ESTRO 2024 - Abstract Book

S5450

RTT - Patient care, preparation, immobilisation and IGRT verification protocols

ESTRO 2024

Orally administered endoluminal contrast agents are routinely used to improve the conspicuity between the gastrointestinal tract and other soft tissues such as the biliary tract in diagnostic MRI procedures (1, 2). While medicinal products such as manganese chloride, gadopentate dimeglumine, or mannitol can be used, they are associated with numerous side effects (1-4). However, drinks such as fruit juice, milk, tea, or water may also be used as non-medicinal oral contrast (NMOC) agents with few or no side-effects, potentially leading to an improved patient experience (5-8). To the authors’ knowledge, using NMOCs to aid MRI radiotherapy contouring and reducing treatment planning uncertainties has not been investigated. This study aimed to provide proof-of-concept data to validate the literature and support further research into the use of NMOCs in MR-guided abdominal radiotherapy.

Material/Methods:

The study comprised of two parts; 1: a systematic scoping review of the literature conducted to identify potential NMOCs that might be suitable for MR-guided radiotherapy; and 2: an in vitro analysis of the inherent relaxometry properties of potential NMOCs.

1. Systematic scoping review:

A systematic scoping review based on Arksey and O’Malley’s framework (9) was conducted following a pre-defined and published protocol. Empirical studies were searched from inception to 01/05/2023 using MEDLINE (Ovid), EMBASE, CINAHL (EBSCOhost), CAB Abstracts, Google Scholar, and Proquest Dissertations & Theses databases. Studies involving animals or not published in English were excluded. Duplicates were removed using Bramer’s method (10). Title and abstract screening was conducted by the first author, with a minimum proportion of 10% of results being checked by a second reviewer utilising Covidence systematic review software (11). Disagreements were countered with consensus. An a priori charting framework chart was developed intended for use in the first 10% of the included studies and was modified until the codes were coherent and explicit. Cohen’s kappa statistic was used to test the level of agreement. Data was charted and aggregated to provide an account of the utilisation of NMOC use in upper-abdominal MRI. Characteristics of NMOC reported in the literature were summarised, including luminal signal appearance, anatomical location with regards to the timing of administration, quantitative T1 and T2 measures to aid comparison, and impact on participant experience. An exploratory proof-of-concept evaluation of potential NMOCs was conducted using a 1.5T Philips Ingenia MRI scanner with a dStream HeadNeckSpine coil. NMOCs included those identified in the systematic scoping review and other novel drinks, chosen because of their high concentration of transition metal ions. NMOCs were left in the scanner room overnight to reduce the impact of temperature change on relaxation times. Using MATLAB (12), T1 and T2 relaxometry was performed using an IR SE sequence (TR: 5000ms; TI: 20ms, 30ms, 50ms, 75ms, 100ms, 150ms, 200ms, 350ms, 600ms, 900ms, 2500ms), and a multi-echo TSE sequence (TR: 5000ms; FA: 90°; TE: 10ms, 20ms, 30ms, 40ms, 50ms, 60ms, 70ms, 80ms, 90ms); ETL: 9), respectively. Quantified T1 and T2 values of NMOCs were analysed to identify potential candidate NMOCs. 2. In vitro evaluation of potential NMOCs:

Results: