JPH04210048A - Radiation imaging apparatus - Google Patents

Abstract

PURPOSE:To achieve higher diagnosing performance by producing an image with exposure thereof optimized, an image with no adjustment of a radiation exposure or an image with adjustability thereof weakened to obtain two kinds of images by single irradiation of an object with radiation. CONSTITUTION:On the basis of a data of passage dose of a human body 4 to be detected with a detector 8, a control unit 9 determines an area where passage dose is excessive and a reduction adjustment level of radiation in the area along the length of a fan beam FB, and transmits a control signal to a modulator 10 corresponding to the results so that shutter members 11 of the modulator 10 are advanced into or retracted from a slit 2 to adjust radiation exposure to the human body 4. Therefore, a radiation image which is taken with the feeding back of a passage dose of the human body 4 to the radiation exposure by a structure of the detector 8, a control unit 9 and the modulator 10 is recorded on an accelerated phosphorescence phosphor panel 7. Such an adjustment of the radiation exposure enables the simultaneous photographing of a part easily transmitting radiation, such as lung and a part difficult in transmitting radiation, such as back bone and abdomen, in an easily observable manner, thereby achieving higher diagnosing performance.

Description

[Detailed description of the invention]

[00011

[Industrial Field of Application] The present invention relates to a radiation imaging device,
In particular, the present invention relates to a radiation imaging apparatus configured to detect the passing dose of a subject, feed back the detection result, adjust the radiation dose of a radiation beam irradiated to the subject, and perform imaging. [0002] [0002] A radiation imaging apparatus generally uses an X-ray tube as a radiation source and detects the radiation dose from the radiation source that has passed through an irradiated object (subject) to capture and record a radiation projection image. It consists of an imaging recording device such as a screen/film sensitive to radiation, a stimulable phosphor, and a semiconductor detector. [0003] By the way - in intra-shell radiological examinations, for example chest examinations, a typical patient has very large anatomical thickness variations and therefore exhibits very large X-ray attenuation variations. That is, various anatomical parts have large differences in X-ray transmittance. For this reason, when shooting using a screen/film with a narrow dynamic range, due to the narrow dynamic range of the screen/film that shows the test results, only a portion of the overall image is properly exposed, and the majority of the image is This results in overexposure or underexposure. [0004] On the other hand, in a system using a stimulable phosphor, although the stimulable phosphor has a relatively high dynamic range, the CRT used for visualization generally has a lower dynamic range than the stimulable phosphor. Due to the narrow dynamic range, exposure errors may also occur due to the narrow dynamic range. Therefore, for example, in X-ray photography for chest examination as mentioned above, areas that are easily transparent to X-rays, such as the lungs, and areas that are difficult to transmit, such as the spine and abdomen, are observed at the same time. It was not easy to display it in an easy-to-understand manner. [0005] For this reason, for example, a shutter member that variably controls the opening area for each region divided in the longitudinal direction is supported in and out of a fan beam forming slit formed in a collimator provided in front of the radiation source. , the fan beam obtained by passing through the slit is scanned in a direction perpendicular to the longitudinal direction of the fan beam to scan the subject and record the image on the imaging surface provided behind the subject. A detector is provided to detect the radiation dose (dose passing through the subject), and the amount of aperture by the shutter member is controlled so as to obtain an appropriate exposure amount based on the detection signal from the detector, thereby controlling the radiation dose irradiated to the subject. There is a configuration that allows adjustment (see Japanese Patent Application Laid-Open No. 129034/1983). [0006]

