| Objective:To analyze the influence of the change of bladder volume on the radiation dose to normal tissues during the treatment of local advanced cervical cancer with intensity-modulated radiotherapy,and provide reference and help for the research unit in the treatment of cervical cancer with external radiation.Materials and methods:A total of 54 patients with locally advanced cervical cancer who underwent prevention of external beam intensity-modulated radiotherapy after radical resection of cervical cancer in our department from December 2018 to December 2020 were selected.The FIGO staging is IB2,IB3 and IIA2.Perform CT simulation positioning,and instruct the patient to hold back the urine to a comfortable state and prepare the bowel before positioning.The target area and organs at risk were delineated,and a physicist carried out a plan design on the Varian Eclipse13.5 treatment planning system.The prescribed dose PTV was DT 50 Gy,2.0Gy/time,5 times/week.After the plan is completed,the target area and organ-at-risk limits will be evaluated according to the DVH chart and isodose curve.The bladder volume was measured on the location CT simulation image.According to the bladder volume,54 patients were divided into 3 groups,group A: bladder volume V≤200ml;group B: 200 ml < bladder volume V ≤ 400ml;group C:bladder volume V>400ml.And calculate the D2 cc,D1cc and D0.1cc of each patient’s bladder and rectum,and D1% of bilateral femoral heads in the treatment planning system.Use SPSS 22.0software to analyze the dosimetry data among the three groups.Result:Bladder exposure dose: There were significant differences in the dose values of bladder in different bladder volume groups(P<0.05).The results showed that the dose of 200～400ml bladder volume was less than that of 0～200ml bladder volume(P=0.014)and more than 400 ml bladder volume(P=0.027)in D0.1cc group;In D1 cc group,the dose of 200～400ml bladder volume was less than that of 0～200ml bladder volume(P = 0.04),and it was also less than that of 400 ml bladder volume(P = 0.02);In D2 cc group,the dose of200～400ml bladder volume was less than that of 0～200ml bladder volume(P = 0.037),and it was also less than that of more than400 ml bladder volume(P = 0.026).In conclusion,the dose of D0.1cc,D 1cc and D 2cc was the lowest in the bladder volume between 200 ml and 400 ml,which were(50.86±2.75)Gy、(50.37±77)Gy and(50.20±2.72)Gy。Rectal exposure dose: The rank sum test was performed on each group.There was no statistically significant difference in exposure dose values measured by different bladder volume groups(P>0.05).It is not yet believed that the results of rectal exposure doses are different when the bladder volume is 0～200ml,200～400ml and 400 ml or more.Exposure dose of bilateral femoral heads: analysis of variance was performed for each group;there was no statistically significant difference in exposure dose values measured by different bladder volume groups(P>0.05),It is not yet believed that the average exposure dose of bilateral femoral heads is different when the bladder volume is 0～200ml,200～400ml and 400 ml or more.Conclusions:1.In intensity-modulated radiotherapy for locally advanced cervical cancer,the filling state of the bladder changes the radiation dose of the bladder.2.The filling state of the bladder has no significant effect on the radiation dose of the rectum and bilateral femoral heads.3.The best bladder holding urine volume is between 200～400ml,which can minimize the radiation dose of the bladder,which may reduce the probability of radiation cystitis caused by radiotherapy. |
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