JP2009240568A - Radiographic imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce an exposed dose applied to a subject, compared to a conventional radiographic imaging apparatus, in a radiographic imaging apparatus prepared for long-length imaging of a range larger than a detecting range of a radiation image detecting means. <P>SOLUTION: A computer 4 for controlling the entire radiographic imaging system 1 relates a site to be imaged of the subject P and a position of a radiographic imaging part 15 and varies imaging conditions for each site of the subject P. When a plurality of radiation images obtained by imaging are synthesized, the computer 4 synthesizes the plurality of radiation images after approximating density or contrast of each image by adjusting the density of the radiation image for each of the plurality of radiation images to be synthesized. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a radiographic image capturing apparatus that supports long imaging in a range wider than the detection range of a radiographic image detecting means.

  2. Description of the Related Art Conventionally, in the medical field and the like, various types of radiation detectors that record a radiation image related to a subject by irradiation with radiation that has passed through the subject have been proposed and put into practical use.

  As the radiation detector, for example, as described in Patent Document 1, there is a radiation detector using a semiconductor such as amorphous selenium that generates a charge by irradiation of radiation, and as such a radiation detector, a so-called radiation detector is used. An optical reading type and a TFT reading type have been proposed.

  If such a radiation detector is used, image information obtained by imaging can be acquired as digital data, so that affinity with a diagnosis support apparatus using a computer can be increased.

  For example, as described in Patent Literature 2-4, in order to perform long imaging in a range wider than the detection range of the radiation image detection means, the radiation detector is moved in parallel along the radiation detection surface. It has been proposed to shoot a plurality of times at different locations and then combine the obtained images to generate an image in a wider range than the detection range of the radiation detector.

Furthermore, in the apparatus that performs imaging by moving the radiation detector in this way, in order to prevent the subject from coming into contact with the radiation detector, a screen arranged between the radiation detector and the subject has also been proposed. ing.
JP 2000-105297 A JP 2005-270277 A JP 2006-500126 A JP 2004-358254 A Noto 3118190

  When performing long shooting as described above, since it is necessary to synthesize a plurality of images, conventionally, shooting was performed with the same shooting conditions such as radiation irradiation intensity and time for all images to be shot. . This is because if the imaging conditions such as radiation irradiation intensity and time change, the density of the image changes, making it difficult to properly combine the images.

  For this reason, it is desirable to reduce the exposure dose as the optimal radiation exposure time for each part of the subject, but in the case of long imaging, the imaging conditions must be the same for each imaging. It was difficult to reduce the exposure dose to subjects.

  The present invention has been made in view of the above circumstances, and in a radiographic imaging apparatus that supports long imaging in a range wider than the detection range of the radiographic image detection means, compared to the conventional one, the subject is exposed to exposure. It aims at providing the radiographic imaging apparatus which can reduce a dose.

  A radiographic image capturing apparatus according to the present invention includes: a radiation irradiating unit that irradiates a subject with radiation; a radiation image detecting unit that receives a radiation image transmitted through the subject; A moving unit that moves the radiation image detecting unit in parallel along a radiation detection surface; an irradiation position changing unit that changes a position of radiation irradiated by the radiation irradiating unit based on a position of the radiation image detecting unit; and a radiation image detecting unit. A plurality of radiation images taken at different positions of the means, and an image generating means for generating an image in a range wider than the detection range of the radiation image detecting means; a radiation irradiating means; a radiation image detecting means; Means, an irradiation position changing means, and a control means for controlling the operation of the image generating means. Associating a location, and changes the imaging condition for each region of the subject.

  Here, the “radiation image detecting means” obtains an image signal representing a radiographic image related to a subject by converting incident radiation directly or once into light and then converting it into electric charge and outputting the electric charge to the outside. Can be used.

  There are various types of solid-state detectors. For example, from the aspect of the charge generation process that converts radiation into electric charge, the photoconductive layer detects fluorescence emitted from the phosphor when irradiated with radiation. The signal charge obtained in this way is temporarily stored in the power storage unit, the stored charge is converted into an image signal (electrical signal) and output, or the photoconductive layer is irradiated with radiation. The signal charge generated in step 1 is collected by the charge collection electrode, temporarily stored in the power storage unit, and the stored charge is converted into an electrical signal and output, or the direct conversion type solid state detector that reads the stored charge to the outside From the aspect of the reading process, a TFT reading method that scans and reads a TFT (thin film transistor) connected to a power storage unit, or an optical reading method that reads a reading light (reading electromagnetic wave) by irradiating a detector to the detector. Such as those of news, there is such an improved direct conversion type which is proposed in the Patent Document 1 filed by the present applicant that combines the direct conversion type and the optical readout type.

