JP2015123317A - Radiographic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiographic apparatus capable of accurately overlapping a blood vessel image with a live image even if a top board moves during moving image shooting.SOLUTION: A radiographic apparatus includes a stereoscopic image editing section 13 which moves a blood vessel image of a subject on data in accordance with the movement amount of a top board 2 output from a potentiometer 25. However, if trying to grasp the movement of the top board 2 only based on the potentiometer 25, a deviation occurs at the time of overlapping of a moving image and the blood vessel image. In this invention, the movement of the top board 2 is actually measured by imaging a phantom in plural times while changing the position of the top board 2. By considering the actually-measured data, the moving image and the projection image can be overlapped with each other without a deviation even if there are an error in the potentiometer 25 and a deviation in the movement direction of the top board 2.

Description

  The present invention relates to a radiation imaging apparatus that acquires a live image by irradiating a subject with radiation, and particularly relates to a radiation imaging apparatus that can display an image acquired in advance on a live image. .

  Medical institutions are equipped with a radiation imaging apparatus that acquires an image of a subject with radiation. The configuration of such a conventional apparatus will be described. According to the conventional configuration, as shown in FIG. 17, the radiation source 53 for irradiating radiation and the FPD 54 for detecting radiation are included. The radiation source 53 and the FPD 54 are supported by a C arm 57. A subject to be imaged is placed on a top plate 52 located between the radiation source 53 and the FPD 54 (see, for example, Patent Document 1).

  Such a radiation imaging apparatus can continuously perform fluoroscopy of a subject and generate a moving image (live image). The surgeon can perform various treatments by inserting the catheter into the blood vessel of the subject while visually recognizing the live image. Such a live image clearly shows the bone of the subject and the catheter itself.

  However, such an imaging method is not suitable for clearly imaging the blood vessels of the subject. This is because blood vessels are difficult to image by radiation unlike catheters. If it is not known how the blood vessel extends in the subject, the insertion of the operator's catheter will be hindered.

  In order to solve such a problem, a configuration in which a blood vessel image indicating the position of a blood vessel is superposed on a live image has been conventionally devised. That is, a blood vessel image of a subject is photographed using a blood vessel contrast agent before the catheter insertion operation, and the blood vessel image is superimposed on the live image and displayed. Then, the operator can understand which part of the blood vessel of the subject reaches the catheter, and can smoothly perform the catheter insertion operation.

  A blood vessel image, which is a two-dimensional image superimposed on a live image, is generated based on a three-dimensional image of a blood vessel. This three-dimensional image is taken prior to taking a live image, and is taken by a radiation imaging apparatus based on the same principle as a CT apparatus. That is, the three-dimensional image of the blood vessel is acquired by performing continuous shooting of images while rotating the radiation source 53 and the FPD 54 around the subject and reconstructing these images. An image obtained by projecting this three-dimensional image onto a plane is a blood vessel image, which is an image that clearly represents the position of the blood vessel that is not obvious in the live image.

  By the way, the top plate 52 can move in the body axis direction of the subject. With such a configuration, the surgeon can change the field of view of the live image so that the operation can be easily performed by moving the subject with respect to the C-arm 57.

JP 2010-193965 A

However, the conventional configuration has the following problems.
That is, according to the conventional configuration, a shift occurs between the blood vessel image and the live image while the top plate 52 is moved.

  As described above, there are two types of imaging by the radiographic apparatus, one relating to acquisition of a three-dimensional image of blood vessels and one relating to acquisition of a live image. If the top plate 52 is not moved during the two imaging operations, no deviation occurs between the live image and the blood vessel image superimposed thereon. The conventional configuration is based on this concept.

  However, in an actual operation site, the top plate 52 may be moved after taking a three-dimensional image of the blood vessel. When the top plate 52 is moved during the shooting of the live image, the subject reflected in the live image moves so as to scroll the whole. On the other hand, since the blood vessel image is generated when the top plate 52 is at the initial position, it cannot follow this movement and remains at the same position.

  Then, the live image and the blood vessel image, which are overlapped with each other at the beginning of shooting of the live image, are displaced due to a positional shift as the top plate 52 moves. When such a divergence occurs, the blood vessel image superimposed on the live image does not represent the position of the blood vessel that should be in the live image, which hinders accurate surgery.

  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 accurately superimposing a live image on a blood vessel image even if the top plate moves. is there.

The present invention has the following configuration in order to solve the above-described problems.
That is, the radiographic apparatus according to the present invention includes a top plate on which a subject is placed, a top plate driving unit that moves the top plate, a top plate drive control unit that controls the top plate driving unit, and a movement of the top plate. A sensor for detecting an amount; a radiation source for irradiating the subject with radiation; a detection means for detecting radiation transmitted through the subject; an arm supporting the radiation source and the detection means; and radiation by driving the arm. Arm driving means for rotating the source and detecting means, arm driving control means for controlling the arm driving means, and moving image generating means for connecting a series of radiation images obtained by continuously shooting the subject in the order of imaging to generate a moving image A three-dimensional image generating means for generating a three-dimensional image of the subject based on a series of radiographic images continuously taken while rotating the radiation source and the detection means with respect to the subject; Projection image generation means for generating a projection image projected on a two-dimensional plane, and the amount of movement of the sensor output based on the imaging result obtained by imaging the phantom multiple times by changing the position of the top plate Correction means for correcting the error, editing means for adding editing for moving the three-dimensional image or projection image of the subject on the data by the corrected movement amount in the direction of movement of the top plate obtained by phantom imaging, and projection onto the moving image And display means for displaying an image in a superimposed manner.

