Simplified measurement of deoxyglucose utilization rate.

UNLABELLED

The reliability of the dose uptake ratio (DUR), a widely used index of 18F-fluoro-2-deoxy-D-glucose (18FDG) metabolism in a variety of tumors, depends on the overall rate of removal of 18FDG from the circulation. Correcting for this factor is important if DUR is to be used quantitatively for pre- and post-treatment assessments of tumors.

METHODS

We developed a simplified kinetic method (SKM), based on measured blood curves from a control group, which requires one venous blood sample. We compared the simplified method to the conventional kinetic method and the widely used DUR index in 13 patients with grade 3 or 4 non-small-cell lung carcinoma. Studies were obtained before and after treatment. In all patients, dynamic PET imaging and blood activity measurement was performed for 80 min. The utilization rate of 18FDG (MRDGlc) was calculated by using a three-compartment model and correlated with a 55-min measurement of DUR and with the simplified kinetic method.

RESULTS

Coefficients of determination (R2) between MRDGlc and DUR before and after treatment were 0.53 and 0.71, respectively. Using the SKM, these values improved significantly (p < 0.0001) to 0.96 and 0.94, respectively. The pooled pre- and post-treatment coefficient of determination for DUR versus MRDGlc was 0.81; for SKM, it improved significantly (p < 0.001) to 0.98.

CONCLUSION

These results indicate that the observed tumor tissue uptake of 18FDG, corrected for blood 18FDG activity and glucose concentration, can reliably predict glucose metabolic rate from a single static image acquired at between 45 min and 1 hr after injection. This has substantial implications for the quantitative use of 18FDG PET to diagnose and manage malignancy.