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History of the MGH Bone Density Center

The history of the Bone Density Center at Massachusetts General Hospital encompasses major technological innovations that have improved the diagnosis and treatment of osteoporosis and other generalized bone diseases. The center opened in the 1970's when MGH physicians purchased a new research device invented at the University of Wisconsin to measure bone mass non-invasively in people. Until that time, a bone's mass was assessed by judging its whiteness on a simple x-ray picture, a procedure so insensitive that osteoporosis could not be diagnosed until it had caused fractures. The new research device measured bone mass more accurately by using a beam of radioactivity (from radioactive iodine) instead of x-rays, using a radioactivity detector instead of x-ray film, and using a computer instead of the human eye. Known as a single photon absorptiometer, the new device eventually became commercially available and greatly enhanced research on osteoporosis and other metabolic bone diseases. The MGH laboratory was the first in the eastern United States to possess a single photon absorptiometer and one of the first in the country to make forearm bone density measurements available to practicing physicians for routine patient care.

llustrated is a photo of a person undergoing this early bone density measurement with a single photon absorptiometer (see figure 1). Rigid immobilization of the patient's arm for ten minutes was required to perform one measurement.The patient's arm was surrounded by a water-filled balloon to compensate for anatomical differences in soft tissue surrounding the bone.

The University of Wisconsin and other medical centers subsequently extended single photon absorptiometry technology to measure bone density in the spine and hip. This required radioactivity beams of two different energies, one stronger than the other (dual photon absorptiometry). The technology was difficult to implement because the radioactive isotopes varied in purity, and each measurement took 30 minutes, during which a patient had to remain completely immobile.

In 1987 a Massachusetts company, Hologic inc., developed a faster and more reproducible way to measure bone density in the spine and hip. Hologic's technique used an x-ray beam of two different energies instead of radioactivity, but continued to use radiation detectors instead of film and computers instead of eyes. This new technology was known as quantitative digital radiography, or dual energy x-ray absorptiometry (DXA), and was first introduced into clinical medicine and osteoporosis research by the MGH Bone Density Center ( click to view the first scientific publication describing the use of this technique in humans).

DXA has subsequently become the world's standard method for measuring bone density and has revolutionized medical care and treatment of osteoporosis, and osteoporosis research. DXA allows osteoporosis and related bone diseases to be diagnosed early, before a person experiences a fracture, and physicians and researchers to establish the effectiveness of ostoporosis treatments in groups of patients and in individuals. This has enormously accelerated the development and dissemination of improved methods to prevent, arrest or reverse ostoporosis. The following graph illustrates the growth in the number of DXA measurements performed by the MGH Bone Density Center in recent years.

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