EP0611226A1 - Eléments radiographiques peu sensibles aux expositions parasites à travers le support adaptés pour l'enregistrement d'une image de la chair et des os - Google Patents

Eléments radiographiques peu sensibles aux expositions parasites à travers le support adaptés pour l'enregistrement d'une image de la chair et des os Download PDF

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Publication number
EP0611226A1
EP0611226A1 EP94420028A EP94420028A EP0611226A1 EP 0611226 A1 EP0611226 A1 EP 0611226A1 EP 94420028 A EP94420028 A EP 94420028A EP 94420028 A EP94420028 A EP 94420028A EP 0611226 A1 EP0611226 A1 EP 0611226A1
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Prior art keywords
silver halide
halide emulsion
emulsion layer
crossover
layer unit
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EP94420028A
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German (de)
English (en)
Inventor
Robert Edward C/O Eastman Kodak Co. Dickerson
Phillip Carter C/O Eastman Kodak Co. Bunch
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Eastman Kodak Co
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Eastman Kodak Co
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Publication of EP0611226A1 publication Critical patent/EP0611226A1/fr
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
    • G03C5/00—Photographic processes or agents therefor; Regeneration of such processing agents
    • G03C5/16—X-ray, infrared, or ultraviolet ray processes
    • G03C5/17—X-ray, infrared, or ultraviolet ray processes using screens to intensify X-ray images
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
    • G03C2200/00—Details
    • G03C2200/58—Sensitometric characteristics

Definitions

  • the invention relates to radiographic imaging. More specifically, the invention relates to double coated silver halide radiographic elements of the type employed in combination with intensifying screens.
  • double coated as applied to a radiographic element means that emulsion layer units are coated on each of the two opposite sides of the support.
  • low crossover as applied to double coated radiographic elements indicates a crossover of less than 10% within the wavelength range of imaging and when measured as more fully described below.
  • sensitometrically symmetric means that the emulsion layer units on opposite sides of a double coated radiographic element produce identical characteristic curves when identically exposed.
  • sensitometrically asymmetric means that the emulsion layer units on opposite sides of a double coated radiographic element produce significantly different characteristic curves when identically exposed.
  • an image of a patient's tissue and bone structure is produced by exposing the patient to X-radiation and recording the pattern of penetrating X-radiation using a radiographic element containing at least one radiation-sensitive silver halide emulsion layer coated on a transparent (usually blue tinted) film support.
  • the X-radiation can be directly recorded by the emulsion layer where only limited areas of exposure are required, as in dental imaging and the imaging of body extremities.
  • a more efficient approach which greatly reduces X-radiation exposures, is to employ an intensifying screen in combination with the radiographic element.
  • the intensifying screen absorbs X-radiation and emits longer wavelength electromagnetic radiation which silver halide emulsions more readily absorb.
  • Another technique for reducing patient exposure is to coat two silver halide emulsion layers on opposite sides of the film support to form a "double coated" radiographic element.
  • Diagnostic needs can be satisfied at the lowest patient X-radiation exposure levels by employing a double coated radiographic element in combination with a pair of intensifying screens.
  • the silver halide emulsion layer unit on each side of the support directly absorbs 1 to 2 percent of incident X-radiation.
  • the front screen, the screen nearest the X-radiation source absorbs a much higher percentage of X-radiation, but still transmits sufficient X-radiation to expose the back screen, the screen farthest from the X-radiation source.
  • An imagewise exposed double coated radiographic element contains a latent image in each of the two silver halide emulsion units on opposite sides of the film support. Processing converts the latent images to silver images and concurrently fixes out undeveloped silver halide, rendering the film light insensitive. When the film is mounted on a view box, the two superimposed silver images on opposite sides of the support are seen as a single image against a white, illuminated background.
  • An art recognized difficulty with employing double coated radiographic elements in combination with intensifying screens as described above is that some light emitted by each screen passes through the transparent film support to expose the silver halide emulsion layer unit on the opposite side of the support to light.
