title: The validity of an intravenous isotope method for cerebral blood flow measurements. An experimental study.
abstract: The intravenous isotope method has been examined. The method uses 99Tc as the indicator with recording of the radioactivity with two gamma-dectors placed bilaterally over the skull and oriented over the bifurcation of the middle cerebral artery. 65% of the total curve obtained was found to be generated by activity passing in the ipsilateral internal carotid artery, 25% in the contralateral internal carotid artery and less than 10% by activity passing in the two external carotid arteries. The counting rate efficiency for an intracerebral location was 19.4 +/- 1.8 times the count rate from the same activity placed at 1 m distance in air which in turn was 5 cps/muCi. The variability in efficiency from patient to patient was thus estimated at +/- 9%. The duration of the input bolus had a marked influence on the vurve, which will be of importance since it showed a rather large variability from patient. Using the peak activity as an index of the cerebral blood flow the intravenous method showed a surprisingly good correlation with the 133Xe wash-out method; the correlation coefficient was 0.93 and the variability at slightly subnormal values estimated at +/- 15%. It is concluded that the method can be used in the case of limited demands on the accuracy of the cerebral blood flow determinations.
mesh_terms: D001921:Brain / Q000098:blood supply*; D002339:Carotid Arteries / Q000502:physiology; D005720:Gamma Rays; D006801:Humans; D007269:Injections, Intra-Arterial; D007275:Injections, Intravenous; D007457:Iodine Radioisotopes; D011865:Radioisotope Dilution Technique; D011874:Radiometry; D012039:Regional Blood Flow; D013667:Technetium / Q000008:administration & dosage; D014980:Xenon Radioisotopes
chemical_list: D007457:Iodine Radioisotopes; D014980:Xenon Radioisotopes; D013667:Technetium