MRI is a non-invasive imaging technology that produces detailed three-dimensional anatomical images. It is used for a wide range of purposes, from diagnosing brain disorders to monitoring the progression of diseases like cancer. In epidemiology, MRI can be instrumental in studying chronic diseases. For instance, it allows researchers to investigate brain changes in populations at risk for Alzheimer's disease. By analyzing MRI data, epidemiologists can identify early biomarkers of disease, which helps in understanding disease etiology and potential interventions.