Meanwhile, the OEMs aren't waiting around for the government to restore full funding for bone density screening, although a bill is proposed (see sidebar). Manufacturers have come up with new applications for what is turning out to be quite a versatile technology. For instance, since the DXA system can measure bone loss, why not use it to measure gain? That simple new use implies an important additional application to heart disease diagnosis, and another large population at risk.

"One of the goals we have is finding more uses for these devices. If the doctor can't justify owning a machine solely for osteoporosis testing, what else can they get out of the machine?" said Hologic's Jenkins. The company has FDA approval to use bone density scanning to look at aortic calcium, which is a major risk factor for cardiovascular disease. "When you look at the prevalence of cardiovascular disease in this country... here we have added another very useful exam to the machine."


In this application, the DXA technology takes a quick image of the lumbar and thoractic spine, which is part of the standard DXA exam, but visualizes abdominal aortic calcification to assess risk.

BMD Testing is More Than DXA

The proposed legislation to restore funding specifically mentions Dual Energy X-ray Absorptiometry. DXA (or DEXA) is by far the most widely used technology to measure bone density, although others are in use and emerging.

It's important to know that a "bone densitometer" is not necessarily a DXA machine. Other modalities also measure bone density, such as portable ultrasound for mass screening efforts. A more sensitive technology for bone health scanning is QCT, which uses CT enhanced with software and phantoms. You can get a QCT package from the CT manufacturer or from specialized companies such as Image Analysis and MindWays.

"QCT is a more sensitive measure than DXA because we are looking at only the metabolic bone," explained Roger Schulte, Vice President of Sales and Marketing, Image Analysis, Inc., Columbia, KY. "We can see bone loss much faster and we can see recovery in the event of drug therapy much faster. We can see changes in six months that take DXA two years."

Despite this advantage in detecting improvement during therapy, the much wider adoption of DXA, and the prospective data that it has amassed convinced regulators and Medicare that only DXA should be used to track patients during the course of treatment.

"Science is going in the opposite direction; we have been prohibited from scanning patients more than for the initial screening test," Schulte said. He noted that QCT is most widely used in rural hospitals that can add it on to their CT technologies affordably in lieu of acquiring DXA; and QCT is used in research. The technology is impressive and attractive. For instance, after the capital cost of the CT scanner, a QCT add-on has almost no impact on the radiology budget. QCT phantom calibration is also being applied to quantifying calcium in the descending aorta and coronary arteries.

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