JPS6345219B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an X-ray imaging device.

In order to increase the contrast of a film image obtained by X-ray irradiation, a method has been proposed in which an X-ray beam is irradiated in a slit shape and the slit beam is moved while recording the X-ray image on the film.
This method improves object contrast, but since the recording medium is film, the dynamic range is narrow and development work is required.

On the other hand, one method to improve the dynamic range is to use a large number of detector groups arranged in a row, e.g.
This method uses a detector consisting of a Xe gas ionization chamber, a scintillator, and a photodiode to detect the light, convert it into an electrical signal, and display the image on a cathode ray tube. This method is used as a positioning technique for third-generation X-ray CT devices. However, this method requires approximately 500 detectors and has insufficient resolution. To increase the resolution, it is necessary to reduce the aperture area of the detector and increase the number of detectors, but this has technical problems such as manufacturing density and reduced sensitivity. . Furthermore, since a current-voltage converter, an integrator, etc. are connected after each detector, the cost becomes very high as the number of detectors increases.

Further, all of the above-mentioned devices have the disadvantage that they are only used for X-ray photography and cannot perform fluoroscopy.

Furthermore, the level of the detected value may differ depending on the thickness of the object. As a result, the processing accuracy of detected values was sometimes adversely affected.

An object of the present invention is to provide an X-ray imaging apparatus that increases the detection output value when the detection output value decreases more than necessary due to the thickness of the subject or the like.

The gist of the present invention resides in that the detector is constituted by an integral type solid-state array sensor, and that the driving frequency of the array sensor can be changed.

FIG. 1 shows an embodiment of the present invention. An X-ray beam moving slit 11 is selectively inserted between the subject 2 and the X-ray source (tube) 1. An X-ray beam slit 12 is selectively inserted between the table 3 and the X-ray intensifier 4. This X
The moving slits 11 and 12 for the ray beam are the X-ray source 1.
It has the role of narrowing down the radiation X-rays from the The X-ray beam moving slits 11 and 12 are the controller 1.
Slit drive mechanism 1 driven by receiving the output of 7
4 and 15, the slit position is moved along the scanning direction. Furthermore, during fluoroscopy, the X-ray beam moving slits 11 and 12 are removed from the X-ray path, and the X-rays emitted from the X-ray source 1 are directly irradiated onto the subject 2 without passing through the slits. The transmitted radiation enters the X-ray image intensifier 4 as it is. The removal of the X-ray beam moving slits 11 and 12 from the X-ray path is also performed by the slit drive mechanisms 14 and 15. A half mirror 8 which receives the output of the image intensifier 4 via the objective lens 5 is driven by a mirror drive circuit 9. The mirror drive circuit 9 causes the output of the image intensifier 4 sent through the objective lens 5 to be taken into the television image pickup tube (TV camera) 10 through the X-ray television eyepiece 6 during fluoroscopy. Furthermore, in order to cause the array sensor 13 to detect the output of the image intensifier 4 sent through the objective lens 5 during photographing,
Controls the half mirror 8.

The array sensor 13 consists of an integral type solid state array sensor. Therefore, an integrating circuit is not required for its output. The array sensor 13 is controlled by a drive mechanism 16 as shown by the arrow in synchronization with the slits 11 and 12.

The monitor TV 22 receives fluoroscopic information in the television image pickup tube 10 sent via the switch 24 and the X-ray television camera controller 20, and the image processing device 2.
The image processing information from 1 is selectively displayed by switching the switch 25. Image processing device 21
The switch 23 connects the output of the array sensor 13 and the output of the controller 17 sent out via the AD converter 18, and the output of the TV image pickup tube 10 sent out via the switch 24 and the AD converter 19. Selectively capture via. Image processing device 2
1 performs processing such as processing for freely adjusting the density curve, processing that enables control of spatial frequency characteristics, and numerical analysis processing.

Next, the operation will be explained. This embodiment has two operation modes. The first is the X-ray fluoroscopy mode, the second
is the X-ray photography mode. In X-ray fluoroscopy mode,
The necessary affected area of the subject is searched and the location to be imaged is determined. In the X-ray imaging mode, X-ray imaging is performed at the imaging location determined in the X-ray fluoroscopy mode.

