JPS62231628A - X-ray tomographic imaging 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 (Industrial Field of Application) The present invention is directed to XII? The present invention relates to an Fi layer field imaging device.

(Prior Art) An X-ray tomographic imaging apparatus is a device that performs tomographic imaging of an affected area using X-rays. FIG. 4 shows a schematic configuration of the xmi layer imaging device. In the figure, 1 is an X-ray for performing X-ray tomography.
An xei tube that emits radiation, and the emitted X-rays are sent to collimator 2
The object 3 is irradiated in a fan-shaped manner. Reference numeral 4 denotes an X-ray detector that converts the X-rays that have passed through the subject 3 and entered into an electrical signal proportional to the energy of the X-rays. There are several types of xII detectors, but the N11 box detector 4 shown in Figure 5
has an ionization chamber filled with a gas such as Xe, which has a high X-ray absorption rate, at high pressure, and as shown in the figure, channel 5
is formed in the space between the two bias electrodes 6 in the ionization chamber, and when a positive high voltage is applied to the bias electrode 6, the ionization of the Xe gas caused by the incident X-rays from the direction of the arrow in FIG. X-ray intensity is detected by obtaining an ion current from the signal electrode 7.

(Problem to be Solved by the Invention) In order for the output current obtained from the X-ray detector 4 to accurately reproduce the incident X-ray energy distribution regardless of changes in environmental temperature, each channel 5 must be It is necessary to maintain the same shape. However, in reality, when the environmental temperature changes, channel 5
The bias electrodes 6 forming the electrodes, the support plate (not shown) holding each electrode, and the adhesive fixing each electrode expand or contract, and the individual shapes of the chitonels 5 change.

For this reason, conventional apparatuses sometimes produce ring artifacts in tomographic images. In order to avoid this, it is necessary to keep the environmental temperature of the X-ray tomography device as constant as possible,
Conventional methods include making X-ray detectors with higher precision to reduce the temperature coefficient, conducting strict product inspections and sorting out those with little change, or keeping only the X-ray detector at a constant temperature. Although measures have been taken, these measures not only cause cost increases, but also cannot be considered as sufficient countermeasures.

The present invention has been made in view of the above points, and its purpose is to correct changes in actual measurement data of each channel caused by temperature changes at a low cost, and to perform correct X-ray cross-sectional IFi imaging. The goal is to realize a photographic device.

(Means for Solving the Problems) The present invention for solving the above problems provides an X-ray tomography 1 most visible apparatus having an X-ray detector constituted by a plurality of measurement channels. A temperature sensor is provided for measuring the sensitivity of the measurement channel, and a storage means for storing the temperature characteristic of the sensitivity of the measurement channel, and a temperature sensor for each measurement channel based on the temperature characteristic stored in the storage means and the actual measurement temperature of the temperature sensor. The present invention is characterized in that it is provided with a brightness effecting means for performing temperature correction on actually measured data.

(Function) Memorize the temperature characteristics of the sensitivity of the measurement channel in advance,
Using the temperature characteristics and the actual temperature measured by the temperature sensor,
Temperature correction is performed on the actual measurement data from the measurement chitnel.

(Example) Examples of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of a main body and a data processing section according to an embodiment of the present invention. In the figure, the same parts as in FIG. 4 are given the same reference numerals. In the figure, 8 is a reference channel (hereinafter referred to as RCh) provided in the X-ray detector 4.
It is arranged as a reference for other channels at a position where the irradiated X-rays are directly incident without passing through the subject 3, and is used to correct the intensity of the X-rays, which may constantly change during scanning.

Since it is necessary to provide a plurality of R channels 8, in this embodiment, there are six stages. 9 is a measurement channel (hereinafter referred to as ACh)
This is a temperature sensor provided for measuring the temperature of 5). The data of each channel and the temperature sensor 9 are taken into the computer 11 via a data collection unit 10 consisting of a multiplexer, an A/D converter, etc., and the computer 11 performs temperature correction processing and other preprocessing described below. It has become. In this embodiment, calculations for image reconstruction are performed by a dedicated high-speed calculation device 12. Reference numeral 13 denotes an external memory that stores data (projection data) taken into the computer 11 as is, or stores data after preprocessing and reconstruction calculation processing.

Next, a method of temperature correction will be explained with reference to FIG. 2 in conjunction with the operation of the above embodiment. FIG. 2 is a graph showing an example of the temperature characteristics of an arbitrary channel (here, the 11th channel) in Δch5.

In this figure, each symbol is defined as follows.

That is, the output at t° C. in the m-th channel of Ach5 when the subject 3 is not present is Amt.

The average value of the outputs of six Rch8 at t° C. is set as Rt. Using the average value for the output of Rch8 is as follows:
In the channel shown in Fig. 5, even if one electrode deforms and its volume changes due to a temperature change, the total volume with the adjacent channels does not change, so by calculating the average value, Rc
This is because the output of h8 remains approximately constant even with temperature changes, and the temperature coefficient is considered to be almost O. In this example, AC
As each actual measurement data of h5, in order to prevent the influence of fluctuations in the intensity of irradiation XIa, each output of ACh5 is not used as it is, but the data obtained by dividing these output data by the average value of the output of Rch8 is used. In this case, the temperature coefficient of the average value of the output of RCh8 is considered to be almost O as described above, so data is not taken every time each channel is scanned.
Although data for one temperature may be used, in this embodiment, in order to ensure greater accuracy, measurements are taken each time each channel is measured.

