Study Effect Of Dose Distributions In Nasopharyngeal Carcinoma For Anatomic Changes During The First Course Intensity Modulated Radiotherapy

The purpose of study is to analyse the effect of anatomic changes during the frist coures intensity modulated radiotherapy in nasopharyngeal carcinoma,ten patients were enrolled in this study.Calculating the dosimetry variations of targets、 organs at risk using the adaptive radiotherapy software along with the increase of treatment times;comparing differences of dose calculation between MVCT and KVCT with cheese phatom,there were ten set images in MVCT and KVCT,respectively.The results showed that the sizes of head and neck outlines 、 left 、 right parotid glands shrinked obviously,the maximum rate in transverse diameters were:-12.938%、-35.124%、-40.161% and average rate were:-4.453% 、-13.391% 、-12.606%( at 25 th fraction), respectively,the maximum and average rate of left、 right parotid glands in anteroposterior diameters were:-30.854%、-34.351% and-10.366%、-11.566%(at 25 th fraction),respectively;the results of dose caculations in MVCT and KVCT weren’t exceeding ±5%.The advantages of intensity modulated radiotherapy technique are steep dose gradients and high conformal degree, treatment is sensitive to anatomical changes,it is necessary to revise the radiotherapy plan of nasopharyngeal carcinoma patient in time in the whole radiation course.