Bone Mineral Densitometry (BMD), also known as dual energy x-ray absorptiometry (DEXA or DXA), is a specialised low-dose X-ray technique used to determine bone strength and measure bone loss. 

How is BMD performed?

A machine detects the amount of X-rays that pass through the bones. Bone mass will obstruct X-rays  passing through. Thus, the more energy detected passing through the bones, the less dense and weaker the bone is.

BMD value is determined by two scores generated from the scan. The T-score, indicating the amount of bone loss, is calculated by comparing the patient’s current BMD, to the peak bone mass achieved by healthy young individuals, while the Z-score compares the patient’s bone loss to the expected bone loss of other individuals of the same age. These scores help assess whether the patient’s BMD is normal.

These measurements are used for the diagnosis of osteoporosis, estimation of the fracture risk, and assessment of response to treatment.

Is BMD safe?

The radiation dose is very low for a BMD scan. While it is a safe procedure, it is not recommended for pregnant women, due to the low-level radiation exposure to the developing foetus.

Bone Mineral Density (BMD) Scan  [ 1.86 MB | PDF ]