Scanner Specific Uncertainty of Quantitative MRI: Assessing Consistency for Clinical Implementation

In the past, many of the steps involved in the radiotherapy workflow have been heavily reliant on X-ray based anatomical imaging. Incorporating additional imaging modalities in this workflow has been shown to be promising. This includes aiding in generating and modifying a patient’s treatment regimen and also helping determine a patient’s response to treatment. Magnetic resonance imaging (MRI) is one of these modalities which can provide both enhanced soft-tissue anatomical images and supplementary information relating to changes in tissue physiology (which occurs at a faster rate than anatomical changes). Quantitative imaging biomarkers (QIBs), derived from quantitative MRI (qMRI) techniques, are measurable quantities that relate to tissue physiology (e.g., diffusion or perfusion) and thus are of particular interest in radiotherapy. Given these capabilities, there is potential for MRI to replace X-ray imaging in several steps of the radiotherapy workflow. However, until recent years there were no qMRI quality assurance (QA) guidelines available for departments to assess the technical performance of QIBs on their MRI scanners (e.g., accuracy and repeatability). This resulted in limited work being completed that investigates QIB performance metrics; ultimately limiting the widespread clinical utilisation of qMRI techniques. These investigations are essential to determine if the quantitative values derived can be accurately used to guide radiotherapy workflow decisions.