pharmacology*; D004058:Diffusion; D004195:Disease Models, Animal; D006801:Humans; D007668:Kidney / Q000473:pathology; D008099:Liver / Q000473:pathology; D008297:Male; D051379:Mice; D009368:Neoplasm Transplantation; D009369:Neoplasms / Q000098:blood supply* / Q000175:diagnosis*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D002247:Carbon Isotopes