Dosimetric comparison of Cervix uteri irradiation with 9 equal spaced fields IMRT and beam angle optimized IMRT / 中华放射肿瘤学杂志

ABSTRACT

Objective To study the dosimetry characteristics of 9 equal spaced fields and 9 fields with beam angle optimization (BAO) process for cervix uteri.Methods 12 cervix uteri cancer patients CT Images were transferred into Eclipse planning system.Each patient,the 9 equal spaced fields and 9 fields by BAO process were IMRT plan designed with the same CT image.Make a evaluation of dose distribution for target volume and OARs,and paired t test for them.Results Comparing to 9 equal spaced fields IMRT plan,the quality of 9 fields IMRT plan with BAO process the the PTV V95％ was 99.31％ vs 99.42％,P =0.020,at the same time V105％,V110％,Dmax,D got 60.54％ vs 47.92％,P =0.013;7.14％ vs 0.37％,P =0.000;56.62 Gy vs 55.47 Gy,P =0.000;53.29 Gy vs 52.72 Gy,P =0.000,the CI and HI was 0.85 vs 0.89,P =0.000 ;0.10 vs 0.13,P =0.000.For organs at risk,bladder V40 was increased by 4.7 ％ (P =0.013) ;the D40 of rectum was 0.5 Gy higher (P =0.004) ; the small bowel's DVH showed that V40 and Dmax increased by 0.6％ (P =0.015) and 1.4 Gy (P =0.000),D of bone marrow were raised separately by 1.3 Gy (P =0.000),the spinal cord's dose D0.1 cm3 was also increased by 2.0 Gy (P =0.000).Conclusion The quality of 9 equal spaced fields IMRT plan will be better than those achieved by BAO process optimized plans.