Dr James Bedford, Radiotherapy Treatment Planning team
The work of the Radiotherapy Treatment Planning team relates to inverse planning and treatment delivery for intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT). The AutoBeam in-house treatment planning system is being used to incorporate the latest advances in inverse planning, including beam orientation optimisation for conformal radiotherapy. For IMRT, the team is working on direct-aperture optimisation, providing effective treatment plans with the simplest and dosimetrically most accurate delivery. This work also includes beam orientation optimisation for IMRT, which is one of the most computationally challenging problems in radiotherapy.
The team is also involved in the development and clinical implementation of VMAT for a variety of clinical sites, including lung, brain and prostate. Research activities have broadened into in vivo portal dosimetry. Methods have been developed for predicting portal images produced by VMAT treatments. The actual measured image at the time of treatment can then be compared with this predicted image, thereby providing a measure of the accuracy of delivered dose. This method of portal imaging is now in routine clinical use.
Helical VMAT for treatment of the central nervous system has also been demonstrated in a research setting. By translating the couch linearly during the delivery, a helical trajectory results, allowing maximum efficiency in treating long target volumes. This type of treatment has been planned and successfully delivered experimentally on the linear accelerator. Investigations are being made into the potential for VMAT with a dynamically rotating couch. This would allow an arbitrary non-coplanar trajectory to be used during VMAT delivery, so as to optimally spare organs-at-risk for head-and-neck and brain cancers.
Other current interests of the team include 4D and adaptive radiotherapy. The team is contributing to studies demonstrating the use of multileaf collimator tracking for moving lung tumours, and has carried out a study investigating the impact of tracking latency on this type of treatment. There is interest in inter-fraction adaptive radiotherapy with VMAT, including the image registration and dose warping that relate to this. Accuracy of dose calculation is important, so this remains part of the work of the team.