[Operation and Effect] According to the present invention, it is possible to provide a radiation imaging apparatus capable of accurately superimposing a live image on a blood vessel image even if the top plate moves. That is, according to the present invention, the editing is performed to move the stereoscopic image or the projected image of the subject on the data according to the movement amount of the top plate output from the sensor, so that the moving image with the top plate moves on the moving image. An editing means for causing the image on the data to follow the image is provided. As a result, the projected image can be moved following a moving image that naturally moves as the top plate moves.
However, if only the sensor is used to grasp the movement of the top plate, a deviation occurs when the moving image and the projected image are superimposed. Therefore, in the present invention, the movement of the top plate is measured by photographing the phantom a plurality of times while changing the position of the top plate. In consideration of such actually measured data, even if the sensor has an error or a deviation in the moving direction of the top plate, the moving image and the projected image can be superimposed without any deviation.

  In the above-described radiation imaging apparatus, it is more desirable that the imaging result used by the editing means for the operation is a phantom stereoscopic image.

  [Operation / Effect] The above-described configuration more specifically represents the present invention. If the photographing result used by the editing means for the operation is a three-dimensional image of the phantom, the movement of the top can be captured three-dimensionally, and more accurate image alignment is possible.

  In the above-described radiographic apparatus, the correction unit corrects the movement amount error based on a coefficient for converting the movement distance detected by the sensor obtained from the imaging result of the phantom into the actual movement distance of the top board. desirable.

  [Operation / Effect] The above-described configuration more specifically represents the present invention. If the sensor output value is corrected with a coefficient that converts the movement distance detected by the sensor into the actual movement distance of the top plate, sensor errors can be absorbed and more accurate image alignment is possible. It becomes.

  Further, in the above-described radiographic apparatus, it is more desirable that the actual moving direction of the top board obtained from the imaging result of the phantom used when the editing unit operates is expressed as vector data.

  [Operation / Effect] The above-described configuration more specifically represents the present invention. By operating based on the vector data indicating the actual direction of movement of the top plate, even if the direction of movement of the top plate deviates from the ideal, this deviation can be absorbed reliably and more accurate image alignment is possible. It becomes.

  In the above-described radiation imaging apparatus, it is more desirable that the distribution of blood vessels in the subject is reflected in the stereoscopic image and the projected image of the subject.

  [Operation / Effect] The above-described configuration more specifically represents the present invention. If the distribution of blood vessels in the subject is reflected in the stereoscopic image and the projection image of the subject, the blood vessel image is superimposed on the moving image, and a radiation imaging apparatus that can easily perform surgery can be provided.

  Moreover, in the above-described radiographic apparatus, it is more desirable if it is for catheter insertion operation.

  [Operation / Effect] The above-described configuration more specifically represents the present invention. The present invention is particularly suitable for catheter insertion operations.

  ADVANTAGE OF THE INVENTION According to this invention, even if a top plate moves, the radiography apparatus which can superimpose a live image on a blood vessel image correctly can be provided. That is, according to the present invention, there is provided editing means for moving the blood vessel image of the subject on the data according to the movement amount of the top plate output from the sensor. However, if only the sensor is used to grasp the movement of the top plate, a deviation occurs when the moving image and the blood vessel image are superimposed. Therefore, in the present invention, the movement of the top plate is measured by photographing the phantom a plurality of times while changing the position of the top plate. In consideration of such actually measured data, even if the sensor has an error or a deviation in the moving direction of the top plate, the moving image and the projected image can be superimposed without any deviation.

1 is a functional block diagram illustrating an overall configuration of an X-ray imaging apparatus according to Embodiment 1. FIG. FIG. 3 is a schematic diagram illustrating a configuration of a C arm according to the first embodiment. It is a schematic diagram explaining the structure of the top plate which concerns on Example 1. FIG. 6 is a schematic diagram illustrating a configuration of a projection image generation unit according to Embodiment 1. FIG. 1 is a schematic diagram illustrating a phantom according to a first embodiment. It is a schematic diagram explaining a mode that the phantom which concerns on Example 1 is image | photographed. It is a schematic diagram explaining the movement of the top plate which concerns on Example 1, and the displacement of the phantom accompanying it. FIG. 6 is a schematic diagram illustrating operations of a distance correction coefficient calculation unit and a vector data calculation unit according to the first embodiment. 3 is a flowchart for explaining the operation of the X-ray imaging apparatus according to Embodiment 1; FIG. 3 is a schematic diagram illustrating a situation where a stereoscopic image according to Example 1 is captured. It is a schematic diagram explaining a mode that the moving image which concerns on Example 1 is image | photographed. It is a schematic diagram explaining the superimposed moving image according to the first embodiment. It is a schematic diagram explaining a state that a top plate is moved during imaging | photography of the moving image which concerns on Example 1. FIG. It is a schematic diagram explaining the shift | offset | difference of the image on the superimposition animation which appears with the movement of the top plate which concerns on Example 1. FIG. FIG. 6 is a schematic diagram illustrating an operation of a stereoscopic image editing unit according to the first embodiment. It is a schematic diagram explaining the superimposed moving image according to the first embodiment. It is a schematic diagram explaining the structure of the radiography apparatus of a conventional structure.

