JPH04352576A - X-ray television receiver - Google Patents

Abstract

PURPOSE:To display both objects with high and low contrasts on optimum conditions by detecting the maximum and minimum values of an analog image signal and setting the upper and lower reference voltages of an A/D converter based on those values. CONSTITUTION:The analog image signal is inputted from a TV camera 13 to a maximum/minimum value detection circuit 19. The circuit 19 detects image signal values VMAX and VMIN respectively corresponding to maximum and minimum luminances from image signals in the prescribed range of one picture and transmits the values to a reference voltage generation circuit 20. Based on these maximum and minimum values, the circuit 20 generates upper and lower reference voltages VRF+ and VRF- for an A/D converter 14, inputs them to the relevant terminal of the converter 14 and sets the upper and lower reference voltages. The converter 14 digitizes the analog image signal from the camera 13 to the prescribed number of bits between these upper and lower limit values. Afterwards, an image processing is executed and the analog image signal is recovered at a D/A converter 16 and visibly displayed at a CRT 17.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray television apparatus used in the medical field.

0002

2. Description of the Related Art The configuration of a conventional X-ray television apparatus with an image processing function is shown in FIG. To briefly explain its function, X-rays emitted from the X-ray tube 10 and transmitted through the subject 11 are transferred to an image tube (Image Intensifier).
=II) Form a visible image on 12 projection planes. A television (TV) camera 13 photographs this image, and the TV camera 13 outputs an analog image signal. The analog image signal is converted into digital image data by an A/D converter (ADC) 14, and is subjected to various image processing such as edge enhancement in an image processing circuit 15. The digital image data processed in this way is transferred to a D/A converter (DA
C) 16 converts the signal into an analog image signal again and displays it on the display device 17.

[0003] Here, the brightness is set within a predetermined range on the projection surface of the image tube 12 so that the image displayed on the display device 17 always has an appropriate brightness even if the X-ray transmittance of the subject 11 varies. A photo pick-up 21 for detecting the brightness is provided inside the optical system, and the X-ray controller 18 sets the operating conditions (tube current and tube voltage) of the X-ray tube 10 to appropriate values based on the brightness data. .

0004

[Problem to be Solved by the Invention] The feedback control of the above-mentioned X-ray conditions in the conventional X-ray television apparatus is as follows:
This is done so that the average brightness within a predetermined range including the center of the screen is constant, so the X When the line condition is set, when projecting an object such as a lung field that has a large difference in object thickness (high contrast), thin areas may show blown-out highlights (halation) and thick areas may show blown-out black areas. On the other hand, if the X-ray conditions are determined based on areas where the thickness of the object differs greatly, when a flat object is projected, the contrast will be extremely low and details will be lost. Furthermore, even if image signals with such blown-out highlights or blown-out shadows are digitized and image processed, the image processing may become meaningless because the processing is processing data that originally had lost information. There is. The present invention was made to solve these problems, and its purpose is to be able to display both low-contrast and high-contrast subjects under optimal conditions, and to always display meaningful images. An object of the present invention is to provide an X-ray television device that can perform certain image processing.

[0005]

[Means for Solving the Problems] An X-ray television apparatus according to the present invention, which has been made to solve the above problems, has the following features:
(b) detects the maximum value and minimum value of the analog image signal and generates an upper limit value signal and a lower limit value signal based on the maximum value and minimum value of the analog image signal; (c) A converting the analog image signal into a digital signal having a predetermined number of bits between the upper limit value signal and the lower limit value signal;
/D converter.

[0006]

[Operation] The image adjustment circuit (b) first receives an output signal (analog image signal) from the television camera (a), and detects the maximum and minimum values within a predetermined range A within one screen. The predetermined range A here may be the entire screen, but is preferably the central part of the screen excluding the peripheral part in order to remove parts other than the image of the subject. Image adjustment circuit (b
) further generates an upper limit signal and a lower limit signal based on these maximum and minimum values. These values may be equal to the maximum and minimum values detected earlier, but in order to make the screen easier to see on the display device, (maximum value + α)
, (minimum value - α) with a little margin. The upper limit value signal and lower limit value signal thus generated by the image adjustment circuit (b) are given to the A/D converter (c), and the A/D converter (c) is connected to the television camera (
The analog image signal output from a) is digitized into a predetermined number of bits between these upper and lower limits.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of an X-ray television apparatus which is an embodiment of the present invention. The X-ray television device of this embodiment differs from the conventional X-ray television device shown in FIG.
A circuit 19 that detects the maximum and minimum values of the output signal (analog image signal) of the TV camera 13, and an A/D converter 14 that receives the detected maximum and minimum value signals.
The difference is that a reference voltage generation circuit 20 for generating upper and lower reference signals VRF+ and VRF- is provided.

The operation of the X-ray television apparatus of this embodiment is as follows. Generated from the X-ray tube 10, the object 11
The transmitted X-rays form a visible image on the projection plane of the image tube (II) 12. The TV camera 13 photographs an image on the projection plane, generates a predetermined analog image signal, and sends it to the A/D converter 14 and the maximum/minimum value detection circuit 19.

The maximum/minimum value detection circuit 19 detects image signal values VMAX and V corresponding to the maximum brightness and minimum brightness from among the image signals within a predetermined range (this is referred to as A) in one screen.
Detect MIN. The predetermined range A here is:
Although it is desirable to set the range so that the subject image can be captured under normal shooting conditions, excluding the peripheral part of the screen, it may be the entire range of one screen of the TV signal. Maximum/minimum value detection circuit 19
Maximum and minimum signal values VMAX, VMIN detected by
is sent to the reference voltage generation circuit 20.

