Researchers at the Harvard-affiliated Brigham and Women's Hospital this week reported discovering a possible way to reach an early diagnosis in cases of Alzheimer's disease, the irreversible illness that impairs victims' memories.

The procedure involves injecting radioactive material into the brain of the suspected Alzheimer's victim and then taking photo-like images which record the pattern of blood flow in the patient's brain.

Alzheimer's victims have a decreased blood supply to certain brain areas, said Dr. B. Leonard Holman, the hospital's director of nuclear medicine. Holman and a team of doctors found that many of the disease's victims have identical brain "signatures," or blood flow patterns.

"The discovery will help in the fight to come up with an understanding, treatment, or even cure" for the disease, he said.

While hospitals currently have the capability to use the new diagnostic procedure, Holman said, its practical value is limited because there is no known cure or treatment for the disease.

"The disease causes severe debilitation. Usually it leads to death," Holman said.

Alzheimer's disease afflicts 2.5 percent of all people over 65 years old and "accounts for half of the total nursing home costs in this country," he said.

Alzheimer's disease, first reported by Elois Alzheimer more than 80 years ago, is a type of disease called dementia. Victims of the illness experience no physical disability but suffer progressive loss of memory. In the advanced stages of the disease, many victims cannot remember words long enough to form coherent sentences and do not recognize members of their family.

Alzheimer's disease has been particularly difficult to diagnose because of its similarity to other mentally crippling diseases.

"We used to diagnose by excluding stroke, depression, and other diseases. What we were left with was Alzheimer's," Holman explained.

Holman said additional research will focus on related forms of dementia and the development of "brain signature" patterns in Alzheimer's disease.