X-ray image converter, device and method for recording, processing and illustrating images using X-rays and other rays

Abstract

An X-ray image converter (2) for recording and evaluating information gained from X-ray investigations of persons (3), animals or objects and other purposes is suggested, which comprises a carrier (4) of a material in which the impinging X-ray radiation causes detectable changes, as well as a method for recording X-ray images, wherein changes in charge carriers on the surface of a carrier (4) are determined for evaluation of the radiation from the object (3) being observed.

Description

[0001] This application is related to DE 198 50 608 filed Nov. 3, 1998 the entire disclosure of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] The invention is based on a device and a method for recording, processing and illustrating X-ray images in accordance with the pre-characterizing part of claims 1 and 2.

[0003] Medicine uses X-rays for diagnosis. In technology, X-rays are used for testing, e.g. for testing material. Towards this end, the object to be examined is subjected to X-ray radiation. The rays passing through the object are recorded by an X-ray image converter. Known X-ray image converters are e.g. X-ray films which directly show the contrasted negative projected image. Moreover, polyester sheets coated with barium halogenide crystals are known which are scanned by a laser beam after exposure to X-ray radiation and thereby emit light pulses of an intensity which corresponds to the intensity of the X-rays. The light pulses are evaluated after digital image processing in a computer and can be printed out. A further possibility of visualization of the X-ray image is the use of fluorescence of different substances in the X-ray light. X-rays are also used in science and research for a wide range of applications.

[0004] Disadvantageously, known X-ray image converters require a considerably high radiation dose for satisfactory evaluation and visualization. This is particularly disadvantageous since recordings must often be repeated. If e.g. CCD cameras or other detector systems are used for recording the light pulses emitted by a crystal coating, the known methods have the further disadvantage that such systems may be damaged with time by the X-ray radiation.

SUMMARY OF THE INVENTION

[0005] In contrast thereto, the inventive X-ray image converter having the characterizing features of the claims, has the advantage that a carrier is used for recordings which is an inexpensive, disposable component which can be replaced after repeated use and whose surface, e.g. the charge carriers, is detectably changed by the impinging X-ray radiation. Evaluation is carried out not optically via a lens or via secondary light emissions on a screen, but electrically. The inventive system has the further advantage that it is considerably more sensitive than the known methods and image converters and therefore requires a considerably smaller radiation dose. The increased sensitivity is also very advantageous in other applications such as analysis, measuring, control and observation devices.

[0006] In accordance with an advantageous design of the inventive X-ray image converter for electrostatic methods according to claims 2, 7, 8, 9, the carrier consists of an insulating, electrically well chargeable material, in particular of plastic sheet. This material may contain air or gas in small cavities. This material has the advantage that even low radiation energy deposition already causes changes in the charge carriers which, however, do not discharge immediately. Scanning of the change of the charge carriers is thereby possible within a certain time after exposure to the X-ray radiation.

[0007] In accordance with a further advantageous embodiment of the invention, one side of the carrier is provided with an electrically conducting coating. This causes uniform electric charging of that side and also direct contact with the carrier, which is an insulator and which only becomes weakly conducting during irradiation. This coating permits an increase in sensitivity and uniformity.

[0008] In accordance with a further advantageous embodiment of the invention, the other side of the carrier is provided with a plurality of electrically conducting surfaces which are electrically insulated from one another. They are also electrically insulated from the conducting layer described in the above paragraph. The plurality of surfaces form, together with the opposite surface, a plurality of separate capacitors having a certain capacitance. These surfaces are so-called pixels which are ideally square and uniform but may also have other shapes. The size, number and distribution of these surfaces depend on the required resolution and also on other parameters such as sensitivity, noise and scanning methods.

[0009] Immediately before recording with e.g. X-rays, the two sides are charged (polarized) with a constant D.C. voltage applied across the two sides. If the surface is fully covered, one single contact is sufficient. In the case of one side having pixels, all surfaces must be contacted. This may be effected e.g. by a roller or in an analogous fashion. The detecting device or scanning device can also be configured to perform this task. The charging contacts are then removed and irradiation follows to effect charge exchange and thereby a voltage drop at the individual capacitors or pixels. The voltage drop at each individual pixel is a function of the radiation intensity at this pixel or in the carrier layer (dielectric) of this pixel. After irradiation, the pixels are scanned as quickly as possible which may occur through contact or without contact (capacitively, through electrostatic induction) or in a different conventional manner.

