JP2007160077A - Radiographic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To quickly acquire a long subtraction image in dual-energy type radiographic equipment using slot-shaped X-ray beam. <P>SOLUTION: This radiographic equipment is so formed that an X-ray beam irradiation section 1 for irradiating the slot-shaped X-ray beam and an FPD (Flat Panel type X-ray Detector) 2 for detecting a transmission X-ray image of a subject M are continuously moved along the longitudinal direction MX of the subject M by a continuous movement section 3, so that the X-ray beam irradiation section 1 and the FPD 2 can be quickly moved compared with a case where the X-ray beam irradiation section 1 and the FPD 2 are intermittently moved, so as to quickly irradiate the X-rays to the subject and detect the X-rays transmitting through the subject. Moreover, the X-ray detection signals necessary for acquiring a long high-energy X-ray image and a long low-energy X-ray image are all outputted from the FPD 2 in real time so as to quickly acquire the long high-energy X-ray image and the long low-energy X-ray image. Consequently, this equipment can quickly acquire the long subtraction image. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  In addition to using a slot-shaped (strip-shaped) radiation beam as a radiation beam to be irradiated onto a subject to be imaged, the present invention provides a high-energy radiation image when the radiation energy of the slot-shaped radiation beam is high and the slot-shaped radiation beam A dual-energy radiation imaging device using a slot-shaped radiation beam that acquires a low-energy radiation image when the radiation energy is low, and then acquires a subtraction image by processing the high-energy radiation image and the low-energy radiation image. In particular, the present invention relates to a technique for acquiring a long subtraction image.

  2. Description of the Related Art In recent years, dual energy X-ray imaging apparatuses used for diagnosis in hospitals and the like detect an X-ray tube that irradiates a subject (patient) to be imaged with an X-ray beam and a transmitted X-ray image of the subject. In addition to acquiring a high-energy X-ray image according to an X-ray detection signal output from the two-dimensional X-ray detector upon irradiation with an X-ray beam, an X-ray tube In addition to having a configuration for switching between X-ray beams with high X-ray energy and X-ray beams with low X-ray energy, a high-energy X-ray image is displayed when an X-ray beam with high X-ray energy is irradiated. It has a configuration in which a low-energy X-ray image is acquired when an X-ray beam with low X-ray energy is acquired.

In the case of a high-energy X-ray image, for example, soft tissue such as lung tissue is not shown so much and bone tissue such as ribs is conspicuous. X-rays with high energy tend to pass through the soft tissue without being absorbed so much, so the soft tissue is not clearly visible and is not noticeable.
In the case of a low-energy X-ray image, for example, a mixed image of bone tissue and soft tissue in which both soft tissue and bone tissue are shown. Since low energy X-rays are absorbed not only by bone tissue but also by soft tissue, both bone tissue and soft tissue are reflected.

  In addition, in the case of a conventional dual energy X-ray imaging apparatus, there is an apparatus configured to acquire a subtraction image by performing image subtraction processing on a high energy X-ray image and a low energy X-ray image. Image subtraction processing of high-energy X-ray images and low-energy X-ray images to acquire an image showing only bone tissue as a subtraction image, or an image showing only soft tissue Can be acquired as a subtraction image.

  In addition to this, a dual energy type X-ray imaging apparatus is proposed that uses a slot-shaped X-ray beam as an X-ray beam and uses a storage phosphor sheet as a two-dimensional X-ray detector. When a slot-shaped X-ray beam is used, there is an advantage that distortion of a transmitted X-ray image and incidence of scattered rays can be suppressed (see, for example, Patent Document 1).

JP-A-2-275582 (pages 5 to 6, FIGS. 1 to 3)

However, the conventional dual energy X-ray imaging apparatus using the slot-shaped X-ray beam has a long subtraction for imaging over a long range in the longitudinal direction of the subject (the body axis direction of the subject). There is a problem that it is difficult to quickly acquire an image.
In the case of the conventional apparatus, it is necessary to read the X-ray detection signal by putting the stimulable phosphor sheet on another image reading apparatus, and the X-ray detection signal necessary for acquiring the high energy X-ray image and the low energy X-ray image is real time. Therefore, it takes time to acquire a high-energy X-ray image or a low-energy X-ray image that is a source of the subtraction image, and it is difficult to acquire the subtraction image quickly.

  In addition, since the conventional apparatus is configured to intermittently move the X-ray tube and the two-dimensional radiation detector along the longitudinal direction of the subject, X-ray irradiation to the subject and X-rays transmitted through the subject As a result, it takes a long time to acquire a subtraction image. The X-ray tube, which is a heavy object, and the stimulable phosphor sheet, which is a two-dimensional radiation detector, are difficult to control the speed, and it is necessary to move the X-ray tube and the two-dimensional radiation detector slowly in order to move them intermittently. As a result, the time until the X-ray irradiation to the subject and the detection of the X-ray transmitted through the subject are completed becomes longer.

In particular, when a long subtraction image is acquired by photographing a long range in the longitudinal direction of the subject, the moving distance of the storage phosphor sheet that is an X-ray tube and a two-dimensional radiation detector is longer. Accordingly, the time until the transmission X-ray image of the subject is recorded on the stimulable phosphor sheet is further extended.
Therefore, in the case of a conventional apparatus, it is very difficult to quickly acquire a long subtraction image.

