To systematically evaluate the consistency of various standardized uptake value (SUV) lean body mass (LBM) normalization methods in a clinical positron emission tomography/magnetic resonance imaging (PET/MR) setting.
SUV of brain, liver, prostate, parotid, blood and muscle were measured in 90 18F-FDG and 28 18F-PSMA PET/MR scans and corrected for LBM using the James, Janma (short for Janmahasatian) and Dixon models. 40 dual energy X-ray absorptiometry (DXA) measurements of non-fat mass were used as the reference standard. Agreement between different methods was assessed by linear regression and Bland-Altman statistics.
LBM fraction measured by DXA, James, Janma and Dixon approaches was 68.19±6.43%, 66.95±6.71%, 76.20±5.41% and 71.56±7.97% respectively. Compared to DXA, the Dixon approach presented the minimal bias when compared to the James and Janma models (bias: 0.76±7.35, -8.01±9.36, -3.33±8.26 respectively). SUV normalized by bodyweight (SUVbw) was positively correlated with Body Mass Index (BMI) in both FDG (liver: r=0.454, p<0.001) and PSMA studies (r=0.197,p=0.31), while SUV normalized by lean body mass (SUVlean) revealed a decreased dependency on BMI (r=0.22,0.08,0.14, p=0.04,0.46,0.18 for Dixon, James and Janma models respectively). Paired T-test showed significant difference between SUVlean of major organs measured using Dixon method vs James and Janma models.
Significant systematic variation was found among SUVlean calculated using different approaches. A consistent correction method should be applied in PET/MR serial scans.