JPH05130990A - X-ray image detector for medical treatment with automatic exposing function - Google Patents

Abstract

PURPOSE:To decrease or remove the unnecessary irradiation with X-rays and to obtain an X-ray image having good sharpness and resolution by disposing an X-ray intensity detecting element in proximity to an X-ray phosphor on a ceramic substrate for fixing a CCD element and controlling the time for irradiation with the X-rays with X-ray intensity output. CONSTITUTION:The X-ray intensity detecting element 6 is fixed in line up with the transverse direction of the wafer of the CCD element 4 in proximity to the phosphor 2 of the X-ray image sensor to the ceramic substrate 5 and the X-rays transmitted near the desired tooth part transmit the X-ray phosphor 61 so that the phosphor emits light. The electric signal proportional to the light intensity is generated by a photodetecting element 62 and is transmitted to a controller 8 on the outside of the device by a cable 7 contg. lead wires. The anode current of an X-ray tube is shut off when the transmitted X-ray quantity which is detected by the X-ray intensity detecting element 6 and is calculated by integration with the time for the irradiation with the X-rays in an integrating circuit attains equal to the set transmitted X-ray quantity. The image signal accumulated in the CCD element or the memory element in the controller 8 is reproduced by a monitor 81 at the point of this time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a medical X-ray image detecting apparatus, and more particularly to a small dental X-ray image detecting apparatus which is used by being inserted into the oral cavity for dental imaging.

[0002]

2. Description of the Related Art In dental treatment, X which has penetrated a tooth part
The X-ray image is converted into an optical image by a fluorescent screen in a small X-ray image detection device inserted behind an intraoral tooth, and is projected onto an image pickup surface of a solid-state image pickup device such as a CCD device by a glass fiber to obtain a digital signal. An intraoral radiography system is being used which converts the image into a radiograph and reproduces a transmission image of a tooth portion on a monitor image.

In conventional intraoral X-ray photography, the position of an X-ray source for irradiating the target tooth portion with X-rays is set, and a small X-ray image detection device is set behind the tooth portion to perform the imaging. The operator sets the X-ray tube voltage and current of the X-ray generator according to the target site and the patient's physique, and then the X-ray is irradiated for a predetermined irradiation time determined in advance by the X-ray tube voltage and current. Irradiation is performed.

The X-rays emitted from the X-ray source pass through the tooth part which is the subject and are converted into an optical image having a brightness proportional to the transmitted X-ray dose on the fluorescent surface of the X-ray phosphor. Not only X-rays that have passed through the X-ray phosphor are no longer necessary, but the increase in radiation dose adversely affects the human body, and unnecessary X-rays are C
Since it may affect the image signal of the CD element, a countermeasure is required.

Further, in the conventional X-ray image detecting apparatus, the optical input surface or the output surface of the glass fiber for transmitting an optical image is processed so as to be oblique to the fiber strand axis, and the image pickup by the CCD element is performed. It is known to employ a method of projecting a reduced optical image on a surface. In this case CC
The image pickup surface of the D element is arranged parallel to the X-ray direction, or
There is one that is arranged at a place in the container behind the X-ray transmission region behind the fluorescent screen to avoid the influence of X-rays on the CCD element (Japanese Patent Laid-Open No. 2-249537).

[0006]

As described above, the X-ray irradiation conditions of the X-ray generator are determined based on the experience of the operator, and the exposure of the CCD element of the optical image on the fluorescent screen by the transmitted X-rays of the tooth portion. In the conventional method of setting the time, the blackening degree of the X-ray image on the monitor is not constant due to the overexposure or underexposure, and the image quality may change for each photographing, and the image quality necessary for diagnosis may not be obtained. Therefore, re-imaging is often required, not only time is required for dental diagnosis, but the X-ray exposure dose to the patient increases, which is not preferable.

The above-mentioned conventional apparatus in which the glass fiber is formed in the oblique plane with respect to the axis is convenient for reducing the projection image of the subject on the fluorescent screen, but on the other hand, the reproduced X
Since it reduces the resolution of line images, it is not always suitable for use in dental treatment.

Further, before reaching the fluorescent screen from the X-ray source, some of the X-rays are scattered when passing through an object such as tooth tissue, and scattered X-rays of low energy are generated.
Since the CCD element is sensitive to such low-energy soft X-rays and generates an electric signal, the sharpness of the X-ray image reproduced from the optical image from the fluorescent screen is lowered.

