WO2018116870A1

WO2018116870A1 - Radiography device, radiography system, radiography method, and program

Info

Publication number: WO2018116870A1
Application number: PCT/JP2017/044182
Authority: WO
Inventors: 辻井　修; 中野　浩太; 亮藤本; 哲雄島田
Original assignee: キヤノン株式会社
Priority date: 2016-12-19
Filing date: 2017-12-08
Publication date: 2018-06-28
Also published as: JP2018099175A

Abstract

This radiography device is provided with: a rotating means for rotating a radiation generation means for generating radiation and/or a radiation detection means for detecting the radiation; a fixing means for rotatably holding the rotating means; and a distance sensor for acquiring information on the distance between the rotating means and the fixing means in the radial direction and thrust direction with respect to the direction of rotation of the rotating means.

Description

Radiation imaging apparatus, radiation imaging system, radiation imaging method, and program

The present invention relates to a radiation imaging apparatus, a radiation imaging system, a radiation imaging method, and a program.

For example, a mammogram device is standardly used as a radiation imaging device for breast cancer. However, it is known that in the case of dense breasts (breasts with many mammary glands), the mammogram device has reduced lesion detection sensitivity and specificity because the lesion and the mammary gland structure overlap. Tomosynthesis and breast-only CT are attracting attention as techniques to compensate for the disadvantages of this mammogram device. A feature of these devices is that they provide a 3D image of the breast so that the lesion and mammary gland structure can be separated and observed.

The following techniques are disclosed in breast dedicated CT. Japanese Patent Application Laid-Open No. 2004-151820 discloses that even if the actual rotation center of the X-ray fan beam deviates from the ideal rotation center, the amount of deviation is corrected by the correcting means. Japanese Patent Application Laid-Open No. 2004-228688 discloses that a shift of the rotation center and distortion of a projection image are corrected to obtain a difference image, a contrast of a projection image and a reconstructed image, and a high-resolution image.

In addition, a technique is disclosed in which an alignment phantom is placed in an imaging region and scanning is performed to obtain an X-ray ray formula for each projection image (Non-Patent Document 1).

JP-A-4-325144 JP 2002-291726 A

The radiation imaging apparatus may require a high resolution image. For example, in breast-only CT, it is necessary to depict microcalcifications because of the need to replace mammograms in screening. Therefore, a special mechanism is required to suppress the displacement of the mechanism unit in the radiation imaging apparatus.

It is an object of the present invention to correct a shift caused by a mechanism unit in a radiation imaging apparatus based on distance information resulting from rotation of the mechanism unit in the radiation imaging apparatus without requiring a special mechanism.

The radiation imaging apparatus of the present invention includes a radiation generating means for generating radiation, a rotating means for rotating at least one of the radiation detecting means for detecting the radiation, a fixing means for rotatably holding the rotating means, and the rotation A distance sensor for acquiring distance information between the rotating means and the fixing means in a radial direction and a thrust direction with respect to a rotating direction of the means;

Based on the distance information resulting from the rotation of the mechanism unit in the radiation imaging apparatus, it is possible to correct the shift caused by the mechanism unit in the radiation imaging apparatus.

1 is an external view of a radiation imaging system according to a first embodiment of the present invention. It is a front view inside the imaging | photography part which concerns on the 1st Embodiment of this invention. It is a side view inside the imaging | photography part which concerns on the 1st Embodiment of this invention. It is a figure which shows an example of the distance sensor arrangement | positioning which concerns on the 1st Embodiment of this invention. It is a figure which shows an example of the timing of the signal which concerns on the 1st Embodiment of this invention. It is a flowchart which shows an example of the calibration flow which concerns on the 1st Embodiment of this invention. It is a flowchart which shows an example of the imaging | photography flow which concerns on the 1st Embodiment of this invention. It is a figure explaining calculation of a ray type concerning a 1st embodiment of the present invention. It is a figure which shows an example of the distance sensor arrangement | positioning which concerns on the 2nd Embodiment of this invention. It is a figure which shows the example by which a distance sensor is arrange | positioned on the outer side of a rotation frame.

(First embodiment)
FIG. 1 is an external view of the radiation imaging system according to the first embodiment. An imaging unit 6 that captures a radiographic image is held by a support unit 3. There is a rotating frame (not shown) in the imaging unit 6, and an imaging region is set at the center of the rotating frame. The rotating frame is covered with a cover part. The cover part includes a front cover 130 and a side cover 140. At the center of the front cover 130 is a hole 7 for inserting a breast.

