Bladder anatomical changes and dose variation during the course of intensity-modulated radiation therapy of cervical cancer

Objective To investigate bladder anatomical changes and dose variation in patients with cervical cancer.Methods We analyzed 20 patients,undergoing external beam radiotherapy scanning cone beam CT(CBCT)before each fraction.Bladder was contoured on each CBCT,was projected onto the planning CT and assesses anatomical changes and dose variation.Results A total 451 CBCT images,for 20 patients were collected for analysis,show more change in bladder volume and position.In 15 cases bladder volume and V45 had no significant correlation(r=0.225 -0.473,all P>0.05),4 cases shows negative correlation(r=-0.564,P<0.05;r=-0.597,P<0.01;r=-0.942,P<0.01;r=-0.816,P<0.01),1 case shows positive correlation(r=0.662,P<0.01).Have more than the criteria(V45≤50%)number is 64/451(14.2%)in whole treatment.Conclusions For most patients by filling adequacy bladder,bladder dose variation is acceptable:CTV lager for individual patients should be closely observed its regression,implementation of the offline or online calibration. Key words: Volume and position changes of bladder; Bladder dose variation; Tomography,Xray computed,cone-beam;  Cervical neoplasms/intensity-modulated radiotherapy