JPH0910197A - Rotating perspective image display - Google Patents

Abstract

(57) [Abstract] [Purpose] To improve the unnaturalness when continuously displaying perspective images with different angular directions. [Structure] Each of the perspective images in the adjacent angle direction read from the image recording device 42 is reduced by the image reduction device 43 in the rotational arc direction by multiplying the cosine of the angle of the difference from the interpolation angle, and by the image shift device 44. It shifts little by little and sends it to the adder 46 through the multiplier 45, adds all the shifted ones, and writes it in the image memory 47.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for displaying a rotary fluoroscopic image obtained by a rotary X-ray fluoroscopic apparatus.

[0002]

2. Description of the Related Art A rotary X-ray fluoroscope is an apparatus for rotating an X-ray imaging system around a subject (patient) to obtain X-ray fluoroscopic images from respective directions. Here, the X-ray imaging system usually includes an X-ray tube, an image intensifier arranged opposite to the X-ray tube, and a television camera optically coupled to the image intensifier. An X-ray tube, an image intensifier, and the like that form this X-ray imaging system are attached to the rotating frame and rotate around the patient. If the video signals of the obtained X-ray fluoroscopic images from the respective directions are sent to the image monitor device and continuously displayed, it is possible to observe the image as if it were seen through while rotating the viewpoint around the patient, and thus the stereoscopic image in the body is seen. Easy to grasp.

In particular, when angiography is performed by this rotary X-ray fluoroscope, it is useful for grasping the three-dimensional structure of blood vessels. This is usually performed in combination with converting a video signal into digital image data and performing various kinds of image processing, and is therefore called rotational DA (digital angiography).

DSA (Digital Subtraction Angiography) is also performed using this rotary X-ray fluoroscope (referred to as rotary DSA). This is because in angiography, image data in each direction is obtained in the state of non-injection of the contrast agent, and this image data is subtracted from the image data in each direction at the time of injecting the contrast agent to obtain only the blood vessel portion. The extracted image is obtained in each direction. Since this rotated DSA image is an image of only the blood vessel portion viewed from each direction of the patient, if it is displayed continuously in the rotational direction, the three-dimensional grasping of the blood vessel is much easier.

Thus, when displaying a rotary fluoroscopic image (including a rotary DA image and a rotary DSA image) obtained by the rotary X-ray fluoroscope, if the fluoroscopic images obtained for each fluoroscopic angle are continuously displayed as they are, If the angle interval is large, smooth display cannot be performed. Therefore, conventionally, in the case of continuously displaying a rotary perspective image, an interpolated image is created and displayed as an image of an intermediate angle. As this interpolation method, a simple linear interpolation method is used. That is, two perspective images from adjacent angular directions are weighted by the angle to be displayed and interpolated.

[0006]

However, the conventional linear interpolation method is not suitable as a method for interpolating a rotational perspective image, and there is a problem that only a jerky and unnatural image can be obtained.

That is, for example, as shown in FIG. 2, the point P is projected on the right side of the image receiving surface 51 in the perspective direction of the angle θ1, but the same point P is left side of the image receiving surface 52 in the perspective direction of the different angle θ2. Projected on. Therefore, as shown in FIG. 4, the image that appears on the right side in the perspective image 61 at the angle θ1 appears on the left side in the perspective image 62 at the angle θ2. When the interpolated image 63 is obtained by the conventional simple linear interpolation method, the above-mentioned left and right separated images both appear in the interpolated image 63,
However, when the interpolation angle θ is close to θ1, the image on the right side is dark and the image on the left side is thin, and when the angle θ is close to θ2, the opposite is true.

As described above, in general, if the perspective directions are different, even objects at the same position (unless they are located at the center of rotation)
Although they appear at different positions, in the conventional interpolation method, the difference in the positions is not interpolated at all, and it is merely the adjustment of the light and shade of the image. Therefore, when the perspective image 62 is displayed after the perspective image 61, even if the interpolation image 63 is displayed in the meantime, the image that was on the right will fly to the left, which will be jerky.

