MK-6240 is primarily used in medical research as a positron emission tomography (PET) imaging agent. It is specifically designed to detect and quantify tau protein aggregates in the brain, which are associated with neurodegenerative diseases such as Alzheimer's disease. By binding selectively to tau tangles, MK-6240 allows researchers and clinicians to visualize and monitor the progression of tau pathology in living patients. This aids in early diagnosis, tracking disease development, and evaluating the efficacy of therapeutic interventions targeting tau-related mechanisms. Its application is crucial for advancing understanding and treatment of tauopathies.