Radiotherapy is usually planned and delivered using CT scans. However, MRI‑guided radiotherapy (MRIgRT), such as that delivered on the MR‑Linac, works differently because MRI shows soft tissues and tumours more clearly. To make sure this newer approach is safe, accurate and effective, we need to study several important areas:

1. Understanding how consistently clinicians can identify the tumour on MR‑Linac images.
   This helps us know whether different doctors (or the same doctor at different times) see the tumour in the same way.
2. Building a library of example scans (“atlases”) for different tumour types.
   These help clinicians interpret images and support the development of automated tools that can assist in planning and adapting treatment.
3. Developing reliable methods to match MR‑Linac images with the CT or MRI scans used in the original treatment plan.
   Accurate matching is essential for safe daily treatment adjustments.
4. Figuring out the best safety margins around tumours for radiotherapy planning.
   These margins account for natural movement and size changes of the tumour during treatment.
5. Identifying the best margins to guide daily treatment setup on the MR‑Linac.
   This ensures each treatment is delivered accurately even when the tumour moves or changes.
6. Creating a library of treatment plans for each type of tumour.
   These ready‑made plans help speed up the adaptive radiotherapy process when changes need to be made on the day.
7. Studying how specific features of the MR‑Linac affect treatment delivery.
   This helps us optimise how we use the technology to provide the best possible care.
   

The PRIMER study will enrol patients and volunteers from many different sites of disease to build a comprehensive library of images which can be optimised by the study team. These superior images can then be used in the clinical setting in order to be of benefit to future patients.

Participants will be required to undertake MR scans on the MR-Linac at 1-5 timepoints throughout their treatment. These scans should take no longer than 1 hour.