In view of the above, the present invention eliminates the positional discontinuity between the originally adjacent perspective images in the angular direction, and is jerky when the perspective images are continuously displayed in the rotational direction. An object of the present invention is to provide a rotary perspective image display device that can eliminate unnaturalness.

[0010]

In order to achieve the above object, in a rotary perspective image display device according to the present invention, an image for creating an interpolation image in a new angular direction between the angular directions of adjacent perspective images. The interpolation means reduces each of the perspective images in the adjacent angular directions in the rotational arc direction by an image reducing means that reduces the angle difference between the new angular direction and the angular difference between those angular directions by cosine. It is characterized in that it comprises means for adding while gradually shifting the images in the direction of the rotation arc.

[0011]

By using only the information on the original space represented by the perspective image in a certain angle direction, a new interpolated image in a different angle direction is reconstructed. The interpolated image is completed by creating and adding the interpolated image for each original perspective image. This interpolated image is like stretching the original perspective images in the direction of the arc of rotation and overlapping them, so it is possible to eliminate the discontinuity in the position between the original perspective images. The transition from one perspective image to the other can be naturally displayed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the drawings. In FIG. 1, a subject 10 is laid on a top plate of a bed, and an X-ray tube 21 and an image intensifier 22 are arranged so as to sandwich the subject 10. The X-ray tube 21 and the image intensifier 22 are fixed to both ends of a C-shaped arm (rotating frame) 24, respectively. A television camera 23 is optically coupled to the image intensifier 22. The C-shaped arm 24 is the rotation driving device 2
5 and thereby a C-arm 24
It is adapted to be rotationally driven in a circular arc direction (indicated by an arrow). The rotation driving device 25 is held by a stand 26 installed on the floor of the examination room.

The rotation driving device 25 is a control device 31.
The rotation angle is controlled by the control unit 31, and the television camera 23 is also controlled by the control unit 31 for frame synchronization. Therefore, the video signal of the X-ray fluoroscopic image of each frame is output from the television camera 23 at each predetermined angle. This video signal is sent to the image monitor device 33 via the image processing device 32 and an X-ray fluoroscopic image is displayed.

The image processing device 32 includes an A / D converter 41.
When a video signal of an X-ray fluoroscopic image in each direction is sent frame by frame, it is converted into digital image data. The digital image data is sent to the image recording device 42 such as a magnetic disk recording device, and is recorded together with the angle data (representing the perspective direction) sent from the control device 31. When the C-shaped arm 24 is rotated by, for example, 180 °, the image data of all the X-ray fluoroscopic images from the necessary angular direction is recorded in the image recording device 42.

This image data is sequentially read from the image recording device 42 in each direction, reduced in the rotating arc direction by the image reducing device 43, and then gradually shifted in the rotating arc direction by the image shift device 44. Further multiplier 45
Are multiplied by a predetermined coefficient in step S1, then added in order by the adder 46, and stored in the image memory 47. This image memory 47
The image data stored in is read out and the D / A converter 4
The analog video signal is returned by 8 and sent to the image monitor device 33.

Here, as shown in FIG. 2, perspective directions (directions of X-ray beams) θ, θ1, and θ2 are determined. Note that the X-ray beam is parallel for the sake of simplicity. Angle θ
Assuming that the perspective image 61 shown in FIG. 3 is obtained in the direction of 1 and the perspective image 62 shown in FIG. 3 is obtained in the direction of the angle θ2, the perspective image 63 at an intermediate angle θ (θ1 ≦ θ ≦ θ2) is obtained. Will be described. In each perspective image, the rotation arc direction is the X direction, and the direction parallel to the rotation center axis is the Y direction.

