动态增强 MRI 定量与半定量分析在直肠癌术前 T、N 分期中的应用价值

Applications of quantitative and semi-quantitative dynamic contrast enhanced magnetic resonance imaging analysis in T-staging and N-staging of preoperative rectal cancer

目的：评估动态增强 MRI（DCE-MRI）定量、半定量分析在直肠癌术前 T、N 分期诊断中的应用价值。方法回顾性分析山西省肿瘤医院 MR 室2014年7月—2014年11月经肠镜病理证实的27例直肠癌患者影像资料。其中男18例,女9例,年龄45~73岁,此前均未经任何治疗。均于术前行 DCE-MRI,用 Omni-Kinetics 专用灌注软件进行后处理,同时获得容量转移常数（Ktrans ）、速率常数（Kep ）、细胞外血管外间隙容积比（Ve ）等定量参数,以及达峰时间（TTP）、曲线下面积（AUC）、最大浓度（Max Conc）、最大斜率（Max Slope）等半定量参数。对正常肠壁与病变段肠壁的定量、半定量参数行独立样本 t 检验；采用秩和检验比较各定量、半定量参数在直肠癌术后病理 T、N 分期的差异,判断各参数的诊断价值。应用 ROC 曲线分析定量参数在 T、N 分期中的最佳诊断界点及敏感性、特异性。根据 TNM 对患者进行分期。结果正常肠壁与病变段肠壁的 Ktrans 值[（0.28±0.14） min -1 vs （1.33±0.86）min -1]、Kep值[（1.41±0.67）min -1 vs （3.56±0.72）min -1]、Max Conc（0.17±0.02 vs 0.29±0.09）、AUC（0.11±0.07 vs 0.23±0.11）比较,差异均具有统计学意义（t =-6.270、-11.359、-2.487、-2.803,P 值均〈0.05）。在 T 分期为 T1~2的早期组与 T3~4的晚期组间 Ktrans值[0.66（0.12~1.35）min -1 vs 2.15（0.84~2.96） min -1]、Kep值[2.51（0.12~5.65）min -1 vs 4.05（3.18~6.68） min -1]比较,差异均有统计学意义（Z 值分别为-4.077、-2.281,P 值均〈0.05）。 N 分期中,淋巴结无转移组的 Ktrans 值（1.01±0.73）、Ve 值（0.29±0.18）、TPP（0.93±0.35）均低于转移组（1.75±0.84、0.54±0.29、1.14±0.15,差异均有统计学意义（Z 值分别为-2.433、-2.832、-2.496, P 值均〈0.05）。结论 DCE-MRI 定量及半定量参数在判断正常肠壁与病变段肠壁、直肠癌的术前T、N 分期方面和病理有较高的相关性,对诊断有一定参考价值。定量参数 Ktrans值、Ve 值最佳诊断界点为直肠癌 T、N 分期提供了较高的敏感性与特异性。

Objective To explore diagnostic values of the semi-quantitative and quantitative dynamic contrast enhanced magnetic resonance imaging （ DCE-MRI） analysis in the T-stage and N-stage preoperative assessment of rectal cancer. Methods Twenty-seven patients with colonoscopy pathologically proven rectal cancer in Shanxi Province Tumor Hospital from July 2014 to Nov. 2014 were retrospectively analyzed. Among those, there were 18 men and 9 women, ages ranged from 45 to 73 years, and no prior surgeries were performed. The patients underwent DCE-MRI examinations before the surgery, with several semiquantitative and quantitative parameters including transfer constant（ Ktrans ）, rate constant of bacKflux （Kep ） , extravascular extracellular volume fraction（Ve ）, Time To Peak（TTP）, Max Concentration, Area Under Curve （ ADC） and Max Slope measured and statistically analyzed using Omni-Kinetics software. Differences of the quantitative and semiquantitative parameters between normal tissue and lesions were compared using the paired t test. Mann-whitney U tests were utilized to examine the differences of the quantitive and semiquantitative parameters between different T-stage or N-stage lesions to determine their diagnostic values. Receiver operating characteristic （ROC） curve analyses were performed to determine thenbsp;cut-off values to quantitatively distinguish different T stages and N stages. Results There were significant differences of Ktrans , Kep , Max Conc and AUC between normal tissue and lesions （t = - 6. 270, - 11. 359,- 2. 487, - 2. 803, all P values 〈 0. 05）. In T-staging, Ktrans and Kep values were statistically significant between T1-2 group and T3-4 group （Z = - 4. 077, - 2. 281, all P values 〈 0. 05）. In N-staging, the Ktrans , Ve and TTP in no lymph node metastasis group was significantly lower than those in lymph node metastasis group （Z = - 2. 433, - 2. 832, - 2. 496, all P values 〈 0. 05）. Conclusions The quantitative and semi-quantitative DCE-MRI parameters showed high correlations with pathology in differentiation of normal rectal wall and lesions, and in preoperative rectal cancer T-staging and N-staging, which demonstrated reference values in diagnosis. The cut-off value of Ktrans and Ve values provided high sensitivity and specificity in differentiation between T staging and N staging.