CT Colonography Provides Two-in-One Screening Approach for Cancer and Osteoporosis

New research reveals that computed tomography (CT) colonography, also known as virtual colonoscopy, has the potential to screen for two diseases at once--colorectal cancer and osteoporosis, both of which commonly affect adults over age 50.

Results of the study were presented in December 2008 at the annual meeting of the Radiological Society of North America (RSNA), held in Chicago, IL, USA. "With CT colonography, in addition to screening for colorectal cancer, we were able to identify patients with osteoporosis,” said lead author Rizwan Aslam, M.B.Ch.B., assistant clinical professor of radiology at the University of California, San Francisco (UCSF; USA).

CT colonography, an imaging modality performed to detect precancerous polyps in the large intestine, begins with an abdominal CT scan, which creates cross-sectional images of all structures in the abdomen including the spine. Computer software then assembles the CT images to create an interior or "fly-through” view of the colon.

Using the same CT images, another software application can create three-dimensional (3D) images of the spine, allowing bone mineral density to be measured. Low bone mineral density is usually associated with osteoporosis, a disease in which bones become fragile and more likely to break.

In the study conducted at the San Francisco Veterans Administration Hospital, the researchers evaluated the results of 35 patients who underwent CT colonography and bone mineral density testing with dual-energy X-ray absorptiometry (DEXA), a conventional bone density screening tool.

Patients included 30 males and 5 females ranging in age from 54 to 79. The results of the study showed excellent agreement between the DEXA bone-mineral-density scores and the data generated through the CT colonography study. "The bone density measurements obtained from CT colonography were comparable to the DEXA results,” Dr. Aslam said. "Both tests identified osteoporotic bones.”

Most physicians recommend that adults undergo CT colonography or conventional colonoscopy every seven to 10 years beginning at age 50. "CT colonography isn't a replacement for DEXA testing, but it could be a way to screen more people for osteoporosis,” Dr. Aslam said. "When an individual undergoes CT colonography, we can also obtain a bone density measurement with no additional radiation and at minimal cost.”

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