JPS60153848A - Detection circuit of x-ray examination apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention Field of Application of the Invention The present invention detects the output of X-rays after passing through an object in an X-ray inspection device such as an X-ray CT device or a baggage inspection device, and sends a detection signal to an N-converter. The present invention relates to a detection circuit that sends out a signal, and more particularly to a detection circuit for an X-ray inspection apparatus that reduces the measurement amplitude in an integrator and enables high-speed and highly accurate measurement.

Prior Art and Problems The X-ray fluoroscopic inspection device 1 and baggage inspection device shown in FIG.
irradiating an X-ray pulse 4 from an X-ray tube 2 to a subject 3;
The X-ray output after passing through the object 3 is detected by a detector 5 such as a semiconductor detector or an ion chamber detector and sent to a detection circuit 6, which converts the input signal into a voltage and detects it. The signal was sent as a signal to a Φ converter (not shown), and the projection data of the X-ray onto the subject 3 was measured. Then, the subject 3 was sequentially moved relative to the X-ray tube 2 and the detector 5, as shown by arrow A, for example, and projection data of each part of the subject 3 was obtained. Similarly, in the X-ray CT apparatus 7 shown in FIG. A detection signal was sent to the converter.

The X-ray tube 2 and the detector 5 are mounted on a rotary plate 8 at symmetrical positions with the subject 3 in between, and the rotary plate 8 is rotated by an appropriate angle in the direction of arrow B, for example. Then, projection data from all angles around the subject 3 was measured.

In both of the apparatuses shown in FIG. 1 and FIG. 2, the way in which the X-rays detected at the position of the detector 5 are emitted is as shown in FIG. 3.
Although it suddenly decreases in the region W where the subject 3 is placed, the magnitude of the X-ray output within the region W is almost the same and does not change much. In order to obtain projection data in a region W where the magnitude of the X-ray output does not change much, the detector 5 is, for example, an electrode D1 of a semiconductor detector or an ionization chamber detector, as shown in FIG. D2-Dn are arranged at a very small pitch, and the current-voltage converter 9 and the integrator 10 are arranged as the detection circuit 6 using individual electrodes D'*D2...Dn.
are connected in series to the above-mentioned side electrodes f)t, f)2...
An input signal s1 from Dn is extracted as a detection signal S2 corresponding to each position by a corresponding current-voltage converter 9 and an integrator 10, respectively. However, in this case, the irradiation of X-ray pulse 4 for each homogeneous order is almost the same intensity,
The attenuation of the X-rays due to transmission through the object 3 is uniform, and the X-ray output at the position of the detector 5 does not change much.
Since the arrangement pitch of each electrode D11D2...Dn is very small, for example, 0.75 to LCjm, the difference in the output of the detection signal S2 between adjacent channels output from the detection circuit 6 or the next X-ray exposure The difference from the X-ray detection signal at the time of radiation is not very large. Similarly, the difference in detection signals between adjacent channels in the X-ray CT apparatus 7 shown in Figure IEG-2 and the difference in output for each rotation angle of 0.5 to 1 degree were not very large.

In such a state, the detection circuit of the conventional X-ray inspection apparatus is busy, operational amplifier 11 and resistor R as shown in FIG.
1, and an integrator 15, which has a current discharge switch 14 connected in parallel. and,
As shown in FIG. 6(a), the X-ray tube 2
The detector 5 detects the X-ray output after the X-ray pulse 4 emitted from the object 3 passes through the object 3, and the
The input terminal 16 of the current-voltage converter 120 receives the signal output from the input terminal io, and the current-voltage converter 12 converts the input signal io into a voltage Eo. At this time, the voltage value of the output of the current-voltage converter 12 changes to E depending on the magnitude of the input signal io from the detector 5, as shown in FIG. 6(b).
l, E2. It changes little by little like E5. This voltage E
1. E2. E5 is converted into a current i by a resistor R2 and input to an integrator 15. In this integrator 15, the discharge switch 14 is turned on immediately before the current i is input, that is, immediately before the X-ray pulse 4 in FIG. 6(a) is irradiated (see FIG. 6<C>). , by discharging the integrating capacitor C to
), the output E of the integrator 15 is lowered to the 0 level each time, and from that state the output E of the current-voltage converter 12 is
1. E2. The battery is charged in an amount corresponding to E3, and a detection signal E is output from the operational amplifier 13 for integration. This detection signal E is sent to the Φ converter 18 via a detection channel changeover switch 11 such as a multiplexer, and is measured as X-ray inspection data.