The radiation generator and radiation detector are fixed to the rotating frame, and the projection data is photographed by rotating 360 degrees around the breast as the subject. There is an imaging region in the center of the rotating frame, and a breast holding unit (not shown) is arranged so as to fit in the imaging region.

FIG. 2 is a front view of the inside of the photographing unit of the first embodiment. The support column 3 holds the imaging unit 6. The imaging unit 6 includes a fixed frame (fixed unit) 10 and a rotating frame 11. The fixed frame (fixed portion) 10 holds the rotating frame 11 in a rotatable manner. Mounted on the rotating frame 11 are a radiation generation unit 12 that generates radiation and a radiation detection unit 13 that detects radiation.

A subject 15 is arranged in an imaging region in the radiation beam 14 formed by the radiation generator 12 and the radiation detector 13. The radiation beam 14 is rotated by the rotation of the rotating frame 11 that rotates the radiation generation unit 12 and the radiation detection unit 13, and projection data of the subject 15 in the 360-degree direction is captured. The control unit 16 stores the projection data in the data storage unit 17.

The control unit 16 controls the timing of reading projection data from the radiation detection unit 13 according to the rotation angle of the rotating frame 11. The control unit 16 acquires distance information from the distance sensor 18 at the same timing as recording or reading of projection data.

The control unit 16 controls the timing at which the distance sensor 18 acquires the distance information according to the rotation angle of the rotating frame 11. The distance sensor 18 acquires distance information between the rotating frame 11 and the fixed frame 10 in the radial direction and the thrust direction with respect to the rotating direction of the rotating frame 11. That is, the distance information is distance information between the fixed frame 10 and the rotating frame 11 in the radial direction and the thrust direction with respect to the rotating direction of the rotating frame 11. The distance information may be acquired by a plurality of distance sensors. In FIG. 2, three distance sensors 18 are mounted. As the distance sensor 18, a contact type or laser type sensor is used.

Projection data recording timing is determined by the radiation pulse exposure position. In breast dedicated CT, high resolution is required, so pulsed radiation is used. The exposure position is defined by the rise and fall of the radiation pulse. Recording is performed at the same timing as the projection data recording.

Distance information is measured and recorded at three timings: the rise of the radiation pulse, the fall of the radiation pulse, and the center of the rise and fall of the radiation pulse. The control unit 16 controls the timing at which the radiation generating unit 12 emits radiation according to the rotation angle of the rotating frame 11. In the control unit 16, the distance sensor 18 obtains distance information at at least one of the three timings of the rising edge, the falling edge, and the center of the rising edge and the falling edge of the radiation pulse (pulse signal) that defines the irradiation timing. Control the timing.

The timing for measuring and storing the distance information is controlled by transmitting from the control unit 16 a synchronization signal synchronized with the radiation pulse. Since the radiation pulse width (unit: msec) is determined before the start of imaging, for example, even when the timing at which distance information is measured and recorded is set at a time delayed by a half pulse width from the fall of the radiation pulse. Good. The timing for recording the distance information may be at least one of the three timings at the rise of the radiation pulse, the fall of the radiation pulse, and the center of the rise and fall of the radiation pulse.

In FIG. 2, the distance information in the radial direction and the thrust direction is acquired at three positions. By using the distance information of the three positions, it is possible to specify (calculate) the position of the rotating frame 11 with respect to the fixed frame 10 in the three-dimensional space.

FIG. 3A shows a side view of the inside of the photographing unit 6 of the first embodiment. An imaging system frame 19 is fixed to the rotating frame 11, and the radiation generation unit 12 and the radiation detection unit 13 are installed in the imaging system frame 19. The rotating frame 11 is rotatably attached to the fixed frame 10 via a bearing 20. A subject (breast) 15 is inserted from the hole 7 of the front cover 130 of FIG. The front cover 130 is attached to the fixed frame 10.

The subject 15 is structurally fixed to the fixed frame 10. In this state, when the rotating frame 11 rotates with respect to the fixed frame 10, the play due to the bearing 20 occurs. At the timing of the radiation pulse, the distance sensor 18 records a backlash generated between the fixed frame 10 and the rotating frame 11. In this case, the distance sensor 18 measures the distance between the fixed frame 10 and the rotating frame 11 in the radial direction and the thrust direction. By providing the plurality of distance sensors 18, the three-dimensional position of the rotating frame 11 can be specified. Here, the three-dimensional position is based on the position of the fixed frame 10.

