Chlinic Dosimetric Research For Cervical Cancer Patients Received Intensity-modulated Radiation Therpy

Objective:To analyze the impact of different states of bladder and the cervix cancer regression on the motion of cervix during the intensity-modulated radiotherapy(IMRT) for cervical cancer.At the same time to analyze the clinical dosimetric difference of the target and the baldder and the rectum in the defferent states of bladder.To provide referrence for the clinical appliance.Methods: This experiment is divided into two parts. One part is to investigate the motion of cervix cancer.We collect 10 patients overseeded IIB stage,which was performed according to the international Fedration of Gynecology and Obstetrics(FIGO).We divide all this patients into two groups.One group is to keep the rectum in the full states. To scan CT with thermoplastic model in full and semi-full and empty states of bladder. To 3 use SPSS15.0 statistical software to analyse the cervix cancer and uterus motion in the diferrent states of bladder. In the other group,we analyse the cervix cancer and uterus motion when the tumor is shrunk for the radiotherapy when these 5 patients is in the natrual states. The other part is to transmit the first group data to the corvus nomos treatment planning system(TPS). All patients with diferrent states of bladder were treated with IMRT, 46Gy in 23 fractions. Analyze the dosimetric rules of the bladder and the rectum in the diferrent states of bladder.Results: (1)when the rectum is kept in the full states, diferrent states of bladder have diferrent effects on the motion of cervix cancer. In the direction of R/L (Right/Left),the motion is minimum; in the direction of A/P(Anteriorly/Posteriorly),when bladder's volume is gradualy increased ,the cervix is gradualy moved to the posteriorly .The maximum motion is 19.1mm ;in the direction of S/I(Superiorly/Inferiorly),when the bladder's volume is gradualy increased ,the cervix is gradualy moved to the dierection of inferiorly. The maximum motion is 18.5mm.when the rectum is kept in the full states, diferrent states of bladder have diferrent effects on the motion of uterus. In the direction of R/L ,the motion is minimum; in the direction of A/P,when bladder's volume is gradualy increased ,the uterus is gradualy moved to the posteriorly .The maximum motion is 20.83mm ;in the direction of S/I,when the bladder's volume is gradualy increased ,the uterus is gradualy moved to the dierection of superiorly. The maximum motion is 12.23mm.(2)when we use IMRT to treat cervical cancer ,the cervix regression is considerably evident. During the treatment,the motion of the cervix cancer is small,the motion of uterus is large gradualy moved to the inferiorly. The maximum motion is 30.12mm. (3) IMRT plans are derived by use of inverse TPS(corvus,nomos Inc.)in three states of bladder.When we use the volumes of 25Gy,30Gy,35Gy,40Gy,45Gy doses to the bladder and rectum to stastis the irradiated volumes to them,we find that the irradiated volumes of bladder and rectume are least when the bladder is full.(4) Doses to 33% and 67% of the volumes of bladder and rectum have no stastical difference,in the other words ,when we use this parameter ,the doses to bladder and rectum have no dosimetric difference. Doses to 100% of the volume have stastical difference,in the other words ,when we use this parameter ,the doses to the bladder and rectum is distinctly decreased. When we use the doses to 5%,10%,20%,30%,40%,50%,0.1cc,1cc,2cc of the volumes of the bladder and rectum,we find that when the bladder is full,the doses to it is least,when the bladder is semi-full,the doses to the rectum is least.Conclusions : (1) The diferrent states of bladder have such effect on cervix cancer motion :in the direction of R/L,the motion of cervix is trivial ;in the direction of A/P and I/S.the the cervix cancer is gradualy moved to the Posteriorly-Inferiorly direction with baldder's volume gradualy increased. The diferrent states of bladder have such effect on uterus motion :in the direction of R/L,the motion of cervix is trivial ;in the direction of A/P and I/S.the the cervix cancer is gradualy moved to the Posteriorly-Superiorly direction with baldder's volume gradualy increased. (2) During the course of radiotherapy ,the cervix regression have small effect on cervix cancer motion ,whereas have large effect on the uterus mostly in the S/I direction.(3) IMRT can increase the dose of the target,. (4) When we use IMRT to treat cevical cancer,we must consider the organ motion and the tumor's regression, the margins of CTV to PTV are unequally.(5) When the bladder is full,the irradiated volumes of bladder and rectum is least; when the bladder's volume is gradualy increased, the irradiated doses of bladder and rectum is gradualy decreased.