Radiation imagery chemistry: process – composition – or product th – Luminescent imaging
Reexamination Certificate
2003-03-26
2004-02-03
Schilling, Richard L. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Luminescent imaging
C430S434000, C430S502000, C430S503000, C430S567000, C430S569000, C430S642000, C430S966000, C430S967000
Reexamination Certificate
active
06686117
ABSTRACT:
FIELD OF THE INVENTION
This invention is directed to radiography. In particular, it is directed to blue light-sensitive, radiographic silver halide films that provide improved medical diagnostic images with reduced yellow stain. This invention also provides an imaging assembly and a method of radiographic imaging using these improved radiographic films.
BACKGROUND OF THE INVENTION
The use of radiation-sensitive silver halide emulsions for medical diagnostic imaging can be traced to Roentgen's discovery of X-radiation by the inadvertent exposure of a silver halide film. Eastman Kodak Company then introduced its first product specifically that was intended to be exposed by X-radiation in 1913. The discovery of X-rays in 1895 provided the beginning of a new way of providing medical evaluation and diagnosis. Prior to that time, medical examination comprised predominantly manual probing and consideration of symptoms. Such examinations would obviously be incomplete and inconclusive in most instances, and incorrect in some instances. In some cultures, there was a prohibition of touching the female anatomy, further limiting the effectiveness of medical examination. Thus, the discovery that X-radiation could pass through the body with relatively little harm and provide useful images provided a powerful tool in medical diagnosis and treatment.
In conventional medical diagnostic imaging the object is to obtain an image of a patient's internal anatomy with as little X-radiation exposure as possible. The fastest imaging speeds are realized by mounting a dual-coated radiographic element between a pair of fluorescent intensifying screens for imagewise exposure. About 5% or less of the exposing X-radiation passing through the patient is adsorbed directly by the latent image forming silver halide emulsion layers within the dual-coated radiographic element. Most of the X-radiation that participates in image formation is absorbed by phosphor particles within the fluorescent screens. This stimulates light emission that is more readily absorbed by the silver halide emulsion layers of the radiographic element.
Examples of radiographic element constructions for medical diagnostic purposes are provided by U.S. Pat. No. 4,425,425 (Abbott et al.) and U.S. Pat. No. 4,425,426 (Abbott et al.), U.S. Pat. No. 4,414,310 (Dickerson), U.S. Pat. No. 4,803,150 (Kelly et al.), U.S. Pat. No. 4,900,652 (Kelly et al.), U.S. Pat. No. 5,252,442 (Tsaur et al.), and Research Disclosure, Vol. 184, August 1979, Item 18431.
Problem to be Solved
Some commercial radiographic films that are available from Eastman Kodak Company and Agfa-Gevaert are sensitive to blue light and designed to be used in combination with blue-emitting fluorescent intensifying screens such as those containing calcium tungstate as the phosphor.
In order to match the spectral sensitivity of calcium tungstate screens, radiographic films must be blue-light sensitive. One way to achieve this is to use spectral sensitizing dyes for the silver halide grains that absorb in the blue region of the electromagnetic spectrum. Unfortunately, some of the spectral sensitizing dyes used for this purpose leave an undesirable “yellow” stain following wet processing.
There is a desire in the industry to have “blue-sensitive” or “blue-light sensitive” radiographic films that have reduced dye stain without significant loss of desired sensitometric properties.
SUMMARY OF THE INVENTION
This invention provides a radiographic silver halide film comprising a support having first and second major surfaces,
the radiographic silver halide film having disposed on the first major support surface, one or more hydrophilic colloid layers including a first silver halide emulsion layer, and on the second major support surface, one or more hydrophilic colloid layers including a second silver halide emulsion layer,
the first silver halide emulsion layer comprising a blend of silver halide grains, the blend comprising:
blue-sensitive tabular silver halide grains that have an aspect ratio of at least 15, a grain thickness of at least 0.1 &mgr;m, and comprise at least 90 mol % bromide and up to 4 mol % iodide, based on total silver halide, substantially all of said iodide being present in an internal localized portion of the blue-sensitive tabular silver halide grains that excludes the surface of the blue-sensitive tabular silver halide grains, and
green-sensitive tabular silver halide grains that have an aspect ratio of at least 20, a grain thickness of at least 0.07 &mgr;m, and comprise at least 90 mol % bromide, up to 1.5 mol % chloride, and up to 1.5 mol % iodide, based on total silver halide,
wherein the molar ratio of silver in the blue-sensitive tabular silver halide grains to the silver in the green-sensitive tabular silver halide grains is from about 2:1 to about 6:1,
wherein the blue-sensitive and green-sensitive tabular silver halide grains in the first silver halide emulsion layer are dispersed in a hydrophilic polymeric vehicle mixture comprising at least 0.5% of oxidized gelatin, based on the total dry weight of the polymeric vehicle mixture.
In preferred embodiments, the radiographic silver halide films of the invention include a second silver halide emulsion layer that comprise blue-sensitive tabular silver halide grains that have an aspect ratio of at least 15, a grain thickness of at least 0.1 &mgr;m, and comprise at least 90 mol % bromide and up to 4 mol % iodide, based on total silver halide, substantially all of the iodide being present in an internal localized portion of the blue-sensitive tabular silver halide grains that excludes the surface of the blue-sensitive tabular silver halide grains, wherein the blue-sensitive tabular silver halide grains in the second silver halide emulsion layer are dispersed in a hydrophilic polymeric vehicle mixture comprising at least 0.5% of oxidized gelatin, based on the total dry weight of the polymeric vehicle mixture.
In still other preferred embodiments, the second silver halide emulsion layer comprises a blend of silver halide grains, the blend comprising:
blue-sensitive tabular silver halide grains that have an aspect ratio of at least 15, a grain thickness of at least 0.1 &mgr;m, and comprise at least 90 mol % bromide and up to 4 mol % iodide, based on total silver halide, substantially all of the iodide being present in an internal localized portion of the blue-sensitive tabular silver halide grains that excludes the surface of the blue-sensitive tabular silver halide grains, and
green-sensitive tabular silver halide grains that have an aspect ratio of at least 20, a grain thickness of at least 0.07 &mgr;m, and comprise at least 90 mol % bromide, up to 1.5 mol% chloride, and up to 1.5 mol % iodide, based on total silver halide,
wherein the molar ratio of silver in the blue-sensitive tabular silver halide grains to the silver in the green-sensitive tabular silver halide grains is from about 2:1 to about 6:1,
wherein the blue-sensitive and green-sensitive tabular silver halide grains in the second silver halide emulsion layer are dispersed in a hydrophilic polymeric vehicle mixture comprising at least 0.5% of oxidized gelatin, based on the total dry weight of the polymeric vehicle mixture.
In most preferred embodiments of the present invention, a radiographic silver halide film comprising a support having first and second major surfaces,
the radiographic silver halide film having disposed on the first major support surface, one or more hydrophilic colloid layers including a first silver halide emulsion layer, and on the second major support surface, one or more hydrophilic colloid layers including a second silver halide emulsion layer,
the first and second silver halide emulsion layers having essentially the same composition and comprising a blend of silver halide grains, the blend comprising:
blue-sensitive tabular silver halide grains that have an aspect ratio of from about 20 to about 30, a grain thickness of from about 0.10 to about 0.14 &mgr;m, and comprising at least 95 mol % bromide and from about 1 to about 3.5
Davis Richard F.
Dickerson Robert E.
Eastman Kodak Company
Schilling Richard L.
Tucker J. Lanny
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