MRI scans with respiratory immobilisation to contour radiotherapy organs-at-risk using oral contrast of hypo or hyper intense fluids including the patient perspective.

Introduction
Stereotactic ablative body radiotherapy (SABR) has emerged as a promising treatment option for liver cancer. However, its use is challenging due to organ motion and poor visual discrimination between the tumour and surrounding healthy tissues. Whilst magnetic resonance imaging (MRI) and breathing immobilisation techniques have been employed to address these issues, there is a paucity of research exploring the patient experience and potential strategies to improve this. The aim of this PhD project was to explore improvements in visualisation of healthy tissues by reducing motion and improving conspicuity of organs in an acceptable way to patients.

Methods
Four studies were undertaken:
1. A scoping review mapped Non-medicinal Oral Contrasts (NMOC) for upper-abdominal MRI.
2. A single-centre retrospective analysis of 134 consecutive liver SABR patients compared liver motion with and without abdominal compression using planning CT data and multivariable modelling.
3. Semi-structured patient interviews explored experiences of planning and treatment.
4. A proof-of-concept healthy-volunteer study assessed candidate NMOCs on 1.5 T MRI.

Results
1. The review identified 31 distinct NMOCs, with no radiotherapy-specific evaluations, which signified a translational gap.
2. Abdominal compression reduced superior-inferior liver motion by a median of 4.4 mm. However, a large proportion of compressed patients had superior-inferior excursion > 5 mm, and motion ranges overlapped between compressed and uncompressed cohorts. This indicates heterogeneous benefit and supports further personalisation of immobilisation.
3. Ten patient interviews from a single radiotherapy centre revealed three themes of communication, discomfort, and coping and support. Recommendations include clearer pathway explanations and improved timing prompts for breath-hold.
4. Healthy-volunteer MRI suggested that NMOCs, notably yerba mate, produced the expected T1-hyperintense and T2-hypointense appearances, improved duodenal conspicuity by one point on a four-point visual grading scale for contouring confidence on T1-weighted sequences, and were acceptable to participants.

Conclusions
Personalised motion management and pragmatic NMOC protocols warrant prospective evaluation to test effects on contouring confidence, margins, and patient-reported experience.