| Abstrakt: |
Washout rates of Xe-133 from the canine liver have been externally recorded following injection into the hepatic artery and portal vein. Liver perfusion has been calculated from the curves on the basis of 1) the maximal slope (kh), 2) the height over area (H/A) and 3) the weighted harmonic mean (whm) of the rate constants of the exponentials analysed. When a lung signal was not superimposed on the curve, H/A and whm gave values higher following arterial than following portal injection, whereas kh values were no different. When a lung signal was superimposed, portal values were increased relative to arterial values, so that portal kh exceeded arterial and arterial H/A and whm were no greater than portal. In addition to recording over the liver, radioactivity in the lung has been simultaneously recorded with a second detector. Exponentials analysed from liver curves showed a correlation with corresponding exponentials analysed from lung curves. No significant differences were noted in the rate constants of exponentials between arterial and portal injections, either in liver or lung curves. It is suggested that there is no essential difference between the portal and arterial intrahepatic vascular beds, and that the observed differences between arterial and portal clearances are due to factors probably of a technical nature. |
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