阳性亲淋巴对比剂增强MR淋巴成像对淋巴结病变的诊断价值

目的 探讨大分子阳性亲淋巴对比剂在间质MR淋巴成像中对肿瘤转移、炎性增生淋巴结的鉴别诊断价值.方法 采用18只纯种新西兰大白兔,体质量2.0～2.5 kg.在其中9只兔一侧后肢各趾蹼处注射完全型免疫佐剂,用于建立腘窝淋巴结炎性增生模型(炎性增生组);另9只兔一侧后肢肌肉接种VX~2瘤建立腘窝淋巴结肿瘤转移模型(肿瘤转移组).对侧正常腘窝淋巴结作为对照.各组每只兔接种前后行MR淋巴成像检查.将0.2 ml二氨基乙基乙二醇醚-DTPA酰胺共聚物钆配合物(Gd-poly-DTPA-EOEA)注入各组每只兔双侧后肢足背部各趾蹼处的皮下.在注射对比剂前后分别进行3D T_1WI扫描和MIP图像重组.在增强3D MIP图像上测量每一腘窝淋巴结短轴最大径(MSAD),在每只兔胭窝淋巴结中选取直径最大者测量其延迟扫描各观察时点的信噪比(SNR).采用成组设计t检验比较炎性增生组与肿瘤转移组腘窝淋巴结接种后MSAD的差异和每一观察时点炎性增生组、肿瘤转移组、正常对照侧腘窝淋巴结间的SNR差异.分析各组腘窝淋巴结的MR淋巴成像图像,并与病理检查相对照.结果 肿瘤组2只兔接种未成功,其他模型形成良好.13个炎性增生、11个肿瘤转移腘窝淋巴结的MSAD分别为(1.32±0.14)cm和(1.33±0.12)cm,差异无统计学意义(t=0.186,P＞0.05).延迟扫描5、15、30、60、90、120 min,9个炎性增生腘窝淋巴结与正常对照侧腘窝淋巴结的SNR值分别为17.31±0.37和17.19±0.29、27.42±0.50和27.39±0.48、38.44±0.47和38.19±0.27、37.10±0.09和36.97±0.10、36.32±0.61和36.20±0.80、34.60±0.44和34.71±0.32,两组间各对应时点SNR值的差异均无统计学意义(t值分别为0.78、0.14、1.43、1.00、0.36、-0.62,P值均＞0.05).7个肿瘤转移腘窝淋巴结和正常对照侧腘窝淋巴结的SNR值分别为6.00±0.22和17.21±0.28、7.87±0.16和27.17±0.23、8.14±0.24和38.16±0.19、8.09±0.28和36.94±0.30、7.59±0.20和35.96±0.72、7.50±0.14和34.81±0.27,两组间各对应时点SNR值的差异均有统计学意义(t值分别为-84.00、-182.72、-261.27、-186.48、-100.22、-239.00,P值均＜0.01).炎性增生组淋巴结的SNR值明显高于肿瘤转移组,差异有统计学意义(t值分别为83.97、174.07、158.49、152.71、96.06、154.57,P值均＜0.01).肿瘤转移淋巴结在MR淋巴成像图像上表现为淋巴结完全或部分的信号缺损.结论 通过阳性亲淋巴对比剂增强MR淋巴成像可提供解剖背景下淋巴结解剖和功能方面的信息,是特异性地鉴别良、恶性淋巴结的敏感检查方法.

Evaluation of MR lymphography with positive lymphotropic contrast agent in diagnosing lymph node lesions

Objective To evaluate the interstital MR lymphography using positive lymphotropic contrast agent for differentiation of metastatic lymph nodes from inflammatory lymph nodes hyperplasm.Methods Eighteen New Zealand white rabbits weighted at 2.0-2.5 kg were used.Inflammatory hyperplastic popliteal lymph node model was established in 9 rabbits by injection of complete freund adjuvant into the interdigitial skin of the dorsal aspect of one hind leg,and tumor-bearing popliteal lymph node model was established in another 9 rabbits by injection of VX~2 tumor cell suspension.The popliteal lymph nodes of another hind leg of all 18 rabbits were assigned to the normal contral group.In each group,every rabbit underwent MR lymphography examination before and after the inoculation.Volumes of 0.2 ml of Gd[DTPA-bis(2-aminoethoxy)ethane]polymeric contrast agent(Gd-poly-DTPA-EOEA)injection were injected subcutaneously into the dorsal feet of both hind legs of two groups of rabbits.T_1-weighted 3D gradient-echo images were obtained,and source images were used to reconstruct images of MIP before and after the administration of agent.The maximum short-axis diameter(MSAD)of each popliteal lymph node was measured on the enhanced 3D MIP images,and the signal-to-noise ratio(SNR)measurement was performed in the largest popliteal node of each rabbit at each time point in delayed scan.Independentsamples t test was used to compare the sizes of popliteal nodes in MSADs between inflammatorily hyperplastic and tumor-bearing nodes after the inoculation,and the values of SNRs of popliteal nodes at each time point between inflammatorily hyperplastic,tumor-bearing and normal popliteal lymph nodes.Imaging results of the popliteal nodes were analyzed and correlated with pathological findings.Results All of the rabbits were successfully inoculated except of the 2 rabbits in tumor-bearing nodal group.The size in MSAD of 13 inflammatorily hyperplastic and 11 tumor-bearing nodes was(1.32±0.14)and(1.33±0.12)cm,respectively.There was no significant statistical difference between the sizes of the two groups(t=0.186,P＞0.05).At the time of 5,15,30,60,90,120 minutes after the injection of the agent,the value of SNR of 9 inflammatorily hyperplastic and 9 contralateral normal nodes was 17.31±0.37 and 17.19±0.29,27.42±0.50 and 27.39±0.48,38.44±0.47 and 38.19±0.27,37.10±0.09 and 36.97±0.10,36.32±0.61 and 36.20±0.80,34.60±0.44 and 34.71±0.32,respectively.There was no significant statistical difference between the values of the two groups(t=0.78,0.14,1.43,1.00,0.36,-0.62,respectively,P＞0.05).The value of SNR of seven tumor-bearing and seven contralateral normal nodes was 6.00±0.22 and 17.21±0.28,7.87±0.16 and 27.17±0.23,8.14±0.24 and 38.16±0.19,8.09±0.28 and 36.94±0.30,7.59±0.20 and 35.96±0.72,7.50±0.14 and 34.81±0.27,respectively.There was significant statistical difference between the values of the two groups(t=-84.00,-182.72,-261.27,-186.48,-100.22,-239.00,respectively,P＜0.01).At each time point,inflammatorily hyperplastic nodes had significantly higher values of SNRs compared to tumor-bearing nodes(t=83.97,174.07,158.49,152.71,96.06,154.57,respectively,P＜0.01).A complete or part signal filling defect occurred in the tumor-bearing lymph node on the MR lymphographic images.Conclusions The internal anatomy and function of the lymph nodes were effectively visualized by interstitial MR lymphography with positive lymphotropic contrast agent,which provide a sensitively diagnostic way for the differentiation of benign lymph nodes from malignant ones.