Subject 3's l! Prior to Li layer deposition, the temperature characteristics of Ach5 must be read, and this is done as follows. In the absence of the subject 3, the output for the X-ray input of each channel is set to an appropriate temperature range of □ij + ℃ and t2, which is outside the temperature range in which the XrA detector 4 is considered to normally change, for example.
℃, and once stored in memory, read the output of RQ118 and find its average value Rj 1 + Rtz at each temperature, and calculate the Ach at each temperature.
The output of ACh5 is divided to obtain data as shown in FIG. 3, and this is stored in the memory 13 again as actual measurement data for each channel of ACh5 at a3. Although the temperature characteristics of each channel of Δch5 are not constant, the main cause is expansion and contraction due to heat, so if we focus on one channel, it is proportional to the temperature change, and its reproducibility is good. Therefore, the temperature characteristic can be considered to be linear with respect to temperature, for example,
From the measurement results shown in the figure, one channel of ACh5 draws a temperature characteristic curve as shown in Fig.
It only stores actual measurement data for each channel at two points at 2°C. However, by reading each data at these two points, the temperature characteristics of @ degrees of Ach5 are read.

Next, the actual scanning operation of the X-ray tomography apparatus will be explained. During this scan, data is constantly collected by Δch5 and Rch8, and one scan at a certain point in time will be explained. The computer 11 first detects the temperature in degrees Celsius and Rch8. Actual measurement data from Ach5 is taken in via the data collection unit 10. Next, this temperature t and the temperature t1 of ACh5 stored in the memory 13
．． Using the actual measurement data of t2, prediction of the actual measurement data when the subject 3 is not present in all channels of Ach5 is performed. M of Ach5 now? ! Taking the eye channel as an example,
This prediction utilizes the fact that A 1llt/Rt changes linearly with respect to temperature, and the following formula %/Rt, holds true. When this formula is rearranged for 8mt/Rt, the following formula (1) is obtained, and by performing this calculation, the predicted value can be easily reduced to 1q. Based on the measured data of humidity and temperature, for example, temperature [! Actual measurement data A mt.

, /R1, the actual measurement data P A mt/ Rt obtained when the subject 3 is present (however, pAmt
is the output of m-th Ach5 when subject 3 is present)
can always be converted into data at the reference temperature t1. That is, assuming that the actual measurement data to be obtained converted into temperature t1 is P A l1ljt / Rt t, this can be obtained by the following equation.

PAllj+ / Rj I= (PAlllt/R
t ) X((Amtl /Rt t ) /
(Alnt/Rt) )... (2) The computer 11 performs the calculation according to equation (2) over all channels of △ch5, performs any necessary preprocessing, and then processes the data. Send it to the high-speed arithmetic unit 12,
An image reconstruction calculation is performed, the 1!7 image data is temporarily stored in the memory 13, and necessary data is taken out from there to display the instructed image.

As mentioned above, in this embodiment, the temperature t1° t2 is
Obtain actual measurement data that does not pass through the test object 3 of all channels at the point, and then use the actual measurement temperature by the temperature sensor 9 to determine the test data of the test object 3 of each constituent channel of Δch5 at that temperature.
The predicted value of the actual measured data when there is no AC+15 is obtained using equation (1), and based on that value, the measured data obtained from AC+15 is calculated at the reference temperature using equation (2). The data is converted to actual measurement data and temperature correction is performed.

Note that the present invention is not limited to the above embodiments. For example, in the above embodiment, the X-ray detector uses electric l! I
Although a case has been described in which an Li box-shaped detector is used, a semiconductor detector may be used in which a collimator partitioned by a tungsten plate is provided for each channel in front. Also, t
I ”C,t Using actual measurement data at 2°C (1)
Although the equation has been calculated, the data shown in the characteristic curve shown in FIG. 2 may be stored in the memory 13 over each temperature, and correction may be made by sequentially reading out the data. Also, formula (1),
It is not necessary to perform the calculations of equation (2) sequentially, and a combination of these may be used for correction. Furthermore, the average value of Rch8 output was used as the actual measurement data.
If the X-ray energy is stable, Rch8 may not be used, and the output of ACh5 may be used as it is as the actual measurement data.

(Effects of the Invention) As explained above, according to the present invention, actual measurement data can be obtained at low cost without requiring any special equipment and by using the storage means and calculation means normally included in an XSS tomography apparatus. XI that can perform temperature correction! A jlflj layer device can be realized.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a schematic configuration of the main body and processing section of an embodiment of the present invention, and Fig. 2 shows one of the measurement channels.
A diagram showing an example of the temperature characteristic curve of a channel, FIG. 3 is an explanatory diagram of actual measurement data of each channel at a temperature tl+12 stored in memory, FIG. 4 is a schematic configuration diagram of a conventional X-ray tomography apparatus, and FIG. FIG. 5 is an electrode layout diagram of the ionization chamber type detector. 1...XI! IL tube 2...collimator 3
...Object under test 4...X-ray detector 5...Measurement channel (△ah) 6...Bias electrode 7...Signal electrode 8...Reference channel (RCh) 9... Temperature sensor 10... data collection unit 11
...Computer 12...High-speed calculation device 13...
・Memory patent applicant Yokogawa Medical Systems Co., Ltd. No. 22 Negative number 3 Figure East 14 Figure rust 5) Decoy X &!

Claims (1)

[Claims] In an X-ray tomography apparatus having an X-ray detector configured with a plurality of measurement channels, a temperature sensor for measuring the temperature of the measurement channel is provided, and a storage means for storing temperature characteristics of sensitivity of the measurement channel. and a calculation means for correcting the temperature of the measured data in each measurement channel based on the temperature characteristics stored in the storage means and the temperature actually measured by the temperature sensor. .