| 摘要 |
The present invention provides an in situ, low dose and noninvasive method and device for estimating bone mineral content of trabecular bones, particularly the calcaneus. The method of estimating bone mineral content involves measuring the intensity of X-rays backscattered from the calcaneus and estimating the calcium content from this intensity. The apparatus includes an axially symmetric heavy-metal radioactive source holder (collimator) containing a radioactive source mounted on the axis of a cylindrically symmetric scintillation counter or detector. In a preferred embodiment of the device, a 109Cd radioactive source that emits the K X-rays of silver (22 to 25 Kev) is used. A person's foot is immobilized on the apparatus with a spring-loaded X-ray collimator bearing against the back of the heel. The method relies upon measuring the total intensity of X-rays backscattered from the calcaneus (heel bone). The X-ray energy is selected on the basis that it is low enough to ensure a strong contrast in the absorption of both the primary and scattered X-rays because of the presence of calcium. X-rays are backscattered primarily via Compton scattering and are detected by the scintillation detector. Periodic measurements of the calcium content in a person's caleaneus using the present method and device permits one to monitor the development of osteoporosis based on changes in the X-ray albedo of the calcaneus resulting from changes in concentration of calcium phosphate over time.
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