JPH07250283A - Fluoroscopic image pickup device - Google Patents

Abstract

PURPOSE:To achieve dynamic offset compensation by measuring an offset value and latching it at the time of trial seeing through and image pickup in advance to performing real ones, and subtracting the offset value at the time of performing the real ones. CONSTITUTION:Just before the seeing through is started, a CPU 7 calculates and latches the average value of AD outputs provided plural times. Next, a real seeing-through activation is started, the output of an amplifier circuit 10 is provided together with X-ray irradiation, the outputs are successively A/D converted at every unit time by an A/D converter 6, and offset correction is conducted by subtracting the average value from the A/D converted outputs at every unit time. Afterwards, X-ray irradiation is conducted, and the integrated outputs of X-ray electric signals transmitted through an object during a real photographing block. Then, those integrated outputs are successively converted by the A/D converter 6 at every unit time, the offset value is subtracted every time, and offset correction is conducted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray fluoroscopic apparatus which dynamically removes the influence of changes with time.

[0002]

2. Description of the Related Art In automatic exposure control, when photographing, an X-ray is irradiated with a set photographing tube voltage and photographing tube current, the light II is detected by a light receiving element, and the signal obtained by integrating the electric signal of this output is amplified. Then, the A / D conversion is performed, and when the converted value becomes equal to a reference value corresponding to a preset proper film density, X-rays are blocked and the irradiation time is adjusted. In this case, it is necessary to always design the circuit and set the components so that an appropriate film density can be obtained.

[0003]

However, in the conventional device of this type, a dark current of a light receiving element for detecting light and converting it into an electric signal and a change with time of offset voltage of a circuit such as amplifying an electric signal are used. There is a phenomenon that the irradiation time until the electric signal value reaches the reference value changes due to a change in the electric signal value or a change in the circuit output value. Therefore, before the X-ray irradiation, an integrating circuit for integrating the electric signal is added, and the output is fed back to the input of the integrating circuit for integrating the electric signal during the X-ray irradiation to amplify the dark current and the electric signal of the light receiving element. The compensation method that cancels the offset voltage of the circuit to be used is adopted.

Further, during fluoroscopy, X-rays are radiated and an output image of II (image intensifier) is observed on a television monitor through a camera. The brightness of the TV monitor at that time is set to be appropriate. By using the method of detecting the output light of II, converting it into an electric signal, and further AD converting it, and controlling the fluoroscopic conditions such as fluoroscopic tube voltage or fluoroscopic tube current so that the converted value always becomes an appropriate reference value. There is.

Further, in this case, in the conventional device, the reference value is changed to the reference value due to the change over time in the offset voltage of the circuit such as the dark current of the light receiving element which detects light and converts it into an electric signal and the electric signal which is amplified. On the other hand, the perspective condition may change because the conversion value changes. Prior to X-ray irradiation, these electric signals are AD-converted and stored in memory, and the correction data stored in the D / A converter added for correction are D / A-converted and fed back to the amplification circuit to detect the light receiving element. A method of canceling an offset voltage such as a circuit for amplifying a dark current and an electric signal during fluoroscopy is used. In each case, each conventional example requires a special offset compensating means.

An object of the present invention is to provide an X-ray fluoroscopic imaging apparatus which enables dynamic offset compensation during fluoroscopy and radiography without using special offset compensation means.

[0007]

According to the present invention, an X-ray source, a table on which an object is mounted, a film which is excluded from transmission of X-rays from the object during fluoroscopy, and is inserted into the transmission X-ray passage during imaging. And an image intensifier that converts X-rays that have passed through the subject into light, an optical / electrical conversion unit that converts the output light of the image intensifier into an electric signal, and this electric signal is AD-converted during fluoroscopic imaging At times, an AD converter that AD-converts the integrated signal of the electric signal, a digital processing unit that sets and controls the fluoroscopic condition from the AD converted output of the electric signal, and controls the photographing time from the AD converted output of the integrated signal; A TV monitor for displaying the electric signal output of the electric signal converting means;
The digital processing means uses a measuring means for obtaining and latching an AD conversion output which is an offset output in a section where X-rays are not emitted during fluoroscopy and photographing, and real fluoroscopy with the latched AD conversion output by the fluoroscopy offset during fluoroscopy. Time A
A fluoroscopic condition is set by a correction unit that corrects the D conversion output and corrects the AD conversion output at the time of actual shooting by the latched AD conversion output due to the offset at the time of shooting and the AD conversion output after correction by this correction unit. An X-ray fluoroscopic imaging apparatus including means for performing control and imaging time control is disclosed.