[0010] To increase the capacitance on the pixel surfaces, several layers of conducting laminates can be used, which are connected as required. In the basic version, the layers are parallel to the carrier. However, to increase the capacitance, facilitate production, or for other reasons, the conducting layers must not necessarily be parallel to the carrier.

[0011] The principle of operation in the above embodiment can be modified while still maintaining an operable device. The conducting surfaces increase the scanning capability and the signal-to-noise ratio. In accordance with further advantageous embodiments of the invention, solutions other than conducting surfaces are possible. Omission of the pixel layer may produce a better resolution. There is, however, the associated risk of systematic errors and increased noise. Moreover, other conventional physical methods which react to irradiation may be utilized optionally, and if advantageous, combined with the embodiment described above.

[0012] The carrier is basically passive. In accordance with an advantageous embodiment, electric conductors and current circuits, and furthermore passive and/or active elements may be used on or in the carrier, e.g. to generate or prolong maintenance of the polarization voltage, to intensify signals or to improve transmission to the detector device. Such devices can be powered and the information read-out via contacts, inductively, capacitively or in a different conventional fashion.

[0013] In an advantageous embodiment of the invention, the measurement of the electric voltage at the individual pixels may occur simultaneously with irradiation. In this case, the current to or from the pixels or the resistance may be measured, since each of these quantities depends on the intensity of the rays at the respective pixel. The information content can be read out from the carrier during or following irradiation. In this case as well, the pixels must be charged before or during irradiation.

[0014] To extend the time between charging, irradiation and scanning, or for other reasons, one or more masks can be used, having specific geometric and electric properties with respect to the carrier, which influence the pixel surfaces just before irradiation, using contacts or in a different fashion. An analogous or the same method may be carried out between irradiation and scanning. Even during irradiation, the use of a mask may be advantageous. The mask is preferably disposed parallel to the carrier and can possibly contact or nearly contact the carrier. In another embodiment, the mask may be a roller which rolls over the carrier or vice versa. In a further embodiment, the mask completely or partially follows the movements of the carrier on the surface to be irradiated for imaging. The mask may also be on the side facing the rays as long as radiation attenuation is negligible or can be compensated for. In that case, it could be combined with the shadow casting device of claim 18.

[0015] The carrier may consist of more than one layer (sheet) or several carriers can be used at the same time. The different layers or carriers can have specialized functions, can supplement one another, and can cooperate. They can move together, partially together, or differently.

[0016] The invention may also be used with radiation other than X-rays, depending on the purpose and type of carrier, e.g. with alpha, beta and gamma radiation. Detection of other particles and their tracks or of cosmic radiation is also possible in this fashion.

[0017] In accordance with an advantageous embodiment of the invention, magnetic fields or magnetic field changes can be recorded which can also be processed and represented as two- or three-dimensional images. The carrier is equipped with appropriate conventional devices such as electric circuits and/or materials having magnetic properties and the detector device is correspondingly adjusted. To increase the sensitivity and accuracy, the carrier, its materials or parts thereof may be pre-magnetized or saturated before and/or during recording.

[0018] In accordance with a further advantageous embodiment of the invention, a detector device is provided which can be moved relative to the carrier for detecting the information contained on the carrier. The movement between the detector device and the carrier is parallel to the carrier surface, in one or two directions. After the action of the incident radiation, the carrier is scanned by the detector device. Since the carrier material is insulating, scanning can occur within a certain time following action of the X-rays. The detector device can thereby easily be protected from the radiation and is therefore not damaged.

[0019] In accordance with a further advantageous embodiment of the invention, the detector device can be moved over the carrier in two directions. The carrier itself is thereby stationary. The detector of the detector device may be punctiform. If several detectors are disposed next to one another to produce a detector device with one-dimensional extent, it is sufficient to move same in one direction relative to the carrier.