In view of the above problems, the present invention provides a human body and a CC.
Provided is a medical X-ray image detection apparatus having an automatic exposure adjustment function capable of reducing or eliminating unnecessary X-ray irradiation which adversely affects the D element as much as possible and obtaining an X-ray image having a good definition and resolution. Is what you are trying to do.

[0010]

In the medical X-ray image detection apparatus of the present invention, the fluorescent surface of the X-ray phosphor and the imaging surface of the solid-state image pickup device are connected by a glass fiber so as to form an optical image. A medical X-ray image detection apparatus comprising an X-ray image sensor formed in an outer container, wherein an X-ray intensity detection element is arranged in the outer container in proximity to the X-ray phosphor. It is characterized by being present.

In this X-ray image detecting apparatus, the X
It is preferable that the line intensity detection element is fixed on the fixed substrate of the solid-state image pickup element or is fixed to the back side of the fixed substrate with respect to the solid-state image pickup element.

The X-ray intensity detection element is connected to a control device including an integration circuit and a set value comparison circuit. This control device controls the output of the X-ray intensity detection element during the X-ray irradiation time by the integration circuit. The integrated X-ray dose signal is output and X is output by the comparison circuit.
Compare with the set X-ray dose to obtain the best quality of the line image,
When the dose signal becomes equal to the set X-ray dose, the X-ray tube current of the X-ray source is cut off.

In the medical X-ray image detecting apparatus of the present invention, the glass fiber is such that the axis of the glass fiber strand is substantially perpendicular to the phosphor screen of the X-ray phosphor.
It is preferable that the fluorescent surface is adhered to the fluorescent surface, and at least the front surface of the container on the X-ray incident side is formed of a soft X-ray absorbing material.

[0014]

According to the medical X-ray image detecting apparatus of the present invention, an optical image of the X-rays of the X-ray phosphor, which is transmitted through the object of interest, is projected on the image-pickup surface of the solid-state image-pickup element, and the image-pickup surface is imaged. A charge proportional to the amount of light corresponding to each pixel of the optical image is accumulated in each optical element of, and the accumulated charge of each optical element is converted into an electric signal, and finally an X-ray image is displayed on the monitor display. To be played as. Therefore, the degree of blackening of each pixel of the X-ray image on the display is almost proportional to the transmitted X-ray dose that stimulated each pixel on the phosphor screen.

In the present invention, X
An X-ray intensity detection element is arranged in the vicinity of the X-ray phosphor, and the X-ray intensity detection element electrically detects an X-ray transmitted through an object to be photographed or its vicinity, and detects the X-ray intensity of the X-ray. Generates an output signal proportional to intensity. This output is integrated during the X-ray irradiation time to calculate the irradiation X-ray dose, and when the X-ray irradiation reaches the same value compared with the set X-ray dose required to obtain the optimum image quality, if the X-ray irradiation is stopped, it will be displayed. In addition, the X-ray image is a good quality image having a proper degree of blackening.

Further, in the outer container of the apparatus of the present invention, if at least the X-ray incidence surface is formed of a soft X-ray absorbing material, high energy X-rays such as characteristic X-rays that have penetrated the tooth part and the surrounding tissues. The rays pass through the soft X-ray absorbing material and are projected on the fluorescent screen, but the scattered X-rays are absorbed by the soft X-ray absorbing material and cannot reach the fluorescent surface, so that they do not become a noise signal and are reproduced. The X-ray image obtained becomes a clear image.

As the soft X-ray absorber, a metal aluminum plate is used alone, or a rare earth metal is appropriately used together with a plastic plate material and plywood. Its thickness is
Although it is experimentally determined in consideration of the radiant X-ray intensity and the energy distribution of the X-ray source, it is suitable for a practical dental X-ray device that the thickness of the aluminum plate is 0.5 to 5 mm.

When one end surface of the glass fiber is a plane substantially perpendicular to the axis of the glass fiber strand and is joined to the phosphor screen, the optical image on the phosphor screen is transmitted to the image pickup surface of the CCD element. In this case, the resolution of the image does not deteriorate, and in particular, if the other end surface of the glass fiber is a plane substantially perpendicular to the axis of the glass fiber strand and is joined to the imaging surface of the CCD element, Even when the optical image projected on the image pickup surface is reproduced as an X-ray image on the monitor, the image resolution does not decrease and a clear image can be obtained.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1A and 1B are a plan sectional view and a vertical sectional view of a dental X-ray image detection apparatus according to one embodiment. A ceramic substrate 5 having a set of X-ray image sensors mounted thereon is fixed to an inner surface opposite to the incident direction) via an X-ray shielding material made of a lead plate.

