The impact of a radiologist‐led workshop on MRItarget volume delineation for radiotherapy

Magnetic resonance imaging (MRI) is increasingly used for target volume delineation in radiotherapy due to its superior soft tissue visualisation compared to computed tomography (CT). The aim of this study was to assess the impact of a radiologist‐led workshop on inter‐observer variability in volume delineation on MRI. Data from three separate studies evaluating the impact of MRIin lung, breast and cervix were collated. At pre‐workshop evaluation, observers involved in each clinical site were instructed to delineate specified volumes. Radiologists specialising in each cancer site conducted an interactive workshop on interpretation of images and anatomy for each clinical site. At post‐workshop evaluation, observers repeated delineation a minimum of 2 weeks after the workshops. Inter‐observer variability was evaluated using dice similarity coefficient (DSC) and volume similarity (VOLSIM) index comparing reference and observer volumes. Post‐workshop primary gross tumour volumes (GTV) were smaller than pre‐workshop volumes for lung with a mean percentage reduction of 10.4%. Breast clinical target volumes (CTV) were similar but seroma volumes were smaller post‐workshop on both supine (65% reduction) and prone MRI(73% reduction). Based on DSCscores, improvement in inter‐observer variability was seen for the seroma cavity volume on prone MRIwith a reduction in DSCscore range from 0.4–0.8 to 0.7–0.9. Breast CTVdemonstrated good inter‐observer variability scores (mean DSC0.9) for both pre‐ and post‐workshop. Post‐workshop observer delineated cervix GTVwas smaller than pre‐workshop by 26.9%. A radiologist‐led workshop did not significantly reduce inter‐observer variability in volume delineation for the three clinical sites. However, some improvement was noted in delineation of breast CTV, seroma volumes and cervix GTV. Magnetic resonance imaging (MRI) is increasingly being adopted into radiotherapy planning and treatment. Appropriate training and education needs should be considered to allow for this change in practice, particularly for sites currently not routinely using MRI. A radiologist led workshop can potentially be used as a method to minimise inter‐observer variability. However, further research is needed to design the most appropriate education or training intervention to support the use of MRIin radiotherapy.