Invited Lecture 3.3

Abstract

Modern radiotherapy is unthinkable without imaging. Imaging provides the information required for target definition and treatment planning and it is required to verify the patient position at time of treatment delivery. Imaging in radiotherapy must be three dimensional and take motion into consideration where needed, such as in abdominal and thoracic cancers. All this results in imaging procedures that are often different from the ones used in diagnostic radiology and often do not take radiological protection into account in the same way radiology does. Challenges specific to imaging in radiotherapy are i) the requirement to image larger volumes than in radiology to account for potential beam direction in therapy, ii) the explicit inclusion of breathing motion, iii) the lack of optimisation tools provided by manufacturers, and iv) the fact that verification imaging is often required daily for 20 or more treatment delivery fractions. In addition to this is the lack of specific training for operators and a prevalent feeling that radiological protection is of secondary importance in clinical scenarios where tumours receive doses 1000s of time larger than the ones used in imaging. However, these perceptions change as imaging affects typically a much larger volume than the treatment and late effects such as cardiac toxicity and secondary cancers are affecting patients who survive longer due to the advances of modern cancer treatment. The presentation will introduce the problem, discuss the approach of a recent task group of ICRP looking into the topic and consider some potential improvements that can help to optimise use of imaging in radiotherapy.