[0020] In accordance with a further advantageous embodiment of the invention, the carrier, e.g. the plastic sheet, is disposed on rollers or cylinders to permit movement of the carrier relative to the detector device.

[0021] In accordance with a further advantageous embodiment of the invention, the detection device within the detector is a field effect transistor or an integrated amplifier provided with a field effect transistor at the input thereof.

[0022] In accordance with a further advantageous embodiment of the invention, a field effect transistor is used as the detection device in the detector, however, without a gate: the electric field of the carrier surface thereby directly influences the current between the source and drain, instead of the controlling gate electrode. This influence is recorded and evaluated. Scanning of the carrier surface may be effected without contact. This principle is provided in claim 20 as an embodiment. Therein, it is possible that many measuring points simultaneously act over a complete line width, similar to fax devices or paper sheet scanners.

[0023] In accordance with a further advantageous embodiment of the invention, several carriers are disposed in different spatial positions relative to the object to be recorded for recording spatially resolved information. In this case, at least 2 X-ray radiation sources should be provided or the position of the source should be changed relative to the object.

[0024] In accordance with a further advantageous embodiment of the invention, the information recorded by the detector device is evaluated and displayed by means of a computer. The X-ray images may be stored in the computer, printed out by printers and processed in a different fashion.

[0025] In claim 3, scanning is effected, e.g. immediately in front of the rollers.

[0026] In claim 4, the solution depends on the physical principles of the carrier. The scanning roller may e.g. have contact points which contact the pixels individually to scan the information, or conducting surfaces, optionally below a thin insulator, which scan the pixels without electric contact, e.g. capacitively. If deflecting rollers simultaneously carry out scanning, the pixels are usually on the side facing the scanning rollers.

[0027] In claim 5 it is sufficient to move the detector device in only one direction, e.g. across the longer side of a rectangle, if its detectors are distributed over the entire width, i.e. across the shorter side of the rectangle, similar to a flat bed scanner for paper sheets. The detector device must have a number of detector points required for the resolution.

[0028] In accordance with claim 6, the two or more information planes permit calculation of e.g. improved image resolution and three-dimensional information, since i.a. the positions of radiation sources, objects and carrier levels are known. The planes are parallel to one another only in their simplest embodiment and may also have different orientations.

[0029] Intermediate layers can be used in claims 7 and 8 to increase the effect, e.g. to increase the capacity or sensitivity.

[0030] Claim 9 is directed towards a solution which increases sensitivity. To achieve the purpose of the invention, any conventional method can be applied and optionally combined. The same is true for claim 10.

[0031] Claim 11 differs from claim 6 in that the recording planes are disposed not one behind the other but next to one another, with respect to the path of the rays.

[0032] Claim 12 cooperates geometrically with claims 11 and 6. The direction of radiation through the object is different, e.g. also perpendicular or at an angle with respect to one another.

[0033] In claim 16, the image converter does not record the radiation originating directly from the radiation source, influenced by the absorption effects of the objects being examined, but rather radiation sources within the object itself which become sources following irradiation by the actual primary radiation source. This point is partially related to applications using optical microscopes with which the object is not observed using transmitted light but rather e.g. in the dark field. In this case, the image converters are usually not in the path of the rays of the radiation source, as in classical X-ray recordings, but lateral or transverse thereto and are shielded from the primary radiation. It is possible to simultaneously use several converters in accordance with the invention, even with only one primary radiation source. The optimum angle or orientation depends on the physical mechanism utilized. Deflection angles and other parameters which are further processed later for evaluation and representation can be calculated numerically in a computer using the inventive converter and must not necessarily be searched for through mechanical adjustments, if the converters are sufficiently large. A special case of this embodiment involves sources in an object which are not secondary but actually primary, i.e. real sources, in particular radioactive sources, such as radioactively marked capsules, agents, medication, tools, instruments, and also sources in space or on the earth. When the effects and the inventive converter are reasonably combined, e.g. through application of fluorescence effects, use of selective filters and spatial image recording, then through orientation of X-ray source and converter in a same direction, even in close proximity to one another or installed in the same housing, e.g. mines, explosives or other objects can be detected at large distances. With substances comprising phosphorescence effects, the primary source is switched on for illumination, is then switched off and the recording is started immediately thereafter.

