[Correlation analysis between patlak plot and DAR using 11C-methionine PET]

Seven patients were studied with positron emission tomography (PET) using 11C-methionine. All had non-Hodgkin's lymphoma but one, who had Hodgkin's disease. By assuming a simple three-compartment model for dynamic data analysis, we used the graphic method proposed by Patlak et al., where Ki (K2K3/(K1+K3)) was compared with DAR (differential absorption ratio). Trichloroacetate was added to each plasma sample, and the activity of the acid-soluble fraction was counted to eliminate the influence of the protein-bound fraction of injected activity. Patlak data plots, using this acid-soluble fraction as an input factor, showed good linearity over the time of data collection. All tumors showed clear 11C-methionine accumulation. Tumor activity reached almost a plateau within 10 min and was kept at the same level for at least 30 min. Ki and DAR were 0.070 +/- 0.035 and 4.64 +/- 1.85 (mean +/- SD), respectively. There was no apparent correlation between histological type and Ki or DAR, while the correlation efficient between Ki and DAR was 0.875. Our conclusion is that DAR will give almost the same result as dynamic data in the analysis of methionine metabolism using PET.