Objective To evaluate the dosimetric impact of interfractional bladder fullness variation in volumetric modulated arc therapy for cervical cancer using artificial intelligence-assisted cone-beam CT(CBCT)image segmentation,and propose an imaging-based quantitative assessment criterion for bladder fullness,providing an objective basis for assessing bladder filling status during clinical treatment.Methods Fifty patients receiving volumetric modulated arc therapy for cervical cancer were selected.The criterion for determining bladder fullness was as follow:if the bladder longitudinal diameter measured on the CBCT mid-sagittal plane was greater than half of the bladder longitudinal diameter measured on the localizable CT,it was defined as≥50%bladder fullness;otherwise,it was defined as<50%bladder fullness.Based on this criterion,two CBCT images were selected for each patient(representing fractions with≥50%and<50%fullness,respectively).Borui auto-contouring system was applied to re-contour the target areas and organs at risk,followed by dose recalculation.Results Compared with≥50%bladder fullness group,<50%bladder fullness group had significantly increased bladder V40,and small bowel Dmax,Dmean,V55,V45,V40(P<0.05),indicating that during interfractional radiotherapy,a CBCT-measured bladder longitudinal diameter less than half of the bladder longitudinal diameter measured on the localizable CT could serve as a predictor for significantly increased radiation dose to the bladder and small bowel.Correlation analysis revealed that bladder volume change showed a positive correlation with bladder Dmax change(R=0.45),a significant negative correlation with bladder V30(R=-0.37),and negative correlations with small bowel Dmax,Dmean,V55,V45,V40(R=-0.31,-0.41,-0.39,-0.49,-0.61).The correlation results indicate that increasing bladder fullness could reduce the radiation dose to the bladder and small bowel.Conclusion Artificial intelligence-assisted segmentation confirms that in interfractional radiotherapy for cervical cancer,when the CBCT-measured bladder longitudinal diameter is less than half of the longitudinal diameter measured on the localizable CT,there is a significant increase in radiation dose to OAR.Maintaining an ideal state of bladder fullness contributes to reducing the radiation dose to the bladder and small bowel.It is crucial to provide patients with adequate bladder management education before treatment and implement strict bladder volume management strategies during treatment fractions.

Objective To evaluate the dosimetric impact of interfractional bladder fullness variation in volumetric modulated arc therapy for cervical cancer using artificial intelligence-assisted cone-beam CT(CBCT)image segmentation,and propose an imaging-based quantitative assessment criterion for bladder fullness,providing an objective basis for assessing bladder filling status during clinical treatment.Methods Fifty patients receiving volumetric modulated arc therapy for cervical cancer were selected.The criterion for determining bladder fullness was as follow:if the bladder longitudinal diameter measured on the CBCT mid-sagittal plane was greater than half of the bladder longitudinal diameter measured on the localizable CT,it was defined as≥50%bladder fullness;otherwise,it was defined as<50%bladder fullness.Based on this criterion,two CBCT images were selected for each patient(representing fractions with≥50%and<50%fullness,respectively).Borui auto-contouring system was applied to re-contour the target areas and organs at risk,followed by dose recalculation.Results Compared with≥50%bladder fullness group,<50%bladder fullness group had significantly increased bladder V40,and small bowel Dmax,Dmean,V55,V45,V40(P<0.05),indicating that during interfractional radiotherapy,a CBCT-measured bladder longitudinal diameter less than half of the bladder longitudinal diameter measured on the localizable CT could serve as a predictor for significantly increased radiation dose to the bladder and small bowel.Correlation analysis revealed that bladder volume change showed a positive correlation with bladder Dmax change(R=0.45),a significant negative correlation with bladder V30(R=-0.37),and negative correlations with small bowel Dmax,Dmean,V55,V45,V40(R=-0.31,-0.41,-0.39,-0.49,-0.61).The correlation results indicate that increasing bladder fullness could reduce the radiation dose to the bladder and small bowel.Conclusion Artificial intelligence-assisted segmentation confirms that in interfractional radiotherapy for cervical cancer,when the CBCT-measured bladder longitudinal diameter is less than half of the longitudinal diameter measured on the localizable CT,there is a significant increase in radiation dose to OAR.Maintaining an ideal state of bladder fullness contributes to reducing the radiation dose to the bladder and small bowel.It is crucial to provide patients with adequate bladder management education before treatment and implement strict bladder volume management strategies during treatment fractions.

Objective:To design and evaluate the application value of intracavitary-interstitial brachytherapy (IC-ISBT) applicator template for locally advanced cervical cancer.Methods:MRI data of 100 patients with ⅡB-ⅣA stage cervical cancer (International Federation of Gynecology and Obstetrics 2018 staging system) before and after external beam radiation therapy (EBRT) admitted to Sun Yat-sen University Cancer Center from March 2019 to September 2020 were collected. The range of primary cervical lesions was retrospectively analyzed and compared. Based on the residual mass of patients, the corresponding high-risk clinical target volume (HR-CTV) was delineated, and the IC-ISBT applicator template was designed and initially applied to cervical cancer patients. Dosimetry analysis and efficacy evaluation were compared between the applicator template-guided ( n=37) and free-hand implantation groups ( n=63). Chi-square test or Fisher exact test was performed for categorical variables, and t-test or U-test for continuous variables. Results:The median distance between the residual tumor margin (clockwise 3, 6, 9, 12 o'clock) and the center of 100 patients with ⅡB-ⅣA stage cervical cancer after EBRT was 16.5, 14.0, 17.0 and 13.0 mm, respectively. The corresponding HR-CTV was superimposed to reconstruct the three-dimensional diagram, and the cylindrical IC-ISBT applicator template with mushroom-like head was designed and manufactured: the longest and shortest diameter of the head was 35 and 20 mm, respectively; the central channel was adapted to the uterine tube, the C1-C12 channels was arranged in inner circle, and the peripheral B1-B5 and A1-A4 pin channels were expanded bilaterally. In terms of dose coverage, there was no significant difference between the HR-CTV D 90% [(635.12±22.65) vs. (635.80±25.84) cGy], bladder D 2 cm3 [(473.79±44.78) vs. (463.55±66.43) cGy)], rectum D 2 cm3 [(396.99±73.54) vs. (408.00±73.94) cGy] and sigmoid colon D 2 cm3 [(293.07±152.72) vs. (311.31±135.77) cGy] between the template-guided and free-hand implantation groups (all P>0.05), but the HR-CTV D 98% was significantly higher [(544.78±32.07) vs. (536.78±32.04) cGy, P=0.007] and the rectum D 1 cm3 and D 0.1 cm3 were significantly lower [(438.62±69.65) vs. (453.97±67.89) cGy, P=0.016; (519.46±70.67) vs. (543.82±81.24) cGy, P=0.001] in the template-guided implantation group. In addition, there was no significant difference in the complete response rate between two groups (86% vs. 83%, P>0.05). Conclusions:This IC-ISBT applicator template is reasonably designed, and the therapeutic efficacy of the template-guided implantation is equivalent to that of free-hand implantation. The dose coverage of the target area meets the clinical demand with a better protection of the organs at risk. The applicator template has the potential to be widely used as a conventional template in clinical practice as the applicator-guided implantation is convenient to operate and repeat.