  The present invention has been made in view of such circumstances, and in a dual energy method using a slot-shaped radiation beam, a long subtraction image captured over a long range in the longitudinal direction of a subject is quickly obtained. It is an object of the present invention to provide a radiation imaging apparatus that can be obtained in a simple manner.

In order to achieve such an object, the invention of claim 1 has the following configuration.
That is, the radiation imaging apparatus according to the first aspect of the invention includes (A) a radiation beam irradiation means for irradiating a subject to be imaged with a slot-shaped radiation beam, and (B) a slot-shaped radiation beam to the subject. A two-dimensional radiation detection means for detecting a transmitted radiation image of a subject generated by irradiation and outputting a radiation detection signal; and (C) a radiation beam irradiation means and a two-dimensional radiation detection means relative to each other along the longitudinal direction of the subject. And (D) radiation energy switching control for switching the slot-shaped radiation beam irradiated by the radiation beam irradiation means alternately to a high energy radiation beam having a high radiation energy and a low energy radiation beam having a low radiation energy. Radiation energy switching control means, and (E) each irradiation of a high energy radiation beam adjacent to each other Are connected in the longitudinal direction of the subject to form one long high-energy radiation beam irradiation region, and each irradiation region of the adjacent low-energy radiation beam is connected in the longitudinal direction of the subject to form one long shape. A radiation irradiation timing control means for performing irradiation timing control for irradiating the radiation beam irradiation means with a slot-like radiation beam, or a moving speed control means for controlling the moving speed of the moving means so as to be in a low energy radiation beam irradiation area , (F) a long height corresponding to the transmitted radiation image of the long high energy radiation beam irradiation area according to the radiation detection signal output from the two-dimensional radiation detection means upon irradiation with the high energy radiation beam. High energy image acquisition means for acquiring energy radiation images, and (G) low energy radiation A long low-energy radiation image corresponding to the transmitted radiation image in the long low-energy radiation beam irradiation area is acquired according to the radiation detection signal output from the two-dimensional radiation detection means with the irradiation of the beam. Low energy image acquisition means, and (H) image subtraction means for acquiring a long subtraction image by performing image subtraction processing on a long high energy radiation image and a long low energy radiation image. It is characterized by being.

[Operation / Effect] When a long subtraction image is acquired by the radiation imaging apparatus according to the first aspect of the invention, first, a radiation beam irradiating means for irradiating a subject to be imaged with a slot-like radiation beam, and the subject. The two-dimensional radiation detecting means for detecting the transmitted radiation image of the subject generated by the irradiation of the slot-like radiation beam and outputting the radiation detection signal is relatively moved along the longitudinal direction of the subject by the moving means. .
The radiation beam irradiation means moving along the longitudinal direction of the subject in this way converts the slot radiation beam irradiated by the radiation beam irradiation means into a high energy radiation beam having a high radiation energy and a low energy radiation beam having a low radiation energy. Adjacent high energy radiation according to the irradiation timing control received from the radiation irradiation timing control means or the moving speed control of the moving means received from the moving speed control means while receiving the radiation energy switching control alternately switching from the radiation energy switching control means Each irradiation area of the beam is connected to the longitudinal direction of the subject to form one long high energy radiation beam irradiation area, and each irradiation area of the adjacent low energy radiation beam is connected to the longitudinal direction of the subject. One long shape So that the energy radiation beam irradiated region repeatedly slotted radiation beam is irradiated to the subject.

Then, according to the radiation detection signal output from the two-dimensional radiation detection means along with the irradiation of the high energy radiation beam, the high energy image acquisition means has a length corresponding to the transmission radiation image for the long high energy radiation beam irradiation area. A high-energy radiation image having a long shape is acquired, and the low-energy image acquisition unit emits a long low-energy radiation beam in accordance with a radiation detection signal output from the two-dimensional radiation detection unit when the low-energy radiation beam is irradiated. A long low-energy radiation image corresponding to the transmitted radiation image of the region is acquired.
Further, the image subtraction unit performs image subtraction processing on the long high-energy radiation image obtained by the high-energy image obtaining unit and the long low-energy radiation image obtained by the low-energy image obtaining unit. A subtraction image is acquired.

That is, in the case of the radiation imaging apparatus according to the first aspect of the present invention, the radiation detection signal necessary for obtaining the long high-energy radiation image and the long low-energy radiation image that are the basis of the long subtraction image is Since all are output from the two-dimensional radiation detection means, a long high-energy radiation image and a long low-energy radiation image can be quickly acquired.
Therefore, according to the radiation imaging apparatus of the first aspect of the present invention, in the dual energy type apparatus using the slot-shaped radiation beam, the long subtraction image to be imaged over a long range in the longitudinal direction of the subject is quickly obtained. Can be obtained.

  According to a second aspect of the present invention, in the radiation imaging apparatus according to the first aspect, the moving means moves the radiation beam irradiating means and the two-dimensional radiation detecting means along the longitudinal direction of the subject, and the subject is stopped. It is what has been left.

  [Operation / Effect] In the radiation imaging apparatus of the invention of claim 2, only the radiation beam irradiation means and the two-dimensional radiation detection means move along the longitudinal direction of the subject, and the subject remains stopped. Therefore, it can be avoided that the subject to be imaged moves during imaging and the position of the subject is shifted.

