PET/CT及DWI-MRI早期评估兔VX2肉瘤射频消融效果

FDG-PET/CT and diffusion-weighted MRI evaluation of the early therapeutic effect of radiofrequency ablation for VX2 sarcomas in rabbits

目的探讨弥散加权(DWI)-MRI和18F-FDG-PET/CT评估兔VX2肉瘤射频消融(RFA)治疗早期效果的价值。方法 14只新西兰白兔双侧后肢接种VX2肉瘤建模,一侧后肢VX2肉瘤接受超声引导下RFA治疗(RFA组),对侧后肢不进行射频治疗(对照组)。RFA治疗后2 d行DWI-MRI检查,治疗后3 d行PET/CT检查。分别计算肿瘤病灶和消融灶表观弥散系数(ADC)值和标准摄取值(SUV)值。根据外科切除病灶组织病理学检查结果金标准,分别对DWI-MRI、PET/CT及两者联合等3种方法评估RFA瘤灶行临床诊断一致性Kappa检验。结果 VX2肉瘤RFA前,DWI-MRI显示T1低信号,T2高信号,T1加权像环状强化,PET/CT显示18F-FDG呈结节状或环状聚集;消融后DWI-MRI显示T1高信号,T2轻度高密度,T1加权像轻度强化,PET/CT显示18F-FDG浓聚程度减低。消融瘤灶ADC值为(1.52±0.24)×10-3mm2/s,明显高于未消融瘤灶(1.09±0.12)×10-3 mm2/s(P<0.05);SUV值为(0.60±0.30),明显低于未消融瘤灶(9.60±3.20)(P<0.05)。单独DWI-MRI与单独PET/CT评估结果的敏感性、特异性及准确性与组织病理学诊断结果的一致性Kappa值分别为0.357和0.428,无显著性差别(P>0.05),DWIMRI联合PET/CT评估结果与组织病理学诊断结果的一致性Kappa值为0.786,与前两者均有显著性差别(P<0.05)。结论 DWI-MRI显像ADC值和FDG-PET/CT显像SUV值是评估RFA治疗早期效果的有临床应用价值的指标。DWI-MRI与FDG-PET/CT诊断肿瘤病灶治疗效果各具优势,两者联合应用可有效提高疗效评估的准确性。

Objective To discuss the value of diffusion-weighted MRI（DWI） and18F-FDG-PET/CT in assessing the early therapeutic effect of radiofrequency ablation（RFA） for VX2 sarcomas in experimental rabbits.Methods VX2 sarcoma was inoculated at bilateral hind limbs in 14 New Zealand white rabbits to establish the animal models.The implanted VX2 tumor on one hind leg was treated with ultrasound-guided percutaneous RFA（study group）,while no RFA was given to the VX2 tumor on the contralateral hind leg（control group）.DWI-MRI was performed at 2 days after RFA,and18F-FDG-PET/CT examination was employed at 3 days after RFA.The mean apparent diffusion coefficient（ADC） values and standard uptake value（SUV） of the untreated tumor and the ablated tumor were separately calculated.Taking the pathologic result as the gold standard,the consistency of DWI-MRI,PET/CT as well as the combination of DWI-MRI and PET/CT with the clinical diagnosis was separately evaluated by Kappa test.Results Before RFA,DWIMRI demonstrated that the VX2 tumor was characterized by hypo-intensity signal on T1 and hyper-intensity signal on T2 with ring-shaped enhancement on T1-weighted image; PET/CT showed that the tumor had nodular or ring-shaped18F-FDG accumulation.After RFA,DWI-MRI revealed that the VX2 tumor was manifested as hyper-intensity signal on T1 and slight higher density on T1 with slight enhancement on contrast-enhanced T1-weighted image; PET/CT showed lowered accumulation of18F-FDG.The mean ADC value of the ablated tumor was（1.52 ± 0.24） × 10^-3mm^2/s,which was obviously higher than that of the unablated tumor,that was（1.09 ± 0.12） × 10^-3mm^2/s,the difference was statistically significant（P〈0.05）.The mean SUV value of the ablated tumor was（0.6 ± 0.3）,which was significantly lower than that of the ablated tumor（9.6 ± 3.2,P〈0.05）.No significant difference in sensitivity,specificity and accuracy existed between DWI-MRI and pathology as well as between PET/CT and pathology,the Kappa value being 0.357 and 0.428respectively（P〉0.05）.The Kappa value of the consistency between combination of DWI-MRI with PET/CT and pathology was 0.786,which was significantly different from the result by simple DWI-MRI or simple PET/CT evaluation（P〈0.05）.Conclusion Both ADC value of DWI-MRI and SUV value of PET/CT are useful indexes for evaluating the early therapeutic effect of RFA.Both DWI-MRI and PET/CT have their respective advantages,nevertheless,combination use of both can effectively improve the evaluation of curative effect for VX2 tumor after RFA in experimental rabbits.