JP2010213768A - Radiographic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray imaging apparatus 1 capable of obtaining a series of rectangular images while the imaging condition is preferably adjusted, with construction without the phototimer. <P>SOLUTION: The X-ray imaging apparatus 1 has the structure for taking rectangular images P successively. Subjects in adjacent rectangular images P in the time elapse manner are regarded as almost the same, and the imaging condition of the rectangular image P for the next imaging is decided from the rectangular image P which is photographed this time. By thus deciding the imaging condition of the rectangular image P for the next imaging from the rectangular image P photographed this time, and obtaining and joining the series of rectangular images P, the X-ray imaging apparatus 1 can be provided where the subject is photographed with a pixel distribution suitable for diagnosis. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a radiographic apparatus that acquires a fluoroscopic image of a subject, and more particularly, to a radiographic apparatus that synthesizes strip images to generate a single radiographic image.

  A medical institution is provided with a radiation imaging apparatus 51 that acquires a fluoroscopic image of a subject. As shown in FIG. 12, such a radiographic apparatus 51 is provided on the top plate 52 on which the subject M is placed, the radiation source 53 provided on the upper side of the top plate 52, and the lower side of the top plate 52. The radiation detector 54 and a phototimer 55 provided so as to cover the detection surface for detecting the radiation of the radiation detector 54 are provided. The radiation source 53 and the radiation detector 54 can move with respect to the top plate 52 while maintaining a relative position. The phototimer 55 can detect the intensity of the radiation that has passed through the subject M.

  The radiation imaging apparatus 51 is configured to acquire a plurality of strip images P extending in the body-side direction S of the subject M as shown in FIG. 13 and connect them to generate a single fluoroscopic image Q. . By performing such imaging, it is possible to obtain a radiographic image Q having high contrast while suppressing the incidence of indirect radiation. An operation for acquiring the strip image P will be described. First, radiation is emitted from the radiation source 53. This radiation passes through the subject M and the phototimer 55 and then enters the radiation detector 54.

  Most of the radiation incident on the phototimer 55 goes to the radiation detector 54. However, some are detected by the phototimer 55. As described above, the phototimer 55 measures the dose of the incident radiation, and stops the radiation irradiation of the radiation source 53 when the cumulative radiation dose from the start of the radiation irradiation reaches a certain amount. That is, the phototimer 55 is provided for the purpose of determining the exposure time when the strip image P is acquired.

  The configuration of the phototimer 55 will be described. As shown in FIG. 14, the phototimer 55 has a configuration in which two transparent plates 55a and 55b are fixed so as to sandwich a frame 55c. A circular electrode is provided at the center of each of the transparent plates 55a and 55b. The space closed by the transparent plates 55a and 55b and the frame 55c is filled with xenon gas, and the xenon atoms are ionized upon exposure to radiation. This is detected by both electrodes of the transparent plates 55a and 55b. That is, the phototimer 55 determines the exposure time when acquiring the strip image P by monitoring the radiation dose in the region R sandwiched between both electrodes.

JP 2007-275228 A

However, the conventional configuration has the following problems.
That is, in the conventional configuration, the exposure time of radiation may not be determined correctly. The radiation imaging apparatus 51 emits radiation only once to the radiation detector 54 in addition to the mode in which the above-described strip images P are connected to obtain a single fluoroscopic image, and based on this, the radiographic image is displayed. A mode to acquire is prepared. The detection surface of the radiation detector 54 has a substantially square shape, and a radioscopic image having the same shape as this is acquired. The shape and size of the electrode of the phototimer 55 can obtain a suitable exposure time in this single shot. Therefore, as shown in FIG. 15, the areas Ra and Rb in which the radiation dose is measured may protrude from the strip images Pa and Pb. In such a state, the exposure time is determined in consideration of the radiation dose in the protruding area that does not constitute the strip images Pa and Pb. Then, there is a possibility that the strip image P is underexposed or overexposed.

  Moreover, the shape of the subject M reflected in the series of strip images P is not constant. A strip image on the chest of the subject M is Pa, and a strip image on the leg of the subject M is Pb. The phototimer 55 is present at the position A in FIG. 15 at the time of acquiring the strip image Pa, and the region at that time is Ra. At this time, the entire region Ra is included in the subject M.

  From there, the strip images P are photographed one after another, and the region Rb at the time of photographing the strip images Pb is located at a position where both feet of the subject M are bridged. not exist. Therefore, when the exposure time is determined with reference to the region Rb, it is determined that the radiation is strong, and the radiation irradiation is immediately terminated.

