JPS623684A - Detector for x-ray ct equipment - Google Patents

Abstract

PURPOSE:To stabilize measurement characteristics by providing a heating means which heats a detector to a prescribed temperature in accordance with the output of a temperature sensor provided on a prescribed position of the detector. CONSTITUTION:A preheating control circuit 7 starts the operation when a constant voltage source 32 is connected by a control signal 31 from a control part of an X-ray CT equipment; and if the temperature of the detector is different from a normal temperature, the differential voltage between the output voltage of a temperature sensor 6 and a reference voltage set by a reference voltage setter 11 is outputted from a comparator 10 and is supplied to the base of a switching transistor Tr 13 to turn on the Tr 13, and a coil 14A of a relay 14 is energized to turn on its contact 14B, and power is supplied to a heater 5 from a power source 15 to heat the detector. When the temperature of the detector is equal to the normal temperature, the differential voltage between the output voltage of the sensor 6 and the reference voltage is zero, and the Tr 13 is turned off to break the current flowed to the coil 14A of the relay 14, and the contact 14B is turned off, and power supplied to the heater 5 is broken to stop heating the detector.

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to a detector for an X-ray CT apparatus, and particularly to a detector for an X-ray CT apparatus.

The present invention relates to a technique that is effective when applied to a technique for stabilizing the temperature of a detector for an X-ray CT apparatus (hereinafter simply referred to as a detector) during use.

[Background technology]

Detectors for conventional X-ray CT apparatuses have some degree of temperature dependence in their characteristics, and some measurement errors occur due to changes in ambient temperature. For example, the output of the n channel of the detector has a temperature dependence as shown in Fig. 7, and the output of the n' channel has a temperature dependence as shown in Fig. 8. , resulting in measurement errors for the same X-ray dose for each channel of the detector. There was a problem in that the image quality of both CT images deteriorated due to this measurement error. For example, if the output of one channel changes significantly due to temperature, artifacts will appear on the screen. Also, the output of all channels varies depending on the temperature.

Image resolution and contrast are reduced. In addition, in FIGS. 7 and 8, A, B, and C are respectively appropriate temperatures T of the detector during use. , T0+ΔT, T o
−ΔT is the measurement characteristic straight line of n channel, and A
', B', and C' are the appropriate temperatures T of the detector during use, respectively. , To+ΔT',T.

It is a measurement characteristic straight line of the n' channel at -ΔT'.

As a countermeasure to this problem, temperature control to keep the detector temperature constant is considered, but the temperature control means such as temperature control accuracy is complicated and high temperature control accuracy is required.

Further, there is a problem in that there are problems such as induced noise generated by the current flowing through the temperature control heater.

[Purpose of the invention]

An object of the present invention is to provide a technique that can stabilize measurement characteristics by reducing temperature fluctuations during use of a detector with a simple structure.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

That is, in a detector for an X-ray CT device that detects X-rays transmitted through a subject, a temperature sensor is provided at a predetermined position of the detector, and heating is performed to heat the detector to a predetermined temperature according to the output of the temperature sensor. The present invention is characterized by the provision of a means for reducing temperature fluctuations during use of the detector and stabilizing measurement characteristics with a simple structure.

[Structure of the invention]

Hereinafter, the configuration of the present invention will be explained along with examples.

In addition, in all the figures for explaining the embodiments, parts having the same functions are given the same reference numerals, and the explanation of the decoration will be omitted.

First, the principle of this embodiment will be explained.

In the detector of the XI@CT device, temperature fluctuations are large from the time the XfiCT device starts being used until it reaches a steady temperature state suitable for measurement during operation, and the fluctuations after reaching the steady temperature are small. The cause of this is that when using the X41CT device,
This is because the room temperature fluctuates due to the operation of the room temperature regulator in the IACT equipment room and the heat from the X-ray CT equipment, which causes the detector temperature to fluctuate. The thermal time constant of the detector is about 30 to 90 minutes, so even if the room temperature stabilizes at a steady temperature after about 30 minutes, the detector temperature will change after about 2 to 4 hours.
It takes some time to reach a steady temperature.

Therefore, before using the X-ray CT apparatus, the detector of this embodiment
The detector is preheated to a steady state temperature (hereinafter simply referred to as steady state temperature) suitable for measurement, and the temperature is stabilized at the steady state temperature immediately after the X-ray CT apparatus is started to be used. In addition, the room temperature in a steady state is affected by temperature fluctuations such as seasonal changes, but it does not change suddenly over a few days, so the expected value of the steady state temperature when preheating the detector is The sensor temperature at the time of last use may be used.

