Xue Hua-Dan, Lei Jing, Li Zhuo, Wang De-Tian, Zhou Wei-Xun, Dai Wei, Jin Zheng-Yu
Department of Radiology, PUMC Hospital, CAMS and PUMC, Beijing 100730, China.
Zhongguo Yi Xue Ke Xue Yuan Xue Bao. 2009 Apr;31(2):139-45.
To assess the characteristics of enhanced magnetic resonance image with ultrasmall superparamagnetic iron oxide (USPIO) in the inflammatory and tumor metastatic rabbit model, and explore its relevance with histologic ultrastructural findings.
Totally 36 New Zealand white rabbits were randomly divided into lymphadenitis group and metastatic group. Complete Freund's adjuvant was injected into the bilateral dorsal footpads of 18 rabbits to set up ipsilateral lymphadenitis model. The other 18 rabbits received a subcutaneous implantation of VX2 tumor cell suspension (1.5 x 10(7) cells/ml) in both thighs to set up metastatic lymph node model. Magnetic resonance scan were performed 24 hours before and after USPIO (90 micromol Fe/kg) injection. T2 values of each lymph node were measured and lymph node T2 enhancement rate was calculated as well. HE staining, Prussian blue staining, and electronic microscopy were performed to observe the pathological microstructure changes and the distribution of the iron particle in lymph node. Relationship between lymph nodes USPIO enhancement and its microstructures were further analyzed. Results Thirty-six lymph nodes in lymphadenitis group showed different degrees of reactive hyperplasia. Twenty-six lymph nodes in metastatic group were invaded by tumor cell. Non-enhanced scan showed mild difference between T2 signal intensity of the two pathological lymph node types. After USPIO enhancement, inflammatory lymph nodes showed distinct T2 signal reduction at the center, and metastatic lymph nodes showed homogenous and faint T2 signal reduction. Enhancement rate of benign and malignant lymph nodes were 57.39% and 29.45% respectively (P < 0.01). HE staining and Prussian blue staining indicated USPIO particles located mainly in the macrophages at inflammatory lymphatic medulla, while paracortical area and cortical area contained relatively much less USPIO particles due to less macrophages distribution. MRI findings were correlated with the pathological results. Electronic microscopy also verified that the majority of USPIO particles were located in the numerous cytophagic bubbles of macrophages. Lymph nodes metastasis including 4 lymph nodes with completed structure destruction due to entire tumor infiltration, 19 lymph nodes with partially lymph node structure destruction but reduced USPIO-contained macrophage numbers or reduced USPIO particles in macrophages, and 3 lymph nodes with only localized foci tumor metastasis at subcapsular area. Conclusions USPIO enhancement pattern of different lymph nodes is closely related to distribution and functional status of the intra-node macrophages. It may affect the accuracy of the lymph node property diagnosis based on USPIO enhanced image.
评估超小型超顺磁性氧化铁（USPIO）增强磁共振成像在兔炎症和肿瘤转移模型中的特征，并探讨其与组织学超微结构结果的相关性。
将36只新西兰白兔随机分为淋巴结炎组和转移组。18只兔双侧背部足垫注射完全弗氏佐剂建立同侧淋巴结炎模型。另外18只兔双侧大腿皮下植入VX2肿瘤细胞悬液（1.5×10⁷细胞/ml）建立转移淋巴结模型。在注射USPIO（90 μmol Fe/kg）前后24小时进行磁共振扫描。测量各淋巴结的T2值并计算淋巴结T2增强率。进行苏木精-伊红（HE）染色、普鲁士蓝染色和电子显微镜检查，观察淋巴结病理微观结构变化及铁颗粒分布。进一步分析淋巴结USPIO增强与其微观结构之间的关系。结果：淋巴结炎组36个淋巴结呈现不同程度的反应性增生。转移组26个淋巴结被肿瘤细胞侵袭。未增强扫描显示两种病理类型淋巴结的T2信号强度差异轻微。USPIO增强后，炎性淋巴结中央T2信号明显降低，转移淋巴结呈现均匀且微弱的T2信号降低。良性和恶性淋巴结的增强率分别为57.39%和29.45%（P<0.01）。HE染色和普鲁士蓝染色显示USPIO颗粒主要位于炎性淋巴结髓质的巨噬细胞中，而副皮质区和皮质区由于巨噬细胞分布较少，所含USPIO颗粒相对较少。磁共振成像结果与病理结果相关。电子显微镜也证实大多数USPIO颗粒位于巨噬细胞的大量吞噬泡中。淋巴结转移包括4个因肿瘤完全浸润导致结构完全破坏的淋巴结、19个淋巴结结构部分破坏但含USPIO的巨噬细胞数量减少或巨噬细胞内USPIO颗粒减少的淋巴结以及3个仅在被膜下区域有局部肿瘤转移灶的淋巴结。结论：不同淋巴结的USPIO增强模式与淋巴结内巨噬细胞的分布和功能状态密切相关。它可能影响基于USPIO增强图像的淋巴结性质诊断的准确性。