  At the time of obtaining the strip image Pb, for example, when the region where the entire region is included in one leg of the subject M is Ri as shown in FIG. 15, the exposure time is determined with reference to the radiation dose in the region Ri. If possible, the dose of the strip image Pb is suitable. However, since the phototimer 55 actually determines the exposure time in consideration of the area where nothing is captured between both legs of the subject M, both legs of the subject M appear on the strip image Pb in an underexposed state. Come on.

  Thus, at the time of acquiring a series of strip images P, the area referred to for determining the exposure time of the strip images P is not suitable, so that the subject M is extremely bright or extremely A strip image P that is darkly reflected in the image is acquired.

  When acquiring a series of strip images P, if the shape of the region can be changed, the exposure is suitable. However, the photo timer 55 cannot be exchanged once shooting has begun. In the first place, it is not realistic to replace the photo timer 55 every time the strip image P is taken.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a radiation imaging apparatus capable of acquiring a series of strip images while making imaging conditions such as exposure time suitable. It is to be realized with a configuration in which the timer is omitted.

The present invention has the following configuration in order to solve the above-described problems.
That is, the radiation imaging apparatus according to claim 1 is a relative position of a top plate on which a subject is placed, a radiation source that irradiates radiation, a radiation detection unit that detects radiation, a radiation source, and a radiation detection unit. Moving means for moving both of them relative to the top plate in a state of maintaining, a movement control means for controlling the moving means, an image generating means for generating a fragment image based on a detection signal output from the radiation detecting means, Histogram generating means for generating a histogram of fragment images, imaging condition determining means for determining imaging conditions for the next imaging based on the histogram, radiation source control means for controlling the radiation source based on the imaging conditions, a radiation source, and A splicing means for splicing a series of fragment images taken while moving the radiation detection means with respect to the top board to generate a single radioscopic image; And it is characterized in Rukoto.

  [Operation / Effect] According to the radiation imaging apparatus of the present invention, the fragment images are continuously performed, and the histogram generating means generates the histograms every time the fragment images are acquired. Based on this histogram, shooting conditions for the next shooting are determined. That is, the shooting condition of the next fragment image to be captured is determined from the currently captured fragment image. When determining the shooting conditions for the fragment images, it is necessary to determine the shooting conditions that have not yet been performed, and it is difficult to accurately know the shooting conditions for the fragment images. If a phototimer is used, shooting conditions can be determined while shooting, but accurate shooting conditions cannot be determined using this.

  However, according to the present invention, this difficulty is solved by assuming that the subject images appearing in the adjacent fragment images with the time of imaging are almost the same. In the configuration in which fragment images are acquired one after another while moving the radiation source and the radiation detection means with respect to the top plate, the fragment image captured this time and the fragment image captured next time are used as similar images. To do. In this way, by determining the shooting conditions of the next captured fragment image from the currently captured fragment image, and acquiring and connecting a series of fragment images, the subject is captured with a pixel value distribution suitable for diagnosis. A compact radiographic apparatus can be provided.

  The invention according to claim 2 is the radiation imaging apparatus according to claim 1, wherein the movement control means moves the radiation source and the radiation detection means in one direction when taking a series of fragment images. It is a feature.

  [Operation / Effect] According to the above-described configuration, the subject image reflected in the adjacent fragment images with the passage of time is more surely similar. This is because when the fragment images of the subject M are acquired along one direction, the fragment images whose acquisition times are adjacent over time are also adjacent in position.

  The invention according to claim 3 further comprises reference value storage means for storing a reference value in the radiation imaging apparatus according to claim 1 or claim 2, wherein the imaging condition determination means acquires the center of gravity of the histogram. It is characterized by comprising a center of gravity acquisition means and a comparison means for comparing the pixel value of the center of gravity of the histogram with a reference value to determine the photographing condition.

  [Operation / Effect] The above-described configuration shows a specific configuration of the photographing condition determining means. The photographing condition determining means determines the photographing condition by comparing the pixel value of the center of gravity of the histogram with the reference value.

  According to a fourth aspect of the present invention, in the radiographic apparatus according to the third aspect, the reference value storage means stores a reference table in which position information indicating the position of the fragment image is associated with the reference value, and is compared. The means is characterized in that a reference value corresponding to a next-captured fragment image is obtained from the reference table and the relative position of the fragment image with respect to the top board, and this is compared with the center of gravity of the histogram.

  [Operation / Effect] According to the above-described configuration, radiography with a higher degree of freedom is possible. Depending on the region of the subject, there are a portion with a lot of bone tissue and a portion with a lot of soft tissue. Therefore, it may be better to change the reference value referred to by the comparison means depending on the site of the subject. According to the above-described configuration, the reference value associated with the position information indicating the position of the fragment image and the reference value is included, so that the reference value can be weighted according to the region of the subject.

