The introduction of dedicated planning MR-CT fusion for radical radiotherapy of prostate cancer

Purpose Advances in radiotherapy planning and delivery have made target definition increasingly important. While CT images are required for plan calculation, MR fusion is increasingly used to more accurately define tumour and normal tissue. There is often significant variation seen between diagnostic and therapeutic imaging; hence, MR carried out in the treatment position is desirable. Materials and methods A multidisciplinary team of diagnostic and therapeutic radiographers, treatment planners, medical physicists and clinicians was convened. Planning MR was integrated into the radiotherapy pathway and carried out in the days immediately following CT simulation. All men underwent identical preparation (administration of a micro-enema and drinking 300 mL of water thirty minutes prior to imaging/treatment). Patients were set up in the treatment position using MR-compatible radiotherapy immobilisation. T2SE axial and sagittal images were acquired (Siemens Aera 1.5T E11, incorporating RT software platforms/LAP Laser Bridge/Civco RT Indexing Flat couch top/coil bridges), imported into the Eclipse planning system (V13.6, Varian), and fused to the planning CT for volume delineation. Results The service opened in mid-September 2017. 26 patients were scanned to the end of November 2017. All patients tolerated preparation and imaging without difficulty. Conclusion This service has been successfully introduced and will shortly expand to include other sites (rectum, lung, head and neck, complex palliative). A study is planned to assess the impact of the addition of MR on target delineation. Additional considerations include the need for dedicated radiology input and the potential role of collaboration with industry with a view to stand-alone MR simulation.