[0034] To improve contrast, selectivity and sensitivity, reference recordings are taken without the object, and with object but without searched features to be imaged (e.g. source of an illness, instruments, foreign bodies), and the features to be searched and their physical properties are recorded separately and are taken into consideration numerically during evaluation and image representation.

[0035] Claim 17 describes an auxiliary means which casts defined shadows (in the relevant spectral range of the recording) onto the converter. In a simple embodiment, identical round short rods of a suitable material, e.g. aluminum, are used, which are perpendicular to the converter. The rods have a similar effect as a sun-dial. The angle of impingement can be determined numerically or in a different fashion and be displayed. In an embodiment, the auxiliary means can be easily aligned towards the source because the shadows thereby become minimal in size, reflecting maximum absorption. In a similar manner, alignment towards secondary sources in accordance with claim 16 is also possible. One or several primary or secondary sources can be represented as an image or in a different manner following numerical processing. In principle, one rod is sufficient, however, a grid, mesh or another formation can also be used instead of rods. The length of e.g. the rods or the distance from the recording plane is given i.a. by the required angular resolution and the resolution of the converter.

[0036] Claim 21 utilizes the same effect as in electret capacitor microphones. The plastic material of the membrane is polarized during production to always permit subsequent build-up of an electric voltage. The method known from microphone technology can be modified for the inventive application in the carrier, to facilitate or omit charging before irradiation. Claim 21 can also be combined e.g. with claim 9 to improve the results.

[0037] Further advantages and advantageous embodiments of the invention can be extracted from the following description, the drawing and the claims.

[0038] The drawing shows an embodiment of the invention which is described in more detail below.

BRIEF DESCRIPTION OF THE DRAWING

[0039] FIG. 1 shows a schematic representation of an arrangement of an X-ray source, a person to be examined and an X-ray image converter; and

[0040] FIG. 2 shows an embodiment of the X-ray image converter in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0041] FIG. 1 shows an arrangement of X-ray source 1 and X-ray image converter 2 for recording X-ray images of a person 3. The X-ray converter comprises a plastic sheet 4 carrier which is disposed on two rollers 5 which can support and transport the sheet. The plastic sheet 4 can have a thickness of fractions of to tens of centimeters. After impingement of the X-rays on the plastic sheet 4, the sheet 4 is rolled over the rollers and moved past a detector device 6. The detector device 6 is not subjected to X-ray radiation and can therefore not be damaged by it. The sheet and rollers may comprise a precise guidance, e.g. a pin feed system and have synchronization markings. In the present example, the sheet is an endless belt.

[0042] The detector device has a longitudinal extension parallel to the rollers (not visible in the drawing) and must therefore not be moved over the plastic sheet since the sheet itself moves over the detector device along its entire width. The detector device may be connected to a computer via appropriate leads, for evaluation of the scanned voltage differences.

[0043] Depending on the intensity of the radiation and on the properties of the plastic sheet, a charge difference may occur not only on the side of the plastic sheet facing the X-ray source 1 but also in the area of the plastic sheet 4 facing away from the X-ray source. For evaluation, both regions of the plastic sheet can be used.

