Helical tomotherapy: image-guided and adaptive radiotherapy.

Helical tomotherapy is a treatment device that is designed to deliver intensity-modulated radiation therapy treatments. Helical tomotherapy systems have been used to treat a wide spectrum of anatomical sites. In addition to its unique delivery technique, the capability to obtain megavoltage-based CT (MVCT) images is highly integrated into the system's image guidance. The introduction of MVCT imaging into clinical practice has prompted a range of technical and clinical investigations. The image quality, image dose and use of MVCT images for dose calculation have been investigated. At the same time, routine clinical use of MVCT imaging has provided a wealth of clinical experience. Both technical and clinical experiences with the MVCT system will be reviewed in this chapter.