JPH08339440A - Image processing method, image processor and x-ray fluoroscopic system - Google Patents

Abstract

PURPOSE: To provide an image processing method an image processor and an X-ray fluoroscopic system capable of having a recursive filter function and an image holding function composed of common constituent elements. CONSTITUTION: This processor is provided with a subtracting means 114 which finds the differences between the input image data of a current frame and the output image data of the last frame, a 1st converting means 111 which has bipolar conversion characteristics, a 2nd converting means 112 which have unipolar conversion characteristics, a selective input means 116 which selectively inputs the output data of the subtracting means 114 to the 1st converting means 111 and 2nd converting means 112, a selective output means 117 which selectively outputs the output data of the 1st converting means 111 and the output data of the 2nd converting means 112, and an adding means 115 which finds the output image data of the current frame by adding the output data of the selective output means 117 and the output image data of the last frame.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing method, an image processing apparatus and an X-ray fluoroscope. More particularly, the present invention is a recursive filter.
An image processing method, an image processing apparatus, and an X-ray fluoroscopic apparatus capable of holding image data by utilizing the.

[0002]

2. Description of the Related Art In an X-ray fluoroscope, a fluoroscopic image of an object is captured by an image intensifier.
r) to enhance it and use it as a TV camera
I'm trying to get a picture for display by shooting at. At that time, image data is processed by a recursive filter in order to obtain an image with reduced noise.

The processing content of the recursive filter is expressed by the following equation.

[0004]

[Equation 1]

Here, D: output image data I: input image data a, b: coefficient (a + b = 1) i: frame number That is, the processing by the recursive filter is the same as the output image data of the previous frame. This is a process of adding the input image data of the frame with the same pixels with a predetermined weight to obtain the output image data of the current frame. The output image data of the previous frame is read from the storage device. Since the noise included in the input image data is random between frames, the noise can be effectively reduced and the SN can be improved by such processing by the recursive filter.

The X-ray fluoroscope is provided with a so-called last image hold function which keeps the last fluoroscopic image even after the X-ray irradiation is stopped. As an application of this last image hold function,
Before performing the actual fluoroscopy, a trial X-ray irradiation is performed for a short time to retain the fluoroscopic image, and the fluoroscopic image is examined to determine the fluoroscopic conditions (X-ray intensity etc.) during the actual irradiation. . This is called exposure monitoring.

When performing last image hold or exposure monitoring, a storage device is used to hold the fluoroscopic image even after the X-ray irradiation is stopped.

[0008]

In an X-ray fluoroscope having a recursive filter and having an image holding function, storage of output image data for the recursive filter F and holding of the image data are separately performed as shown in FIG. Storage devices MB and ML. This requires a storage device for each and the controller CNT also needs a means to control the storage device ML for last image hold or exposure monitoring.
It has many components.

This is a problem common to not only the X-ray fluoroscopic apparatus but also an image processing apparatus that performs recursive filtering and holds an image of image data of a subject.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an image processing method, an image processing apparatus, and an X-ray fluoroscope which can realize a recursive filter function and an image holding function with common components. It is to be realized.

[0011]

The first means for solving the above-mentioned problems is to find the difference between the input image data of the current frame and the output image data of the previous frame for an image obtained by photographing a subject, The difference data is converted by a conversion characteristic that can be switched between a unipolar conversion characteristic and a bipolar conversion characteristic, and the converted image and the output image data of the previous frame are added to output the output image of the current frame. An image processing method characterized by obtaining data.

A second means for solving the above-mentioned problems is a subtraction means for obtaining a difference between the input image data of the current frame and the output image data of the previous frame for an image obtained by photographing a subject, and a bipolar means. First conversion means having conversion characteristics, second conversion means having unipolar conversion characteristics, and output data of the subtraction means is converted by either the first conversion means or the second conversion means. Selecting means for selecting whether or not to add, the output data converted by the converting means selected by the selecting means of the first converting means and the second converting means, and the output image data of the previous frame are added. The image processing device is characterized by further comprising: an addition unit that obtains output image data of the current frame.

A third means for solving the above-mentioned problems is an X-ray irradiating means, an X-ray image forming means for forming an X-ray image irradiated from the X-ray irradiating means and transmitted through a subject, and the X-ray. An X-ray fluoroscope having image data forming means for forming input image data of a plurality of frames for an X-ray image formed by the image forming means, and display means for displaying output image data is obtained by photographing a subject. Subtracting means for obtaining the difference between the input image data of the current frame and the output image data of the previous frame for the captured image, a first converting means having a bipolar conversion characteristic, and a second converting means having a unipolar conversion characteristic. Converting means, selecting means for selecting which of the first converting means and the second converting means the output data of the subtracting means is converted, the first converting means and the second converting means means X is provided with an addition unit that obtains output image data of the current frame by adding the output data converted by the conversion unit selected by the selection unit and the output image data of the previous frame. It is a fluoroscope.

