JPH06225869A - Digital radioscopic image processor - Google Patents

Abstract

PURPOSE:To provide a digital radioscopic image having a proper afterimage in response to the movement of an image, having a good S/N ratio, and particularly useful for the catheter operation in angiography when digital image processing is applied to the radioscopic image. CONSTITUTION:A digital radioscopic image processor is provided with shift quantity detecting means (3, 8-11) detecting the shift quantity between images separated in time and recursive filters (4-7, 12, 14) applying filtering at the prescribed constant in response to the degree of the shift quantity of the images detected by the shift quantity detecting means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a digital fluoroscopic image processing apparatus for performing digital image processing on a fluoroscopic image obtained by a fluoroscopic apparatus such as an X-ray fluoroscopic apparatus.

[0002]

2. Description of the Related Art It has been conventionally known that a recursive filter (recursive or circular filter) is effective for obtaining a good digital fluoroscopic image in a digital fluoroscopic image processing apparatus of this type.

Although this method is effective for improving S / N,
If the image is applied too much, the afterimage will increase, and especially when the support (bed etc.) of the fluoroscopic device and the image system are moved, the afterimage will increase and the image will be difficult to see. Therefore, (1) a method has been proposed in which the filter coefficient is changed depending on whether the support or the image system is moving or not. Further, (2) a method of detecting a partial movement between images and changing the filter coefficient between a moving portion and a non-moving portion is already known.

[0004]

In the above conventional method (1), when the subject itself moves, the movement cannot be detected.
There was a problem that afterimages increased. In addition, in the conventional method (2), X-ray quantum noise is large in general X-ray fluoroscopy, it is difficult to discriminate the movement of the subject or the support and the fluctuation of the data due to the X-ray noise, and the recursive filter is sufficient. There was a problem that it could not be applied. In addition, there is a problem that the movement of the heart originally exists in the vicinity of the heart, so that the movement of the heart is detected and the filter cannot be applied.

An object of the present invention is to provide a digital perspective image processing apparatus capable of appropriately controlling an afterimage according to an image and obtaining a digital perspective image with a good S / N.

[0006]

SUMMARY OF THE INVENTION The above object is a digital perspective image in which an image signal from a television camera is AD-converted and recorded in a frame memory, the image data in the frame memory is DA-converted, and the image is displayed on a monitor. In the processing device, a motion amount detecting unit that detects a motion amount between images that are temporally preceding and following, and filters with a constant set in advance according to the degree of the motion amount of the image detected by the motion amount detecting unit. It is achieved by providing a recursive filter.

[0007]

The motion amount detecting means detects the amount of motion between images that are temporally preceding and following each other. The recursive filter filters with a constant (filter coefficient) preset according to the degree of the amount of motion of the image detected by the motion amount detecting means.

The conventional method (2) of detecting motion and partially changing the constant (filter coefficient) of the recursive filter is not effective for cardioangiography which originally involves motion. Therefore, the motion amount detecting means detects the motion of the subject, which has been a problem in the conventional method (1), by digital processing, and combines it with the motion of the support of the fluoroscopic device to determine the motion amount (content of motion). Then, the recursive filter constant (filter coefficient) is changed, and here, at least three or more steps are changed.

As a result, the filter can be applied even in the region close to the heart, the filter is sufficiently applied to a region having no motion other than the heart, the filter is weakly applied to a region having a pulsation, and when the whole is moving. The recursive filter operates such that no filter is applied, the overall S / N ratio is good, and the afterimage also occurs (or does not occur) to a degree according to the movement of the image.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a digital perspective image processing apparatus according to the present invention.

In FIG. 1, 1 is a television camera. This television camera 1 outputs an output image of an X-ray image intensifier (not shown) as a television signal (image signal).
Convert to.

The image signal from the television camera 1 is converted into image data (digital data) by the AD converter 2,
The image data is recorded in the frame memory 3 and simultaneously in the frame memory 4. The TV signal generated next is AD-converted in the same manner as described above, and then recorded in the frame memory 3 and simultaneously recorded in the frame memory 5.

Similarly, the data is recorded in the frame memory 3, the frame memory 6 and the frame memory 7 at the same time, and then returns to the next frame memory 4. That is, the signal for the TV frame is simultaneously transmitted to the frame memory 3 and
It is cyclically recorded in the order of the frame memories 4 to 7.

Here, since the image data recorded in the frame memory 3 detects the amount of motion of the image between each frame and the preceding frame, the subtraction calculator 8 compares it with the current television signal. 1 pixel at a time, every pixel, for example 51
Subtraction is performed for 2 × 512 pixels, and the amount of change is measured. This change amount is continuously added by the addition calculator 9 for one frame (addition is performed by an absolute value).