  The invention according to claim 5 is the radiographic apparatus according to any one of claims 1 to 4, further comprising a brightness upper limit storage unit that stores a brightness upper limit, and is brighter from the brightness upper limit in the histogram. The image processing apparatus further includes an upper trimming unit that trims the side region from the histogram so that the bright side region is not used for acquiring the center of gravity of the center of gravity acquiring unit.

  Further, the invention according to claim 6 is the radiographic apparatus according to any one of claims 1 to 5, further comprising a luminance lower limit value storing means for storing a luminance lower limit value, and dark from the luminance lower limit value in the histogram. The image processing apparatus further includes a lower trimming unit that trims the side region from the histogram so that the dark side region is not used for the center of gravity acquisition of the center of gravity acquisition unit.

  [Operation / Effect] With the above-described configuration, it is possible to acquire the pixel value of the center of gravity of the histogram more suitable for determining the photographing condition. In a region on the bright side from the luminance upper limit value in the histogram, very bright pixel values in which the subject is not captured are densely gathered to form a peak. Also, in the region on the dark side from the lower limit of luminance in the histogram, very dark pixel values derived from metal such as an artificial joint embedded in the subject are densely gathered to form another peak. The upper trimming means does not use the bright area for the center of gravity acquisition of the center of gravity acquisition means, and the lower trimming means does not use the dark side area for the center of gravity acquisition of the center of gravity acquisition means. In this way, since the pixel value of the center of gravity of the histogram is acquired in a state where the component that does not depend on the subject itself is ignored, it is possible to acquire the pixel value of the center of gravity of the histogram more suitable for determining the imaging conditions. it can.

  The invention according to claim 7 is the radiographic apparatus according to any one of claims 1 to 6, further comprising initial imaging condition storage means for storing initial imaging conditions, wherein the imaging condition determination means includes The imaging condition of the first fragment image in a series of continuous shooting is determined based on the imaging condition.

  [Operation / Effect] The above-described configuration shows a specific configuration related to the acquisition of the first fragment image. Since the photographing condition of the fragment image is determined based on the previously acquired fragment image, there arises a problem of how to determine the photographing condition of the first fragment image. According to the above-described configuration, the first photographing condition is separately stored, and the first fragment image is acquired using this.

  According to the radiation imaging apparatus of the present invention, the fragment image is continuously performed, and the imaging condition of the fragment image to be captured next time is determined from the currently captured fragment image. In a configuration in which fragment images are acquired one after another while moving the radiation source and the radiation detection means with respect to the top plate, the fragment image captured this time and the fragment image captured next time are similar images. According to the present invention, the subject images that appear in the adjacent fragment images with respect to the time of imaging are considered to be substantially the same. In this way, by determining the shooting conditions of the next captured fragment image from the currently captured fragment image, and acquiring and connecting a series of fragment images, the subject is captured with a pixel value distribution suitable for diagnosis. A compact radiographic apparatus can be provided.

1 is a functional block diagram illustrating a configuration of an X-ray imaging apparatus according to Embodiment 1. FIG. 1 is a perspective view illustrating a configuration of a collimator according to Embodiment 1. FIG. FIG. 3 is a functional block diagram illustrating a configuration of an information storage unit according to the first embodiment. It is a functional block diagram explaining the structure of the exposure time determination part which concerns on Example 1. FIG. 3 is a flowchart for explaining an operation according to the first embodiment. 3 is a schematic diagram illustrating a strip image according to Embodiment 1. FIG. FIG. 10 is a schematic diagram for explaining editing of a histogram according to the first embodiment. FIG. 10 is a schematic diagram for explaining editing of a histogram according to the first embodiment. FIG. 10 is a schematic diagram for explaining editing of a histogram according to the first embodiment. 3 is a schematic diagram illustrating a strip image according to Embodiment 1. FIG. It is a schematic diagram explaining the structure which concerns on 1 modification of this invention. It is a figure explaining the radiography apparatus of a conventional structure. It is a figure explaining the radiography apparatus of a conventional structure. It is a figure explaining the radiography apparatus of a conventional structure. It is a figure explaining the radiography apparatus of a conventional structure.

  Next, the configuration of the radiation imaging apparatus according to Embodiment 1 will be described with reference to the drawings. The X-ray in Example 1 corresponds to the radiation of the present invention.

<Device configuration>
As shown in FIG. 1, the radiation imaging apparatus 1 according to the first embodiment includes a top plate 2 on which a subject M is placed, and an X-ray tube 3 that irradiates an X-ray beam provided on the top plate 2. A flat panel detector (FPD) 4 for detecting an X-ray beam provided under the top plate 2, an X-ray tube control unit 6 for controlling the irradiation time, tube current, and tube voltage of the X-ray tube 3; The image generation unit 11 generates a strip image P in which a part of the subject M is reflected based on the detection signal output from the FPD 4, the histogram generation unit 12 generates a histogram H0 of the strip image P, and the histogram H0. The upper trimming unit 13 and the lower trimming unit 14 for editing the exposure time, and the exposure time determination unit 15 for determining the exposure time based on the edited histogram H0uL.

