In PET, several different Standard Uptake Value (SUV) metrics have been proposed utilizing different normalizers in an attempt to take into consideration the patient to patient differences in radionuclide uptake due to differences in body habitus (body weight, surface area, lean body mass). These normalizers are to some extent aribitrary in that they are selected from the list of proposed body habitus metrics, none of which necessarily describes well the distribution volume into which a given radionuclide labeled compound distributes with the body. 

In this work we propose a new body habitus normalizer, SUV_fdg, that is specific to the tracer ¹⁸F-FDG and which like previously proposed SUV normalizers is a simple function of a patient's height and weight. Derivation of this metric assumed that absolute normal-liver FDG uptake rate is not itself a function of body habitus (i.e. is not correlated with height, weight, etc). The SUV_fdg metric was tested in an independent cohort and shown to have little to no correlation with body habitus measures in normal liver, spleen and blood. When applied to normal brain uptake, it was shown to vary as a function of patient age.

After exclusions for type and extent of cancer and timing of the scan, a cohort of 481 patients was selected for analysis of ¹⁸F-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.