Variability of Metabolic Rate and Distribution Volume Quantification in Whole-Body Parametric PATLAK [18F]-FDG PET/CT-A Prospective Trial in Patients with Lung Cancer.

Background

The recent introduction of whole-body positron emission tomography/ computed tomography (PET/CT) scanners and multi-bed, multi-time point acquisition technique enable calculating fluorodeoxyglucose (FDG) kinetics in the whole body. However, validating parametric, Patlak-derived data is difficult on phantoms.

Methods

This prospective study investigated the effect of quantification methods mean, max, and peak on the metabolic rate (MR-FDG) and distribution volume (DV-FDG) quantification, as well as the diagnostic accuracy of parametric Patlak FDG-PET scans in diagnosing lung lesions and lymph node metastases, using histopathology and follow-up as reference standards. Dynamic whole-body FDG PET was acquired for 80 minutes in 34 patients with indeterminate lung lesions and kinetic parameters extracted from lung lesions and representative mediastinal and hilar lymph nodes.

Results

All quantification methods-mean, max, and peak-demonstrated high diagnostic accuracy (AUC: MR-FDG: 0.987-0.991 and 0.893-0.905; DV-FDG: 0.948-0.975 and 0.812-0.825) for differentiating benign from malignant lymph nodes and lung lesions. Differences in the magnitude of MR-FDG (-4.76-14.09) and DV-FDG (-10.64-46.10%) were substantial across methods. Variability was more pronounced in lymph nodes (MR-FDG: 1.37-3.48) than in lung lesions (MR-FDG: 3.31-5.04). The variability was lowest between mean and max quantification, with percentage differences of 40.87 ± 5.69% for MR-FDG and 39.26 ± 7.68% for DV-FDG.

Conclusions

The choice of method to measure MR-FDG and DV-FDG greatly influences the results, especially in smaller lesions with large and systematic differences. For lung lesions, a conversion factor between mean and max methods of 40% provides acceptable agreement, facilitating retrospective comparisons of measurements, e.g., in meta-analyses.