JPS62222599A - X-ray tube voltage measuring unit - Google Patents

Abstract

PURPOSE:To simply and accurately measure an X-ray tube voltage by finding the X-ray tube voltage based on the variation ratio of the logarithm of an X-ray transmission factor obtained from the output ratio of a reference X-ray detector and an X-ray detector. CONSTITUTION:An X-ray information signal is converted into an electrical signal with an X-ray detector 1, and amplified with an amplifier 3. The amplified signal is converted into a digital signal with an A/D converter 4, and inputted to a processing-memory unit 5. The unit 5 separates output information (Is) of a reference X-ray detector 1s from output information of the X-ray detectors, and stores independently them. Each value of output information is divided by the output information (Is) to obtain the transmission factor Yn(In/ Is) (N=1,2...) and then the logarithm of the transmission factor (log Yn) is found. The variation DELTA(log Yn) of the log Yn to the variation DELTAt of the thickness (t) of an X-ray absorption filter is obtained. A numerical value in which the variation ration of the logarithm of transmission factor of the X-ray filter is constant and a conversion value of the X-ray tube voltage are stored in the processing-memory unit 5 and compared with the value DELTA(log Yn)/DELTAt, and the X-ray tube voltage value in which the both values are identical is obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an X-ray tube voltage measuring device, and in particular, to a method for easily measuring the tube voltage of an X-ray tube when verifying, maintaining, etc. an X-ray generator. The present invention relates to an X-ray tube voltage measuring device.

[Prior art]

As shown in FIG. 4, the X-ray generator is composed of an X-ray tube 11 and a high voltage generator. Generation of X-rays involves accelerating thermionic electrons emitted from the filament 12 with a high voltage and causing them to collide with the anode 14, and the kinetic energy t of the thermionic electrons at this time
- by converting it into X-rays. X-ray tube 11
The voltage applied to is controlled by the slider 13.

To generate X-rays as described above, a predetermined high voltage is applied to
It is necessary to apply voltage to the X-ray tube, and when performing verification or maintenance of an X-ray generator, one of the inspection items is to measure the actual tube voltage of the X-ray tube when X-rays are generated. The conventional method for measuring the tube voltage of an X-ray tube is to directly measure the voltage between the terminals of the X-ray tube using a voltmeter or the like.

[Problem that the invention seeks to solve]

However, in the above conventional X-ray tube voltage measurement method, the measurement operation is complicated and may be dangerous because the voltage is high.

The present invention has been made in view of the above problems, and provides an X-ray tube that can be easily and accurately measured by detecting emitted X-rays and indirectly measuring the X-ray tube voltage. Aims to provide complete voltage measuring equipment.

[Means for solving problems]

The above problem is solved by a reference X-ray detector that includes a scintillator that converts XME fluorescence emitted from an X-ray tube and a photodetector that detects the fluorescence, and a reference X-ray detector that includes the scintillator and the photodetector. and an X-ray detection unit including, as an essential component, a plurality of X-ray detectors each having an X-ray filter having a different thickness arranged in front of a scintillator, and the criteria for changes in the thickness of the X-ray filter. It has an X-ray detector and an arithmetic processing unit that calculates the rate of change in the logarithm of the X-ray transmittance calculated from the output ratio of the X-ray detector, and calculates the tube voltage of the X-ray tube according to the rate. This problem is solved by the X-ray tube voltage measuring device of the present invention, which is characterized in that it determines the following.

[Effect]

The principle of the invention is explained as follows.

An X-ray with an intensity of N0 passes through a shielding object with a thickness of t, and the intensity becomes N.
Assuming that, we have the following relationship.

ゞ −“1°′°1 ・・・・・・・・・(
1)N.

From equation (1) Log (row) = -μm - ρ・t At this time, ρ is the absorption coefficient of quality 1 when the density of the shielding material is 1 μm.

ρ is determined by the material of the shield, and μm is a constant that depends on the X-ray energy (hv) within a certain range. In the present invention, since the energy of this X-ray is converted from the kinetic energy of electrons accelerated by the voltage applied to the X-ray tube, by finding the left side of equation (2), The purpose is to find the voltage applied to the

That is, in the X-ray tube voltage measurement apparatus of the present invention, X-ray tube voltage detection is performed in the following process.

