磁共振扩散加权成像对脑转移瘤立体定向放射治疗疗效评价的研究

Application of DWI in evaluating the response of brain metastases treated by stereotactic radiosurgery

目的通过测量立体定向放射治疗前及治疗后早期脑转移瘤实质扩散系数(ADC)值及r ADC值,以期为临床制定进一步治疗方案提供早期依据。方法收集2013—2015年于某伽玛刀治疗中心就诊的21例脑转移瘤患者26个病灶作为研究对象。在治疗前1 d、治疗后1个月及治疗后6个月分别行常规磁共振成像(MRI)及扩散加权成像(DWI)检查,得到ADC值及r ADC值。同时测量T1WI增强图像上伽玛刀治疗前后肿瘤强化组织最大直径。结果 19个治疗有效的脑转移瘤治疗后肿瘤实质的ADC值及r ADC值均较治疗前明显升高(P<0.01)。治疗无效1例,治疗后ADC值及r ADC值较治疗前明显降低。6个死亡脑转移瘤病灶治疗前后肿瘤实质ADC值及r ADC值的差异无统计学意义(P=0.861)。肿瘤最大直径的变化与ADC值及r ADC值的变化之间无相关性(r_(△ADC)=0.20,P=0.40;r△_(r ADC)=0.32,P=0.18)。结论扩散加权成像在早期评价脑转移瘤立体定向放射治疗效果方面有重要意义。

Objective By measuring the ADC value and r ADC value of brain metastases before and after treatment, in order to provide the basis for clinical treatment. Methods In a prospective study, we collected 26 brain metastases in 21 patients treated in Gamma Knife Center during the latest three years. Conventional MRI and DWI were taken one day before, 1 month after SRS, and 6 months after SRS. The ADCs of brain metastases and contralat-eral white matter and the max diameters of tumors were taken at the various time intervals, and tumor ADC values were normalized to normal-appearing white matter（r ADC）. Results Nineteen brain metastases were treated effectively. The mean pretreatment ADC value and r ADC value in these 19 brain metastases rose significantly（P〈0.01）. One tumor was progressive and both the ADC value and the r ADC value declined after SRS. Six brain metastases of death when 1 month after treatment and the ADCs and the r ADCs had no significant differences（P=0.861）. Pearson′s correlation test shows no significant correlation between changes of tumor diameter and ADC value in whole patients（ r_（△ADC）=0.20,P =0.40;r_（△r ADC）=0.32,P =0.18）. Conclusion DWI is very meaningful in evaluating the early response of brain metastases treated by stereotactic radiosurgery. ADC value and r ADC value of brain metastatic tumor might be useful to predict successful treatment at early time points.