[Problems to be Solved by the Invention] However, in the configuration described above in which the detection result of the radiation dose that has passed through the object is fed back to the irradiated radiation beam to take an image, for example, in medical applications, the density (passage The irradiated radiation dose is adjusted to areas where the radiation dose (radiation dose) should be lower than that of the normal area, and adjustments are made to reduce the difference in concentration (passing dose) between the normal area and the diseased area. , the diagnostic performance based on the obtained images may be deteriorated. [0007] For example, in a human chest, if one lung suffers from pneumonia and water accumulates in a relatively wide area, the amount of radiation passing through the diseased area is reduced compared to the normal area, but the irradiation Due to the radiation dose adjustment control, the irradiation dose to the lesioned area of one lung is increased (adjustment is made to decrease the radiation dose to the surrounding normal area), and the adjustment of the irradiation radiation dose makes the lesion area clearer. In some cases, this may result in poor diagnostic performance. [0008] The present invention has been made in view of the above-mentioned problems, and it is possible to obtain an image with appropriate exposure by feeding back the passing dose of the subject to the dose of the irradiation radiation beam, and to adjust the irradiation radiation dose. Based on the adjusted image, an image without adjusting the irradiation radiation dose or an image with a weakened degree of adjustment is obtained, and the above two types of images are obtained by one radiation irradiation to the subject, for example. The purpose of medical radiological images is to improve diagnostic performance. [0009]

[Means for Solving the Problems] Therefore, a radiation imaging apparatus according to the present invention is constructed as shown in FIG. Figure 1
In this method, the passing radiation dose detection means outputs a detection signal corresponding to the radiation dose that has passed through the subject, and the radiation dose adjustment means variably adjusts the radiation dose of the radiation beam irradiated to the subject based on the detection signal. [00101] Then, the imaging means detects the radiation dose that has been variably adjusted by the radiation dose adjustment means and has passed through the subject, and converts it into a radiation image signal. Further, the adjustment level pseudo conversion means processes the radiation image signal obtained by the imaging means based on the radiation adjustment amount data by the radiation dose adjustment means, so that the level of the radiation adjustment amount is changed in a pseudo manner. Get the image.

[0011]

[Operation] According to this configuration, the radiation dose of the radiation beam irradiated to the subject is variably adjusted based on the detection signal corresponding to the radiation dose that has passed through the subject, and the radiation beam with the variably adjusted radiation dose passes through the subject. The amount is sensed by the imaging means and converted into a radiographic image signal. [0012] Therefore, depending on the imaging means, a radiation image with a radiation beam whose radiation dose is variably adjusted can be obtained, but here, a radiation image obtained without adjusting the radiation dose is based on the radiation adjustment amount data. Since it can be estimated, by processing the radiation image signal based on the data of the radiation adjustment amount, for example, the degree of variable adjustment of the radiation dose may be weakened, or what would be obtained if the radiation dose was not variably adjusted at all. It is possible to obtain an image signal. [0013] Therefore, based on the radiation image obtained by adjusting the radiation dose, it is possible to obtain a radiation image in which the level of the radiation adjustment amount is changed in a pseudo manner, together with the radiation image,
For example, in medical applications, when radiation images obtained by variable adjustment of radiation dose alone are insufficient for diagnosis, it is possible to provide images with pseudo-variable adjustment levels of radiation dose, improving diagnostic performance. This can be improved. [0014]