  According to a third aspect of the present invention, in the radiation imaging apparatus according to the first or second aspect, the radiation irradiation timing control means or the movement speed control means is provided on the adjacent side end of each irradiation region of two adjacent high energy radiation beams. The high-energy radiation beam is irradiated so that the portion becomes an overlapped irradiation region where the ends of both high-energy radiation beams overlap, and the adjacent side ends of the irradiation regions of two adjacent low-energy radiation beams are both low-energy radiation beams Are irradiated with a low energy radiation beam so as to be an overlapped irradiation region where the edges of the two overlap.

  [Operation / Effect] In the case of the radiation imaging apparatus according to the invention of claim 3, each irradiation region of two adjacent high-energy radiation beams and each irradiation region of two adjacent low-energy radiation beams are adjacent end portions. Is an overlapped irradiation region where the ends of the radiation beam overlap, so that radiation can be applied between both irradiation regions of two adjacent high-energy radiation beams and between both irradiation regions of two adjacent low-energy radiation beams. There is no risk of unirradiated gaps.

  According to a fourth aspect of the present invention, there is provided the radiation imaging apparatus according to the third aspect, wherein the high energy image acquisition means is configured to detect the radiation detection signal of the overlapping irradiation region where the ends of the high energy radiation beam overlap with each other. A weighting factor that decreases as approaching the edge is multiplied by one radiation detection signal, and the same weighting factor is multiplied by the other radiation detection signal, and then added together to obtain a pixel signal of a long high-energy radiation image, For the radiation detection signal of the overlapping irradiation area where the low energy image acquisition means overlaps the end of the low energy radiation beam, the weighting factor that decreases as it approaches the end of the low energy radiation beam is changed to one radiation detection signal. Is added to the other radiation detection signal and then added together to add a long, low energy Ray is set as the pixel signal of the image.

  [Operation / Effect] In the radiation imaging apparatus according to the invention of claim 4, the radiation detection signal of the overlapping irradiation region where the ends of the high energy radiation beam overlap and the radiation detection signal of the overlapping irradiation region where the ends of the low energy radiation beam overlap. In both cases, two radiation detection signals with the same irradiation position of the two radiation beams are multiplied by weighting factors that decrease as they approach the end of each radiation beam, and then added together to add a long high-energy radiation image. Or because it is a pixel signal of a long low-energy radiation image, a high-energy radiation beam or an overlapped irradiation region where the ends of the low-energy radiation beam overlap is a long high-energy radiation image or a long low-energy radiation. Appearing as a clear seam on the image can be avoided.

  According to a fifth aspect of the present invention, in the radiation imaging apparatus according to any one of the first to fourth aspects, the elongated high-energy radiation image acquired by the high-energy image acquisition unit and the low-energy image acquisition unit are acquired. There is a deviation of the imaging position in the direction parallel to the longitudinal direction of the subject between the long low-energy radiographic image and the image subtraction means between the high-energy radiographic image and the low-energy radiographic image. The image subtraction process is performed after the image shift process for eliminating the deviation of the photographing position.

  [Operation / Effect] In the case of the radiation imaging apparatus according to the fifth aspect of the invention, the radiation imaging apparatus is oriented in a direction parallel to the longitudinal direction of the subject existing between the long high-energy radiation image and the long low-energy radiation image. The shift of the imaging position is eliminated before the image subtraction process by the image shift process by the image subtraction means, so that the imaging position between the long high-energy radiation image and the long low-energy radiation image is not changed. It is possible to avoid the image disturbance caused by the shift from appearing on the subtraction image.

In the case of the radiation imaging apparatus of the present invention, all the radiation detection signals necessary for obtaining the long high-energy radiation image and the long low-energy radiation image that are the basis of the long subtraction image are two-dimensional radiation detection. Since it is output from the means, a long high-energy radiation image and a long low-energy radiation image can be quickly acquired.
Therefore, according to the radiation imaging apparatus of the present invention, in the dual energy method using the slot-shaped radiation beam, it is possible to quickly acquire a long subtraction image that is imaged over a long range in the longitudinal direction of the subject. it can.

  An embodiment of the radiation imaging apparatus of the present invention will be described. FIG. 1 is a block diagram showing the overall configuration of a dual-energy (medical) X-ray imaging apparatus using a slot-shaped X-ray beam according to the embodiment. FIG. 2 is a slot-shaped X-ray beam (strip) used in the apparatus of the embodiment. FIG. 3 is a flat panel X-ray detector (hereinafter abbreviated as “FPD” where appropriate) as a two-dimensional X-ray detector (two-dimensional radiation detection means) of the apparatus of the embodiment. It is a schematic diagram which shows the arrangement | sequence state of the X-ray detection element in FIG.

  As shown in FIGS. 1 and 2, the X-ray imaging apparatus of the embodiment is configured such that the slot-like X-ray beam SA is applied to the subject M to be imaged, and the short-side direction SX of the slot-like X-ray beam SA is An X-ray beam irradiating unit 1 that irradiates in a direction parallel to the direction MX, and a transmission X-ray image of the subject M generated by the irradiation of the subject M with the slot-like X-ray beam SA and detecting an X-ray detection signal An FPD 2 that outputs in real time, and a continuous movement unit 3 that continuously moves the X-ray beam irradiation unit 1 and the FPD 2 along the longitudinal direction MX of the subject M while the subject M is stopped.

