Technological Developments in Radiotherapy

Uwe Oelfke1

1Institute of Cancer Research, Sutton, Surrey, UK


  Technological innovations have been the driving force behind step changes in radiation therapy practice in recent decades. The introduction of intensity-modulated radiation therapy (IMRT) with high energy photon beams led to fascinating new opportunities conforming doses tightly, even to concave radiation targets encompassing organs-at-risk. The exploitation of this improved dose-shaping potential critically required an accurate knowledge of the patient's anatomy at the time of treatment and led to the development of image guided radiotherapy (IGRT) technologies. IGRT was introduced as a hybrid-technology integrating an x-ray source and a flat-panel imager with state-of-the-art dose delivery equipment. This technology has been available for more than a decade and is increasingly viewed as a means of facilitating therapy adaptation for a substantial proportion of RT patients.¬† However, despite its success, the day-to-day practice of IGRT revealed severe limitations inherent to this approach. First, its poor soft-tissue contrast makes it impossible to discriminate between tumour targets and adjacent healthy tissues for most clinical indications. Second, the detection and monitoring of intra-fraction organ motion is difficult. A solution to these shortcomings is the integration of magnetic resonance imaging (MRI) within modern RT treatment machines. Currently, there are 5 different types of systems either under development or in clinical practice worldwide. A comprehensive overview of their basic features will be presented. Parallel to these developments in radiation therapy with photon beams the technology for the practice of proton radiation therapy advanced considerably. The design of intensity modulated proton therapy (IMPT) concepts with scanning pencil beams allows the design of improved dose patterns reducing integral doses in healthy tissues by a factor of 2-3 when compared to photon RT. Other recent technological innovations¬† that will be discussed are the development of compact single room proton therapy delivery systems and proton specific IGRT solutions.