Comparative test-retest variability of outcome parameters derived from brain [18F]FDG PET studies in non-human primates

Abstract

Introduction Knowledge of the repeatability of quantitative parameters derived from [ 18 F]FDG PET images is essential to define the group size and allow correct interpretation. Here we tested repeatability and accuracy of different [ 18 F]FDG absolute and relative quantification parameters in a standardized preclinical setup in nonhuman primates (NHP). Material and methods Repeated brain [ 18 F]FDG scans were performed in 6 healthy NHP under controlled experimental factors likely to account for variability. Regional cerebral metabolic rate of glucose (CMRglu) was calculated using a Patlak plot with blood input function Semi-quantitative approaches measuring standard uptake values (SUV, SUV×glycemia and SUVR (SUV Ratio) using the pons or cerebellum as a reference region) were considered. Test-retest variability of all quantification parameters were compared in different brain regions in terms of absolute variability and intra-and-inter-subject variabilities. In an independent [ 18 F]FDG PET experiment, robustness of these parameters was evaluated in 4 naive NHP. Results Experimental conditions (injected dose, body weight, animal temperature) were the same at both imaging sessions (p >0.4). No significant difference in the [ 18 F]FDG quantification parameters was found between test and retest sessions. Absolute variability of CMRglu, SUV, SUV×glycemia and normalized SUV ranged from 25 to 43%, 16 to 21%, 23 to 28%, and 7 to 14%, respectively. Intra-subject variability largely explained the absolute variability of all quantitative parameters. They were all significantly correlated to each other and they were all robust. Arterial and venous glycemia were highly correlated (r = 0.9691; p<0.0001).

Performance evaluation of the IRIS XL-220 PET/CT system, a new camera dedicated to non-human primates

“…Because a fair comparison of new preclinical PET systems based on NEMA standard evaluations has been questioned [ 26 ], we further studied the performances of the IRIS XL-220 PET system in real conditions using two distinct radiotracers. The images obtained from the 18 F-FDG and (-)-[ 18 F]FEOBV experiments on NHP were consistent with previous reports, with (-)-[ 18 F]FEOBV binding corresponding to the biodistribution of the vesicular acetylcholine transporter [ 20 , 27 , 28 ]. This revealed that the IRIS XL-220 PET provided an excellent quality of images in NHP, but also in rats based on the spatial resolution of the system.…”

SARS-CoV-2 causes brain inflammation and induces Lewy body formation in macaques

“…In humans and macaques, the volume of the pituitary gland is small, and under physiological conditions, its metabolic activity is comparable to the background level of the entire brain (16, 17) . The 18 F-FDG uptake of the pituitary gland may even be underestimated due to the partial-volume-effects that affect the emission signal recovery (16) .…”

“…The analysis was performed in VivoQuant 4.5 (Invicro, Boston, USA). Based on repeatability parameters for correct interpretation of the results, a standardized uptake value (SUV) ratio was used for robustness (17, 42) . An increased uptake, and pituitary gland hypermetabolism is defined as a SUV mean ratio above 1.5 for the pituitary gland over the surrounding brain in combination with a SUV peak ratio above background levels (>1.0).…”

“…In humans and macaques, the volume of the pituitary gland is small, and under physiological conditions its metabolic activity is comparable to the background level of the entire brain (16,17).…”

Cerebral glucose changes after chemotherapy and their relation to long-term cognitive complaints and fatigue

“…However, when normalizing values to a (pseudo-reference) region, we were unable to identify whether regional hypo/hypermetabolism truly reflects decreased/increased metabolism or is driven by absolute metabolic changes in the surrounding GM regions. Although methods exist to approach absolute quantification ( 55 ) (e.g., determining plasma kinetics with an arterial-plasma input function), they are invasive and unnecessary in clinical examinations. Third, since no MR data were available, we were unable to perform partial volume correction, which may have influenced our results, especially by chemotherapy-induced volumetric effects or aging in longitudinal follow-up ( 40 , 56 ).…”