JPH0551294B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an X-ray image display device that displays an X-ray fluoroscopic image of a subject.

(Prior Art) Conventionally, an operation of inserting a curtain or a guide wire into a patient's blood vessel has been frequently performed. In such cases, operations are performed while viewing a moving X-ray fluoroscopic image (hereinafter simply referred to as a real image). Since blood vessels are not shown in this real image, a vascular contrast agent-containing image (referred to as a road map image) taken immediately after injecting an angiographic contrast agent is displayed on the monitor in parallel with the real image. , a method is used in which the catheter or guide wire is operated while recognizing the direction in which it is to be advanced. More recently, a method has been attempted in which a road map image and a real image are superimposed and output on a monitor (referred to as superimposition). According to this method, an angiographic image is clearly displayed on a real image in which blood vessels are not displayed. Therefore, this superimposition improves the operability of the catheter compared to the case where the real image and the road map image are displayed side by side.

(Problem to be Solved by the Invention) In the above superimposition, if the positions of the road map image and the real image match, it is very effective in recognizing the direction in which the catheter or guide wire should be advanced. If there is a certain amount of positional deviation between the road map image and the real image due to body movements, etc., it will be extremely difficult to see, and will even become a hindrance to operation. Therefore, the operator must perform operations such as canceling the superimposition and outputting only the real image on the monitor, or correcting the position of the patient's body and continuing the superimposition. This places a heavy burden on doctors who perform extremely delicate work.

Therefore, the present invention solves the above-mentioned drawbacks, and it is an object of the present invention to accurately determine a positional deviation of more than a predetermined value between a road map image and a real image in superimposition, and to output only the appropriate superimposition to a monitor. The object of the present invention is to provide an X-ray image display device capable of

[Structure of the Invention] (Means for Solving the Problem) In order to solve the above problems, the present invention provides an The line image display device performs arithmetic processing between the vascular contrast agent-containing image recorded in the image memory and the fluoroscopic image, and uses the result of this calculation to display a difference between the vascular contrast agent-containing image and the fluoroscopic image. The apparatus is characterized in that it includes a positional deviation detection circuit that detects a positional deviation of the image, and an output processing section that switches the monitor output from a superimposed image to a perspective image under the control of this positional deviation detection circuit.

(Function) The positional deviation detection circuit performs calculation processing between the real image and the road map image, detects positional deviation between the two by analyzing the calculation result, and
By controlling the output processing unit according to the degree of this positional shift, only a real image or a superimposed image is output to the monitor as appropriate.

(Example) A first example of the X-ray image display device according to the present invention will be described below with reference to the drawings. Here, FIG. 1 is a block diagram showing the overall configuration of the X-ray image display apparatus in this embodiment, and FIG. 2 is a block diagram showing the detailed configuration of the positional deviation detection circuit 5 in FIG. 1.

In FIG. 1, an X-ray tube 1 irradiates a subject P with X-rays. The X-rays that have passed through the subject P are
It is converted into an electrical signal by a system 2 consisting of a radiation detector and an imaging tube. Furthermore, this
An A/D converter 3 that digitally converts the electrical signal from the system 2, an image memory 4 that records the digital signal from the A/D converter 3, and an A/D converter 3 that converts the electric signal from the system 2 into a digital signal; an image memory 4 that records the digital signal from the A/D converter 3;
A positional deviation detection circuit 5 compares the output from the D converter 3, determines the positional deviation between the two, and controls the superimpose processing section 6 at the subsequent stage. It consists of a superimpose processing unit 6 that outputs an image, a display system 7 that converts the output from the superimpose processing unit 6 into an analog signal, and a monitor 8 that outputs the output of the display system 7 as an image. .

Furthermore, to describe the configuration of the positional deviation detection circuit 5 in detail, the input from the image memory 4 is sequentially transmitted to the reduction circuit 12, the logarithmic conversion circuit 15, the reduction image memory 16,
The input from the A/D converter 3 is connected to the position shift circuit 14 and the subtraction circuit 17, and the input from the A/D converter 3 is sequentially connected to the reduction circuit 1.
1, connected to a logarithmic conversion circuit 13 and a subtraction circuit 17, and further connected to a histogram creation circuit 18, a mode calculation section 19, a standard deviation calculation section 20, and a comparison circuit 21.
This comparison circuit 21 controls the superimpose processing section 6.

Next, the operation of the above configuration will be explained.

First, X-rays are emitted from the X-ray tube 1 toward the subject P, and the X-rays that have passed through the subject P are converted into electrical signals by the system 2, and then
The converter 3 converts it into a digital signal.

Here, when inserting the guide wire into the blood vessel of the subject P, a road map image of the angiogram injected is taken in advance immediately beforehand, but this road map image is stored in the image memory. Recorded in 4. It is desirable that the image memory 4 has a capacity sufficient to record an image for one heartbeat, since there are many cases in which treatment is applied to areas such as the heart.

