Reliability of uptake estimates in FDG PET as a function of acquisition and processing protocols using the CPET

Abstract

Standardized uptake values (SUV) are commonly used in FDG PET to characterize suspicious high uptakes. To better understand the reliability and the limits of SUV, we studied the accuracy of uptake estimates as a function of a number of parameters using phantom data acquired on the CPET. Methods: Using the Data Spectrum thorax phantom in which spheres were inserted, we studied the effect of the sphere sizes, of out-of-the-field-of-view activity (OFOVA), of the emission scan duration and of attenuation and partial volume effect (PVE) corrections upon biases in tumor-to-normal tissue uptake ratio (TNR) estimates. Considering a specific acquisition and processing protocol as a reference, we determined the changes in TNR when modifying this protocol. Results: For a true TNR of 8, estimated TNR were strongly dependent on lesion size, but also on the acquisition and processing protocol. Depending on the method used to derive the attenuation map, estimated TNR could change by more than 50% for lung spheres less than 2 cm in diameter. Using PVE correction, TNR increased by a factor greater than 2 for spheres less than 2 cm in diameter. The very method used to estimate sphere activity from the reconstructed images could also change the TNR by more than 50%. Even with CT-based attenuation correction and PVE correction, TNR estimates remained underestimated by more than 20% in lesions less than 2 cm in diameter. Conclusion: Biases in uptake estimates strongly depend on the acquisition and processing protocols. This suggests that comparing SUV between studies make sense only if the scanner and the acquisition and processing protocols are strictly identical.

Comparative Assessment of Methods for Estimating Tumor Volume and Standardized Uptake Value in 18F-FDG PET

“…We first considered a phantom including spheres as often used to characterize the performance of tumor segmentation methods (1,5,7,29) or SUV estimation methods (17,30). However, tumors are rarely spheric, and the activity distribution in tissues is far more complex in patients than in phantoms.…”

Quantitative PET/CT Scanner Performance Characterization Based Upon the Society of Nuclear Medicine and Molecular Imaging Clinical Trials Network Oncology Clinical Simulator Phantom

“…These results should make it possible to identify and recommend make-and-model-specific reconstruction strategies to minimize measurement variability in cancer clinical trials. Mul ticenter oncology clinical trials are increasingly using PET/CT imaging as primary and secondary endpoints to define success or failure of treatment regimens, with considerable effort expended in understanding reproducibility and variability (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11). PET, as an inherently quantitative imaging technique, is arguably the most powerful imaging modality available to researchers to assess response to therapy in the multicenter clinical trial setting.…”

Cerebellum/liver index in pretherapeutic 18F-FDG PET/CT as a predictive marker of progression-free survival in follicular lymphoma treated by immunochemotherapy and rituximab maintenance

“…Our results are limited by the small sample size and will require larger studies to be confirmed. SUV might vary from one PET system to another [29] and the CLIP was calculated on 2 distinct machines in this study. There was no difference between the 2 centers in terms of CLIP measurement: the normalization of the cerebellar uptake by the hepatic SUVmean probably limited the variability of the CLIP measurements.…”