The X-ray beam irradiation unit 1 includes an X-ray tube 4 and a collimator 5 that shapes the X-ray beam into a slot shape. The short-side direction SX of the slot-shaped X-ray beam SA is parallel to the longitudinal direction MX of the subject M. Therefore, the longitudinal direction SY of the slot-shaped X-ray beam SA is perpendicular to the longitudinal direction MX of the subject M.
As shown in FIG. 3, the FPD 2 includes a large number of X-ray detection elements 2 </ b> A that detect X-rays by converting them into electrical signals on an X-ray detection surface Xa on which a transmission X-ray image to be detected is projected. They are arranged in a two-dimensional matrix. As an array matrix of the X-ray detection element 2A, for example, horizontal: several thousand × vertical: several thousand can be mentioned. The X-ray detection element 2A is a direct conversion type in which X-rays are directly converted into electric signals, but may be an indirect conversion type in which X-rays are once converted into light and then converted into electric signals.

An imaging system including the X-ray beam irradiation unit 1 and the FPD 2 is attached to one end side and the other end side of the attachment arm 7 with the top plate 6 on which the subject M is placed, and is attached to the attachment arm 7 by the continuous moving unit 3. Is configured to be continuously moved along the longitudinal direction MX of the subject M together with the X-ray beam irradiation unit 1 and the FPD 2.
The continuous moving unit 3 includes mechanical parts such as a rack and a pinion, and includes an imaging system continuous moving mechanism 8 that reciprocates the mounting arm 7 along the longitudinal direction MX of the subject M, an X-ray beam irradiation unit 1, and an FPD 2. Imaging system continuous movement control unit 9 for starting and stopping or controlling the moving speed, and imaging system continuous movement mechanism 8 continuously connects X-ray beam irradiation unit 1 and FPD 2 in accordance with the control of imaging system continuous movement control unit 9. Move.

  On the other hand, the X-ray beam irradiation unit 1 irradiates the X-ray tube 4 with the slot-shaped X-ray beam SA every time X-ray tube driving power is supplied from the X-ray power supply 10. X-ray energy switching control for alternately switching the slot-shaped X-ray beam SA irradiated by the X-ray beam irradiation unit 1 to a high-energy X-ray beam having high energy and a low-energy X-ray beam having low X-ray energy An energy switching control unit 11 is provided. Specifically, the X-ray energy switching control unit 11 sets the high voltage of the high voltage generator 10A of the X-ray power supply 10 to a higher voltage (for example, 140 kV) for the high energy X-ray beam and a lower voltage for the low energy X-ray beam. X-ray energy switching control is performed by alternately switching to a voltage (for example, 60 kV).

  In other words, in the case of the apparatus of the embodiment, the X-ray energy switching control unit 11 performs X-rays while the X-ray beam irradiation unit 1 and the FPD 2 are continuously moved along the longitudinal direction MX of the subject M by the operation of the continuous movement unit 3. By the energy switching control, the X-ray beam irradiation unit 1 alternately and repeatedly irradiates the subject M with the high energy X-ray beam and the low energy X-ray beam, and the FPD 2 generates a transmission X-ray image every time the X-ray beam is irradiated. It detects and outputs an X-ray detection signal in real time. In other words, the subject M is repeatedly irradiated with the high-energy slot-shaped X-ray beam SA and the low-energy slot-shaped X-ray beam SA from the X-ray beam irradiation unit 1 along the longitudinal direction. Each time the X-ray beam SA is irradiated, the slot-like transmitted X-ray image is detected by the FPD 2 one by one.

  On the other hand, in the apparatus of the embodiment, each irradiation area of the high energy X-ray beam is connected in the longitudinal direction of the subject M without a gap between adjacent irradiation areas of the high energy X-ray beam in the object M. Each of the low-energy X-ray beams without any gaps between adjacent irradiation regions of the low-energy X-ray beam in the subject M. Are controlled in such a manner that the X-ray beam irradiation unit 1 is irradiated with the slot-like X-ray beam SA at the timing when the X-ray beam irradiation unit 1 is connected to the longitudinal direction of the subject M to become one long low-energy X-ray beam irradiation region. A line irradiation timing control unit 12 is provided.

  That is, at the stage where the irradiation of the slot-shaped X-ray beam SA is completed, as shown in FIG. 4A, the irradiation areas Ha of the high-energy X-ray beam are controlled by the irradiation timing control by the X-ray irradiation timing control unit 12. Are connected in the longitudinal direction of the subject M without leaving a gap to form one long high-energy X-ray beam irradiation area HA. As shown in FIG. 4B, each irradiation with a low-energy X-ray beam is performed. The area La is joined in the longitudinal direction of the subject M without leaving a gap to form one long low energy X-ray beam irradiation area LA.

  Furthermore, the apparatus according to the embodiment corresponds to a transmission X-ray image of the long high energy X-ray beam irradiation area HA according to the X-ray detection signal output from the FPD 2 when the high energy X-ray beam is irradiated. A high-energy image acquisition unit 13 that acquires a long high-energy X-ray image, and a long low-energy X-ray according to an X-ray detection signal output from the FPD 2 upon irradiation with a low-energy X-ray beam And a low energy image acquisition unit 14 that acquires a long low energy X-ray image corresponding to the transmitted X-ray image of the beam irradiation area LA.