The CCD substrate 4 is mounted on the ceramic substrate 5.
Of the glass element 3 is attached to the image pickup surface of the CCD element 4, and the fluorescent surface of the X-ray phosphor 2 is attached to the other end surface of the glass fiber 3. ing. In this example, the CCD element 4 and the glass fiber 3 and the X-ray phosphor 2 have a three-layer structure, and both optical end faces of the glass fiber 3 are planes substantially perpendicular to the axis of the glass fiber strand. Fluorescent screen and CC
It is joined to the imaging surface of the D element 4. X-ray phosphor 2
The X-ray transmitted through the front part 11 of the container 1 is irradiated,
A fluorescence image is emitted, the image is transmitted to the glass fiber 3, and is converted into an electric signal on the imaging surface of the CCD element 4. The CCD element 4 is connected to a control device 8 outside the device by a cable 7 including a lead wire 71.

On the ceramic substrate 5, an X-ray intensity detecting element 6 is fixed in close proximity to the phosphor 2 of the X-ray image sensor and arranged side by side in the lateral direction of the CCD element 4. The X-ray intensity detection element 6 is composed of a photo detection element 62 which is a phototransistor and an X-ray phosphor 61 applied on the light receiving surface thereof, and the upper surface of the X-ray phosphor 61 has a rectangular shape,
It is arranged substantially parallel to the upper surface of the phosphor 2. The X-ray transmitted near the target tooth portion is transmitted through the X-ray phosphor 61 to stimulate and emit light, and the emitted light is detected by the photodetector element 62.
An electric signal proportional to the light intensity is generated, and the signal is transmitted to the control device 8 outside the device by the cable 7 including the lead wire 71.

The X-ray intensity detecting element 6 is used for irradiation X of the phosphor 2.
To generate a signal representative of the mean value of the line intensities, X
It is arranged close to the phosphor 2 of the line image sensor, and in order to generate a signal indicating the average value of the intensity of X-rays within a certain area, the X-ray phosphor 61 is exposed to light of a certain size or more. Those having a surface area are used.

FIG. 2 shows the four outer corners of the X-ray image sensor,
A cross-sectional view of an X-ray image detection apparatus in which a total of four X-ray intensity detection elements 6a, 6b, 6c, 6d are arranged is shown. The average intensity of X-rays incident on the phosphor 2 of the image sensor is used for sampling. X-ray intensity detection elements 6a, 6b,
The outputs of the electric signals from 6c and 6d are simply added, for example, and input to the above integrating circuit so that averaged X-ray dose data is obtained.

FIG. 3 shows a portion of the opening 51 provided in the ceramic substrate 5 of the X-ray image sensor near the opening surface and C
A cross-sectional view of an X-ray image detection device in which an X-ray intensity detection element 6 is arranged on the back side of the CD element 4 is shown. The X-rays incident on the X-ray intensity detection element 6 are the phosphors 2 of the X-ray image sensor.
Since the X-rays are transmitted through the CCD element 4 and the X-rays, the transmitted X-ray dose at approximately the center of the X-ray image can be measured, and thus the reliability of the setting of the X-ray exposure time is improved.

The X-ray image detecting device comprises an X-ray intensity detecting element 6
The X-ray image sensor provided with is housed in the outer container 1, and the container 1 has a front surface 11, that is, a surface on the X-ray incidence side, including the side surface of the container, made of an aluminum plate. The aluminum plate is joined to the bottom portion 13 of the container 1 in a watertight manner. The container front portion 11 of this aluminum plate is a soft X-ray absorbing member,
The low-energy scattered X-rays generated when the X-rays pass through the tooth portion such as the tooth 92, the jawbone, and the soft tissue, are absorbed by the aluminum plate, and therefore hardly reach the CCD element. On the other hand, the main X-rays transmitted through the tooth portion are transmitted through the container 1 wall of the aluminum plate and projected on the phosphor 2 and the X-ray intensity detection element 6 of the X-ray image sensor.

FIG. 4 shows a mode of use of the dental X-ray image detection apparatus 10 of the present invention. The container 1 of the apparatus 10 is shown in FIG.
The image signal is reproduced as an image on the display of the monitor 81 by the control device 8 to which the cable 7 from is connected, and the image is printed on the paper by the printer 82 if necessary. Therefore, if the present apparatus 10 is held behind the target tooth 92 in the oral cavity that requires X-ray imaging and the X-ray of the small X-ray generator 9 is applied to the tooth 92, the transmitted X-ray of the tooth 92 is transmitted. The image is displayed on the monitor 81.

