title: Non-invasive determination of tumor oxygen tension and local variation with growth.
abstract: OBJECTIVE
  The objective was to develop and demonstrate a novel noninvasive technique of measuring regional pO2 in tumors. The method is based on measuring 19F nuclear magnetic resonance spin-lattice relaxation rate (R1 = 1/T1) of perfluorocarbon (PFC) emulsion discretely sequestered in a tumor.
  
  
  METHODS
  We have examined pO2 in the Dunning prostate tumor R3327-AT1 implanted in a Copenhagen rat. Oxypherol blood substitute emulsion was administered intravenously and became sequestered in tissue. Proton magnetic resonance imaging (MRI) showed tumor anatomy and correlated 19F MRI indicated the distribution of perfluorocarbon. Fluorine-19 spectroscopic relaxometry was used to measure pO2 in the tumor and repeated measurements over a period of 3 weeks showed the variation in local pO2 during tumor growth.
  
  
  RESULTS
  Perfluorocarbon initially resided in the vascularized peripheral region of the tumor: 19F nuclear magnetic resonance R1 indicated pO2 approximately 75 torr in a small tumor (approximately 1 cm) in an anesthetized rat. As the tumor grew, the sequestered PFC retained its original distribution. When the tumor had doubled in size the residual PFC was predominantly in the core of the tumor and the pO2 of this region was approximately 1 torr indicating central tumor hypoxia.
  
  
  CONCLUSIONS
  We have demonstrated a novel noninvasive approach to monitoring regional tumor pO2. Given the critical role of oxygen tension in tumor response to therapy this may provide new insight into tumor physiology, the efficacy of various therapeutic approaches, and ultimately provide a clinical technique for assessing individual tumor oxygenation.
authors.affiliation: Department of Radiology, UT-Southwestern Medical Center, Dallas 75235-9058.
authors.forename: R P
authors.initials: RP
authors.lastname: Mason
authors.forename: P P
authors.initials: PP
authors.lastname: Antich
authors.forename: E E
authors.initials: EE
authors.lastname: Babcock
authors.forename: A
authors.initials: A
authors.lastname: Constantinescu
authors.forename: P
authors.initials: P
authors.lastname: Peschke
authors.forename: E W
authors.initials: EW
authors.lastname: Hahn
mesh_terms: D000230:Adenocarcinoma / Q000378:metabolism; D000818:Animals; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D009368:Neoplasm Transplantation; D009374:Neoplasms, Experimental / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D011471:Prostatic Neoplasms / Q000378:metabolism; D051381:Rats
chemical_list: D010100:Oxygen