Objective: To compare the accuracy of 18F-FDG PET/CT in measuring the tumor metabolic volume (MTV) of primary tumor volume of cervical squamous cell carcinoma based on different thresholds of maximum standardized uptake value (SUVmax) (iterative adaptive algorithm and 30%

40%

50%). Methods: All the included patients withⅠB-ⅣA stage cervical squamous cell carcinoma underwent 18F-FDG PET/CT and MRI. Threshold MTV method was used to calculate the lesion volumes with different fixed thresholds (30%

40% and 50% SUVmax) and MTV iterative method was used to calculate the lesion volume directly through AW VolumeShare5 system

and MRI was used to measure the tumor volume in transverse and sagittal position on T2WI by Reformat software. Taking MRI measurement results (MRIv) as the "gold standard"

the differences between the results of different MTV measurement methods and MRI were compared

and the linear fitting and correlation analysis were conducted between MTVs and MRIv

and finally the ROC curve was drawn to compare the accuracy. Results: A total of 117 patients met the inclusion criteria. The MTV30%method and the MTViterativemethod were closest to MRIv results

with linear correlation closer to the diagonal; the MTViterativemethod had the strongest correlation with MRIv (r=0.98

P=0.000)

followed by MTV30% (r=0.96

P=0.000); the ROC curve showed that the MTV30%method and the MTViterative method were close to the measurement of lesions (z=0.145

P=0.885). Conclusion: MTViterativemethod and MTV30%methods are more accurate in the calculation of lesion size and target delineation of cervical squamous cell carcinoma

which can be used as a reliable basis for the diagnosis and treatment of cervical squamous cell carcinoma.