CEREBRAL BLOOD-FLOW MEASUREMENT DURING EMBOLIZATION OF THE RAT-BRAIN USING THE XENON INJECTION METHOD

The purpose of this study was to investigate if cerebral blood flow (C BF) was influenced by the volume of the bolus using the intracarotid ( 133)Xenon method in anesthetized rats, and to evaluate the effect of i ntracarotid embolization on hemispheric CBF. In 18 male Sprague-Dawley rats hemispheric CBF was calculated from the recorded clearance of an intracarotid injected 50 mu l bolus of Xenon. A second clearance reco rding was done after the injection of a 200 mu l bolus of (133)Xenon. Then the 18 animals were divided in 3 subsets each of 6 animals. In th e first subset of 6 animals a bolus of 200 mu l! (133)Xenon was given, clearance was recorded before and after the injection of a suspension of microemboli. In all the above experiments within 90sec after the i nitial bolus of (133)Xenon, 20 mu l (133)Xenon remaining in the caroti d catheter was flushed into the brain by saline or the suspension of e mboli. In the second subset of 6 rats the distribution of (133)Xenon i n various parts: of the brain and head was examined after killing the animals 35 sec after injection of a 200 mu l bolus of Xenon. The third subset of 6 rats was treated as the second subset, except for the siz e of the bolus which was 50 mu l of (133)Xenon. The calculated CBF val ues were independent of the volume of the bolus. At the post-mortem ex amination 76% of the radioactivity was located in the right hemisphere and the majority of the remainder in the head outside the brain. The clearance curve was not monoexponential, but flattened out within the initial 30 sec when clearance from areas with high CBF dominated the i nitial 15-second period, then clearance from areas with lower CBF valu es were more prominent in the following 15-second period. Embolization significantly reduced right hemispheric CBF to 0.26 (0.09-0.50) of th e value immediately before embolization. The findings demonstrate appl icability of CBF measurements using the intra-arterial (133)Xenon inje ction method during embolization of the rat brain, provided a second b olus of (133)Xenon is given before the embolization.