Radiation imagery chemistry: process – composition – or product th – Luminescent imaging
Reexamination Certificate
2003-05-29
2004-02-03
Schilling, Richard L. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Luminescent imaging
C430S434000, C430S502000, C430S567000, C430S569000, C430S642000, C430S966000, C430S967000
Reexamination Certificate
active
06686119
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 higher contrast and that have improved processing characteristics. 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 (Dickerson et al.), U.S. Pat. No. 4,900,652 (Dickerson et al.), U.S. Pat. No. 5,252,442 (Tsaur et al.), and Research Disclosure, Vol. 184, Aug. 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. Those films generally contain high silver coverage in the form of grains having cubic or other 3-dimensional morphology. However, the higher silver coverage contributes to longer processing times.
In addition, the silver halide emulsions in such films are generally “internally fogged” meaning that the emulsion grains have internal latent image sensitivity. Such emulsions, when coated in combination with high silver iodide emulsions sufficient to release iodide upon development to render the internally fogged emulsion developable, results in higher covering power than would be possible with the silver iodide emulsions. This property can provide the advantage of lower silver coverage and improved processing compared to higher silver containing films, but it is also disadvantageous in that if the developer is contaminated with photographic fixers from the fixing tank, the internally fogged emulsion is developer prematurely and provided high fogging (D
min
).
There is a desire in the industry to have “blue-sensitive” or “blue-light sensitive” radiographic films that have reduced silver coverage and improved processability without significant loss of desired sensitometric properties. In addition, it is desired to avoid the use of internally fogged emulsion because of the various disadvantages with their use.
SUMMARY OF THE INVENTION
The present invention provides a blue-sensitive, 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 predominantly tabular silver halide grains that have an aspect ratio of from 8 to 14.5, a grain thickness of from about 0.15 to about 0.3 &mgr;m, and that comprise at least 90 mol % bromide and up to 6 mol % iodide, based on total silver halide,
wherein the 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 blue-sensitive, radiographic silver halide film of this invention comprises 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 predominantly tabular silver halide grains that have an aspect ratio of from about 12 to about 14, a grain thickness of from about 0.16 to about 0.19 &mgr;m, and comprising at least 95 mol % bromide and from about 0.9 to about 3 mol % iodide, based on total silver halide in each of the emulsion layers, said iodide being distributed uniformly throughout the grains,
wherein the tabular silver halide grains in the first and second silver halide emulsion layers are dispersed in a hydrophilic polymeric vehicle mixture comprising from about 0.8% to about 1.2% of deionized oxidized gelatin, based on the total dry weight of the polymeric vehicle mixture.
This invention also provides a radiographic imaging assembly comprising:
A) the blue-sensitive, radiographic silver halide film of this invention as described herein, and
B) a fluorescent intensifying screen that comprises an inorganic phosphor capable of absorbing X-rays and emitting electromagnetic radiation having a wavelength of from about 360 to about 540 nm, the inorganic phosphor being coated in admixture with a polymeric binder in a phosphor layer onto a flexible support and having a protective overcoat disposed over the phosphor layer.
Further, this invention provides a method of providing a black-and-white image comprising exposing the radiographic imaging assembly of this invention, and processing the blue-sensitive radiographic silver halide film, sequentially, with a black-and-white developing composition and a fixing composition, the processing being carried out within 90 seconds, dry-to-dry.
In addition, a method of providing a black-and-white image comprises exposing the blue-sensitive, radiographic silver halide film of this invention, and processing the blue-sensitive radiographic silver halide film, sequentially, with a black-and-white developing composition and a fixing composition, the processing being carried out within 90 seconds, dry-to-dry.
The present invention provides an improved blue-sensitive, radiographic film with relatively lower silver coverage than known films and improved contrast and processability without loss in other sensitometric properties such as speed and maximum density. These films can be used to provide black-and-white images useful for medical diagnosis.
These advantages are achieved by a combination of proper
Mroczek Susan K.
Pavlik Mark P.
Pepe Joseph P.
Eastman Kodak Company
Schilling Richard L.
Tucker J. Lanny
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