[0008]

According to the present invention, during fluoroscopy and photographing, the offset value is measured and latched prior to the real fluoroscopy and the real photographing, and the offset value is measured in the real fluoroscopy and the real photographing. Achieves dynamic offset compensation by subtracting.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an embodiment of the X-ray fluoroscopic imaging apparatus of the present invention. In the figure, the X-ray controller 2 comprises a fluoroscopic / imaging condition controller 3 and an automatic exposure controller 11. The fluoroscopic / imaging condition control unit 3 controls the tube voltage, tube current, and ON / OFF of the X-ray tube including the X-ray tube and the high-voltage generating unit.

The X-rays emitted by turning on the X-ray tube pass through the subject 15 on the table and are converted into light by the II (image intensifier) 14. The output of II14 is T
An image is taken by the V camera 12, and an image is displayed on the TV monitor 13. The output of the TV camera 12 or the output of the light receiving element 16 is input to the automatic exposure control device 11.

The automatic exposure control device 11 includes an I / O port 4, an amplification circuit 10, an integration circuit 5, an AD converter 6 and a CPU.
7, RAM 8, ROM 9, and bus 20. The amplifier circuit 10 includes an operational amplifier 10A, resistors 10B, 10C, 10
D and switch 10E, switch 10E ON
Adjust the amplification by turning on / off. The integrating circuit 5 includes an operational amplifier 5A, resistors 5B and 5D, an integrating capacitor 5C, and a switch 5E, and performs a reset / integration operation by turning on / off the switch 5E.

The I / O port 4 is used for various input operations. In this figure, the switches 10E and 5E are used.
ON / OFF control of E is performed. The A / D converter 6 receives the detection voltage, which is the output of the amplifier circuit 10, as an input during fluoroscopy.
D conversion is performed and AD conversion is performed using the integrated voltage output from the integration circuit 5 as an input during photographing.

The CPU 7, the RAM 8 and the ROM 9 constitute a computer, which receives the output of the AD converter 6 and sets the fluoroscopic condition,
The imaging conditions (including the imaging time) are set, and the X-ray tube device is controlled via the I / O port. In this embodiment, this computer also performs offset correction.

Next, the features of this embodiment will be described. This will be described with reference to the time chart of FIG. Figure 2
2A is a time chart at the time of seeing through, and FIG. 2B is a time chart at the time of photographing.

At the time of fluoroscopy, the ON section is an actual fluoroscopy section, and the section before that is a section for obtaining an offset value such as a dark current or a noise electric signal. In the previous section, there is no X-ray irradiation, and the output of the amplifier circuit 10 has a value corresponding to the offset value. This is A by AD converter 6
D-convert and latch in RAM8. AD conversion is shown in Fig. 2.
As shown in (a), it is performed one after another every unit time, and is performed a plurality of times before the start of fluoroscopic activation. Immediately before the start of fluoroscopy, the average value of the AD outputs obtained in the multiple times is set to C
PU7 calculates and latches. Next, the fluoroscopic activation ON section is entered, and the actual fluoroscopic period is entered, and X-rays are emitted together with this section. The output of the amplifier circuit 10 is obtained together with this X-ray irradiation, and the AD converter 6 sequentially performs AD conversion for each unit time. The average value is subtracted from the AD conversion output for each unit time each time. As a result, offset correction is performed. The AD conversion output after this offset correction is the ROM
The CPU 7 compares the fluoroscopic reference value stored in 9 with the fluoroscopic reference value. If it is larger than the reference value, the fluoroscopic condition (fluoroscopic tube voltage, tube current) is lowered because the brightness is high, and if it is smaller than the standard value, the fluoroscopic condition is raised because the brightness is low. This is realized by feedback control to the X-ray tube device 1. By implementing such feedback control, the monitor TV 13
A monitor image with proper brightness can be obtained.