[0014]

According to the first means for solving the problem, the output image data of the previous frame is held by converting the data of the difference between the input image data of the current frame and the output image data of the previous frame with a unipolar conversion characteristic. Then, recursive filtering processing is performed by converting with the bipolar conversion characteristic.

In the second and third means for solving the problems, recursive filtering is performed by utilizing the bipolar conversion characteristic of the first conversion means in accordance with the switching of the input / output data by the switching input means and the switching output means. Processing is performed and the output image data of the previous frame is held by utilizing the unipolar conversion characteristic of the second conversion means.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an image processing apparatus according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a configuration of an X-ray fluoroscopic apparatus according to an embodiment of the present invention. The image processing method of the embodiment of the present invention is shown by the operation of the apparatus of the embodiment of the present invention.

First, the X-ray fluoroscopic apparatus according to the embodiment of the present invention will be described with reference to FIG. The X-ray generator 1 irradiates the subject 2 with X-rays. This X-ray generator 1
Is an embodiment of the X-ray irradiation means in the present invention. The table 3 carries the subject 2. The table 3 is made of a material that is transparent to X-rays, such as carbon fiber or aluminum, and is driven by the table feed mechanism 4 so that it can move two-dimensionally along the table surface. Has become. The position detector 5 detects the position of the table 2.

The image intensifier 6 enhances the fluorescent image by the X-rays which has been transmitted through the subject 2 and the table 3 and is incident by photoelectron multiplication. The image intensifier 6 is an embodiment of the X-ray image forming means in the present invention.

The TV camera 7 photographs the output image of the image intensifier 6 and outputs an analog video signal obtained by decomposing the photographed image with scanning lines. The analog video signal has a predetermined frame rate (frame r
ate) Output at 30 Hz, for example. The TV camera 7 is an embodiment of the image data forming means in the present invention.

The support base 8 supports the table 3 and houses the table feed mechanism 4, the position detector 5, the image intensifier 6 and the TV camera 7 in the lower space.

The image input device 10 converts an analog video signal supplied from the TV camera 7 into digital image data to form a frame of the input image data, and the input image data is recursive filter device for each pixel. 11 is input. The image input device 10 is an embodiment of the image data forming means in the present invention.

The recursive filter device 11 performs recursive filtering processing on input image data. The recursive filter device 11 will be described in detail later.

The display device 13 is a recursive filter device 1.
The image is displayed based on the output image data of No. 1. The display device 13 is an embodiment of the display means in the present invention. The control device 15 includes an X-ray generator 1, a table feed mechanism 4, an image input device 10, and a recursive filter device 1.
1 and the operation of the display device 13. The position signal of the table 3 is input from the position detector 5 to the control device 15. The operation device 16 is operated by an operator and gives a command to the control device 15.

Next, the recursive filter device 11 will be described with reference to FIG. Subtraction device 114 data of the difference between the output image data D _i-1 of the previous frame supplied from the input image data I _i and image buffer device 113 of the current frame supplied from the image input unit 10 Δ (= I _i -D _{i- 1} )
Is to seek. The subtracting device 114 is an embodiment of the subtracting means in the present invention.

The image buffer device 113 controls the input image data I of the current frame under the control of the controller 15.
and outputs the output image data D _i-1 of the previous frame corresponding to _i.

The switching device 116 converts the difference data Δ into a look-up table device 111 or 112.
The input is switched to. The switching of the switching device 116 is controlled by the control device 15. Switching device 11
6 is an embodiment of the selecting means in the present invention.

Look-up table devices 111, 112
Respectively have a look-up table, which is used to convert the input data Δ given from the subtraction unit 114 into the output data kΔ (= k (I _i −D _i−1 )). k is a conversion coefficient. Such lookup table devices 111 and 112 are, for example, ROM (read only mem)
ory). Of course RAM (random access m
emory) so that the conversion coefficient k can be freely rewritten.

The look-up table device 111 is an embodiment of the first conversion means of the present invention. The look-up table device 112 is an embodiment of the second conversion means of the present invention.

The input / output conversion characteristic of the look-up table device 111 is set to be a linear function as shown in FIG. 3, for example. The slope of this linear function is the conversion coefficient k. k is set to 1 or less. When the coefficient is set to 1, the input / output characteristic is that the input data Δ is output as it is.
This condition is called through.