The reference voltage generation circuit 20 calculates A/V based on these maximum and minimum signal values VMAX and VMIN.
Upper/lower reference voltage VRF+ for D converter 14
, VRF- is generated. Here, the range (width) of the reference voltage is made slightly wider than the range (width) of the maximum and minimum values of the image signal, for example, VRF+=VMAX×1.1 VRF−=VMIN×0.9. Upper and lower reference voltages VRF+ and VRF generated in this way
- is input to the corresponding terminal of the A/D converter 14.

The A/D converter 14 converts a voltage range VRF- to VRF+ with upper and lower reference voltages as upper and lower limits.
is equally divided into a predetermined number (quantization step number) of small ranges, and T
The analog image signal from the V camera 13 is converted into digital data depending on which of the small ranges the analog image signal falls within.

[0012] The digitized image data is subjected to image processing (for example, noise removal, edge enhancement using differential operations, etc.) according to the purpose by various well-known image processing operations. The digital image data subjected to image processing is converted back into an analog image signal by the D/A converter 16, and is visually displayed by the CRT 17.

Note that if the original X-ray image projected onto the projection surface of the image tube 12 is not sufficiently good, it is impossible to obtain a good image display on the CRT 17 no matter what image processing is performed afterwards. Therefore, as before, a photo pickup 21 is installed inside the image tube 12, and the tube current and tube voltage of the X-ray tube 10 are controlled by the X-ray controller 18 so that the image on the projection surface always has the optimum brightness. Feedback control.

In this embodiment, as described above, the TV camera 1
Since the reference voltage for A/D conversion is determined based on the data of the image actually shot in step 3, the image data of the main part of the screen (within range A above) is always converted to digital data, and the information is The image is processed without any loss and is displayed on the display device (CRT) 17.

Examples of generation of reference voltages VRF+ and VRF− in the X-ray television apparatus of this embodiment are shown in FIGS.
Shown in Figure 5. In the example of FIG. 3, the X-ray fluoroscopic image is relatively flat (the contrast of the main part A is low), so the range of the maximum and minimum values VMAX and VMIN of the image signal is relatively narrow, and the reference voltage VRF+1, VR
The range of F-1 is also narrower. However, since the number of quantization steps in the A/D converter 14 is constant,
Even small differences in brightness are digitized with sufficient distinction, and by performing appropriate image processing and D/A conversion, the details of the image can be sufficiently distinguished on the display device 17. Note that in order to prevent meaningless gradation from being performed even when the image originally has no detail and is flat, a minimum limit may be set for the width of the reference voltages VRF+ and VRF-.

FIG. 4 shows an example of an image in which the X-ray transparency in the center of the subject is very low, and a conventional X-ray television apparatus would cause blackout in that part. In the embodiment, since the lower limit reference voltage VRF-2 is set to be surely lower than the minimum value VMIN of the image signal, the image information of that part is also processed and displayed without being lost. . On the contrary, the example shown in FIG. 5 is an example of an image where the X-ray transparency in the central part is very high, and in a conventional X-ray television apparatus, that part would cause halation. In this case too,
Since the upper limit reference voltage VRF+3 is always set to be equal to or higher than the maximum value VMAX of the image signal, image processing and display are performed without losing the details of that part.

Furthermore, as shown in FIG. 6, the TV camera 13
The present invention can be similarly applied to an X-ray television apparatus in which a nonlinear amplifier such as a gamma amplifier 25 is installed between the A/D converter 14 and the A/D converter 14. In this case, the maximum/minimum value detection circuit 19 must receive a signal from the output side of the nonlinear amplifier 25 (that is, from immediately before the input of the A/D converter 14) and detect the maximum and minimum values. Must be.

[0018]

Effects of the Invention In the X-ray television apparatus according to the present invention, the reference voltage of the A/D converter is set in consideration of the maximum and minimum values of the signal of the image actually taken by the TV camera. To perform effective image processing at all times without losing the information of the original image during image processing, and to display an appropriate image without blown-out highlights or blown-out shadows on the screen of a display device.

[Brief explanation of drawings]

[Fig. 1] X with image processing device, which is an embodiment of the present invention
FIG. 1 is a block diagram showing the basic configuration of a line television device.

FIG. 2 is a block diagram showing the configuration of a conventional X-ray television device with an image processing device.

FIG. 3 is a graph showing reference signal generation in the case of a flat image.

FIG. 4 is a graph showing how a reference signal is generated in the case of an image where black collapse is likely to occur in some parts.

FIG. 5 is a graph showing reference signal generation in the case of an image where halation is likely to occur in some parts.

FIG. 6 is a partial block diagram showing a modification of the embodiment.

[Explanation of symbols]

10...X-ray tube
11...Subject 12...Image tube
13...TV camera 14...A/D converter (ADC) 15...Image processing circuit 16...D/A converter (DAC) 17...Display device (CRT) 18...X-ray controller
19...Maximum/minimum value detection circuit 20...Reference voltage generation circuit 21...Photo pickup 25...Nonlinear amplifier

Claims (1)

[Claims] 1. A television camera that photographs an image formed on an image tube and outputs an analog image signal;
An image adjustment circuit that detects the maximum value and minimum value of an analog image signal and generates an upper limit value signal and a lower limit value signal based on them; A to convert into a numerical digital signal
/D converter.