  The “irradiation position changing means for changing the position of the radiation irradiated by the radiation irradiating means based on the position of the radiation image detecting means” means that the position of the radiation irradiating means is moved in accordance with the movement of the radiation image detecting means. The radiation direction of the radiation irradiation unit may be changed in accordance with the movement of the radiation image detection unit.

  The “imaging condition” refers to various operation setting conditions of the radiation irradiating means and the radiation image detecting means at the time of photographing, such as the intensity, amount and time of radiation irradiated by the radiation irradiating means, and the detection operation time of the radiation image detecting means. Means.

  In the radiographic image capturing apparatus according to the present invention, it is preferable that the image generating unit synthesizes the plurality of radiographic images after adjusting the density of the radiographic image for each of the plurality of radiographic images to be synthesized.

  Further, it is preferable that the control means associates the part of the subject and the position of the radiation image detecting means based on the information on the imaging range for the subject input from the outside and the information on the actual imaging range.

  Here, the “imaging range for the subject” means, for example, an imaging region for the subject (subject) such as the upper body or the entire lower limb, and the “actual imaging range” means a range for capturing a radiographic image by the radiographic image detecting means. That is, it means the moving range of the radiation image detecting means.

  Further, the radiation image detection means includes a plurality of radiation dose detection means for detecting the amount of irradiated radiation at different positions on the radiation detection surface, and the control means includes a plurality of radiation dose detection means for each part of the subject. It is preferable to select the radiation dose detecting means to be used.

  According to the radiographic image capturing apparatus of the present invention, in the radiographic image capturing apparatus corresponding to the long imaging in a range wider than the detection range of the radiographic image detecting means, the control means includes the position of the subject and the position of the radiographic image detecting means. Since the imaging condition is changed for each part of the subject, the radiation dose for each part of the subject can be optimized to reduce the exposure dose to the subject.

  In addition, even when the imaging conditions are changed for each region, the image generation means is configured to synthesize a plurality of radiation images after adjusting the density of the radiation images for each of the plurality of radiation images to be combined. An appropriate composite image can be obtained.

  Further, the control means associates the part of the subject and the position of the radiographic image detection means on the basis of the information about the photographing range with respect to the subject inputted from the outside and the information about the actual photographing range, so that the subject can be appropriately displayed. Can be associated with the position of the radiation image detecting means.

  Further, the radiation image detecting means is provided with a plurality of radiation dose detecting means (photo timer, etc.) for detecting the amount of irradiated radiation at different positions on the radiation detection surface, and a plurality of control means are provided for each part of the subject. By selecting the radiation dose detection means to be used from among the radiation dose detection means, it becomes possible to control the irradiation radiation dose using the optimum radiation dose detection means for each part of the subject. The exposure dose to can be reduced more reliably.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic side view showing a radiographic imaging system as an example of a preferred embodiment of the present invention, FIG. 2 is a front view of a radiographic imaging unit of a radiation irradiation apparatus of this system, and FIG. FIG. 4 is a schematic view of a solid state detector used in the apparatus, and FIG.

  This radiographic imaging system 1 includes a radiation irradiation apparatus 2 including a radiation source, a radiation imaging apparatus 3 including a solid detector 20 for detecting radiation, the radiation irradiation apparatus 2 and the radiation imaging apparatus 3. The computer 4 is connected and a monitor 5 is connected to the computer 4.

  The radiation irradiation apparatus 2 includes a base 10, a support column 11 fixed to the base 10, and a radiation irradiation unit 12 containing a radiation source therein. It is attached to be movable in the direction (vertical direction in FIG. 1).

  In the radiation irradiating apparatus 2, the operation of the radiation source and the movement operation of the radiation irradiating unit 12 are all integrated and controlled by a control means (not shown).

  The radiation imaging apparatus 3 includes a base 13, a column 14 fixed to the base 13, a radiographic imaging unit 15 that houses a solid detector 20 therein, and the radiographic imaging unit 15 and a subject P. It comprises a partition 16 disposed between them, a handrail 17 fixed to the base 13, and three phototimers 18a, 18b, and 18c as radiation dose detection means for detecting the irradiated radiation dose. The image capturing unit 15 is attached to be movable in the longitudinal direction of the support column 14 (vertical direction in FIG. 1).