However, in this case, each time the output E of the integrator 15 is irradiated with 1@ of the X-ray pulse 4, the output E of the integrator 15 is lowered to the θ level, and then raised again from O by an amount corresponding to the output of the current-voltage converter 12. The measured amplitude of 15 had to have a wide enough width to rise to the maximum voltage value (eg 0-8v). Therefore, the amount of falling and rising times of the integrator 15 increases each time, and it is difficult to speed up the measurement time of the detection circuit in consideration of the stabilization time of the analog system. Furthermore, as shown in FIG. 3, in a state where the X-ray output is suddenly small within the area W where the subject 3 is placed, and the magnitude of the X-ray output within that area W hardly changes, As shown in FIG. 6(d), if the magnitudes of the detection signals E between each homogeneous or adjacent channel of X-ray irradiation are directly compared, it is difficult to accurately read the output difference between the respective detection signals E. was difficult. Therefore, it was not possible to perform highly accurate measurements and it was not possible to obtain good inspection images.

Purpose of the Invention The present invention has been made to solve the above-mentioned problems, and by extracting only the difference in detection signals for each X-ray irradiation, the measurement amplitude of the integrator is reduced and the measurement speed is high An object of the present invention is to provide a detection circuit for an X-ray inspection device that enables highly accurate measurement.

SUMMARY OF THE INVENTION According to the present invention, an input signal from a detector for detecting the X-ray output after an X-ray pulse emitted from an X-ray tube passes through an object is converted into a current-voltage converter. In the detection circuit of the X-ray inspection apparatus, which converts the voltage through the integrator and sends the detection signal to the converter N, a differentiator is provided between the current-voltage converter and the integrator, This is achieved by providing a detection circuit for an X-ray inspection apparatus characterized in that a differential output between a detection signal during irradiation and a detection signal during the next X-ray irradiation is provided.

Embodiments of the Invention Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The detection circuit of the X-ray inspection apparatus according to the present invention includes a current-voltage converter 12, a differentiator 19, and an integrator 15, as shown in FIG. The current voltage converter 121-1:,X
The signal i outputted as a current from the line output detector 5 is received by the power output terminal 16 and converted into a voltage EO, and is formed by connecting an operational amplifier 11 for current-voltage conversion and a resistor R1 in parallel. A differentiator 19 is connected to the output side of the current-voltage converter 12. This differentiator 19 receives the output voltage Eo of the current-voltage converter 12 and provides an output proportional to the time differentiation of the input signal. An analog switch 20 that is turned on only during the period, and an integrator 15 that will be described later only when the input voltage EO from the current-voltage converter 12 changes.
A differential capacitor C1 through which a current i flows is connected in series to the differential capacitor C1. Here, the on/off timing of the analog switch 20 is as shown in FIG. 8(C). It is likely to be turned off slightly earlier. That is, the above output voltage EO
If the pulse width is '6t' and the conduction time of the analog switch 20 is t', it is set so that t'<t. In this way, there is no charge flowing into the differential capacitor C1 when the X-ray pulse falls, and the current i flows through the differential capacitor C1 only when the output voltage EO rises (Fig. 8(d) )reference). An integrator 15 is connected to the output side of the differentiator 19. This integrator 15 inputs the output current i of the differentiator 19, integrates it for a specified duration, and provides an output proportional to the input integral value.
3, and the integrating capacitor C2, and the integrating capacitor C2.
and a discharge switch 14 are connected in parallel. Here, as shown in FIG. 8(e), the discharge switch 14 is turned on only once, immediately before taking in a series of signals input from the differentiator 19.