The addition result obtained by the addition calculator 9 is recorded in the register 10 for each pixel. When one frame has been added, it is stored in the register 11 as the total motion amount. The addition of the motion amount can be performed by the addition gate circuit GC as in the present embodiment, for example, by performing only the circular area of a predetermined size at the center of the frame (image), thereby limiting the motion detection range. . According to this, it is possible to detect the movement of only the effective range of the X-ray image intensifier, and the precision of the movement detection is improved.

As described above, the image data is sequentially recorded from the frame memory 4 to the frame memory 7, but S
In order to improve / N, the frame memories 4 to 7 are arithmetically averaged. As types of arithmetic average (filter coefficient), there are arithmetic average of four images of the frame memories 4 to 7 and arithmetic average of only two images of the four frame memories 4 to 7, In addition to this, processing of not performing arithmetic averaging can be performed, and three types of filter processing can be selected.

That is, it is possible to obtain an optimum filter by selecting and changing the filtering method from the above three types according to the amount of motion stored in the register 11, which will be described below. To do.

The relationship between the type of motion of the image, the motion amount, and the filter processing is as shown in FIG. As shown in Figure 2,
Since the amount of movement increases when the supporter (bed or the like) of the fluoroscope or the image system is moving, or when the subject is moving, the filter is turned off in this case.
In this state, the subject is moving and it is sufficient to know the movement. If there is an afterimage, the screen will flow and it will be difficult to see, so the addition and averaging process is turned off.

In the case of an image having a pulsation due to the movement of the heart, a certain amount of movement is detected, but it is smaller than when the entire subject moves. As shown in FIG. 2, when a motion amount equal to or less than the pulsation of the heart is detected, the filter is turned on. In the case of an image without a pulsation (a region in which the heart is not shown, for example, an image of the head or lower limbs), X-ray noise becomes a large amount of movement. This X-ray noise amount can be estimated in advance.

Therefore, when the amount of motion associated with the pulsation is detected, the filter is set to weak (the number of images to be averaged is 2), and when the amount of motion is about X-ray noise, the filter is strong (the average of average). Set to 4) the number of images to be printed.

That is, the averaging control circuit 12 reads the contents (movement amount) of the register 11 and, as shown in FIG. 2, the boundaries of the filter OFF region, the filter ON (weak) region, and the filter ON (strong) region. As a result of comparison with a threshold value set in advance, a control signal 13 for four-image image averaging (filter strong), two-image image averaging (filter weak), and no averaging is created, and the averaging processing circuit 14 Control the behavior of.

The image data from the averaging processing circuit 14 is
The DA converter 15 converts the signal into a television signal, and an image is displayed on the television monitor 16.

In the above embodiment, the frame memories 4 to 4 are used.
7. The recursive filter is configured by the averaging control circuit 12 and the averaging processing circuit 14, but the present invention is not limited to this. For example, the present invention can be realized by a recursive filter having a k factor as shown in FIG. In this case, the same effect as that of the above-described embodiment can be obtained by changing the feedback constant k according to the movement amount.

[0024]

As described above, according to the present invention, the optimum filter constant (coefficient) can be automatically changed according to the amount of movement of the entire image, and as a result, the filter constant (coefficient) can be appropriately changed according to the movement of the image. After that, a digital perspective image with good S / N can be obtained.

In other words, an afterimage is minimized in an image with a lot of movement, and an image that is easy to see is obtained (if there are many afterimages, the image will flow and become difficult to see). Also, for images of the heart region, especially for angiography, the catheter must be well visible
Although an appropriate afterimage is required, in the present invention, the pulsation state is detected, an appropriate afterimage is added, and an image that makes the catheter easy to see and an image with good S / N are obtained. Further, afterimages are strongly applied in the case of an image having no pulsation and no motion. For example, in the case of the above-described embodiment, four images are arithmetically averaged, and thereby the S / N is 2 as compared with when the filter is OFF. Can be doubled.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a device of the present invention.

FIG. 2 is a graph showing the relationship between the type of image movement and the amount of movement.

FIG. 3 is an operation principle diagram of another embodiment.

[Explanation of symbols]

 1 TV Camera 2 AD Converter 3 to 7 Frame Memory 8 Subtraction Operator 9 Addition Operator 10 Register 11 Register 12 Averaging Control Circuit 13 Control Signal 14 Averaging Processing Circuit 15 DA Converter 16 TV Monitor GC Addition Gate Circuit

Claims (1)

[Claims] 1. A digital perspective image processing apparatus for AD-converting an image signal from a television camera and recording it in a frame memory, DA-converting the image data in the frame memory, and displaying the image on a monitor. A motion amount detecting means for detecting a motion amount between the images, and a recursive filter for filtering by a preset constant according to the degree of the motion amount of the image detected by the motion amount detecting means. A characteristic digital perspective image processing device.