When capturing a real image for guidewire insertion is started, no new writing is performed to the image memory 4, and the digital signal from the A/D converter 3 is transferred to the reduction circuit 11 in the positional deviation detection circuit 5.
The image matrix size is reduced (e.g.
1024 ² →256 ² ), and is further subjected to logarithmic conversion in the logarithmic conversion circuit 13 before being sent to the subtraction circuit 17 . At the same time, the load map image is read out from the image memory 4, and the reduction circuit 12 and the logarithmic conversion circuit 1
After the same processing in step 5, the reduced image is once written into the reduced image memory 16, and then the reduced image is shifted one pixel vertically and horizontally in the position shifting circuit 14 (see Fig. 5) to create an image, and subtraction is performed along with these images. The signal is sent to circuit 17. In this subtraction circuit 17, pixel density is subtracted between the road map image, the road map image obtained by shifting the position of the road map image, and the real image (the image obtained by this is called a subtract image). Histogram creation circuit 1
8, a histogram of each of these subtract images is created. Next, the mode calculation unit 1
9. The standard deviation calculation unit 20 calculates the frequency and standard deviation of the mode of the previous histogram, and sends these values to the comparison circuit 21, which evaluates them to determine the difference between the real image and the road map image. The presence or absence of positional deviation or the one with the least positional deviation between the real image and each road map image is determined, and only the real image is output to the monitor, or the real image and the road map image are superimposed and output to the monitor. The superimpose processor 6 is then controlled. The superimpose processing unit 6 sends the image data to the display system 7 under the control of the comparator circuit 21, and after processing such as analog conversion is performed in the display system 7, the image is displayed on the monitor 8.

Here, the principle behind the processing in the positional deviation detection circuit 5 will be explained.

Here, reduction circuits 11 and 12, logarithmic conversion circuit 1
3 and 15 are provided to eliminate complicated circuits to increase processing speed and realize real-time processing speed. calculation speed is achieved.

Next, logarithmic transformation will be explained. When performing X-ray photography, conditions such as current and voltage applied to the X-ray tube are often changed depending on the situation. In such a case, it is not appropriate to simply compare, but it is better to perform logarithmic transformation and then perform subtraction processing. That is, when the same object is exposed to X-rays under different conditions, the amount of X-rays transmitted will be, for example, f(x, y) and af(x, y). Here, x and y are position variables, and a is a constant. Furthermore, if the state of the object differs, the amount of X-ray transmission will be, for example, ag(x, y). If this is subtracted after logarithmic transformation, logag (x, y) - logf (x, y) = loga + (logg (x, y) - logf (x, y)).

In other words, the differences between the two are correctly reflected except for the constant loga. Therefore, if the result of this subtraction is not concentrated on a certain constant, it is considered that there is a positional shift between the two.

To give a concrete example, if the profiles of the real image and the road map image are subtracted after logarithmic transformation, one image of either the contrast blood vessel area or the guide wire area can be obtained, as shown in Figure 3. The portions other than the portion where only 1 is present are concentrated around a certain constant a (if there is no positional shift between the two).

In this manner, the subtractor circuit 17 subtracts the two images, and the histogram creation circuit 18 creates a histogram based on the pixel density and frequency of the subtract image. Furthermore, the frequency and standard deviation of the mode of this histogram are calculated by the mode calculation section 19 and the standard deviation calculation section 20. As already mentioned, such calculations are performed for all images read out from the reduced image memory 16 and images whose positions have been shifted by the position shifting circuit 14. The comparison circuit 21 selects from among these the one with the highest frequency of the mode and the one with the smallest standard deviation. If the image with the highest frequency of the mode and the image with the lowest standard deviation are different, the image with the highest frequency of the mode is selected. It is determined that the road map image corresponding to this subtract image is the image with the smallest positional deviation from the real image (see FIG. 4).

Further, the frequency and standard deviation of the most frequent value are compared with a certain reference value to determine the degree of positional deviation. If the frequency of the mode is smaller than the reference value or the standard deviation is larger than the reference value, it is determined that the positional deviation between the two is large.

This reference value is not an absolute value, but a value that can be set by each user of the device. Furthermore, since the number of pixels that deviate from the mode can be predicted to some extent depending on the amount of contrast medium injected, it may be determined based on this. Alternatively, it may be determined in advance through experiments using a phantom or the like. Furthermore, priority may be given to the standard deviation.

As described above, if the comparison circuit 21 determines that there is no positional deviation or that the positional deviation is small, a control signal is sent to the superimposition processing section 6 to execute superimposition. Furthermore, if it is determined that the positional shift is large, superimposition is stopped and only the real image is output to the monitor. At this time, only the real image may be output while gradually fading out the road map image so as not to create a sense of incongruity with superimposition.

Furthermore, since the above-described processing continues even if superimposition is stopped, superimposition is output again when the positional shift becomes smaller.