  The X-ray imaging apparatus according to the present invention is a C-arm type for catheter insertion operation. Hereinafter, details of the X-ray imaging apparatus according to the present invention will be described. Note that FPD is an abbreviation for flat panel detector, and X-rays correspond to the radiation of the present invention.

<Configuration of X-ray imaging apparatus>
As shown in FIG. 1, an X-ray 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 emits X-rays provided below the top plate 2. The FPD 4 that detects X-rays transmitted through the subject M provided above the top 2, the X-ray tube controller 6 that controls the tube current and tube voltage of the X-ray tube 3, and the X-ray tube 3 , A C arm 7 that supports the FPD 4, a support column 8 that supports the C arm 7, a C arm rotation mechanism 21 that rotates the C arm 7, and a C arm rotation control unit 22 that controls the C arm rotation mechanism 21. The X-ray tube 3 is configured to irradiate the subject M with X-rays. 1 represents the body axis direction of the subject M, and S represents the body side direction of the subject M. The X-ray tube 3 corresponds to the radiation source of the present invention, and the FPD 4 corresponds to the detection means of the present invention. The C arm 7 corresponds to the arm of the present invention. The C arm rotation mechanism 21 corresponds to the arm drive means of the present invention, and the C arm rotation control unit 22 corresponds to the arm drive control means of the present invention.

  The C arm 7 can also be rotated by a C arm rotation mechanism 21. That is, as shown in FIG. 2, the C-arm 7 is a plane to which the virtual circle VA along which the curve of the C-arm 7 is semicircular (see FIG. 2). The top can be rotated along a virtual circle VA. That is, the C arm 7 is on a plane to which the C arm 7 belongs when the X-ray tube 3 is vertically lower and the FPD 4 is vertically upper, and an axis that passes through the coupling portion between the C arm 7 and the column 8. An axis extending in the vertical horizontal direction (an axis extending in the body axis direction A passing through the center point of the curve of the C arm 7) can be rotated as a central axis. The C arm rotation mechanism 21 rotates the X-ray tube 3 and the FPD 4 by driving the C arm 7. A point where the central axis and the virtual circle VA at this time intersect will be referred to as a rotation center point c. The C arm rotation control unit 22 is configured to control the C arm rotation mechanism 21. The virtual circle VA is assumed to be located on a plane that bisects the C-arm 7.

  The top plate drive mechanism 23 is a mechanism for moving the top plate 2 in the body axis direction A as shown in FIG. The top plate drive mechanism 23 drives the top plate 2 according to the control of the top plate drive control unit 24 shown in FIG. The top board drive control unit 24 controls the top board drive mechanism 23 by inputting a top board movement signal indicating the movement direction and the movement amount of the top board 2 to the top board drive mechanism 23. If the surgeon wants to move the top plate 2, if the operator informs that through the operation console 31, the top plate drive control unit 24 moves the top plate according to the movement direction (forward direction or reverse direction) and the movement distance as input by the operator. The top plate driving mechanism 23 is controlled so as to drive the plate 2. The top plate drive mechanism 23 corresponds to the top plate drive unit of the present invention, and the top plate drive control unit 24 corresponds to the top plate drive control unit of the present invention.

  The bed to which the top plate 2 is attached is provided with a potentiometer 25 that detects the amount of movement of the top plate 2. When the top plate driving mechanism 23 moves the top plate 2, the potentiometer 25 detects the movement of the top plate 2. When the movement of the top plate 2 stops, the potentiometer 25 outputs a movement amount indicating the movement distance and movement direction of the top plate 2 accompanying the series of movements of the top plate 2. That is, when the potentiometer 25 moves the top plate 2 in the positive direction in the body axis direction A, the potentiometer 25 outputs a movement amount representing the movement distance as data. When the top plate 2 is moved in the opposite direction to the body axis direction A from this state, a negative movement amount representing the movement distance is output as data. The potentiometer 25 corresponds to the sensor of the present invention and can also be realized by an encoder.

  The X-ray tube control unit 6 is provided for the purpose of controlling the X-ray tube 3 with a predetermined tube current, tube voltage, and pulse width. When X-rays are emitted from the X-ray tube 3 under the control of the X-ray tube control unit 6, the X-rays pass through the subject M and enter the detection surface of the FPD 4. The FPD 4 detects the incident X-ray and generates a detection signal. This detection signal is sent to the image generation unit 11 (see FIG. 1), where an X-ray image P1 in which the subject M and the phantom ph are reflected is generated. This X-ray image P1 is a rectangle having the same shape as the detection surface for detecting the X-rays of the FPD 4, and is a mapping of the X-ray intensity detected on the detection surface.

  The stereoscopic image generating unit 12 reconstructs a series of X-ray images P1 continuously shot while rotating the C-arm 7 to generate a stereoscopic image D1 representing the internal structure of the subject M as voxel data. The three-dimensional image D1 is generated based on a series of X-ray images continuously taken while rotating the X-ray tube 3 and the FPD 4 with respect to the subject M in which a contrast medium is poured into the blood vessel. This is three-dimensional volume data in which a blood vessel image of the specimen M is three-dimensionally reflected. The stereoscopic image generation unit 12 corresponds to the stereoscopic image generation means of the present invention.