At the time of shooting, a film is attached,
First, shooting is started, and this ON section becomes a shooting section. The first integration interval is set at the start of shooting. Since this section is used as an offset calculation section, X-ray irradiation is not performed. The integrated output at the end of the integration period is AD converted. This AD conversion value is an offset value V due to dark current or the like.
Is. The CPU 7 stores the offset value (V / T) per unit time by dividing the offset value V by the integration section T in the ROM 9
It is calculated according to the program and latched in the RAM 8.

After that, X-ray irradiation is performed, an integration section is set at the same time as this irradiation, and the actual photographing section is entered. In the actual photographing section, the integrated output of the electric signal of the X-ray transmitted through the subject is obtained. The integrated output is converted by the AD converter 6 one after another every unit time, and the offset value is subtracted each time to perform offset correction. Here, the AD conversion output D _i , the offset value (V / T), and the offset-corrected AD conversion output P _i have the following relationship.

## EQU1 ## P _i = D _i −i (V / T) where i is the AD conversion number (number of times) in the actual shooting section, and any one of i = 1, 2, ... Is one. That is, the AD conversion output after offset correction of the i-th conversion output in one section (ON section) of X-ray irradiation is (Equation 1)
Follow The processing of (Equation 1) is performed by the CPU 7 using the RAM 8 according to the program stored in the ROM 9.

Next, the CPU 7 updates the magnitude of P _i and the reference P _th for constant blackening degree control in the ROM 9 while updating i.
Compare. Immediately after the start of X-ray irradiation, P _i <P _th ,
Each time i is updated, P _i approaches P _th . Then, a certain degree of blackening is achieved at the time point when it coincides with P _th in comparison with the AD conversion output several times, and the X-ray is turned off. Naturally, the integration is completed and the start signal is turned off.

Although the film is supposed to be mounted at the time of shooting, it is possible to store the film in the memory instead of the film.

[0020]

According to the present invention, the offset values such as the dark current and the offset electric signal in the system path up to that time, which are included in the AD conversion output, are measured prior to actual fluoroscopy / actual photography, and By subtracting from the AD conversion output at the time of real see-through / real shooting, dynamic offset compensation became possible. As a result, even if the offset value changes over time, those changes are not affected. Can perform fluoroscopy and photography.

[Brief description of drawings]

FIG. 1 is an embodiment diagram of an X-ray fluoroscopic imaging apparatus of the present invention.

FIG. 2 is an operation time chart of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 X-ray tube apparatus 2 X-ray control apparatus 3 Perspective / imaging condition control section 4 I / O port 5 Integrating circuit 6 AD converter 7 CPU 8 RAM 9 ROM 10 Amplifying circuit 11 Automatic exposure control apparatus 12 TV camera 13 TV monitor 14 II (Image Intensifier) 15 Subject

Claims (1)

[Claims] 1. An X-ray source, a table on which a subject is mounted, a film which is excluded from a transmission X-ray passage from the subject during fluoroscopy, and is inserted into the transmission X-ray passage when photographing, and an X-ray transmitted through the subject. Image intensifier that converts light into light, an optical / electrical conversion unit that converts the output light of the image intensifier into an electric signal, and the A / D conversion of this electric signal during fluoroscopy, and the integrated signal of this electric signal during photography. An AD converter for AD conversion, a digital processing means for setting and controlling the fluoroscopic condition from the AD conversion output of the electric signal, and a photographing time from the AD conversion output of the integral signal, and an electric signal output of the optical / electric signal conversion means. To display T
In addition to the V monitor, the digital processing means uses a measuring means for obtaining and latching an AD conversion output which is an offset output in a section where X-rays are not emitted during fluoroscopy and photographing, and by the offset during fluoroscopy. Correcting means for correcting the AD conversion output during actual fluoroscopy with the latched AD conversion output, and correcting the AD conversion output during actual photography with the latched AD conversion output due to the offset during shooting during shooting. X-ray fluoroscopic imaging apparatus having means for performing fluoroscopic condition setting control and imaging time control with the AD conversion output of.