Comparison of SUVs Normalized by Lean Body Mass Determined by CT with Those Normalized by Lean Body Mass Estimated by Predictive Equations in Normal Tissues

Purpose: Standardized uptake values (SUVs) normalized by lean body mass (LBM) determined by CT were compared with those normalized by LBM estimated using predictive equations (PEs) in normal liver, spleen, and aorta using (18)F-FDG PET/CT.

Methods: Fluorine-18 fluorodeoxyglucose (F-FDG) positron emission tomography/computed tomography (PET/CT) was conducted on 453 patients. LBM determined by CT was defined in 3 ways (LBMCT1-3). Five PEs were used for comparison (LBMPE1-5). Tissue SUV normalized by LBM (SUL) was calculated using LBM from each method (SULCT1-3, SULPE1-5). Agreement between methods was assessed by Bland-Altman analysis. Percentage difference and percentage error were also calculated.

Results: For all liver SULCTs vs. liver SULPEs except liver SULPE3, the range of biases, SDs of percentage difference and percentage errors were -0.17-0.24 SUL, 6.15-10.17 %, and 25.07- 38.91 %, respectively. For liver SULCTs vs. liver SULPE3, the corresponding figures were 0.47-0.69 SUL, 10.90-11.25 %, and 50.85-51.55 %, respectively, showing the largest percentage errors and positive biases. Irrespective of magnitudes of the biases, large percentage errors of 25.07-51.55 % were observed between liver SULCT1-3 and liver SULPE1-5. The results of spleen and aorta SULCTs and SULPEs comparison were almost identical to those for liver.

Conclusion: The present study demonstrated substantial errors in individual SULPEs compared with SULCTs as a reference value. Normalization of SUV by LBM determined by CT rather than PEs may be a useful approach to reduce errors in individual SULPEs.