Dosimetric Study of Intensity Modulated Radiotherapy in Nasopharyngeal Carcinoma

Objective: To analyze the doseimetric characteristic on various target and surrounding organs in intensity modulated radiotherapy(IMRT) for firstly-diagnosed nasopharyngeal carcinoma(NPC).Methods: From September 2006 to March 2007,40 primary NPC treated with IMRT were enrolled to this dosimetric study.The prescription dose for target volume was PTVnx68 Gy~74 Gy,PTVnd 62 Gy~70 Gy,PTV160 Gy~64 Gy,PTV2 54 Gy,respectively.The nasophynx and upper neck were treated with IMRT,and the node areas of lower neck and top of clavicle were uniformity irradiated with a single conventional anterior portal.Then the dose distributions of tumor volume and organ at risks were studied.Results: The Dmin,Dmax,Dmean,D95 of PTVnx and PTVnd were 60.9 Gy,81.2 Gy,76.7 Gy,71.2 Gy and 57.2 Gy,78.2 Gy,73.2 Gy,66.5 Gy,respctively.The Dmax of lens,optical nerve,optical chiasma,pituitary,temporal mandibula joint were 6.7 Gy,43.8 Gy,45.6 Gy,47.4 Gy,57.4 Gy,respctively.The dose of 1 cm3 spinal cord(D1cc),3 percent of brain stem volume(D3),10 percent of temporal lobe volume(D10),50 percent of parotid gland volume(D50) were 40.8 Gy,51.4 Gy,50.4 Gy,32.3 Gy.Conclusion: IMRT could provide quite good dose distributions not only to the tumor target but the surrounding organs.