Statement on the purpose of cross-sectional imaging scans taken for planning radiotherapy

Medical imaging plays a central role in patient care and fulfils a number of separate purposes: diagnosis, staging, monitoring of treatment response and follow-up or surveillance. In all these circumstances, a formal evaluation of the images is required with the production of a report, usually by a clinical radiologist. Images are also acquired in some circumstances specifically to guide treatment. For example, orthopaedic surgeons use x-rays in operating theatres to ensure correct positioning of prostheses and physicians use ultrasound to identify optimal sites for therapeutic aspiration of pleural fluid. In these circumstances, the images may not be optimised to obtain maximum diagnostic information and are obtained for a specific purpose – to guide therapy.

In a similar way, clinical oncologists acquire images, including CT, MRI and on-treatment imaging, specifically for the purpose of planning and delivering radiotherapy. In patients receiving radiotherapy as part of their treatment for cancer, images are used to identify the site for radiotherapy treatment precisely and to plan and ensure the optimal delivery of the treatment. Good practice dictates that these scans should be focused on obtaining enough information for this purpose, while ensuring that the patient receives as little radiation from the scan as possible. Therefore the field covered and scan parameters are not equivalent to those used for a diagnostic study. For this reason these planning scans are not considered as diagnostic examinations and the opinion of a clinical radiologist is not routinely sought. Patients should be clearly informed that the purpose of the scan is for radiotherapy planning and not for diagnostic processes.

If a diagnostic scan is required as part of the patient’s treatment pathway then the clinician will refer the patient to a clinical radiologist for appropriate imaging and interpretation.

Radiotherapy planning images must be stored in line with RCR guidance and if they are stored on the hospital Picture Archiving and Communications System (PACS) they should be clearly labelled as planning scans.

When a clinical radiologist does interpret a diagnostic scan, then it is good practice to use all available information to provide a comprehensive report. This should include all available previous diagnostic imaging and, if available, radiotherapy planning scans may be reviewed.

Revised: December 2025