  Specifically, as shown in FIG. 5, for example, when a high energy X-ray beam is irradiated in a period T1 of about 2 mSEC, an X-ray detection signal output in real time from the FPD 2 is output from the memory selector 15 in the subsequent period T3. It is sent to the high energy image acquisition unit 13 via the first slot image memory 16. An X-ray detection signal output with one high-energy X-ray beam corresponds to one slot image. The high-energy image acquisition unit 13 sequentially joins the slot-like images sent one after another along the longitudinal direction of the subject M, and as shown in FIG. A line image Pa is acquired. As shown in FIG. 6A, the high-energy X-ray image Pa is an image in which bone tissue such as ribs is conspicuous without much soft tissue such as organ tissue such as lung and stomach being shown.

  Next, as shown in FIG. 5, for example, when a low energy X-ray beam is irradiated in a period T2 of about 10 mSEC, an X-ray detection signal output in real time from the FPD 2 is output from the memory selector 15 in the second period T4. It is sent to the low energy image acquisition unit 14 via the slot image memory 17. An X-ray detection signal output with one low energy X-ray beam also corresponds to one slot-like image. The low energy image acquisition unit 14 sequentially joins the slot-like images sent one after another along the longitudinal direction of the subject M, and as shown in FIG. The line drawing Pb is acquired. As shown in FIG. 6B, the low-energy X-ray image is, for example, a mixed image of bone tissue and soft tissue in which both soft tissue and bone tissue are shown.

  In addition, the apparatus according to the embodiment includes an image subtraction unit 18 that obtains a long subtraction image by performing image subtraction processing on a long high energy X-ray image and a long low energy X-ray image. ing. The image subtraction unit 18 is a long high-energy X-ray image Pa acquired by the high-energy image acquisition unit 13 and sent via the high-energy image memory 19, and the low-energy image acquired by the low-energy image acquisition unit 14. A long subtraction image is obtained by weighting the long low-energy X-ray image Pb sent via the memory 20 by an appropriate coefficient and then subtracting it.

That is, the image subtraction unit 18 performs an operation of subtracting an image of a × log (pixel signal of a long high energy X-ray image Pa) −b × log (pixel signal of a long low energy X-ray image Pb). Performed by image subtraction processing.
Therefore, by appropriately adjusting the coefficient a and the coefficient b of the calculation for subtracting the above image, for example, as shown in FIG. 7, an image in which only bone tissue such as the ribs and the spine is reflected is subtracted. It can be acquired as PA. Of course, it is also possible to acquire an image in which only the soft tissue is substantially reflected by adjusting the coefficients a and b as a subtraction image.
The long subtraction image acquired by the image subtraction unit 18 is stored in the subtraction image memory 21 and displayed on the screen of the display monitor 22 as necessary.

Further, a menu for performing operations necessary for X-ray imaging and operation of the apparatus is displayed on the screen of the display monitor 22. When inputting commands and data necessary for X-ray imaging and operation of the apparatus, an operation for inputting commands and data is performed from the operation unit 23 using an input device such as a mouse or a keyboard.
The main control unit 24 is mainly composed of a computer (CPU) and an operation program, and appropriate commands and data are input according to various command inputs from the operation unit 23 or the like, or the progress of X-ray imaging. Is sent to the necessary parts in a timely manner, and the overall control function is performed so that the entire device is always properly operated.

In the case of the apparatus of the embodiment, the width (the dimension in the short direction SX) W of the slot-shaped X-ray beam SA, the moving speed of the X-ray beam irradiation unit 1 and the FPD 2 can be set by an input operation of the operation unit 23 or the like. It is configured.
The width W of the slot-shaped X-ray beam SA is usually set to a range of several centimeters, for example, about 1 cm to 5 cm. The moving speed of the X-ray beam irradiation unit 1 and the FPD 2 is set to a moving speed of, for example, about several centimeters / second (specifically, 1 cm / second to 5 cm / second) because an image is blurred if it is too fast.

  Therefore, the width W of the slot-shaped X-ray beam SA is 4 cm, the moving speed of the X-ray beam irradiation unit 1 and the FPD 2 is 4 cm / second, and the length of the long subtraction image to be acquired is 80 cm. In this case, the total movement time of the X-ray beam irradiation unit 1 and the FPD 2 is 25 seconds, and the slot-shaped X-ray beam SA is about 20 times each of the high-energy X-ray beam and the low-energy X-ray beam about 40 times. When the length of the long subtraction image is about 1 m, the total movement time of the X-ray beam irradiation unit 1 and the FPD 2 is 25 seconds, and the slot-like X-ray beam SA is high energy X The total number of irradiations is 50, that is, approximately 25 times for each of the beam and the low energy X-ray beam.

