A CT scanner which collects X-ray projection data of a subject and which generates an image in the subject from the projection data, the CT scanner includes tubes which emit X-rays and which include grids to switch emission and stoppage of the X-rays, a unit which generates a high voltage to be supplied to the tubes, a cable which sends the high voltage to each of the tubes, circuits which change potentials of the grids arranged in the tubes, respectively, a control unit which controls the circuits to switch the emission and the stoppage of the X-rays in a pulse manner while the tubes rotate around the subject, detectors arranged to face the tubes, respectively, and a unit which validates an output signal from the detector facing the tube emitting the X-rays and which invalidates an output signal from the detector facing the tube stopping the emission of the X-rays.
1. A CT scanner which collects X-ray projection data of a subject and which generates an image of the subject from the projection data, the CT scanner comprising:
first to third X-ray tubes which emit X-rays and which include grids to switch emission and stoppage of the X-rays;
a high-voltage generation unit which generates a high voltage to be supplied to the first to third X-ray tubes;
a high-voltage cable which sends the high voltage to each of the first to third X-ray tubes, the high-voltage cable connecting the high-voltage generation unit to the first X-ray tube, the second X-ray tube, and the third X-ray tube;
a plurality of grid control circuits which change potentials of the grids and are arranged near the first to third X-ray tubes, respectively, and include semiconductor switches;
a control unit which controls the grid control circuits to switch the emission and the stoppage of the X-rays in a pulse manner while the first to third X-ray tubes rotate around the subject; and
a plurality of X-ray detectors arranged to face the first to third X-ray tubes, respectively.
2. The CT scanner according to claim 1 , wherein the control unit controls the grid control circuits to prevent the X-rays from being emitted simultaneously by at least two X-ray tubes.
3. The CT scanner according to claim 1 , wherein the plurality of grid control circuits are arranged in the first to third X-ray tubes, respectively.
4. The CT scanner according to claim 1 , further comprising:
a plurality of high-voltage connectors which connect the first to third X-ray tubes to the high-voltage cable, respectively,
wherein the plurality of grid control circuits are contained in the plurality of high-voltage connectors, respectively.
5. The CT scanner according to claim 1 , wherein each X-ray tube contains a filament transformer which heats a cathode of each X-ray tube.
6. The CT scanner according to claim 1 , wherein the high-voltage cable has one core wire which sends the high voltage, and the first to third X-ray tubes are electrically connected to the core wire.
7. The CT scanner according to claim 1 , wherein the high-voltage cable is arranged so that the first to third X-ray tubes are arranged in order along the high-voltage cable.
8. The CT scanner according to claim 1 , wherein each X-ray tube contains a transformer which applies an alternating voltage to a cathode of each X-ray tube.
9. The CT scanner according to claim 1 , wherein a number of a plurality of X-ray tubes is n,
the plurality of X-ray tubes are arranged at intervals of 360/n degrees, and
the control unit controls the plurality of X-ray tubes to emit the X-rays sequentially, and to emit the X-rays a same number of times, while the plurality of X-ray tubes are rotated through 360/n degrees.
10. The CT scanner according to claim 1 , wherein each X-ray tube includes a unit which prevents an abnormal current from being introduced into a cathode of each X-ray tube.
11. The CT scanner according to claim 1 , wherein the control unit detects abnormalities of the first to third X-ray tubes, respectively, and controls the grid control circuits to constantly stop abnormal X-ray tubes while switching emission and stoppage of the X-rays in other X-ray tubes in the pulse manner, and to prevent the X-rays from being emitted simultaneously by at least two X-ray tubes.
12. The CT scanner according to claim 1 , wherein the high-voltage cable includes:
a first cable portion which connects the high-voltage generation unit to the first X ray tube;
a second cable portion which connects the first X ray tube to the second X ray tube; and
a third cable portion which connects the second X ray tube to the third X ray tube.
13. A CT scanner which collects X-ray projection data of a subject and which generates an image of the subject from the projection data, the CT scanner comprising:
a plurality of X-ray tubes which emit X-rays and which include grids to switch emission and stoppage of the X-rays;
a high-voltage generation unit which generates a high voltage to be supplied to the plurality of X-ray tubes;
a high-voltage cable which sends the high voltage to each of the plurality of X-ray tubes;
a plurality of grid control circuits which change potentials of the grids arranged in the plurality of X-ray tubes, respectively;
a control unit which controls the grid control circuits to switch the emission and the stoppage of the X-rays in a pulse manner while the X-ray tubes rotate around the subject, and which detects abnormalities of the plurality of X-ray tubes, respectively, and controls the grid control circuits to constantly stop the abnormal X-ray tubes while switching the emission and the stoppage of the X-rays in the other X-ray tubes in the pulse manner, and to prevent the X-rays from being emitted simultaneously by at least two X-ray tubes; and
a plurality of X-ray detectors arranged to face the plurality of X-ray tubes, respectively.
14. The CT scanner according to claim 13 , wherein the control unit controls the grid control circuits to prevent the X-rays from being emitted simultaneously by at least two X-ray tubes.
15. The CT scanner according to claim 13 , wherein the high-voltage cable connects high-voltage input portions of the plurality of X-ray tubes in parallel with an output portion of the high-voltage generation unit.
16. The CT scanner according to claim 13 , wherein the plurality of X-ray tubes include first to third X-ray tubes, and
the high-voltage cable includes:
a first cable portion which connects the high-voltage generation unit to the first X-ray tube;
a second cable portion which connects the first X-ray tube to the second X-ray tube; and
a third cable portion which connects the second X-ray tube to the third X-ray tube.
17. The CT scanner according to claim 13 , wherein the plurality of grid control circuits are arranged either in or near the plurality of X-ray tubes, respectively.
18. The CT scanner according to claim 13 , further comprising:
a plurality of high-voltage connectors which connect the plurality of X-ray tubes to the high-voltage cable, respectively,
wherein the plurality of grid control circuits are contained in the plurality of high-voltage connectors, respectively.
19. The CT scanner according to claim 13 , wherein each X-ray tube contains a filament transformer which heats a cathode of each X-ray tube.
20. The CT scanner according to claim 13 , wherein the high-voltage cable has one core wire which sends the high voltage, and the plurality of X-ray tubes are electrically connected to the core wire.
21. The CT scanner according to claim 13 , wherein the high-voltage cable is arranged so that the plurality of X-ray tubes are arranged in order along the high-voltage cable.
22. The CT scanner according to claim 13 , wherein each X-ray tube contains a transformer which applies an alternating voltage to a cathode of each X-ray tube.
23. The CT scanner according to claim 13 , wherein a number of the plurality of X-ray tubes is n,
the plurality of X-ray tubes are arranged at intervals of 360/n degrees, and
the control unit controls the plurality of X-ray tubes to emit the X-rays sequentially, and to emit the X-rays a same number of times, while the plurality of X-ray tubes are rotated through 360/n degrees.
24. The CT scanner according to claim 13 , wherein each X-ray tube includes a unit which prevents an abnormal current from being introduced into a cathode of each X-ray tube.