  The stereoscopic image editing unit 13 performs editing by adding an edit that moves the subject image reflected in the stereoscopic image D1 generated by the stereoscopic image generating unit 12 according to the output of the potentiometer 25, vector data, and the correction coefficient k on the data. A stereoscopic image D2 is generated. Assuming that the edited stereoscopic image D2 and the unedited stereoscopic image D1 are superimposed, the position of the blood vessel image of the subject M reflected in each stereoscopic image is shifted, and the respective blood vessel images do not completely overlap. The stereoscopic image editing unit 13 corresponds to editing means of the present invention.

  The projection image generation unit 14 projects the stereoscopic image D1 generated by the stereoscopic image generation unit 12 or the edited stereoscopic image D2 generated by the stereoscopic image editing unit 13 on a certain plane to generate the projection image Pr1 or the projection image Pr2. FIG. 4 illustrates a state in which the projection image generation unit 14 generates the projection image Pr1. The projection image generation unit 14 determines a projection direction for the stereoscopic image D1, and projects the stereoscopic image D1 onto a plane orthogonal to the projection direction to generate a projection image Pr1 that is a two-dimensional image. In the projection image Pr1 of the subject M, the distribution of blood vessels in the subject M is reflected. Specifically, the projection image generation unit 14 generates a projection image Pr1 obtained by projecting the stereoscopic image D1 onto the two-dimensional plane from the shooting direction of the moving image V0 determined by the inclination angle of the C arm 7. The projection image generation unit 14 corresponds to the projection image generation unit of the present invention. The projection image generation unit 14 corresponds to the projection image generation unit of the present invention.

  A description will be given of how the projection image generation unit 14 determines the projection direction. The projection image generation unit 14 is configured to generate the projection image Pr1 while performing X-ray imaging with a moving image. This moving image shooting is different from the shooting related to the generation of the stereoscopic image D1 described above, and is performed by emitting X-rays from a certain direction, passing through the subject M, and entering the FPD 4. is there. The direction in which X-rays are emitted at this time can be changed as appropriate by rotating the C-arm 7. The projection image generation unit 14 recognizes the X-ray irradiation direction based on the rotation angle of the C-arm 7 and generates the projection image Pr1 using this irradiation direction as the projection direction when generating the projection image.

  The X-ray irradiation direction is uniquely determined by the rotation angle of the C arm 7 output from the C arm rotation control unit 22. Therefore, the projection image generation unit 14 obtains the data regarding the rotation angle from the C-arm rotation control unit 22 when generating the projection image Pr1, determines the projection direction based on this, and projects the edited stereoscopic image D2. To do. The X-ray irradiation direction may be recognized by a potentiometer attached to the C arm. In this case, the projection image generation unit 14 operates by determining the projection direction based on the output of the potentiometer. It should be noted that this potentiometer is different from the potentiometer 25 according to the top plate 2 described above.

  The moving image generation unit 16 connects the X-ray images Ps generated one after another during X-ray imaging for moving image generation to generate a moving image V0. This moving image V0 is generated by connecting a series of X-ray images Ps obtained by continuously shooting the subject M in the order of imaging, and includes a two-dimensional image when the subject M is projected from a certain direction. The blood vessels are not clearly captured. The moving image generating unit 16 corresponds to the moving image generating means of the present invention.

  The image composition unit 17 superimposes the moving image V0 sent from the moving image generation unit 16 and the projection image Pr1 sent from the projection image generation unit 14 to generate a superimposed moving image V1. The superimposed moving image V1 is a moving image in which the projected image Pr1 is superimposed and displayed on the moving image V0, and the blood vessel image on the moving image V0 is emphasized.

  The main control unit 34 (see FIG. 1) is provided for the purpose of comprehensively controlling each control unit. The main control unit 34 is constituted by a CPU, and by executing various programs, the X-ray tube control unit 6 and the units 11, 12, 13, 14, 16, 17, 18, 19, 22, 24, and 26 are controlled. Realized. Further, each of the above-described units may be divided and executed by an arithmetic device that takes charge of them. The storage unit 28 (see FIG. 1) stores all parameters relating to control of the X-ray imaging apparatus 1 such as parameters used for imaging. The display unit 32 is provided for the purpose of displaying the superimposed video V1 and the like. The display unit 32 is configured to display the moving image V0 with the projection image Pr2 superimposed thereon, and corresponds to the display unit of the present invention. The display unit 32 corresponds to display means of the present invention.

<Moving the top plate during video recording>
The surgeon may want to fine-tune the moving image shooting field of view while shooting the superimposed moving image V1. Such fine adjustment is necessary, for example, when it is desired to bring the tip of the catheter reflected at the end of the superimposed moving image V1 to the center. When the operator inputs an instruction to move the top board 2 through the console 31 in order to change the field of view for photographing, the top board 2 is moved as instructed by the operator. Then, since the subject M moves with respect to the X-ray tube 3 and the FPD 4, the live image of the subject M reflected in the superimposed moving image V1 also moves.

  Then, what will the projected image Pr1 on the superimposed video V1 look like when the top 2 is moved? According to the conventional configuration, the projected image Pr1 is not updated when the moving image shooting starts, and thus does not move on the superimposed moving image V1. Therefore, according to the conventional configuration, when the operation of moving the top 2 during moving image shooting is performed, the live image of the subject M in the superimposed moving image V1 moves, but the projection image Pr1 is left behind, The image of will shift. Such image displacement hinders the knowledge of the position of the blood vessel of the subject M in the live image of the subject M.

