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.

Inclusion Criteria:

• Both sexes.
• All ethnicities.
• Age equal or above 18 years.
• Any clinical indication (no specific pathology is required) for a CT scan of the lumbosacral spine or abdomen in which the entire lumbar spine (L1 to L5), paravertebral muscles, abdominal aorta, and subcutaneous adipose tissue are visible.
• Ability to give informed consent.

Exclusion Criteria:

• General contraindications to CT examination, including pregnancy or body weight/size exceeding scanner limits.
• Severe degenerative manifestations of the lumbosacral spine.
• Severe scoliosis of the lumbosacral spine.
• Surgical hardware that prevents adequate CT scanning.
• Oncologic pathology in progress or in recent history.
• Any other situation deemed incompatible with the study by the designated physician or investigator.

The study will involve a population of patients undergoing CT scans including the lumbar spine at the Diagnostic and Interventional Radiology Unit of each participating center. In CT scans requiring the administration of contrast medium, only the non-contrast-enhanced images will be considered.