JP2984841B2 - X-ray imaging device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an X-ray imaging apparatus for creating an image using transmitted X-rays, and particularly to a flat large-diameter X-ray imaging apparatus.

(Prior Art) A diagnostic X-ray system is a device that irradiates X-rays to a diagnostic site of a subject and images transmitted X-rays to diagnose the X-rays. At present, the following devices are mainly used as means for storing an image of the X-ray transmitted through the subject.

I. An imaging device that exposes film directly.

B. X-ray TV using Cine Imaging System C.II (Image Intensifier)
Apparatus d. X-Ray Image Reading Apparatus Using Stimulable Fluorescence (Problems to be Solved by the Invention) The above-described image recording apparatus has the following features and problems.

I. Photographing devices that directly expose the film need to be developed and cannot be viewed in real time. Obviously, moving images cannot be observed.

B. The cine imaging device can observe a moving image after development, but cannot see it in real time.

C. X-ray TV devices using II can watch moving images in real time, but the equipment is large and cannot be made thin.

D. An X-ray image reading apparatus using stimulable fluorescence stores an image based on transmitted X-rays in a phosphor by irradiating the X-rays, and when irradiating the phosphor with a red laser beam, the above image is reproduced by blue light. Therefore, this is an apparatus which amplifies this with a photomultiplier tube and inputs it to a computer to form an image. This device requires a procedure such as temporarily storing the transmitted X-ray image on the phosphor, and then irradiating red laser light at the location of the imaging device. It cannot be made thin. Moreover, it is an expensive facility.

The present invention has been made in view of the above points, and an object of the present invention is to realize a thin, nearly flat, large-diameter X-ray imaging apparatus that can be observed in a moving image state in real time.

(Means for Solving the Problems) According to the present invention for solving the above-mentioned problems, an input phosphor screen for forming a visible light image by the arriving X-rays, and a photocathode for emitting photoelectrons by receiving light from the visible light images An output fluorescent screen that receives the photoelectrons and emits light to form a visible light image, an anode configured by a metal back of the output fluorescent screen and applied with a positive voltage to attract the photoelectrons, And a field coil wound on the outer periphery of the side surface of the container to apply a magnetic field parallel to the electron traveling path, and a visible light generated on the input phosphor screen 1 is maintained. Proximity type II that allows the light image to appear as it is on the output phosphor screen, and a plurality of imaging units including a lens that outputs a visible light image generated on the output phosphor screen by dividing the visible light image into a plurality of sections and outputting image data. Output analog of the imaging means An AD converter that converts a signal into a digital signal, a frame memory that is written by synthesizing and writing one image data by aligning the light images divided by the plurality of imaging units, and a frame memory that is stored in the frame memory. And a DA converter for calling the combined image data and converting it into an analog signal.

(Function) The X-ray fluoroscopic image is converted into a visible light image on the input phosphor screen of II, converted into photoelectrons on the photocathode, and formed on the output phosphor screen. This image is divided and photographed by a plurality of photographing means and combined into a single image by a frame memory, thereby shortening the distance between II and the photographing means to obtain a thin X-ray image photographing apparatus. .

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a circuit configuration diagram using an apparatus according to one embodiment of the present invention. In the figure, 1 is X that has passed through the subject and reached
An input phosphor screen 2 which emits fluorescent light by a line to form an X-ray image of a visible light image thereon is a photocathode which receives a visible light image formed on the input phosphor screen 1 and emits photoelectrons. 3 is a photocathode 2
An output phosphor screen 4 for forming a visible light image by an electron image by electrons emitted from the light source 4 is a power supply in which a negative electrode is connected to the photocathode 2 and a positive electrode is connected to an anode 5 made of a metal back covering the back surface of the output phosphor screen 3. is there. Each of the above parts is a glass container 6
And the inside thereof is maintained in a vacuum. 7 generates a magnetic field H ₀ to the action of straight photoelectrons in order to suction so as to draw as image depicted on the input phosphor screen 1 the photoelectrons emitted from the photocathode 2 to the output phosphor screen 3 Field Coil. The above components constitute the proximity type II8. The proximity type II is configured such that the distance between the photocathode 2 and the output phosphor screen 3 is short, and an optical image generated on the photocathode 2 by the action of an electric field and a magnetic field is directly drawn on the output phosphor screen 3. It is.

