3353. Impact of Biological and Procedural Factors on FDG PET Liver and Thigh Uptake in Children: A Retrospective Study
Authors * Denotes Presenting Author
  1. Pradipta Debnath *; Cincinnati Children’s Hospital Medical Center
  2. Andrew Trout; Cincinnati Children’s Hospital Medical Center; University of Cincinnati College of Medicine
The aim of this study was to characterize, according to patient specific factors, liver and thigh uptake of 18-F Fluorodeoxyglucose (FDG) in children and young adults undergoing Positron Emission Tomography/Computed Tomography (PET/CT).

Materials and Methods:
This IRB-approved, retrospective study included 193 whole body scans from 139 patients who underwent clinically indicated 18-F FDG PET/CT examinations. Three-dimensional spherical regions of interest (ROIs) were drawn in the liver (3 cm diameter) and in the thigh muscle (1.5 cm diameter). Activity in each ROI was recorded in Bq/mL and mean standardized uptake value (SUV) by body weight (SUV mean-bw). After 2 weeks, liver activity (Bq/mL) and activity standard deviation (SD) were remeasured. Counts, SUVs, and liver signal to noise ratio (SNR) were assessed for associations with patient-specific predictor variables using Pearson correlation and multivariable linear regression.

The mean patient age was 11.0 ± 5.4 (SD) years, mean liver SUV mean-bw was 1.17 ± 0.60 and mean liver counts was 5387 ± 1875 Bq/mL. On univariable analysis liver SUV mean-bw and liver counts were strongly correlated with weight (<em>r</em> = 0.87, <em>p</em> < 0.0001), age (<em>r</em> = 0.75, <em>p</em> < 0.0001) and total activity (<em>r</em> = 0.85, <em>p</em> < 0.0001). Mean thigh counts were significantly associated only with activity/weight (<em>r</em> = 0.37, <em>p</em> < 0.0001). On multivariable analysis, body weight and age (which is collinear with body weight) were the only significant independent predictors (<em>p</em> < 0.0001). Liver SNR was moderately associated with all predictors apart from administered activity per kilogram (<em>r</em> = 0.09, <em>p</em> = 0.23).

Liver counts on 18-F FDG PET/CT have a significant positive association with age and body weight. However, liver SNR has no significant association with administered activity per kilogram suggesting that increasing doses of FDG may not improve image quality in young children.