JPH0479260B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention provides an
The present invention relates to an X-ray tomography apparatus that uses a part of a ray detector as a reference channel.

(Prior Art) An X-ray tomography device is a device that performs tomography of an affected area using X-rays. FIG. 2 shows a schematic configuration of the X-ray tomography apparatus. In the figure, 1 is an X-ray source that emits X-rays for performing X-ray tomography;
The emitted X-rays are shaped into a fan shape by a collimator 2 and irradiate the subject 3. 4 is an X-ray detector that converts the incident X-rays that have passed through the object 3 into electrical signals proportional to the energy of the X-rays; 5 is a measurement channel (hereinafter referred to as Ach) that constitutes the X-ray detector 4;
It is. In addition to Ach 5, this X-ray detector 4 is provided with a reference channel (hereinafter referred to as Rch) 6 at a position where the irradiated X-rays are directly incident without passing through the subject 3 in order to perform various corrections on the acquired data. I was being treated,
The intensity of the X-rays, which may constantly change during a scan, is measured, and changes in the measured values caused by the X-ray source among the measured values obtained at Ach5 are corrected. Ach
The data of Rch 5 and Rch 6 are taken into the computer 8 via the data collection device 7, which is composed of a multiplexer, an analog-to-digital converter (hereinafter referred to as AD converter), etc., and the computer 8 performs X-ray intensity correction processing and other processing. Pre-processing is now being performed. Calculations for image reconstruction are performed in a dedicated high-speed arithmetic unit 9. Reference numeral 10 denotes an external memory that stores data taken into the computer 8 as is, or stores data after preprocessing and reconstruction calculation processing.

(Problem to be Solved by the Invention) Conventionally, there is a difference in the timing of data acquisition for Ach5 and Rch6 due to the configuration of the data acquisition device, and it is difficult to accurately detect X-ray fluctuations that occur during measurement for each channel. It was not possible to correct it. Also, Rch
It is equipped with multiple Rch 6 and multiple AD converters in order to eliminate the individual differences in 6, and calculates the average value.
It was necessary to perform correction using it as the measured value of Rch6.

The present invention has been made in view of the above points, and its purpose is to:
The object of the present invention is to realize an X-ray tomography apparatus equipped with a data acquisition device that can accurately correct the influence of X-ray fluctuations occurring during the measurement time of the channel using one Rch.

(Means for Solving the Problems) The present invention uses a part of an X-ray detector consisting of a plurality of channels as a reference channel in order to correct temporal fluctuations in the intensity of X-rays emitted by an X-ray source. ,
In an X-ray tomography system that uses the remaining channel as a measurement channel and corrects the measurement data obtained from the measurement channel using reference data obtained from the reference channel, measurement is performed in which the output of the measurement channel of the X-ray detector is sequentially read out. a data reading means; a reference sampling means for reading out the output of the reference channel in accordance with the read cycle of each channel of the measurement data reading means; The present invention is characterized by comprising a reference data generation means for sequentially updating data.

(Function) The detection data of each Ach is integrated over a certain period of time using an integrating means, and is converted into a voltage.
Detection data alternately with voltage converted data
It is converted into a digital signal by AD conversion means.
The digitalized Rch detection data is added to the data at fixed time intervals by an adding means and input to the computer, and each Ach detection data bypasses the adding means and is corrected in the computer based on the Rch data. .

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of main parts of an embodiment of the present invention. In the figure, the same parts as in FIG. 2 are given the same reference numerals. In the figure, CH1 to CHn are each channel of Ach5, and the CHR is Rch6. 11a,1
1b,..., 11n are each channel CH1,
The current output detected by CH2,...,CHn is integrated by capacitors C1, C2,...,Cn, and the measurement data converted to voltage values is sequentially switched to the amplifier A1.
12 is the capacitor C1, C
This is a switch for grounding the capacitors C1, C2,..., Cn in order to discharge the charges stored in them. 13a, 13b, 13
c, 13d is 13 when 13a and 13c are turned on.
This is an interlocking switch consisting of four SPST switches in which 13b and 13d are turned off, and when 13b and 13d are turned on, 13a and 13c are turned off. When switch 13a and switch 13c are on, any one of the data of each channel of Ach5 is sent to AD converter 1.
4, it is converted into a digital signal and inputted to the computer 8 without going through the adder 15, and then the switch 1
When switch 3b and switch 13d are on, the data on Rch 6 is converted into a digital signal by AD converter 14, inputted to adder 15, and inputted to computer 8 after addition operation. Switches 11a to 11n, 1
2, 13a to 13d are controlled by the control circuit 16, and the AD converter 14 is controlled by the control circuit 16.
The timing of AD conversion and the timing of the addition operation of the adder 15 are also controlled by the control circuit 16.