  Therefore, according to the present invention, when the top plate 2 is moved, the projection image Pr1 is updated. By adopting such a configuration, even if the top 2 is moved, the projected image on the superimposed moving image V1 moves so as to follow the live image of the subject M, and the surgeon can operate the blood vessel in the live image. You can know the position of.

  In order to realize a configuration in which the projection image Pr1 is updated in accordance with the movement of the top plate 2, a mechanism for re-projecting the three-dimensional image to reflect the movement direction and movement distance of the top plate 2 and generating the projection image Pr1. Necessary. The movement distance of the top plate 2 is known by a potentiometer 25 that is a sensor attached to the bed constituting the top plate 2. The moving direction of the top plate 2 is a fixed direction determined when the bed having the top plate 2 is attached to the examination room. Therefore, if the projection image Pr1 is regenerated according to the movement distance of the top plate 2 detected by the potentiometer 25 and the predetermined movement direction of the top plate 2, the superimposed moving image V1 corresponding to the movement of the top plate 2 can be displayed. Should be.

  The alignment of the projection image Pr1 and the moving image V0 caused by the movement of the top 2 is performed at the stage of the stereoscopic image D1 before the projection image Pr1 is generated. The configuration for specifically performing the alignment is the stereoscopic image editing unit 13, and the stereoscopic image editing unit 13 is subject M according to the movement amount (corrected movement amount described later) output from the potentiometer 25. Thus, the image on the data is made to follow the image on the moving image that moves with the top board 2 by adding an edit for moving the three-dimensional image or the projected image on the data. The stereoscopic image editing unit 13 is configured to transmit data relating to the moving distance of the top plate 2 from a potentiometer 25 provided on the top plate 2. The stereoscopic image editing unit 13 monitors whether or not data relating to the movement of the top board 2 has been sent from the time point when the photographing relating to the stereoscopic image D1 is completed. When data relating to the movement distance is sent from the potentiometer 25, the stereoscopic image editing unit 13 basically generates the edited stereoscopic image D2 by moving the stereoscopic image D1 in a predetermined direction on the data according to the movement distance. . The edited stereoscopic image D2 is sent to the projection image generation unit 14 and converted into the projection image Pr2. Thus, the projection image Pr2 should also move following the movement of the subject M on the superimposed moving image V1 accompanying the movement of the top board 2.

  The top plate 2 does not actually move as ideal. That is, there is a slight difference between the actual movement of the top plate 2 and the movement of the top plate 2 detected by the potentiometer 25. Such a difference is caused by two factors, which will be described.

<Factors related to travel distance>
The potentiometer 25 is a sensor, and an error occurs in detection. Even if the potentiometer 25 detects the movement of the 10 cm top plate 2, it actually moves 9.95 cm. The movement process of the stereoscopic image D1 performed by the stereoscopic image editing unit 13 is performed based on the output of the potentiometer 25. Therefore, in the previous example, the stereoscopic image editing unit 13 moves the stereoscopic image D1 by an extra amount of 0.05 cm. In order to display the superimposed moving image V1 that accurately indicates the position of the blood vessel, this detection error must also be taken into consideration.

<Factors related to moving direction>
The stereoscopic image D1 is an image on a data space in which the body axis direction A is the x axis, the body side direction B is the y axis, and the vertical direction is the z axis. For example, it is assumed that the subject M is moved by a certain width in the body axis direction A by moving the top 2. In order to make the stereoscopic image D1 follow the movement of the subject M, it is only necessary to move the stereoscopic image D1 in the x-axis direction corresponding to the body axis direction A in the data space.

  However, the actual movement direction of the couchtop 2 due to an error when installing the couch provided with the couchtop 2 in the examination room and the situation that the couchtop drive mechanism 23 does not move the couchtop 2 in the ideal direction. Is slightly off from the ideal direction. In spite of such circumstances, the x-axis associated with the stereoscopic image D1 indicates the ideal direction of movement of the top 2. That is, if the subject M moves in the body axis direction A, in order to make the stereoscopic image D1 follow the movement of the subject M, the stereoscopic image D1 is moved in a slightly different direction from the x axis in the data space. Must be moved. In order to display the superimposed moving image V1 that accurately indicates the position of the blood vessel, it is necessary to accurately know the moving direction of the top 2.

  Such an image shift caused by the fact that the top plate 2 does not move as expected due to a factor related to the moving distance and a factor related to the moving direction is eliminated by photographing the phantom. By photographing the phantom, both the image shift due to the factor related to the moving direction and the image shift due to the factor related to the moving distance are suppressed. That is, the three-dimensional image editing unit 13 operates using the result of photographing the three-dimensional image of the phantom ph.

  FIG. 5 shows a phantom used to prevent image misalignment. The phantom ph has a cubic shape with a side of about 5 cm, and has a plurality of iron balls (not shown). In order to prevent the image shift caused by the top board 2, a three-dimensional image of the phantom ph is photographed as shown in FIG. X-ray images are continuously shot while rotating the C-arm 7 with respect to the phantom ph placed on the top board 2, and the phantom stereoscopic image Dph is photographed by assembling the continuous X-ray images into a stereoscopic image. Is done. The center of the phantom stereoscopic image Dph will be referred to as the phantom stereoscopic image center Dphc.