Reference numeral 11 denotes a division for dividing one visible light image formed on the output phosphor screen 3 of II8 into a plurality of small sections and projecting the image portion of each section onto the CCD image sensor 12 of the divided number of sections. The number of lenses is equal to the number of divided sections. The CCD image sensor 12 is composed of a number of CCD elements.
Can be obtained. Reference numeral 13 denotes a CCD sensor support circuit for operating the CCD image sensor 12 by causing the CCD image sensor 12 to perform signal generation, pulse generation for transfer, drive, image processing, and the like. The image signal output from the CCD sensor support circuit 13 is converted into a digital signal by the AD converter 14 and output. Reference numeral 15 denotes a frame in which the input digitized signals of the visible light image of the divided output phosphor screen 3 from each CCD image sensor 12 are combined into one image according to the arrangement of each CCD image sensor 12 and stored. A memory 16 is a DA converter that converts a digital signal output from the frame memory 15 into an analog signal, and 17 is a monitor TV that displays data stored in the frame memory 15 as it is.

Next, the operation of the embodiment configured as described above will be described. The X-rays transmitted through the subject reach the input fluorescent screen 1 through the II8 container 6, and draw a visible light image on the input fluorescent screen 1. The photocathode 2 emits photoelectrons corresponding to the visible light image by the irradiation of the visible light, and the photoelectrons penetrate the anode 5 formed by the metal back and emit the output fluorescent light by the action of the electric field by the power supply 4 and the magnetic field H ₀ by the field coil 7. The light reaches the surface 3 and emits fluorescent light to generate a visible light image as it is on the photoelectric surface 2.

The visible light image generated on the output phosphor screen 3 is divided into a number of sections corresponding to the number of the lenses 11 and forms an image on the CCD image sensor 12 through the lenses 11. The charge generated in the CCD image sensor 12 by the input light image is transferred to the CCD support circuit 13.
Is output as an image signal from the output unit, and is converted into a digital signal by the AD converter 14. The output data of the image for each section of the AD converter 14 is stored at the position of each section of the frame memory 15, and the frame memory is stored by all the AD converters 14.
An X-ray transmission image is formed and stored on 15. The image data is read out, converted into a digital signal by the DA converter 16, and displayed on the monitor TV 17 as shown in the figure.

In the above X-ray imaging apparatus composed of II8, lens 11 group and CCD image sensor 12 group, many lenses 11
Since the area shared by the lens is a small part, the lens 11 can be brought very close to the output phosphor screen 3. Therefore, it is necessary to make a certain X-ray imaging system thin from the proximity type II8, the lens 11, and the CCD image sensor 12. Can be. By increasing the number of divisions of the image, the distance between the II 8 and the lens 11 can be further reduced to further reduce the thickness.

The present invention is not limited to the above embodiment,
Various variants can be obtained. FIG. 2 is an explanatory view of an embodiment in which the area covered by the lens 11 is widened so that the image formed on the CCD image sensor 12 overlaps with the adjacent area. The relationship is shown. In the figure, the same parts as those in FIG. 1 are denoted by the same reference numerals. 21 is one lens
The area covered by the lens, which is the area covered by 11, is indicated by a dashed line, a dashed line, or a two-dot chain line. The assigned area 21 of the lens is wider than the divided area 22 of the output phosphor screen shown by the solid line, and overlaps with the assigned area 21 of the adjacent lens. This is a lens
11, for correcting shading distortion in the peripheral portion caused by the CCD image sensor 12 and the like. When the overlap portion is gradually weighted in the CCD support circuit 13 to form an image by a gradual change, the splicing portion can be connected inconspicuously. Further, if it is made mechanically rugged, there is no shift due to a change over time in the overlapping of the combined images by the light input to the CCD image sensor 12. In addition, it is not necessary to perform sensitivity adjustment, shading adjustment, and the like frequently in real time or equivalently, and it is sufficient to perform adjustment during maintenance.

CCD image sensor with lens as above (CCD T
When using the (V camera itself), what can be a problem is the overall dynamic range. This is, for example, that the offset, sensitivity itself, and linearity of each pixel are corrected by a linear expression using a correction table. Alternatively, if there is an element that has dropped out, the deterioration of the dynamic range can be corrected by a method such as making up for it by approximate interpolation from the surroundings. Further, it is considered that the correction can be made not only for each pixel but also for each CCD image sensor. The distribution of sensitivity, dark area characteristics, and blooming characteristics in one sensor is not considered to be a problem to the left, but the above characteristics do not always match between sensors of different manufacturing lots. It is necessary to provide a correction table for that.

