University of Guelph

Guard, Inc.

Tava Corporation

Innes K MacKenzie

Robert J Stone

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,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. The device also provides a method for calculating the distance from the source holder to the substrate using backscattering of gamma rays.

Method and apparatus for measuring thickness of coating layers on substrates using backscattering of x-rays and gamma rays

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,Cd 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.

Method and device for estimating bone mineral content of the calcaneus

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.

Method and apparatus for measuring ice thickness on substrates using

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.

Method and apparatus for measuring thickness of paint layers on

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.

A radioactive source holder for use with a NaI (TI) spectrometer for obtaining very low dose estimates in bone minerals in vivo, comprising a molybdenum tube, a gold insert within the tube, a blind hole within the insert for receiving the radioactive source, and an inner tube inserted into the blind hole for directing radiation from the source in a narrow cone, whereby the directing of radiation in the narrow cone minimizes spectrometer response to radiation which has been scattered by soft tissue overlying a bone.

Method and apparatus for low dose estimates of bone minerals in vivo

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. The method includes applying a source of constant gamma or x-rays substantially perpendicular from the center of the face of a detector to a target of unknown coating and to a calibration target of the same base material of known coating to cause the labelling material to emit characteristic fluorescent x-ray ranges from 4-90 kev, measuring the fluorescent x-ray and compton yields of the calibration target, measuring the fluorescent x-ray and compton yields of the target of unknown coating, deriving the source-target distance for the unknown coating from the compton yields, deriving the expected fluorescent x-ray of the calibration target of known coating at said distance, and comparing the measured fluorescent x-ray for the unknown coating to the expected fluorescent x-ray derived at said distance to obtain the coating thickness for the unknown coating. The constant source may be eliminated by measuring the ratio of compton and Rayleigh yields. For targets of variable base thickness, the center of the compton profile is measured.

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Guelph, Canada

Innes K MacKenzie