Tomotherapy as a tool in image-guided radiation therapy (IGRT): current clinical experience and outcomes

Modern radiotherapy is characterised by a better target definition through medical imaging accompanied by significantly improved radiation delivery methods, most notably Intensity-Modulate Radiation Therapy (IMRT). However, the treatment can only be as accurate as the positioning of patients for their daily radiotherapy fraction. It is in this context that a number of imaging modalities - ranging from ultrasound to on-board kilovoltage imaging and computed tomography (CT) - have found their way into the treatment room where they verify accurate patient positioning prior to or even during delivery of radiation. Helical tomotherapy (HT) combines IMRT delivery with in-built image guidance using megavoltage CT scanning. This paper discusses the initial experience of different centres with IGRT using HT illustrated by a number of clinical examples from the installation in London in Ontario, Canada, one of the world's first HT sites. We found that HT allows the delivery of highly conformal radiation dose distributions combined with adequate daily image acquisition. An important feature of this unit is its seamless integration, which also includes a customised inverse treatment planning system and a quality assurance module for individual patients.