Abstract： Objective To observe the change of 18F-Fluorodeoxyglucose positron emission tomography-computed tomography (18F-FDG PET-CT) imaging on lung tumors after treatment of Argon-Helium (Ar-He) cryoablation,and to search the measure for evaluating the short-term curative effect after treatment of Ar-He cryoablation.Methods 19 focuses of 15 patients had completed the treatment of Ar-He cryoablation.All of patients imaged with 18F-FDG PET-CT in six months after Ar-He cryoablation.7 patients of all imaged with 18F-FDG PET-CT pre- and after Ar-He cryoablation.The others only imaged with 18F-FDG PET-CT after cryoablation,but these focuses could compare with tissues near the focus or other tumors in themselves.Results 18F-FDG PET-CT imaging found that there was no accumulation of radionuclide in 13 of 19 focuses after cryoablation and there was no new tumor in follow-up.Two target region of cryoablation,which grew up in mediastinum,were found radiation defect with distinct boundary and expanding outward during 4 months.The other 4 focuses recurred during 6 months in which there was accumulation of radionuclide after cryoablation.There was significant change about SUVmax of focuses after cryoablation by qualitative and quantitative analysis (t =3.784,P ＜0.05).But the changes of SUVmax had no significant difference in different time,between cryoablation and PET-CT imaging (F =0.106,P ＞0.05).Conclusion 18F-FDG PET-CT imaging really reveals the range and effect of Ar-He cryoablation.It is an optimal measure for evaluating the short term curative effect after Ar-He cryoablation.