New research to be released this week at a major Alzheimer's Disease conference suggests physicians using positron emission tomography or PET scans are now able to detect physical signs of the disease that previously had been possible only via autopsy.
The technique is just one of the latest in a series of novel applications of nuclear medicine, which has evolved far beyond its traditional area of imaging for tumors.
At the 8th International Conference on Alzheimer's Disease and Related Disorders in Stockholm, Sweden, which began on Saturday and runs until July 25, researchers will report on several studies that showcase potential applications of PET for the management of Alzheimer's disease.
Speaking from Stockholm, a spokesman for the Alzheimer's Association, host of the conference, told United Press International scientists using PET scans were able to image a key characteristic of the disease, the amyloid plaques in the brains of people known to have developed its early stages.
After 10 years of effort, an international team of researchers has developed an agent that pierced the so-called "blood-brain barrier" and allowed scientists at Uppsala University PET Center in Sweden to scan for the plaques. Until now, the only way to confirm the presence of the plaques was an autopsy.
If confirmed in larger trials, "Its importance initially would be to test the impact of drugs on the disease," said William Theis, vice president of medical and scientific affairs for the Alzheimer's Association. At present, drug test results depend largely on relatively slow and imprecise cognitive tests to demonstrate a therapy's impact on patients, Theis said, "This has the potential to give us a much quicker answer."
At recent gatherings of nuclear medicine specialists, as well as in interviews with UPI, researchers have reported progress on technologies and imaging agents in such areas as locating chemical or process errors at the heart of all major disease areas, monitoring the effect of therapies and aiding the development of therapies.
For example, this year for the first time, the Food and Drug Administration has approved a radiopharmaceutical -- not for imaging but for therapy. The agent, Zevalin, by IDEC Pharmaceuticals Corp. of San Diego, Calif., was approved in February for treatment of a condition called relapsed, or refractory, low-grade follicular, or transformed, B-cell non-Hodgkin's lymphoma -- a cancer of the lymphatic system.
The agent combines a molecule that binds only to the cancer with a radioactive chemical that kills the cancer.
In nuclear medicine, physicians inject imaging agents into patients. These agents, called radiopharmaceuticals -- literally, radioactive drugs -- perform two functions. First, they accumulate in a target tissue in the body or bind to a predetermined molecule, such as amyloid plaque in the case of Alzheimer's Disease. Second, they emit a very short-lived, tiny amount of radioactivity that permits diagnostic targets to show up on PET scans or other imaging devices.
One key feature of nuclear medicine imaging is its ability to detect changes in the body's function or chemistry. For example, nuclear medicine is used to reveal areas of the body where glucose accumulates at an abnormal rate. This often is an indicator of malignancy or, in the case of Alzheimer's, decreased brain function.
Dr. Michael Phelps, who invented PET in 1973 and 1974, told UPI recently he anticipates current research using PET scans will lead to detection of errors in chemistry and function related to Alzheimer's Disease 10 years before the appearance of symptoms. Also, Phelps said, the technology probably will be applied to find signs of impending metastasis -- before a cancer begins to spread to distant parts of the body.
Because of its ability to monitor the presence of diseased cells in the body, Phelps and others said the technology already is being used actively by pharmaceutical companies to guide development of new drugs. He said micro-PET scanners are sold to drug companies for use with mice -- the test animals for drugs.
Additional examples of evolving nuclear medicine applications include:
-- The use of PET imaging to assess the prognosis for patients with gliomas, or brain tumors, appears better than traditional pathological grading, researchers from the Wallace-Kettering Neuroscience Institute in Kettering, Ohio, report.
-- Using a technology known as SPECT, for single-photon emission computed tomography, physicians using myocardial perfusion imaging -- which tracks the flow of blood to the heart muscle -- may be able to detect which patients with diabetes are at risk for cardiovascular disease, according to a new study of 189 patients with diabetes.
The imaging found stress-induced ischemic, or loss of blood flow, defects in 56 percent of the participants, while electrocardiogram changes were observed in only 14 percent of the patients in the study. The report comes from Dr. John O. Prior, and colleagues from the Centre Hospitalier Universitaire Vaudois in Lausanne, Switzerland.
-- An imaging agent approved for the evaluation of solitary pulmonary nodules in patients suspected of lung cancer now appears able detect leftover lung cancer cells in patients initially believed cured by surgery. About 25 percent of lung cancer patients die within five years from spread of the disease even though surgeons considered them surgically cured.
A radiopharmaceutical called depreotide, or NeoTect, by Berlex Laboratories Inc. of Richmond, Calif., shows promise in identifying patients in whom there is a likelihood for recurrent cancer, said Dr. Alan D. Waxman, director of nuclear medicine at Cedars-Sinai Medical Center in Los Angeles.
-- Researchers at Memorial University of Newfoundland in St. John's, Canada, used a nuclear medicine study to show that in cigar smokers, everyone inhales even though they might say otherwise.
In a study of 24 male cigar smokers, led by Dr. L. J. McDonald, participants smoked a cigar through a holder that permitted cigar smoke to mix with radiolabled particles. Then their breaths were scanned. Although 79 percent of the participants reported they did not inhale during cigar smoking, the study found they all inhaled.
-- In Japan, the HIMEDIC Imaging Center at Lake Yamanaka has been offering periodic PET scans to 5,716 members of a medical health club. The scans found malignant tumors in 115, or 2 percent of the members. This figure is 10 times higher than the 0.2 percent tumor rate found in Japan by conventional diagnostic methods, the researchers noted.
Even so, Dr. Phelps and others said, at least for the foreseeable future, PET imaging, at a cost of $2,000 per session, should be restricted to those with some indication of risk, either due to their own medical history, their family history, or genetic predisposition for cancer.