The distance information is measured by the distance sensor 18 by the distance reading unit 21 and the distance measurement surface 22 shown in FIG. 3B. In the present embodiment, the distance reading unit 21 is installed on the rotating frame 11, and the distance measuring surface 22 is a surface on the fixed frame 10.

If the distance reading unit 21 is installed on the rotating frame 11, since both the control unit 16 and the distance reading unit 21 are on the rotating frame 11, a synchronization signal for controlling the timing for measuring and storing the distance information is rotated. It is transmitted by wire on the frame 11. Considering the transmission speed and accuracy of the synchronization signal and the simplicity and cost of the configuration, it is preferable to transmit the synchronization signal by wire rather than wirelessly.

On the other hand, if the distance reading unit 21 is installed on the fixed frame 10, the control unit 16 is on the rotating frame 11, and the distance reading unit 21 is on the fixed frame 10. It is necessary to transmit a synchronization signal via the frame 10. Specifically, it is necessary to transmit the synchronization signal via a slip ring or a cable bear (registered trademark). Although the slip ring has an advantage that it can be continuously rotated in one direction, an expensive slip ring is required for high-speed data communication.

Therefore, it is preferable that the control unit 16 and the distance reading unit 21 are both installed on the rotating frame 11 side. That is, the distance sensor 18 is installed on the rotating frame 11 side and rotates together with the rotating frame 11. For example, the rotating side surface of the rotating frame 11 rotates along the side surface of the fixed frame 10. The distance sensor 18 is installed on the rotating side surface and measures the distance to the side surface of the fixed frame 10 in the radial direction and the thrust direction.

As shown in FIG. 3C, the rotating frame 11 is rotated by the rotation-on signal. The timing of distance measurement is defined by the timing of radiation exposure by radiation pulses. The radiation exposure by the radiation pulse is performed for each rotation angle determined by the control unit 16.

In order to measure the rotation angle, a rotation angle reading unit (not shown) is arranged on the rotation frame 11 and faces a rotation angle measurement surface arranged circumferentially on the fixed frame 10. Each time the rotation angle reading unit reads the rotation angle measurement surface by the rotation of the rotation frame 11, an encoder signal is generated.

The control unit 16 determines the rotation angle at which the radiation is exposed based on the number of imaging angles (number of views) when the rotating frame 11 makes one rotation. The control unit 16 counts the encoder signal from the rotation angle reading unit, outputs a synchronization signal when the rotation angle reaches a predetermined rotation angle, and synchronizes with a predetermined timing of the radiation pulse with a predetermined pulse width and duty ratio. Expose radiation. When the number of views is 1000, the radiation pulse is output 1000 times and the radiation is exposed 1000 times. In response to the radiation exposure, the control unit 16 reads an image signal from the radiation detection unit 13.

The distance sensor 18 measures and records distance information in synchronization with a predetermined timing of the radiation pulse. The radiation pulse has a width of 10 msec to 20 msec. For example, when the pulse width is 10 msec, the distance sensor 18 measures and records the distance information at three timings: rising of the radiation pulse, 5 msec after the rising, and falling of the radiation pulse. The distance sensor 18 may measure and record the distance information at at least one of these three timings. In this case, distance information may be recorded at the center of the rise and fall of the radiation pulse.

FIG. 4 is a diagram showing a calibration flow of the present embodiment. In the calibration flow, a ray table in which the ray formula of radiation and distance information are associated (linked) is created at each imaging angle (projection angle). A command for performing calibration imaging of the alignment phantom and the number of views (calibration data) are input from a display input unit (not shown) (step S101).

The number of views (first view number) in calibration may not be the same as the number of views (second view number) in the shooting flow described later. The ray formula of the projection angle of the radiation irradiated in the imaging flow may be calculated by interpolating the data of the ray distance table created by calibration.

Alignment phantoms are installed in the imaging area of the imaging unit 6 (step S102). The alignment phantom may be the one described in Non-Patent Document 1. For example, an alignment phantom has a plurality of tungsten spheres arranged in acrylic.

The instruction to start capturing the radiation image of the alignment phantom is issued from the display input unit, and the rotating frame 11 rotates (step S103). The control unit 16 releases the interlock of the radiation generation unit 12, activates the radiation detection unit 13, resets the encoder, and starts rotating the rotating frame 11.

