Purpose:The purpose of the present thesis was to study the effect of the 3D printed bolus in intensity-modulated radiation therapy of nasal cavity tumor.Methods:A uniform 1cm thickness 3D bolus was designed based on a anthropomorphic head phantom and printed out using 3D printer.Then,the anthropomorphic phantom was simulated twice with and without the 3D bolus,respectively.A virtual tumor model was added to both CT simulations.GTV,CTV and OARs were designed as 5 mm to the body surface.PTVs were formed with a uniform 5 mm margin.A 6Mv X-ray,7 beam IMRT planning was optimized with a dose prescription of 55 Gy to PTV-GTV and 50 Gy to PTV-CTV with and without 3D bolus,respectively.After completion of the IMRT plan,EBT3 film was used to verification the dose distribution on the anthropomorphic phantom with 3D bolus.In addition,three points,two in the relative flat area and one in one side of the nose,were chosed to verify the aboslute dose.Gamma analysis was performed by using the QALAB software.Results:The target area fitness index(CI)and the uniformity index(HI)were analyzed between these two groups.(1)In the group A,There was a high dose area(69.5Gy highest)near the superficial skin of tumor,which could not meet the clinical dose requirements.(2)In the group B the superficial tumor target dose was uniform and the maximum dose was 61.9Gy,the PGTV(V95%)was 55.1Gy and PCTV(V95%)was 50.5Gy,which was in accordance with the clinical requirements.Besides,the group B decreased skin dose better than other groups.The percentage of validity was 94.6%in the QALAB film gamma analysis(3%3mm)and the Deviation of there point results are less than 1.5%between TPS and measure.Conclusions:Using the 3D printed bolus can improve the ontcomes of IMRT planning for nasal cavity tumor,especially for those located superficial to the skin.Future studies are needed to verify this result.