Accounting for tumour deformation in real time

Tumours of thorax, abdomen and prostate undergo continuous motion including translation, rotation and deformation. State-of-the-art treatment techniques can correct only for tumour translation and rotation in real time. Studies show deformation for lung, liver and pancreatic tumours of up to 5mm and differential motion (deformation of multi-tumour system) between primary lung or prostate tumours and involved lymph nodes of more than 15mm. In current practice, the problem of deformation is still addressed by extending the treatment margin to ensure tumour coverage, which increases normal tissue toxicity and limits local disease control.

The collaborations have developed a radiotherapy system capable of accounting for tumour translational motion in real time using dynamic multileaf collimator (DMLC). We are working on adding the capability of accounting for tumour deformation to the system, including real-time acquisition of deformation and real-time adaptation of DMLC fields. Currently, the focus is to develop the DMLC tracking system provided that the deformation has been acquired. The system will be validated and characterised with a series of phantom experiments.

We have implemented the work flow of deformable image registration of acquired images, communication between the deformation data processing and the DMLC tracking system and adapting DMLC fields using the deformation data.