JP2013223814A - X-ray diagnostic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To be capable of constantly controlling the incident dose into an X-ray detector even when an effective area of an X-ray spot field is reduced by diaphragm operation of a movable X-ray diaphragm part.SOLUTION: An X-ray output of an X-ray tube 1 is controlled based on an X-ray output signal obtained by multiplying an X-ray output signal transmitted from a photomultiplier sensor 4 by 1/Y, wherein Y is the effective area ratio of an X-ray spot field 20 that changes in accordance with diaphragm operation of a movable X-ray diaphragm part 2.

Description

  The present invention relates to an X-ray diagnostic apparatus, and more particularly to an X-ray diagnostic apparatus that adjusts an X-ray output signal based on an area ratio of an X-ray sampling field that varies depending on an aperture opening amount of an X-ray diaphragm unit.

  In the X-ray diagnostic apparatus, the patient is irradiated with X-rays from an X-ray tube, and the X-rays are detected by an X-ray detector. In addition, a photomal sensor is provided on the front side of the X-ray detector. The photomal sensor has an X-ray sampling field, and an X-ray dose passing through the X-ray sampling field is detected as a photoelectrically converted optical signal. Is done. The detected optical signal is converted into an electric signal by a photomultiplier tube and enters an integrating circuit in the phototimer control circuit. The integration circuit converts and amplifies the voltage and current of the electric signal from the photomultiplier tube and integrates the time, and supplies the integration value to the multiplier. In the multiplier, a value obtained by multiplying the supplied integral value by the AEC correction coefficient and correcting the integral value is supplied to the comparison detector. In the comparison detector, when the supplied correction value matches the reference voltage, a signal for shutting off the X-ray with respect to the X-ray control circuit is sent to the switch, and the X-ray output is cut off. Thereby, the X-ray incident dose in the X-ray detector is controlled to be constant.

By the way, X-rays are narrowed down by the diaphragm portion as necessary, and are irradiated only to a necessary part of the patient. At this time, a part of the X-ray sampling field of the photomal sensor is blocked, and the effective area of the X-ray sampling field is reduced. When the effective area of the X-ray lighting field is reduced in this way, the X-ray dose detected by the photomultiplier sensor is also reduced in proportion to the reduction amount (see, for example, Patent Document 1).
JP 2006-334154 A

  However, conventionally, when the effective area of the X-ray sampling field decreases due to the aperture operation of the aperture section and the X-ray dose detected by the photomultiplier sensor decreases, the X-ray output is increased by the decrease. I was letting. For this reason, there was a problem that more than necessary X-rays were output, and the dose incident on the X-ray detector was not constant.

  The present invention has been made paying attention to the above circumstances, and the object of the present invention is to provide an incident dose to the X-ray detection means even when the X-ray is reduced and the X-ray amount detected by the photomal sensor is reduced. It is to provide an X-ray diagnostic apparatus that can control the frequency constant.

  In order to solve the above-mentioned problem, an invention according to claim 1 includes an X-ray generation unit that irradiates a subject with X-rays, an X-ray detection unit that detects X-rays irradiated on the subject, A photomal sensor that is provided on the X-ray incident side of the X-ray detection means, has an X-ray sampling field region that collects X-rays, and transmits an X-ray output signal according to the collected X-ray dose, and the photomultisensor A control unit that controls the X-ray output of the X-ray generation unit based on an X-ray output signal transmitted from the X-ray generation unit, and a necessary part of the subject by narrowing down the X-rays emitted from the X-ray generation unit The X-ray output signal transmitted from the photomultiplier sensor is 1 when the effective area ratio of the X-ray field area that changes based on the aperture operation of the aperture means is Y. / Y based on the X-ray output signal obtained by multiplication And controlling the X-ray output of the X-ray generating means Te.