  The X-ray tube control unit 6 corresponds to the radiation source control means of the present invention, and the X-ray tube 3 corresponds to the radiation source of the present invention. The FPD 4 corresponds to the radiation detection means of the present invention, and the upper trimming unit 13 corresponds to the upper trimming means of the present invention. The image generation unit 11 corresponds to the image generation unit of the present invention, and the lower trimming unit 14 corresponds to the lower trimming unit of the present invention. The histogram generator 12 corresponds to the histogram generator of the present invention. The strip image P corresponds to a fragment image of the present invention.

  The radiation imaging apparatus 1 includes a joining unit 18 that joins the strip images P, an X-ray tube moving mechanism 21 that moves the X-ray tube 3, an X-ray tube moving control unit 22 that controls the X-ray tube moving control unit 22, and an FPD 4. An FPD movement mechanism 23 that moves the FPD movement control unit 24 that controls the FPD movement mechanism 23 is provided. In addition, the radiation imaging apparatus 1 includes an information storage unit 25 that stores various types of information, an operation console 26 that inputs an operator's instruction, and a display unit 27 that displays an X-ray fluoroscopic image Q. The joining unit 18 corresponds to the joining means of the present invention, and the X-ray tube moving mechanism 21 and the FPD moving mechanism 23 correspond to the moving means of the present invention. The X-ray tube movement control unit 22 and the FPD movement control unit 24 correspond to movement control means of the present invention.

  The X-ray imaging apparatus 1 includes a main control unit 31 that comprehensively controls the units 6, 11, 12, 13, 14, 15, 18, 22, and 24. The main control unit 31 is constituted by a CPU, and realizes each unit by executing various programs. Further, each of the above-described units may be divided and executed by an arithmetic device that takes charge of them.

  The X-ray tube 3 is provided with a collimator 3a. The collimator 3 a is attached to the X-ray tube 3, and collimates the X-rays emitted from the X-ray tube 3 to form a quadrangular pyramid-shaped X-ray beam B. Details of the collimator 3a will be described. As shown in FIG. 2, the collimator 3a has a pair of leaves 3b that move mirror-symmetrically, and includes another pair of leaves 3b that also move mirror-symmetrically. The collimator 3a can move the leaf 3b to irradiate the entire surface of the X-ray detection surface of the FPD 4 with the cone-shaped X-ray beam B. For example, only the central portion of the FPD 4 has a fan-shaped X-ray. The beam B can also be irradiated. A central axis C is set for the X-ray beam B. Each leaf 3b moves in mirror image symmetry with the central axis C as a reference. One of the pairs of leaves 3b is for adjusting the spread in the body axis direction A of the X-ray beam having a quadrangular pyramid shape, and the other pair of leaves 3b is the body side direction S of the X-ray beam. It is to adjust the spread of. The collimator moving mechanism 29 changes the opening of the collimator 3a. The collimator control unit 30 controls the collimator moving mechanism 29.

  As shown in FIG. 3, the information storage unit 25 includes a reference value storage unit 25a that stores a reference value, a luminance upper limit value storage unit 25b that stores a luminance upper limit value, and a luminance lower limit value storage unit that stores a luminance lower limit value. 25c and an initial imaging condition storage unit 25d for storing the initial imaging conditions. The luminance upper limit storage unit 25b corresponds to the luminance upper limit value storage unit of the present invention, and the initial imaging condition storage unit 25d corresponds to the initial imaging condition storage unit of the present invention. The reference value storage unit 25a corresponds to the reference value storage unit of the present invention, and the luminance lower limit value storage unit 25c corresponds to the luminance lower limit value storage unit of the present invention.

  As shown in FIG. 4, the exposure time determination unit 15 includes a center-of-gravity acquisition unit 15a and a comparison unit 15b. These details will be described later.

<Description of operation>
The operation of such an X-ray imaging apparatus 1 will be described. In the X-ray imaging apparatus 1, the X-ray fluoroscopic image Q is obtained by placing the subject M on the top 2 as shown in FIG. 5 and the first strip image P 0 for obtaining the first strip image P 0. From the acquisition step S2, the histogram acquisition step S3 for generating the histogram H0 of the strip image P, the histogram editing step S4 for editing the histogram H0, the centroid acquisition step S5 for acquiring the centroid G of the histogram, and the pixel value of the centroid G An exposure time acquisition step S6 for acquiring the exposure time t, a strip image acquisition step S7 for updating the exposure time t to acquire the strip image P, and the acquired strip image P are connected to form a single fluoroscopic image. This is performed by performing each step of a joining step S8 for acquiring Q and a display step S9 for displaying the X-ray fluoroscopic image Q. Hereinafter, the details of each step will be described in order. The exposure time t corresponds to the shooting condition of the present invention.