  • the light emitted by a screen that exposes the emulsion layer unit on the opposite side of the support reduces image sharpness. The effect is referred to in the art as crossover.
  • US-A-4,997,750 discloses low crossover double coated radiographic elements in which the emulsion layer units on opposite sides of the support differ in speed.
  • US-A-4,994,355 discloses low crossover double coated radiographic elements in which the emulsion layer units on opposite sides of the support differ in contrast.
  • US-A-5,021,327 discloses low crossover double coated radiographic elements in combination with a pair of intensifying screens, where the back emulsion layer unit-intensifying screen combination exhibits a photicity twice that of the front emulsion layer unit-intensifying screen combination, where photicity is the product of screen emission and emulsion layer unit sensitivity.
  • Dickerson and Bunch I and II as well as Bunch and Dickerson disclose a low crossover double coated radiographic element having a fast low contrast emulsion layer unit on one side of the support and a slow high contrast emulsion layer unit on the opposite side of the support.
  • Jebo and others Statutory Invention Registration H1105 discloses low crossover double coated radiographic elements with emulsion layer units on opposite sides of the support that differ in sensitometric properties. A feature is included for ascertaining which of the emulsion layer units is positioned nearest a source of X-radiation during exposure.
  • US-A-5,108,881 discloses a low crossover radiographic element in which a faster silver halide emulsion layer unit coated on one side of the support exhibits a lower contrast that an slower silver halide emulsion layer unit coated on the opposite side of the support.
  • Radiographic elements that produce higher contrast images at lower densities and lower contrast images at higher densities are disclosed by Suzuki and others published European Patent Application 0 126 644 and Belgian Patent 530,129. Suzuki and others blended emulsions to achieve this result while the Belgian Patent suggests coating higher and lower contrast emulsions on the opposite sides of a support.
  • Figure 1 is a schematic diagram of an assembly consisting of a low crossover radiographic element sandwiched between two intensifying screens.
  • Figure 2 illustrates the overall sensitometric characteristic curve of a conventional sensitometrically symmetric double coated radiographic element and the characteristic curve of each of two identical individual emulsion layer units forming the radiographic element.
  • Figure 3 illustrates the overall sensitometric characteristic curve of a sensitometrically asymmetric low crossover double coated radiographic element according to the invention and the characteristic curves of the individual emulsion layer units as positioned by their screen exposures.
  • Figure 4 illustrates the overall and individual emulsion layer unit characteristic curves of an example radiographic element according to the invention.
  • the characteristic curves of Figures 2 and 3 have been drawn to conform to an ideal configuration. Ignoring superscripts, which are employed to distinguish one curve from another, the points A, B, C and D indicate corresponding reference points in the curves.
  • A is the point beyond which additional exposure results in an increase in density--that is, A is the highest exposure level consistent with obtaining minimum density (Dmin).
  • the curve segment A-B is in each instance the toe of the characteristic curve. In the toe of a characteristic curve incremental increases in density become larger with each incremental increase in the logarithm of exposure.
  • the curve segments B-C are shown as linear--that is, as regions in which each incremental increase in the logarithm of exposure produces a corresponding incremental increase in density.
  • flesh soft tissue surrounding the bones in a radiographic image. Achieving both bone and flesh imaging in a single radiograph is difficult if not impossible using conventional radiographic elements. The reason is that when film exposure has been optimized for bone imaging the film is receiving 0.6 log E (subject to some patient to patient variation) more exposure in areas in which the exposing X-radiation has penetrated only flesh. Given the requirement of relatively sharp images for bone feature definition, contrast levels are too high to provide film exposure latitude sufficient to capture both bone and flesh features in a single image.
  • the present invention has as its purpose to provide radiographic elements that exhibit the sharp imaging advantages of low crossover radiographic elements, allowing optimum sharp imaging of bone tissue while at the same time obtaining functionally serviceable images of surrounding flesh.
  • this invention is directed to a radiographic element comprised of a transparent film support, first and second silver halide emulsion layer units coated on opposite sides of the film support, and means for reducing to less than 10 percent crossover of electromagnetic radiation of wavelengths longer than 300 nm capable of forming a latent image in the silver halide emulsion layer units, the crossover reducing means being decolorized in less than 30 seconds during processing of the emulsion layer units.
