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

Medical imaging fulfils several purposes including diagnosis, staging, monitoring of treatment response and follow-up. In all these circumstances, formal evaluation of the images is required by IR(ME)R with the production of a report, usually by a clinical radiologist. In some circumstances images are acquired 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.

In a similar way, radiotherapy teams acquire localisation images, including CT, MRI and on-treatment imaging, specifically to identify the site for radiotherapy 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. Planning scans are usually acquired shortly after other diagnostic imaging which has covered the same sites and been formally reported. Consequently, the opinion of a clinical radiologist is not routinely sought for planning scans. Patients should be clearly informed that the purpose of the scan is for radiotherapy planning and not for diagnosis.

The oncologist should review all images in the planning scan dataset to look for other significant or unexpected findings, for example new visible tumour, metastases or other obvious pathology. This review should be documented in the radiotherapy planning note.  A review is particularly important when there has been no prior cross-sectional imaging of that part of the body in the recent past. Concern on the part of the oncologist regarding a possible previously undetected abnormality on the radiotherapy planning scan should prompt review of the planning scan by a clinical radiologist, documentation of that review by the oncologist or radiologist, and appropriate follow-up action as required. However, clinical oncologists are not responsible for ensuring that all anatomical abnormalities on a radiotherapy planning scan are detected. 

Radiotherapy planning images must be stored in line with RCR guidance. If they are stored on the hospital Picture Archiving and Communications System (PACS) they should be clearly labelled as planning scans. It is best practice that all imaging, including radiotherapy planning scans, are available to a reporting radiologist in a single archive when a patient’s imaging is accessed. 

Published: January 2014
Reviewed: February 2017
Revised: March 2025