Proton CT of a human skull

3D rendering of the skull of an adult male receiving X-ray radiotherapy, viewed from the side. A clinical proton CT has not yet been produced to date. This is a simulation using X-ray data of a patient receiving radiotherapy where every X-ray event has been converted to its proton equivalent. 180 image projections were then processed using a new algorithm to create the image seen here. Proton beam radiotherapy is rapidly becoming a recognised treatment for certain cancers, especially in children and young people. To target the tumour site while minimising the exposure to healthy surrounding tissue it is necessary to image using the same particles (protons) that are used for therapy. The advantage of using high-energy treatment protons to construct the CT scan instead of much lower energy X-ray photons is that registration errors are reduced from ±4% to less than ±1%. Proton therapy could be used in many more cases and with better outcomes.