JPS62185488A - X-ray diagnostic device - Google Patents

Abstract

PURPOSE:To use the limited dynamic range of an image pickup tube effectively as much as possible and to improve the picture quality by providing a processor for determining an input and output position of respective rod shape filters in plural steps and a driving part for realizing a wedge filter for displacing and driving the input and output position of the respective rod shape filters based on the output of this processor. CONSTITUTION:The processor 6 sets an avaluation area R with respectic to the same picture on a monitor 7, a safety ratio is optionally set based on an average video signal of this evaluation area R and a threshold level I is decided. The processor 6 feeds one dimentional arrays (z), (y) and the quantity Z (n) of a protrusion as information to the driving part 9. The driving part 9 passes the current corresponding to the Z (n) to an aluminium rod at the position corresponding to the (y, z) based on the Z (n) to drive a motor and push out to an instructed (x) position, namely, the quantity of the protrusion Z (n). According to such a means, the step like wedge filter 10 according to an object 2 is constituted and the above-mentioned operation is repeated on all lines (y=1 to ny). Thereby, a deformable and reproducible wedge filter can be realized. Thereby, the dynamic range of the image pickup tube can be effectively used to improve the picture quality.

Description

[Detailed Description of the Invention] Technical Field of the Invention The present invention relates to an X-ray tube controlled by an X-ray controller, and a method for converting X-rays emitted from the X-ray tube and transmitted through a subject into an optical image. An optical system having an image intensifier, an optical aperture that changes the amount of light of an optical image obtained by the image intensifier, and an image pickup tube that converts the optical image obtained through the optical system into a video signal. The present invention relates to an X-ray diagnostic apparatus such as an X-ray television system having the following.

[Technical Background of the Invention and Problems Therewith] In general, in this type of X-ray diagnostic apparatus, the dynamic range of the image pickup tube is limited, so the image quality of an object with a significant difference in thickness is significantly degraded. For this reason, conventionally, filters such as lead, aluminum, rock salt, clay, water pillow, etc. have been used to correct the subject.

However, although clay, water pillows, etc. are deformable, they have a problem of lack of reproducibility, while lead, aluminum, rock salt, etc. have a reproducibility of 1. L is available, but it has the problem that it is difficult to adapt to the shape of the subject.

Further, such selection of filters is an empirical cut-and-try method that is performed while comparing fluoroscopic images, and object information obtained from fluoroscopy is not fully utilized.

[Object of the Invention] The present invention has been made in view of the above circumstances, and is capable of achieving uniformity of video signals by being deformable and reproducible, and actively utilizing image information during fluoroscopy. , limited R@! The purpose of the present invention is to provide an X-ray diagnostic apparatus that can improve image quality by making the most effective use of the tube's dynamic range.

[Summary of the Invention] The outline of the present invention for achieving the above object is to include an X-ray tube controlled by an X-ray controller, and converting X-rays emitted from the X-ray tube and transmitted through a subject into an optical image. an optical system having an optical aperture that changes the amount of light of an optical image obtained by the image intensifier; and a video tube that converts the optical image obtained through the optical system into a video signal. In the X-ray diagnostic apparatus, the filter regulates the amount of X-rays applied to the subject, and the rod-shaped filter is installed for each line obtained by dividing a two-dimensional plane within the X-ray irradiation area by a predetermined width. Based on the wedge filter that can freely move in and out of the X-ray irradiation area, and the video signal from the 11i1 picture tube, the entrance and exit positions of each of the plurality of stages of rod-shaped filters are determined for each line in order to equalize the video signal. The present invention has a calculation means for determining the calculation means, and a drive means for displacing and driving the input and output positions of each rod-shaped filter based on the output from the calculation means to realize a stepped filter.

[Embodiments of the Invention] Examples of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of an X-ray diagnostic apparatus according to the present invention.

This X-ray diagnostic apparatus includes an X-ray tube 1 controlled by an X-ray controller 8, and an image intensifier 3 that converts X-rays emitted from the X-ray tube 1 and transmitted through a subject 2 into an optical image. an optical system 4 having an optical aperture that changes the amount of light of the optical image obtained by the image intensifier 3; and an i-image tube 5 that converts the optical image obtained through the optical system 4 into a video signal. A processor (calculating means) 6 that processes the video signal obtained from the cough imaging tube 5, a monitor 7 that displays images from the processor 6, and the processor 6.
It has a driving section 9 that obtains more information and drives it, and wedge filters 10 on both left and right sides that are arbitrarily deformed by the driving section 9 and correct the subject 2.

The main parts will be explained in detail below.

As shown in FIG. 2, the basic unit that constitutes the wedge filter 10 is a rod-shaped rectangular parallelepiped (rod-shaped filter) with a width W, a thickness, and a length l, with a scale a obtained by dividing l into m equal parts, and its material is Assuming that the human body consists of water, it is desirable to have a tube voltage dependence similar to that of water. Here - as an example AI
is used.

At tube voltages from 5Qkv to around 150kv, Al
Because it has approximately 3 to 4 times the absorption properties compared to water,
For example, when correcting a difference in body pressure of 30 cm, 100 m
Correction is possible with a certain thickness, and since it is made of light metal, it is easy to operate.

The overall configuration of the wedge filter 10 is such that aluminum rods like this are arranged in two directions, the y direction, as shown in FIG. 3, and the correction of the subject 2 is WXj! For density direction 2, quantized correction is performed in the thickness direction h in quadrilateral units of /m.

Next, a control means using this wedge filter 10 will be explained.

First, the processor 6 converts the image obtained during fluoroscopy into a fourth image.
As shown in the figure, the average video signal value I (x, y) of the video signal in each square is divided into nxxny meshes.
seek. Division size nx.

ny is WXi! in the wedge filter as shown in FIG. It is found by dividing a quadrilateral of /m based on the size A projected onto the surface of the subject.