(1) X-ray i emitted from the X-ray tube, a reference X-ray detector consisting of a scintillator that converts the X-rays into fluorescence, and a photodetector that detects the fluorescence (with a certain thickness in front of the scintillator) The X-ray intensity is detected by an X-ray filter (which may be equipped with an X-ray filter) and its X-ray intensity is measured. The scintillator and photodetector are provided, and in front of the scintillator (in front of the X-ray filter fs if an X-ray filter is placed in front of the scintillator) are X-ray filters fl, r, l, and each having a different thickness. ...detected by multiple X-ray detectors arranged fn't', and their X-ray intensities N1, N,
,...Measure Nn.

(2) X-ray intensity NL, N, I...N1 X-ray intensity N0
, and the respective XIw filters f,,f,.

...Transmittance Y1 s Ys ) for fn
'Yn (Yl = N 1/N@ # Y 1 = N
1/N o t ・”p Yn=Nn/N6 )t
-Multiple subdivisions.

(3) Logarithm of transmittance Log Yl, log Yl
, =log Yl gold determination, X-ray filter f, f
! , . . . This transmittance versus the change Δt in the thickness t of fn (Δ(1ogY)) (4) Set 7 to a value where − is constant #) Find the voltage applied to the X-ray.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a block diagram showing an embodiment of the configuration of the X-ray tube voltage measuring device of the present invention shown in FIG. 1;

FIG. 2 is a schematic diagram for explaining the XMA detection section.

As shown in FIG. 1, the configuration of the X-ray tube voltage measuring device of this embodiment includes an X-ray detection section 1 that detects incident X-rays, and an output signal from the X-ray detection section 1 that is converted into a voltage value. Arithmetic processing unit 2
and a display section 6 that displays the determined voltage value.

The arithmetic processing unit 2 further includes an amplification unit 3 for amplifying the output signal from the X-ray detection unit 1, and a conversion unit 4 for digitizing the analog information obtained by the amplification unit 3, and calculates the digitized information. It is composed of a calculation/storage unit 5 for storing data.

As shown in FIG. 2, the X-ray detection unit l includes a reference X-ray detector in each of the small chambers of the envelope 7, which has all the small chambers of the envelope 7, which is divided by partition walls and has a plurality of small chambers. IB and multiple X-ray detectors 1a, lb.

It is constructed by inserting 1c*1d.

The reference X-ray detector Is is a fluorescent plate 8I with a scintillator that converts the incident X-ray Lt into fluorescent light proportional to the amount of incident X-ray Lt. 1, and a photodetector 1 which is provided in close contact with the fluorescent plate 811 on the surface opposite to the X-ray incident surface and detects the fluorescent light.
0s and Karanashi, X-ray detector l a p 1. b e
1 c # l d are scintillator fluorescent plates 8m and 8b that convert incident X-rays into an amount of fluorescent light proportional to the incident amount.
, 8c, 8d, and X-ray filters 9a, 9b, 9c of different thickness provided in front of the X-ray incident surface of these fluorescent plates.
, 9d, and photodetectors 10a, 10b, 10ep 1 provided in close contact with the surface of the fluorescent plate opposite to the X-ray incident surface.
It consists of 0d.

Note that the thickness t of the X-ray filters 9a, 9b, 9e, and 9d is La p tb * Lc # jd, and in this example, tri ta < tb < tc <
In this example, the X-ray detector has 4
However, in order to increase the accuracy of the X-ray tube voltage measuring device,
X-ray detectors (The greater the number of X-ray detectors disposed in Sl, the better. In practice, it is desirable to provide three or more X-ray detectors.

The envelope 7 is necessary to protect the X-ray detectors 1s, la to 1d, and to prevent the intrusion of external light and the leakage of fluorescent light from other fluorescent plates. A material that does not transmit external light or fluorescent light at all is selected, and for example, it is preferable to use a plastic such as a colored acrylic plate or Bakelite plate.

The X-ray filters 9m and 9b*9c+9d are preferably made of a material that has a large X-ray absorption ability and whose X-ray transmittance changes greatly with changes in thickness, even if the thickness is less than a few inches. , e.g. Cu, AI.

Metal plates such as Sn and PB are preferably used.

Fluorescent plate 8s*8a*8be8et8d is CaWoa, B
i Go OZnS: Ag, BaFCl:
Eu, La0Br: 4312% Tm, (ZnCd)S: Ag, Y2O
28: Tb, Gd2O2S: Tb%Gd2
O□S: A phosphor coating liquid made by dispersing an X-ray phosphor such as Pr that emits light with high efficiency in a binder resin is applied onto a support such as paper or f-plastic. , coating a phosphor coating liquid on a phosphor plate obtained by drying to form a phosphor layer on a support, or on a substrate such as glass;
A self-supporting phosphor plate is obtained by peeling the dried phosphor layer from the substrate.

