Calibr-Ì: Comparative Evaluation of Phantomless Calibration Methods to Quantify Bone Mineral Density for Opportunistic Analysis of CT Scans

Osteoporosis is a systemic disease characterized by a reduction in bone mineral density (BMD) and qualitative alteration of the skeleton, resulting in increased bone fragility and fracture risk. The epidemiological impact of osteoporosis is extremely high. Proper diagnosis and clinical management of osteoporosis are critical to reducing the incidence of fragility fractures and preventing their complications. The diagnosis is generally confirmed by instrumental analysis of bone mineral density. The standard method is X-ray bone densitometry (DXA), which allows diagnosis based on criteria defined by the World Health Organization (WHO) by virtue of the T-score. DXA is a relatively quick and inexpensive examination with low exposure to ionizing radiation. However, this method has limitations in detecting fracture risk, and in addition, not all patients are properly referred for DXA services, which, among other things, require specific criteria to be reimbursed by the National Health System. Currently, computed tomography (CT) scanning is the most widely used three-dimensional diagnostic modality in clinical practice, and the number of investigations performed in high-income countries is continuously growing. Quantitative assessment of bone mineral density by CT is possible by proper calibration of the machine for the purpose of converting the CT numbers (or Hounsfield units) measured by the scanner into BMD units.