When the rotation of the rotating frame 11 (first rotation) starts, an encoder signal is generated. The control unit 16 counts up the encoder signal (step S104). Each time the count reaches the specified value q1, a radiation pulse is generated with a predetermined pulse width (step S105).

The distance information (first distance information) is measured and recorded in synchronization with a predetermined timing of the radiation pulse, and the distance information (first distance information) is acquired by the rotation (first rotation) of the rotating frame 11. (Step S106). In response to the radiation pulse, the control unit 16 acquires an image signal of the radiation image from the radiation detection unit 13 (step S107). The radiation image shows the shadow of the alignment phantom. By the rotation of the rotating frame 11 (first rotation), a radiation image (first radiation image) of the alignment phantom is acquired.

The counting up of the encoder signal, generation of radiation pulses, acquisition of distance information, and acquisition of radiation images are repeated the number of times corresponding to the rotation angle (projection angle).

Analyzing the radiation image, the ray formula of the radiation at each rotation angle (projection angle) is calculated (step S108). The control unit 16 calculates a radiation ray formula (first ray formula) in the radiation image (first radiation image) acquired by the first rotation of the rotating frame 11.

In the present embodiment, the method described in Non-Patent Document 1 is applied as the light ray calculation method, but other known calculation methods may be applied. In Non-Patent Document 1, nine parameters such as SID (Source Image Distance) and SOD (Source Object Distance) that define the ray of radiation are calculated, but are not limited thereto.

The ray formula (9 parameters in this embodiment) calculated in step S108 and the distance information measured in step S106 are associated with each rotation angle (projection angle) (step S109). The table associated in step S109 is referred to as a light ray distance table (light ray distance information). The control unit 16 acquires the first distance information and the first light beam expression by rotating the rotating frame 11 around the alignment phantom. The control unit 16 generates ray distance information that associates the first distance information acquired by the first rotation with the first ray type according to the rotation angle of the rotating frame 11.

The above processing ends normally, and calibration shooting ends (step S110).

FIG. 5 is a diagram showing a photographing flow for photographing a subject according to the present embodiment. In the imaging flow, imaging of the subject 15 at each projection angle is performed, and before reconstructing the radiation image, the ray formula of the radiation at each projection angle of the subject 15 is determined using the ray distance table. A radiation image of the subject 15 is reconstructed based on the determined ray formula. The control unit 16 corrects the shift of the rotating frame 11 with respect to the fixed frame 10 according to the distance information, and reconstructs a radiographic image of the subject 15.

A command for photographing the subject 15 and the number of views (subject data) are issued from a display input unit (not shown) (step S201). The number of views (second view number) in photographing the subject 15 may not be the same as the number of views (first view number) in calibration. The ray formula of the projection angle of the radiation irradiated by photographing the subject 15 may be calculated by interpolating the data of the ray distance table created by calibration.

The subject 15 is placed in the shooting area of the shooting unit 6 (step S202). An instruction to start capturing a radiographic image of the subject 15 is issued from the display input unit, and the rotating frame 11 rotates (step S203). The control unit 16 releases the interlock of the radiation generation unit 12, activates the radiation detection unit 13, resets the encoder, and starts rotating the rotating frame 11.

When the rotation of the rotating frame 11 (second rotation) starts, an encoder signal is generated. The control unit 16 counts up the encoder signal (step S204). Each time the count reaches the specified value q2, a radiation pulse is generated with a predetermined pulse width (step S205).

The distance information is measured and recorded in synchronization with the predetermined timing of the radiation pulse, and the distance information (second distance information) is acquired by the second rotation of the rotating frame 11 (step S206). In response to the radiation pulse, the control unit 16 acquires an image signal of the radiation image from the radiation detection unit 13 (step S207). A shadow of the subject (breast) 15 is reflected in the radiation image. A radiographic image (second radiographic image) of the subject 15 is acquired by the second rotation of the rotating frame 11.

By analyzing the distance information in radiographic image capturing of the subject 15, the radiation ray formula (in this embodiment, nine parameters) of each rotation angle (projection angle) is calculated (step S208). In the calculation of the light ray equation (second light ray equation) in step S208, the light ray distance table (light ray distance data) created in step S109 of the calibration flow is used.

