title: Quantitative evaluation of cerebral blood flow and oxygen metabolism in normal anesthetized rats: 15O-labeled gas inhalation PET with MRI Fusion.
abstract: PET with (15)O gas has been used for the quantitative measurement of cerebral blood flow (CBF), cerebral metabolic rate of oxygen (CMRO(2)), oxygen extraction fraction (OEF), and cerebral blood volume (CBV) in humans. However, several technical difficulties limit its use in experiments on small animals. Herein, we describe the application of the (15)O gas steady-state inhalation method for normal anesthetized rats.
  
  
  METHODS
  Eight normal male Sprague-Dawley rats (mean body weight ± SD, 268 ± 14 g) under anesthesia were investigated by (15)O-labeled gas PET. After tracheotomy, an airway tube was placed in the trachea, and the animals were connected to a ventilator (tidal volume, 3 cm(3); frequency, 60/min). The CBF and OEF were measured according to the original steady-state inhalation technique under artificial ventilation with (15)O-CO(2) and (15)O-O(2) gases delivered through the radioactive gas stabilizer. CBV was measured by (15)O-CO gas inhalation and corrected for the intravascular hemoglobin-bound (15)O-O(2). Arterial blood sampling was performed during each study to measure the radioactivity of the whole blood and plasma. MR image was performed with the same acrylic animal holder immediately after the PET. Regions of interest were placed on the whole brain of the PET images with reference to the semiautomatically coregistered PET/MR fused images.
  
  
  RESULTS
  The data acquisition time for the whole PET experiment in each rat was 73.3 ± 5.8 (range, 68-85) min. In both the (15)O-CO(2) and the (15)O-O(2) studies, the radioactivity count of the brain reached a steady state by approximately 10 min after the start of continuous inhalation of the gas. The quantitative PET data of the whole brain were as follows: CBF, 32.3 ± 4.5 mL/100 mL/min; CMRO(2), 3.23 ± 0.42 mL/100 mL/min; OEF, 64.6% ± 9.1%; and CBV, 5.05 ± 0.45 mL/100 mL.
  
  
  CONCLUSIONS
  Although further technical improvements may be needed, this study demonstrated the feasibility of quantitative PET measurement of CBF, OEF, and CMRO(2) using the original steady-state inhalation method of (15)O-CO(2) and (15)O-O(2) gases and measurement of CBV using the (15)O-CO gas inhalation method in the brain of normal anesthetized rats.
authors.affiliation: Department of Nuclear Medicine and Tracer Kinetics, Osaka University Graduate School of Medicine, Suita, Osaka, Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Watabe
authors.forename: Eku
authors.initials: E
authors.lastname: Shimosegawa
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Watabe
authors.forename: Yasukazu
authors.initials: Y
authors.lastname: Kanai
authors.forename: Kohei
authors.initials: K
authors.lastname: Hanaoka
authors.forename: Takashi
authors.initials: T
authors.lastname: Ueguchi
authors.forename: Kayako
authors.initials: K
authors.lastname: Isohashi
authors.forename: Hiroki
authors.initials: H
authors.lastname: Kato
authors.forename: Mitsuaki
authors.initials: M
authors.lastname: Tatsumi
authors.forename: Jun
authors.initials: J
authors.lastname: Hatazawa
mesh_terms: D000758:Anesthesia; D000818:Animals; D001921:Brain / Q000473:pathology; D002138:Calibration; D002245:Carbon Dioxide / Q000737:chemistry; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005740:Gases; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption; D010103:Oxygen Isotopes / Q000737:chemistry; D019047:Phantoms, Imaging; D049268:Positron-Emission Tomography / Q000379:methods*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012542:Scattering, Radiation; D013997:Time Factors
chemical_list: D005740:Gases; D010103:Oxygen Isotopes; D002245:Carbon Dioxide; D010100:Oxygen