  Such a phantom stereoscopic image Dph is photographed twice. The two shootings are performed by placing the phantom ph in the field of view in the stereoscopic image shooting on the top 2. However, as shown in FIG. 7, the first shooting is performed with the phantom ph arranged on one end side of the visual field range, and the second shooting is performed with the phantom ph arranged on the other end side of the visual field range. . The movement of the phantom ph at this time is performed by the movement of the top board 2 through the top board drive mechanism 23. Therefore, by analyzing the positional relationship between the phantom stereoscopic images Dph1 and Dph2 obtained by the two shootings, it is possible to know how much and in which direction the top 2 has moved. As can be understood from this description, the size of the phantom ph is such that the phantom ph can move within the visual field range with the entire region positioned in the visual field range. In addition, it is assumed that the potentiometer 25 detects the movement of the 10 cm top plate 2 during one photographing.

  FIG. 8 illustrates the obtained phantom stereoscopic images Dph1 and Dph2 superimposed on one data space. The phantom stereoscopic images Dph1 and Dph2 are shifted by voxels corresponding to 9.95 cm. The reason why the top plate 2 should have moved 10 cm is that the actual top plate 2 did not move by the ideal distance assumed by the top plate drive control unit 24. The movement distances of the phantom stereoscopic images Dph1 and Dph2 are determined by the distance correction coefficient calculation unit 18 comparing the positions of the stereoscopic image centers Dphc1 and Dphc2 on the data.

  Further, the phantom stereoscopic images Dph1 and Dph2 are not shifted along the x axis indicating the body axis direction A on the data. This is because the actual top plate 2 did not move in the ideal direction. This is because the top plate 2 should move along the body axis direction A because the actual top plate 2 did not move in the ideal direction. The moving direction of the phantom stereoscopic images Dph1 and Dph2 is performed by the vector calculation unit 19 comparing the positions of the stereoscopic image centers Dphc1 and Dphc2 on the data. The moving direction of the phantom stereoscopic images Dph1, Dph2 is F. The vector data indicating the direction F is data indicating the moving direction of the top 2 calculated by the vector data calculation unit 19.

  Further, the distance correction coefficient calculation unit 18 acquires a coefficient related to the moving distance of the top 2. Data relating to the amount of movement of the top 2 is sent from the potentiometer 25 to the distance correction coefficient calculator 18. In the above example, the potentiometer 25 notifies the distance correction coefficient calculation unit 18 that the moving distance of the top 2 is 10 cm. Separately from this, the distance correction coefficient calculation unit 18 knows that the actual top 2 has moved 9.95 cm from image analysis of the phantom stereoscopic images Dph1 and Dph2. Therefore, the distance correction coefficient calculation unit 18 calculates a coefficient for converting the movement distance output by the potentiometer 25 into the actual movement distance based on the movement distance output by the potentiometer 25 and the movement distance obtained by image analysis. . This coefficient means that the actual moving distance can be calculated by multiplying the moving distance output by the potentiometer 25. In the above example, it is 9.95 / 10, that is, 0.995. This coefficient is called a correction coefficient k. This correction coefficient k is obtained from the photographing result obtained by photographing the phantom ph a plurality of times while changing the position of the top 2.

  The coefficient calculated by the distance correction coefficient calculation unit 18 is output to the distance correction unit 26. When there is an output of data related to the amount of movement of the top 2 from the potentiometer 25 in the future, the distance correction unit 26 corrects the data and sends it to the stereoscopic image editing unit 13. That is, if the potentiometer 25 outputs distance data “the top 2 has moved by a” during the moving image shooting of the subject M, the distance correction unit 26 corrects “the top 2 has moved by ak”. The completed distance data is sent to the stereoscopic image editing unit 13. This value ak is obtained by correcting the error of the moving amount by the distance correcting unit 26 based on a coefficient for converting the moving distance detected by the potentiometer 25 obtained from the photographing result of the phantom ph into the actual moving distance of the top board 2. It is. The distance correction unit 26 corresponds to the correction unit of the present invention.

  Further, vector data indicating the actual moving direction of the top 2 is sent from the vector data calculation unit 19 to the stereoscopic image editing unit 13. Therefore, the stereoscopic image editing unit 13 generates the edited stereoscopic image D2 by moving the stereoscopic image in which the subject M is reflected on the data by “ak” in the “F direction” as the vector data calculation unit 19 outputs. . As described above, the stereoscopic image editing unit 13 moves the image based on the vector data indicating the actual moving direction of the top board 2 obtained from the imaging result of the phantom ph.

<Operation of X-ray imaging apparatus>
Next, the operation of the X-ray imaging apparatus 1 according to the first embodiment will be described with reference to FIG. Live image capturing using the X-ray imaging apparatus 1 according to the present invention is performed as follows. The operations described below are assumed to be a surgical operation in which a catheter is inserted into the blood vessel of the subject M. The preparation stage related to phantom imaging and the book related to subject imaging Divided into shooting stages. Preparation is necessary to align the real space and the data space. Therefore, once the pre-preparation is performed, the main photographing can be performed many times by using the result obtained in the pre-preparation as long as there is no change in the movement pattern of the top 2. The preparation is not necessarily performed every time the subject is photographed.