The ray formula (in this embodiment, nine parameters) calculated in step S208 and the radiation image of the subject 15 acquired in step S207 are associated with each rotation angle (projection angle) (step S209).

Based on the ray formula calculated in step S208, the radiographic image of the subject 15 is forward projected or back projected to calculate a reconstructed image of the subject 15 (step S210). When the reconstructed image is completed, shooting is completed (step S211).

Next, with reference to FIG. 6, the calculation of the ray formula in step S208 will be described in detail according to the method described in Non-Patent Document 1. As shown in FIG. 6, the coordinate system of the reference (O, X, Y, Z) of the alignment phantom or subject 15 is represented by (X, Y, Z). Further, the coordinates of the reference (S, X ′, Y ′, Z ′) of the radiation focus (projection) are represented by (X ′, Y ′, Z ′), and the detection surface of the radiation detection unit 13 from the radiation focus S. The point where the perpendicular to the crossing with the detection surface of the radiation detector 13 is represented by S ′ (C, L). The length of the perpendicular line from the radiation focus S to the detection surface of the radiation detection unit 13 is represented by D.

Here, it is assumed that the rotating frame 11 rotates about the Z axis as a rotation axis. The ray formula is described by (Xs, Ys, Zs, Θ, φ, Ψ, Cs, Ls, D). Here, (Xs, Ys, Zs) is an offset of the radiation focus S with respect to the coordinate system O of the subject 15. (Θ, φ, Ψ) is the Euler angle between the coordinate system O of the subject 15 and the coordinate system of the radiation focus S. (Cs, Ls) is the position of the point where the perpendicular from the radiation focus S to the detection surface of the radiation detection unit 13 intersects the detection surface of the radiation detection unit 13. D is the length of a perpendicular line from the radiation focus S to the detection surface of the radiation detection unit 13.

In step S108 of the calibration flow, the first ray formula when the rotation angle (projection angle) is 0 degree is described as (Xs0, Ys0, Zs0, Θ0, φ0, Ψ0, Cs0, Ls0, D0). .

In step S106, when the projection angle is 0 degree, the measurement values (first distance information) in the radial direction and the thrust direction of the distance sensor 18 installed at the position of the rotation frame 11 at the rotation angle 0 degree are obtained. Let R0 (0) and TH0 (0). When the projection angle is 0 degree, the measured values (first distance information) in the radial direction and the thrust direction of the distance sensor 18 installed at the position of the rotation angle 90 of the rotating frame 11 are R0 (90). And TH0 (90). Here, the distance sensor 18 is installed at a position where the rotation angle of the rotating frame 11 is 0 degrees and 90 degrees.

In step S206 of the photographing flow, when the projection angle is 0 degree, the measurement values (second distance information) in the radial direction and the thrust direction of the distance sensor 18 installed at the position of the rotation angle of the rotation frame 11 are 0 degrees. Are R1 (0) and TH1 (0). When the projection angle is 0 degree, the measurement values (second distance information) in the radial direction and the thrust direction of the distance sensor 18 installed at the position of the rotation angle of the rotation frame 11 are 90 degrees. And TH1 (90).

In this case, in step S208 of the imaging flow, the control unit 16 uses the second ray formula (Xs1, Ys1, Zs1, Θ1, φ1, Ψ1, Cs1, Ls1, D1) when the rotation angle (projection angle) is 0 degrees. ) Is calculated by the equation (1).
Xs1 = Xs0 + α (R1 (0) −R0 (0))
Ys1 = Ys0 + β (R1 (90) −R0 (90))
Zs1 = Zs0 + γ (TH1 (0) −TH0 (0))
Θ1 = Θ0
Φ1 = Φ0
Ψ1 = Ψ0
Cs1 = Cs0
Ls1 = Ls0
D1 = D0 (1)

Here, α, β, and γ are constants of about 0.5 and correspond to the ratio between the circumference of the rotating frame 11 and the SID. As described above, the control unit 16 calculates the second light ray equation from the first light ray equation based on the difference between the first distance information and the second distance information.

Further, in the formula (1), it is assumed that the positional relationship between the radiation focus S and the radiation detection unit 13 does not change and the Euler angle between the coordinate system O and the coordinate system of the radiation focus S does not change. Further, the position of the point where the perpendicular line from the radiation focus S to the detection surface of the radiation detection unit 13 intersects the detection surface of the radiation detection unit 13 and the length of the perpendicular line from the radiation focus S to the detection surface of the radiation detection unit 13 do not change. It is assumed that. The movement of the rotating frame 11 with respect to the fixed frame 10 is reflected in the movement of the radiation focus S.