The control device 8 integrates the output signal from the X-ray intensity detection element 6 with respect to time and compares the settings, and an X and an output signal from the integration circuit and the comparison circuit and the comparison circuit.
A control circuit for shutting off the anode current of the X-ray tube is included, and if the X-ray transmission dose suitable for the analysis of the X-ray image of the tooth part is set and input in advance in the comparison circuit, it will be used during X-ray photography. Is cut off by the anode current of the X-ray tube when the transmitted X-ray dose detected by the X-ray intensity detection element 6 and integrated by the X-ray irradiation time in the integration circuit becomes equal to the set transmitted X-ray dose. ..
At this time, the image signal accumulated in the CCD element 4 or the storage element in the control device 8 is reproduced as an X-ray image on the display of the monitor 81.

The X-ray intensity detecting element 6 used in the X-ray image detecting apparatus of the present invention is not only a solid-state optical element having a wide fluorescent screen but also a solid-state element which is directly sensitive to X-rays without utilizing the fluorescent screen. Can also be adopted. Further, the amplification circuit and the integration circuit for processing the output from the X-ray intensity detection element 6 are
The X-ray intensity detection element 6 may be provided on the ceramic substrate of the X-ray image sensor.

[0030]

According to the X-ray image detecting apparatus of the present invention, an X-ray intensity detecting element for exposure adjustment for detecting the X-ray transmission intensity is arranged in the vicinity of the X-ray phosphor for X-ray image detection. Therefore, the X-ray irradiation time during X-ray photography, that is, the exposure time can be controlled by the X-ray dose calculated by integrating the intensity signal of the X-ray intensity detection element with the irradiation time. The X-ray image is always a high-quality image with a constant degree of blackening, which is useful for medical diagnosis, and since the failure of X-ray imaging due to overexposure or underexposure at the time of imaging is eliminated, the frequency of reimaging is reduced. It is possible to minimize the X-ray exposure dose of the patient.

Further, if the glass fiber is surface-attached to the phosphor screen so that the axis of the glass fiber strand is substantially perpendicular to the phosphor screen of the X-ray phosphor,
If the resolution of the X-ray image is improved, and at least the front surface of the container on the X-ray incident side is made of a soft X-ray absorbing material, the image quality of the X-ray image is degraded due to the soft X-rays scattered by the subject. Can be prevented, and the image quality can be made uniform by the above-mentioned exposure control, and the X-ray image can be made clear.

[Brief description of drawings]

FIG. 1 is a horizontal sectional view (A) and a vertical sectional view (B) of a dental X-ray image detection apparatus including an X-ray intensity detection element according to an embodiment of the present invention.

FIG. 2 is a view similar to FIG. 1 of another embodiment.

FIG. 3 is a view similar to FIG. 1 of the third embodiment.

FIG. 4 is an X-ray imaging system diagram using a dental X-ray image detection device.

[Explanation of symbols]

 1 container 2 X-ray phosphor 3 glass fiber 4 CCD element 5 ceramic substrate 6 X-ray intensity detection element 7 cable 8 control device 81 monitor 9 X-ray generator

[Procedure amendment]

[Submission date] November 22, 1991

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Fig. 2]

[Figure 3]

[Figure 4]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Norio Takahashi, No. 1126, 1126 Ichinomachi, Hamamatsu City, Hamamatsu Photonics Co., Ltd. (72) Inventor Takao Makino, 680, Higashihamanamicho, Fushimi-ku, Kyoto City Morita Manufacturing Co., Ltd. (72 ) Inventor Keisuke Mori 680 Higashihaman-cho, Fushimi-ku, Kyoto City Morita Manufacturing Co., Ltd.

Claims (4)

[Claims] 1. A medical device comprising an X-ray image sensor in which a fluorescent screen of an X-ray phosphor and an image pickup surface of a solid-state image pickup device are connected by a glass fiber so that an image can be optically formed in the outer container. In the X-ray image detecting apparatus, an X-ray intensity detecting element is arranged in the outer container in the vicinity of the X-ray phosphor.
Line image detection device. 2. The medical device according to claim 2, wherein the X-ray intensity detection element is fixed on a fixed substrate of the solid-state image pickup element or fixed on the back side of the fixed substrate with respect to the solid-state image pickup element. X-ray image detection device. 3. The glass fiber is surface-attached to the phosphor screen so that the axis of the glass fiber strand is substantially perpendicular to the phosphor screen of the X-ray phosphor.
Alternatively, the medical X-ray image detection device according to item 2. 4. The soft X-ray absorbing material is formed on at least the front surface of the container on the X-ray incident side.
The medical X-ray image detection apparatus described.