First, under normal X-ray fluoroscopy conditions, slit 1
1 and 12 are retracted out of the field of view of the X-ray beam by drive mechanisms 14 and 15, and mirror 8 is controlled by a mirror drive circuit 9, and the output image of the image intensifier 4 is sent to the television camera. 10. The fluoroscopic image is observed on the monitor 22 through the switch 24, the X-ray television controller 20, and the switch 25. Through this observation, the appearance and position of the fluoroscopic image can be visually observed, and the location and conditions necessary for imaging can be confirmed.

Next, enter shooting mode. In the photographing mode, the X-ray slits 11 and 12 are first moved by the drive mechanisms 14 and 15 so as to be within the field of view of the X-ray beam. Furthermore, the half mirror 8 is controlled by a mirror drive circuit 9 and is driven to send an output image from the objective lens 5 to the array sensor 13.
Furthermore, slits 11, 12 and array sensor 13
are controlled by drive mechanisms 14 and 15 to move linearly (indicated by arrows) in synchronization with the optical axis. However, the slit 11 performs rotational movement.

The array sensor 13 is an integral solid state array sensor in which a large number of photodetectors are arranged in one dimension, and a typical example is the G series array sensor manufactured by Reticon. Equivalently, this G series array sensor consists of linearly arranged photodiodes that perform light detection, a capacitor compatible with the photodiodes that accumulates the output of the photodiodes, a scanning changeover switch, and a photodiode-compatible capacitor that accumulates the output of the photodiodes. It consists of a shift register that controls switching of the scanning switch. The above capacitor plays the role of an integrating capacitor.

The array sensor 13 moves in optical axis synchronization with the slits 11 and 12, and the output of each channel (for example, 1024 channels) of the sensor itself is sequentially read out. The read data is AD converted by the AD converter 18 and stored in the memory within the image processing device 21. The data stored in the memory is processed such as being arranged in an orderly manner in accordance with the position of each channel in real space on the surface of the image intensifier 4 to obtain a necessary X-ray fluoroscopic image. The processing contents within the image processing device 21 are as follows:
In order to freely adjust the density curve, processing is performed like adjusting the window and level in a CT device. Furthermore, processing and numerical analysis processing are performed to enable control of spatial frequency characteristics.

The processing results of the image processing device 21 are sent to the monitor 22 and displayed, or stored in an auxiliary memory or the like, as necessary. The image processing device 21 receives and stores the video signal from the TV camera 10 via the switch 24 and the AD converter 19, and performs necessary processing. The processing results are displayed on the monitor 22.

According to this embodiment, the following effects are obtained.

(1) The conventional slit photography method can be used, and
At this time, compared to the conventional method of using film, it is possible to capture, store, and process data without using film, making it possible to obtain an extremely wide range of X-ray images. Furthermore, since an array sensor is used in this case, the configuration is simplified.

(2) To enable fluoroscopy and imaging, and to increase sensitivity, use an X-ray image intensifier, distribute its output light, and connect it to a TV camera.
We were able to achieve a configuration in which the array sensor was irradiated.
Furthermore, we were able to create a digital imaging system with fluoroscopic and photographic functions.

(3) Since an integral type solid-state array sensor is used as the array sensor, it is possible to achieve miniaturization and to easily achieve high resolution. Current CT scanography has a resolution of around 500 lines, but using an array sensor can achieve a resolution of more than 1000 lines.

(4) By installing a line sensor behind the X-ray image intensifier, the zoom mechanism of the X-ray image intensifier can be used.
High resolution can be achieved if the field of view is small. In contrast, this is not possible with CT scanography.

(5) The digital processing function for array sensor output processing is not limited to array sensor output.
TV output signal processing is also possible, resulting in
Dynamic (such as dynamic subtraction) or high-speed digital images can be obtained.

(6) Compared to other scanography, the exposure dose can be reduced.

A case study in which the array sensor is Reticon's 1024G will be explained in detail. FIG. 2 shows the results of measuring the output Vout of each channel while changing the intensity of the incident light under the condition that the frequency of the driving pulse for each channel is constant. According to this characteristic, it becomes clear that when the intensity of the incident light is less than 10 ³ , the output Vout is approximately proportional to the incident light, and when the intensity is 10 ³ or more, the output Vout is saturated. Generally, in order to obtain an image with a good S/N ratio, it is necessary to obtain a large output from the detector. On the other hand, when the frequency _c of the driving pulse is changed while the intensity of the incident light is constant, the detector output becomes inversely proportional to the frequency (that is, naturally proportional to the integration time T). An example of the characteristics at this time is shown in FIG.

