JPH0553108B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to transmitted X-rays obtained by irradiating an object with X-rays.
The present invention relates to an X-ray diagnostic apparatus that obtains image information for medical diagnosis using visible images of rays.

[Technical background of the invention and its problems] Recent X-ray diagnostic devices that emit X-rays onto a subject and obtain image information useful for medical diagnosis from the X-rays that have passed through the subject are different from conventional ones. This system was developed by adding various image processing functions to the X-ray television diagnostic device of 1999.It has excellent temporal resolution because it can take repeated images, and the immediacy of image display. Many of them have features such as being able to highlight and display the part you want to identify.

Incidentally, in such an X-ray diagnostic apparatus, an image pickup tube is used as a means for converting an optical image into an electrical signal. In general, image pickup tubes have a small dynamic range of about 60 dB, which is the ratio between the maximum signal that can be extracted and the noise generated in the signal amplification system of the TV camera circuit. It has the disadvantage that only a range of information can be collected. Therefore,
With this type of X-ray diagnostic apparatus, it is impossible to simultaneously capture an image of a blood vessel overlapping a large bone of a subject and an image of a blood vessel located in a portion where X-rays are well transmitted.

Therefore, in the past, X-rays that do not pass through the subject and directly enter the image intensifier (hereinafter referred to as "II") are blocked by an X-ray diaphragm, or
Measures have been taken to limit the amount of transmitted X-rays by placing an appropriate X-ray filter or the like in areas where radiation is likely to pass through, or by adjusting the aperture in the optical system to limit the amount of transmitted light.

[Object of the invention] The present invention has been made in view of the above circumstances, and its purpose is to
An object of the present invention is to provide an X-ray diagnostic device that can take images with a wide latitude by using a TV camera incorporating a solid-state image sensor whose photoelectric conversion characteristics can be controlled in place of a TV camera.

[Summary of the Invention] In order to achieve the above object, the X-ray diagnostic apparatus of the present invention uses an image intensity system that converts transmitted X-rays obtained by irradiating a subject with X-rays generated from an X-ray tube into an optical image. a TV camera that captures this optical image and converts it into an electrical signal, and a display unit that performs predetermined processing on this electrical signal and displays a diagnostic image of the subject, and the TV camera functions as a photoelectric conversion element. A solid-state image sensor capable of controlling photoelectric conversion characteristics is provided, the photoelectric conversion characteristics are changed and set according to the incident illuminance value obtained by preliminary exposure, and the display means is configured to at least change the set photoelectric conversion characteristics as the processing. Accordingly, density conversion processing is performed to linearize the relationship between the amount of X-ray transmission and the image pixel value.

[Embodiments of the Invention] The present invention will be described below with reference to illustrated embodiments.

FIG. 1 is a block diagram showing the configuration of an X-ray diagnostic apparatus according to an embodiment of the present invention. In the same figure,
Reference numeral 1 denotes an X-ray tube that is driven by a high voltage generator or the like (not shown) and irradiates X-rays to the subject P; 2 indicates an II that converts the transmitted X-rays that have passed through the subject P into an optical image;
3 is an optical system that guides the output image of II2 to the TV camera;
4 is a TV camera with a built-in solid-state image sensor that converts an optical image into an electrical signal; 5 is an A/D converter that converts the output from the TV camera 4 into a digital quantity; 6
7 is a processor equipped with a memory that stores the output of the A/D converter 5 and an arithmetic processing circuit that performs predetermined arithmetic processing; 7 is a TV monitor that displays the video information output from the processor 6; 8 is this device. This is a control console that controls the entire system.

FIG. 2 is a photoelectric conversion characteristic diagram of the TV camera 4 with a built-in solid-state image sensor of the device shown in FIG. The photoelectric conversion characteristics are shown when photoelectric conversion characteristics are not controlled. As shown by the broken line, when photoelectric conversion control is not performed, the characteristics change linearly and the slope remains constant until the output signal current of the TV camera 4 is saturated (the saturation point is S). However, as shown in practice, when photoelectric conversion control is performed, it bends at the K point, and the K
In the illuminance region exceeding the point, the slope of the characteristic curve becomes smaller. Therefore, compared to the case where photoelectric conversion control is not performed, the width L of the incident illuminance region is expanded, and an image with a wide latitude can be obtained.

Note that the above-mentioned point K is not always constant, but in order to effectively expand the incident illuminance region width L,
Before the main irradiation, a preliminary irradiation is performed to recognize the subject's body pressure, and depending on the incident illuminance value at that time, the K point is set, for example, around 80% of the peak value of the incident illuminance. It is.

FIG. 3 is a correlation diagram between the amount of X-ray transmission and the image pixel value for explaining the second basic configuration of the present invention. Processor 16 receives photoelectric conversion characteristic control.
As shown by the solid line in Figure 3, the image data stored in
The pixel value is not proportional to the dose as a linear function.

Therefore, the processor 16 performs density conversion processing to make the relationship between the two proportional to each other as a linear function.
The process is carried out as shown by the dashed line in FIG. In order to do this, the bending point K of the photoelectric conversion characteristic of the TV camera 4 and the slope of the characteristic curve are set on the system control console 18, and then the TV camera 4 is controlled. This set value is then sent to a calculation section in the processor 6 (not shown) and used as a parameter for density conversion processing. Then, based on this parameter, this calculation section multiplies the image data values below the image data value of point K in FIG. Then, density conversion processing is executed by multiplying by 1/g. Here, g is the ratio of the slopes of the polygonal lines in FIG. 3 (g2/g1). FIG. 4 is a characteristic diagram showing the relationship between the multiplication coefficient and the pixel value of the image in the density conversion process.

[Effects of the Invention] As described above, according to the present invention, transmitted X-rays transmitted through a copying object are converted into an optical image by I/I, the optical image is converted into an electrical signal, and the electrical signal is further converted into an optical image. In X-ray diagnostic equipment that converts images into digital signals, performs predetermined processing, and displays diagnostic information, a TV camera with a built-in solid-state image sensor that can control photoelectric conversion characteristics is used as a means of converting optical images into electrical signals. Furthermore, by performing density conversion, it becomes possible to obtain an image with a wide dynamic range. Therefore, even if the subject has a wide distribution of the amount of transmitted X-rays, it is possible to obtain an image that does not suffer from halation or is cut off to a dark level.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention;
Figure 2 is an input/output characteristic diagram of a TV camera whose photoelectric conversion characteristics can be controlled, and Figure 3 is the correlation between the amount of X-ray transmission and image pixel values to explain the image density conversion process under control of the photoelectric conversion characteristics. Similarly, FIG. 4 is a characteristic diagram showing the relationship between the multiplication coefficient and the pixel value of the image. 1... X-ray tube, 2... Image intensifier, 4... TV camera, 5... A/D converter, 6... Processor, 7... TV monitor, 8... System control processor.

Claims (1)

[Claims] 1. An image intensifier that converts transmitted X-rays obtained by irradiating a subject with X-rays generated from an X-ray tube into an optical image, and that captures this optical image and converts it into an electrical signal. The TV camera is equipped with a display means that performs predetermined processing on the electrical signal and displays a diagnostic image of the subject, the TV camera is equipped with a solid-state image sensor that can control photoelectric conversion characteristics as a photoelectric conversion element, and the The photoelectric conversion characteristic is changed and set according to the incident illuminance value obtained by preliminary exposure, and the display means displays the relationship between the amount of X-ray transmission and the image pixel value according to at least the set photoelectric conversion characteristic as the processing. An X-ray diagnostic device characterized by performing density conversion processing for linearization.