By calculating Expression (1) at each projection angle in the projection flow, the ray formula calculated at each rotation angle (projection angle) according to the number of views is associated with the radiation image of the subject 15 in Step S209. . In this case, the ray equation for each projection angle ζ may be calculated by equation (2).
Xs1 = Xs0 + α (R1 (0) −R0 (0)) · cos (ζ)
Ys1 = Ys0 + β (R1 (90) −R0 (90)) · cos (ζ)
Zs1 = Zs0 + γ (TH1 (0) −TH0 (0))
Θ1 = Θ0
Φ1 = Φ0
Ψ1 = Ψ0
Cs1 = Cs0
Ls1 = Ls0
D1 = D0 (2)

As described above, the control unit 16 calculates the second light equation from the first light equation based on the function of the rotation angle of the rotating frame 11, the first distance information, and the second distance information.

Based on the first distance information and the second distance information, the control unit 16 obtains the second radiation from the first light ray expression of the radiation in the first radiation image according to the expression (1) or the expression (2). A second ray formula in the image is calculated. The control unit 16 reconstructs a radiographic image of the subject 15 based on the light beam method (second light beam method).

Note that the control unit 16 may generate a radiation image for gain correction from the radiation image reconstructed based on the light beam method (second light beam method). In this case, in a state where the alignment phantom and the subject 15 are not arranged in the imaging region, the radiation generation unit 12 obtains distance information and a radiation image while irradiating the radiation, thereby gain based on the second ray formula. A correction radiation image is generated.

In the equations (1) and (2), the relationship between the movement of the rotating frame 11 caused by play such as a bearing for rotating the rotating frame 11 with respect to the fixed frame 10 and the ray type of radiation is corrected. Explained when to do.

However, the radiation beam misalignment of radiation is influenced by the distortion of the rotating frame 11 and the bending of the radiation generating unit 12 and the radiation detecting unit 13 fixed to the rotating frame 11 in addition to the backlash of the bearing and the like. In this case, since it may be difficult to formulate, by performing the calibration flow a plurality of times, a function of the rotation angle ζ and the distance information (the measured value Rn in the radial direction and the measured value THn in the thrust direction) For example, the ray formula is calculated using Formula (3).
Xs1 = Xsa + F1 (ζ, Rn, THn)
Ys1 = Ysa + F2 (ζ, Rn, THn)
Zs1 = Zsa + F3 (ζ, Rn, THn)
Θ1 = Θa + F4 (ζ, Rn, THn)
Φ1 = Φa + F5 (ζ, Rn, THn)
Ψ1 = Ψa + F6 (ζ, Rn, THn)
Cs1 = Csa + F7 (ζ, Rn, THn)
Ls1 = Lsa + F8 (ζ, Rn, THn)
D1 = Da + F9 (ζ, Rn, THn) (3)

Here, Xsa, Ysa, Zsa, Θa, Φa, Ψa, Csa, Lsa, Da represent an average ray equation (for example, an average value) obtained by a plurality of calibrations. F1 to F9 are functions derived from the rotation angle ζ, the radial measurement value Rn, and the thrust measurement value THn by a plurality of calibrations. The ray formula at each projection angle ζ when the subject 15 is photographed is calculated using the formula (3) from the radial measurement value Rn and the thrust measurement value THn.

As described above, the control unit 16 determines, based on the rotation angle of the rotating frame 11 and the function of the plurality of distance information, from the average of the radiation beam type in the plurality of radiation images acquired by the plurality of rotations of the rotating frame 11. The ray formula in the radiographic image of the subject 15 is calculated. The control unit 16 acquires a plurality of distance information and a radiation beam type by rotating the rotating frame 11 a plurality of times around the alignment phantom.

In order to reconstruct a highly accurate radiographic image, it is important to accurately grasp the positional relationship between the radiation generation unit 12 and the radiation detection unit 13. Therefore, the distance phantom data is generated by calibrating the alignment phantom, and the light ray formula is generated from the light distance data based on the distance information when the subject 15 is photographed. A high-accuracy radiographic image can be reconstructed by reconstructing the radiographic image of the subject 15 using the corrected ray formula.

