89 Comparison of MRI response evaluation methods in rectal cancer: a multicentre and multireader validation study 6 MRI protocols and quality assessment MRI examinations were performed according to the local protocols of the participating centers at the time of inclusion. From the full available protocols, we selected a basic set of sequences (representing the main sequences required for rectal cancer restaging according to current guidelines [15]) consisting of 2D-T2W sequences in sagittal, obliqueaxial (perpendicular to the tumor axis), and oblique-coronal (parallel to the tumor axis) planes, and an oblique-axial DWI sequence with corresponding apparent diffusion coefficient (ADC) map. T2W slice thickness ranged between 3 and 5 mm and in-plane resolution ranged between 0.35 x 0.35 and 0.94 x 0.94 mm. The DWI sequence included at least one high b-value ranging between b600 and 1200 s/mm2. MR image quality was graded by one of the authors (N.E.K., who did not participate in the further study readings) using a 6-point scoring system developed for the purpose of this study. This scoring was based on current guidelines, other published recommendations on image acquisition, and on previously published scoring systems to grade DWI image quality [15,16,17,18], as detailed below: • Transverse sequence angulation[15]: 0 = not perpendicular to longitudinal tumor axis o 1 = perpendicular to longitudinal tumor axis • T2W slice thickness [15]: 0 = > 3 mm o 1 = ≤ 3 mm • T2W in-plane resolution [16]: 0 = > 0.6 x 0.6 mm o 1 = ≤ 0.6 x 0.6 mm • DWI high b-value[15]: 0 = < 800 s/mm2 o 1 = ≥ 800 s/mm2 • DWI signal to noise ratio [18]: 0 = Poor – intermediate o 1 = Good – excellent • DWI artefacts [17]: 0 = moderate-severe, hampering interpretation o 1 = no-minimal, not hampering interpretation Scans with a score of ≥ 4/6 were classified as good quality; scans with a score of < 4/6 as below average quality. Image evaluation An invitation to participate in the study was sent out to the members of the European Society of Gastrointestinal and Abdominal Radiology (ESGAR) (in particular members with an interest in rectal imaging). This rendered an international group of twenty-two radiologists, including 5 rectal MRI experts (each with ≥ 10 years of dedicated experience in rectal MRI ) and 17 abdominal radiologists (or general radiologists with a specific interest in abdominal imaging). Image evaluation was performed using an in-house developed web-based viewing platform (iScore) with embedded electronic case report forms (eCRF) that were designed for the purpose of this study by one of the authors
RkJQdWJsaXNoZXIy MjY0ODMw