  In the correction coefficient / vector calculation step S1 corresponding to the preparation, the above-described correction coefficient and vector data are calculated. That is, after the stereoscopic image of the phantom ph placed on the top board 2 is taken, the top board 2 is moved, and the stereoscopic image of the phantom ph is taken again. Accordingly, the distance correction coefficient calculation unit 18 calculates the correction coefficient k, and the vector data calculation unit 19 calculates vector data indicating the F direction.

  Then, the main imaging for the subject M is finally started. To perform the main imaging, first, the subject M is placed on the top 2 (subject placement step S2). The placed subject M is first injected with an angiographic contrast agent. Then, the X-ray image P1 is continuously shot while rotating the C arm 7 (see FIG. 2) (subject rotation imaging step S3). The obtained X-ray image P1 is assembled into a three-dimensional image D1 showing a three-dimensional distribution of blood vessels. Then, the projection image generation unit 14 recognizes the X-ray irradiation direction related to the moving image shooting based on the data indicating the rotation angle of the C arm 7 included in the C arm rotation control unit 22, and in this direction, the projection The image D1 is projected to generate a projection image Pr1. FIG. 10 shows how the projection image Pr1 is generated.

  When the generation of the projection image Pr1 is completed, a catheter is inserted into the subject M, and a surgical operation is started. Note that the rotation angle of the C-arm 7 during the surgical operation is the same as the rotation angle referred to when the projection image generation unit 14 operates. When the surgeon instructs the start of live image shooting through the console 31, the X-ray beam with a reduced dose is irradiated 15 to 30 times per second, and shooting of the moving image V0 is started (moving image shooting start step S4). ). FIG. 11 shows the situation at this time.

  The projection image Pr1 is sent to the image composition unit 17, and is superimposed on the moving image V0 and displayed on the display unit 32. In this way, display of the superimposed moving image V1 in which the projection image Pr1 is superimposed on the moving image V0 is started (superimposed moving image display start step S5). FIG. 12 shows the superimposed moving image V1 displayed at this time. The moving image shooting is performed using the position of the stereoscopic image shooting range in the subject rotation shooting step S3 as a visual field. This stereoscopic image shooting range is indicated by hatching in FIG. Therefore, the moving image V0 and the projected image Pr1 in the superimposed moving image V1 overlap without being deviated.

  Here, it is assumed that the operator instructs the X-ray imaging apparatus 1 to move the top 2 through the console 31 so that the catheter operation can be easily performed. The top plate 2 moves in the body axis direction A with respect to the C arm 7 in accordance with the operator's instructions (top plate moving step S6). However, due to the problem of mechanical accuracy, the actual trajectory of the movement of the top plate 2 is in the direction indicated by the vector data and is slightly deviated from the body axis direction A. FIG. 13 shows how the top plate 2 moves. The upper side of FIG. 13 shows a state before the top plate 2 is moved, and the lower side shows a state after the top plate 2 is moved. The relative position between the stereoscopic image capturing range indicated by the oblique lines and the subject M changes as the top 2 moves. The left side of FIG. 14 represents a moving image V0 obtained after the top plate 2 has been moved. As can be seen from comparison with the moving image V0 before the top plate 2 is moved as shown on the right side of FIG. 11, the field of view for moving image shooting is moved so as to scroll as the top plate 2 moves. When the above projected image Pr1 is superimposed on such a moving image V0, the images are displaced as shown on the right side of FIG.

  When the distance correction unit 26 recognizes the movement of the top 2 through the potentiometer 25, the distance correction unit 26 performs a correction process on the output of the potentiometer 25 based on the correction coefficient k calculated by the distance correction coefficient calculation unit 18. Data indicating the amount of movement of the plate 2 is sent to the stereoscopic image editing unit 13. The stereoscopic image editing unit 13 generates the edited stereoscopic image D2 by moving the stereoscopic image D1 on the data space by the corrected movement amount in the moving direction of the actual top plate 2 indicated by the vector data as shown in FIG. (3D image editing step S7). The edited stereoscopic image D2 is sent to the projection image generation unit 14 and converted into the projection image Pr2. The projection image Pr2 is superimposed on the moving image V0 by the image composition unit 17 and converted into a superimposed moving image V1. FIG. 16 shows the superimposed video V1 generated in this way. Since the projected image Pr2 is obtained by projecting the edited stereoscopic image D2 that has moved following the movement of the subject M, the moving image V0 and the projected image Pr2 are superimposed without deviation. The moving image V0 is displayed on the display unit 32, and the operation ends.

  As described above, it is possible to provide a radiation imaging apparatus that can accurately superimpose a live image on a blood vessel image even when the top 2 moves. That is, according to the present invention, it is possible to grasp how the top 2 has moved based on the output of the potentiometer 25, and to edit the stereoscopic image of the subject M to edit the stereoscopic image or the projected image on the data. Part 13 is provided. As a result, the projected image can be moved following the moving image that naturally moves as the top plate 2 moves. However, if only the potentiometer 25 is used to grasp the movement of the top 2, a deviation occurs when the moving image and the projected image are superimposed. Therefore, in the present invention, the movement of the top 2 is measured by changing the position of the top 2 and photographing the phantom a plurality of times. If such actually measured data is taken into account, even if there is an error in the potentiometer 25 or a deviation in the direction of movement of the top 2, the moving image and the projected image can be superimposed without deviation.