(Second Embodiment)
FIG. 7 is a diagram illustrating an arrangement of distance sensors in the radiation imaging system according to the second embodiment. As shown in FIG. 7, four

distance sensors

181, 182, 183, and 184 are arranged on the rotating frame 11 at intervals of 90 degrees in the rotating direction of the rotating frame 11. Each distance sensor can measure and store distance information between the fixed frame 10 and the rotating frame 11 in the radial direction and the thrust direction with respect to the rotating direction of the rotating frame 11. By providing four distance sensors, the three-dimensional position of the rotating frame 11 can be specified with redundancy as compared with the case of providing two distance sensors.

R (0) and TH (0) are measured as the measured values in the radial direction and the thrust direction of the distance sensor 181 installed at the position where the rotation angle of the rotating frame 11 is 0 degree. R (90) and TH (90) are measured as measured values in the radial direction and the thrust direction of the distance sensor 182 installed at the position of the rotation angle of the rotation frame 11 at 90 degrees.

R (180) and TH (180) are measured as measured values in the radial direction and the thrust direction of the distance sensor 183 installed at the position of the rotation angle of the rotation frame 11 of 180 degrees. In addition, R (270) and TH (270) are measured as measured values in the radial direction and the thrust direction of the distance sensor 184 installed at the position of the rotation angle 270 degrees of the rotating frame 11.

In Expressions (1) to (3), the measured values in the radial direction are R (0), R (90), R (180), R (270), and the thrust direction in the light ray expression when photographing the subject 15. TH (0), TH (90), TH (180), and TH (270) may be considered.

In the first embodiment and the second embodiment, the distance reading unit 21 of the distance sensor 18 is arranged on the rotating frame 11 side, but the distance reading unit 21 of the distance sensor 18 is fixed outside the rotating frame 11. It may be arranged on the frame 10 side.

Since the radiation generator 12 and the radiation detector 13 are arranged on the rotating frame 11 side, it is preferable that the radiation exposure timing and the radiation image acquisition timing are generated on the rotating frame 11 side. Moreover, since it is preferable to acquire distance information according to the timing of radiation exposure, it is preferable that the distance reading unit 21 is also on the rotating frame 11 side.

However, there is a request to dispose the distance reading unit 21 outside the rotating frame 11 due to space restrictions. For example, as illustrated in FIG. 8, the distance reading unit 185 and the distance information storage unit 186 that stores the distance information measured by the distance reading unit 185 may be arranged on the fixed frame 10 side.

The rotating side surface of the rotating frame 11 rotates along the side surface of the fixed frame 10. The distance sensor 18 is installed on the fixed frame 10 and measures the distance to the rotating side surface in the radial direction and the thrust direction.

In this case, in order to control the timing at which the distance reading unit 185 measures distance information in accordance with the radiation exposure timing, a circuit on the rotating frame 11 side and a circuit on the outside of the rotating frame 11 (for example, the fixed frame 10 side). It is sufficient to match the times. For example, a time signal is output from the rotating frame 11 side (for example, the control unit 16) to the fixed frame 10 side (for example, the distance information storage unit 186), and the times of the rotating frame 11 and the fixed frame 10 are made coincident.

The control unit 16 matches the times of the control unit 16 and the distance sensor 18, controls the timing at which the radiation generation unit 12 emits radiation according to the time, and the distance sensor 18 determines the distance information according to the time. To get.

Further, as shown in FIG. 1, the hole 7 is provided in the front cover 130, but there is no cover on the opposite side 150 of the front cover 130, and the photographer can turn the rotating frame from the opposite side 150 of the front cover 130. 11 central imaging areas can be easily accessed.

The present invention supplies software (programs) for realizing the functions of the above-described embodiments to a system or apparatus via a network or various storage media, and a computer (CPU, MPU, etc.) of the system or apparatus reads the program. May be executed. The present invention can also be realized by a process in which one or more processors in a computer of a system or apparatus read and execute a program, and can also be realized by a circuit (for example, an ASIC) that realizes one or more functions.

The present invention is not limited to the above embodiment, and various changes and modifications can be made without departing from the spirit and scope of the present invention. Therefore, in order to make the scope of the present invention public, the following claims are attached.

This application claims priority from Japanese Patent Application No. 2016-245666 filed on December 19, 2016, the contents of which are incorporated herein by reference.

