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: Radiology
[{'content': 'Which of the following investigation is considered to be the gold standard in the diagnosis of osteoporosis? \nSelect and explain. \nA. Ultrasound, B. Dual energy X-ray absorptiometry, C. Single energy X-ray absorptiometry, D. Quantitative computed tomography', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Osteoporosis is a group of disorders characterized by reduced bone mass or density in the absence of defect in bone mineralization. Dual energy X ray Absorptiometry (DEXA) scan is the gold standard method in the diagnosis of osteoporosis. It is a quantitative method for measuring bone mass by using low energy X ray beam. Using this method bone mass is measured in units of gram per cubic centimeter of bone. WHO criteria for osteoporosis is a DEXA scan T score at or below -2.5. T score between +1 and -1 indicates normal bone, between -1 and -2.5 indicates osteopenia. Ref: Internal Medicine: An Illustrated Radiological Guide By Jarrah Ali Al-Tubaikh, Page 219', 'role': 'assistant'}]