JPH0584303U - X-ray CT - Google Patents

Abstract

(57) [Abstract] [Purpose] To realize X-ray CT that does not cause artifacts even if the target position changes due to thermal expansion of the anode. [Structure] The anode 4 is thermally expanded, so that the detector 4
A displacement occurs in the X-ray 27 input to the. Z sensor 41
Detects this displacement and sends error information to the motor controller 43. The motor 42 moves the collimator 28 according to a control signal from the motor controller 43 to change the position of the slit 29, and allows the X-ray 27 to pass through the path when the anode 21 is cooled.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an improvement of an X-ray tube used for X-ray CT.

[0002]

[Prior Art]

 In order to know lesions and the like inside the human body, a method of irradiating X-rays and detecting the transmitted X-rays to detect the structure, lesion, etc. inside the human body from the difference in transmittance is used. X-ray CT is used as an apparatus for obtaining a tomographic image of the.

FIG. 3 shows an example of the configuration of the X-ray CT. In the figure, reference numeral 1 denotes an X-ray tube that generates X-rays, and the X-rays emitted from the X-ray tube 1 pass through a subject 3 through a collimator 2 and are detected by a detector 4. The data detected by the detector 4 is subjected to processing such as amplification and integration by the data collection device 5, AD-converted, and then processed by the data processing device 6 to reconstruct an image. Reference numeral 7 denotes a gantry on which the X-ray tube 1, the collimator 2, and the detector 4 are mounted, and the subject 3 is housed in the central opening.

Reference numeral 8 denotes a display device for displaying a tomographic image or the like based on the image-reconstructed data. Reference numeral 9 is a table / gantry controller for controlling the position of a table (not shown) on which the subject 3 is placed, and for controlling the posture and movement of the gantry 7, and 10 is a high pressure generator 11 for controlling the X-axis. It is an X-ray controller for supplying a high voltage to the ray tube 1.

Reference numeral 12 relates to tomography, such as communicating with an operator through an operating device 13, controlling the operation of the data processing device 6 and controlling the operation of the table / gantry controller 9 and the X-ray controller 10. It is a system controller that performs unified control.

FIG. 4 shows a configuration diagram of an example of the X-ray tube 1 used as an X-ray generation source in this X-ray CT. Only the main part of the X-ray tube 1 will be described below. In the X-ray tube 1 shown in the figure, 21 is an anode to which a high voltage is applied and which attracts thermoelectrons from a filament 23 attached to the cathode 22. Reference numeral 24 denotes a target that emits X-rays by collision of electrons from the filament 23, and the anode 21 is a rotating anode in order to prevent overheating of the target 24 due to collision of electrons. Reference numeral 25 is a glass tube for accommodating the above-mentioned respective parts to keep airtightness.

An electron beam 26 generated by thermoelectrons emitted from the filament 23 collides with the target 24, and the target 24 irradiates the target 24 with X-rays 27 toward the center of rotation of the X-ray tube 1 in the lower part of the figure.

FIG. 5 is a diagram showing the relationship between the electron beam 26 emitted from the filament 23 and the X-ray 27 emitted from the target 24. In the figure, the same parts as those in FIGS. 3 and 4 are designated by the same reference numerals. In the figure, 28 is a collimator having a slit 29 for obtaining a beam of thin X-rays 27.

The electron beam 26 emitted from the filament 23 collides with the target 24 and irradiates a beam of X-rays 27 downward in the drawing. The beam of X-rays 27 is narrowed down by the slit 29 of the collimator 28 and detected by the detector 4.

[0010]

[Problems to be solved by the device]

 By the way, as described above, the target 24 generates heat due to collision of the electron beam 26 due to thermoelectrons from the filament 23, and changes from room temperature to nearly 1000 ° C. Due to this heat generation, the target 24 and the anode 21 expand. The effect of this expansion will be described with reference to FIG. In the figure, the same parts as those in FIG. 5 are designated by the same reference numerals. In the figure, 31 is an anode after expansion due to heat generation, and 32 is a target after expansion.

As described above, the X-rays emitted from the expanded target 32, which is the target of the anode 31 after being expanded by thermal expansion, reach the detector 4 through the course of b shown by the broken line as shown in the figure. .