<Installation step S1, first strip image acquisition step S2>
First, the subject M is placed on the top 2 (see FIG. 1). When the operator gives an instruction to acquire the X-ray fluoroscopic image Q through the console 26, the X-ray tube movement control unit 22 and the FPD movement control unit 24 maintain the relative positional relationship between the X-ray tube 3 and the FPD 4. In this state, the X-ray tube 3 and the FPD 4 are moved to one end in the body axis direction A in the field of view of the X-ray fluoroscopic image Q. From this position, the strip images 3 and 4 continuously take a strip image while moving toward the other end of the fluoroscopic image Q in the same direction and at the same speed along the body axis direction A.

  The collimator 3a makes the pair of leaves 3b that move along the body axis direction A approach, and separates the pair of leaves 3b that move along the body side direction S. Then, the X-ray beam emitted from the collimator 3a becomes a fan-shaped fan beam as shown in FIG. 2, and is incident on the band-shaped region R (see FIG. 6) extending in the body side direction S in the FPD 4.

  The exposure time determination unit 15 reads the initial shooting conditions from the information storage unit 25. The initial imaging conditions are control conditions for the X-ray tube 3 in which tube voltage, tube current, exposure time, etc. are preset. The information storage unit 25 stores a plurality of initial imaging conditions, and the initial imaging conditions read to the exposure time determination unit 15 can be selected in accordance with the purpose of imaging. The surgeon makes this selection through the console 26.

  The exposure time determination unit 15 sends the initial imaging conditions to the X-ray tube control unit 6. The X-ray tube control unit 6 controls the X-ray tube 3 based on the initial imaging conditions. The X-ray tube 3 outputs X-rays during the period indicated by the exposure time with the tube voltage and tube current of the initial imaging conditions. The fan beam emitted from the collimator 3a passes through the subject M and then enters the band-shaped region R extending in the body side direction S in the FPD 4. The X-ray detection signal output from the FPD 4 is sent to the image generation unit 11, where an initial strip image P0 in which a fluoroscopic image of the subject M is copied is generated. The initial strip image P0 is generated only in the portion where the X-rays in the FPD 4 are incident. Therefore, the first strip image P0 is an elongated image having the same shape as the band-shaped region R in the FPD 4 described above.

<Histogram acquisition step S3>
The initial strip image P0 is sent to the histogram generator 12, and the histogram H0 of the initial strip image P0 is generated. The histogram H0 shows the distribution of pixel values of the pixels constituting the initial strip image P0, and can be visually represented by a graph showing the relationship between the pixel value x and the frequency f as shown in FIG. .

<Histogram editing step S4>
The generated histogram H0 is sent to the upper trimming unit 13. The histogram H0 is composed of three peaks. The bright side peak a in the histogram H0 is derived from a portion of the FPD 4 that is not masked by the subject M. That is, it is derived from a portion like region D in FIG. In this portion, since the X-rays enter the FPD 4 without being attenuated by the subject M, the detected X-ray dose is strong and uniform between the regions D. Accordingly, the histogram H0 of the initial strip image P0 appears as a sharp peak on the bright pixel value side (on the high pixel value side). Further, the gentle peak b appearing in the histogram H0 is derived from the portion masked by the subject M in the FPD4. In this portion, X-rays are attenuated by the subject M and enter the FPD 4, so that the detected X-ray dose has various values depending on the portion of the initial strip image P 0. Therefore, the histogram H0 of the first strip image P0 appears with a certain width on the pixel value side (on the low pixel value side) slightly darker than the peak a.

  The upper trimming unit 13 trims the peak a from the histogram H0. That is, the upper trimming unit 13 reads the luminance upper limit value stored in the information storage unit 25 and rewrites all the frequencies f of the brighter region from 0 in the histogram H0 to zero. Then, as shown in FIG. 8, the peak a of the histogram H0 is trimmed from the generated histogram H0u.

  The histogram H0u is sent to the lower trimming unit 14. When a metal such as an artificial joint is embedded in the subject M, the metal is difficult to pass X-rays, so the metal appears dark enough to be impossible for the subject M in the strip image. A pixel derived from such a metal appears in a very dark region in the histogram H0, and appears as a peak c in FIG. The peak c appears in the histogram H0 as a relatively sharp peak due to the appearance of similar low pixel values at a high frequency. Also in the histogram H0u, this peak c is not removed and is inherited from the histogram H0.

