A survey of image-guided radiation therapy practices around the globe

Improvements in conforming radiation fields to tumours in radiotherapy have increased the potential for successful treatment of cancer. However, achieving successful delivery requires the patient to be positioned on the treatment couch accurately. X-ray imaging using on-board imaging systems incorporated into linacs is performed to verify patient positioning, frequently at every treatment fraction. The x-ray imaging exposes normal tissues surrounding the tumour and carries a risk of inducing second cancers. The reductions in high-dose treatment margins achieved with image-guided radiation therapy (IGRT) must be balanced against harm from additional imaging doses. ICRP Task Group 116 has been set up to prepare guidance on radiological protection aspects of IGRT. The task group has undertaken a survey of imaging practices in radiotherapy in nine countries across the world. This has shown that kilovoltage (kV) cone beam computed tomography (CT) is used widely, and the level of use increases with the Human Development Index for the country. The survey has shown that there is limited awareness of the doses from imaging in radiotherapy centres, a lack of expertise in diagnostic imaging, and limited recording of patient doses. This has informed the task group in the development of guidance.