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人体内脂肪组织分为白色脂肪组织(white adipose tissue,WAT)与棕色脂肪组织(brown adipose tissue,BAT)2种类型,WAT主要以三酰甘油的形式起保温和储存能量的作用;BAT可通过非战栗方式产热,是人体适应性产热的主要部位,也是目前研究代谢性疾病和肥胖的靶点[1-2]。在PET显像中,3.6%~9.1%的成年人的BAT可高摄取18F-FDG而显影[3-4]。成年人的BAT主要分布于锁骨上区、颈部、椎旁、纵隔及肾周区域[5],这些亦是肿瘤淋巴结转移的好发部位。18F-FDG PET/MRI和18F-FDG PET/CT在肿瘤的诊断、分期及疗效评价方面有重要作用,BAT的生理性摄取对二者的影像诊断均可产生不同程度的干扰。已有研究者对PET/CT显像中BAT摄取的影像学特点及规律进行了分析总结[6-7],但关于PET/MRI中BAT摄取特点的报道较少。本研究初步探讨18F-FDG PET/MRI中BAT摄取的规律和影像学表现。
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31名BAT摄取18F-FDG阳性者的PET/MRI图像表现为颈部、锁骨上区、纵隔、脊柱两旁及肾上区等部位呈对称性分布的片状、结节状及串珠状的18F-FDG高摄取灶,MRI图像的T1WI、T2WI均呈高信号,SPAIR呈低信号(图1),DWI图像未见高信号。双侧颈部、锁骨上区摄取者30名(96.8%,30/31),脊柱两旁摄取者21名(67.7%,21/31),纵隔摄取者9名(29.0%,9/31),双侧肾上区摄取者5名(16.1%,5/31)。31名出现1~5个部位摄取的受检者数依次为2名(6.4%)、8名(25.8%)、11名(35.5%)、6名(19.4%)、4名(12.9%)。
图 1 18F-FDG PET/MRI显像中棕色脂肪组织的摄取图 受检者女性,29岁,因血清糖类抗原724升高行PET/MRI检查。A为最大密度投影,可见双侧颈部及锁骨上区对称性分布串珠状18F-FDG摄取增高灶;B为PET横断面,可见双侧锁骨上区对称性分布片状、结节状18F-FDG摄取增高灶,SUVmax=9.7;C为T1WI横断面,可见对应位置T1WI呈高信号;D为T2WI横断面,可见对应位置T2WI呈高信号;E为SPAIR横断面,可见对应位置SPAIR呈低信号;F为SPAIR与PET融合显像横断面,可见18F-FDG高代谢部位SPAIR呈低信号,局部未见肿大淋巴结。FDG为氟脱氧葡萄糖;PET为正电子发射断层显像术;MRI为磁共振成像;SUVmax为最大标准化摄取值;WI为加权成像;SPAIR为频率衰减反转恢复序列
Figure 1. Image of 18F-FDG uptake in brown adipose tissue by PET/MRI
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男性和女性BAT摄取18F-FDG的阳性率分别为1.6%(13/836)和2.6%(18/693),差异无统计学意义(χ2=2.07,P=0.15)。BAT摄取18F-FDG阳性者的年龄[(33.3±11.7)岁]低于阴性者[(54.1±13.5)岁],差异有统计学意义(t=−12.03,P<0.001);BAT摄取18F-FDG阳性者的BMI[(21.89±2.79) kg/m2]低于阴性者[(24.01±3.26 ) kg/m2],差异有统计学意义(t=−5.15,P<0.001)。BAT摄取18F-FDG阳性者检查当日的气温[(7.5±6.5 )℃]低于阴性者[(16.5±11.9)℃],差异有统计学意义(t=−8.97,P<0.001)。31名BAT摄取18F-FDG阳性者按检查月份1~12月的人数分布依次为5、4、2、2、1、0、0、0、0、4、6、7名,多分布于冬、春季节。
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31名BAT摄取18F-FDG阳性者的SUVmax为7.49±3.62(2.82~17.60)、SUVmean为2.92±1.53(0.91~6.47),将SUVmax和SUVmean分别与性别、年龄、BMI、检查当日平均气温及摄取部位BAT数量进行相关性分析,由表1可知,SUVmax和SUVmean均与摄取部位数量呈正相关(均P<0.001);与年龄和BMI呈负相关(均P<0.05);与性别及检查当日平均气温无明显相关性(均P>0.05)。
影响因素 (范围)$\bar x\pm s $ SUVmax SUVmean r值 P值 r值 P值 性别(男/女) − 0.07 0.69 0.01 0.93 年龄(岁) 33.3±11.7(16~61) −0.45 0.01 −0.41 0.02 体重指数(kg/m2) 21.89±2.79(15.50~26.45) −0.36 0.04 −0.40 0.02 检查当日气温(℃) 7.5±6.5(−4~19) 0.29 0.11 0.09 0.61 摄取部位数量(个) 2.9±1.5(1~5) 0.61 <0.001 0.59 <0.001 注:FDG为氟脱氧葡萄糖;PET为正电子发射断层显像术;MRI为磁共振成像;SUVmax为最大标准化摄取值;SUVmean为平均标准化摄取值。−表示无此项数据 表 1 31名棕色脂肪组织摄取18F-FDG阳性者PET/MRI显像的SUVmax和SUVmean与各因素的相关性分析
Table 1. Correlation analysis between maximum standard uptake value and mean standard uptake value by PET/MRI and various factors in 31 subjects with 18F-FDG uptake in brown adipose tissue
