How many is enough? Sample size estimation for imaging‐based outcomes in clinical trials of neurodegenerative disease

Effective treatments for neurodegenerative diseases are a global health priority. Appropriately powered clinical trials are critical to showing evidence of efficacy ‐ these are expensive and take years to complete. Depending on the study aims, imaging biomarkers can provide high precision measurements that reflect underlying pathology or downstream effects and may help in reducing the number of participants and/or duration of the trial. Identifying how to design trials that make the most efficient use of imaging endpoints, while maintaining sufficient statistical power to detect the desired therapeutic effect, will be critical to reduce approval time for effective therapies.