Department of Radiology, Duke University Medical Center, DUMC 3808, Durham, NC 22710, USA.
AJR Am J Roentgenol. 2010 Apr;194(4):964-71. doi: 10.2214/AJR.09.3011.
The purpose of our study was to evaluate whether two-point Dixon MRI using a 2D decomposition technique facilitates metabolite differentiation between lipids and iron in standardized in vitro liver phantoms with in vivo patient validation and allows semiquantitative in vitro assessment of metabolites associated with steatosis, iron overload, and combined disease.
The acrylamide-based phantoms were made to reproduce the T1- and T2-weighted MRI appearances of physiologic hepatic parenchyma and hepatic steatosis-iron overload by the admixture of triglycerides and ferumoxides. Combined disease was simulated using joint admixtures of triglycerides and ferumoxides at various concentrations. For phantom validation, 30 patients were included, of whom 10 had steatosis, 10 had iron overload, and 10 had no liver disease. For MRI an in-phase/opposed-phase T1-weighted sequence with TR/TE(opposed-phase)/TE(in-phase) of 4.19/1.25/2.46 was used. Fat/water series were obtained by Dixon-based algorithms. In-phase and opposed-phase and fat/water ratios were calculated. Statistical cluster analysis assessed ratio pairs of physiologic liver, steatosis, iron overload, and combined disease in 2D metabolite discrimination plots.
Statistical assessment proved that metabolite decomposition in phantoms simulating steatosis (1.77|0.22; in-phase/opposed-phase|fat/water ratios), iron overload (0.75|0.21), and healthy control subjects (1.09|0.05) formed three clusters with distinct ratio pairs. Patient validation for hepatic steatosis (3.29|0.51), iron overload (0.56|0.41), and normal control subjects (0.99|0.05) confirmed this clustering (p < 0.001). One-dimensional analysis assessing in vitro combined disease only with in-phase/opposed-phase ratios would have failed to characterize metabolites. The 2D analysis plotting in-phase/opposed-phase and fat/water ratios (2.16|0.59) provided accurate semiquantitative metabolite decomposition (p < 0.001).
MR Dixon imaging facilitates metabolite decomposition of intrahepatic lipids and iron using in vitro phantoms with in vivo patient validation. The proposed decomposition technique identified distinct in-phase/opposed-phase and fat/water ratios for in vitro steatosis, iron overload, and combined disease.
本研究旨在评估使用二维分解技术的两点 Dixon MRI 是否有助于在具有体内患者验证的标准化体外肝脏模型中区分脂质和铁的代谢物，并允许对与脂肪变性、铁过载和合并疾病相关的代谢物进行半定量的体外评估。
使用丙烯酰胺基模型来模拟生理肝实质和肝脂肪变性-铁过载的 T1 和 T2 加权 MRI 外观，通过混合甘油三酯和铁氧化物来实现。通过混合不同浓度的甘油三酯和铁氧化物来模拟合并疾病。对于模型验证，纳入了 30 名患者，其中 10 名患有脂肪变性，10 名患有铁过载，10 名无肝脏疾病。使用 T1 加权的同相位/反相位序列，TR/TE（反相位）/TE（同相位）为 4.19/1.25/2.46。通过 Dixon 算法获得脂肪/水系列。计算同相位和反相位以及脂肪/水比值。统计聚类分析评估生理肝脏、脂肪变性、铁过载和合并疾病在二维代谢物区分图中的比值对。
统计评估证明，模拟脂肪变性（1.77|0.22；同相位/反相位|脂肪/水比值）、铁过载（0.75|0.21）和健康对照（1.09|0.05）的模型中的代谢物分解形成了三个具有明显比值对的聚类。对肝脂肪变性（3.29|0.51）、铁过载（0.56|0.41）和正常对照（0.99|0.05）的患者验证证实了这一聚类（p<0.001）。仅使用同相位/反相位比值的一维分析评估体外合并疾病将无法对代谢物进行特征描述。绘制同相位/反相位和脂肪/水比值的二维分析（2.16|0.59）提供了准确的半定量代谢物分解（p<0.001）。
MR Dixon 成像使用具有体内患者验证的体外模型促进了肝内脂质和铁的代谢物分解。所提出的分解技术为体外脂肪变性、铁过载和合并疾病确定了独特的同相位/反相位和脂肪/水比值。
