Imaging of macrophages in soft-tissue infection in rats: Relationship between ultrasmall superparamagnetic iron oxide dose and MR signal characteristics
Imaging of macrophages in soft-tissue infection in rats: Relationship between ultrasmall superparamagnetic iron oxide dose and MR signal characteristics
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DOI：
10.1148/radiol.2343031172
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发表时间：
2005-03-01
期刊：
影响因子：
19.7
通讯作者：
Kaim, AH
中科院分区：
文献类型：
--
作者：
Lutz, AM;Weishaupt, D;Kaim, AH
目得：描述超小超顺磁性氧化铁（USPIO）给药后24小时获得的1.5 T T1和T2* 加权磁共振（MR）图像上实验诱导的软组织肿胀的剂量依赖性信号强度（SI）特征，并描述51与USPIO摄取量和巨噬细胞铁含量之间的关系。动物护理的当地机构审查委员会批准了实验，这些实验根据国立卫生研究院和我们机构的动物研究委员会的指导方针进行。在21只大鼠中注射金黄色葡萄球菌悬液诱导单侧小腿肌肉肿胀。将大鼠分为三组，每组7只动物：低USPIO剂量（50 μ mol铁/kg体重），高USPIO剂量（150 μ mol Fe/kg）和对照（盐水溶液）。所有大鼠在USPIO给药前和给药后24小时在1.5 T下成像（横向T1加权自旋回波、T2* 加权快速梯度回波和短反转时间反转恢复序列）。图像进行定量和定性分析方面的SI和信号模式。使用Wilcoxon符号秩检验分析计算的对比噪声比的时间变化。MR结果与组织病理学结果相关，包括电子显微镜检查结果。结果：24小时后，USPIO管理高剂量组，敏感性影响存在于脓肿周边的对比后T2* 加权图像（P = 0.04），并注意到增强后T1加权图像脓肿壁和脓肿中心（P = 0.04）。在低剂量组中，在T1加权增强后图像上整个脓肿中观察到SI增强（P = .03）。在增强后T2* 加权图像上，在任何脓肿的周边或中心均未检测到显著的S1丢失（P = 0.09）或易感性效应。各组间巨噬细胞的总量无明显差异，但USPIO剂量组之间的铁阳性巨噬细胞的个体铁含量有明显差异。结论：在1.5 T时，USPIO注射后24小时获得的T1和T2* 加权图像上的S1特征强烈依赖于造影剂的给药剂量。在低剂量下，T1效应强于T2* 效应。(C)RSNA 2005
PURPOSE: To describe dose-dependent signal intensity (SI) characteristics of experimentally induced soft-tissue abscesses on 1.5-T T1 and T2*-weighted magnetic resonance (MR) images obtained 24 hours after administration of ultrasmall superparamagnetic iron oxide (USPIO) and to describe the relationship between 51 and amount of USPIO uptake and macrophage iron content.MATERIALS AND METHODS: Local institutional review committee on animal care approved the experiments, which were performed according to the guidelines of the National Institutes of Health and the committee on animal research at our institution. Unilateral calf muscle abscesses were induced in 21 rats with an injection of a Staphylococcus aureus suspension. The rats were divided into three groups of seven animals each: low USPIO dose (50 mumol of iron per kilogram of body weight), high USPIO dose (150 mumol Fe/kg), and control (saline solution). All rats were imaged before and 24 hours after USPIO administration at 1.5 T (transverse T1-weighted spin-echo, T2*-weighted fast gradient-echo, and short inversion time inversion-recovery sequences). Images were analyzed quantitatively and qualitatively with regard to Sl and signal pattern. Temporal variation of calculated contrast-to-noise ratios was analyzed with the Wilcoxon signed rank test. MR findings were correlated with histopathologic findings, including those of electron microscopy.RESULTS: Twenty-four hours after USPIO administration in the high-dose group, susceptibility effects were present in abscess periphery on postcontrast T2*-weighted images (P = .04), and Sl enhancement was noted on postcontrast Tl-weighted images within both abscess wall and abscess center (P = .04 for both). In the low-dose group, SI enhancement was noted in entire abscess on Tl-weighted postcontrast images (P = .03). Neither significant Sl loss (P = .09) nor susceptibility effects were detected in periphery or center of any abscess on postcontrast T2*-weighted images. There was no obvious difference in total amount of macrophages among the groups, but there was a clear difference with regard to individual iron content of iron-positive macrophages between the USPIO dose groups.CONCLUSION: At 1.5 T, Sl characteristics of abscesses on T1- and T2*-weighted images obtained 24 hours after USPIO injection strongly depend on administered dose of the contrast agent. At low doses, T1 effects were stronger than T2* effects. (C) RSNA 2005