Objective: To investigate the dosimetric effects of computed tomography（CT） images-based reconstruction uncertainties of the tip of the stainless-steel Fletcher applicator on three-dimensional intracavitary brachytherapy for cervical cancer. Methods: We selected 20 patients with cervical cancer who completed treatment

and directly modified the offset values of their original brachytherapy plans to simulate the dose distribution at ± 1 mm

± 2 mm

and ± 3 mm reconstruction uncertainties of the applicator tip. We obtained the D

100

D

90

D

50

V

200

V

150

V

100

and V

90

values for high-risk clinical target volume（HR-CTV） and intermediate-risk CTV（IR-CTV）

the D

0.1cc

D

1 cc

D

2cc

and D

5cc

values for the bladder

rectum

sigmoid colon

and small intestine

and the conformity index values to analyze the dosimetric effects of applicator tip reconstruction uncertainties on three-dimensional intracavitary brachytherapy for cervical cancer. Results: The deviation of dose-volume histogram（DVH） parameters for HR-CTV and IR-CTV increased with the increase in applicator tip reconstruction uncertainty（P

<

0.05）. For a fixed applicator tip reconstruction uncertainty

the deviation of DVH parameters for HR-CTV increased with the increase in volume or dose（P

<

0.05）;the deviation of dose parameters for IR-CTV increased with the increase in volume（P

<

0.05）

while the deviation of volume parameters decreased with the increase in dose（P

<

0.05）. The dose deviation for organs at risk（OARs） increased with the increase in applicator tip reconstruction uncertainty（P

<

0.05）. For a fixed applicator tip reconstruction uncertainty

there were differences in dose deviation changes between different OARs. For the bladder

the dose deviation increased with the increase in volume（P

<

0.05）. For the rectum and sigmoid colon

the dose deviation decreased with the increase in volume（P

<

0.05）. For the small intestine

there was no significant association between the dose deviation and volume（P

>

0.05）. When the applicator tip reconstruction uncertainty was 2 mm

the dose deviation was 3.58% for D

90

of HR-CTV

2.84% for D

90

of IR-CTV

3.4% for D

2cc

of the bladder

3.47% for D

2cc

of the rectum

3.99% for D

2cc

of the sigmoid colon

and 2.10% for D

2cc

of the small intestine. Conclusion: The applicator tip reconstruction uncertainty should be within ±1 mm. The slice thickness of CT scanning should not exceed 3 mm.