Dosimetry Study Of Intensity Modulated Radiotherapy And Three-dimensional Conformai Radiotherapy For Prostate Cancer

Objective: To investigate the dosimetry differences of intensity modulatedradiotherapy (IMRT) and three-dimensional conformal radiotherapy (3D-CRT) forprostate cancer.Method：Ten patients treated with radiotherapy in our hospital from February2012to June2013were selected in the research. All patients were underwentcomputed tomography simulation with the preparation of bowl. According to thecontoured targets,3D-CRT and IMRT plans were designed for each patient with theprescription dose of78Gy,5fractions per week,2Gy per fraction and all the patientswere treated with a6-MV X-ray beam from a medical linear accelerator. After all, weevaluated V95%、D95、Dmin、Dmean、Dmax、CI、HI of PTV, V70、V60、V50、V40、MLD of the rectum, V70、V50、MLD of the bladder, and V50of the femoral headsby the dose volume histogram(DVH) to made the statistical analysis.Results: V95%of PTV in IMRT and3D-CRT plans was99.01%and94.75%,CI、HI in the two methods were0.81、1.07and0.58、1.09respectively（P<0.05）,showing that the two methods both had a good target coverage, but IMRT plansshowed a significant superior uniformity and conformity over3D-CRT plans. Otherdosimetry parameters of PTV also presented this tendency. Compared with3D-CRTplans, V70、V60、V50of the rectum in IMRT plans were lower(9.6%、20.0%、29.7%vs23.3%、43.7%、53.1%, P<0.01), and V70、V50of the bladder were decreased by6.2%、7.4%（P<0.02）, V50of the femoral heads was declined by3.0%（P<0.01）.Conclusions: Present calculations support the hypothesis IMRT can improve theconformity index and dose distribution of the target and limit dose to normal tissue byreducing treatment margins relative to conventional3D planning, to allow a reduction in complication rate spanning several sensitive structures while maintaining orincreasing tumor control probability. Therefore, IMRT has a significant therapeuticsuperiority in the treatment of prostate cancer.