地中海贫血重度肝脏铁沉积能量CT定量研究

Using a novel iron overload.rabbit model, we have proved determine the feasibility of liver iron concentration(LIC) quantification by MRI. But we also found extremely high LIC may not be quantifiable by MRI without specialized pulse sequences designed. Is it feasibile quantificate extremely high LIC by dual energy CT(DECT) ? Because LIC is the main index to diagnosis iron overloaded thalassemia patient and to evaluate the treatment effect of iron chelator. Sigle energey CT fails to detect and quantify iron in the liver in the case of co-existing fat, which shows an inverse effect on attenuation by lowering the CT numbers. Liver biopsy can quantify extremely high LIC, but it is invasive, and can't be repeated. Through an observation study, we found that iron in the liver could be separated in the iron deposited and fatty rabbit liver by DECT scan, so it effective avoided the effect of fat composition, and there was linear correlation trend between CT numbers of virtual iron concentration (VIC) image and the actual LICs. Therefore, we speculate that material separation technology of DECT could be accurate quantitative LIC. This study aims to establish iron overloaded and fatty liver rabbit model and to explore the relationship between CT numbers of VIC image and LICs, then establish the regression equation between them. The conclusion could be applied to clinical application, through DECT quantitative extremely higher LIC, so that it is no longer blind to diagnosis and treatment patients with higher LICs, and provide a kind of accurate, noninvasive examination method.

通过建立肝铁超负荷兔模型，我们已经证明MRI可以定量肝铁浓度，但无法定量极重度肝铁沉积。那么是否可以应用双能量CT物质分离技术定量高肝铁浓度？因为肝铁含量是诊断地中海贫血患者铁负荷及去铁剂疗效评价最主要指标。单能量CT扫描测量肝脏的CT值易受脂肪等因素影响使CT值降低，不能准确定量铁浓度。肝脏穿刺可以检测高肝铁含量，但有创伤，且不能反复进行，临床难以常规检查。通过预实验我们发现双能量CT可以分离铁沉积并脂肪肝家兔的肝脏中铁成分，有效避免脂肪成分影响。虚拟铁浓度（VIC）图像CT值与实际肝铁浓度有线性相关趋势。因此，我们推测双能量CT物质分离技术可能可以准确定量肝铁浓度。本研究旨在建立铁超负荷兔模型,探讨双能量CT扫描VIC图CT值与肝铁浓度关系，建立两者之间回归方程。将得到的结论应用于临床，通过双能量CT定量肝铁浓度,从而使高肝铁含量患者的诊断及治疗不再盲目，提供一种准确、无创的检查方法。

地中海贫血尤其是重型患者需输血治疗，造成体内铁沉积，引起器官损害，而人体70%的铁沉积在肝脏，因此监测肝脏铁负荷对指导去铁药物的应用具有重要的作用。实验已经证明MRI可以测量肝铁浓度，但无法定量超过43mg Fe/g 干重的极重度肝铁沉积。近年来，已有研究表明双能量CT定量肝脏铁沉积具有可行性和准确性，但国内外尚无应用能量CT测量极重度肝铁沉积的研究。为了弥补了MRI测量重度肝铁沉积的空白，展开如下研究：.1、136只家兔随机分为6组，包括重度肝铁超负荷实验组32只及验证组16只，每周肌肉注射右旋糖酐铁；重度肝铁超负荷并脂肪肝实验组32只及验证16只，每周肌肉注射右旋糖酐铁并喂食高脂饲料；脂肪肝组32只，喂食高脂饲料；正常组8只。每周随机抽取实验组家兔2只、验证组1只、脂肪组2只、正常组每2周1只行DECT检测，测量VIC图的CT值，取肝脏标本测量肝脏铁浓度（LIC）。.2、收集β-重型地中海贫血患者47例，行DECT检查，测量VIC图的CT值，并按Ferriscan扫描标准扫描1.5T MR得到LIC。.重要结果：.1、重度肝铁超负荷实验组及重度肝铁超负荷并脂肪肝实验组VIC图CT值与LIC成正线性相关，相关系数r分别为0.979、0.963；VIC与LIC的直线回归方程为y=0.33x+0.89（F=793.0，P<0.05）、y=0.32x+0.71（F=321.2，P<0.05）。当LIC=15.0 mg Fe/g干重，VIC的CT最佳阈值为40.5HU，诊断的敏感度、特异度、AUC分别为96.15%、100.00%、0.994。LIC=43.0 mg Fe/g时,VIC CT最佳阈值为121.6HU，诊断的敏感度、特异度、AUC为92.86%、98.00%、0.989。.2、47例地中海贫血患者的VIC图CT值与LIC成正线性相关，r分别为0.825；VIC与LIC的直线回归方程为y=0.74x+6.90（F=142.4，P<0.05）。.结论：DECT的VIC图可以测量重度肝脏铁的LIC，而不受脂肪肝的影响。