Schwenzer Nina F, Machann Jürgen, Martirosian Petros, Stefan Norbert, Schraml Christina, Fritsche Andreas, Claussen Claus D, Schick Fritz
Section on Experimental Radiology, Department of Diagnostic Radiology, Eberhard-Karls University, Tübingen, Germany.
Invest Radiol. 2008 May;43(5):330-7. doi: 10.1097/RLI.0b013e31816a88c6.
The goal of the present study was the assessment of pancreatic and hepatic fat content applying 2 established magnetic resonance (MR) imaging techniques: in-phase/opposed-phase gradient-echo MR imaging and fat-selective spectral-spatial gradient-echo imaging. Results of both approaches were compared, and influences of T1- and T2*-related corrections were assessed. The possibility of a correlation between pancreatic lipomatosis and liver steatosis was investigated.
Seventeen volunteers at risk for type 2 diabetes (6 male, 11 female; age, 26-70 years; body mass index, 19.4-41.3 kg/m2; mean, 31.7 kg/m2) were examined. Liver and pancreas fat content were quantified with 2 different gradient-echo techniques: one uses a spectral-spatial excitation technique with 6 binomial radio frequency pulses, which combines chemical shift selectivity with simultaneous slice-selective excitation. The other technique based on double-echo chemical shift gradient-echo MR provides in- and opposed-phase images simultaneously. Influences of T1 and individual T2* effects on results using in-phase/opposed-phase imaging were estimated and corrected for, based on additional T2* measurements.
The fat content calculated from images recorded with the fat-selective spectral-spatial gradient-echo sequence correlated well with the fat fraction determined with in-phase/opposed-phase imaging and following correction for T1/T2* effects: pancreas r = 0.93 (P < 0.0001) and liver r = 0.96 (P < 0.0001). In-phase/opposed-phase imaging revealed a pancreatic fat content between 1.6% and 22.2% (mean, 8.8% +/- 5.7%) and a hepatic fat fraction between 0.6% and 33.3% (mean, 7.9% +/- 9.1%). The fat-selective spectral-spatial gradient-echo sequence revealed a pancreatic lipid content between 3.4% and 16.1% (mean, 9.8% +/- 4.0%) and a hepatic fat content between 0% and 28.5% (mean, 8.8% +/- 8.3%). With neither technique was a substantial correlation between pancreatic and hepatic fat content found.
The presented results suggest that both methods are reliable tools for pancreatic and hepatic fat quantification. However, for reliable assessment of quantitative fat by the in-phase/opposed-phase technique, an additional measurement of T2* seems crucial.
本研究的目的是应用两种既定的磁共振(MR)成像技术评估胰腺和肝脏脂肪含量:同相位/反相位梯度回波MR成像和脂肪选择性频谱空间梯度回波成像。比较了两种方法的结果,并评估了T1和T2*相关校正的影响。研究了胰腺脂肪瘤病与肝脂肪变性之间相关性的可能性。
对17名有2型糖尿病风险的志愿者(6名男性,11名女性;年龄26 - 70岁;体重指数19.4 - 41.3kg/m²;平均31.7kg/m²)进行检查。使用两种不同的梯度回波技术对肝脏和胰腺脂肪含量进行量化:一种使用具有6个二项式射频脉冲的频谱空间激发技术,该技术将化学位移选择性与同时的层面选择激发相结合。另一种基于双回波化学位移梯度回波MR的技术可同时提供同相位和反相位图像。基于额外的T2测量,估计并校正了T1和个体T2效应在使用同相位/反相位成像时对结果的影响。
由脂肪选择性频谱空间梯度回波序列记录的图像计算出的脂肪含量与通过同相位/反相位成像并校正T1/T2*效应后确定的脂肪分数具有良好的相关性:胰腺r = 0.93(P < 0.0001),肝脏r = 0.96(P < 0.0001)。同相位/反相位成像显示胰腺脂肪含量在1.6%至22.2%之间(平均8.8%±5.7%),肝脏脂肪分数在0.6%至33.3%之间(平均7.9%±9.1%)。脂肪选择性频谱空间梯度回波序列显示胰腺脂质含量在3.4%至16.1%之间(平均9.8%±4.0%),肝脏脂肪含量在0%至28.5%之间(平均8.8%±8.3%)。两种技术均未发现胰腺和肝脏脂肪含量之间存在显著相关性。
所示结果表明,两种方法都是用于胰腺和肝脏脂肪定量的可靠工具。然而,对于通过同相位/反相位技术可靠地评估定量脂肪,额外测量T2*似乎至关重要。