**2.5 Comparison of various imaging examination techniques**

In conclusion, the above imaging techniques have their own emphasis: DXA has been widely used to evaluate BMD because of its economy, simplicity and low radiation. What's more, WHO has also recommended it as the "gold standard" for diagnosing OP. Although QCT is more accurate in measuring volume BMD, it can measure cortical bone and cancellous bone BMD respectively, but the radiation is larger. QUS is simple and radiation-free, which is mainly used as a screening tool for osteoporosis. MRS is radiation-free and can indirectly assess bone quality at the molecular level. On the premise of bone mineral density measurement, MR combined with QCT or QUS for the detection of osteoporosis, the combined application of multiple methods enhances our scientific understanding of bone microstructure, bone geometric properties and other biomechanics, and provides a basis for further exploration of osteoporosis. The pathophysiological process of the disease, sensitive clinical diagnosis, monitoring of disease changes and curative effects provide technical support (**Table 2**).


#### **Table 2.**

*Comparison of imaging techniques for various bone mineral density examinations.*