  • the radiographic element is characterized in that, at a density of 1.0, the first silver halide emulsion layer unit exhibits a speed exceeding by from 0.3 to 1.0 log E that of the second silver halide emulsion layer unit, the first silver halide emulsion layer unit exhibiting a contrast in the range of from 2.0 to 4.0, and the second silver halide emulsion layer unit exhibiting a contrast in the range of from 0.5 to 1.7.
  • the present invention constitutes an improvement over low crossover double coated radiographic elements, such as, for example, those disclosed by Dickerson and others I and II, the disclosures of which are here incorporated by reference.
  • the advantages of the present invention are that in addition to improved image sharpness attributable to low crossover the radiographic elements are also capable of producing both sharp images of bone and useful images of surrounding soft tissue (that is, flesh) exhibiting a much lower capability of attenuating X-radiation.
  • the invention is directed to an imaging assembly as claimed in Claim 7.
  • a low crossover double coated radiographic element 100 is positioned between a pair of light emitting intensifying screens 201 and 202.
  • the radiographic element support is comprised of a transparent radiographic support element 101, typically blue tinted, capable of transmitting light to which it is exposed and, optionally, similarly transmissive subbing units 103 and 105.
  • On the first and second opposed major faces 107 and 109 of the support formed by the subbing units are crossover reducing hydrophilic colloid layers 111 and 113, respectively.
  • Overlying the crossover reducing layers 111 and 113 are light recording latent image forming silver halide emulsion layer units 115 and 117, respectively.
  • Each of the emulsion layer units is formed of one or more hydrophilic colloid layers including at least one silver halide emulsion layer. Overlying the emulsion layer units 115 and 117 are optional hydrophilic colloid protective overcoat layers 119 and 121, respectively. All of the hydrophilic colloid layers are permeable to processing solutions.
  • the assembly is imagewise exposed to X-radiation.
  • the X radiation is principally absorbed by the intensifying screens 201 and 202, which promptly emit light as a direct function of X-ray exposure.
  • the intensifying screens 201 and 202 which promptly emit light as a direct function of X-ray exposure.
  • the light recording latent image forming emulsion layer unit 115 is positioned adjacent this screen to receive the light which it emits. Because of the proximity of the screen 201 to the emulsion layer unit 115 only minimal light scattering occurs before latent image forming absorption occurs in this layer unit. Hence light emission from screen 201 forms a sharp image in emulsion layer unit 115.
  • crossover reducing layers 111 and 113 are interposed between the screen 201 and the remote emulsion layer unit and are capable of intercepting and attenuating this remaining light. Both of these layers thereby contribute to reducing crossover exposure of emulsion layer unit 117 by the screen 201.
  • the screen 202 produces a sharp image in emulsion layer unit 117, and the light absorbing layers 111 and 113 similarly reduce crossover exposure of the emulsion layer unit 115 by the screen 202.
  • the radiographic element 100 is removed from association with the intensifying screens 210 and 202 and processed in a rapid access processor--that is, a processor, such as an RP-X-Omat TM processor, which is capable of producing a image bearing radiographic element dry to the touch in less than 90 seconds.
  • a rapid access processor such as an RP-X-Omat TM processor, which is capable of producing a image bearing radiographic element dry to the touch in less than 90 seconds. Rapid access processors are illustrated by US-A-3,545,971 and European published patent application 248,390.
  • low crossover means reducing to less than 10 percent crossover of electromagnetic radiation of wavelengths longer than 300 nm capable of forming a latent image in the silver halide emulsion layer units.
  • low crossover is achieved in part by absorption of light within the emulsion layer units and in part by the layers 111 and 113, which serve as crossover reducing means.
  • the crossover reducing means In addition to having the capability of absorbing longer wavelength radiation during imagewise exposure of the emulsion layer units the crossover reducing means must also have the capability of being decolorized in less than 90 seconds during processing, so that no visual hindrance is presented to viewing the superimposed silver images.
