title: Hyperpolarized water as an MR imaging contrast agent: feasibility of in vivo imaging in a rat model.
abstract: OBJECTIVE
  To assess the feasibility of a perfusion magnetic resonance (MR) imaging technique that uses Overhauser dynamic nuclear polarization (DNP) to provide contrast during the continuous delivery of hyperpolarized water in rats.
  
  
  METHODS
  Protocols approved by the local institutional animal care and use committees were followed. Twelve male Wistar rats were anesthetized and prepared by placing injection tubing in the subcutaneous layer (n=3), peritoneum (n=3), aorta (n=3), or carotid artery (n=3). Water was hyperpolarized by means of Overhauser DNP in the 0.35-T fringe field of a 1.5-T MR imaging magnet by using a custom-built system to continuously deliver radical-free hyperpolarized water to the subject. Fast gradient-echo and spoiled gradient-recalled-echo MR imaging sequences were used. The signal-to-noise ratio (SNR) of the images was calculated and compared.
  
  
  RESULTS
  Images showed greatly altered SNR and enhanced flow contrast at all injection locations. For subcutaneous and intraperitoneal injections, the water perfusion trajectory was observed for approximately 5 seconds after injection. Flow through a 4.2-cm length of artery was seen during intra-aortic injection. The right hemisphere of the brain was seen during injection into the right carotid artery. Images with hyperpolarized water had greatly altered SNR compared with images without injection or with the injection of nonhyperpolarized water, with a range of 13%-27% for the carotid and 444%-2900% for the other regions.
  
  
  CONCLUSIONS
  Perfusion contrast for MR imaging can be obtained by continuously infusing hyperpolarized water, providing localized angiography or brain perfusion information in vivo for rat models.
authors.affiliation: Department of Chemistry, University of California, Santa Barbara, Mesa Road, Santa Barbara, CA 93106, USA.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Lingwood
authors.forename: Ting Ann
authors.initials: TA
authors.lastname: Siaw
authors.forename: Napapon
authors.initials: N
authors.lastname: Sailasuta
authors.forename: Osama A
authors.initials: OA
authors.lastname: Abulseoud
authors.forename: Henry R
authors.initials: HR
authors.lastname: Chan
authors.forename: Brian D
authors.initials: BD
authors.lastname: Ross
authors.forename: Pratip
authors.initials: P
authors.lastname: Bhattacharya
authors.forename: Songi
authors.initials: S
authors.lastname: Han
mesh_terms: D000818:Animals; D001158:Arteries / Q000033:anatomy & histology* / Q000502:physiology*; D001783:Blood Flow Velocity / Q000502:physiology; D003287:Contrast Media / Q000737:chemistry*; D005240:Feasibility Studies; D007089:Image Enhancement / Q000379:methods*; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055672:Static Electricity; D014867:Water / Q000737:chemistry*
chemical_list: D003287:Contrast Media; D014867:Water