JPS5878650A - Permeated x-ray detecting apparatus of 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] The present invention relates to a transmission X-ray detection device for a CT apparatus.

The transmitted X-ray detection device of the CT apparatus has the function of taking in transmitted X-rays, detecting them, performing waveform shaping processing, AD modification processing, and outputting AD conversion output to a computer. In order to shorten the processing time from capturing transmitted X-rays to AD conversion output,
In order to shorten the time for image reconstruction processing, it is possible to provide a plurality of (for example, six) X-ray detectors for detecting transmitted X-rays. In this method, the plurality of detectors described above are
They are divided into two groups, and each group is provided with a preprocessing system consisting of a dedicated amplifier and an AD converter, and the AD conversion output is output from the AD conversion means to a computer. However, there is an imbalance in the performance of the amplifiers for each group.1. If there is an unbalance in the performance of each AD converter, a harmful difference will appear in the outputs of the two groups, resulting in disadvantages such as lowering the accuracy of image reconstruction and generating ring artifacts.

An object of the present invention is to make it possible to eliminate the influence of unbalanced performance of the preprocessing system composed of amplifiers and AD converters for each group, and to achieve 90T.
An object of the present invention is to provide a transmission X-ray detection device.

The gist of the present invention is to input the output from the same detector into the preprocessing system for each group, to input the respective outputs of the preprocessing system for each group into a computer, and to communicate between the preprocessing systems. Find the error value. The error value is reflected in subsequent actual OCT data as a correction value. This eliminates errors caused by imbalance in the preprocessing system. Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the present invention. OXX-ray detector group ib The detector group 1 is divided into two groups from a plurality of X-ray detectors. The number of X-ray detectors is, for example, 6 or 32.
Each item is divided into two parts. On the output side of each group, there are integrating circuits PAII to PA1n l corresponding to each detector, and a switch 81.
1-8in.

The X-ray detector, integrating circuit, and switch that correspond to each other constitute one detector system. 2A and 2B indicate an integrating circuit group for each group, and 3A and 3B indicate a switch group for each group.

The outputs of the switches Stt to sln are connected in common and input to the first group preprocessing system 4A. The outputs of the switches 5al-sun are commonly connected and input to the second group preprocessing system 4B. The preprocessing system 4A is composed of an amplifier 41 and an AD converter 51, and the preprocessing system 4B is an amplifier. 42 and an AD converter 52. The computer 6 takes in the AD conversion outputs of the preprocessing systems 4A and 4B in a time-sharing manner and performs image reconstruction processing.

The integration circuit PAm is an integration circuit provided for detecting errors in the preprocessing system, and the 0 switch am, which receives the detection signal from the X-ray detector for detecting errors in the preprocessing system and performs integration, is the integration circuit P.
The switch Sm+1, which is a transmission selection switch for transmitting the output of Am to the first preprocessing system 4A, is an integral circuit PAm.
This is a transmission selection switch for transmitting the output of 1 to the second preprocessing system 4B.

In addition to image reconstruction processing by importing OCT data from the preprocessing systems 4A and 4B, the computer 6 also processes error detection data from the preprocessing systems 4A and 4B at the time of error detection, and processes the imported error detection. Error and correction value calculation processing based on the data for processing, processing for storing the calculated correction value in memory, reading out the correction value stored in the memory, and preprocessing system 4A.
, 4B has a preprocessing zologram that performs processing to correct OCT data.

Next, in the sixth embodiment, the operation of which will be explained, there is a subject inspection mode for obtaining actual OCT data and an error detection mode for the preprocessing system. The object testing mode is the main operation mode, and the error detection mode of the preprocessing system is operated prior to the object testing mode. It is also possible that the error detection mode of the preprocessing system is operated during the object testing mode. First of all,
The operation in the analyte calibration mode will be explained.

This embodiment can be applied to either the R-R method or the T-R method, and the emitted X-rays are fan-shaped X-rays, and the fan-shaped
Ray transmission fan-shaped X-rays are detected by all the detectors constituting the detector group 1. Each integrating circuit PA1. ~PA,n integrates the detection signal from the corresponding detector detected within the exposure time. After the exposure is completed, it is ~Sin at the time,
Turn on in splits. This time-sharing ON operation of the switches Stt to S and H is performed for the purpose of performing simultaneous preprocessing in the two preprocessing systems 4A and 4B and shortening the preprocessing time. Specifically, n sections are set, and in the first section, all and 811 are turned on at the same time, and in the next section, SXS is turned on.
and 822 are turned on at the same time...S in the last section! Turn on n, S, and n at the same time. In each section, the integrated value of the integrating circuit PA connected to the corresponding switch that is turned on is sent to the preprocessing systems 4A and 4B.