Next, the operation of the detection circuit according to the present invention will be explained with reference to the timing diagram shown in FIG. First, as shown in FIG. 8(a), the detector 5 detects the X-ray output after the X-ray pulse 4 emitted from the X-ray tube 2 passes through the object 3 at appropriate time intervals. The signal output from the detector 5 as a current io is received by the input terminal 16 of the current-voltage converter 12 (the seventh
), this current-voltage converter 12 converts the input signal io
Convert to voltage EO. At this time, the voltage value of the output of the current-voltage converter 12 changes to El depending on the magnitude of the input signal io from the detector 5, as shown in FIG. 8(b).
, E2. It changes little by little like p and s. This voltage E
1. E2. E5 is converted into a current by the resistor R2 of the differentiator 19, and by turning on and off the analog switch 20 shown in FIG. 8(C), the differential capacitor C1 receives the current as shown in FIG. 8(d).
As shown in FIG. 1, current i flows only when the output voltage EO of the current-voltage converter 12 rises. Here, at the output voltage EO, when the output voltage E2 due to the second X-ray pulse irradiation is smaller than the first output voltage E1, the current 12 flowing through the differential capacitor C1 is in the negative direction. flows. Also, the third output voltage Es is the second output voltage Es.
When the output voltage E2 is also larger than the current output voltage E2, the current i3 flows in the positive direction. That is, the previous differential capacitor C1
Compared to the magnitude of the voltage stored in
The difference from the previous X-ray output detection result can be extracted based on the direction and magnitude of the current i. The output current i of the differentiator 19 is input to the integrator 15, and in this integrator 15, the switch 14 for discharging the integrating capacitor C2 is activated as shown in FIG.
e>, it is turned on only once just before taking in a series of signals input from the differentiator 19, discharging the integrating capacitor C2, thereby setting the initial data of the detection circuit to 0, and the subsequent Remains off during measurement.

Therefore, the integrator 15 does not fall to the 0 level every time after it is initially set to the 0 level. When the output current i1 of the differentiator 19 is first input from this initial 00 level state, as shown in FIG. is output as a detection signal E. Next, when the output current 12 in the negative direction is input, negative integration is performed from the previous integral value to obtain an amount proportional to the difference between the output E2 and El of the current-voltage converter 12 as shown in FIG. 8(b). outputs a lower integral value. Next, when the output current i5 in the positive direction is input, positive integration is performed from the previous integral value, and the outputs E3 and E of the current-voltage converter 12 shown in FIG. 8(b) are
It outputs an integral value that is proportional to the difference between the two. In this way, the integrator 15 integrates only the amount corresponding to the difference in the output Ell of the current-voltage converter 120 from the previous integrated value, and outputs the detection signal E. Therefore, this detection signal E is Only the difference output between the detection signal from the previous X-ray irradiation and the detection signal from the next X-ray irradiation will change.

Then, as shown in FIG. 7, the detection signal E is sent to the Φ converter 18 via a detection channel changeover switch 1T such as a multiplexer, and is measured as X-ray inspection data.

FIG. 9 is a circuit diagram showing a modification of the detection circuit according to the present invention. In this modification, the differentiator 1g is composed of only a resistor R2 and a differential capacitor C1, and is mainly used when irradiating continuous X-rays instead of X-ray pulses. Features of X-ray CT equipment, baggage inspection equipment, etc.
Since the electrodes of the X-ray output detector are arranged at a very small pitch, the sample pitch is small, and the sampling rate is high, even when continuous X-rays are irradiated, the input current i (1 is , as shown in FIG. 10(a), the data shows a nearly square wave-like change.Therefore, the current i output from the differentiator 1g and input to the integrator 15 is as shown in FIG. b) K], 8th
The output waveform is not much different from the output waveform shown in Figure (d). Therefore, even if the differentiator 19' is not provided with the analog switch 20, it is possible to extract only a change in the differential output of the detection signal E from the integrator 15 as shown in FIG. 10(C).