By the way, in order to improve the scan throughput and high-speed scanning, it is important to increase the capacity. Therefore, the anode capacity of the X-ray tube is increasing. Along with this increase in capacity, the positional variation of the target 24 in the axial direction due to thermal expansion also increases. This is a serious problem for detectors with non-uniform axial sensitivity and causes ring artifacts.

As a solution to this, a method of correcting the position variation due to the thermal expansion as it is and using software to correct it has been adopted, but there is a limit to that, and the yield of the detector is deteriorated.

The present invention has been made in view of the above points, and an object thereof is to realize an X-ray CT that does not cause artifacts even if the position of the target changes due to thermal expansion of the anode.

[0015]

[Means for Solving the Problems]

 The present invention for solving the above problems detects an X-ray tube, and an X-ray tube having a filament that emits an electron beam of thermoelectrons and a target that receives the electron beam and irradiates the X-ray toward the center of rotation. An X-ray CT having a detector, a collimator having a slit for controlling the route of the X-ray, and a Z sensor for detecting a detection position shift of the detector, detects the X-ray by moving the collimator. A motor controller for moving the collimator to correct the position shift of the detector, and a motor controller for receiving the detected position error information in the detector from the Z sensor and controlling the motor. Is to

A second invention is to detect the X-ray, and an X-ray tube having a filament that emits an electron beam by thermoelectrons and a target that receives the electron beam and irradiates the X-ray toward a rotation center. In an X-ray CT including a detector, a collimator having a slit for controlling the route of the X-ray, and a Z sensor for detecting a detection position shift of the detector, a magnetic field is generated to deflect the electron beam. A bias coil that constitutes a magnetic lens, a power supply that supplies a current to the bias coil, and a power supply that controls the current that is supplied to the bias coil upon receiving detection position error information from the Z sensor. And a controller for sending a signal.

[0017]

[Action]

 When the anode expands and the X-ray path shifts, the Z sensor detects the position shift of the detector and sends the position error information to the motor controller. The motor controller controls the motor to move the collimator and modify the X-ray path.

Further, the Z sensor sends the position error information to the controller, and the controller controls the power source to supply the current to the bias coil. The bias coil generates a magnetic field and constitutes a magnetic lens to deflect the electron beam and correct the X-ray path.

[0019]

【Example】

 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a main part of an X-ray CT according to an embodiment of the present invention. In the figure, the same parts as those in FIGS. 5 and 6 are designated by the same reference numerals. In the figure, reference numeral 41 is a Z sensor for detecting a positional deviation of the X-ray in the detector 4 from the data of the transmitted X-ray detected by the detector 4. Reference numeral 42 is a motor for shifting the position of the collimator 28 and changing the position of the slit 29 in order to correct the shift of the X-ray due to the position change due to the thermal expansion of the anode 21.

Reference numeral 43 is a motor controller for moving the collimator 28 based on the positional deviation information of the X-ray 27 from the Z sensor 41 and for sending a control signal to the motor 42 to operate the motor 42.

(A) is a diagram showing the path of the X-rays 27 by the anode 21 during cooling and the path of the X-rays 27 by the anode 31 after expansion. The X-rays 27 obtained by the anode 21 are slits. Although it reaches the detector 4 through the path “a” by 29, the X-ray 27 from the expanded anode 31 passes through the path “b”, so that the detector 4 detects at a different position. , Artifacts are generated in the image based on the obtained data.

The Z sensor 41 detects the change in the detection position of the detector 4 and sends a signal proportional to the detection error to the motor controller 43. The motor controller 43 sends a control signal to the motor 42 to change the position of the collimator 28.

(B) is a diagram showing a state in which the position of the collimator 28 is moved to the right in the figure by the motor 42. The collimator 28 is moved from the A position in (a) to the B position in (b). Because of the movement, the X-rays emitted from the expanded anode 31 pass through the moved slit 29, pass through the “c” path, and are the same as the “a” path from the anode 21 of the detector 4. Detected by position.

As described above, according to this embodiment, even when the anode expands, it is detected at the same position of the detector as when cooling. That is, even if the position of the target is sequentially changed by heating the anode, the position of the X-ray irradiated to the detector does not change, so that no artifact is generated.

The present invention is not limited to the above example. 2A and 2B are explanatory views of another embodiment of the present invention. FIG. 2A is a configuration diagram showing a main part of the X-ray CT of the embodiment, and FIG. 2B is a normal X-ray path according to the present embodiment. It is a figure which shows the state which was set to the path of.