  • the crossover reducing means decreases crossover to less than 10 percent, preferably reduces crossover to less than 5 percent, and optimally less than 3 percent.
  • the crossover percent being referred to also includes "false crossover", apparent crossover that is actually the product of direct X-radiation absorption. That is, even when crossover of longer wavelength radiation is entirely eliminated, measured crossover will still be in the range of 1 to 2 percent, attributable to the X-radiation that is directly absorbed by the emulsion farthest from the intensifying screen. Taking false crossover into account, it is apparent that any radiographic element that exhibits a measured crossover of less than 5 percent is in fact a "zero crossover” radiographic element. Crossover percentages are determined by the procedures set forth in US-A-4,425,425 and US-A-4,425,426.
  • the exposure response of an emulsion layer unit on one side of the support is influenced to only a slight extent by (that is, essentially independent of) the level of exposure of the emulsion layer on the opposite side of the support. It is therefore possible to form two independent imaging records, one emulsion layer unit recording only the emission of the front intensifying screen and the remaining emulsion layer unit recording only the emission of the back intensifying screen during imagewise exposure to X radiation.
  • radiographic elements have been constructed to produce identical sensitometric records in the two emulsion layer units on the opposite sides of the support. The reason for this is that until practical low crossover radiographic elements were made available by Dickerson and others I and II, cited above, both emulsion layer units of a double coated radiographic element received essentially similar exposures, since both emulsion layer units were simultaneously exposed by both the front and back intensifying screens.
  • a typical overall characteristic curve A-B-C-D is produced by exposing a high crossover double coated radiographic element.
  • the overall characteristic curve is the sum of two identical characteristic curves A'-B'-C'-D' produced by the individual emulsion layer units. The same individual characteristic curves are produced even when the front and back intensifying screens are varied in their emission intensities, since each emulsion layer unit is exposed by both intensifying screens and therefore receives essentially the same exposure.
  • the same overall and individual emulsion layer unit characteristic curves can be produced by substituting a low crossover sensitometrically symmetric radiographic element, such as radiographic element 100 with identical emulsion layer units 115 and 117 and with the crossover reducing layers 111 and 113 present, provided front and back intensifying screens 201 and 202 having similar light emission properties are employed.
  • a low crossover sensitometrically symmetric radiographic element such as radiographic element 100
  • identical emulsion layer units 115 and 117 and with the crossover reducing layers 111 and 113 present provided front and back intensifying screens 201 and 202 having similar light emission properties are employed.
  • a point at mid-scale between points A and C is labelled BONE and a point at mid-scale between points A' and C' is labelled BONE', indicating the optimum film exposure for bone imaging.
  • BONE represents the composite bone image produced the emulsion layer units on both sides of the support while BONE' represents the bone image produced by only one of two identical emulsion layer units on opposite sides of the support. While the same characteristic curve can be obtained using either a dual coated radiographic of either high or low crossover, the low crossover radiographic element produces a sharper BONE image, since unsharpness due to crossover has been minimized, if not eliminated.
  • a low crossover double coated radiographic element can be constructed to produce sharp bone images and useful flesh images by employing the combination of a relatively high contrast emulsion layer unit and a relatively low contrast emulsion layer unit.
  • the overall characteristic curve A T -B T -C T -D T of the radiographic element of the invention is similar to the overall characteristic curve A-B-C-D, except that point D T is not the maximum density point of the characteristic curve.
  • point D T is not the maximum density point of the characteristic curve.
  • optimum BONE exposure remains at mid-scale between points B T -C T , allowing the same sharp BONE images to be obtained as in the Figure 2 low crossover radiographic element.
  • the FLESH exposure point is now located in a portion of the characteristic curve that shows a significant contrast (that is, ⁇ D/ ⁇ E).
  • the FLESH image is in a lower contrast portion of the characteristic curve than the BONE image, the FLESH image is less sharp. From the radiologist's viewpoint this is an advantage, since sharp images also contain a large high frequency noise content that would be distracting in attempting an accurate BONE diagnosis from the image.