Next, the operation of the embodiment configured as described above will be explained. X-rays emitted from the X-ray source 1 and transmitted through the subject 3 reach the X-ray detector 4, are detected at Ach5, and are output as a current signal. Rch6
In this case, X-rays that do not pass through the subject 3 are detected and output as a current signal. The detection data of CH1 to CHn of Ach5 is charged in capacitors C1 to Cn, respectively, and integrated for a predetermined time and output as a voltage signal. The voltage signal is applied to the switches 11a to 11 which are turned on and off in sequence under the control of the control circuit 16.
input to amplifier A1 by switch 13
a, and is converted into a time-series digital signal by the AD converter 14. The switch 12 is turned on while the switches 11a to 11n are turned on and off to discharge the charges in the capacitors C1 to Cn. The current signal of the measurement data of Rch6 is converted into a voltage signal by amplifier A2, and the current signal of the measurement data of Rch6 is converted to a voltage signal by amplifier A3.
The output signal is inverted and amplified at the switch 13b so that it has the same phase as the output of the amplifier A1, and is input to the switch 13b. Switch 13a is “off” and switch 13b is “on”
At this time, the output of the amplifier A3 is converted into a digital signal by the AD converter 14 according to the AD conversion timing signal of the control circuit 16, and is input to the adder 15 via the switch 13d, which is turned on at the same time as the switch 13b. . The adder 15 is, for example, CH1
The m pieces of Rch 6 data from the first to the mth Rch 6 that arrive from the time when the switch 11a is turned on until the next one is added and used as reference data for the data on CH1. When the m+1st Rch6 data is input, the first data is removed from the addition result,
The adder 15 always outputs the addition result of m pieces of Rch 6 data. The measurement data of CH1 input to the computer 8 is compared with the data of Rch6, which is obtained by adding the data of the time interval from “on” of the switch 11a inputted at the same time to the next “on”, and will be corrected. The above operation will be explained in detail with reference to the time chart shown in FIG. In the figure, A indicates the operating time of the switch 11a, B indicates the operating time of the switch 11b, and C indicates the operating time of the switch 1.
Waveform representing the operating time of 1n, D is switch 13
Waveforms a and E represent the operating time of the switch 13b, and waveform F represents the operating time of the switch 12. from the control circuit 16
The AD conversion timing signal waveform supplied to the AD converter 14 performs an operation of converting an analog signal into a digital signal at the falling edge of the pulse waveform. Chi is
The data of Rch6 is converted into a voltage signal in amplifier A2, and the output waveform of amplifier A2 whose amplitude fluctuates for each pulse.
Nu is the voltage waveform at the end of capacitor C2 charged with the current based on the measurement data of CH2, and le is capacitor Cn.
This is the end voltage waveform of . The code at the bottom is switch 11
It is attached to the rise or fall time of each pulse from the time when a becomes "on". Here, the timing of each waveform and the operation of the circuit will be explained.

Time (a) Switch 11a “on”, switch 13a
“On” capacitor C1 end voltage input to AD converter 14.

(b) The AD converter 14 performs AD conversion and measurement of CH1 according to the AD conversion timing signal.

(U) Switch 12 “on”, capacitor C1
charge discharge.

Switch 13a is "off", switch 13b is "on", and the data is input to the AD converter 114 of Rch6.

(E) The AD converter 14 performs AD conversion and measurement of Rch 6 according to the AD conversion timing signal.

(O) Switch 11a “off”, switch 11b
When the switch 12 is turned on and the switch 12 is turned off, charging of the capacitor C1 starts and the mode becomes current integration mode.

Switch 13a "on", switch 13b "off", capacitor C2 terminal voltage AD converter 1
Enter 4.

