152 Appendices Summary With this thesis we developed a practical web-based tool (iScore) and research infrastructure to investigate and validate visual diagnostic methods and staging templates on a large scale within the clinical context of rectal cancer. In Chapter 2 we used iScore to investigate the reproducibility of the structured reporting template published by the European Society of Gastrointestinal and Abdominal Radiology (ESGAR) for the primary MRI staging of rectal cancer in an international study with twenty one radiologists from 12 different countries. In this study we found that several staging items included in the structured reporting template lacked sufficient reproducibility. Main risk variables such as T- and N- stage showed better reproducibility when converted to a dichotomized risk stratification. We showed that diagnostic accuracy is significantly correlated with diagnostic confidence, suggesting that a confidence level should perhaps be included in reporting templates, in particular for staging items with low reproducibility. In Chapter 3 forty-two radiologists completed a stepwise virtual training program, including an online workshop, a case-based training of 70 study cases using iScore, and a virtual expert feedback session. Participants completed a pre- and post-course test to monitor the benefit of the training program. An exploratory comparison of the pre- and post-course test results suggests that dedicated virtual training can improve staging accuracy (between +2 and +17% for individual staging items), diagnostic confidence and interobserver agreement to assess rectal cancer on MRI. These results suggest that virtual training could be a good alternative or addition to in-person training. In Chapter 4 we investigated the trends in staging in the Netherlands. We retrospectively analyzed 712 patients from 8 different teaching hospitals in the Netherlands to assess whether and to what extent new concepts for risk stratification such as EMVI, updated criteria for lymph node staging and subclassification of T stage (high versus low risk based on the depth of extramural invasion) are adopted in routine radiological reporting following recent updates of the Dutch guidelines for colorectal carcinoma. We found a significant increase in the reporting of these items over a seven-year period, along with an increase in the use of structured reporting templates (from ±2% to 30%) and generally improved completeness of reporting. In the second part of this chapter, all MRIs from the study were re-evaluated by an expert radiologist in rectal cancer MRI using the most recent (revised) guideline criteria. Compared to the original staging reports, this led to a change in risk classification in approximately 18% of the study patients, which in retrospect could have led to a change in treatment choice.
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