Therefore, even if the thickness of the object is large and a sufficient amount of light cannot be obtained, it is possible to increase the signal output by lowering the driving frequency and obtain an image with a good S/N ratio. Therefore, in the present invention, the analog output of each channel corresponding to the first one or several channels of the X-ray slit beam is measured at the initially set driving frequency, and the X-ray slit beam is adjusted based on the output value. The moving speed, that is, the driving frequency, is automatically set, and the subsequent output is taken into the image processing device as regular image data.

FIG. 4 is a diagram showing an embodiment of the present invention. The configuration is characterized by the provision of a switch 26 and an output measuring circuit 27, and the other configurations are the same as in FIG. The switch 26 is a switch that selects whether to send the output of the array sensor 13 to the AD converter 18 or to the output measurement circuit 27. Array sensor 13
When checking whether the output of the circuit has reached a predetermined value, the switch 26 is switched to the output measuring circuit 27 side. By this switching, the array sensor 13
Measurement circuit 2 outputs the output of one detection element at the end of
7. The measured value by the output measurement circuit 27 is sent to the controller 17.
In step 7, a check is made to see if the measured value has reached the required reference value for output detection. If the reference value is reached, the control signal (drive frequency) from the controller 17 to the drive mechanisms 14, 15, 16 remains unchanged from the previous time. If it is below the reference value, the controller 17 sets a new drive frequency to lower the drive frequency, and drives the drive mechanisms 14, 15, 16 in accordance with the new set value.

After completing the setting of the new set value, the switch 26 is operated to input the output of the array sensor 13 to the AD converter 18.

Figure 5 shows a time chart. When the start pulse is turned on as shown in FIG. 5, an output check and a normal output are taken in during this period. First, as shown in 2, the switch 26 is switched to the output measurement circuit 27 side under the condition setting preliminary measurement section T'. In this interval T', the frequency of the drive pulse follows the previously set frequency (wavelength τ') as shown in 3. In this interval T', as shown in 4, N channel data is output to the measurement circuit 2.
7. The measured value of the output measuring circuit 27 is sent to the controller 17, and its output value V'out is compared with a reference value. As a result of the comparison, if it is smaller than the reference value, the drive frequency is set small (wavelength τ), and the switch 26 is thereafter switched to the AD converter side.

According to this embodiment, it was possible to make the variation in output uniform depending on the thickness of the subject 2. Note that the switch 26 may be switched to the output measurement circuit 27 side basically at any time period. That is, even during the scanning process, a switch may be switched to perform an output check as appropriate. Further, although the output of the array sensor during checking is determined from a specific detection element, the number of the detection element (channel) is not necessarily specified and may be arbitrary. Furthermore, the output of not only one detection element but also a plurality of detection elements may be checked.

According to the present invention, array sensor output without output fluctuation could be reliably obtained.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of the X-ray imaging device, Figures 2 and 3
The figure is a characteristic diagram of the array sensor, FIG. 4 is an embodiment of the present invention, and FIG. 5 is a time chart. 1...X-ray source, 11, 12...Slit, 13
...Array sensor, 26...Switch, 27...
Output measurement circuit.

Claims (1)

[Claims] 1. X-rays emitted from an X-ray source are made into a slit-shaped beam and irradiated onto the subject, and the transmitted output obtained from the subject due to the irradiation is inputted to an X-ray image intensifier, and the image intensifier The output of the slit-shaped beam is made incident on an integral solid-state array sensor, the position of incidence of the slit-shaped beam on the object is moved in accordance with the scanning order, and the array sensor is optically synchronized with the slit-shaped beam. In an X-ray imaging apparatus in which the output from the array sensor is captured and processed by an image processing device, there is an output check section in which the output of the array sensor is checked and a processing section in which the output of the array sensor is captured and processed. The output value of the array sensor is measured during the output check period, and when the measured value becomes smaller than a predetermined reference value, an output value larger than the reference value is obtained. An X-ray imaging apparatus that changes the drive frequency of the array sensor, drives the array sensor according to the drive frequency during a processing period, and automatically inputs and processes the output into an image processing device.