  The lower trimming unit 14 trims the peak c from the histogram H0u. That is, the lower trimming unit 14 reads the luminance lower limit value stored in the information storage unit 25, and rewrites all the frequencies f in the darker area from the luminance lower limit value in the histogram H0u to zero. Then, the peak c is trimmed from the generated histogram H0uL as shown in FIG.

  In this way, the upper trimming unit 13 and the lower trimming unit 14 cooperate to edit the histogram H0 and generate a histogram H0uL.

<Center of gravity acquisition step S5>
The histogram H0uL is sent to the center-of-gravity acquisition unit 15a provided in the exposure time determination unit 15. The center-of-gravity acquisition unit 15a analyzes the histogram H0uL and acquires the pixel value of the center of gravity G. The pixel value of the center of gravity G of the histogram H0uL is the pixel value x1 at a position that divides the peak b (the peak that remains without being trimmed) into two equal parts (see FIG. 9). That is, the integral value obtained by integrating the peak b with respect to x in the bright region from the pixel value x1 and the integral value obtained by integrating the peak b with respect to x in the dark region from the pixel value x1 are exactly the same. The center of gravity acquisition unit 15a corresponds to the center of gravity acquisition means of the present invention.

<Exposure time acquisition step S6>
The pixel value of the center of gravity G is sent to the comparison unit 15b. The comparison unit 15b reads the reference value from the information storage unit 25 and compares it with the pixel value of the center of gravity G. Since the reference value indicates an ideal value of the pixel value of the centroid G, it is determined whether the luminance of the strip image P is too bright or too dark depending on how much the pixel value of the centroid G deviates from the reference value. . When the pixel value of the center of gravity G is darker than the reference value, the comparison unit 15b determines that the exposure time of the first strip image P is too short, sets the exposure time t to be long, and sets this as the new exposure time. Let t1. The newly obtained exposure time t1 is sent to the X-ray tube control unit 6. Conversely, when the pixel value of the center of gravity G is brighter than the reference value, the exposure time t1 is shortened. The comparison unit 15b corresponds to the comparison unit of the present invention.

  The adjustment of the exposure time performed by the comparison unit 15b can be obtained as a linear relationship between the pixel value of the center of gravity G and the length of the exposure time. For example, if the pixel value of the centroid value G is 1.2 times the reference value, a new exposure time t1 is obtained by multiplying the exposure time t0 when the first strip image P0 is captured by 1 / 1.2 times. Note that a relational expression between the pixel value of the center of gravity G and the length of the exposure time may be obtained in advance by actual measurement or the like, and this relational expression may be stored in the information storage unit 25. The comparison unit 15b calculates a new exposure time t1 by applying the pixel value of the center of gravity G and the length of the exposure time to the relational expression.

<Strip image acquisition step S7>
The X-ray tube 3 and the FPD 4 move by a predetermined pitch (which is stored in the information storage unit 25) in the body axis direction A according to control of the control units 22 and 24 in charge of each. This movement will be described. As shown in FIG. 10, the field of view of the X-ray tube 3 and the FPD 4 at the time of photographing the first strip image P0 and the field of view of the X-ray tube 3 and the FPD 4 at the time of photographing the strip image P1 adjacent to the first strip image P0. The range partially overlaps. This is not limited to the first strip image P0, but all adjacent strip images P0 to P4 overlap each other from the body axis direction A direction. Assuming that the overlap portion of the initial strip image P0 is a portion Δp0 as shown in FIG. 10, the strip images P1 to P3 are provided with similar portions Δp1 to Δp3, respectively. The width of Δp0 to Δp3 is about 1 cm in the body axis direction A.

  When the X-ray tube 3 and the FPD 4 have finished moving after taking the first strip image P0, the X-ray tube control unit 6 controls the X-ray tube 3 based on the new exposure time t1, and the X-ray tube 3 Irradiate. Based on this, the image generation unit 11 generates a strip image P1. The obtained strip image P1 is sent to the histogram generator 12, and the exposure time t2 is further calculated through steps S3 to S6 described above. This exposure time t2 is used to acquire the next strip image P2.

  In this way, the exposure time used when acquiring the strip images P0 to Pn is the exposure time t0 of the first fluoroscopic condition in the first strip image P0, and in the strip image Pn, the previous strip image Pn− is used. 1 is an exposure time tn obtained by histogram analysis. As described above, in the configuration of the first embodiment, the exposure time obtained with the current strip image is used for obtaining the next strip image.

  The image generation unit 11 adds a serial number in the order in which the strip images are generated to the strip image. The serial number corresponds to the position information of the present invention. Moreover, the X-ray tube 3 and the FPD 4 acquire the strip images P0 to Pn while moving in one direction along the body axis direction of the subject M. Therefore, the strip images that are adjacent to each other over time are also adjacent to each other in terms of position.

