Date Published: February 27, 2018
Publisher: Public Library of Science
Author(s): Clarice Sprinz, Stephan Altmayer, Matheus Zanon, Guilherme Watte, Klaus Irion, Edson Marchiori, Bruno Hochhegger, Kewei Chen.
To perform a systematic review of the effect of blood glucose levels on 2-Deoxy-2-[18F]fluoro-D-glucose (18F-FDG) uptake in normal organs.
We searched the MEDLINE, EMBASE and Cochrane databases through 22 April 2017 to identify all relevant studies using the keywords “PET/CT” (positron emission tomography/computed tomography), “standardized uptake value” (SUV), “glycemia,” and “normal.” Analysis followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses recommendations. Maximum and mean SUVs and glycemia were the main parameters analyzed. To objectively measure the magnitude of the association between glycemia and 18F-FDG uptake in different organs, we calculated the effect size (ES) and the coefficient of determination (R2) whenever possible.
The literature search yielded 225 results, and 14 articles met the inclusion criteria; studies included a total of 2714 (range, 51–557) participants. The brain SUV was related significantly and inversely to glycemia (ES = 1.26; R2 0.16–0.58). Although the liver and mediastinal blood pool were significantly affected by glycemia, the magnitudes of these associations were small (ES = 0.24–0.59, R2 = 0.01–0.08) and negligible (R2 = 0.02), respectively. Lung, bone marrow, tumor, spleen, fat, bowel, and stomach 18F-FDG uptakes were not influenced by glycemia. Individual factors other than glycemia can also affect 18F-FDG uptake in different organs, and body mass index appears to be the most important of these factors.
The impact of glycemia on SUVs in most organs is either negligible or too small to be clinically significant. The brain SUV was the only value largely affected by glycemia.
Radiolabelled 2-deoxy-2-[18F]fluoro-D-glucose (18F-FDG) is a widely used radiopharmaceutical for the evaluation of tumor metabolism by positron emission tomography/computed tomography (PET/CT). In clinical practice, images are analyzed qualitatively by visual comparison of the metabolism in lesions and in normal tissues, or semiquantitatively using standardized uptake values (SUVs) . 18F-FDG uptake in normal tissues is frequently adopted as an internal standard for tracer uptake, used as a reference when assessing tumor treatment response with PET .
This literature review indicated that the brain is the only organ in which hyperglycemia has a large effect on the SUV. Although the liver and mediastinal blood pool are significantly impacted by glycemia, these effects appear to be too small to be of clinical relevance. The lung, bone marrow, tumor, spleen, fat, bowel, and stomach were not found to be influenced by the plasma glucose levels. Other factors, such as BMI, age and diabetes status, were also shown to affect 18F-FDG uptake; thus, they should be taken into account in future studies of the effects of blood glucose levels on the SUVs of different organs.
This review showed that the impact of glycemia on the 18-F-FDG uptake in most tissues, except the brain, is negligible or too small to be clinically significant. Future studies should explore the use of other background tissues that are less affected by other factors, such as BMI, and seek better normalization methods for the brain.