体素内不相干运动磁共振成像评估鼻咽癌同步放化疗疗效

目的探讨体素内不相干运动磁共振成像(intravoxel incoherent motion magnetic resonance imaging,IVIM-MRI)评估鼻咽癌放化疗疗效的价值。材料与方法 27例经活检证实为鼻咽癌的患者,于治疗前、放疗开始后1个月及结束后1个月行MRI扫描,扫描序列包括T1WI、T2WI、IVIM(9个b值,范围0~800 s/mm~2)及T1WI增强。放疗过程中接受3个周期的同步化疗。使用单指数模型获得表观扩散系数(apparent diffusion coefficient,ADC)值,双指数模型测得体素内的纯扩散系数(true molecular diffusion coefficient,D)、灌注分数(perfusion fraction,f)、伪扩散系数(pseudodiffusion coefficient,D*)。测量各扫描时间点肿瘤最大面积及IVIM参数,并分析其动态变化及相关性。结果排除图像伪影病例,最终23例患者被纳入。鼻咽癌病灶ADC及D值在整个治疗过程中逐步升高,治疗前与结束后1个月ADC均值为0.80×10~(-3) mm~2/s和1.57×10~(-3) mm~2/s(P_(1/3)0.001),D均值为0.68×10~(-3) mm~2/s和1.31×10~(-3) mm~2/s(P_(1/3)0.001)。f值先上升后下降,治疗前与放疗开始后1个月f值分别为11%、19%(P_(1/2)0.001)。D*值在1组与2组、1组与3组及2组与3组间差异均无统计学意义。结论 IVIM-MRI可监测鼻咽癌在放化疗过程中的动态变化。组织内微循环灌注对单指数ADC值有影响,体素内水分子的扩散被高估了。而D值的计算是选取高b值(200 s/mm~2),微循环灌注对MR信号的影响微乎其微,反映的是纯扩散信息。因而,D值更能有效监测放化疗疗效,f值可作为潜在观察指标。

Intravoxel incoherent motion magnetic resonance imaging for evaluating the efficacy of concurrent chemoradiotherapy in nasopharyngeal carcinoma

Objective: To explore the value of intravoxel incoherent motion magnetic resonance imaging in evaluating the efficacy of chemoradiotherapy in nasopharyngeal carcinoma (NPC). Materials and Methods: Twenty-seven patients with nasopharyngeal carcinoma proved by biopsy pathology were enrolled. Those patients underwent MRI at the time points of pretreatment (group 1), one month after the start of radiotherapy (group 2) and one month after the end of radiotherapy (group 3). T1WI, T2WI, IVIM (9 b-factors, 0~800 s/mm2) and contrast-enhanced T1WI were included. They received concurrent chemotherapy for 3 cycles during radiotherapy. The apparent diffusion coefficient (ADC) was derived from the mono-exponential model, while the diffusion coefficient (D), perfusion fraction (f) and pseudodiffusion coefficient (D*) were calculated via the bi-exponential model. The values of IVIM parameters and maximum area for NPC lesions were measured at each time point, and their dynamic changes and correlation were analyzed. Results: Patients whose images had artifact were excluded, and 23 patients were included in this study finally. The ADC and D values increased throughout the whole course. ADC value of group 1 and 3 was 0.80×10-3 mm2/s and 1.57×10-3 mm2/s, respectively (P1/3<0.001); D value of group 1 and 3 was 0.68×10-3 mm2/s and 1.31×10-3 mm2/s, respectively (P1/3<0.001). f value was increased originally then decreased. f value of group 1 and 2 was 11% and 19% (P1/2<0.001). There were no correlations between group 1 and group 2, group 1 and group 3, group 2 and group 3 for D* value. Conclusion: IVIM-MRI could monitor dynamic changes of NPC during treatment. ADC value was influenced by microcirculation perfusion, therefore the diffusion of water molecules were overrated. D value was calculated from high b values (>200 s/mm2), so microcirculation perfusion had little effect on MR signal, it reflected pure diffusion information. D value was better at monitoring the efficacy of chemoradiotherapy. f value might be a potential biomarker.