Abstract: 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. In one embodiment the X-ray source is a small x-ray tube that provides a continuous energy spectrum of X-rays. The intensity of backscattered X-rays from the soft tissue covering the trabecular bone, preferably the calcaneus, is compensated for by directly measuring the thickness of the soft tissue. Alternatively the soft tissue thickness can be measured directly along with the bone mineral content from the backscattered X-rays by measuring intensity over an energy range and correlating these results with a model of backscattering from a trabecular bone covered with a layer of soft tissue.

Abstract: The present invention provides a method and apparatus for non-destructive, in situ measuring thicknesses of layers on substrates. The method and device uses a probe including a radioactive source in a source holder and a photodetector mounted behind the source for detection of backscattered photons. In one aspect the method is used to measure the thickness of paint deposited onto metal substrates. The source holder and photodetector array forms a cylindrically symmetric probe for producing an axially symmetric beam of primary photons. A source containing radioactive 109Cd producing high energy photons of energy 22 and 25 keV is spaced from the painted surface so the photons impinge on the painted substrate. The intensity of photons backscattered by Compton scattering in the paint layer is proportional to the mass density of the paint to give a direct measurement of the paint thickness. The photons penetrating through to the substrate are absorbed within the substrate.

Abstract: 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).

Abstract: The present invention provides a method and apparatus for in situ measuring thicknesses of ice buildup on airfoil. The method and device uses a probe including a radioactive .sup.241 Am gamma ray source producing 60 keV gamma ray photons which penetrate through the airfoil substrate and a photodetector mounted behind the source for detection of backscattered gamma rays. The probe is mounted on the interior of the airfoil and secondary radiation is backscattered within the ice layer and back through the airfoil substrate to the photodetector. The shape and density of the source holder in addition to the geometrical arrangement of the source and detector with respect to the airfoil substrate are used to block a substantial fraction of gamma rays backscattered in the airfoil substrate thereby favoring scattering in the ice layer over that in the airfoil material.

Abstract: The present invention provides a method and apparatus for nondestructive, in situ measuring thicknesses of layers on substrates. The method and device uses a probe including a radioactive source in a source holder and a photodetector mounted behind the source for detection of backscattered photons. In one aspect the method is used to measure the thickness of paint deposited onto metal substrates. The source holder and photodetector array forms a cylindrically symmetric probe for producing an axially symmetric beam of primary photons. A source containing radioactive .sup.109 Cd producing high energy photons of energy 22 and 25 keV is spaced from the painted surface so the photons impinge on the painted substrate. The intensity of photons backscattered by Compton scattering in the paint layer is proportional to the mass density of the paint to give a direct measurement of the paint thickness. The photons penetrating through to the substrate are absorbed within the substrate.

Abstract: The present invention provides a method and apparatus for in situ measuring thicknesses of ice buildup on airfoil. The method and device uses a probe including a high energy radioactive gamma ray source .sup.241 Am producing 60 keV photons which penetrate through the airfoil substrate and a photodetector mounted behind the source for detection of backscattered photons. The probe is mounted on the interior of the airfoil and secondary radiation is backscattered within the ice layer and back through the airfoil substrate to the photodetector. The shape and density of the source holder in addition to the geometrical arrangement of the source and detector with respect to the airfoil substrate are used to block photons backscattered in the airfoil substrate thereby favoring scattering in the ice layer over that in the aluminum.

Abstract: A method of measuring a coating thickness applied on a target of constant base material, such coating containing a non-radioactive labelling material having an atomic number higher than 20.