Comparison of conformal arc radiotherapy and Volumetric Modulated Arc Therapy (VMAT) for the treatment of small lesions affected by motion

Arc radiotherapy has become a popular radiation therapy treatment modality as it delivers high radiation doses quickly using a dynamic rotational treatment where the beam is on continuously while the radiation unit rotates around the patient. This is particularly interesting for stereotactic ablative body radiation therapy (SABR) where very high biological doses are given in few fractions. The most recent delivery techniques combine dynamic arcs with variations in dose rate and continuous modulations of radiation fluence (VMAT) which allows to create dose distributions which can tightly conform to the tumour. However, this additional modulation increases treatment time and more importantly risks that variations in shielding are in synch with tumour motion, effectively providing unwanted shielding for the target (“interplay effect”).

The project seeks to study this interplay effect systematically as a function of motion, lesion size, number of fractions, surrounding inhomogeneities (eg lung) and intensity modulation pattern. This will be compared with conventional arcs that always treat the whole tumour from every beam direction. The project will combine dose calculations with measurements in phantoms to provide radiation oncologists with guidance as to what treatment approach would be most beneficial for a particular patient.

This project will be supervised by Professor Tomas Kron.

The Department of Physical Sciences houses a dedicated group of researchers harnessing the physical sciences to optimise the delivery of cancer treatments, developing techniques that increase tumour exposure to effective therapy and simultaneously reduce the exposure of normal tissues.

Research Interests:
• Improving the accuracy of radiation therapy in planning and delivery and ensuring equipment complies with prescribed dosages.
• Conducting compliance testing, refining and improving image quality in diagnostic imaging equipment such as planar X-ray, computed tomography (CT) scanners and fluoroscopy.
• Developing methods to utilise modern imaging techniques to improve accuracy of radiation delivery.
• Developing tools to support clinical trials to assess the utility of modern radiation oncology technology.
• Improving the surveying and monitoring of radiation protection and electromedical equipment.

A strength of the research group is the involvement of medical physicists and biomedical engineers to turn ideas into clinical practice. This has led to many successful innovations, such as a computer controlled rotating turntable for whole body electron treatments, a novel monitor unit calculation program, credentialling tools for clinical trials and the development of an infra-red motion detection system to monitor movement of paediatric patients.