[0044] FIG. 2 shows an embodiment of an X-ray converter 2 in accordance with the invention. A partial section of the entire converter of FIG. 1 is illustrated, including the lower roller 5. The plastic sheet 4 is illustrated with exaggerated thickness for reasons of clarity. Referring to the rear portion of the converter 2 at the right hand part of FIG. 2, the plastic sheet 4 is seen to be lined on one side thereof with an array of mutually separated electrically conducting pads 10. The pads 10 are electrically insulated from each other via the plastic sheet 4. A charger 12 is disposed proximate the converter 2 and contacts the pads 10 to apply electrical charge thereto. The charger 12 is connected to an appropriate power supply 14. As can be seen on the left portion of FIG. 2, the side of the plastic sheet 4 opposite to the pads 10 is covered with a uniform electrically conducting sheet 16. The sheet 16 can be maintained at ground potential through contact with an electrically grounded and conducting surface 18 of the lower roller 5. A detector device 6 is located at the lower rear portion of the converter 2 and comprises a linear array of detection units 20. The detection units communicate with an analysis unit 22 via suitable cable connection 24. The embodiment of FIG. 2 operates as follows. In an initial step the rollers 5 of FIG. 1 ( only the lower one of which is illustrated in FIG. 2 ) are set into rotation by a suitable drive motor in the direction indicated by arrow 26. The pads 10 located at the rear of the converter 2 thereby pass by charger 12 and are charged thereby to a suitable voltage which is typically in the range of 50 to 100 volts. As the lower roller 5 continues to rotate, the plastic sheet with its associated charged pads 10 travels over the top roller 5 see FIG. 1 ) and proceeds in a downward direction at the front, left portion of the converter 2. At this point in time, rotation of the lower roller 5 is interrupted and the converter is exposed to X-ray radiation 28. The X-ray radiation passes through the thin layer of pads 10 and penetrates into the plastic sheet 4 to ionize materials in the plastic sheet 4. As a result of these ionization processes, a voltage decrease between a given pad 10 and the oppositely disposed conducting sheet 16 which is proportional to the X-ray dose absorbed by that portion of the sheet 4 proximate a given pad 10 and therefore to the X-ray intensity incident on that pad 10. Following exposure, the X-ray source 1 (see FIG. 1) is switched off and the rollers 5 are once more set into rotation in the direction of arrow 26. Exposed pads 10 are thereby caused to pass by detector array 6 which detects the residual voltage in the respective pad 10 by means of detection units 20 and passes this information on to analysis unit 22 for image construction.

[0045] All the features shown in the description, the following claims and the drawing may be essential to the invention either individually or collectively in any arbitrary combination.

List of Reference Numerals

[0046] 1 X-ray source

[0047] 2 X-ray image converter

[0048] 3 person

[0049] 4 plastic sheet

[0050] 5 roller

[0051] 6 detector device

[0052] 10 pads

[0053] 12 charger

[0054] 14 charger power supply

[0055] 16 conducting sheet

[0056] 18 roller ground surface

[0057] 20 detection units

[0058] 22 analysis unit

[0059] 24 cables

[0060] 26 rotation direction

[0061] 28 impinging X-rays

Claims

1. An X-ray image converter for recording and evaluating information which can be detected within suitable radiation regions, e.g X-ray examination of persons (3), animals or objects or for scientific and technical purposes such as e.g. analysis or controls, comprising a carrier (4) on which the X-ray radiation impinges and effects characteristic changes, characterized in that the carrier (4) is a sheet, in particular a plastic sheet and that for detecting the characteristic change, a detector device is provided which scans the surface of the sheet during relative motion with respect to the sheet or which detects the information in a different fashion.

2. The X-ray image converter according to claim 1, characterized in that the sheet has useful properties to detect the changes such as e.g. electrically conducting surfaces (electrodes) on one or both surfaces or also in between, which are electrostatically charged before exposition and which are scanned after exposition to measure the charge or voltage differences caused by irradiation or in that a magnetic effect is utilized for detection or that physical methods are combined.

3. The X-ray image converter according to claim 1, characterized in that rollers (5) or cylinders are provided for retaining and moving the sheet (4) in a direction relative to the detector device (6) by means of which the sheet is moved over the detector device after exposition.

4. The X-ray image converter of claim 3, characterized in that the detector device, and/or a charger, is integrated in one or both of the above-mentioned rollers.

5. The X-ray image converter of claim 1, characterized in that the detector device (6) can be moved over the carrier (4) in one or two directions in dependence on the number and arrangement of the measuring points of the detector device.

6. The X-ray image converter of claim 1, characterized in that more than one sheet plane, disposed one behind another with respect to the path of the rays, are exposed simultaneously and subsequently scanned and evaluated to receive more information and calculate improved image results, wherein both sheet regions between the rollers and both rollers can be simultaneously utilized, if rollers are provided for retaining and moving the sheet.

7. The X-ray image converter of claim 2, characterized in that one side of the sheet is provided with an electrically conducting coating.

