Nearly a century after Alzheimer’s disease was first identified, there has been no foolproof way to diagnose the illness in a living patient. But a new method used by doctors at UT Southwestern Medical Center at Dallas is almost 100 percent accurate when combined with clinical assessment. Testing blood flow in a specific region of the brain may boost the degree of diagnostic certainty in difficult cases from 90 percent to almost 100 percent, said Dr. Frederick Bonte, director of the Nuclear Medicine Center at UT Southwestern.