磁共振扩散峰度成像评价宫颈癌放疗后变化的小鼠实验研究

目的评价宫颈癌小鼠模型放疗前后的磁共振扩散峰度成像参数变化情况。材料与方法建立皮下种植成瘤的宫颈癌小鼠模型11只,在一侧腹股沟区及对侧腋下分别成瘤,对腹股沟区肿瘤行一次性大剂量放疗照射,腋下肿瘤作为未经放疗的对照组。对两部位肿瘤放疗前及放疗后1周左右行常规MR T2WI及磁共振扩散峰度成像(diffusion kurtosis imaging,DKI)成像,感兴趣区选取肿瘤全层面,计算表观扩散系数(apparent diffusion coefficient,ADC)值、平均扩散率(mean diffusivity,MD)、平均峰度值(mean kurtosis,MK)的平均值(av)及中位值(m)。对比放疗前各参数值的相关性(Pearson相关性检验),以及放疗前后在放疗组和对照组的变化差异(配对t检验)。结果放疗前的ADC值与MK之间存在强负相关性,ADC值与MD之间存在强正相关性(相关系数均大于0.7)。与放疗前相比,腹股沟组肿瘤放疗后的ADC值明显升高(ADCav分别为0.571±0.063×1 0~(-3) mm~2/s和0.6 1 1±0.0 5 5×1 0~(-3) mm~2/s,P=0.0 1 5;A D C m分别为0.543±0.052×10~(-3) mm~2/s和0.587±0.041×10~(-3) mm~2/s,P=0.013),MK值明显降低(MKav分别为1.14±0.12和1.02±0.10,P=0.003;MKm分别为1.13±0.10和1.14±0.10,P=0.003),而MD值的变化无统计学差异(MDav分别为0.856±0.105×10~(-3) mm~2/s和0.885±0.071×10~(-3) mm~2/s,P0.05;MDm分别为0.843±0.113×10~(-3) mm~2/s和0.878±0.081×10~(-3) mm~2/s,P0.05)。MK平均值变化幅度约9.4%,ADC平均值变化幅度约7.5%。对照组肿瘤前后两次ADC值、MD值和MK值均无统计学显著性差异(P0.05)。结论宫颈癌放疗后会引起ADC值的升高和MK的降低,其中MK的变化幅度相对稍高,提示扩散峰度成像用于放疗评价的可行性。

MR diffusion kurtosis imaging versus standard diffusion imaging: changes with radiation in uterine cervical carcinoma xenografts

Objective: To explore the changes of diffusion-kurtosis imaging (DKI) derived parameters after radiation treatment in cervical cancer xenografts, comparing with traditional apparent diffusion coefficient (ADC) values. Materials and Methods:HELA cell cervical cancer xenografts were built with one tumor in inguinal region and one tumor in contralateral side axillary cavity for each mouse. Radiation were performed on groin area with a single dose of 15 Gy, taking axillary tumors as non-treated contrast. MRI were performed before radiation (pre) and at the 7th day (post) after radiation on a 1.5 T scanner using phase-array animal coil. Maps of mean kurtosis (MK), mean diffusivity (MD) and ADC values were generated with in-house-made software developed in Matlab. Regions of interests covering whole tumor were drawn for each lesion. Average and median values of MK, MD and ADC, respectively, were acquired and the relationships were compared. Differences before and after radiation were compared within treated group and the contrast group using paired sample t test. Results: Strong negative relation of ADC and MK, and strong positive relation of ADC and MD were seen before radiation (r>0.7). After radiation, treated tumors got increased ADC (ADCav 0.571±0.063×10-3 mm2/s v.s. 0.611±0.055×10-3 mm2/s, P=0.015. ADCm 0.543±0.052×10-3 mm2/s v.s. 0.587±0.041×10-3 mm2/s, P=0.013) and decreased MK (MK 1.14±0.12 v.s. 1.02±0.10, P=0.003. MKm 1.13±0.10 v.s. 1.14±0.10, P=0.003) while MD tended to increase but with no statistical significance (MDav 0.856±0.105×10-3 mm2/s v.s. 0.885±0.071× 10-3 mm2/s, P>0.05. MDm 0.843±0.113×10-3 mm2/s v.s. 0.878±0.081×10-3 mm2/s, P>0.05). The average changing rates were 9.4% for MK and 7.5% for MD. No differences were found in the contrast group. Conclusions: Both ADC and MK were able to change with radiation treatment for cervical cancer, in which MK got higher changing rate, thus making DKI hold the potential to use as a tool in therapy evaluation.