Abstract
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Objectives An injectable 15O2 system of 15O2 labeled hemoglobin-containing vesicles (15O2-HbV) was developed to determine cerebral oxygen consumption and evaluated using the bolus injection method in our previous study. However, small animal may suffer from terrible damage due to frequent arterial blood samplings. In this study, we measured cerebral hemodynamic parameters of rats using the 15O2-HbV with the steady-state (SS) method which can estimate the parameters with a few blood sampling points.
Methods Seven rats were studied with a small animal PET. Administration volumes of H215O and 15O2-HbV were increased gradually to compensate radioactive decay of 15O in rat’s body using the multi-programming syringe pump. C15O-labeled HbV (C15O-HbV) was also applied to measure cerebral blood volume (CBV). Cerebral blood flow (CBF), oxygen extraction fraction (OEF) and cerebral metabolic rate for oxygen (CMRO2) were calculated from the data of H215O, 15O2-HbV and C15O-HbV.
Results Radioactivity concentration of 15O rapidly achieved equilibrium in blood and in whole brain at about 2 min after each tracer administration. The mean values of CBF, OEF, CMRO2 and CBV using the SS method were 54.0±2.9 mL/100g/min, 0.58±0.05, 6.0±0.4 mL/100g/min and 4.7±0.9 mL/100g, respectively. These cerebral hemodynamic parameters using the15O2-HbV with the SS method were not significantly different from the results reported previously.
Conclusions The 15O2-HbV with the SS method is very useful in measurement of cerebral oxygen metabolism on small animal study compared to that with bolus method.
- © 2009 by Society of Nuclear Medicine