New software helps radiotherapy track moving tumours

Date:
07 December 2014

The software, developed by researchers at The Institute of Cancer Research, London, and The Royal Marsden NHS Foundation Trust, tracks motion to a high degree of accuracy, matching tumour movement to within one hundredth of a second.

The software could improve high-tech forms of radiotherapy that can shape radiation beams to the tumour, increasing the effectiveness of treatment and reducing radiation exposure to healthy tissues.

Tumours in organs such as the lungs, liver or prostate are susceptible to motion during radiotherapy. Some systems rely on larger than necessary radiation beams to compensate for movement, but this risks damaging healthy tissue at the same time.

Radiotherapy equipment using technology called multileaf collimators (MLC) can alter the radiation beam to match the shape of a tumour, reducing unnecessary exposure to surrounding healthy tissue, but tumour motion may still affect the accuracy of treatment delivery.

The research, published in the journal Medical Physics, was funded by the NIHR Biomedical Research Centre at The Royal Marsden and The Institute of Cancer Research (ICR), and Cancer Research UK. It received technical support and access to a research version of the Agility MLC control software from Elekta AB.

Professor Uwe Oelfke and his team in the Joint Department of Physics at the ICR and The Royal Marsden developed new software to take advantage of specific features of the Elekta Agility MLC, in order to enable real-time tumour tracking.

They tested their software using a model which mimicked the motion of regular breathing, and recorded how accurately their tracking system could follow this motion.

They found that their software helped the MLC to follow the movement of the tumour with very low latency during the delivery of radiotherapy. For typical tumour motion, the radiation beam was able to accurately track the tumour’s position with a mean geometric error of under a millimetre.

The new software could reduce the need for motion-related treatment margins, and could be adapted for existing radiotherapy systems equipped with Agility MLC.

Professor Oelfke, Head of the Joint Department of Physics at the ICR and The Royal Marsden, said: “Modern radiotherapy systems can precisely shape radiotherapy beams to the shape of tumours, but there remains a problem targeting diseases like lung and liver cancer where normal breathing can cause tumours to move significantly over time. Being able to track that movement accurately is extremely important to improve radiotherapy.

“The software we have developed in partnership with Elekta allows fast and effective tumour tracking, accurate to within one millimetre. More research is needed to study its use in patients but our findings could help bring this technology to the clinic within the next five years."