The input / output characteristics of the look-up table device 112 are determined so that the output becomes a linear function for a positive input and the output is 0 for a negative input, as shown in FIG. Is determined to be. This is called a unipolar conversion characteristic. On the other hand, the conversion characteristic of FIG. 3 is called a bipolar conversion characteristic.

The switching device 117 selectively outputs the output data kΔ of the look-up table device 111 or 112. The switching of the switching device 117 is controlled by the control device 15. The switching device 117 is an embodiment of the selection means in the present invention.

The adder 115 obtains the sum of the output image data D _i-1 of the previous frame supplied from the output data kΔ image buffer device 113 selected by the switching device 117, an output image data D _i of the current frame To form. The adding device 115 is an embodiment of the adding means in the present invention. The output image data D _i of the current frame is stored in the image buffer device 113 under the control of the control device 15.

The output data of the adder 115, that is, the output image data D _i of the current frame is expressed by the following equation.

[0034]

[Equation 2]

The equation (2) has the same format as the equation (1) and indicates that the recessive filtering is performed. Comparing equation (2) with equation (1), coefficient (1-k)
And k correspond to the coefficients a and b, respectively. It goes without saying that the sum of both coefficients is 1. The smaller the coefficient k, the larger the influence of the output image data D _i-1 of the previous frame and the smaller the influence of the input image data I _i of the current frame, and the stronger the effectiveness of the recursive filter.

When the coefficient k is 1,

[0037]

(Equation 3)

Then, it becomes a through. When k is 0,

[0039]

[Equation 4]

Then, the output image data D of the previous frame
_i-1 is retained. Next, the operation of the apparatus according to the embodiment of the present invention will be described. The X-ray emitted from the X-ray generator 1 is the subject 2
Then, the light passes through the table 3 and enters the image intensifier 6. The fluorescence image by the incident X-ray is intensified by the image intensifier 6 and photographed by the TV camera 7, and a predetermined frame rate (for example, 30H).
It is input to the image input device 10 as a z) analog video signal.

The image input device 10 forms digital input image data from an input analog video signal. Input image data is formed for each frame. The image data I _i of the current frame is input to the recursive filter device 11 for each pixel.

In the recursive filter device 11,
The output image data D _i-1 of the previous frame is read from the image buffer device 113 for each pixel in the same order as the image data I _i of the current frame. The output image data D _i-1 is given to the subtracting device 114, the adding device 115 and the display device 13.

The display device 13 displays an image based on the output image data D _i-1 . The subtraction device 114 obtains the difference data Δ between the image data I _i of the current frame and the output image data D _i-1 of the previous frame. The difference data Δ is the switching device 11
The output data kΔ is converted by the look-up table device 111 or 112 in accordance with the switching state of 6, 117.

When performing X-ray fluoroscopy, the switching devices 116, 1
Reference numeral 17 is switched to the a-contact side, and is converted by the look-up table device 111 according to the input / output characteristics shown in FIG. In the input / output characteristic of FIG. 3, since the conversion coefficient k is constant regardless of whether the input data is positive or negative, the difference data Δ
Regardless of whether the polarity is positive or negative, it is converted into output data kΔ proportional to it. Generally, the conversion coefficient k is 1
Since it is determined to be smaller, the output data kΔ is smaller than the input data Δ.

Such output data kΔ is added by the adder 11
5 is added to the output image data D _i-1 of the previous frame to obtain the output image data D _{i of the} current frame as given by the equation (2), that is, the output image data subjected to the recursive filtering process.

The output image data D _i of the current frame is stored in the image buffer device 113. Image buffer device 11
The output image data of the current frame stored in 3 is output to the display device 13 in the next frame. Such an operation is repeated for each frame, and the display device 13 displays the X-ray fluoroscopic image subjected to the recursive filtering process.

Next, the operation when performing the last image hold will be described. An operation explanatory diagram is shown in FIG.
The operation device 16 is operated and the operation signal I is turned off. When the operation signal I is turned off, the control device 15 switches the switching devices 116 and 117 to the b contact side, and turns off the X-ray irradiation control signal III when the switching state signal II is confirmed. As a result, the X-ray generator 1 stops the X-ray irradiation (X-ray irradiation IV), and the fluoroscopy of the subject 2 ends.

When the switching devices 116 and 117 are switched to the b-contact side, the difference data Δ is converted by the look-up table device 112 according to the input / output characteristics as shown in FIG. In the input / output characteristics of FIG. 4, the conversion coefficient is
When the input data is positive, 0 <k <1, and when the input data is negative, k = 0.