In pre-treatment systems 4A and 4B, amplification is performed using amplifiers 41 and 42, and A
AD conversion is performed by D converters 51 and 52. AD converter 51.
52 transfers the AD conversion output to calculation 86 in a time-division manner.

Specifically, first, the output of the AD converter 51, and then the output of A
The output from D Converter Co., Ltd. will be used in this order. Since this transfer requires some transfer time, the AD converters 51 and 52 perform data latching for an amount corresponding to the time required for the transfer. In order to shorten this period, the switch of the next rank is turned on when the above-mentioned latch is completed. As a result, the time from the latch to the completion of the transfer can be used as the on time for the next switch, so the time from X@ exposure to CT7'' - evening input to computer 6 can be shortened. By capturing the integral values of circuits PAo to PA2n as CT data, the capture of CT data accompanying one exposure is completed.A similar procedure is performed for the second exposure.Hereinafter, several times of exposure will be performed. After the exposure and accompanying CT data have been taken in, the computer 6 performs an image reconstruction operation after waiting for the completion of the data taking required to obtain the tomographic image.

Next, the operation of the preprocessing system in the error detection mode will be explained.

Amplifiers 41 and 42 of the preprocessing systems 4A and 4B are used as Keff for AD conversion level calibration. For example, when the emitted X-rays are not attenuated, that is, they do not pass through the subject and directly enter the single-ray detector, the product is the integrated maximum output value Vm of the line circuit PA.
aX is approximately Vmax=5 to 10 (V). -The minimum integrated output value Vmin obtained from the integrating circuit PA when X-rays that have been attenuated by passing through a cross section of the subject, for example, the waist circumference, enter the X-ray detector is Vmln = 0.2.
~0.3 mV. On the other hand, the AD converter 51,
52 has a voltage level sufficient to convert, for example, +
It is set to 10V. Therefore, the dynes of amplifiers 41 and 42 are set to fall within this conversion level. For example, the gain G is set to G=1 to 4◇ Ideally, the gains of the amplifiers 41 and 42 are the same, but the gain may vary depending on the temperature, usage time, years of usage, etc. causes fluctuations in Gui/fluctuation becomes an error in CT data. The error in the preprocessing system is mainly caused by the amplifier 41.
42 of the above gain variations. In addition, A
There may be an operational error in the D converters 51 and 52.

In the error detection mode, the switch 811 during the detection period
ゞ8sn * Fk1''Sin is all turned off, and only the switch Sm e Sm+1 is turned on. First, without irradiating X@, the computer 6 extracts the outputs a and b of the preprocessing systems 4A and 4B in a time-sharing manner. Next, X-rays are irradiated, and the transmitted X-rays in an unattenuated state (there is no attenuating object such as a subject in the measurement space) are detected by the detection compatible with the integrating circuit PArn.This detected value is It is integrated by the integrating circuit PAm and inputted to the preprocessing systems 4A and 4B via the switch Sm + Sm+1 which is turned on.The preprocessing system 4 obtained in this way
The computer 6 takes in the outputs A and B of A and 4B in a time-sharing manner.

The computer 6 calculates the difference between the outputs of the preprocessing systems 4A and 4B (A-a
), □n-b). This difference is the amount of power increased by the intensity of the x-rays. It is assumed that both pretreatment systems 4A and 4B have a constant guin regardless of the magnitude of the X-ray dose.
, 4B's output Ar, Br on the vertical axis and the X-ray dose on the horizontal axis, the pretreatment system 4A.

The outputs Ar and Br of 4B have characteristics as shown in FIG.

Next, as shown in Fig. 3, with (A-a) as a reference, (A
Find the deviation Δ between -a) and (B-b).

Δ-(A-a)-(B-b)・・・・・・・・・(
1) Next, find the ratio M between (A-a) and Δ.