  The histogram acquisition step S3 to the strip image acquisition step S7 are continued until acquisition of all the strip images P is completed. When the acquisition of the final strip image P is completed, the subsequent steps are executed.

<Connection Step S8, Display Step S9>
The strip images P0 to Pn are sent not only to the histogram generation unit 12 but also to the joining unit 18. The joining unit 18 arranges the strip images P <b> 0 to Pn in an overlapping manner in order (see FIG. 10), joins them together, and acquires a single X-ray fluoroscopic image Q. The interval at which the strip images P0 to Pn are arranged at the time of joining is determined by referring to the pitch stored in the information storage unit 25 by the joining unit 18. Finally, an X-ray fluoroscopic image Q is displayed on the display unit 27, and the operation of the X-ray imaging apparatus 1 ends.

  As described above, according to the X-ray imaging apparatus 1 of the present invention, the strip image P is continuously performed, and the histogram generation unit 12 generates the histogram H each time the strip image P is acquired. To do. Based on this histogram H, shooting conditions for the next shooting are determined. That is, the shooting condition of the strip image P to be captured next time is determined from the strip image P captured this time. When determining the shooting conditions of the strip image P, it is necessary to determine shooting conditions that have not yet been performed, and it is difficult to accurately know the shooting conditions of the strip image P. If a phototimer is used, shooting conditions can be determined while shooting, but accurate shooting conditions cannot be determined using this.

  However, according to the present invention, this difficulty is solved by assuming that the subject images appearing in the strip images P that are adjacent to each other with respect to time are substantially the same. In the configuration of Example 1 in which the strip images P are acquired one after another while moving the X-ray tube 3 and the FPD 4 with respect to the top plate 2, the strip images P photographed this time and the strip images P photographed next time are: It takes advantage of similar images. In this way, by determining the imaging conditions of the strip image P to be captured next time from the strip image P captured this time, and acquiring and connecting a series of strip images P, the pixel value distribution suitable for diagnosis by the subject is suitable. Therefore, the X-ray imaging apparatus 1 can be provided.

  Further, according to the configuration of the first embodiment, the strip image P of the subject M is acquired while the X-ray tube 3 and the FPD 4 move along one direction. Then, the subject images reflected in the adjacent strip images P with respect to time are surely similar. This is because the strip images P whose acquisition times are adjacent over time are also adjacent in position.

  The configuration of the first embodiment can acquire the pixel value of the centroid G of the histogram H that is more suitable for determining the shooting condition. In the region on the bright side from the luminance upper limit value in the histogram H, very bright pixel values in which the subject is not reflected are densely gathered to form a peak a. Also, in the region on the dark side from the luminance lower limit value in the histogram H, very dark pixel values derived from metal such as an artificial joint embedded in the subject are frequently densely formed to form a peak c. The upper trimming unit 13 does not use the bright side region for acquiring the center of gravity G in the centroid acquisition unit 15a, and the lower trimming unit 14 does not use the dark side region for acquisition of the centroid G in the centroid acquisition unit 15a. In this way, since the pixel value of the center of gravity G of the histogram H is acquired in a state where the component that does not depend on the subject itself is ignored, the pixel value of the center of gravity G of the histogram H that is more suitable for determining the imaging conditions is obtained. Can be acquired.

  And the structure of Example 1 shows the specific structure regarding acquisition of the first strip image P0. Since the shooting condition of the strip image P is determined based on the previously acquired strip image P, there arises a problem of how to determine the shooting condition of the first strip image P0. According to the configuration of the first embodiment, the initial photographing conditions are separately stored, and the first strip image P is acquired using this.

  The present invention is not limited to the configuration of the above-described embodiment, and can be modified as follows.

  (1) In the above-described embodiment, the same reference value is used for the strip images P0 to Pn, but the present invention is not limited to this. That is, the exposure times t1 to tn may be determined using different reference values Ref0 to Refn for the strip images P0 to Pn. In this case, the reference value storage unit 25a stores a reference table in which the serial numbers of the strip images P0 to Pn (position information of the strip images P0 to Pn) and the reference values Ref0 to Refn are associated (see FIG. 11). . The comparison unit 15b uses reference values Ref0 to Refn suitable for each of the strip images P0 to Pn for comparison based on the reference table. Note that the last strip image acquired is not necessarily listed in the reference table. By doing in this way, the X-ray imaging apparatus 1 with a higher degree of freedom can be provided. In a subject, there is a case where it is particularly desired to increase the intensity of X-rays for a site having many bones such as a heel. Therefore, the reference value is weighted according to the positions of the strip images P0 to Pn. The reference value Refn associated with the strip image Pn is set so as to be suitable for shooting the strip image Pn + 1 to be shot next time. That is, if it is desired to increase the X-ray intensity of the strip image Pn + 1 in which the wrinkles appear, the reference value Refn associated with the strip image Pn photographed before that needs to be higher than other reference locations. Depending on the region of the subject, there are a portion with a lot of bone tissue and a portion with a lot of soft tissue. Therefore, it may be better to change the reference value referenced by the comparison unit 15b depending on the region of the subject. According to the above-described configuration, since the position information indicating the position of the strip image P and the reference value are associated with each other, the reference value can be weighted according to the region of the subject.