8. The X-ray image converter of claim 2, characterized in that one side of the sheet is provided with many electrically conducting insulating surfaces which form pixels, i.e. individual image points, wherein should a conducting surface already be used, the other opposing side of the sheet is used for the pixels.

9. The X-ray image converter of claim 2, characterized in that the two surfaces of the sheet or the electrodes or pixels are charged with an electric voltage before irradiation, that the charge or voltage difference is reduced through irradiation and that after irradiation, the electric voltage or voltage difference between the two sheet sides is measured (scanned) at the individual image points and evaluated.

10. The X-ray image converter of claim 2, characterized in that the detector device (6) comprises a field effect transistor or an operation amplifier, having an FET input, as detector for scanning the pixel side.

11. The X-ray image converter of claim 1, characterized in that, for recording spatially resolved information, several carriers are disposed at different spatial positions relative to the object to be recorded.

12. The X-ray image converter of claim 1, characterized in that for recording spatially resolved information, several radiation sources are disposed simultaneously or sequentially at different spatial positions relative to the object to be recorded, wherein X-ray tubes having 2 or more effective anode regions (focal spots), mechanical movement of the tube or use of scattering means may be provided.

13. The X-ray image converter of claim 1, characterized in that the information recorded by the detector device is evaluated and displayed by means of a computer.

14. The X-ray image converter of claim 13, characterized in that the information recorded by the computer is locally stored, transported via data communication, printed onto transparent film or paper or other media or protected from unauthorized access, changes or abuse, either intentionally or unintentionally through cryptological methods and/or electronic authority checks.

15. The X-ray image converter of claim 13, characterized in that the information processed into images is shown in color to increase the meaningfulness, facilitate interpretation, display additional information or for other reasons.

16. The X-ray image converter of claim 1, characterized in that secondary radiation, stray radiation, “fluorescence responses”, diffraction, grid diffraction effects, certain spectral ranges selected from the object, afterglow or polarization effects are recorded from the examined objects, are evaluated and represented as an image or in a different fashion or integrated in other images or evaluations, as well as actual sources located in the object itself.

17. The X-ray image converter of claim 1, characterized in that a shadow casting attachment may be mounted in front of the inventive X-ray image converter to calculate, through image processing, the direction of the impinging irradiation from the recorded images by means of the shadows cast by the attachment to obtain, after numerical calculation in the computer, i.a. a similar image representation as through a lens focussing the rays in front of the image converter and that additionally or instead of the attachment, other shadows from the field of view, in particular also shadows of the object are taken into consideration, wherein additional spatial information and information concerning physical response of the object to the radiation is very useful and essential for certain evaluations.

18. The X-ray image converter of claim 1, characterized in that different spectral regions of the source or sources, e.g. the X-ray tube, are applied for the same examination, either simultaneously or immediately following one another to permit or improve detection of the properties of the examined object, e.g. a tumor or a defective location by combining the different information in most cases by a computer.

19. The X-ray image converter of claim 2, characterized in that the detector device for scanning the image utilizes substantially the same electronics as a flat bed scanner for paper (e.g. format A4 or US letter) or a fax machine when scanning the inserted documents, the difference being that the first step of the input elements reacts not to light (light to dark) but to voltages or charges or to another physical effect such as e.g. magnetic fields or electromagnetic fields.

20. The X-ray image converter of claim 1, characterized in that the carrier or the sheet may consist of several layers and that also more than one carrier may be used in cooperation with specialized functions, wherein the movements may be partly identical and partly different and that carriers may also contain other passive and active elements to effectively support the technical functions before, during and after irradiation.

21. The X-ray image converter of claim 2, characterized in that an electret is used as carrier or part or layer thereof which independently creates D.C. voltage (polarization voltage).

22. The X-ray image converter of claim 1, characterized in that the claims can be effectively combined to carry out basically novel or improved examinations and permit or facilitate detection and illustration of details.

23. Method for recording X-ray images in X-ray examinations of persons, animals or objects, characterized by the following methods steps, that the object to be examined is irradiated with X-ray radiation, that the X-ray radiation emitted by the object or transmitted through the object is received by a carrier (4), and that the change of the charge carrier on the surface of the carrier (4) is detected for evaluation purposes.