EXAMPLES The present invention will be explained in detail below. In FIG. 2 showing the configuration of a radiation imaging device according to an example,
A first collimator 3 having a slit 2 opened with the horizontal direction as the longitudinal direction is provided at a position in front of the X-ray tube 1 as a radiation source. This first collimator 3 is moved in parallel in the vertical direction in the figure by an actuator (not shown) controlled by a control unit 9, and as a result of this parallel movement, a fan beam F of radiation is formed in the slit 2.
B (the radiation beam) is made to perform a scanning motion in a direction perpendicular to its longitudinal direction. Note that a stepping motor, an electromagnet, or the like may be used as the actuator. [0015] A human body 4 as a subject is positioned at the scanning position of the fan beam FB formed by the slit 2 of the first collimator 3, and the fan beam FB that has passed through the human body 4 is passed behind this human body 4. A second collimator 6 having a horizontally long rectangular opening 5 is provided. The second collimator 6 is also moved in the vertical direction in the figure as the first collimator 3 is moved in the vertical direction by an actuator (not shown) controlled by the control unit 9, and the fan beam FB that has passed through the human body 4 is 5
, and reaches a stimulable phosphor panel 7 serving as an imaging means. [0016] Further, the opening 5 of the second collimator 6 is provided with an X-ray transparent line type detector 8 as a passing radiation dose detection means for detecting the X-ray dose. This line type detector 8 has an independent X
It is equipped with radiation detection elements, each of which detects the amount of radiation that has passed through the human body 4, and outputs a detection signal corresponding to the detected radiation amount to the control unit 9. This allows for the creation of a longitudinal pass-through dose profile. [0017] Here, the detector 8 absorbs a portion of the radiation that has passed through the human body 4 and detects the absorbed radiation level, and the portion of the radiation that has passed through the human body 4 that is not absorbed by the detector 8 Since the stimulable phosphor panel 7 is irradiated with the passing radiation, radiation image information can be recorded while detecting the passing radiation. [0018] In order to variably adjust the X-ray beam irradiated to the subject based on the detection signal corresponding to the amount of X-rays passing through the subject (human body 4), the line type detector 8
It is sufficient to be able to detect ultra-low spatial frequency components of the object structure.
The number of detection elements is preferably in the range of 10 to 500,
Practically speaking, 30 to 200 pieces is particularly preferable. Furthermore, the number of data in the scanning direction (vertical direction) of the detector 8 is still preferably 30 to 200 than 10 to 500, and even if the number of data is reduced to the required number by averaging processing etc. good. [00191 Furthermore, in the slit 2 of the first collimator 3, the opening area of the slit 2 is variably controlled for each region divided into a plurality of regions in the longitudinal direction, so that the dose passing through the slit 2 can be controlled at a plurality of locations in the longitudinal direction. A modulator 10 is provided as a radiation dose adjusting means for variable adjustment. As shown in FIG. 3, the modulator 10 includes a plurality of plate-shaped shutter members 11 made of a radiation absorbing material. Each of the shutter members 11 is supported so as to be movable in the width direction of the slit 2 approximately along the end surface of the first collimator 3 on the X-ray tube 1 side. They are placed adjacent to each other. Each of the shutter members 11 is provided with an actuator at its base end, and is driven by the actuator to move forward and backward independently of each other in the moving direction. [00201 Therefore, by selectively moving the shutter member 11 in a direction that covers the opening of the slit 2, the opening area of the slit 2 is changed in the longitudinal direction, and the passing dose in the longitudinal direction of the slit 2 (irradiation dose to the human body 4) is reduced. ), and if it is configured with approximately the same number of shutter members 11 as the number of sensor elements arranged in parallel in the longitudinal direction of the opening 5 of the detector 8, each sensor element of the detector 8 The radiation dose of the fan beam FB irradiated to the human body 4 can be controlled according to the detected dose by the fan beam FB. [00211 Note that the shutter member 11 constituting the modulator 10 may be moved linearly in the width direction of the slit 2 as described above, or may be moved by swinging or rotating. Alternatively, the opening area of the slit 2 may be changed in the longitudinal direction of the slit 2. Further, the absorption rate of radiation may be different depending on the portion of the shutter member 11. [0022] The stimulable phosphor panel 7 is irradiated with a fan beam F from a radiation source via a modulator 10.
Energy according to the radiation transmittance distribution of the human body 4 with respect to B is accumulated and recorded in the photostimulable layer to form a latent image of the human body 4 (subject). The stimulable phosphor panel 7 has a stimulable phosphor layer provided on a support by vapor deposition of the stimulable phosphor or coating of a stimulable phosphor paint. The body layer is shielded or covered by a protective member to block out environmental influences and damage. As the stimulable phosphor material, for example, a material as disclosed in Japanese Patent Application Laid-Open No. 61-72091 or Japanese Patent Application Laid-Open No. 59-75200 is used. [0023] Here, the control unit 9 controls the detector 8
