Task Group 116
Radiological Protection Aspects of Imaging in Radiotherapy

A Task Group under Committee 3

Modern radiotherapy equipment delivers radiation beams from multiple directions conformed to the shape of the target tumour to achieve a planned radiation distribution. Imaging is crucial for successful planning and delivery of this dynamic image guided radiation therapy, to provide additional accuracy in localisation of tumour volumes at the time of treatment. Imaging may be associated with each of the therapy fractions in order to adjust for tumour volumes and any movement in other organs. This is accomplished using either kV or MV orthogonal x-rays or cone beam computed tomography imaging systems integrated into linear accelerators, and enables radiation field margins surrounding the tumour to be reduced. However, if imaging is used frequently with little optimisation, doses to organs and tissues outside the planning target volume can reach tens of mGy per radiotherapy fraction and the imaging dose delivered to the tumour over the course of treatment is no longer insignificant. The use of radiography and fluoroscopy in planning brachytherapy treatment will also be considered. At the present time, practices vary between centres in imaging modalities used, the frequency of imaging, and the level of optimisation undertaken, so more guidance is needed.

This task group will provide guidance on radiological protection aspects in the use of imaging (e.g., cone beam CT, fluoroscopy) in radiotherapy. Advice will relate to optimisation of protocols for exposures carried out during the planning stages, and the frequency and level of optimisation for imaging performed for treatment guidance. The report will consider the trade-off between therapeutic advantages and additional radiation doses from imaging. The report will also examine the need for assessment of organ and tissue doses relating to imaging for communication to radiation oncologists and inclusion in the planning process.

Colin Martin (Chair), University of Glasgow, UNITED KINGDOM
William Small (Vice-Chair), USA
Daniel Berger (Member), International Atomic Energy Agency, AUSTRIA
Aurelie Isambert (Member), IRSN, France
Stine Korreman (Member), Denmark
Tomas Kron (Member), Peter MacCallum Cancer Centre, Australia
Choonsik Lee (Member), National Cancer Institute, USA
Thomas Merchant (Member), USA
Ngie Min Ung (Member), University of Malaya, Malaysia
Jenia Vassileva (Member), International Atomic Energy Agency, Austria
Tim Wood (Member), Hull University Teaching Hospitals, UNITED KINGDOM
Abdullah Abuhaimed (Member (Mentee)), King Abdulaziz City for Science and Technology, SAUDI ARABIA
Abdel-Hai Benali (Member (Mentee)), University of El Oued, ALGERIA
Mario Djukelic (Member (Mentee)), Sir Charles Gairdner Hospital, AUSTRALIA
Sebastien Gros (Member (Mentee)), Loyola University Medical Center, USA
Maria Cristina Plazas (Member (Mentee)), Universidad Nacional de Colombia, COLOMBIA
Hossam Ragab (Member (Mentee)), Senior Medical Physicist at Baheya foundation for early detection & treatment of breast cancer., EGYPT
Yiannis Roussakis (Member (Mentee)), German Oncology Center, CYPRUS