外周带前列腺癌与正常组织的广延指数和单指数模型扩散加权成像的比较

Comparison of stretched-exponential and monoexponential models of diffusion-weighted imaging between prostate cancer and normal tissues

目的:比较前列腺外周带癌与正常组织的广延指数和单指数模型弥散加权成像(diffusionweighted imaging,DWI)参数的差异。方法:25例外周带前列腺癌确诊患者行DWI检查,b值为0、500、1 000、2 000 s/mm2。通过单指数模型计算前列腺癌和正常组织的表观扩散系数(apparent diffusion coefficient,ADC),广延指数模型计算分布扩散系数(distributed diffusion coefficient,DDC)和校正系数α值。比较癌组织与正常组织之间ADC值、DDC值和α值(范围0~1)的差异,评价各组织中ADC值与DDC值的差异和相关性,并比较前列腺癌与正常组织之间A D C值和D D C值标准化差值。结果:共3 0个前列腺癌病灶、3 4个正常外周带组织纳入研究。前列腺癌组织ADC值[(0.73±0.14)×10^(-3)mm^2/s]、DDC值[(0.62±0.20)×10^(-3)mm^2/s]和α值(0.65±0.10)均显著低于正常外周带[(1.43±0.25)×10^(-3)mm^2/s、(1.49±0.20)×10^(-3)mm^2/s、0.86±0.09;均P<0.05)]。前列腺癌组织的ADC值明显高于DDC值,正常外周带组织的ADC值低于DDC值(均P<0.05)。在前列腺癌及正常组织中,ADC值与DDC值均密切相关(R2=0.98、0.98,均P<0.05),前列腺癌组织的ADC值和DDC值的标准化差值明显高于正常组织。结论:广延指数模型DWI为鉴别前列腺癌与正常组织提供了更多信息,有助于提高前列腺癌的诊断率。

Objective：To compare the parameters of stretched-exponential and monoexponential models of diffusion-weighted imaging （DWI） between prostate cancer and normal tissues.Methods：Twenty-ifve patients with peripheral zone prostate cancer underwent DWI exam using b-values of 0, 500, 1 000, and 2 000 s/mm2. The distributed diffusion coefifcient （DDC） and α values of prostate cancer and normal tissues were obtained using stretched-exponential model and apparent diffusion coefifcient （ADC） values were obtained using monoexponential model. The ADC, DDC （both in 0^-3mm^2/s） and α values （range 0-1） were compared between prostate cancer and normal tissues. The ADC and DDC values were compared and correlated in each tissue, and the standardized differences between DDC and ADC values were compared between prostate cancer and normal tissues.Results：Data were obtained from 30 lesions and 34 normal peripheral zone tissue. The ADC （0.73±0.14）, DDC （0.62±0.20） and α values （0.65±0.10） of tumor were all signiifcantly lower than those of the normal tissues （1.43±0.25, 1.49±0.20 and 0.86±0.09） （allP〈0.05）. ADC value was signiifcantly higher than DDC value in tumor but lower than DDC value in normal tissue （all P〈0.05）. ADC value and DDC value were signiifcantly correlated （R^2=0.98, 0.98, respectively;P〈0.05） in prostate cancer and normal tissues, and the standardized difference between ADC value and DDC value in tumor was signiifcantly higher than that in normal tissue.Conclusion：The stretched-exponential model of DWI provides more parameters for prostate cancer and normal tissues and would improve the diagnosis of prostate cancer.