Dosimetric Study Of Intensity Modulated Radiation Therapy And Three-dimensional Conformal Radiation Therapy For Malignant Gliomas

Objective: To investigate the dosimetric differences between IMRT and3D-CRT for malignant gliomas, and provide a reference to select differentradiotherapy techniques for clinical treatment.Materials and methods: We selected14patients of malignant gliomas whowere treated in the department of radiotherapy of cancer center in the firsthospital of jilin university from2010to2011for study.All patients were treatedwith thermal head mold for immobilization and Siemens24rows of largediameter spiral CT simulator for scanning and positioning, the reconstructedimage was transmitted to the Pinnacle system, and doctors contoured targetvolumes and organs at risk based on MRI images. All patients were made bothIMRT and3D-CRT plans,and given the same dose prescription for dosimetricstudy. Studying the dose distribution of target volume and protection of organsat risk by dose volume histogram (DVH) and plan dose (PD).We compared thedose distribution of target (HI,CI,Dmax,Dmin,Dmean,D95and V95),organs atrisk (Dmax,Dmean,D5and D33) between the two plans．Results:1IMRT was better than3D-CRT in Dmax,Dmean,Dmin,D95andCI (P <0.05), but there was no significant difference in V95and HI betweenIMRT and3D-CRT and they both satisfy the requirement.2protection oforgans at risk:(1) IMRT was better than3D-CRT in the protection of brainstem,optic nerve, optic chiasm and pituitary (P <0.05). Compared with3D-CRT,IMRT’s Dmax, Dmean and D5of brain stem were decreased by13.14%,16.24%and18.67%; the Dmax, Dmean and D5of optic chiasm weredecreased by16.54%,21.76%and13.88%; the Dmax and D5of optic nerves were decreased by13.23%and14%; Dmax, Dmean and D33of pituitary weredecreased by23.72%,28.68%and26.29%.(2)3D-CRT is better than IMRT inthe protection of lens and eyes,(P <0.05), but they were both less than thesafety dose limits.Conclusion: Both IMRT and3D-CRT can be good to satisfy therequirement of Clinic dosimetry,dosimetry coverage of the target volume andhomogeneity,but IMRT has better conformity and less dose of organs at riskthan the3D-CRT.