Optics: measuring and testing – With sample preparation
Reexamination Certificate
2000-09-29
2002-12-17
Stafira, Michael P. (Department: 2877)
Optics: measuring and testing
With sample preparation
Reexamination Certificate
active
06496250
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method for screening transparent materials, and more particularly to a combinatorial method for screening an array of transparent materials.
2. Description of Related Art
Combinatorial chemistry techniques have been developed by the pharmacutical industry for the rapid development and screening of drug chemistries. For example, Pirrung et al. developed a technique for generating arrays of peptides and other molecules using, for example, light-directed, spatially-addressable synthesis techniques (U.S. Pat. No. 5,143,854). In addition, Fodor et al. have developed automated techniques for performing light-directed, spatially-addressable synthesis techniques, photosensitive protecting groups, masking techniques and methods for gathering fluorescence intensity data (Fodor et al., PCT Publication No. WO 92/10092).
Using these various methods of combinatorial synthesis, arrays containing thousands or millions of different organic elements can be formed (U.S. Pat. No. 5,424,186). The solid phase synthesis techniques currently being used to prepare such libraries involve a stepwise process (i.e., sequential, coupling of building blocks to form the compounds of interest). In the Pirrung et al. method, for example, polypeptide arrays are synthesized on a base material by attaching photoremovable groups to the surface of the base material, exposing selected regions of the base material to light to activate those regions, attaching an amino acid monomer with a photoremovable group to the activated region, and repeating the steps of activation and attachment until polypeptides of the desired length and sequences are synthesized. The Pirrung et al. method is a sequential, step-wise process utilizing attachment, masking, deprotecting, attachment, etc. Such techniques have been used to generate libraries of biological polymers and small organic molecules to screen for their ability to specifically bind and block biological receptors (i.e., protein, DNA, etc.). These solid phase synthesis techniques, which involve the sequential addition of building blocks (i.e., monomers, amino acids) to form the compounds of interest, cannot readily be used to prepare many inorganic and organic compounds. As a result of their relationship to semiconductor fabrication techniques, these methods have come to be referred to as “Very Large Scale Immobilized Polymer Synthesis,” or “VLSIPS” technology. Robotics are used to mix and process hundreds or thousands of samples simultaneously, allowing for parallel testing of material mixtures for efficacy.
More recently combinatorial techniques have been applied to inorganic materials in the form of thin films deposited or evaporated onto a substrate. For example, Schultz et al. applied combinatorial chemistry techniques to the field of material science in U.S. Pat. No. 5,985,356. More particularly, Schultz et al. disclosed methods and apparatus for the preparation and use of a substrate having thereon an array of diverse materials in predefined regions. An appropriate array of materials is generally prepared by delivering components of materials to predefined regions on the substrate and simultaneously reacting the reactants to form different materials. While these films have known composition, the particle size and porosity of the material make it highly scattering and non-transparent.
A luminescent material absorbs energy in one portion of the electromagnetic spectrum and emits energy in another portion of the electromagnetic spectrum. A luminescent material in powder form, where the material is excited by UV light to generate photons is commonly called a phosphor, while a luminescent material in the form of a transparent solid body that is excited by gamma or X-rays to generate visible photons is commonly called a scintillator.
Most useful phosphors emit radiation in the visible portion of the spectrum in response to the absorption of the radiation which is outside the visible portion of the spectrum. Thus, the phosphor performs the function of converting electromagnetic radiation to which the human eye is not sensitive into electromagnetic radiation to which the human eye is sensitive. Most phosphors are responsive to more energetic portions of the electromagnetic spectrum than the visible portion of the spectrum. Thus, there are powder phosphors which are responsive to ultraviolet light (as in fluorescent lamps), electrons (as in cathode ray tubes) and x-rays (as in radiography).
There are a number of known scintillators each of which has its own set of properties such as the turn-on delay, efficiency, primary decay time, afterglow, hysteresis, luminescent spectrum, radiation damage and so forth. The turn-on delay of a luminescent material is the time period between the initial impingement of stimulating radiation on the luminescent material and the luminescent output reaching its maximum value, for a constant intensity of stimulating radiation. The efficiency of a luminescent material is the percentage of the energy of the absorbed stimulating radiation which is emitted as luminescent light. When the stimulating radiation is terminated, the luminescent output from a scintillator decreases in two stages. The first of these stages is a rapid decay from the full luminescent output to a low, but normally non-zero, value at which the slope of the decay changes to a substantially slower decay rate. This low intensity, normally long decay time luminescence, is known as afterglow and usually occurs with intensity values less than 2% of the full intensity value. The initial, rapid decay is known as the primary decay or primary speed and is measured from the time at which the stimulating radiation ceases to the time at which the luminescent output falls to 1/e of its full intensity value.
A luminescent material exhibits hysteresis if the amount of luminescent light output for a given amount of incident stimulating radiation depends upon the amount of stimulating radiation which has been recently absorbed by the luminescent material. The luminescent spectrum of a luminescent material is the spectral characteristics of the luminescent light which is emitted by that material.
Radiation damage is the characteristic of a luminescent material in which the quantity of light emitted by the luminescent material in response to a given intensity of stimulating radiation changes after the material has been exposed to a high radiation dose. Radiation damage may be measured by first stimulating a luminescent material with a known, standard or reference, intensity of radiation. The initial output (I
o
) of the photodetector in response to this reference intensity of incident stimulating radiation is measured and recorded or stored. Next, the luminescent material is exposed to a high dosage of radiation. Finally, the luminescent material is immediately again exposed to the reference intensity of stimulating radiation and the final output (I
f
) of its photodetector, in response to this reference intensity of stimulating radiation, is measured and stored or recorded. The radiation damage (RD) may then be expressed as:
RD
=
I
f
-
I
o
I
o
Ideally, the radiation damage should be as small as possible. In most luminescent materials, it is a negative number because it is normally less than I
o
.
In a computed tomography (CT) scanning system, an x-ray source and an x-ray detector array are positioned on opposite sides of the subject and rotated around the subject in fixed relation to each other. CT scanners with solid scintillators are known in the art. In a solid scintillator system, the scintillator material of a cell or element absorbs x-rays incident on that cell and emits light which is collected by a photodetector for that cell. During data collection, each cell or element of the detector array provides an output signal representative of the present light intensity in that cell of the array. These output signals are processed to create an image of the subject in a manner which is well known in the CT scanner a
Duclos Steven Jude
Greskovich Charles David
Johnson Noreen C.
Stafira Michael P.
Vo Toan P.
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