JPS61268235A - Inferior area discrimination circuit of x-ray ct 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 determines malfunction locations in a detection circuit system from an X-ray detector of an X1IACT device to a front-stage circuit (usually an interface circuit) of an image processing device. The present invention relates to a circuit for identifying defective parts.

[Background of the invention]

Conventionally, in this type of circuit, a check signal consisting of a voltage signal of a predetermined level is inputted to the input terminal of a preamplifier that receives signals from a large number of detection elements (channels) that constitute an X-ray detector. There was a method in which the defective location was determined based on the output signal of the detection circuit system.

However, in such conventional circuits, the quality of the channel signal amplification section from each detection element of the X-ray detector to the preamplifier is determined on the premise that all parts of the detection circuit system after the preamplifier are normal. It was only possible to judge.

Therefore, if the above assumption does not hold, it is only possible to determine that some part of the entire circuit system of a particular channel in the detection circuit system to which the check signal is input is defective, and which part ( It was not possible to determine whether the circuit was defective or not.

[Purpose of the invention]

The present invention has been made in view of the actual situation described above, and provides a defective location determination circuit for an X-ray CT device that can more specifically determine which location in the detection circuit system is defective. The purpose is to

[Summary of the invention]

In an X-ray CT apparatus, the circuit of the present invention includes a first switch that selectively connects the input terminal of the preamplifier to either the output terminal side of the X-ray detector or the ground side, and a circuit in the detection circuit system after the circuit at the next stage of the preamplifier. A second switch that selectively connects the input end of a desired circuit among the input circuits of the circuit and image processing device to either the output end of the preceding stage circuit or the check signal supply end; and a check that outputs a check signal to the check signal supply end. A signal generating circuit is provided, and the first. While switching the second switches individually in a predetermined order, the input signals to the image processing device at that time are used to sequentially judge whether the operating state of the circuits forming the detection circuit system is good or bad. Defective area (
circuits).

[Embodiments of the invention]

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

Figure 1 shows an X to which the defective location discrimination circuit according to the present invention is applied.
FIG. 1 is a block diagram showing an example of a line CT apparatus.

In FIG. 1, 1 is a preamplifier, 2 is a buffer circuit, 3 is an A/D conversion circuit (hereinafter abbreviated as ADC),
4 is a data holding circuit, 5 is an interface circuit, 6 is a control circuit, and 7 is an image processing device, which constitute an X-ray CT apparatus.

In this case, a large number (576 in this case) of detection elements constituting an X-ray detector (not shown) is divided into a plurality of (36 in this case) detection element groups, and one detection element corresponds to each group. Preamplifiers 1 are provided. Each preamplifier 1 has an amplifier circuit that amplifies the signals from the detection elements constituting the assigned detection element group, and the signals from the amplifier circuits are sequentially selected and output in response to the channel switching signal. Also, regarding the preamplifier 1 mutually,
Output signals from sequentially selected preamplifiers 1 are input to a buffer circuit 2. This results in
The first X-ray detector for one X-ray exposure (for one angle)
From the th detection element (channel) to the final (576th
The detection signals are sequentially amplified and sent to the buffer circuit 2 over the (th) detection element (channel). The buffer circuit 2 performs arbitrary amplification according to the output signal from each preamplifier 1, and makes the output range of the preamplifier 1 correspond to the input range of the ADC 3. ADC3 converts the signal (analog signal) from buffer circuit 2 into a digital signal,
The data holding circuit 4 holds the signal for a certain period of time. The interface circuit 5 inputs the signal from the data holding circuit 4 to the image processing device 7, and the image processing device 7 reconstructs the image based on the input signal and transfers the signal to the CRT (not shown).
Display the CT image. During this time, the control circuit 6 controls the detection circuit system from the preamplifier 1 to the interface circuit 5.

FIG. 2 is an operation timing chart of the above-mentioned CT apparatus, (
A) is a measurement start signal from the image processing device 7. This signal causes the control circuit 6 to operate, and a measurement sequence for one angle is executed. The number of pulses of this measurement start signal is 20 in one scan in a normal X-ray CT device.
The number is 0 to 1200.

(b) is the X-ray exposure signal, and (c) is after the X-ray exposure, the channels of the amplifier circuit output signal of preamplifier 1 are sequentially turned off.'
This is a channel switching signal (pulse train) for switching.