  • the radiologist is provided with exactly the information sought in the overwhelming majority of BONE diagnoses, a sharp BONE image and a view of surrounding FLESH that shows its general location and density, but not all of its fine detail.
  • the characteristic curve A T -B T -C T -D T is the composite of the individual characteristic curves A H -B H -C H -D H and A L -B L produced by a relatively higher contrast emulsion layer unit on one side of the support and a relatively lower contrast emulsion layer unit on the opposite side of the support of the low crossover radiographic element of the invention.
  • the characteristic curve A H -B H -C H -D H is qualitatively similar to curves A-B-C-D and A'-B'-C'-D' described above. Note that the ideal BONE H exposure level remains at mid-scale between points B H -C H , resulting in the FLESH H exposure level occurring beyond the maximum density exposure level D H .
  • the characteristic curve A L -B L is strikingly different than individual emulsion layer unit characteristic curves A'-B'-C'-D' and A H -B H -C H -D H .
  • the location of BONE L on the A L -B L characteristic curve is at a lower exposure level than point A L , indicating that insufficient exposure has been received to produce a useful BONE L image.
  • the FLESH L image lies to the right of point B L on a portion of the characteristic curve that exhibits sufficient contrast for useful imaging.
  • the A L -B L curve has not been extended to show a shoulder portion of the curve, since extended patient exposure to reach the shoulder portion of the A L -B L curve will seldom, if ever, occur.
  • the lower contrast curve makes no contribution to BONE T imaging while the higher contrast curve makes no contribution to FLESH T imaging.
  • the lower contrast curve may make some contribution to BONE T imaging, although this is not its primary imaging role, while the higher contrast curve can make some contribution to FLESH T imaging, although again this is not its primary imaging role and its contribution to FLESH T imaging will be too small to be serviceable in and of itself.
  • characteristic curve A T -B T -C T -D T capable of satisfying practical imaging requirements for most human imaging subjects it is important that certain relationships of speed and contrast be incorporated in the individual emulsion layer units of the low crossover double coated radiographic elements of the invention.
  • each curve represents a single emulsion layer unit rather than a pair of identical emulsion layer units, since this permits the contribution of each emulsion layer unit to the overall characteristic curve to be more readily visually appreciated.
  • the difference in speed of the faster and slower emulsion layer units will be in the range of from 0.3 to 1.0 log E, preferably 0.4 to 0.8 log E.
  • the faster, higher contrast emulsion layer unit is contemplated to have a contrast in the range of from 2.0 to 4.0, preferably 2.5 to 3.5 while the slower, lower contrast emulsion layer unit is contemplated to have a contrast in the range of from 0.5 to 1.7, preferably 0.7 to 1.5.
  • contrast is the slope of the characteristic curve at a reference density of 1.0 and is not an average of contrasts over a range of densities.
  • radiographic elements of this invention can take any convenient conventional form.
  • Features and details of features not specifically discussed preferably correspond to those disclosed by Dickerson and others I and II, Dickerson and Bunch I and II and Bunch and Dickerson, cited above and here incorporated by reference above.
  • This screen has a composition and structure corresponding to that of a commercial, general purpose screen. It consists of a terbium activated gadolinium oxysulfide phosphor having a median particle size of 5.9 ⁇ m coated on a white pigmented polyester support in a Permuthane TM polyurethane binder at a total phosphor coverage of 7.0 g/dm2 at a phosphor to binder ratio of 15:1.
  • This screen has a composition and structure corresponding to that of a commercial, high resolution screen. It consists of a terbium activated gadolinium oxysulfide phosphor having a median particle size of 5 ⁇ m coated on a blue tinted clear polyester support in a Permuthane TM polyurethane binder at a total phosphor coverage of 3.4 g/dm2 at a phosphor to binder ratio of 21:1 and containing 0.0015% carbon.
  • the X-radiation response of each screen was obtained using a tungsten target X-ray source in an XRD 6 TM generator.
  • the X-ray tube was operated at 70 kVp and 30 mA, and the X-radiation from the tube was filtered through 0.5 mm Cu and 1 mm Al filters before reaching the screen.