On the other hand, the processor 6 controls the monitor 7 as shown in FIG.
An evaluation region R is set for the same image above, and a safety factor α is arbitrarily set based on the average video signal value of the evaluation region R to determine a threshold level 11. The graph in FIG. 4 shows the relationship between the video signal XX including the evaluation area R and the threshold level 11. If the evaluation area spans a plurality of squares, the maximum value of the average video signal value is selected as a reference, and the threshold level 11 is determined in the same manner as described above.

Next, the processor 6 calculates A according to the tube voltage V during fluoroscopy.
The average absorption coefficient μ(V) of l is determined from the internal table, and the threshold level Il corresponding to A1 is calculated using the following formula (1).
Calculate by

te= (An lo-l1n Ii')/μ(V
)...(1) Here, In is the subject incident signal.

Next, the following process is performed using te obtained by the above equation (1) and the threshold level IJl determined previously.
, ny for every (nx) lines in the X direction.

That is, the previously obtained average video signal value 1 (x, y) in each divided square is compared with the threshold level Il, and when I (x, y) > IA, the average video signal value 1 (x, y) is compared with the threshold level Il. Calculate ff1t (x, y) using the following formula (2), j (X, V) = lnIo-Ilnl (X, V))/
μ(V)...(2) Calculate the difference between this t (x, y) and the above t1, and calculate the thickness difference in s degrees and z direction T (
x) is calculated using the following equation (3).

T (X) = [(t (X, Y) - tl )/1
1]-(3) Note that [] is a Gauss symbol.

Then, when I (x, y)≦11, set T(x>=O, find bsrT(x) for nx from X-1, and create a one-dimensional array in the X direction as shown in Figure 6. In other words, in Fig. 6, T(1] = 4 indicates that the thickness of the filter is required to be 4h in the mass of the portion of X = 1 in one line in the X direction, and similarly, T (2
)=3 indicates that the filter needs to have a thickness of 3h in that mass, that is, in the mass portion of the X=2 portion.

Note that FIG. 6 shows the case where nx=io. The processor 6 further divides this one-dimensional array in the X direction into two parts, left and right, at the center O-0, as shown in FIG. Create two one-dimensional arrays in seven directions on the left and right. In other words, in Fig. 7, Z(1) = 4 in the left array means the first aluminum bar from the bottom is moved by four scales in the X direction, and Z(2) = 3 means the second aluminum bar from the bottom is moved in the X direction. This indicates that the desired filter shape is formed by extruding by 3 scales (
(See Figure 8). As is clear from FIG. 8, the X=1 portion has a thickness of 4h, and the X=2 portion has a thickness of 3h.

The processor 6 then generates a one-dimensional array z, y.

The above projection ff1Z(n> is sent as information to the drive section 9, and the drive section 9 drives the motor by passing a current corresponding to Z(n) only through the aluminum rod at the position equivalent to this (y, z). to the designated X position, that is, the protrusion 12 (n
). By such means, a stepped wedge filter corresponding to the subject 2 is constructed, and all lines (y=
By repeating the above operations for 1 to ny), a wedge filter that is deformable and reproducible as shown in Fig. 9 is realized, which makes it possible to effectively use the dynamic range of the eye tube and improve image quality. will improve.

Although one embodiment of the present invention has been described above, it goes without saying that the present invention is not limited to the above-mentioned embodiment, and can be modified as appropriate within the scope of the gist of the present invention.

For example, in Figure 9, the material of the aluminum rod constituting the filter is a very absorbent substance.

Several types of medium m2, small material m3 are prepared, and the thickness h is hl, h2. By setting h3..., it is possible to realize a wedge filter that is more suitable for the subject than in the above embodiment.

[Effects of the Invention] As described in detail above, according to the present invention, by actively utilizing image information when viewing a subject, it is possible to form a filter that is deformable, reproducible, and suitable for the subject. Therefore, it is possible to equalize the video signal and make the most effective use of the limited dynamic range of the cathode ray tube to improve image quality.

[Brief explanation of drawings]

Figure 1 is a block diagram of the X-ray diagnostic neck of the present invention, Figure 2 is a perspective view of an aluminum rod that is the basic unit of the wedge filter, Figure 3 is the closure of the wedge filter, and Figures 4 to 9 are FIG. 6 is an explanatory diagram of each action. DESCRIPTION OF SYMBOLS 1... X-ray tube, 2... Subject, 3... Image intensifier, 4... Optical system, 5... Vmfl tube, 6... Calculating means, 7...
Monitor, 8... X-ray controller, 9... Drive means, 10... Wedge filter. Agent Patent Attorney Yudo Noriyuki Chika
Nori Ogo Mistake 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 7

Claims (1)

[Claims] An X-ray tube controlled by an X-ray controller, an image intensifier that converts the X-rays emitted from the X-ray tube and transmitted through the subject into an optical image, and an optical image obtained by the image intensifier. In an X-ray diagnostic apparatus, the X-ray diagnostic apparatus includes an optical system having an optical aperture that varies the amount of light, and an image pickup tube that converts an optical image obtained through the optical system into a video signal. A wedge filter, which is a regulating filter, and in which a rod-shaped filter can be freely moved in and out of the X-ray exposure area for each line obtained by dividing a two-dimensional plane in the X-ray exposure area by a predetermined width; calculation means for determining the input and output positions of each rod-shaped filter in multiple stages for each line in order to equalize the video signal based on the video signal; and the input and output positions of each rod-shaped filter based on the output from the calculation means. An X-ray diagnostic apparatus comprising: a drive means for displacing and driving the filter to realize a stepped filter.