By controlling the modulator 10 based on the data (low spatial frequency component) of the passing dose of the human body 4 detected by the stimulable phosphor panel 7, the radiation dose irradiated to the human body 4 is adjusted. Record images. That is, the control unit 9 determines, based on the data of the passing dose of the human body 4 detected by the detector 8, the area where the passing dose is excessive in the longitudinal direction of the fan beam FB and the amount of radiation reduction adjustment in the area. (or the area where the passing dose is too small and the amount of radiation increase adjustment in the area) and sends a control signal corresponding to this determination to the modulator 10, thereby controlling each shutter member 11 of the modulator 10. It moves forward and backward into the slit 2 to adjust the irradiation dose to the human body 4. [0024] Therefore, the stimulable phosphor panel 7 includes a detector 8. Control unit 9. Due to the configuration of the modulator 10, the passing dose of the human body 4 is fed back to the irradiation dose, and the captured radiation image is recorded, and by adjusting the irradiation dose, it is possible to adjust the radiation dose to a part such as the lungs that is easily transmitted by radiation.
Areas that are difficult for radiation to pass through, such as the spine and abdomen,
At the same time, images are captured in a state that is easy to observe. [0025] On the other hand, reading of image information from the stimulable phosphor panel 7 on which radiation image information of a subject is stored and recorded as described above is performed as follows. That is, the stimulated excitation light source (gas laser, solid-state laser, semiconductor laser, etc.) 21 generates an excitation light beam whose emission intensity is controlled, and the excitation light beam is transmitted to the luminescent light source in which radiation image information of the subject is accumulated and recorded. The stimulable phosphor panel 7 is scanned, and the radiation energy (latent image) accumulated in the stimulable phosphor panel 7 is emitted as fluorescence (stimulated luminescence). [0026] The photoelectric conversion device 22 includes a filter 23 that passes only the fluorescence (stimulated luminescence) emitted by scanning the stimulable phosphor panel 7 with an excitation light beam. A radiation image signal is obtained by photoelectrically converting the received light into a current signal corresponding to the incident light. The analog radiation image signal photoelectrically read by the photoelectric conversion device 22 is sequentially A/D converted by an A/D converter (not shown).
It is output to the image processing device 24 as a digital radiation image signal. The image processing device 24 performs various types of image processing (gradation processing, frequency processing, etc.) on the digital radiation image signal to make it suitable for diagnosis, and then outputs it to the radiation image reproduction device 25. [0027] The radiation image reproducing device 25 is a printer or C
It is a monitor such as RT, which inputs the digital radiation image signal processed by the image processing device 24, and visualizes the photographed radiation image as a hard copy or a playback screen. still,
Along with the radiation image reproduction device 25 or instead of the radiation image reproduction device 25, a storage device such as a semiconductor storage device (
A filing system) may be provided to store radiation image signals output from the image processing device 24. [0028] The image processing device 24 has a function as an adjustment level pseudo conversion means in this embodiment, and performs known processing such as gradation processing and frequency processing.
Signal processing is performed based on the adjustment amount of radiation according to the present invention, and in this embodiment, in addition to the radiation image obtained by adjusting the irradiation dose with the modulator 10, the radiation image is converted into adjustment amount data. By performing signal processing based on this, it is possible to obtain a radiation image even when the radiation dose is not adjusted. [0029] Radiation adjustment amount data storage that stores the detection signal from the detector 8 or the control signal of the modulator 10 based on the detection signal as radiation adjustment amount data for signal processing based on the radiation adjustment amount data. A unit 26 is provided, and an image processing device 24
is obtained when the digital radiation image signal input from the photoelectric conversion device 22 is processed based on the adjustment amount data of irradiation radiation at the time of imaging stored in the radiation adjustment amount data storage unit 26, and the radiation is not adjusted. A radiographic image that is predicted to be simulated is obtained. [00301 FIG. 4 is a block diagram of the configuration of the image processing device 24, and the radiation image signal obtained by adjusting the irradiation radiation dose input from the photoelectric conversion device 22 is temporarily stored in the original image data storage unit 27. Ru. The image restoration processing unit 28 converts the radiation image signal captured by adjusting the irradiation dose stored in the original image data storage unit 27 based on the adjustment amount data stored in the radiation adjustment amount data storage unit 26. By processing the signals using the irradiation method, a pseudo image can be obtained without adjusting the irradiation dose. [00311 The radiation image signal processed and obtained by the image restoration processing section 28 is stored in the restored image data storage unit 29. Here, the state of the signal processing performed by the image restoration processing section 28 is shown in the flowchart of FIG. In the flowchart of FIG. 5, first, step 1
(In the figure, it is referred to as Sl. The same applies hereinafter.) In step 2, the image data for each pixel stored in the original image data storage unit 27 is read out, and in the next step 2, the image data read out in step 1 is used. Radiation adjustment amount storage unit 2 stores radiation adjustment amount data corresponding to the same image area.
Read from 6. [0032] Then, in step 3, the original image data is processed based on the radiation adjustment amount data. Specifically, for example, if the image data was obtained in an image area where the adjustment was made to reduce the radiation dose by 50%, if the radiation dose was not adjusted, the image data would be adjusted. If the image data corresponds linearly to the passing dose, doubling the image data will reduce the radiation to 50% in signal processing. This allows image data to be obtained without weight loss. That is, by adding on the signal the amount by which the irradiation dose has been reduced by the modulator 10, a radiographic image (restored image) obtained when the irradiation dose is not adjusted in signal processing is obtained in a pseudo manner. It is something. [0033] The image data restored in step 3 is stored in the restored image data storage unit 29 in step 4.