  As shown in FIG. 2, the three phototimers 18a, 18b, and 18c are arranged on the radiation incident surface of the radiation image capturing unit 15, and the two phototimers are arranged at positions apart from each other in the upper half of the radiation incident surface. A phototimer 18c is disposed near the center of the lower half of the radiation incident surface 18a, 18b.

  As shown in FIG. 4, these phototimers 18 a, 18 b, and 18 c can appropriately select a phototimer to be used depending on the position of the radiographic image capturing unit 15, that is, the imaging region of the subject P. For example, as shown in FIG. 4A, when photographing the chest of the subject P, all three photo timers 18a, 18b, and 18c are used, and as shown in FIG. 4B, the waist of the subject P is used. When photographing the subject's thigh as shown in FIG. 4C, only the phototimer 18c arranged near the center of the lower half is used. Two photo timers 18a and 18b arranged in the are used. Of course, this is only an example, and the number of phototimers and usage patterns are not limited to the above.

  The system of the present embodiment can perform two types of shooting: normal shooting (only one shooting) and long shooting (image combining after shooting multiple times). It is configured so as to be detachable from the base 13, and when taking a long picture, a screen 16 is attached for photographing, and when not taking a long picture, the screen 16 is removed for photographing. In addition, a sensor for detecting the attachment / detachment state of the partition 16 is attached to the base 13.

  The solid state detector 20 is arranged inside the radiographic image capturing unit 15 so that its radiation detection surface is parallel to the radiation incident surface of the radiographic image capturing unit 15.

  As shown in FIG. 3, the solid state detector 20 includes a first conductive layer 24 made of an a-si TFT on a glass substrate 25, a photoconductivity that generates electric charge by receiving radiation and exhibits conductivity. The layer 23, the second conductive layer 22, and the insulating layer 21 are laminated in this order.

  The first conductive layer 24 is formed with a TFT corresponding to each pixel, the output of each TFT is connected to an IC chip 26, and the IC chip 26 is an image signal processing unit (not shown) on the printed circuit board 27. It is connected to the.

  When the solid state detector 20 irradiates the photoconductive layer 23 with radiation when an electric field is formed between the first conductive layer 24 and the second conductive layer 22, the solid state detector 20 enters the photoconductive layer 23. Charge pairs are generated, and latent image charges corresponding to the amount of the charge pairs are accumulated in the first conductive layer 24. When reading the accumulated latent image charge, the TFTs of the first conductive layer 24 are sequentially driven to output an analog signal corresponding to the latent image charge corresponding to each pixel, and this analog signal is processed by image signal processing. The detection is performed for each pixel in the unit, and the analog signals detected for each pixel are combined in the pixel arrangement order. The combined analog signal is AD converted by an AD converter (not shown) to generate a digital image signal. The generated digital image signal is transmitted from the image signal processing unit to the computer 4 via the memory.

  In the radiation imaging apparatus 3, the operation of the solid state detector 20 and the movement operation of the radiation image capturing unit 15 are all integrated and controlled by a control unit (not shown). The control means also has a function of notifying the computer 4 of information indicating the attachment / detachment state of the partition 16 on the base 13 and the detection states of the three photo timers 18a, 18b, 18c.

  The computer 4 includes an input device such as a mouse and a keyboard, and based on a function as an input unit that receives an input of an imaging region in long imaging, and a radiographic image capturing unit 15 based on information on the imaging region input to the input unit. Functions as a control means for controlling the radiation imaging apparatus 3 so as to move the radiographic image capturing unit 15 so as to include the entire imaging region, a function for designating an irradiation dose in the radiation irradiation apparatus 2, and the like A function for receiving and storing image signals acquired in the radiation imaging apparatus 3 and a plurality of radiation images captured at different positions of the radiation image capturing unit 15 are combined to detect the detection range of the radiation image capturing unit 15 It has a function as an image generation means for generating a wider range of images.

  In addition to this, it also has a function of recording and managing information related to the patient, such as the name and sex of the patient to be imaged, and information related to imaging such as the region to be imaged, radiation dose, and procedure.