(f) The AD converter 14 performs AD conversion and measurement of CH2 according to the AD conversion timing signal.

(ki) Switch 12 “on”, capacitor C2
charge discharge.

Switch 13a is "off", switch 13b is "on", and the data of Rch6 is input to the AD converter 14.

(h) The AD converter 14 performs AD conversion and measurement of Rch 6 according to the AD conversion timing signal.

(Ke) Switch 11b “off”, switch 12
“OFF” starts charging the capacitor C2 and enters current integration mode.

Switch 13a is "on", switch 13b is "off".

(This) Switch 11n is “on”, switch 13a
“ON”, switch 13b “OFF” capacitor Cn terminal voltage input to AD converter 14.

(S) Based on the AD conversion timing signal, the AD converter 14 performs AD conversion and measures the voltage at the Cn terminal of the capacitor Cn.

(Yes) Switch 13a “off”, switch 13b
“ON” switch 12 “ON”, capacitor Cn
charge discharge.

(S) The AD converter 14 performs AD conversion and measurement of Rch 6 according to the AD conversion timing signal.

(S) (A) Repeat the following actions.

In the above explanation, the measurement data from each channel of Ach5, for example, the data collection interval of CH1, is from the start of charging of the C1 voltage at time (o) to the AD conversion timing time before discharging (so), The measurement data collection interval of switch 13b when switch 11a is "on" is
There is a slight deviation from the AD conversion timing time (e) during "on" to the same point in the next CH1 measurement (c), but this deviation is a small deviation in a large amount of data, so it is not affected by changes in X-ray intensity. Data correction has almost no effect. Similarly, the measurement data collection interval for CH2 is (ku)-(na), and the collection interval for Rch6 is (ke)-(te), which is the same deviation as CH1. Since the following is exactly the same, no special explanation will be given.

As described above, by collecting a large number of data during the time interval of collecting the measurement data of each Ach 5, the Rch 6 data can be used to obtain pure X-rays irradiated by the Data that reflects intensity fluctuations can now be collected for each Ach, making it possible to accurately correct the effects of X-ray intensity fluctuations on each Ach without increasing the number of Rchs or AD converters. It became.

Note that the present invention is not limited to the above embodiments. For example, in order to make the measurement of Rch 6 more accurate, the frequency of the conversion timing of the AD converter 14 may be increased to further increase the sampling rate. Also, switches 13a, 13b and 13c, 1
3d has been explained using interlocking switches of four SPST switches, but two sets of interlocking switches of two SPDT switches may also be used.

Alternatively, two AD converters may be used to accurately match the actual measurement time and the addition period by the adder.

(Effects of the Invention) As explained in detail above, according to the present invention,
This has a great practical effect because it becomes possible to accurately measure the temporal X-ray fluctuations that occur when collecting measurement data measured by Ach for each channel and correct the data for each channel.

[Brief explanation of drawings]

Fig. 1 is a main part configuration diagram of an embodiment of the present invention, Fig. 2
The figure is an explanatory diagram of an X-ray tomography apparatus, and FIG. 3 is a time chart of the operation of the apparatus of the present invention. 1... X-ray source, 3... Subject, 4... X-ray detector, 5
...Ach, 6...Rch, 7...Data collection device, 8...Computer, 9...Memory, 11a to 11n, 1
2, 13a to 13d...Switch, 14...AD converter, 15...Adder, 16...Control circuit, C1, C2
~Cn...Capacitor.

Claims (1)

[Claims] 1. In order to correct temporal fluctuations in the intensity of X-rays emitted by an X-ray source, a part of an X-ray detector consisting of a plurality of channels is used as a reference channel, and the rest is used as a measurement channel. In an X-ray tomography apparatus that uses reference data obtained from a reference channel to correct measurement data obtained from a measurement channel using reference data obtained from a reference channel, the measurement data reading means sequentially reads out the output of the measurement channel of the X-ray detector; Reference sampling means reads out the output of the reference channel in accordance with the read cycle of each channel of the data reading means; and Reference sampling means sequentially adds the outputs of the reference sampling means and updates the reference data corresponding to the data integration time of the measurement channel one after another. An X-ray tomography diagnostic apparatus comprising: data generation means.