目的·探讨儿童与青少年在氟-18标记的氟代脱氧葡萄糖（fluorine-18 fluorodeoxyglucose，¹⁸F-FDG）正电子发射断层成像/计算机断层显像（positron emission tomography/computed tomography，PET/CT）中肝脏本底及纵隔血池的生理分布特征及影响因素。方法·收集271例<18岁的经病理确诊或怀疑恶性肿瘤的患儿病例资料，按年龄分为≤2岁组、3~5岁组、6~10岁组和≥11岁组。测量PET/CT影像中肝脏与纵隔血池的最大及平均标准化摄取值（SUV_max和SUV_mean），分析其与年龄、体质量、身高、体质量指数（body mass index，BMI）、性别、肝功能及化学治疗状态的关系。结果·肝脏SUV_max和SUV_mean分别为1.89±0.62和1.36±0.44；纵隔血池SUV_max和SUV_mean分别为1.11±0.37和0.98±0.32。Pearson相关性分析结果显示：肝脏与纵隔血池之间的SUV_max和SUV_mean均呈显著正相关（r=0.78~0.86，P<0.001），且各项SUV值均与患儿年龄、体质量、身高、BMI呈正相关（r=0.47~0.73，P<0.05）；而性别与肝脏、纵隔血池各项SUV参数间无明显相关性（r=0.02~0.04，P>0.05）。肝脏及纵隔血池FDG摄取随年龄增长而升高；肝脏SUV_max从≤2岁组的1.41±0.32升至≥11岁组的2.57±0.60（P<0.001），纵隔血池SUV_max由0.91±0.27升至1.42±0.41（P<0.001）。肝功能异常患儿的肝脏SUV_max低于肝功能正常者（1.71±0.61 vs 1.93±0.61，P=0.034），化学治疗前后差异不显著。多元回归分析结果显示，体质量和年龄是肝脏SUV值的独立影响因素（P<0.001），体质量对纵隔血池SUV值的影响最显著（P<0.001）。结论·儿童与青少年肝脏本底及纵隔血池¹⁸F-FDG摄取随年龄和体质量增长而升高，5岁以下儿童SUV值多低于2；以肝脏本底和纵隔血池SUV值作为疗效评估中的非靶器官参数，具有良好一致性和可重复性，有助于提高儿童PET/CT判读准确性与标准化。

Objective ·To investigate the physiological distribution characteristics of fluorine-18 fluorodeoxyglucose(¹⁸F-FDG) in the liver background and mediastinal blood pool on positron emission tomography/computed tomography (PET/CT) in children and adolescents, and to analyze the influencing factors. Methods ·A total of 271 pediatric patients (<18 years) with pathologically confirmed or suspected malignant tumors were retrospectively analyzed. Patients were divided into four age groups: ≤2 years, 3‒5 years, 6‒10 years, and ≥11 years. The maximum standardized uptake value and mean standardized uptake value (SUV_max and SUV_mean) of the liver and mediastinal blood pool were measured. Their associations with age, weight, height, body mass index (BMI), gender, liver function, and chemotherapy status were assessed. Results ·The SUV_max and SUV_mean of the liver were 1.89±0.62 and 1.36±0.44, respectively.The mediastinal blood pool SUV_max and SUV_mean were 1.11±0.37 and 0.98±0.32. Pearson correlation analysis showed that SUV_max and SUV_mean values of the liver and mediastinal blood pool were significantly positively correlated (r=0.78‒0.86, P<0.001). All SUV parameters were positively correlated with age, weight, height, and BMI (r=0.47‒0.73, P<0.05), but showed no significant correlation with gender (r=0.02‒0.04, P>0.05). ¹⁸F-FDG uptake in both the liver and mediastinal blood pool increased significantly with age. Hepatic SUV_max increased from 1.41±0.32 in the ≤2-year group to 2.57±0.60 in the ≥11-year group (P<0.001), while mediastinal SUV_max increased from 0.91±0.27 to 1.42±0.41 (P<0.001). Children with abnormal liver function had lower hepatic uptake compared to those with normal liver function (1.71±0.61 vs 1.93±0.61, P=0.034), while no significant difference was observed before and after chemotherapy. Multivariate regression analysis identified weight and age as independent influencing factors for hepatic SUV values (P<0.001), and body weight had the greatest impact on mediastinal blood pool SUV values (P<0.001). Conclusion ·Hepatic background and mediastinal blood pool ¹⁸F-FDG uptake increases with age and weight in children and adolescents, with SUV values typically below 2 in children under 5 years old. The SUV values of the liver and mediastinal blood pool show good consistency and reproducibility as non-target reference parameters for therapeutic response evaluation in pediatric PET/CT, which may improve the accuracy and standardization of image interpretation.