JPS6247101Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an X-ray detector. More specifically, the present invention relates to an X-ray detector used in an X-ray computerized tomography apparatus (hereinafter simply referred to as an X-ray CT apparatus).

An X-ray CT device irradiates a subject with X-rays from an X-ray tube, detects the X-rays that have passed through the subject using an Through processing, a tomographic image of the subject is obtained.

First, the general operation of an X-ray detector and the drawbacks of conventional devices will be explained with reference to FIGS. 1 and 2. FIG. 1 is a diagram showing an example of the external appearance of a conventional X-ray detector and an example of a signal extraction means. In Fig. 1, 1 represents a case, in which a high-pressure
Line detection gas is filled. The type and pressure of this X-ray detection gas are selected from those well known to those skilled in the art. For example, rare gases with large atomic numbers such as xenon, krypton, and argon are used. The front part 3 of the case 1 is made of a material that is transparent to X-rays, such as plastic or aluminum. Here, it can be said that the X-ray detection gas filling the case 1 is substantially opaque to radiation at the X-ray frequency, and the front surface 3 of the case 1 is substantially transparent. .

Reference numeral 2 represents an X-ray beam to be detected, which enters from the direction shown in FIG. In case 1,
Usually, a large number of signal electrodes and common electrodes are arranged. Generally, this signal electrode and common electrode are
Since planar plate-like electrodes are used, the signal electrode and common electrode are sometimes referred to as a signal electrode plate or a common electrode plate hereinafter. The signal electrode plates and the common electrode plates are alternately arranged at approximately equal intervals. As a result, the space sandwiched between each signal electrode plate and each common electrode plate constitutes an X-ray detection compartment. Each common electrode is connected to a common potential (usually ground potential),
Further, a DC voltage V ₁ (not shown) is applied between each signal electrode and the common electrode.

When X-rays pass through the front section 3 of the X-ray detector as described above and enter each detection compartment, the X-rays interact with atoms of the X-ray detection gas to generate electron-ion pairs. Electron-ion pairs flow along the electric field,
A current flow is caused between the signal electrode and the common electrode. The value of this generated current corresponds to the incident X-ray energy, so by measuring the current flowing through the lead wires connected to each signal electrode, it is possible to measure the incident X-ray energy for each detection compartment. can.

Therefore, it is necessary to lead the lead wires connected to each signal electrode to the outside of case 1.
The inside is filled with X-ray detection gas, and the lead wire must be taken out from the case 1 in a sealed manner. Therefore, in the past, electrical patterns provided on a printed board were used as lead wires, and signals from the signal electrodes were taken out through the printed board. This printed board is 4 in Figure 1.
Indicated by Then, a connector 5 was connected to each pattern of this printed board 4, and a signal was transmitted to a data processing device 6.

FIG. 2 is a diagram showing an electric circuit around the detector described above. In FIG. 2, I ₁ to I _o equivalently represent the signal currents output from the signal electrodes of each channel. C ₁ to _{C o} are capacitors provided for each channel and converting each signal current into a voltage. S ₁ to _{S o} are each capacitor
This is a multiplexer that selectively selects voltages from C ₁ to _Co. Sr is a reset switch that discharges the charges stored in each of the capacitors C ₁ to _Co.
D is a driver, and this driver D is divided into a decoding function section _D2 and a driver section _D1 . AMP is an amplifier, H is an A/D converter, and M is a sequencer.

The circuit operation of FIG. 2 will be described below. The X-rays that have passed through the object enter each detection compartment of the X-ray detector,
Therefore, currents I ₁ to I _o corresponding to the incident X-ray energy are output for each channel (each detection compartment). Each of these signal currents I ₁ to I _o is connected to a capacitor C ₁
~C _o , where it is converted into a voltage signal and held.
In this state, the digital signal from the sequencer M (specifically, one of the multiplexers S ₁ to S _o
A signal for selecting one of the multiplexers is sent to the driver D, and the multiplexer instructed by the sequencer M is turned on via the decoding function section _D2 and the driver section _D1 . For example, in Figure 2, the switch
_S2 is turned on, and the second channel signal is read out and converted into a digital value through the amplifier AMP and the A/D converter H. Although the destination of this digital signal is not shown in FIG. 2, it is stored in the memory section of the X-ray CT apparatus.

Thereafter, by similar operations, the charge voltage of the capacitor of each channel is stored one after another in the memory section as X-ray detection data.

In the conventional X-ray detector as described above, the part surrounded by the dashed line A in Fig. 2 is
It was housed in case 1, and the others were provided outside case 1.

Normally, the number of channels of the X-ray detector used in an X-ray CT device is 500 or more, and the signal current
I ₁ to I _o are also very weak current values.

