title: Inhalation regional cerebral blood flow: the use of tidal CO2 data to find radionuclide activity associated with exhaled alveolar gas.
abstract: When calculating cerebral blood flow by the inhalation regional cerebral blood flow technique, radionuclide activity associated with exhaled alveolar gas is used to represent the arterial input function for each brain region. In this study, tidal CO2 data are used to identify respiratory gas samples that contain alveolar gas. Traditional methods identify alveolar gas samples by searching for maxima and minima in the raw air curve. The raw air curve is determined by sequentially counting radionuclide activity in respiratory gases sampled at the mouth. Traditional methods sometimes erroneously identify and use maxima or minima that do not represent alveolar gas. The use of CO2 data is advantageous since the range of CO2 during exhalation can identify those exhalations that approach the functional reserve capacity and hence represent alveolar gas. The arterial input function is represented by counting intervals from the raw air curve which coincide with exhalation of alveolar gas as identified by CO2 data. This approach for representing the arterial input function is fully automatic, accurate, and reproducible.
authors.affiliation: Department of Radiology, Medical College of Georgia, Augusta 30912.
authors.forename: J D
authors.initials: JD
authors.lastname: Allison
authors.forename: T B
authors.initials: TB
authors.lastname: Kingsbury
authors.forename: H G
authors.initials: HG
authors.lastname: Sullivan
authors.forename: J J
authors.initials: JJ
authors.lastname: Goode
mesh_terms: D001921:Brain / Q000098:blood supply*; D002245:Carbon Dioxide / Q000032:analysis*; D002560:Cerebrovascular Circulation; D006801:Humans; D009928:Organ Specificity; D011650:Pulmonary Alveoli / Q000502:physiology; D012039:Regional Blood Flow; D012119:Respiration; D014980:Xenon Radioisotopes
chemical_list: D014980:Xenon Radioisotopes; D002245:Carbon Dioxide