A bone densitometry scan can measure the calcium content in the bones while the conventional X-Ray may show the same results but with far less accuracy. It is possible that someone can have particular bone disease like osteoporosis but he may have perfectly normal X-Ray scans. X-ray is good in detecting the fractures and is more reliably used for the same. X-ray beam is directed towards the part of the body which needs to be evaluated. The amount of X-ray absorbed by the bone will reflect the bone mineral density of the bone which can be later calculated using the computer devices by subtracting the amount of the radiation absorbed by the soft tissues of the body. It is a painless procedure.

Indications

• To evaluate osteoporosis patients for the risk of getting fractures in forthcoming years.
• Those persons who have below normal bone mineral density are at a greater risk of getting fractures. 
• These scans are regularly done in patients who are having some or other bone disease so as to access the improvement of the condition and the effectiveness of the treatment.

Benefits and Risks

• It is a noninvasive and simple procedure which does not requires any anesthesia
• Less exposure to radiations compared to the conventional X-ray which has risk of far more radiation exposure to the body
• It is the best method to evaluate and diagnose a case of osteoporosis
• It is convenient for a patient also to get the scan done and also is a trusted method for the physician for the follow up of the cases
• Pregnant women should refrain from taking up the DEXA scan as radiation may harm the fetus
• This procedure is free from complications.

Limitations

• It is indicative of fracture but cannot predict the fracture
• In cases with spinal deformities CT scan is more useful than DEXA scan
• Central DEXA devices are more accurate than the peripheral DEXA devices but cost is the limiting factor for their usage.