The lens 11 may be shaped to be adhered to the glass constituting the container 6 on the output fluorescent screen 3 side of the II8.

FIG. 3 is a schematic structural view of an output section of II8 according to another embodiment of the present invention. In the figure, the same parts as those in FIG. 1 are denoted by the same reference numerals. In the figure, reference numeral 23 denotes a lens array formed by molding the glass itself outside the output fluorescent screen 3 of the container 8 of the II8, and captures the light output of the output side of the II8 with a high capture rate as close as possible to 100% and a CCD. This is effective for inputting to the image sensor 12. The individual lenses of the lens array 23 are not merely lenses having a round outer shape, but are arranged as a lens having a green shape as a square, and further as an aspherical lens or a Fresnel lens, so that the aperture utilization rate can be increased. Alternatively, the lens array 23 may be made of plastic and attached to the glass of the output fluorescent screen 3 of II8 with a translucent adhesive. Numeral 24 is an adhesive layer in the case of bonding in this manner.

FIG. 4 is a schematic structural view of an output section of II8 of still another embodiment. In the figure, the same parts as those in FIG. 3 are denoted by the same reference numerals. In the figure, reference numeral 25 denotes a light-shielding layer provided between the individual lenses 26, outside the lenses 26, and at a portion corresponding to the side of the output fluorescent screen 3 of the container 6. This way each lens
The image quality can be further improved by blocking unnecessary light from the adjacent lens. In this case, each lens 26 splits the light image of the output phosphor screen 3 so that the split images overlap.
Lens 2 needs to be incident on CCD image sensor 12
Since the light-shielding layer placed between 6 cannot be placed at the position of the container 6, the glass of the container 6 in front of the output fluorescent screen 3 is appropriately thickened, or a spacer 27 is inserted as shown. Although this part may be theoretically formed as an air layer, it may cause loss of light amount due to interfacial reflection, and it may also cause ghost, so a dark spacer made of glass or plastic may be used. 27 is preferably inserted through the adhesive layer 24. Therefore, a tall lens with a square edge
The required number of lenses 26 are adhered to each other with a light-shielding plate interposed therebetween, and then attached to the glass of the output surface of the II8 via an additional plastic spacer 27. The image plane formed by the individual lenses 26 may slightly shift back and forth, but this is adjusted by the distance between the lens 26 and the CCD image sensor 12.

As a result of the above-mentioned adjustment, adjustment of the difference in the reduction ratio for the output phosphor screen 3 of II8 of each CCD image sensor 12 which is also secondary, pseudo-correction, correction of absolute sensitivity, or II8
5 can be performed by the circuit shown in FIG. In the figure, the same parts as those in FIGS. 1 and 4 are denoted by the same reference numerals. In the figure, 30 is each CCD
An intermediate memory serving as a working buffer memory for the image sensor 12, in which a signal obtained by converting an output signal of the CCD support circuit 13 into a digital signal by the AD converter 14 is temporarily stored. 31 performs digital image processing on the data read from the intermediate memory 30 to compensate for slight inclination (rotation in the axial direction) of the CCD image sensor 12, correction of shading, correction of absolute sensitivity, An image processing circuit used for compensating for local variations and the like. Therefore, the image processing circuit 31 performs processing such as slight rotation, enlargement, reduction, and parallel movement of the image. The lens 26 used here can be an aspherical lens, a Fresnel lens, a Fresnel lens having an aspherical characteristic, or the like, like the lenses shown in FIGS. 3 and 4. Instead, a lens having a plurality of lenses may be used.

