Applications of Low Energy Megavoltage X-ray Beams in Cancer Radiotherapy

A review on the applications of low energy megavoltage (MV) X-ray beams (1-4 MV) in cancer radiotherapy is presented. Firstly, the physical characteristics of low energy megavoltage X-ray beams are reviewed in terms of penumbra, dose fall-off, exit dose, dose to bone, penetration power, skin dose and image quality. Secondly, the therapeutic applications of low energy megavoltage X-rays in cancer radiotherapy are further stratified and discussed based on X-ray energy levels. Thirdly, a systematic review of imaging applications of low energy megavoltage X-ray beams in image-guided radiation therapy (IGRT) and megavoltage fan beam computed tomography (MVFBCT) is provided. Finally, we summarize the latest development of low energy megavoltage X-ray beams in cancer radiotherapy and cancer imaging during the past twenty years. With their intrinsic physical characteristics, it is feasible to achieve personalized radiotherapy and personalized imaging protocols for individual patient. However, further technological developments and more clinical data would be needed to fully exploit the potentials of low energy megavoltage X-ray beams in the personalized radiotherapeutic management of cancers.