[Principle and instruments of bone densitometry]

Various methods for measurement of bone densitometry have been developed over the past two decades. This paper discribes the basic principle, technical characteristics and clinical performance on the SPA, DPA, QCT and newly developed DEXA. Advantage of SPA is low cost with high precision, but the method is used to measure only the distal radius. QCT can measure only the trabecular bone from the cortex, but requires high radiation dose. DEXA is similar in concept to DPA, but affords many advantages, i.e. higher precision, higher resolution, shorter examination time and lower dose than the DPA. This new DEXA should allow more accurate and precise management in patients with metabolic bone diseases.