  • the emitted light was detected by a Princeton Applied Research model 1422/01 TM intensified diode array detector coupled to an Instruments SA model HR-320 TM grating spectrograph. This instrument was calibrated to within % 0.5 nm with a resolution of better than 2 nm (full width at half maximum). The intensity calibration was performed using two traceable National Bureau of Standards sources, which yielded an arbitrary intensity scale proportional to Watts/nm/cm2. The total integrated emission intensity from 250 to 700 nm was calculated on a Princeton Applied Research model 1460 OMA III TM optical multichannel analyzer by adding all data points within this region and multiplying by the bandwidth of the region.
  • the assemblies were exposed using an intensity scale X-ray sensitometer of the type described by A.G. Haus, K. Rossman, C.Vyborny, P.B. Hoffer and K. Doi, "Sensitometery in Diagnostic Radiology, Radiation Therapy, and Nuclear Medicine", J. Appl. Photog. Eng., vol. 3, pp. 114-124 (1977). Exposure conditions were as follows: 80 KVp X-radiation (constant potential), total filtration consisting of 3 mm berylium + 0.5 mm copper + 2.2 mm aluminum; 7.5 mm aluminum half-value layer; 1.5 mA, 0.11 sec exposure.
  • Optical densities are expressed in terms of diffuse density as measured by an X-rite Model 310 TM densitometer, which was calibrated to ANSI standard PH 2.19 and was traceable to a National Bureau of Standards calibration step tablet.
  • the character-istic curve (density vs. log E) was plotted for each radiographic element processed. Average contrast in each instance was determined from the characteristic curve at densities of 0.25 and 2.0 above minimum density.
  • Element EX (example) (Em.FHC) LXOA (Em.SLC)
  • Radiographic element EX was a double coated radiographic element exhibiting near zero crossover.
  • Radiographic element EX was constructed of a low crossover support composite (LXO) consisting of a blue-tinted transparent polyester film support coated on each side with a crossover reducing layer consisting of gelatin (1.6g/m2) containing 220 mg/m2 of a crossover control dye.
  • LXO low crossover support composite
  • SLC Slow low contrast
  • FHC fast high contrast
  • Both emulsions were green-sensitized high aspect ratio tabular grain silver bromide emulsions, where the term "high aspect ratio" is employed as defined by US-A-4,425,425 to require that at least 50 percent of the total grain projected area be accounted for by tabular grains having a thickness of less than 0.3 ⁇ m and having an average aspect ratio of greater than 8:1.
  • the slow low contrast emulsion was a 1:1 (silver ratio) blend of a first emulsion which exhibited an average grain diameter of 2.0 ⁇ m and an average grain thickness of 0.13 ⁇ m and a second emulsion which exhibited an average grain diameter of 1.2 ⁇ m and an average grain thickness of 0.13 ⁇ m.
  • the fast high contrast emulsion exhibited an average grain diameter of 2.4 ⁇ m and an average grain thickness of 0.12 ⁇ m.
  • the fast high contrast emulsion was monodispersed, exhibiting both thickness and diameter coefficients of variation of less than 10%.
  • Both the fast high contrast and slow low contrast emulsions were spectrally sensitized with 400 mg/Ag mol of anhydro-5,5-dichloro-9-ethyl-3,3'-bis(3-sulfopropyl)oxacarbocyanine hydroxide, followed by 300 mg/Ag mol of potassium iodide.
  • the slow low contrast emulsion was coated at a silver coverage of 1.6 g/m2 and a gelatin coverage of 3.3 g/m2.
  • the fast high contrast emulsion was coated at a silver coverage of 2.2 g/m2 and a gelatin coverage of 3.3 g/m2.
  • Protective gelatin layers (0.7 g/m2) were coated over the emulsion layers.
  • a red absorbing dye (44 mg/m2) was added to the protective overcoat of the high contrast side to provide visual identification of the respective sides under safelight conditions.