  Next, the operation of the radiographic imaging system 1 configured as described above will be described. FIG. 5 is a view showing an example of a histogram of an image taken by the present system, and FIG. 6 is a view showing an example of an image taken by the present system.

  In this system, two types of shooting, normal shooting and long shooting, can be performed. Here, a case where long shooting is performed will be described.

  The photographer attaches the partition 16 to the base 13 when performing long shooting. When the screen 16 is attached to the base 13, the radiation imaging apparatus 3 notifies the computer 4 to that effect.

  When the computer 4 receives information indicating that the partition 16 is attached to the base 13 from the radiation imaging apparatus 3, the computer 4 automatically enters the long imaging mode and displays the long imaging menu on the monitor 5.

  The photographer puts the subject P at a position facing the partition 16 of the radiation imaging apparatus 3, and then inputs information about the imaging range for the subject P and information about the actual imaging range to the computer 4. Here, it is assumed that the upper body of the subject P is photographed, and three times of photographing are performed in order to photograph the entire range.

  The computer 4 automatically associates the site of the subject P with the position of the radiographic image capturing unit 15 based on the information about the imaging range for the subject P and the information about the actual imaging range, and uses the optimal radiation dose for each imaging. Each device is controlled to perform photographing.

  For example, in the case of the present embodiment, the first imaging is in the vicinity of the head of the subject P, the second imaging is in the vicinity of the chest of the subject P, and the third imaging is in the vicinity of the waist of the subject P. To decide.

  Thereafter, when the irradiation radiation intensity, the irradiation radiation dose, and the like are designated for each imaging region and the first stage of a two-stage radiation exposure switch (not shown) is pressed, the radiation irradiation unit 12 and the radiation image capturing unit 15 each perform the first time. When the second stage of the two-stage radiation exposure switch is pressed, the imaging is started. This second-stage switch is continuously pressed until all the imaging is completed, and is configured to immediately stop the radiation irradiation when the pressing is canceled halfway.

  When imaging is started, radiation is irradiated from the radiation irradiating unit 12 toward the radiation image capturing unit 15, and the first imaging is performed.

  When radiation is irradiated, latent image charges carrying radiation image information are accumulated in the solid state detector 20. Since the amount of accumulated latent image charge is substantially proportional to the amount of radiation transmitted through the subject P, this latent image charge carries an electrostatic latent image.

  When a predetermined radiation dose is detected by the phototimer of the radiation imaging apparatus 3, the radiation irradiation of the radiation irradiation apparatus 2 is stopped, and recording on the solid state detector 20 is stopped to complete the imaging.

  At this time, among the three photo timers 18a, 18b, and 18c of the radiation imaging apparatus 3, the photo timer to be used can be selected for each imaging region of the subject P, and when a plurality of photo timers are used in one imaging. The radiation irradiation device 2 may be controlled based on the average value of the radiation detection amount of each phototimer.

  Next, an analog signal corresponding to the latent image charge is output from the solid state detector 20, and AD conversion is performed in the image signal processing unit to generate a digital image signal N1. The generated digital image signal N1 is transmitted from the image signal processing unit to the computer 4 via the memory.

  When the computer 4 receives the digital image signal N1 from the radiation imaging apparatus 3, the computer 4 displays a preview image of the digital image signal N1 on the monitor 5 and ends the first imaging.

  Thereafter, the radiation irradiation unit 12 and the radiation image capturing unit 15 are moved downward to perform the next imaging. At this time, the radiographic image capturing unit 15 is moved so as to include the previous imaging range slightly (including the overlap), and the radiation irradiating unit 12 is also moved correspondingly. Then, in the same procedure as the first time, the second shooting and the third shooting are performed, and the digital image signals N2 and N3 are acquired.

  In the case of long shooting, when the digital image signals N1, N2, and N3 are acquired, the image is synthesized by the computer 4 and an image having a wider range than the detection range of the solid state detector 20 is generated. In the system, image synthesis is started when two digital image signals adjacent to each other are acquired, not after all of the digital image signals N1, N2, and N3 are acquired.

  As shown in FIG. 5, image synthesis is performed by creating a histogram of each image signal for all of the acquired digital image signals N1, N2, and N3 so that the density and contrast approximate each other based on this histogram. Perform automatic adjustment. At this time, the density and contrast of each image may be adjusted based on the density and contrast of a predetermined reference image (for example, the first image taken), or the reference density and contrast are set in advance. In addition, the density and contrast of each image may be adjusted based on this.

