This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anatomy
Gold standard for diagnosis of osteoporosis- 
Select and explain. 
A. DEXA, B. Single beam densitometry, C. Quantitative computed tomography, D. Bone histomorphometry
A: DEXA
Answer: A: DEXA 
Explanation: *Gold standard for diagnosis of osteoporosis is DEXA scan. DEXA SCAN * Commercially introduced in 1987. * Principle - 2 x ray of 70Kv and 140kv are fired on site of measurement with lag time of 4ms. * Detector detects accentuation of 2 beams. * Data is fed into computer powered with complex algorithm and calculates BMD. * SITES- * Central dexa- lumbar spine, hip, whole body. * Peripheral dexa- forearm , calcaneum. * CONTRAINDICATIONS- * PREGNANCY. * RECENT ADMINISTRATION OF CONTRAST. AGENT,NUCLEAR MEDICINE SCAN. * RADIOPAQUE IMPLANT IN MEASUREMENT AREA. * MARKED OBESITY ref : maheswari 9th ed