Imaging in the radiotherapy treatment room

No modern operating theatre would be complete without some imaging equipment. Why should this be different for radiation therapy? The paper by Rybovic et al. in this issue of the Journal aims to provide some data on this in the context of Australia and New Zealand. The term ‘verification imaging’ in the title of the paper indicates that imaging equipment is used in the radiotherapy treatment room to ensure that the radiation beams used for therapy are directed accurately to the correct location in the patient. Verification imaging has been in use for several decades, mostly in the form of portal imaging using radiographic film andmore recently electronic portal imaging (EPI). However, the advent of new imaging methods in the treatment room such as kV imaging, fluoroscopy, ultrasound and cone beam CT has provided us with even more options to use diagnostic tools to improve the targeting of radiotherapy and the term ‘image guided radiation therapy’ (IGRT) is one of the new hot topics in radiation oncology. The concept of image guidance makes sense intuitively and one may wonder why it has taken such a long time for IGRT to hit the spotlight. One would certainly have expected image guidance to be implemented before the introduction of complex, highly conformal radiation dose distributions achievable, for example, with intensity modulated radiation therapy (IMRT). History shows that at least the acronym IMRT was introduced before IGRT. However, in practice, verification imaging has been available for many years and many centres in Australia and New Zealand have intensified their verification imaging protocol once commencing treatment with IMRT. The recent introduction of more advanced imaging tools in the treatment room is welcome in this context and provides us with more options, even if there is still a lack of a widely accepted definition for IGRT and no general agreement as to which technology should be used in what clinical scenario. Research is needed and the paper by Rybovic et al. is timely as it contributes to the discussion by providing an inventory of equipment available in Australasian radiotherapy centres. The article summarizes the availability of verification imaging based on a questionnaire sent to all radiotherapy centres in Australasia. More importantly, it also probes how the technology is used. The high response rate of 87% shows that it was either a well-designed (and brief) survey or that respondents felt it was an important and relevant topic. In the present case most likely both are true and it is worth noting that responses were received from both private and public facilities. Although the actual numbers of equipment are of interest, it is the use of the imaging tools that is of greatest importance. With electronic imaging becoming widely available in the treatment room only in the last few years, there is still a large variety of practices. The manuscript does not probe this in great detail; however, it provides a useful starting point for future studies. The information summarized in the manuscript should be of interest to many ranging from departments considering the purchase of equipment to administrators, educators and clinical trials organizations. Finally, the information will be of interest to patients who would like to find out what is ‘out there’. The results of the present study should be reassuring for patients in Australasia: all radiotherapy centres that filled in the questionnaire have access to some form of imaging in the treatment room and many of them are in the process of upgrading to more advanced technology. Even more reassuring is the fact that more than 90% of responding centres follow a protocol in evaluating the images. This is information less readily available, but probably at least as important as the availability of the equipment itself. It stresses the fact that there is no room for ad hoc introduction of technology – optimum use requires planning, protocols and adherence to best practice. The article only briefly discusses online and offline evaluation of images. This is an interesting debate that will depend on equipment, treatment site, experience, training of staff and clinical judgement. In principle, there is no doubt that online evaluation with the ability to carry out corrective action every day before treatment is preferable as it reduces random