Market for bone densitometers may revive as central DXA regains ground

Vendors respond to needs for quicker scanning and automated reporting

Central dual x-ray absorptiometry (DXA) has been the core technology for diagnosing osteoporosis and monitoring its treatment for nearly a decade. But the sale of bone densitometers based on this technology languished with the proliferation of relatively inexpensive peripheral devices aimed at primary-care centers for osteoporosis screening.

Now central DXA may be poised for a resurgence as peripheral instruments have begun to fall from favor in primary care and the patient population at risk for osteoporosis is burgeoning. That doesn't mean the growth in central DXA will match that of the late 1990s. But the makers of DXA could see a steady 10% to 20% sales rise annually, driven by the release of products that address the needs of busy hospital and primary-care settings, according to Hologic executive Eric von Stetten, Ph.D.

Growth of the DXA market couldn't have been more robust in the 1990s, when the first drugs for treating osteoporosis hit the market, said von Stetten, vice president and general manager for the osteoporosis assessment division of Hologic. One year, he recalled, a manufacturer shipped as many as 2000 finger densitometers. Then there was a cooling-off period as primary-care centers turned from the table-sized central DXA units that measure bone density in the spine and hip to more manageable peripheral devices that assess bones in the finger and heel.

But the explosive growth in peripheral bone densitometers fizzled when physicians realized that measuring bone density with bread-and-butter hip and spine instruments was the only way to make a primary diagnosis of osteoporosis.

Von Stetten explained that the boom in bone density testing was driven by a desire to diagnose osteoporosis so treatment could be started, not just to screen patients who might be at increased risk for the disease. As soon as physicians realized that peripheral devices could only screen for osteoporosis--not diagnose it--sales plummeted, he said. As osteoporosis diagnosis has become part of mainstream primary care, there's been a return to central DXA for measuring bone density at the hip and spine.

The larger number of patients, mainly menopausal women, who may benefit from osteoporosis treatment is also feeding the rising interest in central DXA. The fastest growing segment of the population in the next five to 10 years, according to the U.S. Census Bureau, will be the leading edge of the baby boom, those between the ages of 55 and 64. And the risk for osteoporosis in this age group is high. In a study of 200,000 women over 50 in 34 states, almost 50% already had osteopenia or full-blown osteoporosis.

The current controversy about estrogen replacement therapy will further fuel the move toward central DXA, von Stetten said. There's been little need for primary-care physicians to routinely order central DXA for menopausal women because for the last several years they've automatically placed these women on ERT. But because of recent concerns about the efficacy of ERT for osteoporosis prevention and potential side effects, primary-care physicians will no longer be so quick to prescribe ERT and will be more willing to find and treat women who may suffer bone loss.

"We see two things happening. We see hospitals buying second, third, fourth, and even fifth DXA units for their outlying clinics or because their volume is so high they need multiple units," von Stetten said. "And outside the hospital, primary-care centers are buying bone densitometers because physicians and patients believe it is a standard test, especially for menopausal women."

Advances in central DXA are making it easier for busy hospitals and primary-care centers to run osteoporosis diagnosis and treatment programs. At the RSNA meeting, Hologic introduced Discovery, its latest generation of the QDR Series bone densitometer and the replacement for its Delphi products.

Discovery incorporates several Delphi features. Delphi's One Pass Technology allows single-sweep scanning to generate high-resolution images in just 10 seconds and is making the move to Discovery. Linear fanbeam geometry provides rapid, high-resolution single-energy imaging as well as dual-energy bone density measurements. A third crossover is the patented Internal Reference System, which automatically calibrates bone density pixel by pixel.

The Anthropomorphic Spine QC Phantom, which compares measurements to a life-like standard, and Instant Vertebral Assessment, which in 10 seconds captures a single-energy image of the spine to enable a search for fractures while taking bone density measurements, also made the jump to Discovery.

To these core elements, Discovery adds Express BMD (bone mineral densitometry), which measures bone density at the spine and hip in 10 seconds, and Express Exam, which automates routine scan protocols for positioning and scanning patients and analyzing data. Image Pro, an optional tool on the Delphi that digitally sharpens images of vertebral fractures, is standard on Discovery.

Hologic has two other new technologies. One is CADfx, a computer-aided fracture assessment tool for quantifying the degree of vertebral compression and simplifying interpretation of the vertebral assessment. The other is electronic reporting for streamlining interpretation and documentation of bone density assessments and integrating them with health information systems.

GE Medical Systems has also been adding new technologies to its line of bone densitometers. These include a third-generation fanbeam system, computer-aided densitometry, dual femur and spine scan capability, portable image review and analysis, advanced hip assessment for monitoring hip axis length and the upper neck region, and lateral vertebral assessment.

Improvements in central DXA are responding to the needs of the marketplace by enhancing productivity, von Stetten said. Not only is scanning and bone densitometry faster, but workflow is smoother, thanks to modality worklists and automatic feed of patient biographic information from hospital information systems. In the outpatient setting, scan data are being automatically routed to remote viewing stations. Software with configurable fields and speech recognition is providing one-step report generation. Such workflow enhancements will increase throughput--and translate into healthy sales.

"We're not going to see phenomenal growth, and growth is not going to be driven by bone density measurement products, but the market is vital, and DXA is well suited to it," von Stetten said.