On the other hand, in the case of the apparatus according to the embodiment, the X-ray irradiation timing control unit 12 is configured according to the width W of the slot-shaped X-ray beam SA and the moving speed of the X-ray beam irradiation unit 1 and the FPD 2 as shown in FIG. The irradiation area Ha of the high energy X-ray beam and the irradiation area La of the low energy X-ray beam are divided into the irradiation area Ha of the high energy X-ray beam and the irradiation area La of the low energy X-ray beam in the longitudinal direction MX of the subject M. Is irradiated at a timing at which the dimensional difference ΔL becomes half (W / 2) of the width W of each irradiation area.
In addition, as shown in FIG. 9, the X-ray irradiation timing control unit 12 overlaps the adjacent side ends of the irradiation areas Ha of two adjacent high-energy X-ray beams so that the ends of both high-energy X-ray beams overlap. Overlapping irradiation regions where the high energy X-ray beams are irradiated at the timing of the irradiation region Qa, and the adjacent side ends of the irradiation regions La of two adjacent low energy X-ray beams overlap the ends of both low energy X-ray beams A low energy X-ray beam is irradiated at the timing of Qb.

  Therefore, in the case of the apparatus according to the embodiment, each irradiation region Ha of two adjacent high-energy X-ray beams and each irradiation region La of two adjacent low-energy X-ray beams have X-ray beams at the adjacent side ends. The overlapping irradiation region Qa or the overlapping irradiation region Qb overlaps with each other, so that both irradiation regions Ha of the two adjacent high energy X-ray beams are also irradiated between the two irradiation regions Ha of the two adjacent low energy X-ray beams. There is no possibility that a gap not irradiated with X-rays is generated between La.

  In addition, in the case of the apparatus of the embodiment, the high energy image acquisition unit 13 decreases the X-ray detection signal of the overlapped irradiation region Qa where the ends of the high energy X-ray beams overlap as it approaches the end of the high energy X-ray beams. The weighting factor k1 to be multiplied by one X-ray detection signal and the same weighting factor k2 are multiplied by the other X-ray detection signal and then added to obtain a pixel signal of a long high-energy X-ray image. Similarly, for the X-ray detection signal of the overlapping irradiation region Qb where the ends of the low-energy X-ray beams overlap, the low-energy image acquisition unit 14 reduces the weighting factor k1 that decreases as one approaches the end of the low-energy X-ray beams. The X-ray detection signal is multiplied by a similar weighting factor k2 to the other X-ray detection signal and then added to obtain a pixel signal of an elongated low-energy X-ray image.

  Therefore, in the case of the apparatus of the embodiment, the X-ray detection signal of the overlapped irradiation region Qa where the ends of the high energy X-ray beam overlap and the X-ray detection signal of the overlapped irradiation region Qb where the ends of the low energy X-ray beam overlap. In either case, the two X-ray detection signals having the same irradiation position of the two X-ray beams are multiplied by the weighting factor k1 or the weighting factor k2 that decreases as they approach the end of each X-ray beam, and then added together. Since the pixel signal of the high energy X-ray image or the long low energy X-ray image is the overlapping irradiation region Qa or the overlapping irradiation region Qb where the ends of the high energy X-ray beam or the low energy X-ray beam overlap, Appearance as a clear seam on a long high energy X-ray image or a long low energy X-ray image can be avoided.

The weighting factor k1 and the weighting factor k2 to be multiplied by the X-ray detection signal of the overlapping irradiation region Qa or the overlapping irradiation region Qb where the ends of the X-ray beam overlap are as follows. In both cases, the weight coefficient k1 and the weight coefficient k2 are both 0 at the end of the overlapping irradiation region, and the weight coefficient k1 + weight coefficient k2 = 1 always holds.
As a method of decreasing the weighting factor that decreases as it approaches the end of the X-ray beam, as shown in FIG. 10, it decreases along a straight line, or as shown in FIG. 11, sin ² θ and cos ² θ. The form which decreases along the curve of (1) is mentioned.

  In the case of the apparatus of the embodiment, as shown in FIG. 8, the start point of the irradiation area Ha of the high energy X-ray beam and the start point of the irradiation area La of the low energy X-ray beam are parallel to the longitudinal direction MX of the subject M. Since the direction is shifted by a dimension difference ΔL, the dimension difference ΔL is also between the long high energy X-ray image and the long low energy X-ray image in the direction parallel to the longitudinal direction MX of the subject M. However, the image subtraction unit 18 is configured to perform the image subtraction process after performing the image shift process for eliminating the shift of the shooting position of the dimensional difference ΔL. Therefore, in the apparatus of the embodiment, image disturbance due to a shift in the imaging position between the long high-energy X-ray image and the long low-energy X-ray image appears on the subtraction image. Can be avoided.

As described above, in the case of the apparatus according to the embodiment, the X-ray beam irradiation unit 1 for irradiating the slot-shaped X-ray beam and the FPD 2 for detecting the transmitted X-ray image of the subject M are connected by the continuous moving unit 3. Since the X-ray beam irradiating unit 1 and the FPD 2 are moved intermittently along the longitudinal direction MX of the M, the X-ray beam irradiating unit 1 and the FPD 2 can be moved quickly compared to the case where the X-ray beam irradiating unit 1 and the FPD 2 are moved intermittently. The X-ray irradiation to the specimen and the detection of the X-ray transmitted through the subject can be completed quickly.
In addition, in the case of the apparatus of the embodiment, all the X-ray detection signals necessary for obtaining the long high-energy X-ray image and the long low-energy X-ray image that are the basis of the long subtraction image are all. Since it is output from the FPD 2 in real time, a long high energy X-ray image and a long low energy X-ray image can be quickly acquired.