  According to the present invention, even when X-rays are narrowed down by the diaphragm means, the amount of incident radiation to the X-ray detection means can be kept constant without outputting more than necessary X-rays.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is an overall configuration diagram schematically showing an X-ray diagnostic apparatus according to an embodiment of the present invention.

  This X-ray diagnostic apparatus includes an X-ray tube 1 as an X-ray generation unit, and an X-ray movable diaphragm unit 2 as an X-ray diaphragm unit is provided below the X-ray tube 1. Below the X-ray movable diaphragm unit 2, a bed 3 for laying a patient, a photomultiplier sensor 4, and an X-ray detector (X-ray detection means) 5 are provided.

  A photomultiplier tube 8 is connected to the photomultiplier 4 via an optical signal circuit, and the photomultiplier tube 8 is connected to an integrating circuit 10 of a phototimer control circuit 9 via an electric signal circuit. A multiplier 12, a comparison detector 13, and a switch 14 are sequentially connected to the integration circuit 10. An X-ray control circuit 15 is connected to the switch 14, and an X-ray density adjustment lever 16 is connected to the comparison detector 13.

  The X-ray tube 1, the X-ray movable diaphragm 2, and the bed 3 on which the patient lies is connected to a system controller 18 via a transmission circuit, and this system controller 18 is connected to the multiplier 12 via the transmission circuit. Has been.

  FIG. 2 is a plan view showing the photomal sensor 4 described above.

  An X-ray sampling field region (hereinafter referred to as X-ray sampling field) 20 is provided at the center of the photomultiple sensor 4, and the photomultiple sensor 4 transmits X-rays passing through the X-ray sampling field 20 to a light signal using fluorescent paper. It is to convert to. The daylighting field 20 has a size of 11 cm in length and 8 cm in width, for example.

  FIG. 3 is a plan view showing the X-ray movable diaphragm unit 2 as diaphragm means provided above the photomultiplier sensor 4.

  The X-ray movable diaphragm unit 2 includes left and right diaphragm blades 21 and 22 and upper and lower diaphragm blades 23 and 24. The left and right aperture blades 21 and 22 are slidably moved by a drive mechanism (not shown) in the left-right direction, and the upper and lower aperture blades 23 and 24 are orthogonal to the left-right direction.

  FIG. 4 is a plan view illustrating the X-ray irradiation area determined by the above-described upper, lower, left, and right diaphragm blades 21 to 24 as a projected image on the photomal sensor 4.

  The detection surface of the photomal sensor 4 is 2L in length and 2M in width, and its center coincides with the center O of the X-ray lighting field 20. The X-ray lighting field 20 has a distance from the center O to its upper end, a distance to the lower end, b, a distance to the left end, c, and a distance to the right end, and its total area S is (a + b). X (c + d).

  The moving distance of the upper diaphragm blade 23 from the upper end of the photomal sensor 4 is Aa, the moving distance of the lower diaphragm blade 24 from the lower end of the photomal sensor 4 is Ab, and the photomal sensor of the left diaphragm blade 21. The moving distance from the left end of 4 is Al, and the moving distance of the right diaphragm blade 22 from the right end of the photomultiplier sensor 4 is Ar.

  The size of the X-ray sampling field 20 associated with the position change of the diaphragm blades 21 to 24 is as follows when the diaphragm blades 21 to 24 in four directions move independently.

  When the movement distance Aa of the upper diaphragm blade 23> distance a or the movement distance Aa ≦ distance a, the length of the lighting field 20 in the upper region is Aa−a or a.

  When the moving distance Ab> distance b of the lower diaphragm blade 24 or the moving distance Ab ≦ distance b, the length of the light field 20 in the lower region is Ab−b or b.

  When the movement distance Al of the left diaphragm blade 21> distance c or the movement distance Al ≦ distance c, the length of the lighting field 20 in the left region is Al-c or c.

  When the movement distance Ar of the right diaphragm blade 22> distance d or movement distance Ar ≦ distance d, the length of the lighting field in the right region is Ar−d or d.

