How is bone density measured?

Bone mineral density (BMD) can be measured using three methods.

1. Ultrasound:

Ultrasound-based BMD measurement assesses bone mineral content and bone strength by evaluating ultrasound velocity and amplitude attenuation. This technique is sensitive to soft tissue, bone tissue, and bone marrow structures, and the calcaneus (heel bone) is the most commonly examined site. Currently, it is primarily used for screening individuals at risk of osteoporosis and for assessing the risk of osteoporotic fractures.

2. Computed Tomography (CT):

CT typically measures trabecular BMD in the lumbar spine and proximal femur. Quantitative CT (QCT) is a clinically validated method for measuring BMD at the spine, hip, forearm, and whole body. QCT is mainly employed to evaluate disease severity associated with abnormal BMD and to monitor treatment response. Moreover, QCT provides more accurate measurements in patients with obesity or low body mass index (BMI).

3. Dual-Energy X-ray Absorptiometry (DXA):

DXA quantitatively measures and evaluates skeletal mineral content. This technique can assess bone mass at any skeletal site with high precision and minimal radiation exposure. It utilizes an X-ray tube equipped with a special filter to generate two distinct photon energy beams—low-energy and high-energy. After penetrating the body, these photon beams are detected by the scanning system and the acquired data are processed by a computer to calculate bone mineral content.