  • Each of the gelatin containing layers were hardened with bis(vinylsulfonylmethyl) ether at 1% of the total gelatin.
  • Emulsion FHC of Element EX was exposed by Screen Z employed as a front screen and Emulsion SLC was exposed by Screen Y employed as a back screen, the individual and combined characteristic curves shown in Figure 4 were obtained, where FHC designates the front screen-emulsion layer unit combination, SLC designates the back screen-emulsion layer unit combination, and EX designates the overall characteristic curve. Notice that if BONE exposure were occurring anywhere in the 1.0 to 1.4 relative log exposure range useful FLESH exposure ranges extend to 2.4 relative log exposures and beyond. Thus Element EX has the capability of obtaining sharp images of bone tissue and useful images of surrounding soft tissue.
  • the purpose of choosing the fine screen for exposure of the FHC emulsion layer unit was to obtain the highest practical image detail and sharpness in areas intended to record bone tissue while a medium screen was chosen for use with the SLC emulsion layer unit, since fine image detail of surrounding soft tissue is not sought or desired by radiologists.
  • Emulsion SLC When coated as described above, but symmetrically, with Emulsion SLC coated on both sides of the support and Emulsion FHC omitted, using a Screen Y pair, Emulsion SLC exhibits a contrast of 1.7 at an overall density of 1.0. Similarly, when Emulsion FHC is coated symmetrically with Emulsion SLC omitted, Emulsion FHC exhibits a contrast of 2.9 at an overall density of 1.0. The speed difference in the two coatings at an overall density of 1.0 is 0.7 log E.
  • control radiographic element was constructed similarly as Element EX, described above, except that the crossover control dye was omitted.
  • Element EX When the Elements C and EX were identically exposed and processed as described above, it was observed that Element EX exhibited a larger useful dynamic range of exposure and exhibited higher contrast in the density regions 1.0 to 1.4 in which bone images are viewed. When the dynamic range is taken as the difference in exposure levels between the limit of minimum bone densities (1.0) and the limit of maximum flesh densities (3.0), Element EX exhibits a 0.36 log E larger exposure range than Element C. Stated another way, with bone density exposures optimized for a particular subject it is much less likely with Element EX that flesh image features would be recorded at such high densities as to be difficult to distinguish.
  • Element C offers a restricted exposure latitude of only 0.58 log E between these limits whereas Element EX offers a much larger dynamic latitude of 0.86 log E. This means that a radiologist is much more likely to obtain both bone and flesh images at near ideal density levels using Element EX than when using Element C. Further, higher contrast bone images are obtained with Element EX.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Silver Salt Photography Or Processing Solution Therefor (AREA)
  • Apparatus For Radiation Diagnosis (AREA)
EP94420028A 1993-02-08 1994-01-31 Eléments radiographiques peu sensibles aux expositions parasites à travers le support adaptés pour l'enregistrement d'une image de la chair et des os Withdrawn EP0611226A1 (fr)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1995021403A1 (fr) * 1994-02-04 1995-08-10 Eastman Kodak Company Elements et ensembles radiographiques a surimpression minimale adaptes pour la visualisation de la chair et des os

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5108881A (en) * 1990-03-29 1992-04-28 Eastman Kodak Company Minimal crossover radiographic elements adapted for varied intensifying screen exposures
EP0530117A1 (fr) * 1991-08-16 1993-03-03 Eastman Kodak Company Eléments radiographiques peu sensibles aux expositions parasites à travers le support adapté pour l'enregistrement d'une image de la chair et des os

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5108881A (en) * 1990-03-29 1992-04-28 Eastman Kodak Company Minimal crossover radiographic elements adapted for varied intensifying screen exposures
EP0530117A1 (fr) * 1991-08-16 1993-03-03 Eastman Kodak Company Eléments radiographiques peu sensibles aux expositions parasites à travers le support adapté pour l'enregistrement d'une image de la chair et des os

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1995021403A1 (fr) * 1994-02-04 1995-08-10 Eastman Kodak Company Elements et ensembles radiographiques a surimpression minimale adaptes pour la visualisation de la chair et des os

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