A -11A-& This M is a correction coefficient. If there is no difference in gain between preprocessing systems 4A and 4B, if (B - b ) > (A - a), then M (0), if (B - b) < (A - a), then M
) becomes 0. The correction coefficient M thus obtained is latched in a register and used for correcting CT data.

The CT data is stored in the computer 6' during the above-mentioned object examination mode.
This is the value taken into . Now, when the preprocessing system 4AOCT data output is (Am-a) and the preprocessing system 4BOCT data output is (Bm-b), the gain correction is
This is done for the output of B (nmb). The calculation formula is as follows.

C=(Bm-b)+M(Am-a)-(3)
Here, C is corrected CT data obtained by correcting the output of the preprocessing system 4B.

Let's show it with a numerical example. For example, at the time of calculating the above correction coefficient, (B-b) and (A-a) are (B = b
) = 2 (A −a )−−・−・−・(4), then what is the correction coefficient?

-bA-a=-1... (5) It becomes. Therefore, the correction value C in equation (3) is C=(Bm−
b) −(Am−a) −−−−−・−・(6). Here, assuming that the gain of 4H in the preprocessing system 4 is constant regardless of the magnitude of the input signal (X-ray dose) as shown in Fig. 2, (Bm - b) = 2 (Am -'') -・Song (7) and equation (6) are C= Am -a...
For... (8). The CT7J-taC after this correction was the same as the output of the preprocessing system 4A, and the influence of the difference in gain could be corrected.

Expressed in simple numbers, (B - b ) = addition, (A - a
)=10, then according to equation (2), M=-1. When the incident intensity of the next KX-ray becomes poor, (Bm-b)=IO,
(Am-a): 5, resulting in a difference in output. When this value is substituted into equation (3), C=5, and the numbers used to calculate cT are the same.

Next, if the gain of the preprocessing system changes depending on the magnitude of the input signal (X-ray dose), when calculating the correction coefficient M, divide the range of the input signal, calculate M within each division, and calculate ( 3) Perform correction by 2.

FIG. 4 shows an explanatory diagram for determining correction coefficients consisting of 4 sections and 9 sections. In the figure, Al+A11A81A4 is the pretreatment system 4A.
The output of Bl + 82 m BS + B4 is the output of the preprocessing system 4B. The number after correction within each category M, , M,
.

M, , M4 are as follows. Based on this correction coefficient, the correction calculation of equation (3) is performed to obtain the correction value c, +C! Find +C3pc4.

According to the present invention described above, by correcting the difference in gain of the preprocessing system, it is possible to sufficiently ignore the gain difference (forward direction, error detection
The line detector, error detection integration circuit, and error detection switch may also be used for object detection, or
It may be provided independently for error detection.

[Brief explanation of drawings]

FIG. 1 is an embodiment of the present invention, FIGS. 2 and 3 are explanatory diagrams thereof, and FIG. 4 is a diagram illustrating another embodiment. 1...X-ray detector group, 2A, 2B...integrator circuit group,
3A, 3B... Switch group, 4A, 4B... Preprocessing system, 6... Computer, PAII ~ PA2n, PA
m-integrator circuit, all~Ban*Bm, Sm-
)-t-switch. Patent applicant Hitachi Medeico Co., Ltd. Agent Patent attorney Tadashi Akimoto Younger brother 1 Figure

Claims (1)

[Scope of Claims] 1. A plurality of X-ray detector system groups constituted by a plurality of CT X-ray detector systems as one group, and a plurality of X-ray detectors constituting each X-ray detector group. X1, which is commonly provided for the system
It consists of a preprocessing system for each m-detector group and a computer that takes in the output of the preprocessing system in a time-sharing manner. The output of the X-ray detector system without irradiation and the output of the X-ray detector system with transmitted X-rays without attenuation when X-rays are irradiated from the X-ray source and the subject is not placed on the measurement space are input, and the output is obtained by the inputs. A CT configured by inputting the output of each preprocessing system into the computer and setting it as correction data based on the gain difference of the preprocessing system.
The device's transmission X-ray detection device. 2. The detector system includes an X-ray detector, an integrating circuit that integrates the output of the detector, and a switch that selectively outputs the output of the integrating circuit, and the preprocessing system includes the A transmission X-ray detection device for an OCT apparatus according to claim 1, comprising an amplifier that receives an output and is used for AD conversion level calibration, and an AD converter that converts the output of the amplifier into an AD converter. .