The National Institutes of Health in Bethesda, Md., is conducting a $60 million, five-year study to identify biological markers of Alzheimer’s disease. The project, part of the Alzheimer ’s Disease Neuroimaging Initiative, will employ serial MRI and PET scans; measurements of biological compounds in blood, cerebrospinal fluid and urine; and clinical and neuropsychological assessments. Siemens AG of Munich, Germany, Philips Medical Systems of Surrey, UK, and General Electric Co. of Fairfield, Conn., are providing software support for the imaging aspects of the study. Scientists hope that the study will permit the detection of biological changes before memory decline appears and the evaluation of drug effectiveness as early as possible.