Evaluation of CT-based SUV normalization.

The purpose of this study was to determine patients’ lean body mass (LBM) and lean tissue (LT) mass using a computed tomography (CT)-based method, and to compare standardized uptake value (SUV) normalized by these parameters to conventionally normalized SUVs. Head-to-toe positron emission tomography (PET)/CT examinations were retrospectively retrieved and semi-automatically segmented into tissue types based on thresholding of CT Hounsfield units (HU). The following HU ranges were used for determination of CT-estimated LBM and LT (LBM_CT and LT_CT):  −180 to  −7 for adipose tissue (AT), −6 to 142 for LT, and 143 to 3010 for bone tissue (BT). Formula-estimated LBMs were calculated using formulas of James (1976 Research on Obesity: a Report of the DHSS/MRC Group (London: HMSO)) and Janmahasatian et al (2005 Clin. Pharmacokinet. 44 1051–65), and body surface area (BSA) was calculated using the DuBois formula (Dubois and Dubois 1989 Nutrition5 303–11). The CT segmentation method was validated by comparing total patient body weight (BW) to CT-estimated BW (BW_CT). LBM_CT was compared to formula-based estimates (LBM_James and LBM_Janma). SUVs in two healthy reference tissues, liver and mediastinum, were normalized for the aforementioned parameters and compared to each other in terms of variability and dependence on normalization factors and BW. Comparison of actual BW to BW_CT shows a non-significant difference of 0.8 kg. LBM_James estimates are significantly higher than LBM_Janma with differences of 4.7 kg for female and 1.0 kg for male patients. Formula-based LBM estimates do not significantly differ from LBM_CT, neither for men nor for women. The coefficient of variation (CV) of SUV normalized for LBM_James (SUV_LBM-James) (12.3%) was significantly reduced in liver compared to SUV_BW (15.4%). All SUV variances in mediastinum were significantly reduced (CVs were 11.1–12.2%) compared to SUV_BW (15.5%), except SUV_BSA (15.2%). Only SUV_BW and SUV_LBM-James show independence from normalization factors. LBM_James seems to be the only advantageous SUV normalization. No advantage of other SUV normalizations over BW could be demonstrated. [ABSTRACT FROM AUTHOR]