are stored sequentially. In step 5, it is determined whether or not the pixel-by-pixel restoration process has been completed for all image data as described above, and if it has not been completed, step 1 is performed again.
Return to step 1 and repeat steps 1 to 4. [0034] As described above, an image signal obtained by adjusting the irradiation dose stored in the original image data storage unit 27;
The image signal obtained by processing the image signal and stored in the restored image data storage unit 29 without adjusting the irradiation dose refers to the image signal obtained by processing the image signal and storing it in the restored image data storage unit 29. After being applied, it is output to the radiation image reproduction device 25 via the reproduction interface 31 and visualized. [0035] Therefore, the radiation image reproducing device 25 receives the original image obtained by adjusting the irradiation dose and the image corresponding to the case where the irradiation dose is not adjusted, which is obtained by signal processing this image. The radiation image reproducing device 25 reproduces these two images obtained by photographing the same human body 4 side by side on a CRT or film as shown in FIG. [0036] In this way, in this example, although the radiation dose was adjusted and imaging was performed so that the radiation image was obtained in which the areas where it is easy for radiation to pass and the areas where it is difficult for radiation to pass were simultaneously easy to observe. On the other hand, an image is obtained in the case where the irradiation dose is not adjusted based on the obtained image, and the necessity and effect of performing such processing will be described below. [0037] That is, by adjusting the irradiation radiation dose using the modulator 10 and photographing, the exposure level can be converged to an appropriate range without being affected by the difference in thickness or radiation absorption in the photographed part of the subject, as described above. However, on the other hand, such adjustment of the radiation dose may obscure a lesion that appears clearly when not adjusted. [0038] For example, if a lesion occurs in a small area in the lungs, it will not be adjusted by the modulator 10, but if the lesion spreads over a wide area, the amount of radiation passing through the lesion will decrease. Therefore, when adjusting the radiation dose using the modulator 10 in the direction of reducing the radiation dose, the irradiation dose to the surrounding normal lung parts should be adjusted so that the radiation dose at the lesion area increases compared to other areas. Control is performed to reduce the amount, and as a result, the difference between normal lungs and diseased lungs becomes unclear on the reproduced image. [0039] In addition, when the modulator 10 normally allows only a portion of the X-rays to pass through, and the modulator 10 is opened as necessary to increase the X-ray dose, it is possible to treat lesions where the amount of radiation passing through is reduced. If the lung is present over a wide area, the modulator 10 will be opened to increase the dose at the lesion to compensate for the decrease in the passing dose at the lesion. The difference between this and the diseased lung becomes unclear. [0040] However, as in this example, if both an image obtained by adjusting the irradiation dose and an image obtained when the irradiation dose is not adjusted are obtained, the radiation It is possible to simultaneously visualize the parts where it is easy to pass and the parts where it is difficult to pass, and to clearly diagnose the presence of the lesion based on the image when the irradiation dose is not adjusted. [00411]However, in order to obtain the above two images, it is not necessary to capture each image separately, and two types of images can be obtained with one radiation irradiation, which reduces the amount of radiation exposure of the human body 4, which is the subject. Growth can be suppressed. In the above embodiment, the image obtained by adjusting the irradiation dose is subjected to signal processing to obtain an image signal without any adjustment, but an image with a weakened degree of adjustment is obtained by signal processing. In this case, for example, when the signal level can be achieved without adjustment by doubling the signal from the adjustment amount, if control is performed to increase the signal level by 1.5, for example, an image with the adjustment degree halved can be obtained. be able to. Therefore, it is possible to change the degree of adjustment into a plurality of types through signal processing and obtain a plurality of images in which the degree of adjustment of the irradiation dose is changed in a pseudo manner with respect to the original image. [00421 Furthermore, when obtaining an image with a weakened degree of adjustment as described above through signal processing, it is also possible to arbitrarily set the degree of weakening of the degree of adjustment by external operation. It is also easy to make it possible to visualize only the image. Furthermore,
The image signal obtained by adjusting the irradiation dose and the data stored in the radiation adjustment amount data storage unit 26 are stored as a pair, and the image signal is read again based on the adjustment amount data when necessary during playback. It is also possible to obtain other images with varying degrees of processing. [00431 In the above embodiment, the stimulable phosphor panel 7 was used as the imaging means, but instead of the stimulable phosphor panel 7, a radiation sensitive film or a semiconductor detector may be used. When recording images on film,
After photoelectrically converting the radiation image of the film into an electrical image signal, processing based on the radiation adjustment amount data as described above is performed. In addition, when a semiconductor detector is used instead of the stimulable phosphor panel 7, the image data obtained from the semiconductor detector is adjusted to the passing dose level (low spatial frequency component) detected by the detector 8 at that time. The radiation adjustment amount data storage unit 26 can be omitted. [0044]

