Intensity-modulated radiation therapy (IMRT) is one of the most important techniques for the treatment of head and neck cancers. During IMRT

the accuracy of radiation dose delivery is limited by errors in patient treatment positioning

inter-treatment

and intra-treatment variation of organ position

size

and shape. Image-guided radiation therapy (IGRT) may partly correct these errors and further improve the radiation dose delivery. However

the dose deviation caused by internal organ motion or non-rigid motion cannot be simply solved by IGRT technique. Nowadays

adaptive radiation therapy (ART) has been introduced to minimize the negative effects of treatment position uncertainty which normally exist in either IMRT or IGRT

and to compensate the target coverage and clinical outcome. Based on the patient’s pre-treatment images and relative information such as dose deviation

ART may provide a better strategy for online treatment. Under the help of ART technique

radiotherapy can be more accurate and more personalized.