ESTRO 2020 Abstract book

S1131 ESTRO 2020

Results

CBCT-CT (mm)

MR-CBCT (mm)

MR-CBCT (mm) (post training intervention)

1.4 (±0.8)

1.5 (±0.7) 1.5 (±0.4) 0.6 (±0.4)

Vertical

0.9 (±0.3)

Longitudinal 1.2

1.2 (±0.4)

(±0.7) 0.4 (±0.1)

0.5 (±0.1)

Lateral

Table 1. Mean (± standard deviation) of the inter-observer error across modalities. Results showed similar inter-user variability across the imaging modalities, although variation reduced following the training intervention. Conclusion Therapeutic radiographers require minimal additional training to use MRI as a reference data set for online soft- tissue image matching for prostate patients despite having no prior experience of MRI. This suggests site-specific CBCT analysis skills are transferrable across different reference imaging modalities, and prepares for other tumour sites using an MR-only pathway without fiducial markers. References (1) Gunnlaugsson, A., et al., 2019. Target definition in RT of prostate cancer using magnetic resonance imaging only workflow. Physics and Imaging in Rad Onc , 9 (2) Ariyaratne, H., et al., 2017. Image-guided RT for prostate cancer in the United Kingdom: a national survey. The British journal of radiology , 90 (1070) PO-1936 Establishing the acceptability of a gold standard in IGRT assessment for radiation therapists E. Barker 1 , M. Leslie-Dakers 1 , S. Higgins 1 , T. Barnes 1 , S. McGrail 1 , A. Webster 2 , S. Goldsworthy 1 1 Taunton & Somerset NHS Foundation Trust, Radiotherapy- The Beacon Centre, Taunton, United Kingdom ; 2 National Radiotherapy Trials QA Group, Mount Vernon Cancer Centre, Middlesex, United Kingdom Purpose or Objective Comprehensive training of radiation therapists (RTTs) is essential in delivering accurate radiotherapy; however, there is a lack of a consensus on how to train and assess competence in image guided radiotherapy (IGRT). Inspired by the adaptive training developed by the RAIDER trial (CRUK/14/016) team and the National Radiotherapy Trials Quality Assurance (RTTQA) group, an IGRT assessment and training package has been developed. The main aim was to determine whether a ‘gold standard’ method of IGRT training can be achieved that provides an efficient, robust and objective tool for RTTs. Material and Methods Site specific assessment packages (SSAPs) were produced for 6 anatomical sites within Microsoft® Excel TM . ‘Gold standard’ interpretation of individual images was achieved through a consensus consisting of 5 RTTs specialising in IGRT. Visual Basic for Applications scripting was utilised to provide a semi-automated assessment method. SSAPs were developed to assess individuals’ abilities to interpret and action verification images in respect to local protocol. The system was validated by two independent RTTs specialising in IGRT. Efficiency was measured in regard to time taken to complete each SSAP for both assessor and trainee and a 16-question satisfaction questionnaire was deployed (Table 1.).

Conclusion Data analysis suggests the virtual reality training tool can enhance learning, and improve RT knowledge for the MDT. This in turn, improves support provided to patients undergoing RT. PO-1935 MR-only prostate radiotherapy – how transferable are CT based image matching skills? R. Brooks 1 , H.M. McCallum 1,2 , K. Pilling 1 , R.A. Pearson 1,2 , J.J. Wyatt 1,2 1 Newcastle upon Tyne Hospitals, Northern Centre for Cancer Care, Newcastle upon Tyne, United Kingdom ; 2 Northern Institute of Cancer Research, Newcastle University, Newcastle upon Tyne, United Kingdom Purpose or Objective MRI provides superior soft tissue visualisation in comparison to CT, and has long been used alongside CT in radiotherapy planning. However, MR-CT fusion may introduce registration inaccuracies. MR-only planning can eliminate this inaccuracy resulting in greater geometrical accuracy, one less patient visit and smaller treatment volumes (1), potentially reducing side effects. At our centre we have implemented an MR-only radiotherapy pathway for prostate cancer patients using MRI for target delineation, generation of synthetic CT to enable dose calculation and online verification. Research to date has used online fiducial matching with an MR-only pathway, yet in the UK, 66% of centres use cone beam computed tomography (CBCT) soft-tissue matching for verification purposes (2). To the best of our knowledge, we are the first to report on online soft-tissue matching to an MRI reference image. This piece of work assesses the transferability of radiographer skills and associated training needs for MR-CBCT prostate soft-tissue matching. Material and Methods Twenty-three radiographers with 3 months – 5 years’ experience of online daily CT-CBCT soft tissue matching prostate cancer patients participated in the repeated measures study between February and July 2019. Radiographers with dedicated MR training were excluded. Each participant completed 10 CT-CBCT prostate soft tissue matches offline as a baseline for inter-user variability. To assess image matching skills on an MRI reference data set, each participant completed 10 MR- CBCT prostate soft-tissue matches. Training in MRI anatomy and image analysis was delivered by a clinical specialist therapeutic radiographer with MR-CBCT experience and the same 10 MR-CBCT prostate soft tissue matching exercise was repeated. Inter-observer error was calculated as the standard deviation of the matches across all observers per patient.