FIG. 6 is an explanatory diagram of a technique for widening the dynamic range. The method of expanding the dynamic range is performed as follows. In step II8, the multiplication factor is switched, and two or more times are taken as one unit, and the medium-high level area and the low-medium level area of the pixel value are separately written in the frame memory 15. An example will be described in which an image is constructed by using the two data as one unit. The graph in the figure is a graph in which the horizontal axis represents the logarithmic value of the input light flux, and the vertical axis represents the logarithmic value of the X-ray density or voltage. In the figure, the solid line is the data collected in the first trial, and the curve # 1 curve DBE,
The dashed line is the # 2 curve ABC of the data collected in the second trial with a light beam of normal intensity. Since the data obtained by the first trial is data having a small multiplication factor, that is, a data having a small input light flux, from the top of the data (from the MSB)
It is stored in the frame memory 15 and is not stored below a certain weak part which may be noisy or offset. The data is stored in the lower part (LSB) by the second trial. This will be described in terms of processing on digital data.
As shown in FIG. The figure shows a case where the density D or the voltage E is represented by 8 bits.
Are added together by shifting # 2 by 5 bits downward. The overlapping parts are halved and added together. The bottom row is the obtained synthesized data, and the top row is truncated to make it 12-bit data. This may be done by truncating the data at the bottom. The result of the addition in this manner is the curve shown in FIG. 6, where the saturated portions of the curves # 1 and # 2 and the curves # 1 and
The curve formed by cutting off the portion of the # 2 curve including noise and the like is the curve whose dynamic range is finally widened. This is because the lower part of the data due to the weak # 1 light beam is buried in noise or the like.
The data above is not compensated for by shifting it downward, and the data above the strong # 2 light beam is saturated, and is thus supplemented by the weaker # 1 light beam. Although the description has been made by switching the multiplication factor of II as the means for creating the strong and weak data, it is performed by changing the X-ray intensity by the X-ray source and by changing the integration time for integrating the output of the CCD image sensor 12. You may.

Further, the data stored in the frame memory 15 may be a logarithmic value of the pixel value. By doing so, the capacity of the frame memory can be saved.

(Effects of the Invention) As described in detail above, according to the present invention, a thin, large-diameter X-ray imaging apparatus close to a flat type capable of observing a moving image in real time can be realized, and the practical effect is great.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram using an apparatus according to an embodiment of the present invention, FIG. 2 is a diagram showing a relationship between a divided screen and a lens coverage area, and FIG. 3 is an embodiment of a lens unit configuration. 4, FIG. 4 is a diagram of another embodiment of the lens unit configuration, FIG. 5 is a diagram of a circuit for correcting various errors generated in lens assembly, FIG. 6 is an explanatory diagram of a method of expanding a dynamic range, FIG. 7 is an explanatory diagram of the data processing of the method of FIG. 6 for expanding the dynamic range. DESCRIPTION OF SYMBOLS 1 ... Input phosphor screen, 2 ... Photocathode 3 ... Output phosphor screen, 4 ... Power supply 5 ... Anode, 6 ... Container 7 ... Field coil, 8 ... II 11,26 ... Lens 12 ... … CCD image sensor 13 …… CCD sensor support circuit 14 …… AD converter, 15 …… Frame memory 16 …… DA converter, 17… Monitor TV 25 …… Light shielding layer, 27 …… Spacer 30 …… Intermediate memory , 31 …… Image processing circuit

Claims (3)

(57) [Claims] An image intensifier that receives an X-ray transmitted through a subject on a fluorescent screen and forms a visible light image, divides the visible light image into a plurality of areas, and the adjacent areas overlap each other. A plurality of imaging means for imaging each of the plurality of areas for each area, a plurality of conversion means for converting each image signal output from each of the plurality of imaging means into a digital signal, An X-ray imaging apparatus comprising: a generation unit configured to generate an image corresponding to a visible light image formed on the phosphor screen based on an output signal of the conversion unit. 2. An image intensifier which receives an X-ray transmitted through a subject on an input phosphor screen and forms a visible light image, and which is brought into contact with an output phosphor screen side of said image intensifier to produce said image. A plurality of image pickup means for picking up each area obtained by dividing the visible light image into a plurality of areas by each lens of a lens array integrally formed with the intensifier; and each of the plurality of image pickup means is output from the plurality of image pickup means. A plurality of conversion units for converting each image signal into a digital signal; and a generation unit for generating an image corresponding to a visible light image formed on the phosphor screen based on output signals of the plurality of conversion units. An X-ray imaging apparatus characterized by the above-mentioned. 3. An image intensifier that receives an X-ray transmitted through a subject on a fluorescent screen and forms a visible light image, divides the visible light image into a plurality of regions, and divides the plurality of regions into each region. A plurality of image pickup means, each of which has a lens in which a peripheral portion of an adjacent lens is shielded from light, and each image output from the plurality of image pickup means, respectively. A plurality of conversion units for converting a signal into a digital signal; and a generation unit for generating an image corresponding to a visible light image formed on the phosphor screen based on output signals of the plurality of conversion units. X-ray imaging apparatus.