Tomographic measurement of local cerebral glucose metabolic rate in humans with (F‐18)2‐fluoro‐2‐deoxy‐D‐glucose: Validation of method

TLDR

Tracer techniques and quantitative autoradiographic and tissue counting models were combined with positron computed tomography and (F‑18) FDG to measure local cerebral metabolic rate for glucose in humans, extending the model originally developed by Sokoloff et al. The study developed a three‑compartment model incorporating FDG‑6‑PO4 hydrolysis to measure kinetic constants and calculate LCMRGlc. The authors used this model with an ECAT positron computed tomography system to estimate rate constants, lumped constant, and model stability, while also determining precursor pool turnover, distribution volumes, and red blood cell‑plasma concentration ratios. Hydrolysis of FDG‑6‑PO4, though small, was significant; cerebral FDG‑6‑PO4 rose for ~90 min, plateaued, then slowly declined, with blood activity being a minor fraction of tissue after 10 min; LCMRGlc measurements over 5 h were reproducible within ±5.5 % for ~2 cm² regions, and venous sampling was validated as a substitute for arterial sampling.

Abstract

Abstract Tracer techniques and quantitative autoradiographic and tissue counting models for measuremnt of metabolic rates were combined with positron computed tomography (PCT) and (F‐18)2‐fluoro‐2‐deoxy‐D‐glucose (FDG) for the measurement of local cerebral metabolic rate for glucose (LCMRGlc) in humans. A three‐compartment model, which incorporates hydrolysis of FDG‐6‐PO 4 to FDG, was developed for the measure of kinetic constants and calculation of LCMRGlc. Our model is an extension of that developed by Sokoloff et al. Although small, hydrolysis of FDG‐6‐PO 4 was found to be significant. A PCT system, the ECAT, was used to determine the rate constants, lumped constant, and stability of the model in human beings. The data indicate that cerebral FDG‐6‐PO 4 in humans increases for about 90 minutes, plateaus, and then slowly decreases. After 10 minutes, cerebral blood FDG activity levels were found to be a minor fraction of tissue activity. Precursor pool turnover rate, distribution volumes, and red blood cell‐plasma concentration ratios were determined. Reproducibility (precision) of LCMRGlc measurements (∼2 cm 2 regions) was ± 5.5% over a 5‐hour period. The replacement of arterial blood sampling with venous sampling was validated.