  Next, the operation of the X-ray diagnostic apparatus configured as described above will be described.

  X-rays output from the X-ray tube 1 are irradiated to the patient and detected by the X-ray detector 5. Further, the X-rays irradiated to the patient pass through the X-ray sampling field 20 of the photomultiplier sensor 4 and are detected, and the detection signal is transmitted as an optical signal to the photomultiplier tube 8. Then, after being converted into an electric signal by the photomultiplier tube 8, it is transmitted to the integrating circuit 10 of the phototimer control circuit 9. The data processed by the integration circuit 10 is multiplied by the AEC correction coefficient by the multiplier 12 and then transmitted to the comparison detector 13. The comparison detector 13 compares the voltage with a reference voltage, and the switch 14 is turned on / off based on the comparison value. By turning on / off the switch 14, the X-ray control circuit 15 controls the X-ray exposure time to be longer or shorter. As a result, the incident dose of the X-ray detector 5 is controlled to be constant. When the user increases / decreases the X-ray dose from the outside, the X-ray density adjustment lever 16 is operated. By this operation, the X-ray density adjustment voltage is taken into consideration by the comparison detector 13.

  By the way, the X-rays output from the X-ray tube 1 are focused by the X-ray movable diaphragm unit 2 as necessary, and are irradiated only to a necessary part of the patient. At this time, a part of the X-ray sampling field 20 of the photomal sensor 4 is blocked, and the effective area of the X-ray sampling field 20 is reduced. The X-ray dose detected by the photomal sensor 4 is proportional to the size of the area of the X-ray sampling field 20 if the X-ray dose output from the X-ray tube 1 is the same. Decreases, the X-ray dose detected by the photomal sensor 4 decreases, and the amount of X-ray output signal transmitted from the photomal sensor 4 decreases.

  Conventionally, when the X-ray dose detected by the photomal sensor 4 is decreased, the X-ray output is increased by that amount. Therefore, more than necessary X-rays are output, and the X-ray detector 5 receives the X-ray output. There was a disadvantage that the incident dose was not constant.

  Therefore, in the present invention, when a part of the X-ray sampling field 20 is covered with the diaphragm, the X-ray output signal transmitted from the photomultiplier sensor 4 is adjusted to output more X-rays than necessary. Control to not.

  Next, the adjustment operation of the X-ray output signal when a part of the X-ray lighting field 20 is covered will be described.

  First, when the left and right and upper and lower diaphragm blades 21 to 24 are slid and the X-rays are narrowed, the movement positions of the diaphragm blades 21 to 24 are detected using, for example, an encoder or a potentiometer. Specifically, for example, when a potentiometer is used, the movement amount when the diaphragm blades 21 to 24 are moved is represented as a change in resistance value, so that the change in resistance value is the same as the movement amount of the diaphragm blades 21 to 24. Become. When the system controller 18 recognizes the movement amount of the aperture blades 21 to 24, aperture opening information is obtained.

  After obtaining the aperture opening information, the effective area Sa of the X-ray sampling field 20 and the effective area ratio Y of the X-ray sampling field 20 are obtained by the system controller 18.

That is, as shown in FIG. 5, the distance from the X-ray focal point F to the aperture blades 21 to 24 is La, the distance from the X-ray focal point F to the photomultiplier sensor is Lb (where Lb is obtained from SID), and the aperture of the aperture When the irradiation field determined from the information is Sb, the area Sa of the effective X-ray lighting field 20 on the front surface of the X-ray detector is
Formula: Sa = (Sb × Lb) ÷ La.

The effective area ratio Y of the X-ray lighting field 20 is
Formula: Y = Sa ÷ S. (However, S is the total area of the X-ray lighting field)
In order to make the X-ray dose equivalent to the X-ray dose detected when the X-ray sampling field 20 is the entire visual field, the X-ray output signal transmitted from the photomal sensor 4 needs to be multiplied by 1 / Y.

  Therefore, in this embodiment, the reciprocal 1 / Y of the effective area ratio Y of the X-ray lighting field 20 obtained as described above is transmitted from the system controller 18 to the multiplier 12. The multiplier 12 multiplies the X-ray output signal transmitted from the photomal sensor 4 by the reciprocal 1 / Y of the effective area ratio Y. The X-ray output signal obtained by this multiplication is transmitted to the comparison detector 13 as a final X-ray output signal, and the X-ray output is controlled based on this final X-ray output signal.

  As described above, according to the embodiment of the present invention, when a part of the X-ray sampling field 20 is covered by the diaphragm, the reciprocal of the effective area ratio Y is added to the X-ray output signal transmitted from the photomal sensor 4. Since the X-ray output signal obtained by multiplying 1 / Y is used as the final signal, even if a part of the X-ray lighting field 20 is blocked, no more X-rays than necessary are output, and X-ray detection is performed. The incident dose of the device 5 can be always constant.

  6 and 7 show the positions of the aperture blades 21 to 24 with respect to the X-ray sampling field 20, that is, the effective area ratio of the X-ray sampling field (total 12 patterns).

  FIG. 6A shows a pattern 1 without an aperture. That is, when Aa ≦ a, Ab ≦ b, Al ≦ c, and Ar ≦ d, the area ratio Y1 is {(a + b) × (c + d)} / S = 1.

  FIG. 6B shows a pattern 2 having a diaphragm in four directions. That is, when Aa> a, Ab> b, Al> c, Ar> d, the area ratio Y2 is [{(Aa−a) + (Ab−b)} × {(Al−c) + (Ar−). d)}] / S.

  FIG. 6C shows the pattern 3 having the upper diaphragm. That is, when Aa> a, Ab ≦ b, Al ≦ c, and Ar ≦ d, the area ratio Y3 is [{(Aa−a) + b} × (c + d)] / S.

  FIG. 6D shows a pattern 4 having a lower diaphragm. That is, when Aa ≦ a, Ab> b, Al ≦ c, and Ar ≦ d, the area ratio Y4 is [{a + (Ab−b)} × (c + d)] / S.

  FIG. 6E shows a pattern 5 having a right diaphragm. That is, when Aa ≦ a, Ab ≦ b, Al ≦ c, and Ar> d, the area ratio Y5 is [(a + b) × {c + (Ar−d)}] / S.

  FIG. 6F shows a pattern 6 having a left diaphragm. That is, when Aa ≦ a, Ab ≦ b, Al> c, and Ar ≦ d, the area ratio Y6 is [(a + b) × {(Al−c) + d}] / S.

  FIG. 7A shows a pattern 7 having a diaphragm on the upper and lower sides. That is, when Aa> a, Ab> b, Al ≦ c, and Ar ≦ d, the area ratio Y7 is [{(Aa−a) + (Ab−b)} × (c + d)] / S.

  FIG. 7B shows a pattern 8 having an upper right diaphragm. That is, when Aa> a, Ab ≦ b, Al ≦ c, Ar> d, the area ratio Y8 is [{(Aa−a) + b} × {c + (Ar−d)}] / S.

  FIG. 7C shows a pattern 9 having an upper left diaphragm. That is, when Aa> a, Ab ≦ b, Al> c, and Ar ≦ d, the area ratio Y9 is [{(Aa−a) + b} × {(Al−c) + d}] / S.

  FIG. 7D shows a pattern 10 having a lower right diaphragm. That is, when Aa ≦ a, Ab> b, Al ≦ c, Ar> d, the area ratio Y10 is [{a + (Ab−b)} × {c + (Ar−d)}] / S.

  FIG. 7E shows a pattern 11 having a lower left aperture. That is, when Aa ≦ a, Ab> b, Al> c, and Ar ≦ d, the area ratio Y11 is [{a + (Ab−b)} × {(Al−c) + c}] / S.

  FIG. 7 (f) shows a pattern 12 having left and right left diaphragms. That is, when Aa ≦ a, Ab ≦ b, Al> c, Ar> d, the area ratio Y12 is [(a + b) × {(Al−c) + (Ar−d)}] / S.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above-described embodiments. For example, you may delete some components from all the components shown by embodiment mentioned above. Furthermore, you may combine the component covering different embodiment suitably.

1 is a schematic configuration diagram showing an X-ray diagnostic apparatus according to an embodiment of the present invention. The top view which shows the photomultiplier sensor of the X-ray diagnostic apparatus of FIG. FIG. 3 is a plan view showing upper, lower, left and right aperture blades of the X-ray movable aperture section of FIG. 1. FIG. 4 is a plan view illustrating an X-ray irradiation region determined by upper, lower, left and right diaphragm blades of FIG. 3 as a projected image on a photomultiplier sensor. The figure for calculating | requiring the effective area of the X-ray lighting field covered with the X-ray movable aperture part of FIG. The figure which shows the effective area pattern of the X-ray lighting field covered with the X-ray movable diaphragm part of FIG. The figure which shows the effective area pattern of the X-ray lighting field covered with the X-ray movable diaphragm part of FIG.

  DESCRIPTION OF SYMBOLS 1 ... X-ray tube (X-ray generation means), 2 ... X-ray movable aperture part (aperture means), 4 ... Photomal sensor, 5 ... X-ray detection means, 15 ... X-ray control means (control means), 20 ... X-ray sampling field area, 21-24 ... diaphragm blades, Y ... effective area ratio of X-ray sampling field, Sa ... effective area of X-ray sampling field, S ... total area of X-ray sampling field, Sb ... of aperture means Irradiation field obtained from the aperture amount, La ... distance from the X-ray focal point to the aperture blade, Lb ... distance from the X-ray focal point to the photomultiplier sensor.

Claims (4)

X-ray generation means for irradiating the subject with X-rays;
X-ray detection means for detecting X-rays irradiated on the subject;
A photomultiplier sensor provided on the X-ray incident side of the X-ray detection means, having an X-ray sampling field region for sampling X-rays, and transmitting an X-ray output signal in accordance with the collected X-ray dose;
Control means for controlling the X-ray output of the X-ray generation means based on the X-ray output signal transmitted from the photomultiplier sensor;
A diaphragm means for irradiating a necessary part of the subject by narrowing the X-ray irradiated from the X-ray generating hand;
X-rays obtained by multiplying the X-ray output signal transmitted from the photomal sensor by 1 / Y, where Y is the effective area ratio of the X-ray sampling field region that changes based on the aperture operation of the aperture means. An X-ray diagnostic apparatus for controlling an X-ray output of the X-ray generation means based on an output signal. The diaphragm means has a plurality of movable diaphragm blades,
The X-ray diagnostic apparatus according to claim 1, wherein the diaphragm amount of the diaphragm means is detected based on a movement amount of the diaphragm blade. The effective area of the X-ray sampling field area that changes based on the diaphragm operation of the diaphragm means is Sa, the irradiation field obtained from the diaphragm amount of the diaphragm means is Sb, and the distance from the X-ray focal point to the diaphragm blade is La, X When the distance from the line focus to the photomultiplier sensor is Lb, the Sa is
The X-ray diagnostic apparatus according to claim 2, wherein the X-ray diagnostic apparatus is obtained by the formula: Sa = (Sb × Lb) ÷ La. When the effective area ratio of the X-ray field area that changes based on the aperture operation of the aperture means is Y, and the total area of the X-ray field area is S, the Y is
The X-ray diagnostic apparatus according to claim 3, wherein the X-ray diagnostic apparatus is obtained by the equation Y = Sa ÷ S.

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