Since the X-ray irradiation is stopped, the input image data I _i of the current frame is the output image data D _i-1 of the previous frame.
It gets smaller. Therefore, the difference data Δ becomes negative, and conversion is performed with the conversion coefficient k = 0. Therefore, the output image data D _i of the current frame is given by the equation (4). That is, the output image data D _i of the current frame is held at the same value as the output image data D _i-1 of the previous frame, and the last image hold is performed.

Also during exposure monitoring, a fluoroscopic image for monitoring is held by stopping the X-ray irradiation in the same procedure as above after the trial X-ray irradiation. Although the present invention has been described by taking the X-ray fluoroscope as an example,
The present invention is not limited to X-ray fluoroscopy equipment, and radiation other than X-rays,
It can be implemented in various image capturing devices that capture an object using various waves or physical phenomena such as light, electromagnetic waves, and ultrasonic waves.

The unipolar conversion characteristic of the look-up table device 112 may be the characteristic shown in FIG. 6 instead of the characteristic shown in FIG. With such a characteristic, the image is held when the difference data Δ becomes positive. In this case, contrary to the above case, the input image data I _i
Image hold works when is increased.

Further, the look-up table device described as the embodiment of the converting means is preferable in that desired input / output characteristics can be easily realized, but the look-up table device is not necessarily limited to the look-up table device. It may be any as long as it produces an output signal having a predetermined functional relationship with the input signal.

Further, the input / output characteristic of the converting means is shown as a linear one by a linear function, but the input / output characteristic is not necessarily limited to this, and may follow an appropriate curve.

[0054]

As described in detail above, the present invention provides
It is possible to find the difference between the input image data of the current frame and the output image data of the previous frame for the image obtained by shooting the subject, and switch the difference data between the unipolar conversion characteristic and the bipolar conversion characteristic. Since the output image data of the current frame is obtained by adding the converted image and the output image data of the previous frame by the conversion characteristic, the recursive filter function and the image holding function are common components. The image processing method, the image processing device, and the X-ray fluoroscope that can be realized can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an apparatus according to an embodiment of the present invention.

FIG. 3 is a diagram showing input / output characteristics of a look-up table device according to an embodiment of the present invention.

FIG. 4 is a diagram showing input / output characteristics of the look-up table device in the embodiment of the present invention.

FIG. 5 is an operation explanatory diagram of the embodiment of the present invention.

FIG. 6 is a diagram showing input / output characteristics of the look-up table device in the embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a conventional example.

[Explanation of symbols]

 1 X-ray generator 2 Subject 3 Table 4 Table feed mechanism 5 Position detector 6 Image intensifier 7 TV camera 8 Support stand 10 Image input device 11 Recursive filter device 13 Display device 15 Control device 16 Operating device 111, 112 Look Up table device 113 Image buffer device 114 Subtraction device 115 Addition device 116, 117 Switching device

Claims (3)

[Claims] 1. A difference between input image data of a current frame and output image data of a previous frame of an image obtained by photographing a subject is obtained, and the difference data is used to obtain a unipolar conversion characteristic and a bipolar conversion characteristic. And an output image data of the current frame is obtained by adding the converted data and the output image data of the previous frame. 2. A subtracting means for obtaining a difference between input image data of a current frame and output image data of a previous frame of an image obtained by photographing a subject, and a first converting means having a bipolar conversion characteristic. , Second conversion means having a unipolar conversion characteristic, and the output data of the subtraction means to the first conversion means.
Selecting means for selecting which of the converting means and the second converting means to convert, and converting by the converting means selected by the selecting means of the first converting means and the second converting means. An image processing apparatus comprising: an addition unit that obtains the output image data of the current frame by adding the generated output data and the output image data of the previous frame. 3. An X-ray irradiating unit, an X-ray image forming unit that forms an X-ray image irradiated from the X-ray irradiating unit and transmitted through a subject, and an X-ray image formed by the X-ray image forming unit. In the X-ray fluoroscope having image data forming means for forming input image data of a plurality of frames and display means for displaying output image data, the input image data of the current frame for the image obtained by photographing the subject And subtraction means for obtaining the difference between the output image data of the previous frame, a first conversion means having a bipolar conversion characteristic, a second conversion means having a unipolar conversion characteristic, and output data of the subtraction means. Selecting means for selecting which of the first converting means and the second converting means is to be used, and the selecting means of the first converting means and the second converting means. conversion An X-ray fluoroscopic apparatus comprising: an addition unit that obtains the output image data of the current frame by adding the output data converted by the unit and the output image data of the previous frame.