Xue Hua-Dan, Li Shuo, Sun Hong-Yi, Jin Zheng-Yu, Sun Fei
Department of Radiology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing.
Chin Med Sci J. 2008 Sep;23(3):166-71. doi: 10.1016/s1001-9294(09)60033-x.
To investigate the feasibility of magnetic resonance (MR) diffusion weighted imaging (DWI) in discriminating inflammatory from VX2 carcinoma metastatic lymph nodes in rabbit model.
Twenty New Zealand white rabbits were randomly divided into 2 groups. Complete Freund's adjuvant was injected into the bilateral dorsal footpads to set up ipsilateral lymphadenitis model (n = 10), and the other 10 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. MR imaging scan covering the popliteal fossa and iliac fossa including short time inversion recovery echo-planar imaging DWI (STIR-EPI-DWI), T1-weighted imaging (T1WI) and T2-weighted imaging (T2WI) was performed 2 weeks after injection. T2WI signal intensity (SI), DWI SI, long/short axial ratio (LSR) and apparent diffusion coefficient (ADC) values of the lymph nodes were evaluated in all cases. Right after MR imaging scan, popliteal and iliac fossa lymph nodes were collected for hematoxylin-eosin staining.
Totally 33 lymph nodes larger than 5 mm, including 22 inflammatory and 11 metastatic ones, were successfully isolated and taken into pathological analysis. LSR showed no significant difference between the inflammatory and malignant lymph nodes (P > 0.05). Both benign and malignant lymph nodes appeared iso-intense on T1WI and hyperintense on both T2WI and DWI images with an even lower T1WI and higher T2WI SI core at the hilum. Both T2WI and DWI SI showed no significant difference between two pathological groups (P > 0.01) in popliteal fossa. The mean ADC value of inflammatory nodes [(1.199 +/- 0.281) x 10(-3) mm2/s] was significantly higher than that of metastatic nodes [(0.858 +/- 0.090) x 10(-3) mm2/s, P < 0.01]. On ADC map, a high ADC value central area could be seen in most of the lymph nodes no matter benign or malignant. ADC value gave out the largest area under curve (AUC(ADC) = 0.955) compared with other three indexes (AUC(LSR) = 0.488; AUC(T2WI SI)= 0.727; AUC(DWI SI) = 0.822) and gave the best sensitivity and specificity in lymph node differential diagnosis compared with the other three indexes.
High quality DWI image can be obtained using STIR-EPI-DWI sequence in rabbit model. DWI is a new promising technique for differentiating inflammatory from metastatic lymph nodes. Compared with routine MR sequence, DWI could provide more useful physiological and functional information for diagnosis.
探讨磁共振（MR）扩散加权成像（DWI）在兔VX2癌转移淋巴结与炎性淋巴结鉴别诊断中的可行性。
将20只新西兰白兔随机分为2组。在双侧足背垫注射完全弗氏佐剂建立同侧淋巴结炎模型（n = 10），另10只兔双侧大腿皮下注射VX2肿瘤细胞悬液（1.5×10⁷细胞/mL）建立转移淋巴结模型。注射后2周行MR成像扫描，扫描范围覆盖腘窝和髂窝，包括短时反转恢复回波平面成像DWI（STIR-EPI-DWI）、T1加权成像（T1WI）和T2加权成像（T2WI）。评估所有病例中淋巴结的T2WI信号强度（SI）、DWI SI、长短轴比（LSR）及表观扩散系数（ADC）值。MR成像扫描结束后，立即采集腘窝和髂窝淋巴结行苏木精-伊红染色。
共成功分离出33个直径大于5 mm的淋巴结，其中炎性淋巴结22个，转移淋巴结11个，并进行了病理分析。炎性淋巴结与恶性淋巴结的LSR差异无统计学意义（P > 0.05）。良性和恶性淋巴结在T1WI上均呈等信号，在T2WI和DWI图像上均呈高信号，淋巴结门部T1WI信号更低，T2WI信号更高。腘窝处两组病理类型的淋巴结T2WI和DWI SI差异均无统计学意义（P > 0.01）。炎性淋巴结的平均ADC值[（1.199±0.281）×10⁻³ mm²/s]显著高于转移淋巴结[（0.858±0.090）×10⁻³ mm²/s，P < 0.01]。在ADC图上，大多数良性或恶性淋巴结均可看到高ADC值的中央区域。与其他三个指标相比，ADC值的曲线下面积最大（AUC(ADC)=0.955；AUC(LSR)=0.488；AUC(T2WI SI)=0.727；AUC(DWI SI)=0.822），在淋巴结鉴别诊断中，其敏感性和特异性均优于其他三个指标。
在兔模型中使用STIR-EPI-DWI序列可获得高质量的DWI图像。DWI是鉴别炎性与转移淋巴结的一种有前景的新技术。与常规MR序列相比，DWI可为诊断提供更多有用的生理和功能信息。