First, an image receiving surface (image receiving surface of the image intensifier 22) 51 perpendicular to the X-ray beam in the direction of the angle θ1.
Consider what happens to the image that occurs when the image is viewed from the direction of the angle θ. Since the angle difference between the image receiving surface 51 perpendicular to the angle θ1 and the image receiving surface 53 perpendicular to the angle θ is θ1−θ, the image generated on the image receiving surface 51 is multiplied by the cosine of the above angle difference in the X direction. When the image is reduced in the X direction by using the image, the image formed on the image receiving surface 51 becomes an image when viewed from the direction of the angle θ. Therefore, the image reduction device 43 reduces the perspective image 61 at the angle θ1 by cos (θ1−θ) times in the X direction. In FIG. 2, this corresponds to obtaining a projection image 59 obtained by projecting the image on the image receiving surface 51 onto a surface orthogonal to the angle θ. The projection image 59 is the same as the image receiving surface 53. Is shifted in the X direction by Rsin (θ1−θ). R is the image receiving surface 51
Is the distance from the center of rotation of. The displaced distance is the position in the X direction on the coordinates of the image 63 (FIG. 3) on the image receiving surface 53.

On the other hand, the fact that an image is formed on the image receiving surface 51 means that there is something which forms such an image somewhere in the projection line of the angle θ1. From the image on 51, it is not possible to know where on the projection line of the angle θ1. Therefore, there is no choice but to treat it as being evenly present on the projection line on the image receiving surface 51. That is, it is considered that the image on the image receiving surface 51 is thinned by 1 / (2N + 1) on (2N + 1) planes at equal intervals on the projection line of the angle θ1. The number of these (2N + 1) faces is n, and n = 0, ± 1, ±
2, ± 3, ..., ± N. Image receiving surface 51 when n = N
Refers to.

Then, if the images on these (2N + 1) planes are reduced by cos (θ1−θ) times in the X direction in the same manner as the image on the image receiving plane 51, they will be angled. When viewed from the direction of θ, the position of the nth reduced image on the X-coordinate of the perspective image 63 on the image receiving surface 53 is R
sin (θ1−θ) × n / N.

Therefore, the reduced image obtained by the image reducing device 43 is converted by the image shift circuit 44 into Rsin (θ1
−θ) × n / N is shifted in the X direction. This n-
N, (-N + 1), ..., -2, -1, 0, 1, 2, ...
(1/2) {1 / (2N + 1)} is uniformly applied to the image after the shift obtained by sequentially changing (N + 1) and N by the multiplier 45.
Multiply the coefficient of. Then, the image output from the multiplier 45 for each n when n is changed in order is sequentially added by the adder 46. Then, in the image after this addition, the projected images obtained by projecting the respective images on the (2N + 1) planes arranged in the direction of the angle θ1 on the plane orthogonal to the angle θ are directed to the image receiving surface 53 orthogonal to the angle θ. Are projected (superposed) in the X-ray beam direction of the angle θ.

Creating a new image in this way
Only the information of the original space shown in the image 61 on the image receiving surface 51 is used, and the perspective image 63 that will be created on the image receiving surface 53.
It is equivalent to reconfiguring.

Similarly, the perspective image on the image receiving surface 53 is reconstructed from the image information obtained as the perspective image 62 on the image receiving surface 52. That is, the perspective image 62 at the angle θ2 is read from the image recording device 42, and the X-ray image is reduced by the image reduction device 43.
In the X direction by cos (θ2-θ) times, and further shifted in the X direction by Rsin (θ2-θ) × n / N by the image shift device 44. From this image shift device 44,
Shift images in which n is sequentially changed from -N to N are sequentially output, and a uniform coefficient (1/2) {1 / (2N +
1)} and sequentially added by the adder 46 and written in the image memory 47.

Therefore, in the image memory 47, the image reconstructed from the image 61 of the image receiving surface 51 and the image reconstructed from the image 62 of the image receiving surface 52 are superposed (added), and the interpolated image 63 on the image receiving surface 63. Is completed. Since the image obtained from the image 61 and the image obtained from the image 62 are added to form the interpolated image 63, the coefficient of the multiplier 45 is set to 1/2 of 1 / (2N + 1) as described above. Of. The interpolated image 63 created in this way is as if the original images 61 and 62 were expanded in the X direction and added, as shown in FIG. