兔VX2移植瘤氩氦刀治疗前后^18F-FDG PET／CT显像及病理学变化

^18F-FDG PET/CT for the evaluation of pathological changes of the VX2 rabbit tumors after treatment of Ar-He knife

目的研究兔VX2移植瘤氩氦靶向冷冻治疗系统（简称氩氦刀）治疗后PET／CT显像及病理学的变化，观察治疗后肿瘤组织的演化过程，探索氩氦刀治疗后疗效评价的方法。方法36只日本大白兔在兔VX2肿瘤种植后第4周，进行^18F-脱氧葡萄糖（FDG）PET／CT显像；显像后进行氩氦刀治疗。术后按随机数字表将兔完全随机分为6组，每组6只。分别在氩氦刀治疗后第1，3，7，14，30和60天进行PET／CT显像；分析PET／CT图像，观察标准摄取值（SUV）的变化；第2次PET／CT显像（术后显像）后处死大白兔，取出原肿瘤组织，进行病理学检查和免疫组织化学检测，比较病理学和免疫组织化学的变化。统计软件为SPSS16．0，组间比较采用配对资料的t检验和双变量相关分析，P〈0．05为差异有统计学意义。结果氩氦刀治疗后病理学检查提示，治疗区呈现坏死-炎性反应-机化过程。CT表现：肿瘤区域术后第3天至第14天有一短暂性增大，然后呈缩小的趋势；最大SUV（SUVmax）术后第1天即出现明显下降（由治疗前2．54±1．12下降至0．67±0．12），第3天轻度升高（1．71±0．82），然后逐渐减低（治疗后第60天为0．51±0．32），治疗前后SUVmax变化差异有统计学意义（t=5．471，8．716，11．388，5．713，7．144和7．213，P均〈0．05）。治疗前后靶区面积变化与SUVmax变化相关性不明显（r=0．259，P=0．675）。治疗前后肿瘤微血管密度变化与SUVmax变化密切相关（r=0．865，P=0．032）。结论PET／CT显像可真实反映肿瘤组织氩氦刀治疗后的变化过程，是评价氩氦冷冻治疗疗效较理想的方法。

Objective To study the correlation of ^18F-fluorodeoxyglucose （FDG） PET/CT with pathological changes of the VX2 rabbit tumors after treatment of Ar-He knife, and to explore the evolution of the Ar-He knife curative effect for VX2 rabbit tumors. Methods Thirty-six Japanese white rabbits had successfully been implanted with VX2 tumors in thighs. Four weeks later, the rabbits with VX2 tumors were imaged with FDG PET/CT before they were treated with Ar-He cryoablation. The rabbits were evenly and randomly divided into 6 groups （6 rabbits in each group） and imaged with FDG PET/CT respectively on the first day, third day, seventh day, fourteenth day, thirtieth day and sixtieth day after cryoablation. The rabbits in each group were sacrificed after post-treatment FDG PET/CT imaging for pathology and immunohistochemistry studies. The standardized uptake value （SUV） of tumor regions were calculated and compared with pathology and immunohistochemistry findings in the cryoablative area in each group. Paired-samples ttest and bivariate correlation analysis were evaluated by statistical software SPSS 16.0. Results After ArHe cryoablation, pathological changes of ＂necrosis-inflanmmtory response→rganization＂ were found. On CT imaging, the tumors enlarged during 3 - 14 d after treatment and then shrank gradually. On FDG PET imaging, the maximum SUV （ SUVmax ） dropped dramatically on the first day after the operation （from 2.54 -＋ 1.12 to 0. 67 -＋ 0. 12）, and increased slightly on the third day （ 1.71 -＋0.82）, and then continually dropped to 0. 51 -＋ 0.32 （60 d after the operation）. The differences of SUVmax between pre- and after cryoablation in each stage were significant, respectively （t = 5. 471, 8. 716, 11. 388, 5. 713, 7. 144 and 7. 213, all P 〈 0.05 ）. The size and SUVmax of the targeting area did not correlate with each other （ r = 0. 259, P = 0. 675 ）. The change of the MVD closely correlated with SUVmax （ r = 0. 865, P = 0. 032）. Conclusion FDG PET/CT can reveal the pathological change of tumor tissue after Ar-He eryoablation therapy and therefore may be a potential toolfor evaluating the curative effect of this treatment modality.