Imaging Cherenkov emissions for in vivo verification in radiotherapy
Modern radiotherapy techniques rely on complex radiation fields which rapidly change in space and time. Being able to visualise the radiation dose entering and exiting the patient will enable a new level of in-vivo verification. The impact of this work will be to give greater confidence that the planned dose is actually being delivered, enabling real-time detection, and ultimately correction, of discrepancies between the planned and delivered dose. We have shown that a treatment beam from a linear accelerator generates visible Cherenkov light which can be imaged with a standard consumer digital SLR camera. Other groups have generated in vivo movies showing the Cherenkov light emitted as treatment progresses. We propose to build on this previous work and demonstrate the application of Cherenkov imaging for real-time in-vivo verification. Cherenkov imaging allows the radiation field to be imaged in real time and registered to anatomical landmarks. We believe it will be of particular relevance in treatments including electron boost to breast cancer, patient movement correction in paediatric cancer and, perhaps most significantly, imaging to show the radiation field during radiotherapy of lung cancer. This will allow models of lung tumour movement to be constrained to provide more robust compensation for tumour movement. This project will suit a student with an interest in clinical physics. It will involve experimental work and analysis, including registration of Cherenkov imaging to surface anatomy and determining the effect of movement on the treatment plan. The student must have excellent practical, mathematical, and computational skills.
Aims and Objectives:
(1) Imaging and characterising the accuracy and precision of Cherenkov emissions to determine entrance and exit fields on a static tissue-equivalent phantom. Monte Carlo simulations will be carried out to support these results.
(2) Imaging and characterising Cherenkov emissions for real-time imaging of entrance and exit fields on a dynamic tissue-equivalent phantom with realistic movement.
(3) Review of promising clinical applications, informed by results from (1) and (2) and discussion with clinical colleagues. Request for ethical approval for patient studies.
(4) Clinical studies. Specific applications depend on (3) but likely to be selected from movement compensation in lung cancer, patient movement correction in paediatric cancer, electron boost in breast cancer and field characterisation for extended breath-hold breast radiotherapy
(5) Analysis. The power of Cherenkov imaging will be realised when the entrance and exit fields are registered to the (moving) anatomy and to the treatment plan.