Cardiac CT Can Pull Double-Duty as an Osteoporosis Test

Cardiac CT scans can be used to effectively screen patients for osteoporosis without adding any time to the exam or exposing patients to any additional radiation, according to new research.

Osteoporosis affects approximately 200 million people worldwide, putting them at a greater risk of bone fracture, but, most people at risk are not screened. Even when they are, the current cadre of drugs, while effective in reducing the likelihood of a bone break, can cause harsh side effects. Consequently, early detection and treatment are critical.

In a study published Tuesday in Radiology, investigators from Denmark outlined how adding the bone mineral density (BMD) test used to diagnose osteoporosis to cardiac CT can improve screening for the disease, potentially accelerating treatment.

“Osteoporosis is a prevalent, under-diagnosed and treatable disease associated with increased morbidity and mortality,” said lead study author Josephine Therkildsen, M.D., from the department of cardiology at Herning Hospital, Hospital Unit West in Denmark. “Effective anti-osteoporosis treatment exists and so, identifying individuals with greater fracture rate who may benefit from such treatment is imperative.”

The Mindways Solid phantom with volume of interest in the quality assurance phantom (red circles, left side). A participant's noncontrast-enhanced axial CT (right side) with volume of interest (yellow circles) in the trabecular bone compartment of three vertebrae for bone mineral density measurements. Courtesy: Radiological Society of North America

While BMD is an effective way to pinpoint individuals with osteoporosis, too few people get the test, the researchers said. Other CT exams, such as CT colonography, can assess a patient's osteoporosis risk. However, relying on this scan cannot catch all vulnerable patients. That is why Therkildsen’s team turned to cardiac CT as another option – the scan already captures the thoracic vertebrae that form the vertebral spine in the upper trunk. Therefore, using the test to screen for osteoporosis was as simple as adding on the BMD test.

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The Study

To determine whether this combination could successfully identify osteoporosis cases, the team enrolled 1,487 people in a study. Participants underwent cardiac CT for heart disease evaluation, and investigators added BMD testing of three thoracic vertebrae to the scan by using quantitative CT software.

According to the analysis of these scans, 179 people – 12 percent of the group – had very low BMD. Follow-up revealed that, of that group, 80 people – 5.3 percent – experienced a fracture within the three years. Among those fractures, 31 were osteoporosis related. The relationship between very low BMD and the higher fracture rate, the researchers said, shows that thoracic BMD can be used to guide osteoporosis preventive measures and treatment decisions.

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The Impact

But, the BMD-enhanced scan is not only effective – it can also be done without any additional impact on the patient. Including BMD does not add time to the exam or expose the patient to any more radiation, the researchers said.

“We believe that opportunistic BMD testing using routine CT scans can be done with little change to normal clinical practice and with the benefit of identifying individuals with a greater fracture rate,” Therkildsen said.

With a proper calibration system in place, continuous scanner stability, and systemic imaging acquisition techniques, providers can capture the BMD measurements necessary for diagnosis. Although the team used cardiac CT for this study, it is possible, they said, that any CT images that include views of relevant bone structures could be used for BMD measurements, and the development of fully automated software that capture those measurements bolsters the adaptability and utility of this approach.

Still, the investigators said, further research is needed to not only pinpoint the best BMD cut-off values for treatment, but to also gather more information about fracture risks based on gender and body region. Additional investigations should also examine clinical risk factors, they said.

“Our research group is dedicated to extend the research in this field,” Therkildsen said, “as we believe it should be added to clinical practice.”

Overall, said Miriam A. Brendella, M.D., professor of radiology at Harvard Medical School and musculoskeletal radiologist at Massachusetts General Hospital, in an accompanying editorial, Therkildsen's team did effectively determine that thoracic spine CT can be used for osteoporosis screening and assessing fracture risk. And, implementing it can open the door to better treatment for a wide variety of patients.

"[The team] expanded opportunistic osteoporosis screening to involve the throacic spine," Bredella said. "I hope this study will ignite interest in using chest CT examinations performed for other purposes, such as lung cancer screening, for opportunistic osteoporosis screening and prediction of fractures in vulnerable populations."