Image-Guided Radiation Therapy: Quality and Performance in Cancer Intervention
Image guidance has become a central element of radiation therapy. While the use of images begins at the planning phase, recent technological developments allow high-performance imaging at the treatment unit on a fraction-by-fraction basis, and thereby, allow errors in the targeting of the radiation to be detected and corrected. This development enables a reduction in the volume of normal tissues that must be exposed to therapeutic levels of radiation to assure target coverage. The tightening of the planning target volume (PTV) margins also permits dose escalation for clinical sites where local control is lacking. In addition to enabling novel treatments, IGRT technologies are also seen to increase the quality with which radiation therapy is executed. While the development of the imaging systems is a critical component of IGRT, there have also needed to be developments in the lexicon of radiation therapy prescription, image registration tools, and robotic technologies for patient repositioning to allow the IGRT paradigm to operate within the existing operational models of fractionated radiation therapy. Overall, the technological developments over the past 10 years have transformed radiation therapy into a leading model of image guidance in cancer intervention embarking on the exciting field of adaptive therapy, wherein, geometric and biological changes occurring during the course of therapy are accommodated through replanning.
KeywordsPlanning Target Volume Stereotactic Body Radiation Image Guidance Normal Tissue Complication Probability Treatment Beam
The author would like to acknowledge individuals that have collaborated on some of the work reported in this chapter. These include Dr. Mike Milosevic, Mr. James Stewart, Dr. Kristy Brock, and Dr. Tim Craig. Drs. G. Fallone, J. Lagendijk, and J. Dempsey are thanked for providing some of the figures included in this paper. IMRIS, Inc. is acknowledged for providing the rendering of the MRgRT solution being developed for the Princess Margaret Hospital.
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