IMRT: delivery techniques and quality assurance.

Intensity modulated radiotherapy (IMRT) is a major development in the delivery of radiation therapy that has the potential to improve patient outcome by reducing morbidity or increasing local tumour control. Delivery techniques include those based on purpose built devices and treatment machines together with those utilizing the capabilities of computer controlled multileaf collimators which are more widely available. The complexity of IMRT techniques demands a high level of quality control both in the operation of the equipment and in the delivery of treatment to individual patients. The purpose of this paper is therefore to review the techniques available, concentrating on the use of multileaf collimators, and to consider the necessary quality control requirements for clinical application. It demonstrates that the technology is mature and sufficiently well understood so that IMRT can be safely implemented in the general clinical environment rather than being limited to application in the research environment.