[Effects of the Invention] As explained above, according to the present invention, by feeding back the passing dose of the subject to the irradiation dose and imaging, even if the radiation passing rate differs greatly in each part of the subject, it can be easily observed at the same time. In addition to being able to visualize the image, it is also possible to obtain a radiation image in which the level of the radiation adjustment amount is artificially changed from the image obtained by adjusting the irradiation dose as described above. It is now possible to clearly confirm areas that would otherwise become clear (for example, large-area lesions in medical applications), but radiographic images with simulated changes in the level of radiation adjustment amount as described above are Since it is obtained by processing the signal of the captured image while adjusting the dose, there is an advantage that there is no need to separately perform imaging to obtain images with different adjustment levels.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention.

FIG. 2 is a system schematic diagram showing an embodiment of the present invention.

FIG. 3 is a partially enlarged perspective view showing the detailed structure of the modulator shown in FIG. 2;

FIG. 4 is a block diagram showing the detailed configuration of the image processing device shown in FIG. 2;

FIG. 5 is a flowchart showing how image restoration is controlled in the embodiment.

[Explanation of symbols]

I X-ray tube 2 Slit 3 First collimator 4 Human body 5 Opening 6 Second collimator 7 Exhaustible phosphor panel 8 Detector 9 Control unit 10 Modulator 11 Shutter member 21 Stimulating excitation light source 22 Photoelectric conversion device 23 Filter 24 Image processing device 25 Radiation image reproduction device 26 Radiation adjustment amount data storage unit 27
Original image data storage unit 28 Image restoration processing section 29 Restored image data storage unit

[Figure 2]

Claims (1)

[Claims] 1. Passing radiation dose detection means for outputting a detection signal corresponding to a radiation dose that has passed through a subject; and a detection signal output from the passing radiation dose detection means that indicates the radiation dose of a radiation beam irradiated to the subject. a radiation dose adjusting means for variably adjusting based on the radiation dose adjusting means; an imaging means for detecting the radiation dose variably adjusted by the radiation dose adjusting means and having passed through the subject and converting it into a radiation image signal; and radiation adjusting means by the radiation dose adjusting means. adjustment level pseudo conversion means for obtaining a radiation image in which the level of the radiation adjustment amount is changed in a pseudo manner by processing the radiation image signal obtained by the imaging means based on the amount data; A radiation imaging device characterized by: