JP3451494B2 - X-ray tube voltage measuring device for X-ray CT system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray tube voltage measuring apparatus for an X-ray CT apparatus. More specifically, the present invention relates to X
X-ray CT equipment X-ray generator for verification and maintenance, etc.
The present invention relates to a device for simply measuring the tube voltage of an X-ray tube of a line generator.

[0002]

2. Description of the Related Art When measuring the tube voltage applied to an X-ray tube for verification and maintenance of an ordinary X-ray generator, the voltage applied to the X-ray tube is measured. There are connection type measuring devices that directly measure high voltage by connecting a voltmeter, and non-connecting type measuring devices that indirectly detect the voltage of the X-ray tube by detecting the X-ray generated from the X-ray tube. It is used.

By the way, X-ray CT (Computed)
In a tomography (computer tomography) apparatus, a set of an X-ray tube and a sensor for detecting X-rays emitted from the X-ray tube is usually a rotation center passing through the X-ray irradiation field from the X-ray tube to the sensor. The image is taken by placing the imaged region of the subject on the rotation center and in the vicinity thereof. In this device, generally, the rotational drive of the set of the X-ray tube and the sensor and the drive of the X-ray generator are interlocked, and in the state where the rotation of the set of the X-ray tube and the sensor is stopped. No X-rays are generated from the X-ray tube.

On the other hand, the conventional X-ray tube voltage measuring device is premised on the measurement when the X-ray tube is stationary.
X-ray tube is moved while making a large orbit like an X-ray CT machine.
When a line is generated, there is a problem that the X-ray tube voltage cannot be effectively measured. That is, using the connection-type tube voltage measuring device is dangerous because the measured voltage is a high voltage, and the X-ray tube itself rotates.
It is impractical to connect, and when measuring with a non-contact type tube voltage measuring device, if the X-ray detector is fixedly arranged, the X-ray tube circulates due to the direction dependency of the detector. There is a problem that the measurement value fluctuates depending on the position and the measurement accuracy decreases, and it is conceivable to rotate the X-ray detector in synchronism with the orbit of the X-ray tube. There is a problem that a driving means is required and the configuration becomes complicated.

Some X-ray CT apparatuses are capable of a special operation mode in which X-rays are generated while the circular motion of the X-ray tube is stopped, but in that case, a special operation is required. This is necessary and not practical, and the conditions change from those during actual shooting, so the measurement is not performed in the most preferable state.

In view of the above-mentioned problems of the prior art, the present invention therefore provides an X-ray C for moving the X-ray tube in an orbiting manner during imaging.
It is possible to measure the X-ray tube voltage of the T-apparatus under the same conditions as when shooting,
Moreover, it is an object of the present invention to provide an X-ray tube voltage measuring device having a simple structure and capable of highly accurate measurement without danger.

[0007]

According to the present invention, in order to achieve the above object, a set of an X-ray tube and a sensor for detecting X-rays emitted from the X-ray tube is moved to perform tomography. An apparatus for measuring a tube voltage of the X-ray tube of an X-ray CT apparatus for performing, wherein a scintillator for converting X-rays emitted from the X-ray tube into fluorescence and a method for detecting the fluorescence from the scintillator. A plurality of X-ray detectors having a photodetector, and all or all but one of the X-ray detectors are provided with an X-ray filter on the X-ray incidence side of the scintillator, The X-ray detector includes an arithmetic processing unit that calculates a tube voltage of the X-ray tube by using at least two of the outputs from the X-ray detector. Or 2 so as to cover the two open surfaces of the light-shielding X-ray transmitter. X-ray shielding plate is arranged to form a hollow cylindrical body, the scintillator is arranged inside the cylindrical body, and the photodetector is arranged in the axial direction of the cylindrical body in proximity to the scintillator. The X-ray filters of the X-ray detectors have mutually different thicknesses in the radial direction of the tubular body, and the photodetectors are superposed in the axial direction of the tubular body. Has been characterized,
An apparatus for measuring an X-ray tube voltage of an X-ray CT apparatus is provided.

In one aspect of the present invention, the ring shape of the X-ray filter is a ring shape.

In another aspect of the present invention, the scintillator is located at the center in the radial direction of the tubular body.

In another aspect of the present invention, the photodetector is arranged at a position protruding outward from at least one of the two X-ray shielding plates.

In another aspect of the present invention, all of the X-ray detectors are superposed so that the scintillators of the X-ray detectors are located on a straight line in the axial direction of the cylindrical body. .

[0012]

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a block diagram showing an embodiment of the overall construction of an X-ray tube voltage measuring apparatus of an X-ray CT apparatus according to the present invention. FIG. 1 is an X-ray detector of the measuring apparatus. FIG. 2 is a plan view (a) and a vertical sectional view (b) showing an example, and FIG. 2 is an enlarged sectional view of members constituting the X-ray detector of FIG. 1.

The apparatus of this embodiment, as shown in FIG.
A plurality of lines for detecting a line and converting it into an electric signal (2 in this embodiment)
X-ray detection including X-ray detectors 11A and 11B
And the X-ray detectors 11A and 11B of the X-ray detector.
An arithmetic processing unit 12 for obtaining a tube voltage value from the output signal of the
The display unit 16 displays the voltage value. Arithmetic processing unit 1
2 further receives the electric signals from the X-ray detectors 11A and 11B.
The amplification unit 13 that amplifies each and the amplifier obtained by the amplification unit
A / D converter 14 for digitizing analog signals, and here
Computation / storage unit that computes and stores digitalized signals
It is composed of 15 and. Two in the calculation / storage unit
Predetermined calculation based on the outputs of the X-ray detectors 11A and 11B
The tube voltage value is calculated according to the formula. Calculation of this tube voltage value
Are described, for example, in Japanese Patent Laid-Open No. 5-41290.
You can do it as if you were there. That is, the X-ray detection unit 10
Of the independent X-ray detectors 11A and 11B constituting the
The outputs obtained by amplifying these outputs by the amplification unit 13 are respectively
If [Ia] and [Ib] are set, X when the X-ray is generated
Between the tube voltage value [kVp] and [Ia], [Ib]
Is [KVp] = α {1 / log ([Ia] / [Ib])}
+ Β It was experimentally confirmed that the relational expression of here
Therefore, the thickness of each of the X-ray detectors 11A and 11B is t_a ，
t_b Has an X-ray filter that is_a <T _b so
And α and β are constants. Therefore, the tube voltage is known
Injecting X-rays from the X-ray tube at different tube voltages multiple times,
By obtaining outputs [Ia] and [Ib] at each measurement,
From the above equation, the constants α and β are obtained in advance to establish the relational expression,
If it is stored in the calculation / storage unit 15, the measured X
Inject X-rays from a tube to output [Ia] and [Ib]
Then, {1 / log ([Ia]
/ [Ib])} value, and the tube voltage value of the measured X-ray tube
[KVp] can be obtained.

As shown in FIG. 1, the X-ray detector 10 is formed by superposing two X-ray detectors 11A and 11B.

The X-ray detector 11A has X-ray shielding plates 1a and 2a, which are made of an X-ray shielding material such as lead, and which are substantially disc-shaped and are arranged in parallel with each other. To form a hollow cylindrical body, a scintillator 4a is arranged at the center of the cylindrical body, and a photoelectric converter 5a as a photodetector is arranged adjacent to the scintillator. As shown in FIG. 2, the scintillator 4a and the photoelectric converter 5a are housed and fixed in a light-shielding case 6a that transmits X-rays. Reference numerals 7a and 8a are wirings connected to the photoelectric converter 5a. As shown in FIG. 1, an opening is formed in the center of one X-ray shield plate 1a, and the structure including the scintillator 4a and the photoelectric converter 5a described in FIG. A part of the scintillator 4a projects outward, and the scintillator 4a is located inside the hollow cylindrical body, while the photoelectric converter 5a is located outside the hollow cylindrical body.

The X-ray detector 11B also has the same structure as the X-ray detector 11A, and the corresponding members are shown with the reference sign b instead of the reference sign a. However, as shown in the drawing, the X-ray filter 3a and the X-ray filter 3b have different thicknesses (that is, thicknesses in the radial direction of the cylindrical body). Further, as shown in FIG. 1, the X-ray detector 11B is arranged in the opposite direction to the X-ray detector 11A, that is, the structure including the scintillator 4b and the photoelectric converter 5b is flat. Through the opening formed in the face plate 1b,
It projects outward in the opposite direction to the detector 11A. That is, the two X-ray detectors are superposed back to back in the axial direction of the cylindrical body.

As shown in FIG. 1, the X-rays enter the X-ray detector from the outside in the radial direction of the cylindrical body through the X-ray filter.

As the X-ray filters 3a and 3b, it is preferable to use a material having a large X-ray absorption capacity and having a large change in X-ray transmittance with respect to a change in thickness even if it has a thickness of several mm or less.
For example, a metal plate of Cu, Al, Sn, Pb or the like is preferably used.

As the scintillators 4a and 4b, CaW is used.
O ₄ , Bi ₄ Ge ₃ O ₁₂ , ZnS: Ag, ZnS: C
u, BaFCl: Eu, LaOBr: Tm, (Zn, C
d) S: Ag, Y ₂ O ₂ S: Tb, Gd ₂ O ₂ S: T
b, Gd ₂ O ₂ S: Pr, etc., a single crystal of an X-ray phosphor that emits light with high efficiency by X-ray irradiation, or a sintered product obtained by baking these X-ray phosphors into, for example, a cylindrical shape. ,
A kneaded and molded mixture of an X-ray phosphor and a binder resin is used, and a phosphor coating solution obtained by dispersing the X-ray phosphor in the binder resin is used for paper, plastics, etc. Of the phosphor plate obtained by forming a phosphor layer on the support by coating and drying the support, or a phosphor layer obtained by coating and drying the phosphor coating solution on a substrate such as glass. A self-supporting fluorescent plate obtained by peeling from the substrate is also used.

As the photoelectric converters 5a and 5b, photodiodes and photomultiplier tubes which convert the fluorescence emitted from the scintillators 4a and 4b into electric signals are used. It is preferable to use a photodiode because the dimensions of the X-ray detectors 11A and 11B can be reduced.

FIG. 4 is a schematic front view showing how the measuring apparatus and X-ray detector of this embodiment are used, and FIG. 5 is a partially cutaway side view of the measuring apparatus.

Reference numeral 20 denotes a rotating portion of the X-ray CT apparatus, which has a substantially annular shape. X facing the inside of the rotating part
A line tube 21 is arranged, and an X-ray sensor 22 having a large number of measuring elements is arranged at a position facing the line tube 21. Reference numeral 23 denotes a mounting table on which a subject, for example, a person is positioned, and an imaging region of the subject, for example, a head on the mounting table 23 is positioned at the center of the rotating portion 20 at the time of photographing. The rotating portion 20 is rotated in the direction of the arrow, and the X-ray tube 21 is excited and X-rays are emitted along with this rotation, and the intensity of the X-rays that have passed through the imaging region of the subject and the like is detected by each measuring element of the sensor 22. To be done.

In order to measure the X-ray tube voltage of this X-ray CT apparatus with the above measuring apparatus, the measuring apparatus 30 is placed on the mounting table 23.

In this measuring apparatus, as shown in FIG. 5, the X-ray detecting section 10 is arranged in a protective cover 32,
The portions 34 other than the X-ray detection unit 10 are supported by the support legs 36. As the protective cover 32, a material having a desired hardness with little X-ray absorption, for example, a plastic such as a colored acrylic plate or a bakelite plate is used.

In the measuring device 30, the X-ray shield plates of the X-ray detectors 11A and 11B of the X-ray detector 10 are the same as the plane including the X-ray tube 21 and the sensor 22 (the plane within the plane of FIG. 4). It is arranged so as to be located in a plane. Therefore, the X-ray tube 21
The X-rays emitted from the X-ray detector 11 are always irradiated even if the rotating portion 20 of the X-ray CT apparatus rotates and the X-ray tube 21 circulates.
It is incident on A and 11B from a direction substantially orthogonal to the X-ray filters 3a and 3b.

According to the present embodiment as described above, while the measuring device is stationary, the rotating part 20 of the X-ray CT device is rotated to orbit the X-ray tube 21 and the same conditions as those at the time of imaging are set. Therefore, there is no directional dependence of the sensitivity due to the circulating position of the X-ray tube 21, and it is possible to perform highly accurate X-ray tube voltage measurement under constant conditions. Moreover, since the measuring device is not moved, the device configuration is simple and the safety is high.

In the above embodiment, two X-ray detectors using X-ray filters having different thicknesses are superposed, but one of these two X-ray detectors is an X-ray detector. Instead of the filter, a light-shielding X-ray transmissive body having a similar shape may be used. Further, three or more X-ray detectors may be used, and the larger the number of X-ray detectors, the more the function and accuracy of the apparatus can be improved.

Further, in the present invention, the X-ray filter may have a ring shape other than the ring shape, for example, a regular polygon ring shape,
This also produces a similar effect. Moreover, even if the scintillator is slightly displaced from the center in the radial direction of the hollow cylindrical body, a substantially similar effect can be obtained. Also, photodetectors can be placed on both sides of the scintillator, and two X
It can also be projected outward from the line shield. Also, X
It is preferable that all the X-ray detectors are superposed so that the scintillators of the X-ray detectors are located on a straight line in the axial direction of the cylindrical body, but a similar effect can be obtained even if they are slightly deviated from the straight line. can get.

[0031]

As described above, according to the present invention, the X-ray tube voltage of the X-ray CT device for moving the X-ray tube in the orbit during the radiography can be measured under the same condition as the radiography, and the configuration is simple. There is provided an X-ray tube voltage measuring device capable of highly accurate measurement without danger.

[Brief description of drawings]

FIG. 1 is a plan view and a vertical sectional view showing an embodiment of an X-ray detector of an X-ray tube voltage measuring device of an X-ray CT device according to the present invention.

FIG. 2 is an enlarged cross-sectional view of members constituting the X-ray detector of FIG.

FIG. 3 is a block diagram showing an example of the overall configuration of an X-ray tube voltage measuring device of an X-ray CT apparatus according to the present invention.

FIG. 4 is a schematic front view showing a usage pattern of the measuring device and the X-ray detector of FIGS. 1 to 3.

5 is a partially cutaway side view of the measuring device of FIGS. 1 to 3. FIG.

[Explanation of symbols]

1a, 1b X-ray shield 2a, 2b X-ray shield 3a, 3b X-ray filter 4a, 4b scintillator 5a, 5b photoelectric converter 6a case 7a, 8a wiring 10 X-ray detector 11A, 11B X-ray detector 20 X-ray CT device rotating part 21 X-ray tube 22 X-ray sensor 23 table 30 measuring devices 32 Protective cover

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H05G 1/00-2/00 A61B 6/00-6/14

Claims (4)

(57) [Claims] 1. An apparatus for measuring the tube voltage of the X-ray tube of an X-ray CT apparatus for performing tomography by moving a set of an X-ray tube and a sensor for detecting the X-ray emitted from the X-ray tube. It is provided with a plurality of X-ray detectors having a scintillator for converting X-rays emitted from the X-ray tube into fluorescence and a photodetector for detecting the fluorescence from the scintillator, An X-ray filter is arranged on the X-ray incident side of the scintillator in all or all of the line detectors, and at least two of the outputs from the plurality of X-ray detectors are used. The X-ray detector includes an arithmetic processing unit that calculates a tube voltage of the X-ray tube, and each of the X-ray detectors has two pieces so as to close two open surfaces of a ring-shaped X-ray filter or a light-shielding X-ray transmissive body. X
A line shielding plate is arranged to form a hollow cylindrical body, the scintillator is arranged inside the cylindrical body, and the photodetector is arranged close to the scintillator in the axial direction of the cylindrical body. The X-ray filters of the X-ray detectors have mutually different thicknesses in the radial direction of the tubular body, and the plurality of photodetectors are superposed in the axial direction of the tubular body. An X-ray tube voltage measuring device for an X-ray CT device. 2. The X-ray tube voltage measuring device for an X-ray CT apparatus according to claim 1, wherein the ring shape of the X-ray filter is a ring shape. 3. The X-ray tube voltage measuring device of an X-ray CT device according to claim 1, wherein the scintillator is located at the center in the radial direction of the cylindrical body. 4. The X-ray detectors according to claim 1, wherein all of the X-ray detectors are superposed so that the scintillators of the X-ray detectors are located on a straight line in the axial direction of the cylindrical body. An apparatus for measuring an X-ray tube voltage of the X-ray CT apparatus according to claim 1.