18F-FDG PET/MRI中棕色脂肪组织摄取的影像学表现和规律分析
Imaging characteristics and patterns of brown adipose tissues by 18F-FDG PET/MRI
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摘要:
目的 研究并分析18F-氟脱氧葡萄糖(FDG)PET/MRI中棕色脂肪组织(BAT)摄取的影像学表现和规律。 方法 回顾性分析2017年7月至2020年1月于空军军医大学第二附属医院行18F-FDG PET/MRI检查的1 529名受检者的影像学资料和临床资料,其中男性836名、女性693名,年龄14~93(53.6±13.2)岁;BAT摄取18F-FDG阳性者31名,其中男性13名、女性18名,年龄16~61(33.3±11.6)岁。分析BAT摄取18F-FDG的PET/MRI影像学表现,选取18F-FDG摄取增高部位[以周围肌肉组织的最大标准化摄取值(SUVmax)为临界值],采用三维勾画法勾画感兴趣区,计算SUVmax和平均标准化摄取值(SUVmean)。SUVmax和SUVmean与性别及摄取部位数目的相关性采用Spearman相关性分析,与年龄、体重指数(BMI)、检查当日平均气温的相关性采用Pearson相关性分析。组间计数资料的比较采用χ2检验;计量资料的比较采用独立样本t检验。 结果 (1)BAT摄取18F-FDG阳性者的PET/MRI图像表现为颈部、锁骨上区、纵隔、脊柱两旁及肾上区等部位呈对称性分布的片状、结节状及串珠状的18F-FDG高摄取灶,MRI图像的T1加权成像(WI)、T2WI均呈高信号,频率衰减反转恢复序列呈低信号,弥散加权成像未见高信号。(2)BAT摄取多发生于寒冷的季节,男性和女性BAT摄取18F-FDG的阳性率差异无统计学意义(χ2=2.07,P=0.15);BAT摄取18F-FDG阳性者的年龄、BMI和检查当日气温均明显低于阴性者[(33.3±11.7)岁对( 54.1±13.5)岁、(21.89±2.79) kg/m2对(24.01±3.26) kg/m2、(7.5±6.5)℃对(16.5±11.9)℃],且差异均有统计学意义(t=−12.03、−5.15、−8.97,均P<0.001)。(3)BAT摄取的SUVmax和SUVmean均与年龄、BMI呈负相关(r=−0.45~−0.36,均P<0.05),与摄取BAT部位数量呈正相关(r=0.61、0.59,均P<0.001),与性别和检查当日平均气温均无明显相关性(r=0.01~0.29,均P>0.05)。 结论 在18F-FDG PET/MRI显像中,BAT摄取存在特定的影像学表现和规律性,大多发生在寒冷的季节,年轻、偏瘦者较易出现。 -
关键词:
- 脂肪组织,棕色 /
- 正电子发射断层显像术 /
- 磁共振成像 /
- 氟脱氧葡萄糖F18
Abstract:Objective To investigate and analyze the imaging manifestations and rules of brown adipose tissue (BAT) uptake in 18F-fluorodeoxyglucose (FDG) PET/MRI. Methods The imaging and clinical data of 1 529 subjects (836 males and 693 females, aged 14–93(53.6±13.2) years) who underwent 18F-FDG PET/MRI examination in the Second Affiliated Hospital of Air Force Medical University from July 2017 to January 2020 were analyzed retrospectively. Thirty-one subjects, including 13 males and 18 females aged 16–61 (33.3±11.6) years, had positive BAT uptake of 18F-FDG. The PET/MRI imaging features of 18F-FDG uptake of BAT were analyzed, and three-dimensional sketching was adopted to select sites with increased 18F-FDG uptake to delineate the region of interest (with the maximum standardized uptake value (SUVmax) of surrounding muscles as the boundary value). SUVmax and the mean standardized uptake value (SUVmean) were calculated automatically by the software program. The correlation between SUVmax and SUVmean with variable factors(eg. gender, age, body mass index (BMI), mean temperature on the examination day and number of ingestion sites) were evaluated by Spearman or Pearson correlation analysis. Count data between groups was compared by χ2 test. Measurement data were compared by independent sample t