Image guided radiotherapy: Current status of soft tissue imaging

Image guided radiotherapy has evolved from two dimensional (2D) megavoltage imaging, which allowed verification with respect to bony anatomy, to three dimensional (3D) kilovoltage imaging which enables soft tissue structures to be used for verification. Alongside the technological developments, treatment delivery techniques have become more sophisticated and the potential to adapt treatment delivery to changes in tumour and/or organs at risk is increasing. This review explores the current status of soft tissue imaging techniques in conjunction with the potential clinical impact. The common tumour sites where the new treatment techniques are being investigated are identified and it is seen that to support the implementation of these techniques, investment in capital equipment and staff training is essential.