Computed tomography and opportunistic osteoporosis screening

Osteoporosis is a serious health problem associated with a high risk of fractures, morbidity, and mortality. Although population-based screening using clinical examination, the "Fracture Risk Assessment Tool" questionnaire, and bone densitometry (DXA) was introduced in the Czech Republic in 2023, some patients remain undiagnosed. One way to improve early diagnosis is through opportunistic screening, i.e., the use of CT scans already performed for other indications. CT scans contain information on bone density, which can be obtained by measuring the CT attenuation of trabecular bone-most commonly in the L1 vertebral body-expressed in Hounsfield units (HU). Low CT attenuation values indicate reduced bone mineral density and can serve as a basis for recommending a follow-up DXA scan. In addition to CT attenuation measurements, the presence of vertebral compression fractures is also a significant finding; these are often overlooked, even though they are associated with a significantly increased risk of future severe femoral fractures. The advantages of opportunistic screening include the use of existing data without additional radiation exposure, an increase in the number of patients detected, and potential cost savings. The disadvantages include difficulties in standardizing the evaluation, greater labor intensity, and the fact that it targets only individuals who have already been examined within the healthcare system. Bone CT attenuation value are is primarily influenced by the X-ray tube voltage during CT scanning, the calibration of the CT scanner, and the use of intravenous contrast agents. Therefore, it is necessary to interpret the results with regard to the technical parameters of the examination. The use of specialized software and artificial intelligence offers a promising prospect. Opportunistic screening for osteoporosis has the potential to improve early diagnosis. Its wider implementation requires standardization of methodology and collaboration among healthcare administrators, clinicians, radiologists, and radiation physicists, as well as the use of modern information technologies.

Keywords: Computed tomography, Hounsfield units, opportunstic screening, osteoporosis.