Abstract PurposeTo devise a new body-habitus normalizer to be used in the calculation of a standardized uptake value (SUV) that is specific to the PET tracer 18 F-FDG. MethodsAfter exclusions for type and extent of cancer and timing of the scan, a cohort of 481 patients was selected for analysis of 18 F-FDG uptake into “normal” tissues (presumed to be unaffected by their disease). Among these, 65 patients had only brain concentrations measured and the remaining 416 were randomly divided into an 86-patient test set and a 330-patient training set. Within the test set, normal liver, spleen and blood measures were made. In the training set, only normal liver concentrations were measured. Using data from the training set, a simple polynomial function of height and weight was selected (following a subjective procedure) to predict each patient’s mean liver percent injected dose per milliliter. This function, when used to normalize measured %ID/ml concentrations, defines a new SUV metric (SUV fdg ) which we compared to SUV metrics normalized by body weight (SUV bw ), lean-body mass (SUV lbm ) and body surface-area (SUV bsa ) in a five-fold cross-validation. SUV fdg was also tested on the independent holdout sets utilizing the measurements of normal liver, blood, spleen and brain. ResultsFor patients of all sizes including pediatric patients, the normal range of liver 18 F-FDG uptake concentration at 60 minutes post injection in units of SUV fdg is 1.0 ± 0.16. Liver, blood and spleen SUV fdg in all comparisons had lower coefficients of variation (CoV) compared to SUV bw SUV lbm and SUV bsa . Blood had a mean SUV fdg value of 0.8 ± 0.11 and showed no correlation with age, height or weight. Brain SUV fdg measures were significantly higher (P<0.01) in pediatric patients (4.7 ± 0.9) compared to adults (3.1 ± 0.6). ConclusionA new SUV metric, SUV fdg , is proposed. It is hoped that SUV fdg will prove to be better at classifying tumor lesions and other tissues compared to SUV metrics in current use and may be useful in predicting patient specific radiation dose. Other tracers may benefit from similarly tracer-specific body habitus normalizers.