As the photodetectors 10arlOaplOb and 10cp10d, photoelectric conversion elements such as photodiodes and photomultiplier tubes that convert the fluorescence emitted from the fluorescent plates 8g and 8a to 8d into all-electric signals are used. The volume of can be reduced. It is preferable to use a field diode because manufacturing costs can be kept low.

Next, the calculation processing section 2 will be explained according to the voltage conversion calculation process.

As shown in FIG. 1, the X-ray information signal is converted into an electrical signal by the X-ray detector 1 and amplified by the amplifier 3.

After this amplified signal is digitized by the in-conversion section 4, it is input into the arithmetic/storage section 5.

In the calculation/storage unit 5, the output information from the reference Xa detector 1s and the other X-ray detectors 1&.

Output information C1,) from lb, 1c*1d.

(Is) tCIs) - (I4), each is stored once in Dokdo, and then the output information [work
].

Divide each value of (r*) sirs EFCIA) by the value of full output information [In], and each transmittance Yn ([In]
/(Ia]) (n=1 p 2 , 3 s 4 )e is determined, and the logarithm value log Ynf of the value of transmission $ Yn is determined.

Next, the change Δ(log Yn) f in the logarithm value 1ogYn with respect to the change Δt in the thickness 1) of the X-ray absorption filter
demand. In this embodiment, each X-ray detector 1a.

lb, lc, ld x-ray filter 9at9b.

Thickness of 9a, 9d ta e tb e tc s t
d is ta < lb If at least two of them are the same, it is considered that there is a linear relationship between the change Δt in the thickness of the X-ray absorbing filter and the change Δ(10gYn) in the above logarithm value.

It is a hot theory that if it is above, the accuracy will be high.

The calculation/storage unit 5 includes X-ray detectors laglb, l in advance.
The tube voltage of the X-ray tube, which stores the conversion value between the value at which the change rate of the logarithm of the transmittance of the transmittance curve of the X-ray filter used in c and ld is constant and the tube voltage of the X-ray tube. Search for values.

The voltage value thus determined is displayed on the display section 6.

Next, a specific example showing the relationship between the thickness and transmittance of an X-ray filter will be described.

FIG. 3 is a characteristic diagram showing the relationship between the thickness and transmittance of an X-ray filter.

X-ray filter made of Cu plate and ZnS: Fluorescent plate made of Ag phosphor? It is used as a component of an X-ray detector, and the X5! The thickness of the X-ray absorption filter (Cu plate) and Xll transmittance were measured by changing the tube voltage. Curves A, B, C, and D in the figure have X-ray tube voltages of 60 kVp, , and 80 k'Vp, respectively.

100kVp, 120kVp, etc. are shown in detail.

As shown in Figure 3, even if the X-ray tube voltage is different, as the thickness of the X-ray filter increases, the rate of change in the X-ray transmittance becomes smaller and approaches a constant value. It can be seen that the transmittance curve is approximated to a straight line.

〔Effect of the invention〕

As described above in detail, according to the present invention, the voltage applied to the X-ray tube is indirectly measured by the XR emitted from the X-ray tube without directly measuring the voltage applied to the X-ray tube. It is highly safe and easy to operate as it can measure , it is possible to provide an X-ray tube voltage measuring device that can detect X-rays in a wider energy range than other detectors and can accurately measure tube voltage.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the configuration of the X-ray tube voltage measuring device of the present invention. FIG. 2 is a schematic diagram for explaining the entire X-ray detection section. FIG. 3 is a characteristic diagram showing the relationship between the thickness and transmittance of an X-ray filter. FIG. 4 is a schematic diagram showing an example of an X-ray generator. DESCRIPTION OF SYMBOLS 1... X-ray detection part, 2... Arithmetic processing part, 3... Amplification part, 4... A/D conversion part, 5... Arithmetic/storage part,
6...Display section.

Claims (1)

[Claims] a reference X-ray detector including a scintillator that converts X-rays emitted from an X-ray tube into fluorescence; and a photodetector that detects the fluorescence; An essential component of the
a ray detection unit; and an arithmetic processing unit that calculates the rate of change in the logarithm of the X-ray transmittance determined from the output ratio of the reference X-ray detector and the X-ray detector with respect to the change in the thickness of the X-ray filter. An X-ray tube voltage measuring device characterized in that the tube voltage of the X-ray tube is determined based on the ratio.