  Thereafter, as shown in FIG. 6, overlapping portions of adjacent images are synthesized by an averaging process. The synthesis process is not limited to the averaging process, and may be performed by any process such as a weighted addition process.

  At this time, in order to make the combination position of the second image signal N2 with the first image signal N1 appropriate, pattern matching is performed line by line in the vertical direction in FIG. Perform synthesis at the location. The area where the pattern matching is performed may be in the same range as the movement accuracy of the moving means for moving the radiation image capturing unit 15.

  For example, when the movement accuracy of the moving means is 1 mm, pattern matching may be performed by shifting the pixels one line at a time in the range of 1 mm above and below around the position where the locations recognized as overlapping portions are overlapped. . By adopting such an aspect, the pattern matching process is not performed for an unnecessary range, so that the time required for image synthesis can be shortened.

  In the present embodiment, when the digital image signals N1 and N2 are acquired, the digital image signals N1 and N2 are combined, a combined image of N1 and N2 is displayed on the monitor 5, and the digital image signal is further displayed. When N3 is acquired, the composite image signal of N1, N2 and the digital image signal N3 are combined, and the composite image of N1, N2, N3 is displayed on the monitor 5.

  At this time, the length in the vertical direction (vertical direction in FIGS. 1 and 6) indicated by the finally obtained composite image signal of N1, N2, and N3 and the vertical direction of the first set photographing range (FIGS. 1 and 6). Compared with the length in the middle / up / down direction, if the error is within a predetermined range, it is determined that the composition is normally performed. If the error exceeds the predetermined range, it is determined that the composition is not normally performed. Then, an abnormal message may be displayed on the monitor 5.

  Further, if a marker or the like is displayed at the joint portion in the composite image, it can be easily confirmed whether the image is normally combined.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to the said embodiment, For example, a radiation irradiation part is not restricted to what moves in parallel as mentioned above, The height is It is good also as what fixes only the irradiation direction of a radiation.

  Further, although a TFT readout type is used as the solid state detector, the same effect can be obtained even with an individual detector of another type such as an optical readout type.

Schematic showing a radiographic imaging system according to the invention Front view of the radiation image capturing unit of the radiation irradiation apparatus of the above system Schematic diagram of a solid state detector used in the radiographic apparatus of the above system The figure which shows the usage example of the phototimer of the radiation irradiation apparatus of the said system The figure which shows an example of the histogram of the image image | photographed by the said system The figure which shows an example of the image image | photographed by the said system

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Radiation imaging system 2 Radiation irradiation apparatus 3 Radiation imaging apparatus 4 Computer 5 Monitor 10 Base 11 Prop 12 Radiation irradiation part 13 Base 14 Post 15 Radiation imaging part 16 Screen 17 Handrail 20 Solid state detector

Claims (4)

Radiation irradiating means for irradiating the subject with radiation;
Radiation image detection means for taking a radiation image of the subject in response to irradiation with radiation transmitted through the subject;
Moving means for moving the radiation image detecting means in parallel along the radiation detection surface of the radiation image detecting means;
An irradiation position changing means for changing the position of the radiation irradiated by the radiation irradiating means based on the position of the radiation image detecting means;
Image generating means for combining a plurality of the radiographic images taken at different positions of the radiographic image detecting means and generating an image in a range wider than the detection range of the radiographic image detecting means;
Control means for controlling operations of the radiation irradiating means, the radiation image detecting means, the moving means, the irradiation position changing means, and the image generating means;
The radiographic imaging apparatus characterized in that the control means associates the part of the subject and the position of the radiographic image detection means, and changes imaging conditions for each part of the subject.   2. The radiation according to claim 1, wherein the image generating unit synthesizes the plurality of radiographic images after adjusting the density of the radiographic image for each of the plurality of radiographic images to be synthesized. Image shooting device.   The control means associates the part of the subject and the position of the radiological image detection means based on information on the imaging range for the subject and information on the actual imaging range input from the outside. The radiographic imaging device according to claim 1 or 2. The radiation image detection means comprises a plurality of radiation dose detection means for detecting the amount of irradiated radiation at different positions on the radiation detection surface,
The said control means selects the radiation dose detection means to be used from among the said some radiation dose detection means for every site | part of the said subject, The any one of Claim 1 to 3 characterized by the above-mentioned. Radiation imaging device.

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