1 and 2 are diagrams for explaining a detector of an X-ray CT apparatus according to an embodiment of the present invention, and FIG.
FIG. 2 is a perspective view showing the schematic structure of the 1iCT apparatus, and FIG. 2 is a block diagram showing the schematic structure of its detector.

In FIGS. 1 and 2, a rotary plate 1 is rotated by a drive motor (not shown). The rotary plate 1 has an X-ray tube 2 and a detector 3 facing it.
is installed. After xl emitted from the X-ray tube 2 passes through the subject, it enters the detector 3, and a signal current corresponding to the X-ray intensity is input to the subsequent signal amplifier 4.

The detector 3 is attached with a heater 5 for heating and a temperature sensor 6 for measuring temperature. Heater 5 and temperature sensor 6
is electrically connected to a preheating control circuit 7 attached to the rotating plate 1.

Next, a specific circuit configuration of one embodiment of the preheating control circuit 7 is shown in FIG.

This preheating control circuit 7 is as shown in FIG.

Temperature measurement circuit 8 consisting of temperature sensor 6 and bridge circuit
The output of the temperature measurement circuit 8 is input to one input terminal of a comparator 10 via an amplifier 9. The other input terminal of the comparator 10 is configured to receive a voltage corresponding to the steady temperature set by a reference voltage setting device 11 made of a volume or the like. Here, instead of this reference voltage setter 11, a RAM (Random Access Me
It is also possible to store the steady temperature of the mill or the previous measurement using a tool such as Mory), and use it as the reference value.

Then, a difference voltage between the voltage corresponding to the set steady temperature and the voltage corresponding to the temperature of the detector 3 is outputted from the comparator 10 and inputted to the base of the switching transistor 13 via the amplifier 12. It looks like this. A relay 14 is connected to the collector of the switching transistor 13.
The coil 14A is connected to the coil 14A. This coil 14A
When energized, contact piece 14B of relay 14 turns on (
(closed), an electric power source 15 is connected to the heater 5, and electric power is supplied to the heater 5 to cause the heater 5 to generate heat. When the detector 3 reaches a steady temperature, the switching transistor 13 is turned off and the current flowing through the coil 14A of the relay 14 is automatically cut off. The base voltage setting device 11 is manually set.

Further, a constant voltage source 32 for the temperature measurement circuit 8 and the relay 14
is supplied via the control circuit 30. In the figure, R, R2, and R3 are resistors, respectively.

The preheating control circuit 7 configured in this manner is configured such that, for example, the constant voltage source 32 is connected to the
When connected by the control unit Ji+31 from the control unit of the device, it starts operating. If there is a temperature difference between the temperature of the detector 3 and the steady temperature, the voltage difference between the output voltage of the temperature sensor 6 and the reference voltage set by the base voltage setting device 11 is output from the comparator 10. is applied to the base of the switching transistor 13, and the switching transistor 13 is applied to the base of the switching transistor 13.
is turned on (ON), the coil 14A of the relay 14 is energized, and its contact piece 14B is turned on, causing the heater 5 to receive power type g1.
Electric power is supplied from 5, and the detector 3 is heated. When the temperature of the detector 3 becomes the same as the steady temperature, the voltage difference between the output voltage of the temperature sensor 6 and the reference voltage becomes "0", and the switching transistor 13 turns off (OFF).
The current flowing through the coil 14A of No. 4 is cut off, the contact piece 14B is turned off (OFF) L, the power supplied to the heater 5 is cut off, and heating of the detector 3 is stopped.

Further, at the time when the X-ray CT apparatus starts to be used, a start-of-use control signal 31' is inputted from the control section to the control circuit 30, and the preheating control circuit 7 is disconnected from the X-ray CT apparatus, so that no current flows to the heater 5. do it like this.

As can be seen from the above explanation, according to this embodiment, stable characteristics of the detector 3 can be achieved with a simple structure even in environments where there is a large temperature difference between when it is not in use and when it is in use, such as at night. Therefore, the frequency of calibration of the sensitivity of the detection N3 can be reduced. Moreover, it is also possible to obtain a better image.

Furthermore, since the power supplied to the heater 5 is completely cut off when the X-ray CT apparatus is used, induced noise due to the current flowing through the heater 5 can be prevented. With these, a good image with good contrast and resolution can be obtained.

FIG. 4 is a circuit diagram showing a specific configuration of another embodiment of the preheating control circuit 7. In FIG.

As shown in FIG. 4, the preheating control circuit 7 of this embodiment converts the output of the amplifier 9 of the embodiment of FIG. It looks like this. counter 17
For example, a down-counting counter is used. The initial value of this counter 17 is ROM (Read 0nl).
Reference value setting memory 18 consisting of
It is set by The reference value setting memory 18 stores values corresponding to steady temperature.

