磁共振弥散加权成像在^(125)Ⅰ粒子组织间植入治疗胰腺癌疗效评估中的应用

The application of MR diffusion-weighted imaging in evaluating the efficacy of ^(125)I seed interstitial brachytherapy for pancreatic carcinomas:an experimental study in vivo

目的探讨磁共振(MRI)弥散加权(DWI)成像对^(125)Ⅰ粒子组织间植入治疗人胰腺癌裸鼠移植瘤疗效的评估价值。方法将人胰腺癌SWI990细胞株接种于BABL/C裸鼠右下肢旁腹股沟区偏背侧皮下,待瘤体长至8～10 mm进行干预,共有16只裸鼠的成瘤大小适用于实验,分为实验组8只,植入^(125)Ⅰ粒子,和对照组8只,植入空载粒子。粒子植入前及治疗后2周和2个月时分别行MRI常规扫描及DWI成像。取瘤体标本行组织病理学检查。结果实验组肿瘤细胞坏死明显,而对照组肿瘤细胞无明显或有少许坏死。裸鼠心、肝、肺、肾及脾脏等组织无明显放射炎症表现。常规MRI成像评价^(125)Ⅰ粒子治疗胰腺癌疗效的价值有限。DWI显示实验组内整个肿瘤组织的表观弥散系数(ADC)值在治疗前为(0.001 15±0.000 13)mm^2/s,治疗后2周为(0.00I 29±0.000 038)mm^2/s,治疗后2个月为(0.002 08±0.000 14)mm^2/s,与治疗前相比差异有统计学意义(P<0.05)。实验组肿瘤实质区的ADC值亦较治疗前及对照组增高,但低于坏死区ADC值。结论 ^(125)Ⅰ粒子组织间植入治疗人胰腺癌裸鼠移植瘤可导致肿瘤坏死.并对周围脏器是安全的。用常规MRI及DWI成像观察裸鼠皮下移植瘤可行。DWI对疗效评估有重要价值。

Objective To discuss the application of MR diffusion-weighted imaging （DWI） in evaluating the efficacy of ^125I seed interstitial brachytherapy for human pancreatic carcinoma xenografts in nude mice. Methods The human pancreatic cell line SW1990 was subcutaneously injected into the region that was slightly lateral to the right groin of the nude mice. When the tumor grew up to 8-10 mm in size, the intervention was begun. A total of 16 nude mice with suitable sized tumor were used in this study. Implantation of ^125I seeds was used in the mice of study group （n = 8）, while implantation of empty seeds was performed in the mice of control group （n = 8）. Before seed implantation, as well as at 2 weeks and 2 months after the therapy, conventional MRI scans and DWI were performed to observe the tumors. The specimens were collected and sent for histopathological examination. Results Remarkable tumor necrosis could be seen in the tumors of the study group, but only a little or unnotable necrosis was seen in the control group. The heart, liver, lung, kidney and spleen of nude mice showed no signs of significant radiation inflammation. The value of using conventional MRI imaging to make efficacy evaluation of ^125I seeds brachytherapy for pancreatic cancer was limited. In the study group, on DWI the apparent diffusion coefficient （ADC） values of the entire tumor estimated before the treatment, as well as 2 weeks and 2 months after the treatment were （0.001 15 ± 0.000 13） mm2/s, （0.001 29 ± 0.000 038） mm2/s and （0.002 08 ± 0.000 14） mm2/s respectively. The ADC values estimated after the treatment were significantly different from those estimated before the treatment （P 〈 0.05）. The ADC values of the entire tumor in the study group was closely correlated with the tumor necrosis rate （r = 0.821, P = 0.000）. The ADC values of the tumor＇s solid components in the study group were higher than those determined before the treatment as well as higher than those obtained in the control group, but the values were lower than ADC values of the necrotic area. Conclusion For the treatment of human pancreatic cancer xenografts in nude mice, ^125I seeds interstitial brachytherapy is very effective. The ^125I seeds can cause tumor necrosis, but it is safe for the surrounding organs. Conventional MRI and DWI can be used to observe the subcutaneously-implanted tumors in nude mice. DWI is very valuable in evaluating the efficacy of ^125I seed interstitial brachytherapy. （J Intervent Radiol, 2012, 21： 492-497）