X-ray diagnostic apparatus
An X-ray diagnostic apparatus according to embodiments includes an X-ray tube assembly and a grid potential control circuitry. The X-ray tube assembly includes a filament that emits electrons, a target that generates X-rays by receiving the electrons, and a grid having a potential for adjusting a potential gradient around the filament. The grid potential control circuitry switches the potential of the grid to a potential where the potential gradient around the filament becomes greater than a potential gradient generated by a potential of the filament and a potential of the target.
1. An X-ray diagnostic apparatus comprising:
an X-ray tube assembly including a filament that emits electrons, a target that generates X-rays by receiving the electrons, and a grid having a potential to adjust a potential gradient around the filament; and
grid potential control circuitry configured to switch the potential of the grid to a potential at which the potential gradient around the filament becomes greater than a potential gradient generated by a potential of the filament and a potential of the target.
2. The X-ray diagnostic apparatus according to claim 1 , further comprising:
tube current detection circuitry configured to detect a tube current flowing between the filament and the target,
wherein the grid potential control circuitry is further configured to switch the potential of the grid to the potential at which the potential gradient around the filament becomes greater than the potential gradient generated by the potential of the filament and the potential of the target, and thereafter perform control to decrease the potential of the grid when the tube current detected by the tube current detection circuitry becomes greater than a target tube current, and increase the potential of the grid when the tube current detected by the tube current detection circuitry becomes smaller than the target tube current.
3. The X-ray diagnostic apparatus according to claim 2 , wherein when pulse fluoroscopy is performed, the grid potential control circuitry is configured to perform the control at a cycle shorter than a frame rate of the pulse fluoroscopy.
4. The X-ray diagnostic apparatus according to claim 2 , wherein when pulse fluoroscopy is performed, the grid potential control circuitry is configured to perform the control for each frame of the pulse fluoroscopy.
5. The X-ray diagnostic apparatus according to claim 2 , further comprising:
a filament transformer to control an electric current flowing through the filament; and
control circuitry configured to receive a value of the tube current detected by the tube current detection circuitry and control the grid potential control circuitry based on the value,
wherein the tube current detection circuitry and the filament transformer are installed in the X-ray tube assembly and the value is transmitted from the tube current detection circuitry to the control circuitry through a path different from a path through which the tube current detected by the tube current detection circuitry flows.
6. The X-ray diagnostic apparatus according to claim 3 , further comprising:
a filament transformer to control an electric current flowing through the filament; and
control circuitry configured to receive a value of the tube current detected by the tube current detection circuitry and control the grid potential control circuitry based on the value,
wherein the tube current detection circuitry and the filament transformer are installed in the X-ray tube assembly and the value is transmitted from the tube current detection circuitry to the control circuitry through a path different from a path through which the tube current detected by the tube current detection circuitry flows.
7. The X-ray diagnostic apparatus according to claim 4 , further comprising:
a filament transformer to control an electric current flowing through the filament; and
control circuitry configured to receive a value of the tube current detected by the tube current detection circuitry and control the grid potential control circuitry based on the value,
wherein the tube current detection circuitry and the filament transformer are installed in the X-ray tube assembly and the value is transmitted from the tube current detection circuitry to the control circuitry through a path different from a path through which the tube current detected by the tube current detection circuitry flows.
8. The X-ray diagnostic apparatus according to claim 1 , wherein the grid potential control circuitry is further configured to switch the potential of the grid based on a relationship between a target tube current according to an imaging condition and the potential of the grid.
9. The X-ray diagnostic apparatus according to claim 8 , wherein the relationship used by the grid potential control circuitry is obtained by actual measurement.
10. The X-ray diagnostic apparatus according to claim 8 , wherein the relationship used by the grid potential control circuitry is obtained by simulation.
11. The X-ray diagnostic apparatus according to claim 8 , wherein the relationship used by the grid potential control circuitry is updated according to a thickness of the filament.
12. The X-ray diagnostic apparatus according to claim 8 , wherein the relationship used by the grid potential control circuitry is updated periodically.
13. The X-ray diagnostic apparatus according to claim 8 , further comprising:
filament current measuring circuitry configured to measure an electric current flowing through the filament,
wherein the grid potential control circuitry is further configured to switch the potential of the grid based on the relationship and the electric current measured by the filament current measuring circuitry.
14. The X-ray diagnostic apparatus according to claim 8 , further comprising:
filament temperature measuring circuitry configured to measure a temperature of the filament,
wherein the grid potential control circuitry is further configured to switch the potential of the grid based on the relationship and the temperature measured by the filament temperature measuring circuitry.