Therefore, the X-ray detector configured as shown in FIG. 1 has the following drawbacks.

(a) Since there are a large number of lead wires to be taken out from the case 1, special consideration is required in manufacturing to take them out in a sealed manner, which is not preferable.

(b) In order to protect the weak signal current from external noise, it is necessary to shield the signal lead wires, but since there are many lead wires taken out from the case 1, complete shielding cannot be performed.

(c) In FIG. 1, only two connectors 5 are depicted and the others are omitted, but an actual X-ray detector requires a large number of connectors.

The present invention aims to provide an X-ray detector that eliminates the above-mentioned drawbacks.

The X-ray detector of the present invention has at least a capacitor
The device is characterized in that C ₁ to _{C o} , multiplexers S ₁ to _{S o} , and a driver D are housed in a case 1.

FIG. 3 is a sectional view of the X-ray detector according to the present invention, taken along line PP in FIG. Further, double line B in FIG. 2 represents the case of the X-ray detector according to the present invention.

Hereinafter, the present invention will be explained with reference to FIGS. 2 and 3. As is clear from FIG. 2, the structure of the electric circuit of the present invention is the same as that of the conventional one. The difference is in terms of assembly and configuration, as described above, in that the capacitors C ₁ to _Co , the multiplexers S ₁ to _{S o} , and the driver D are housed in the case 1. Therefore, the number of lead wires connecting the inside and outside of the case 1 is only _l1 and _l2 shown in FIG. 2, and the number of lead wires is drastically reduced compared to the conventional means.

FIG. 3 is a sectional view of the X-ray detector according to the present invention. In the figure, 1a and 1b constitute a case of an X-ray detector, in which an X-ray detection gas 12 is sealed. Reference numeral 2 denotes incident X-rays, which enter from the front part of 3. 7 is a signal electrode plate or a common electrode plate. These electrode plates are held by flat plates 13 and 14 and form a detection chamber as described above. 4a is a printed board, on which a capacitor C, an integrated circuit G, etc. are installed. The capacitor C shown in FIG. 3 corresponds to the capacitors C ₁ -C _o in FIG. 2, and the integrated circuit G shown in FIG. 3 corresponds to the multiplexers S ₁ -S _o and the driver D in FIG. 2. Printed board 4a has screw 8
is fixed to the flat plate 13, and the signal is transmitted to the bush 11.
is led out of the case via. of course,
Portion 10 where the bush 11 is attached to the case
is sealed to prevent the X-ray detection gas 12 from leaking. Note that each signal electrode is connected to a lead wire 9.
It is connected to each capacitor on the printed board 4a via.

In the explanation of FIGS. 2 and 3, the capacitors C ₁ to C _o , the multiplexers S ₁ to _{S o} , and the driver D have been described as being housed in the case, but in addition to the above, for example, The present invention also works even if the reset switch Sr and amplifier AMP shown in FIG. 2 are housed in a case.

As described above, according to the present invention, all of the drawbacks (a) to (c) of the conventional means can be solved, and the lead wires connecting the inside and outside of the case can also be replaced with _l1 and _l2 . Since the amount is small, shielded wires can be used for these lead wires. As a result of the above, it is possible to reduce the number of wiring steps and to realize an X-ray detector that is not affected by external noise.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the appearance of a conventional X-ray detector and signal extraction means, Figure 2 is a diagram showing the X-ray detector and its surrounding electric circuit, and Figure 3 is an X-ray detector according to the present invention. A cross-sectional view of a line detector. I ₁ - I _o ... Signal current, C ₁ - _Co ... Capacitor, S ₁ - S _o ... Multiplexer, D ... Driver, M ... Sequencer, Sr ... Reset switch, AMP ... Amplifier, H ...A/D converter, 7
...electrode plate, 4a...printed board, C...capacitor, G...integrated circuit, 11...button, 12
...X-ray detection gas.

Claims (1)

[Claim for Utility Model Registration] Comprising a case filled with X-ray detection gas and a plurality of signal electrodes and common electrodes provided within the case, X-ray energy incident inside the case is transmitted to each signal electrode. In a multi-channel X-ray detector configured to detect based on flowing current, a capacitor provided for each channel converts the current flowing through the signal electrode into a voltage, a multiplexer that selectively selects the voltage of each capacitor, a driver having a decoding function for driving the multiplexer, at least each of the capacitors, the multiplexer, and the driver are housed in the case, and a lead wire connecting the inside and outside of the case is based on the output of the multiplexer. An X-ray detector comprising a signal line _L1 and a signal line _L2 added to the driver.