Method of providing digital image in radiographic film having visually adaptive contrast

#This invention is directed to a method for providing digitized radiographic images using a radiographic film that can be directly viewed or further manipulated using digitization. In addition, the radiographic film used in this invention also has what is known as “visually adaptive contrast” because it can provide higher contrast than normal in the higher density regions of an image.

#Over one hundred years ago, W. C. Roentgen discovered X-radiation by the inadvertent exposure of a silver halide photographic element. In 1913, Eastman Kodak Company introduced its first product specifically intended to be exposed by X-radiation (X-rays). Today, radiographic silver halide films account for the overwhelming majority of medical diagnostic images. Such films provide viewable black-and-white images upon imagewise exposure followed by processing with the suitable wet developing and fixing photochemicals.

#In medical radiography an image of a patient's anatomy is produced by exposing the patient to X-rays and recording the pattern of penetrating X-radiation using a radiographic film containing at least one radiation-sensitive silver halide emulsion layer coated on a transparent support. X-radiation can be directly recorded by the emulsion layer where only low levels of exposure are required. Because of the potential harm of exposure to the patient, an efficient approach to reducing patient exposure is to employ one or more phosphor-containing intensifying screens in combination with the radiographic film (usually both in the front and back of the film). An intensifying screen absorbs X-rays and emits longer wavelength electromagnetic radiation that the silver halide emulsions more readily absorb.

#FIG. 1 is graphical representation of characteristic density vs. log E (exposure) for Films A, B and C of the Example described below.

#FIG. 2 is a graphical representation of gamma (contrast) vs. log E (exposure) for Films A, B and C of the Example described below.

#The term “contrast” as herein employed indicates the average contrast (also referred to as γ) derived from a characteristic curve of a radiographic element using as a first reference point (1) a density (D1) of 0.25 above minimum density and as a second reference point (2) a density (D2) of 2.0 above minimum density, where contrast is ΔD (i.e. 1.75)÷Δ log10E (log10E2−log10E1), E1 and E2 being the exposure levels at the reference points (1) and (2).

#“Lower scale contrast” is the slope of the characteristic curve measured between of a density of 0.85 to the density achieved by shifting −0.3 log E units.

#“Upper scale contrast” is the slope of the characteristic curve measured between a density of 1.5 above Dmin to 2.85 above Dmin.