超顺磁性氧化铁粒子增强磁共振成像在大鼠脾脏荷VX2肿瘤模型的应用(英文)

Superparamagnetic iron oxide:Enhanced detection of splenic VX2 tumor with magnetic resonance imaging in rats

背景:CT和MRI对小于1cm脾转移瘤结节的诊断的敏感度均不高,超顺磁性氧化铁粒子增强MR图像能否提高诊断敏感度有待研究。目的:建立大鼠脾脏转移瘤模型,结合特异的网状内皮系统对比剂超顺磁性氧化铁粒子行MRI扫描,探讨超顺磁性氧化铁粒子增强MR图像对脾转移瘤的诊断价值。设计:重复测量动物实验。单位:南方医科大学南方医院全军医学影像中心实验室。材料:实验于2005-05/2006-03在南方医科大学南方医院全军医学影像中心实验室完成,选用25只成年SD大鼠,雌雄不拘,体质量200～300g,实验过程中动物的处置符合动物伦理学标准。摸球法将大鼠分为肿瘤组(n=20)及空白对照组(n=5)。方法:制作脾脏荷VX2肿瘤模型鼠,注射超顺磁性氧化铁粒子后行MRI扫描,扫描序列采用T1加权成像(450/12ms)和T2加权成像(4000/128ms)。分析超顺磁性氧化铁粒子增强扫描前后MRI图像上不同组织的信号特点。空白对照组不制备模型,扫描序列与实验组相同。主要观察指标:超顺磁性氧化铁粒子增强扫描前后MRI图像上不同组织的信号特点。结果:纳入大鼠20只,肿瘤组8只死亡,其余12只与对照组5只均进入结果分析。肿瘤组行MR扫描发现有8只脾脏VX2肿瘤形成。①平扫SET1加权成像图像上正常脾实质相对于周围的肌肉及肝实质呈等信号,脾脏VX2肿瘤组织与周围的正常脾实质的信号强度对比较差,肿瘤-脾脏的对比噪声比极差,所有病灶均不能很好显示。②超顺磁性氧化铁粒子增强T2加权成像MR图像上正常脾实质信号强度与平扫时相比信号强度下降百分比为56.11%;脾脏VX2肿瘤信号强度与增强前比较无明显下降,信号强度下降百分比为1.90%,与正常脾实质的信号强度下降程度差异有显著性意义(P<0.01)。超顺磁性氧化铁粒子增强T2加权成像MR图像上脾VX2肿瘤信号强度无明显变化,而其周围正常的脾实质信号强度显著下降,脾VX2肿瘤的对比噪声比较增强前显著提高,差异有统计学意义(P<0.01)。结论:超顺磁性氧化铁粒子增强T1加权成像MR图像上正常脾实质与VX2肿瘤组织的对比差,病灶的检出率低,不利于描述病灶的特征。超顺磁性氧化铁粒子增强T2加权成像MR图像上脾脏-肿瘤的对比显著,提高了病灶的检出率,改善了病灶的影像学特征的描述。

BACKGROUND： Sensitivity of diagnoses differentiating smaller nodes of splenic metastasis （〈 1 cm） from CT and MRI is poor. So whether superparamagnetic iron oxide can enhance magnetic resonance imaging （MRI） of splenic VX2 tumor in rats need to be further studied. OBJECTIVE ： To establish splenic VX2 tumor models, investigate MRI scanning combining with superparamagnetic iron oxide of specific reticuloendothelial system, and study the diagnostic significance of superparamagnetic iron oxide-enhanced MR images on splenic metastases. DESIGN： Duplicated-measured animal study . SETTING ： Medical Imaging Center, Nanfang Hospital of the Southern Medical University MATERIALS： The experiment was carried out in the Medical Imaging Center （Military Key Laboratory）, Nanfang Hospital of the Southern Medical University from May 2005 to March 2006. A total of 25 adult SD rats, of either gender, weighing 200-300 g, were selected in this study. The animal experiment had got confirmed consent from local ethic committee. All rats were randomly divided into tumor group （n =20） and blank control group （n =5）. METHODS： Models of VX2 tumor in spleen were established successfully. The images obtained before and after administration of superparamagnetic iron oxide. Tl-weighted image（T1WI） （450/12 ms） and T2-weighted image（T2WI） （4 000/128 ms） were used to scan sequences. The imaging parameters of various tissues were analyzed before and after superparamagnetic iron oxide-enhanced MRI scanning. Rats in the blank control group were not used to establish models and the sequences were scanned as the same as those in the experimental group. MAIN OUTCOME MEASURES： Signal characteristics of various tissues before and after before and after superparamagnetic iron oxide-enhanced MRI scanning. RESULTS： Eight out of 20 rats died in the tumor group and other 12 and 5 rats in the control group were involved in the final analysis. MR scanning indicated that 8 rats in the tumor group had splenic VX2 tumor. ① On plain MR scanning Tl-weighted splenic VX2 tumor showed hypointensity or isointensity which approximated to the signal intensity （SI） of splenic parenchyma. All lesions had been not displayed well. ②On superparamagnetic iron oxide enhancement T2WI sequence the SI of splenic parachyma decreased obviously with percentage of signal intensity loss （PSIL） was 56.11%, But the SI of tumor was not evidently change with PSIL was 1.90%. Nevertheless the signal-to-noise ratio （SNR） of normal splenic parenchyma around the lesions had obviously difference （P 〈 0.001） comparatively. So the contrast between tumor and spleen increased, and tumor displayed more clear. Moreover the contrast-to-noise （CNR） between VX2 tumor and splenic parenchyma had an evidently difference with before and after admininstration of superparamagnetic iron oxide （P 〈 0.001 ）. CONCLUSION ： On superparamagnetic iron oxide enhancement T1WI sequence the contrast of tumor-to-spleen is poor. So it is not good to characterize the lesions in spleen. On superparamagnetic iron oxide enhanced T2WI the contrast degree of lesions increased obviously. Consequently, superparamagnetic iron oxide-enhanced T2WI MRI scanning can improve the rate of detection and characterization in lesions of spleen.