Abstract
PurposeTo 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.MethodsSUV 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 approaches. The prospective study was performed from December 2018 to August 2020 at Shanghai East Hospital. Forty dual energy X-ray absorptiometry (DXA) measurements of non-fat mass were used as the reference standard. Agreement between different LBM methods was assessed by linear regression and Bland-Altman statistics. SUV’s dependency on BMI was evaluated by means of linear regression and Pearson correlation.ResultsCompared to DXA, the Dixon approach presented the least bias in LBM/weight% than James and Janma models (bias 0.4±7.3%, − 8.0±9.4%, and − 3.3±8.3% respectively). SUV normalized by body weight (SUVbw) was positively correlated with body mass index (BMI) for both FDG (e.g., liver: r = 0.45, p < 0.001) and PSMA scans (r = 0.20, 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). The liver SUVbw of obese/overweight patients was significantly larger (p < 0.001) than that of normal patients, whereas the bias was mostly eliminated in SUVlean. One-way ANOVA showed significant difference (p < 0.001) between SUVlean in major organs measured using Dixon method vs James and Janma models.ConclusionSignificant systematic variation was found using different approaches to calculate SUVlean. A consistent correction method should be applied for serial PET/MR scans. The Dixon method provides the most accurate measure of LBM, yielding the least bias of all approaches when compared to DXA.
Highlights
The unique benefits of integrated positron emission tomography/magnetic resonance imaging (PET/MR), including comprehensive contrast mechanisms and seamless fusion of morphology and function, are driving adoption and exploration in both the clinical and research domains
standardized uptake value (SUV) normalized to body weight (SUVbw) is the most popular metric in today’s clinical setting, Zasadny and Wahl found that it is highly dependent on patient weight and body fat content [5]
The Kolmogorov-Smirnov test (KS test) showed that the lean body mass (LBM) fraction calculated using Dixon, James, Janma, and dual energy X-ray absorptiometry (DXA) as well as the body mass index (BMI) and SUV values all followed normal distribution
Summary
The unique benefits of integrated positron emission tomography/magnetic resonance imaging (PET/MR), including comprehensive contrast mechanisms and seamless fusion of morphology and function, are driving adoption and exploration in both the clinical and research domains. Patients might present dramatic physiological variation in terms of body weight throughout the course of treatment, requiring serial PET scans to maintain high standards for consistent and accurate quantitation [3]. Many studies have investigated methods to improve normalization factors of SUV to account for more consistent quantitation across a wide range of body mass indices (for example, BMI = weight/height). The most widely adopted approach is to use lean body mass (LBM) instead of body weight to offset the systematic bias caused by white adipose tissue [5]. This corrected SUV is often referred to as SUVlean or SUL. SUVlean has been recommended by PERCIST and has been widely accepted in clinical and research studies [6, 7]
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