MR imaging of the brain in large cohort studies: feasibility report of the population- and patient-based BiDirect study.

objectivesTo describe the implementation and protocol of cerebral magnetic resonance imaging (MRI) in the longitudinal BiDirect study and to report rates of study participation as well as management of incidental findings.

methodsData came from the BiDirect study that investigates the relationship between depression and arteriosclerosis and comprises 2258 participants in three cohorts: 999 patients with depression, 347 patients with manifest cardiovascular disease (CVD) and 912 population-based controls. The study program includes MRI of the brain. Reasons for non-participation were systematically collected. Incidental findings were categorized and disclosed according to clinical relevance.

resultsAt baseline 2176 participants were offered MRI, of whom 1453 (67 %) completed it. Reasons for non-participation differed according to cohort, age and gender with controls showing the highest participation rate of 79 %. Patient cohorts had higher refusal rates and CVD patients a high prevalence of contraindications. In the first follow-up examination 69 % of participating subjects completed MRI. Incidental findings were disclosed to 246 participants (17 %). The majority of incidental findings were extensive white matter hyperintensities requiring further diagnostic work-up.

conclusionsKnowledge about subjects and sensible definition of incidental findings are crucial for large-scale imaging projects. Our data offer practical and concrete information for the design of future studies. KEY POINTS: • Willingness to participate in MRI is generally high, also in follow-up examinations. • Rates of refusal and prevalence of contraindications differ according to subject characteristics. • Extensive white matter hyperintensities considerably increase the disclosure rates of incidental findings. • MRI workflow requires continuous case-by-case handling by an interdisciplinary team.