MRI for Crohn's disease From quantification to automation

MRI has become an important technique for diagnosis and monitoring of Crohn’s disease. As there is increasing reliance on MRI to guide therapeutic decisions, accurate and reproducible tools for grading of disease activity are imperative. In this thesis, we show that MRI and CT can both be used to accurately grade Crohn’s disease activity, although MRI has the added benefit of not using ionizing radiation. We compare several available MRI scores, which are found to be similar in accuracy, reproducibility and diagnostic performance. However, considerable variability between radiologists remains an issue. To overcome this problem, we have developed and validated a semiautomatic MRI score, which increases the agreement between radiologists by automating parts of the radiologic evaluation. This includes newly developed MRI features, such as bowel wall volume and a dynamic contrast enhancement feature. In addition, we compare diffusion-weighted imaging (DWI) to contrast-enhanced MRI and show that DWI can be an acceptable alternative in patients with contraindications to intravenous contrast. Another technique called motility imaging is investigated and shows promise as a new biomarker for disease activity. Finally, we show that radiologists retain long-term performance, after being trained to grade Crohn’s disease on MRI.