Massachusetts Institute of Technology (MIT) scientists have developed a new dye that could offer noninvasive early diagnosis of Alzheimer's disease, a discovery that could aid in monitoring the progression of the disease and in studying the efficacy of new treatments to stop it. The work is published in Angewandte Chemie. Today, doctors can only make a definitive diagnosis of Alzheimer's--currently the fourth-leading cause of death in the United States--through a postmortem autopsy of the brain. "Before you can cure Alzheimer's, you have to be able to diagnose it and monitor its progress very precisely," says Timothy Swager, leader of the work and a professor in MIT's Department of Chemistry. "Otherwise it's hard to know whether a new treatment is working or not."