  (2) In the above-described embodiment, the histograms H0 to Hn for the entire area of the strip images P0 to Pn are acquired, but the present invention is not limited to this. In other words, taking the strip image P0 as an example, the histogram H0 may be generated using an elongated region adjacent to the strip image P1 adjacent to the strip image P0. By doing in this way, the exposure time suitable for acquisition of the strip image P1 can be determined.

  (3) Although the above-described first embodiment is a medical device, the present invention can also be applied to industrial and nuclear devices.

  (4) The X-ray referred to in Example 1 described above is an example of radiation in the present invention. Therefore, the present invention can be applied to radiation other than X-rays.

  (5) In the first embodiment described above, the exposure time determination unit 15 adjusts the exposure time based on the histogram H, but the present invention is not limited to this. Instead of the exposure time, the tube voltage and the tube current can be adjusted. Such adjustment is performed by the imaging condition determination unit 15c. The configuration of the imaging condition determination unit 15 c is the same as that of the exposure time determination unit 15.

1 X-ray equipment (radiography equipment)
2 Top plate 3 X-ray tube (radiation source)
4 FPD (radiation detection means)
6 X-ray tube control unit (radiation source control means)
11 Image generation unit (image generation means)
12 Histogram generator (histogram generator)
13 Upper trimming part (upper trimming means)
14 Lower trimming part (lower trimming means)
15 Shooting condition determining unit (exposure time determining means)
15a Center of gravity acquisition unit (center of gravity acquisition means)
15b Comparison part (comparison means)
18 Joining part (joining means)
21, 23 Movement means 22, 24 Movement control means 25a Reference value storage section (reference value storage means)
25b Luminance upper limit storage unit (luminance upper limit storage means)
25c Luminance lower limit storage unit (luminance lower limit storage means)
25d First shooting condition storage unit (first shooting condition storage means)

Claims (7)

A top plate on which the subject is placed;
A radiation source that emits radiation;
Radiation detection means for detecting radiation;
Moving means for moving both of the radiation source and the radiation detecting means relative to the top plate while maintaining a relative position;
Movement control means for controlling the movement means;
Image generating means for generating a fragment image based on the detection signal output from the radiation detecting means;
A histogram generating means for generating a histogram of the fragment image;
Shooting condition determining means for determining shooting conditions for the next shooting based on the histogram;
Radiation source control means for controlling the radiation source based on the imaging conditions;
And a splicing unit that splices a series of fragment images continuously moved while moving the radiation detection unit with respect to the top plate to generate a single fluoroscopic image. Radiography equipment. The radiographic apparatus according to claim 1,
The movement control means moves the radiation source and the radiation detection means in one direction when taking a series of fragment images. The radiographic apparatus according to claim 1 or 2,
Reference value storage means for storing the reference value is further provided,
The photographing condition determining means includes
Centroid acquisition means for acquiring the centroid of the histogram;
A radiation imaging apparatus comprising: a comparison unit that compares a pixel value of the center of gravity of the histogram and the reference value to determine an imaging condition. The radiographic apparatus according to claim 3,
The reference value storage means stores a reference table in which position information indicating the position of the fragment image and the reference value are associated with each other,
The comparison means obtains a reference value corresponding to a next-captured fragment image based on the reference table and a relative position of the fragment image with respect to the top plate, and compares this with a centroid of the histogram. Radiography equipment. The radiation imaging apparatus according to any one of claims 1 to 4,
Further comprising a brightness upper limit storage means for storing the brightness upper limit;
The radiographic apparatus further comprising an upper trimming unit that trims a bright side region from the histogram upper limit in the histogram so as not to use the bright side region for the centroid acquisition of the centroid acquisition unit. The radiographic apparatus according to any one of claims 1 to 5,
A luminance lower limit storage means for storing the luminance lower limit;
A radiographic apparatus, further comprising: a lower trimming unit that trims a dark side region from the lower limit of luminance in the histogram from the histogram so that the dark side region is not used for centroid acquisition of the centroid acquisition unit. The radiographic apparatus according to any one of claims 1 to 6,
First-time shooting condition storage means for storing the first-time shooting conditions is further provided,
The radiographic apparatus according to claim 1, wherein the radiographing condition determining means determines the radiographing condition of the first fragment image in a series of continuous shooting based on the initial radiographing condition.

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