As explained above, in the X-ray image display device configured as described above, only appropriate superimpositions are outputted, and superimpositions that would impede operation are not outputted, so that accurate operations can be performed. It becomes possible.

Next, a second embodiment of the present invention will be described using FIG. 6. This embodiment is implemented by changing the analysis circuit 100 shown in FIG. 4 in the first embodiment to an analysis circuit 200 shown in FIG. The analysis circuit 200 is the histogram creation circuit 1
8, a maximum value calculation section 31, a mode value calculation section 32, a threshold generation section 33, a counter 34, and a comparison circuit 35.

Since the guide wire insertion operation is performed immediately after the road map image is photographed, it is considered that there is no positional deviation between the real image and the road map image at the start of the guide wire insertion operation. Therefore, when the road map image is read out from the image memory, a threshold level is first set, and subsequent determination of the presence or absence of positional deviation is made based on this threshold level. To explain in detail, image memory 4
When the road map image is read out from , the same processing as in the first embodiment is performed. However, the processing in the position shifting circuit 14 is not performed here. In this way, a histogram of the subtract image is created by the histogram creation circuit 18. Next, the maximum density and the mode density of this histogram are calculated by the maximum value calculation unit 31 and the mode value calculation unit 32, respectively, and the threshold generation unit 33 calculates between the maximum density and the mode density. A certain threshold level is set. The counter 34 calculates the number A of pixels having a pixel density equal to or higher than this threshold level.
is counted. This number A and the threshold level are set as reference values for comparison.

Thereafter, a road map image, a subtract image of the road map image obtained by shifting the position of the road map image, and a subtract image of the real image, and a histogram are created one by one. These histograms are sent to counter 34. This counter 34 counts the number of pixels that are above the threshold level. And comparison circuit 3
5, it is determined that the one closest to A among these counts is the one with the least positional deviation. That is, for example, a histogram having the number of pixels B closest to A indicated by diagonal lines in a histogram with a threshold level set in FIG. do. Furthermore, if there is a difference between A and B, for example 100 or more (for example, histogram 203), it is determined that the positional shift is large, and superimposition processing is performed to cancel superimposition and output only the real image. Control part 6. If it is less than 100, it is determined that there is no positional deviation or it is small, and the superimpose processing unit 6 is controlled to output a superimposed image.

As explained above, in the second embodiment, as in the first embodiment, the positional deviation between the road map image and the real image is accurately determined, and the superimposition that becomes an obstacle to the guidewire insertion operation is eliminated. It is possible to easily execute the operation by outputting only the appropriate superimposition without outputting the pose.

In another embodiment, when an operation is performed on a part of the body that moves rapidly, such as the heart, time phase information is added to the road map image recorded in the image memory, and the road map image read out from the image memory is periodically changed. If carried out, it becomes possible to appropriately superimpose parts such as the heart.

Further, in the above embodiments, the case where the entire frame of the image is processed has been described, but it goes without saying that the same effect can be obtained even if the calculation is performed on only one specific line (or several lines).

Furthermore, this can be done more accurately by synchronizing it with an electrocardiogram or the like.

In addition to the methods described above, there are countless other statistical analysis methods, and it is possible to implement each of them in the same way, and even more rigorous positional deviation detection is also possible. Therefore, the present invention is not limited to the above embodiments.

[Effects of the Invention] As explained above, according to the present invention, only appropriate superimpositions are output without outputting superimpositions that have been misaligned beyond a certain degree, thereby reducing unnecessary burden on the doctor. It is possible to provide an X-ray image display device that does not give

[Brief explanation of drawings]

1 and 2 are block diagrams showing the configuration of the first embodiment of the X-ray image display device according to the present invention, FIG. 3 is a simplified diagram showing the principle of logarithmic conversion and subtraction, and FIG. FIG. 5 is a diagram showing an example of the histogram of the embodiment, and FIG. 5 is a diagram simply showing the position shift.
FIG. 6 is a block diagram of the second embodiment, and FIG. 7 is a diagram showing an example of a histogram of the second embodiment. 1... X-ray tube, 2... system, 3...
A/D converter, 4... image memory, 5... positional deviation detection circuit, 6... superimpose processing unit,
7... Display system, 8... Monitor, 17... Subtraction circuit, 100, 200... Analysis circuit.

Claims (1)

[Claims] 1 X that can superimpose the image recorded in the image memory and the fluoroscopic image being taken and output it on a monitor
The line image display device performs arithmetic processing between the vascular contrast agent-containing image recorded in the image memory and the fluoroscopic image, and uses the result of this calculation to display a difference between the vascular contrast agent-containing image and the fluoroscopic image. 1. An X-ray image display device comprising: a positional deviation detection circuit that detects a positional deviation; and an output processing section that switches a monitor output from a superimposed image to a fluoroscopic image under the control of this positional deviation detection circuit.