Therefore, according to the apparatus of the embodiment, in a dual energy system apparatus using a slot-shaped X-ray beam, a long subtraction image captured over a long range in the longitudinal direction of the subject can be quickly acquired. Can do.
In the apparatus of the embodiment, only the X-ray beam irradiation unit 1 and the FPD 2 continuously move along the longitudinal direction of the subject M, and the subject M remains stopped. It can be avoided that the subject M moves during imaging and the position of the subject M shifts.

The present invention is not limited to the above embodiment, and can be modified as follows.
(1) In the case of the apparatus of the example, only the X-ray beam irradiation unit 1 and the FPD 2 continuously move along the longitudinal direction of the subject M, and the subject M remains stopped. An apparatus having the same configuration as that of the embodiment can be cited as a modified example, except that the line beam irradiation unit 1 and the FPD 2 are stopped and only the subject M is continuously moved along the longitudinal direction. .

  (2) In the apparatus of the embodiment, the two-dimensional X-ray detector is an FPD, but the two-dimensional X-ray detector may be a detector other than the FPD.

  (3) Although the apparatus of the embodiment is a medical X-ray imaging apparatus, the present invention can also be applied to X-ray imaging apparatuses other than medical use.

  (4) In the case of the apparatus of the embodiment, the apparatus uses X-rays as radiation, but the present invention can also be applied to an apparatus using radiation other than X-rays (for example, γ-rays).

  (5) Although the apparatus of the embodiment includes the X-ray irradiation timing control unit 12 that performs the irradiation timing control for irradiating the X-ray beam irradiation unit 1 with the slot-shaped X-ray beam SA, as shown in FIG. The present invention can also be applied to an apparatus including a moving speed control unit 25 that controls the moving speed of the moving unit 3.

  In this case, each irradiation area Ha of the high energy X-ray beam is joined in the longitudinal direction of the subject M without leaving a gap to form one long high energy X-ray beam irradiation area HA. The moving speed control unit 25 continuously moves so that each irradiation area La of the beam is joined in the longitudinal direction of the subject M without leaving a gap to form one long low energy X-ray beam irradiation area LA. The moving speed of the unit 3 is controlled. Further, the moving speed control unit 25 has a high energy at a moving speed at which the adjacent side ends of the irradiation areas Ha of two adjacent high energy X-ray beams become the overlapping irradiation areas Qa where the ends of both high energy X-ray beams overlap. While irradiating the X-ray beam, the adjacent side end of each irradiation region La of two adjacent low-energy X-ray beams also has a low energy X at a moving speed that becomes an overlapping irradiation region Qb where the ends of both low-energy X-ray beams overlap. Irradiate a line beam.

  The X-ray irradiation timing control unit 12 operates the X-ray beam irradiation unit 1 via the X-ray power supply 10 in order to control the irradiation timing, but the moving speed control unit 25 performs the moving speed control. The imaging system continuous movement mechanism 8 of the continuous movement unit 3 is operated.

  (6) In the apparatus according to the embodiment, each irradiation region of the high energy X-ray beam extends in the longitudinal direction of the subject M without a gap between adjacent irradiation regions Ha of the high energy X-ray beam in the subject M. The two high-energy X-ray beam irradiation areas HA are connected to each other, and a low-energy X-ray beam is not formed between the irradiation areas La of adjacent low-energy X-ray beams in the subject M. Although each of the irradiation areas is controlled to be connected to the longitudinal direction of the subject M so as to become one long low energy X-ray beam irradiation area LA, there is not necessarily a gap between the irradiation areas. There is no need to control. Even if there is a gap, a high energy X-ray beam irradiation area or a low energy X-ray beam irradiation area may be formed by interpolating the gap area between the irradiation areas.

  (7) The apparatus of the embodiment irradiates the slot-shaped X-ray beam SA in such a direction that the short direction SX of the slot-shaped X-ray beam SA is parallel to the longitudinal direction MX of the subject M. If SA is an apparatus that can irradiate at least the longitudinal direction MX of the subject M, it can be applied to that apparatus.

  (8) In the apparatus of the embodiment, the FPD 2 outputs the X-ray detection signal in real time, but after the FPD 2 outputs the X-ray detection signal, the X-ray detection signal is temporarily written and stored, and then sequentially read out. It can also be applied to an output device.

  (9) Although the X-ray beam irradiation unit 1 and the FPD 2 are relatively continuously moved along the longitudinal direction MX of the subject M, the apparatus of the embodiment can be applied to an apparatus that moves intermittently.

It is a block diagram which shows the whole structure of the X-ray imaging device of an Example. It is a perspective view which shows the slot-shaped X-ray beam used with the apparatus of an Example. It is a schematic diagram which shows the arrangement | sequence state of the X-ray detection element in FPD of the apparatus of an Example. It is a typical top view which shows the elongate high energy X-ray beam irradiation area | region and the elongate low energy X-ray beam irradiation area | region in the apparatus of an Example. It is a graph which shows the time-dependent change of the output voltage of the high voltage generation | occurrence | production part in the apparatus of an Example, and the output condition of a X-ray detection signal. It is a schematic diagram which shows the elongate high energy X-ray image and the elongate low energy X-ray image which are acquired with the apparatus of an Example. It is a schematic diagram which shows the elongate subtraction image acquired with the apparatus of an Example. It is a schematic diagram which shows the dimensional difference which arises between the irradiation area | region of a high energy X-ray beam and the irradiation area | region of a low energy X-ray beam in the apparatus of an Example. It is a schematic diagram which shows the overlapping irradiation area | region which arises between the irradiation area | regions of a high energy X-ray beam or a low energy X-ray beam in the apparatus of an Example. It is a graph for demonstrating an example of the weighting coefficient which multiplies the X-ray detection signal of the overlapped irradiation area | region where the edge of an X-ray beam overlaps in the apparatus of an Example. It is a graph for demonstrating the other example of the weighting coefficient which multiplies the X-ray detection signal of the overlapped irradiation area | region with which the edge of an X-ray beam overlaps in the apparatus of an Example. It is a block diagram which shows the whole structure of the X-ray imaging device of a modification.