In addition, in the above description, an X-ray inspection apparatus having a multi-channel detector 5 like an X-ray CT apparatus has been mainly explained, but the present invention is not limited to this, and can be applied to an X-ray inspection apparatus having a single-channel detector. The present invention can also be similarly applied to a detection circuit of an X-ray inspection apparatus in which the detector is fixed and the measured data changes over time as the subject moves.

Effects of the Invention As explained above, the present invention provides a differentiator 19 between the current-voltage converter 12 and the integrator 15, and uses the differentiator 19 to calculate the difference in magnitude of the output voltage Eel of the current-voltage converter 12. The current i in the positive direction or the negative direction is output to the integrator 15 according to the current, and the integrator 15 is set to the O level only once just before taking in a series of detection signals, and then integrates continuously. The integrator 15 calculates the output voltage E of the current-voltage converter 12 from the previous integrated value.
The detection signal Et- is obtained by integrating only the amount corresponding to the difference in magnitude of O.
It will be output.

Therefore, the detection signal from the previous X-ray irradiation and the
It can be detected as a differential output from the detection signal during radiation irradiation. From this, the amount of falling and rising of the detection signal E of the integrator 15 only needs to be the difference between the detection signal E between the previous time and the next time, and the measured amplitude of the integrator 15 can be compared with the conventional one. For example, it can be reduced to about 172 to 173, and the settling time of the detection signal E as analog data can be shortened. Therefore, the measurement time of the detection circuit can be sped up. In addition, since the measurement amplitude can be reduced as described above, the gain of the integrator 15 can be set higher than before, which improves the A of the detection circuit system and reduces the quantization error of the Φ converter. Even if the magnitude of the X-ray output hardly changes within the region W where the subject 3 is placed, each detection signal E
The output difference can be read with high accuracy. Therefore, it is possible to perform highly accurate measurements and to obtain good inspection images.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the tIi X-ray fluoroscopic inspection device, Fig. 2 is an explanatory diagram showing the X-ray CT device, Fig. 3 is a graph showing the state of change in the X-ray output transmitted through the subject, and Fig. 4 is the above An explanatory diagram showing a detector and a detection circuit of an X-ray inspection device, FIG. 5 is a circuit diagram showing a detection circuit of a conventional X-ray inspection device, FIG. 6 is a timing diagram thereof, and FIG. FIG. 8 is a circuit diagram showing a detection circuit of the line inspection device, FIG. 8 is a timing diagram thereof, FIG. 9 is a circuit diagram showing a modified example, and FIG. 10 is a timing diagram thereof. 2... X-ray tube, 3... Subject, 4... X-ray pulse, 5... Detector, 6... Detection circuit, 12
...Current-voltage converter, 13...Operational amplifier for integration, 14...Switch for discharging, 15...-integrator, 18..., converter, 19,・i g-・・Differentiator, 20... Analog switch, C1... Differential capacitor, C2...
Integrating capacitor, E-...detection signal, R1, R2...
...Resistance, IO...Input signal. Applicant Hitachi Medeico Co., Ltd.

Claims (1)

[Claims] 1. An input signal from a detector that detects the X-ray output after the X-ray pulse emitted from the X-ray tube passes through the object is transmitted through a current-voltage converter and an integrator. In the detection circuit of the X-ray inspection device that converts the voltage and sends the detection signal to the Φ converter, a differentiator is provided between the current-voltage converter and the integrator, and the detection signal from the previous X-ray irradiation is 1. A detection circuit for an X-ray inspection apparatus, characterized in that a differential output from a detection signal at the time of the next X-ray irradiation is detected. 2. The detection circuit for an X-ray inspection apparatus according to claim 1, wherein the differentiator is a resistor, an analog switch, and a differential capacitor connected in series. 3. The detection circuit for the X-ray inspection apparatus according to claim 2, wherein the analog switch is turned on only during the irradiation of the X-ray pulse. 4. The integrator comprises an operational amplifier and an integrating capacitor. 2. A detection circuit for an X-ray inspection apparatus according to claim 1, wherein a switch for discharging the integrating capacitor is connected in parallel. 5. The detection circuit for an X-ray inspection apparatus according to claim 4, wherein the discharge switch is turned on only once immediately before the acquisition of a series of detection signals.