In vivo measurement of brain glucose transport and metabolism employing glucose ¹¹C

The radiopharmaceutical glucose ¹¹C was used for in vivo measurement of brain glucose transport kinetics and metabolism in the rhesus monkey. Radiotracer was injected intravenously as a bolus. Radioactivity was continuously recorded from the head and from the arterial blood via an indwelling peripheral artery catheter for a collection period of 2-3 min. To correct the reading obtained from the head for radioactivity contained in blood, a second intravenous injection of the vascular tracer ¹⁵O labeled carboxyhemoglobin was used. The method was tested in nine phencyclidine anesthetized monkeys in which cerebral glucose metabolism (CMR[Glc]) was simultaneously measured by our method and by a standard method employing the Fick principle. A highly significant correlation was found between the two methods of measuring CMR(Glc) (r = 0.929). In addition, our model predicted a ratio of forward to reverse glucose flux across the blood brain barrier (BBB) (1.37 ± 0.23 SD), the brain to blood glucose concentration ratio across the BBB (0.633 ± 0.14), the relative tissue free glucose space (17 ± 7%), the brain free glucose concentration (13.6 ± 8.5 mg/100 g of tissue), and the brain free glucose turnover time (2.96 ± 1.98 min).