In the figure, the same parts as those in FIG. 1 are designated by the same reference numerals. In the figure, 51 is a bias coil that creates a magnetic field for bending the route of the electron wire 26, and 52 is a power supply that supplies a current to the bias coil 51 to generate a magnetic field.

Reference numeral 53 denotes a controller which receives a detection value of the X-ray positional deviation from the Z sensor 41 of the detector 4 and gives a control signal for controlling the current supplied from the power source 52 to the bias coil 51 to the power source 52. is there.

The operation of the embodiment configured as described above will be described with reference to FIG. The X-rays emitted from the target 24 of the anode 21 pass through the slit 29 and reach the detector 4 through the path "a" as shown in FIG. When the anode 21 is heated and becomes the state of the anode 31 after expansion, the X-rays reach the detector 4 by the path "b", and the slice position on the detector changes.

Returning to FIG. 2, the Z sensor 41 detects this error and outputs an error signal to the controller 53. The controller 53 receives the error signal and sends a control signal to the power supply 52. The power source 52 generates a voltage based on the control signal and supplies the bias current to the bias coil 51. The bias coil 51 generates a magnetic field by this bias current. Due to the presence of this magnetic field, the path of the electron beam 26 is curved and collides with the expanded anode 31 (shown in FIG. 1), so that the collision position is sequentially changed, and the path of the irradiation X-ray 27 is changed. This path becomes the path "a" and continues until the Z sensor 41 stops outputting the error signal. Even if the error signal of the Z sensor 41 disappears, the control signal from the controller 53 does not change, and therefore the current flowing through the bias coil 51 also maintains the final value. When the anode contracts, the error signal output from the Z sensor 41 is in the negative direction, the path of the X-ray 27 is always held in the path "a", and the slice position becomes constant.

As described above, according to this embodiment, the slice position can be controlled constantly without using mechanical means.

[0031]

[Effect of the device]

 As described in detail above, according to the present invention, even if the position of the target changes due to thermal expansion of the anode, artifacts do not occur and the practical effect is great.

[Brief description of drawings]

FIG. 1 is a diagram showing a main part of an X-ray CT according to an embodiment of the present invention.

FIG. 2 is a diagram showing a main part of an X-ray CT according to another embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of an X-ray CT.

FIG. 4 is a schematic configuration diagram of a conventional X-ray tube.

FIG. 5 is a diagram showing a relationship between an electron beam and an X-ray in an X-ray tube.

FIG. 6 is a diagram showing an influence of expansion of an anode in an X-ray tube.

[Explanation of symbols]

 1 X-ray tube 4 Detector 23 Filament 24 Target 26 Electron beam 27 X-ray 28 Collimator 29 Slit 41 Z sensor 42 Motor 43 Motor controller 51 Bias coil 52 Power supply 53 Controller

Claims (2)

[Scope of utility model registration request] 1. A filament (23) which emits an electron beam (26) by thermoelectrons and X upon receiving the electron beam (26).
A target (2 that irradiates a line (27) toward the center of rotation
4), a detector (4) for detecting the X-rays (27), and a collimator (28) having a slit (29) for controlling the route of the X-rays (27). )
And a Z sensor (41) for detecting the detection position shift of the detector (4), the detector (4) for moving the collimator (28) to detect the X-ray (27). (42) for moving the collimator (28) to correct the positional deviation of the motor (42), and control of the motor (42) by receiving the detected position error information in the detector (4) from the Z sensor (41). And a motor controller (43) for performing the X-ray CT. 2. A filament (23) which emits an electron beam (26) by thermoelectrons and an X-ray (2) which receives the electron beam.
7) An X-ray tube (1) having a target (24) for irradiating the center of rotation, a detector (4) for detecting the X-rays (27), and control of the route of the X-rays (27). A collimator (28) having a slit (29) for performing the above, and a Z sensor (4) for detecting a detection position shift of the detector (4).
In an X-ray CT having 1), a bias coil (51) that generates a magnetic field to deflect the electron beam (26) and forms a magnetic lens, and a power supply that supplies a current to the bias coil (51). (5
2) and a controller (53) that sends a control signal to the power supply (52) to control the current supplied to the bias coil (51) upon receiving the detected position error information from the Z sensor (41). An X-ray CT characterized by being provided.