Explanation of symbols

1 ... X-ray beam irradiation unit 2 ... FPD
DESCRIPTION OF SYMBOLS 3 ... Continuous movement part 11 ... X-ray energy switching control part 12 ... X-ray irradiation timing control part 13 ... High energy image acquisition part 14 ... Low energy image acquisition part 18 ... Image subtraction part 25 ... Movement speed control part HA ... Long High energy X-ray beam irradiation area Ha ... High energy radiation beam irradiation area LA ... Long low energy X-ray beam irradiation area La ... Low energy radiation beam irradiation area k1, k2 ... Weighting factor M ... Subject MX ... Longitudinal direction of the subject PA ... Long subtraction image Pa ... Long high energy X-ray image Pb ... Long low energy X-ray image Qa, Qb ... Overlapping irradiation area SA ... Slot shape X-ray beam SX ... Short direction (of slot-shaped X-ray beam)

Claims (5)

  (A) a radiation beam irradiating means for irradiating a subject to be imaged with a slot-shaped radiation beam; and (B) a radiation detection signal by detecting a transmitted radiation image of the subject generated by the irradiation of the subject with a slot-shaped radiation beam. Two-dimensional radiation detection means for outputting the radiation, (C) a radiation means for irradiating the radiation beam and the two-dimensional radiation detection means for relatively moving along the longitudinal direction of the subject, and (D) irradiation by the radiation beam irradiation means. A radiation energy switching control means for performing radiation energy switching control for alternately switching a slot-shaped radiation beam to a high energy radiation beam having a high radiation energy and a low energy radiation beam having a low radiation energy, and (E) an adjacent high energy radiation beam Each irradiation area is connected to the longitudinal direction of the subject to form one long high In the radiation beam irradiation means, each irradiation region of adjacent low energy radiation beams is connected in the longitudinal direction of the subject to form one long low energy radiation beam irradiation region. Radiation irradiation timing control means for performing irradiation timing control for irradiating the slot-shaped radiation beam, or movement speed control means for controlling the movement speed of the moving means, and (F) two-dimensional radiation detection accompanying irradiation with a high energy radiation beam High energy image acquisition means for acquiring a long high energy radiation image corresponding to a transmitted radiation image for a long high energy radiation beam irradiation area according to a radiation detection signal output from the means; and (G) low Output from the two-dimensional radiation detection means with the irradiation of the energy radiation beam Low energy image acquisition means for acquiring a long low energy radiation image corresponding to the transmitted radiation image for the long low energy radiation beam irradiation area according to the ray detection signal, and (H) a long high energy A radiation imaging apparatus comprising: an image subtraction unit configured to perform image subtraction processing on a radiation image and a long low-energy radiation image to obtain a long subtraction image.   The radiation imaging apparatus according to claim 1, wherein the moving means moves the radiation beam irradiating means and the two-dimensional radiation detecting means along the longitudinal direction of the subject, and the subject remains stopped.   3. The radiation imaging apparatus according to claim 1, wherein the radiation irradiation timing control means or the movement speed control means is configured such that the adjacent side ends of the irradiation regions of two adjacent high energy radiation beams are the ends of both high energy radiation beams. Are irradiated with a high energy radiation beam so that they overlap each other, and adjacent end portions of the irradiation regions of two adjacent low energy radiation beams become overlapping irradiation regions where the ends of both low energy radiation beams overlap. A radiation imaging apparatus that irradiates a low energy radiation beam.   The radiation imaging apparatus according to claim 3, wherein the high-energy image acquisition unit sets a weighting factor that decreases as the end of the high-energy radiation beam approaches the end of the high-energy radiation beam for the radiation detection signal of the overlapping irradiation region where the ends of the high-energy radiation beam overlap. The same weighting factor is multiplied to one radiation detection signal and then added to the other radiation detection signal, and added to form a pixel signal of an elongated high energy radiation image. For the radiation detection signal of the overlapping irradiation area where the ends of the radiation beam overlap, the weighting factor that decreases as it approaches the end of the low energy radiation beam is set to one radiation detection signal, and the same weighting factor is set to the other radiation detection signal. The pixel signal of the long low-energy radiation image is added together after multiplication. Radiation imaging apparatus.   5. The radiation imaging apparatus according to claim 1, wherein a long high-energy radiation image acquired by a high-energy image acquisition unit and a long low-energy radiation acquired by a low-energy image acquisition unit. An image shift in which there is a deviation of the imaging position in the direction parallel to the longitudinal direction of the subject between the images and the image subtraction means eliminates the deviation of the imaging position between the high energy radiation image and the low energy radiation image A radiation imaging apparatus that performs image subtraction processing after performing processing.

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