In response to this channel switching signal, each channel (1 to 16 channels) in each preamplifier 1 is switched and
Changing the selection switch of 36 preamplifiers 1, A'D
A/D conversion of C3, switching of data retention of data retention circuit 4, data transfer to image processing device 7, etc. are controlled. When the data transfer for all channels (576) of the preamplifier 1 is completed, the control circuit 6 waits for a large angle measurement start signal, and repeats this for a predetermined angle, 6000 minutes in this case, to complete one scan. After that, the image processing device 7 reconstructs the image and displays the CT image on the display device.

The above is similar to a conventional X-ray CT apparatus, and the circuit of the present invention is obtained by adding the following configuration to such an X-ray CT apparatus. That is, the circuit of the present invention.

A plurality of circuits forming the detection circuit system (circuits from preamplifier 1 to interface circuit 5) and image processing device 7
Among the input circuits of A switch SW for discrimination is provided. In this case, the switch (first switch) SWI provided at the input end of each preamplifier 1 is
The input end of the X-ray detector is selectively connected to either the output end (a contact side) or the ground side (b contact side) of the respectively assigned detection element of the X-ray detector. Also, other circuits 2 to 5 and image processing device 7
The switches (second switches) SW2a to SW2e provided at the input ends of the input circuits connect their input ends to the output ends (A contact side) of the preceding stage circuits 1 to 5 and the check signal supply end (B contact side). (side).

8 is an analog check signal generation circuit, which is connected to the reference power supply and D/
Any voltage can be generated using an A converter (not shown), the output end of which is connected to the b contacts of the switches 5W2a and 5W2b. 9 is a digital check signal generation circuit, and a pattern code corresponding to the number of output bits of the ADC 3, for example, o when the output bits of the ADC 3 is 4 bits.

It generates a digital signal with a code such as 00→1010→0101→1111, and its output end is connected to the b contact of the switch SW2cmSW2e.

Note that these check signal generation circuits 8 and 9 are controlled by the control circuit 6, and the check signal values are changed once or several times, here several times in response to X-ray exposure. Therefore, for example, it is changed corresponding to several signals a or b in FIG. Reference numeral 10 denotes a switch changeover circuit, which controls timing by the above-mentioned signal a or b.
The control circuit 6 controls the switches SWI and SW2a.
= S W 2 e are individually switched to the b contact side in a predetermined order, from the switch SWI on the left side in the drawing to the switch S W 2 e on the right side. in this case,
Switch to activate, e.g. SWI (or 5W2a)
Other switches except for SW2a~5W2e, such as SW2a~5W2e
(or S 'W 1, S W 2b" S W 2
e) is connected to the a contact side. Note that the image processing device 7
Here, the switch SW1, 5W2a"5W2e is also used as a determining means for determining whether the operating state of the circuits 1 to 5 constituting the detection circuit system is good or bad based on the input signal when the switch SW1, 5W2a"5W2e is switched.

Next, the operation of the above-mentioned circuit of the present invention will be explained.

First, a control signal is output from, for example, the image processing device 7 to notify that measurement for determining a defective location will be performed, and the circuits 8 to 10 are placed in a standby state.

The measurement start signal a, the X-ray exposure signal S, the channel switching signal C, and the like are output in the same manner as in the normal measurement described above.

From this state, first perform the first foot movement I. This action I
is all switches SWI as shown.

5W2a=SW2e is connected to the a contact side, that is, the measurement is performed for several angles in the same state as in normal measurement. The measured data ID is determined by comparing the data of each channel (ah) to see if it is within the range of the average data value of all channels plus the tolerance of preamplifier 1. ,
When the measured data is not within the above range, it is determined that the detection circuit system of that channel is defective.

The second foot movement ■ measures the next few angles using the switch SWI.
This is done by switching and connecting only the B contact. Since this b contact is grounded, in this case, the offset voltage of preamplifier 1 will be measured, so the measurement data nD
A predetermined threshold value is set as a determination criterion, and the data of each channel is compared to see if it is larger than the threshold value, and if it is larger, it is determined that the channel is defective (the detection circuit system of that channel is defective).

The third judgment operation ■ measures several angles of the first order.
W 2 This is performed by switching and connecting only a to the b contact.

In this case, the data value of the measurement data llID is compared to see if it is a value determined by the gain constant of the buffer circuit 2, and if it is not, it is determined that the detection circuit system after this buffer circuit 2 is defective. do.

The 4th normal operation ■ measures the primary angle with switch 5W2.
This is done by switching and connecting only the b contact to the b contact.

As a result, if measurement data IVD with a value corresponding to the check signal input to the ADC3 cannot be obtained, this ADC3
The subsequent detection circuit system is determined to be defective.