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

  (1) In the above-described first embodiment, the stereoscopic image D1 is edited. However, the present invention is not limited to this configuration. A configuration may be adopted in which the projection image Pr1, which is a two-dimensional image generated by the projection image generation unit 14, is edited to move in the data space. In this case, the vector data indicating the direction F that is a three-dimensional vector is projected by the projection image generation unit 14 and converted into two-dimensional vector data on a plane. The projection direction at this time is the same as the projection direction when the three-dimensional image D1 is projected to generate the projection image Pr1.

  The correction coefficient k is also converted so as to correspond to the two-dimensional vector data. That is, when a three-dimensional vector is projected onto a plane to obtain a two-dimensional vector, the length of the original vector is projected and the length of the projected vector is calculated. Find the ratio divided by the base vector length. Then, a new correction coefficient k is obtained by multiplying the correction coefficient k by this ratio.

  Such optimization of the vector data and the correction coefficient k is performed by the distance correction coefficient calculation unit 18 and the vector data calculation unit 19 that have received the data related to the projection direction from the projection image generation unit 14. Editing for moving the projection image Pr1 in the data space is performed by a projection image editing unit (projection image editing unit) (not shown) that receives the correction coefficient k and the vector data from the distance correction coefficient calculation unit 18 and the vector data calculation unit 19. Will do. This projection image editing means generates an edited projection image Pr3 by moving the projection image Pr1 on the data space so as to follow the scroll movement of the image on the moving image V0 accompanying the movement of the top board 2, and this edited projection image Pr3 is superimposed on the moving image V0, and the superimposed moving image V1 is generated.

  (2) In the first embodiment described above, the output of the potentiometer 25 is corrected. However, the present invention is not limited to this configuration. The distance correction unit 26 may acquire data indicating an ideal movement distance of the top plate 2 from the top plate drive control unit 24 and correct the data. The correction coefficient k in this case is a coefficient for converting the movement distance output by the top board drive control unit 24 into an actual movement distance.

(3) In Embodiment 1 described above, the phantom was shot twice, but the number of times of shooting may be three or more. That is, in the above-described configuration, the top 2 is moved in the body axis direction A of the subject M and the phantom ph is imaged twice. However, the top 2 is moved in the body-side direction S of the subject M and the phantom is captured. The ph may be taken twice more. Alternatively, the top plate 2 may be moved up and down to photograph the phantom ph twice. According to this configuration, it is possible to correct a displacement in the top plate 2 other than the body axis direction A.
In such a configuration, the correction can be performed independently for each moving direction, so that each moving direction of the top plate can be changed as in the case where the top plate is tilted with respect to the moving direction. The present invention is applicable even if the body axis direction A, the body side direction S, and the vertical direction are not orthogonal to each other.

2 Top plate 3 X-ray tube (radiation source)
4 FPD (detection means)
7 C-arm (arm)
12 stereoscopic image generating unit (stereoscopic image generating means)
13 stereoscopic image editing part (editing means)
14 Projection image generation unit (projection image generation means)
16 Video generation unit (video generation means)
21 C arm rotation mechanism (arm drive means)
22 C-arm rotation control unit (arm drive control means)
23 Top plate drive mechanism (top plate drive means)
24 Top plate drive control unit (top plate drive control means)
25 Potentiometer (sensor)
26 Distance correction unit (correction means)
32 Display section (display means)

Claims (6)

A top plate on which the subject is placed;
A top plate driving means for moving the top plate;
A top plate drive control means for controlling the top plate drive means;
A sensor for detecting the amount of movement of the top plate;
A radiation source for irradiating the subject with radiation;
Detection means for detecting radiation transmitted through the subject;
An arm supporting the radiation source and the detection means;
Arm driving means for rotating the radiation source and the detecting means by driving the arm;
Arm drive control means for controlling the arm drive means;
A moving image generating means for generating a moving image by connecting a series of radiation images obtained by continuously shooting a subject in the order of photographing;
Stereoscopic image generating means for generating a stereoscopic image of the subject based on a series of radiographic images continuously taken while rotating the radiation source and the detection means with respect to the subject;
A projected image generating means for generating a projected image obtained by projecting the stereoscopic image onto a two-dimensional plane from the moving image capturing direction;
Correction means for correcting an error in the amount of movement of the output of the sensor based on the imaging result obtained by imaging the phantom multiple times while changing the position of the top plate;
Editing means for adding an edit to move a stereoscopic image or a projected image of the subject on the data by a movement amount corrected in the movement direction of the top plate obtained by photographing the phantom;
A radiation imaging apparatus comprising: display means for displaying the projected image superimposed on the moving image. The radiographic apparatus according to claim 1,
The radiographic apparatus characterized in that the imaging result used by the editing means for operation is a stereoscopic image of the phantom. The radiographic apparatus according to claim 1 or 2,
The correction means corrects an error in the amount of movement based on a coefficient for converting the movement distance detected by the sensor obtained from the imaging result of the phantom into the actual movement distance of the top board. apparatus. The radiographic apparatus according to any one of claims 1 to 3,
The radiation imaging apparatus according to claim 1, wherein an actual moving direction of the top board obtained by imaging results of the phantom used when the editing unit operates is expressed as vector data. The radiation imaging apparatus according to any one of claims 1 to 4,
A radiation imaging apparatus, wherein a blood vessel distribution in a subject is reflected in the stereoscopic image and the projection image of the subject. The radiographic apparatus according to any one of claims 1 to 5,
A radiographic apparatus characterized by being for catheter insertion operation.

Images