Kinetics of 11C-acetate and 18F-FDG in renal neoplasms evaluated by dual-time point PET/CT

Abstract

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Objectives: Renal tumors have different histopathological features and malignant potentials. Both 18F-FDG (FDG) and 11C-acetate (ACT) PET/CT have limited diagnostic role in renal tumors. In this study, we investigated the role of dual-tracer (DT) kinetics to differentiate renal tumors by dual-time point PET/CT.

Methods: 19 patients (10 F, 9 M; mean age: 58y) with renal tumors confirmed by pathology or clinical follow-up were recruited: 6 clear cell RCC (CCC), 2 papillary RCC (PCC), 3 chromophobe RCC (CRCC), 2 transitional cell carcinoma (TCC), 6 angiomyolipoma (AML). 4 sets of imaging were performed: early and delayed ACT PET/CT at 15 and 30 min; FDG PET/CT at 60 and 120 min. The same ROI was drawn and copied on the 4 sets of PET imaging. A simplified first order kinetic model, K1exp(-k2t), was proposed. When the kinetic model was normalized to normal kidney, 2 new parameters, K1 ratio (defined as K1*) and exp(-k2t) ratio (defined as k2*), were generated and approximated by early and delayed “SUVmax ratios of lesion to kidney.”

Results: All renal tumors except CCC had distinct characteristics (see table). PCC and TCC had similar ACT kinetics, but both FDG K1* and k2* were significantly different (P<0.05). CRCC and AML had similar DT kinetics except that their ACT k2* was significantly different. CCC patients showed little to no ACT uptake (K1*: <1 to 1.4) with variable FDG metabolism (K1*: <1 to 2.9). Two CCC were false negative by the four parameters.

Conclusions: DT PET/CT is useful in the evaluation of renal neoplasm and differentiation of individual functional constituents in relation to pathology. A negative DT dual-time point PET/CT study cannot exclude CCC.