Patient positioning in the proton radiotherapy era

There is currently an increasing interest in proton therapy in the world and the number of proton therapy facilities is rapidly increasing; mostly owing to the fact that physicians acknowledge that even the best current technique of X-ray therapy (intensity modulated proton therapy, IMRT) are still far from maximizing the therapeutic gain, i.e. increasing the local tumour control and decreasing the morbidity in healthy tissues. The concern about late effects for "low" doses to normal organs is particularly relevant in children. At the moment there are approximately 25 proton centres in operation worldwide and dozens of new ones are being planned. The aim of this work is to describe the most representative patient positioning solutions which are in clinical use in some proton radiotherapy centres and to comment on the advantages of robotic positioning in fixed beam delivery scenarios in terms of cost-effectiveness as compared to the moving gantry delivery solutions.The principal obstacle to the diffusion of proton therapy is the high cost for installation. Currently, proton-therapy is more expensive than photon-therapy and the high costs are mostly due to the beam delivery system. In 2003, Goitein and Jermann [1] estimated the relative costs of proton and photon therapy, concluding that, with some foreseeable improvements, the ratio of costs protons/photons was likely to be about 1.7. However, these estimates are probably outdated. Reimbursement rates currently allow the development and operation of proton-therapy facilities with a reasonable profit margin. In the future, it is likely, as these facilities reach full operational capacity that the reimbursement rates for proton-therapy treatment delivery will decrease as capital costs are spread among more patients.One of the main issues in assessing the cost-effectiveness of proton-radiotherapy is the choice between moving gantries and fixed gantries with robotic patient positioning systems. In fact there are two type