The counter 17 outputs an output until the initial setting value becomes "0", and the output of the six amplifiers 12 is input to the base of the switching transistor 13.

The switching transistor 13 is turned on and off. Further, it is also possible to use a storage circuit such as a RAM as the reference value setting memory 18 to store the temperature at the time of the previous day's or previous operation of the detector, and use this as the reference value.

In this way, the same effects as in FIG. 3 can be obtained with a simple configuration using the counter 17 and the reference value setting memory 18.

FIG. 5 is a circuit diagram showing a specific configuration of another embodiment of the preheating control circuit 7. In FIG.

As shown in FIG. 5, the preheating control circuit 7 of this embodiment converts the output of the amplifier 9 of the embodiment of FIG.
Input to OM19. The ROM 19 stores a table of characteristic straight lines showing the relationship between the output of the temperature sensor and the heater heating time shown in FIG. A heater heating time signal corresponding to the temperature of the detector 3 is output from the ROM 19,
The signal is input to the timer 20. The timer 20 outputs a signal for a time corresponding to the heater heating time signal, and the amplifier 12
It is designed to be input to the base of the switching transistor 13 via. In addition, ROM19 has XIaC
A control signal 21 from the control section of the entire T device is connected.

In this way, the same effects as in FIG. 3 can be obtained with a simple configuration using the ROM 19 and the timer 2o.

Further, the temperature at the time of the previous day's or previous operation of the detector is stored using a memory circuit 19A such as a RAM, and
It is also possible to select one of the 19 tables and control its output.

As explained above using the specific embodiment of the preheating control circuit 7, the temperature of the detector 3 is detected by the temperature sensor 6 about two hours before the scheduled start time of the XICT device,
By setting the preheating control circuit 7 and supplying power to the heater 5 until the temperature of the detector 3 reaches the steady state, the temperature of the detector 3 at the start of use of the X-ray CT apparatus is always maintained at the steady temperature state 1.
It can be rubbed.

When the X@CT apparatus starts to be used, a start-of-use control signal 31' from the control section of the X-ray CT apparatus inputs to the control circuit 30 that the apparatus is in use. The control circuit 30 connects the preheating control circuit 7 to XA! & CT device, and completely prevent current from flowing through the heater 5 to prevent induction noise from occurring from the heater 5. Also, X
The control circuit 30 measures the temperature of the detector 3 4 to 6 hours after starting to use the X-ray CT apparatus, stores it in the reference value setting memory 18 or RAM, and prepares for the next time.

As can be seen from the above description, according to this embodiment, the temperature of the detector 3 can be adjusted from the time of the start of use of the X-ray CT apparatus to the steady temperature or the previous day's temperature using a simple configuration using the temperature sensor 6 and the preheating control circuit 7. Alternatively, the temperature can be set to the temperature at the time of the previous operation of the X-ray CT apparatus.

Furthermore, since no current flows through the heater 5 when the X-ray CT apparatus is in operation, induced noise from the heater 5 can be prevented.

The present invention has been specifically explained above based on examples, but
It goes without saying that the present invention is not limited to the embodiments described above, and can be modified in various ways without departing from the spirit thereof.

For example, each component of the preheating control circuit 7 may be of any type as long as it fulfills its function.

〔effect〕

As explained above, according to the present invention, the temperature of the detector can be adjusted to
The temperature can be set to a constant temperature from the time the ICT device is started to be used, or to the temperature from the previous day or the previous operation of the XwIcCT device.

Furthermore, since no current flows through the heater when the X-ray CT apparatus is in operation, induced noise from the heater can be prevented.

Furthermore, the frequency of calibration of the sensitivity of the detector can be reduced.

[Brief explanation of the drawing]

1 and 2 are diagrams for explaining a detector of an X-ray CT apparatus according to an embodiment of the present invention, and FIG.
FIG. 2 is a block diagram showing the schematic structure of the aCT device; FIGS. 3 to 5 are circuits showing specific structures of embodiments of the preheating control circuit. Figure 6 is a diagram showing the heating characteristics representing the relationship between the output of the temperature detection sensor and the heater heating time, and Figures 7 and 8 are:
FIG. 2 is a diagram for explaining problems with a conventional detector. In the figure, 3...detector, 5...heater, 6...temperature sensor, 7...preheating control circuit.

Claims (1)

[Claims] (1) In a detector for an X-ray CT device that detects X-rays transmitted through a subject, a temperature sensor is provided at a predetermined position of the detector, and the detector is heated to a predetermined temperature according to the output of the temperature sensor. A detector for an X-ray CT apparatus, characterized in that it is provided with a heating means.