The fifth foot movement V (Vl to V3) measures the next several angles by switching 5W2c (in the case of Vl) - +5W2d (in the case of V2) → 5W2e (in the case of V3) every time one to several angles are measured.
) and each contact is switched and connected in turn.

In this case, the pattern code signal from the digital check signal generator 9 will be sequentially input to the circuits 4 and 5 and the input circuit of the image processing device 7, and the measurement data VD (VDI to VD3) at that time will An output determination is made for each bit of each circuit. If the measurement data VD1 to VD3 for each focus of each circuit is not a value corresponding to the pattern code signal, the detection circuit system after circuit 4 or 5 (in the case of circuit 5, that circuit 5) is determined to be defective. It will be judged.

Based on the above determination results, the defective location (circuit) is determined as follows. In other words, if the product is determined to be defective in the determination operations 1 or 2, but not determined to be defective in the determination operations 1 to 2,
It is determined that the corresponding channel of the preamplifier 1 is defective, and the other circuits 2 to 5 are normal. Next, if it is determined to be defective in the judgment operations ■ to ■ and not judged to be defective in the judgment operations IV and V, the buffer circuit 2 and/or the preamplifier 1 are defective, and the other circuits 3 to 5 are normal. It is determined that there is. In addition, it is determined to be defective in judgment operations I to ■,
Judgment operation ■If it is not judged as defective in 1, ADC3
, the buffer circuit 2, and the preamplifier 1 are determined to be defective, and the other circuits 4 and 5 are determined to be normal. Hereinafter, if it is determined to be defective in the judgment operation ■ to (n-1) and not judged to be defective in the judgment operation n, the switch SW2 is switched and connected to the b contact at the time of the judgment operation n.
It is determined that at least one of the circuits at the earlier stage is defective, and the circuit at the later stage is normal. and,
If these determination results are comprehensively judged, it becomes possible to specifically determine which location (circuit) in the detection circuit system is defective.

Note that such determination of defective locations can be performed artificially based on the measurement data obtained in the determination operations 1 to 2, but it may also be performed by the image processing device 7, and the determination results can be further processed. The information may be displayed on the CRT.

FIG. 3 is a diagram showing an example of the arrangement of measurement data obtained by the above-mentioned determination operations I to (2). In this figure 3,
Since measurement data from each determination operation is sequentially lined up in the Ch (channel) direction and the θ (X-ray exposure angle) direction, by sequentially determining whether each data value is a predetermined value. It is possible to identify the defective location, for example, C as shown above.
All you have to do is display it on RT.

In the above-described embodiment, a case has been described in which five determination operations 1 to 3 are performed in one scan, but one determination operation may be performed in one scan.

〔Effect of the invention〕

As described above, according to the present invention, in an X-ray CT apparatus, it is possible to more specifically determine which location in the detection circuit is defective compared to the conventional circuit.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of an X-ray CT device to which the present invention is applied, FIG. 2 is an operation timing chart of the device, and FIG. 3 is an array of measurement data obtained by judgment operations by the circuit of the present invention. It is a figure showing an example. 1...Preamplifier, 2...Buffer circuit, 3...
ADC54...data holding circuit, 5...interface circuit, 6...control circuit, 7...image processing device, 8...analog check signal generation circuit, 9...digital check signal generation circuit, 10... Switch switching circuit, SW 1-... First switch, 5W2a=SW
2a-Second switch.

Claims (1)

[Claims] Signals from a large number of detection elements constituting an X-ray detector are sequentially amplified and output by multiple preamplifiers, and are sent to an image processing device via a detection circuit system after the preamplifier stage circuit, and then sent to an image processing device.
In an X-ray CT apparatus for obtaining an image, a first switch selectively connects the input end of each of the preamplifiers to either the output end of the X-ray detector or the ground side, and a detection circuit subsequent to the next-stage circuit of the preamplifier. a second switch for selectively connecting an input terminal of a desired circuit among a plurality of circuits constituting the system and an input circuit of the image processing device to either the output terminal of the preceding stage circuit or the check signal supply terminal; and the check signal supply terminal. a check signal generating circuit that outputs a check signal to one terminal; a switch switching circuit that individually switches the first and second switches in a predetermined order; and determining means for determining whether the operating state of the circuit constituting the detection circuit system is good or bad based on the input signal to the image processing device when the image processing device is switched to one side and the other side, respectively. Defective location determination circuit for CT equipment.