Claims

A rotating means for rotating at least one of radiation generating means for generating radiation and radiation detecting means for detecting the radiation;
Fixing means for rotatably holding the rotating means;
A radiation imaging apparatus comprising: a distance sensor that acquires distance information between the rotation unit and the fixing unit in a radial direction and a thrust direction with respect to a rotation direction of the rotation unit.
The radiographic apparatus according to claim 1, further comprising a control unit that corrects a deviation of the rotation unit with respect to the fixing unit according to the distance information and reconstructs a radiographic image of the subject.
The radiation imaging apparatus according to claim 1, further comprising a control unit that controls a timing at which the distance sensor acquires the distance information according to a rotation angle of the rotation unit.
The control means includes
Calculating a first ray equation of the radiation in a first radiation image acquired by a first rotation of the rotating means;
4. The light ray distance information for associating the first distance information acquired by the first rotation with the first light ray equation is generated according to the rotation angle of the rotation means. 5. The radiation imaging apparatus described in 1.
The control means is based on the first distance information acquired by the first rotation of the rotating means and the second distance information acquired by the second rotation of the rotating means. A second ray formula in the second radiation image obtained by the second rotation of the rotating means is calculated from the first ray formula of the radiation in the first radiation image obtained by the rotation of 1. The radiation imaging apparatus according to any one of claims 2 to 4, wherein the radiation imaging apparatus is characterized in that:
6. The radiographic apparatus according to claim 5, wherein the control means acquires the first distance information and the first light beam expression by rotating the rotation means around an alignment phantom. .
The control means calculates the second light ray equation from the first light ray equation based on a difference between the first distance information and the second distance information. The radiation imaging apparatus described.
The control means calculates the second light ray expression from the first light ray expression based on a function of the rotation angle of the rotation means, the first distance information, and the second distance information. The radiographic apparatus according to claim 5, wherein
The control means includes a plurality of radiation images acquired by the plurality of rotations of the rotation means based on a function of a plurality of distance information acquired by a rotation angle of the rotation means and a plurality of rotations of the rotation means 5. The radiation imaging apparatus according to claim 2, wherein a ray formula in a radiation image of a subject is calculated from an average of the ray formulas of the radiation.
10. The radiation imaging apparatus according to claim 9, wherein the control means acquires the plurality of distance information and the ray formula of the radiation by rotating the rotation means a plurality of times around an alignment phantom.
The radiation imaging apparatus according to any one of claims 1 to 10, wherein the distance sensor is installed in the rotating means and rotates together with the rotating means.
The rotating side surface of the rotating means rotates along the side surface of the fixing means,
The distance sensor is
Installed on the rotating side,
The radiation imaging apparatus according to claim 1, wherein a distance to a side surface of the fixing unit in the radial direction and the thrust direction is measured.
The rotating side surface of the rotating means rotates along the side surface of the fixing means,
The distance sensor is
Installed in the fixing means,
The radiation imaging apparatus according to claim 1, wherein a distance to the rotating side surface in the radial direction and the thrust direction is measured.
The control means includes
According to the rotation angle of the rotating means, the radiation generating means controls the timing of irradiating the radiation,
The timing at which the distance sensor acquires the distance information is controlled by at least one of the rising timing and falling timing of the pulse signal that defines the timing of irradiating the radiation, and the central timing of the rising and falling. The radiation imaging apparatus according to claim 2, wherein
The control means matches the time of the control means and the distance sensor, and controls the timing at which the radiation generating means irradiates the radiation according to the time,
The radiation imaging apparatus according to claim 13, wherein the distance sensor acquires the distance information according to the time.
6. The radiation imaging apparatus according to claim 5, wherein the control unit generates a radiation image for gain correction from a radiation image reconstructed based on the second light beam equation.
Radiation generating means for generating radiation;
A radiation detecting means for detecting the radiation; a rotating means for rotating at least one of the radiation generating means and the radiation detecting means;
Fixing means for rotatably holding the rotating means;
A distance sensor for acquiring distance information between the rotating means and the fixing means in a radial direction and a thrust direction with respect to a rotating direction of the rotating means;
A radiation imaging system comprising:
Rotating a rotating means including at least one of radiation generating means for generating radiation and radiation detecting means for detecting the radiation; and
Obtaining distance information between the rotating means and the fixing means that rotatably holds the rotating means in a radial direction and a thrust direction with respect to the rotating direction of the rotating means;
A radiation imaging method comprising:
A program for causing a computer to function as each unit of the radiation imaging apparatus according to any one of claims 1 to 16.