test. Results (1) The PET/MRI images of subjects with positive BAT uptake of 18F-FDG showed symmetrical flaky, nodular and bead uptake in sucravicula, cervical regions, and paravertebral, mediastinal, and perirenal mediastinum. T1-weighted imaging (WI) and T2WI of the MRI images showed high signal. The frequency attenuation inversion recovery sequence showed low signal. The diffusion weighted imaging showed no high signal. (2) Most BAT uptake occurred in cold periods, and no significant difference was found in the positive rate of BAT uptake between males and females (χ2=2.07, P=0.15). The age, BMI, and the temperature on the day of examination of the subjects with positive uptake of BAT were significantly lower than those with negative uptake ((33.3±11.7) years vs. (54.1±13.5) years, (21.89±2.79) kg/m2 vs. (24.01±3.26) kg/m2, (7.5±6.5)℃ vs. (16.5±11.9)℃), and the differences were statistically significant (t=−12.03, −5.15, −8.97; all P<0.001). (3) SUVmax and SUVmean of BAT were negatively correlated with age and BMI (r=−0.45 to −0.36; all P<0.05) but positively correlated with the number of BAT depots (r=0.61, 0.59; both P<0.001). SUVmax and SUVmean of BAT had no significant correlation with gender or the average temperature on the day of examination (r=0.01−0.29; all P>0.05). Conclusion In 18F-FDG PET/MRI imaging, BAT uptake has specific imaging manifestations and regularity, which mostly occurs in cold season and is more likely to occur in young and low-BMI subjects. -
图 1 18F-FDG PET/MRI显像中棕色脂肪组织的摄取图 受检者女性,29岁,因血清糖类抗原724升高行PET/MRI检查。A为最大密度投影,可见双侧颈部及锁骨上区对称性分布串珠状18F-FDG摄取增高灶;B为PET横断面,可见双侧锁骨上区对称性分布片状、结节状18F-FDG摄取增高灶,SUVmax=9.7;C为T1WI横断面,可见对应位置T1WI呈高信号;D为T2WI横断面,可见对应位置T2WI呈高信号;E为SPAIR横断面,可见对应位置SPAIR呈低信号;F为SPAIR与PET融合显像横断面,可见18F-FDG高代谢部位SPAIR呈低信号,局部未见肿大淋巴结。FDG为氟脱氧葡萄糖;PET为正电子发射断层显像术;MRI为磁共振成像;SUVmax为最大标准化摄取值;WI为加权成像;SPAIR为频率衰减反转恢复序列
Figure 1. Image of 18F-FDG uptake in brown adipose tissue by PET/MRI
表 1 31名棕色脂肪组织摄取18F-FDG阳性者PET/MRI显像的SUVmax和SUVmean与各因素的相关性分析
Table 1. Correlation analysis between maximum standard uptake value and mean standard uptake value by PET/MRI and various factors in 31 subjects with 18F-FDG uptake in brown adipose tissue
影响因素 (范围)$\bar x\pm s $ SUVmax SUVmean r值 P值 r值 P值 性别(男/女) − 0.07 0.69 0.01 0.93 年龄(岁) 33.3±11.7(16~61) −0.45 0.01 −0.41 0.02 体重指数(kg/m2) 21.89±2.79(15.50~26.45) −0.36 0.04 −0.40 0.02 检查当日气温(℃) 7.5±6.5(−4~19) 0.29 0.11 0.09 0.61 摄取部位数量(个) 2.9±1.5(1~5) 0.61 <0.001 0.59 <0.001 注:FDG为氟脱氧葡萄糖;PET为正电子发射断层显像术;MRI为磁共振成像;SUVmax为最大标准化摄取值;SUVmean为平均标准化摄取值。−表示无此项数据 -
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