Radiation imagery chemistry: process – composition – or product th – Luminescent imaging
Reexamination Certificate
2003-06-30
2004-05-11
Schilling, Richard L. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Luminescent imaging
C430S264000, C430S966000
Reexamination Certificate
active
06733947
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to radiographic elements containing radiation-sensitive silver halide grains intended to be exposed by an intensifying screen hit by X-rays. More particularly the said film material is a mammographic film material having a well-defined characteristic curve after rapid processing.
BACKGROUND OF THE INVENTION
The incidence of breast cancer carcinoma among women continues to increase, posing a serious health problem throughout the world. The mortality rate from breast cancer can be decreased significantly by early detection using the radiological mammography technique. With this technique the compressed breast is irradiated with soft X-rays emitted from an X-ray generating device and the modulated X-rays are detected with a radiographic X-ray conversion screen, also called intensifying screen, fluorescent screen or phosphor screen. The X-ray conversion screen comprises a luminescent phosphor which converts the absorbed X-rays into visible light and the emitted visible light exposes a silver halide film that is brought into contact with said X-ray conversion screen. After film processing, comprising the steps of developing, fixing, rinsing and drying, a mammogram is obtained which can be read on a light box.
No other field of medical radiology demands such a high level of image quality as mammography and the ability of the mammogram to portray relevant diagnostic information is highly determined by the image quality of the screen-film system. Image quality is manifested by a number of features in the image including sharpness, noise, contrast, silver image colour and skin line perceptibility. It is common practice to set the amount of X-ray exposure so that the tissues on the inside of the breast are depicted at medium optical density values, i.e. in the optical density range from Dmin+1.0 to Dmin+2.5 (Dmin being defined as the base+fog density obtained after processing the unexposed film), and the diagnostic perceptibility of small, potentially malignant lesions in these tissues is highly determined by the contrast of the mammography film within said density range. A quantitative measure of the film contrast is the so-called average gradation, defined as the slope of the line drawn by connecting both points of the sensitometric curve of optical density vs. logarithmic exposure at which the optical density is equal to Dmin+1.0 and Dmin+2.5.
Conventional mammography films can roughly be classified in low and high contrast types according to the value of their average gradation as defined above. The low contrast type can be characterized by a relatively low average gradation ranging from 2.0 to 2.5 whereas the average gradation of the high contrast type may range from 3.0 to 3.5. Often, high contrast films are preferred because of the higher ability to detect tiny cancers deep in the glandular tissue of the breast. If the contrast is too high, however, it may preclude visualisation of both thin (i.e. the skin line) and thick tissues (i.e. the inside of the breast) in the same image due to lack of exposure latitude. Therefore, some radiologists prefer low contrast mammography films. When the contrast is low, skin line perceptibility is excellent, but then the chance of missing possibly malignant breast lesions is high. Thus a balance has to be found between contrast and exposure latitude and an example of this approach is described in U.S. Pat. No. 5,290,665.
In order to extend the exposure latitude some manufacturers have introduced high contrast mammography films characterized by a higher maximum density (hereinafter referred to as Dmax) than conventional high contrast films, e.g. a Dmax equal to at least 3.7, preferably even higher than 4.0. However, a film characterized by a higher Dmax is only a minor improvement with regard to better skin line perceptibility, since the background density is too high for the skin line to be clearly visible. Indeed at optical density values above 3.5, the local gradient, i.e. the slope of the sensitometric curve must be very high in order to guarantee a reasonable perceptibility as described in the classic article ‘Determination of optimum film density range for röntgenograms from visual effect’ by H. Kanamori (Acta Radiol. Diagn. Vol.4, p. 463, 1966). Nevertheless, mammography films with a higher Dmax are appreciated by a growing number of radiologists because of the wider dynamic range, i.e. the density range Dmax-Dmin of the mammogram. An important progress has been brought about with respect to perceptibility of the skin line in U.S. Pat. No. 5,965,318 but attaining a perfect balance of the characteristic curve after processing between contrast in the low densities (in order to avoid steeping up of said contrast) and contrast in the high densities (in order to avoid flattening of that contrast) remains an ever lasting demand.
As is known from graphic art materials nucleating agents provide ability to get hard dots and high contrasts in line materials, known as the commonly termed “lith quality” in processing cycles wherein the traditional “lith developers” are characterized by the presence of hydroquinone as the sole developing agent and a low but critical sulphite ions content which gives rise to an infectious development mechanism, as was described by Yule in The Journal of the Franklin Institute, Vol. 239, p. 221-223, (1945). In more recent times so-called “hard dot Rapid Access” developers were introduced on the market which combine a good stability with a “lith quality” in the reproduction of lines and screen dots, wherein examples of such developers and corresponding appropriate photographic materials include the GRANDEX system, marketed by FUJI PHOTO ltd., AGFASTAR, marketed by AGFA-GEVAERT N.V. and the ULTRATEC system, marketed by EASTMAN KODAK Co. Some of these systems make use of the contrast promoting action, induced by a nucleating mechanism, of hydrazine derivatives known for long time in the photographic art. As described in U.S. Pat. No. 4,650,746, use of a hydrazine compound permits use of an auxiliary development agent in combination with the hydroquinone type of developing agent so that the development capacity can be increased. It also permits the presence of a relatively high sulphite concentration in order to protect the developer against aerial oxidation, thus prolonging its effective working life.
A practical, early recognized problem with hydrazine compounds was caused by the high pH levels needed for the developers containing said hydrazine compounds or used with photographic elements containing these compounds in order to get the maximum effect on contrast. The teaching of Nothnagle in U.S. Pat. No. 4,269,929 provided a solution for this problem: a method for high contrast development was disclosed involving a hydrazine compound, either in the photographic element or in the developer, said developer further containing a hydroquinone developing agent, a 3-pyrazolidinone developing agent, sulphite ions, and a “contrast-promoting amount” of an amino compound and in a preferred embodiment the hydrazine compound was incorporated in the photographic material. This particular combination of ingredients allowing use of a rather moderate alkaline pH for the developing solution while retaining the desired high contrast, high developing capacity and long effective life of the developer was intensively worked out further in the context of graphic applications, inclusive for materials for micrography, but was never applied in radiographic diagnostic materials as e.g. mammography. Intense research in the context of graphic applications has, more particularly conducted to specific new hydrazide derivatives and an important technological breakthrough has been realized by the development and use of sulphonamido-arylhydrazides as disclosed in EP-A 0 286 840 and U.S. Pat. No. 5,104,769, which proved to be a very reactive and effective type.
Another main progress was the use of hydrazides, especially sulphonamido-arylhydrazides in combination with so-called “incorpor
Callant Paul
De Bie Leo
den Zegel Marc Van
Joly Ludo
Loccufier Johan
Agfa-Gevaert
Guy Joesph T.
Nexsen Pruet , LLC
Schilling Richard L.
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