Department of Radiology, University Hospital of Strasbourg, 67098 Strasbourg, France.
AJR Am J Roentgenol. 2010 Jun;194(6):W521-6. doi: 10.2214/AJR.09.3768.
The objective of our study was to prospectively evaluate macrophage imaging using ultrasmall superparamagnetic iron oxide (USPIO)-enhanced MRI to depict bacterial knee infection in an experimental rabbit model.
Unilateral knee infection was induced by intraarticular injection of Staphylococcus aureus in eight rabbits. The contralateral knees were used as internal controls. After a mean interval of 3 days, two MRI sessions (3-T MRI) were performed before and 24 hours after IV administration of USPIO. The protocol included T1-weighted spin-echo, T2-weighted spin-echo, and T2*-weighted gradient-echo images. A gadolinium-enhanced T1-weighted sequence was also performed in the first session to optimize detection of synovial hyperplasia. MR data were analyzed qualitatively and quantitatively and compared with histopathologic findings (H and E stain and Perls Prussian blue stain). Signal-to-noise ratio changes after USPIO administration were compared using Wilcoxon's signed rank test.
All inoculated knees presented infectious synovitis with intense infiltration of iron-loaded macrophages. In these infected knees, signal loss was determined visually and quantitatively on T1-weighted (p < 0.01), T2-weighted (p < 0.01), and T2*-weighted images (p < 0.01) 24 hours after USPIO administration, reflecting the presence of USPIO-loaded macrophages in the synovium. In contrast, no significant MR signal changes were observed in the control knees (p = 0.07-0.48), which presented a normal synovium without infiltration of iron-loaded macrophages.
Macrophage imaging using USPIO-enhanced MRI can depict infectious knee synovitis.
本研究旨在前瞻性评估超顺磁性氧化铁（USPIO）增强 MRI 对实验性兔膝感染模型中巨噬细胞的成像作用。
通过关节内注射金黄色葡萄球菌在 8 只兔的单侧膝关节中诱导感染。对侧膝关节作为内部对照。在平均间隔 3 天后，在静脉注射 USPIO 前后进行了两次 3-T MRI 检查（第 1 次和第 2 次）。方案包括 T1 加权自旋回波、T2 加权自旋回波和 T2*-加权梯度回波图像。在第 1 次检查中还进行了钆增强 T1 加权序列以优化对滑膜增生的检测。对 MR 数据进行定性和定量分析，并与组织病理学发现（H&E 染色和普鲁士蓝染色）进行比较。使用 Wilcoxon 符号秩检验比较 USPIO 给药后的信噪比变化。
所有接种膝关节均出现感染性滑膜炎，铁负荷巨噬细胞大量浸润。在这些感染的膝关节中，在 USPIO 给药后 24 小时，T1 加权（p<0.01）、T2 加权（p<0.01）和 T2*-加权图像上确定了视觉和定量的信号丢失，反映了滑膜中 USPIO 负载的巨噬细胞的存在。相比之下，在对照膝关节中未观察到明显的 MR 信号变化（p=0.07-0.48），这些膝关节的滑膜没有铁负荷巨噬细胞浸润，表现为正常滑膜。
USPIO 增强 MRI 可用于巨噬细胞成像，以描绘感染性膝滑膜炎。
