CAMBRIDGE, Mass., Aug. 11 -- A team of scientists at the Harvard Institutes of Medicine is working to develop a non-invasive method to image plaque deposits in the brains of patients with Alzheimer's disease as the disease progresses. To date, the only definitive means of diagnosing both the plaque formation and the disease itself has been a posthumous examination of the patient's brain. The Harvard studies were described in the July 29 issue of the Journal of Medicinal Chemistry.The technique involves coupling an isotope of the element technetium to large organic molecules that are known to have an affinity for the type of amyloid present in the brain of a patient with Alzheimer's disease. The imaging is then done with single-photon computed tomography, which detects gamma particles emitted by the trace amounts of radioactive technetium probe. Laboratory studies are in progress.