钆喷替酸葡甲胺-白蛋白制备及其在MR淋巴造影中的应用

背景:在评估肿瘤所在区域的引流淋巴结时,CT、MRI等常用影像技术仅依靠淋巴结的大小、形态和分组等非特异性诊断标准,而不能提供有关淋巴结内部结构的重要信息,所以诊断准确性较低.使用钆喷替酸葡甲胺(Gadolinium diethylenetriamine pentaacetic acid, Gd-DTPA),尤其是Gd-DTPA类鳌合物等淋巴靶向的对比剂,有望改善这种不利的局面.目的:制备Gd~(3+)标记的二乙三胺五乙酸一白蛋白--钆喷替酸葡甲胺一白蛋白(Gd-DTPA-HSA),在动物实验中观察其淋巴结靶向强化效果,并探讨其潜在的应用价值.设计、时间及地点:随机分组设计、对照动物实验,于2008-12/2009-04在南方医院影像中心实验室完成.材料:首先将Gd_2O_3与0.1 mol/L HCI反应10 min,制得GdCl_3.然后将DTPA环酐、人血清白蛋白溶液以摩尔比分别为200:1,100:1的比例混合,各分为4等份,在pH值分别为5.0,6.0,7.0,8.0、室温下反应30 min.最后加入GdCl3,络合反应在1 min内完成.将Gd-DTPA-HSA冻干成粉末并配制成0.50 mmol Gd/L的Gd-DTPA-HSA溶液备用.方法:健康新西兰兔6只,平扫后在双侧后脚掌趾蹼间隙各注射0.2 mL含Gd 0.50 mmol/L的Gd-DTPA-HSA溶液,于给药后30 min,1 h,3 h进行3次MRI扫描.测量增强前后胭窝淋巴结的信号强度并计算其强化率.主要观察指标:①不同反应条件下每个白蛋白分子上所结合的Gd3+离子数量,计算不同反应条件DTPA-HSA的偶联效率.②Gd-DTPA-HSA淋巴结靶向强化效果及其动态变化过程.结果:①在DTPA-HSA摩尔比相同的条件下,每分子DTPA-HSA结合的Gd~(3+)数目和DTPA-HSA的偶联效率随着反应体系pH值的增高而增加.②在反应体系pH值一定的条件下,DTPA-HSA摩尔比为200:1时每分子DTPA-HSA结合的Gd~(3+)数目大于DTPA-HSA摩尔比为100:1时的二者结合的数目,但前者的DTPA-HSA偶联效率低于后者.③经趾蹼间隙给药后,小腿淋巴管和胭窝淋巴结明显、均匀的强化.结论:pH=8.0的0.1 mol/L NaHCO_3反应缓冲体系有利于人血清白蛋白与DTPA的偶联反应.Gd-DTPA-HSA是一种有效的淋巴结特异性对比剂,能够靶向强化淋巴结.

Preparation and application of Gadolinium diethylenetriamine pentaacetic acid-human serum albumin in MR lymphography

BACKGROUND: The imaging technique of CT and MRI has lower diagnostic accuracy in analyzing lymph node location due to the nonspecific diagnostic criteria. However, this situation can be improved with Gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA), especially the use of lymphatic targeting contrast agent. OBJECTIVE: To prepare DTPA-coupled human serum albumin (HSA) labeled with gadoliniumion, and to investigate the enhancement for the lymph node in animal experiment, in further, to explore the potential value of its application. DESIGN, TIME AND SETTING: The randomized grouping, controlled animal experiment was performed at the laboratory of Medical Imaging Center, Nanfang Hospital from December 2008 to April 2009. MATERIALS: GdCI3 was prepared with Gd2O3 reacted with 0.1mol/L HCI for 10 minutes. Then, DTPA cyclic anhydride and HAS solution were mixed together at the ratio of 200:1 or 100:1. The product was divided into 4 equal portions, which was reacted with 5.0, 6.0, 7.0, 8.0 pH values at room temperature for 30 minutes. At last, GdCI3 was added. The complexation reaction was completed within 1 minute. The Gd-DTPA-HAS was dried and prepared for Gd-DTPA-HAS solution with concentration of 0.50 mmol Gd/L.METHODS: Six New Zealand rabbits were undergone the MRI examination, followed by subcutaneous injection of 0.2 mL with Gd 0.50 mmol/L HSA-Gd-DTPA solution. And contrast scanning was performed at minutes 30, 60 and 180 after injection. The signal intensity of popliteal lymph node was measured and the enhancement rate was obtained. MAIN OUTCOME MEASURES: The number of combined Gd-DTPA per HSA at different reaction conditions was measured, and coupling efficiency of HSA-DTPA was calculated. The enhancement rates of lymph node, as well as dynamic changes were observed. RESULTS: ①The number and coupling efficiency of HSA-coupled of gadolinium ions were increased with the pH value of the reaction system at the same DTPA-to-HSA molar ratio. ②At the same pH value of the reaction system, the number of HSA-coupled of gadolinium ions increased with the DTPA-to-HSA molar ratios while the coupling efficiency of HSA-coupled of gadolinium ions decreased.③After subcutaneous injection, HSA-Gd-DTPA entered the lymphatic vessel, which resulted in obvious homogeneous enhancement of the lymphatic vessels and popliteal lymph nodes. CONCLUSION: The number and coupling efficiency of HSA-coupled of gadolinium ions can be increased in pH=8.0, 0.1 mol/L NaHCO_3 reaction system. HSA-Gd-DTPA is an effective contrast agent targeted for lymph node after subcutaneous administration.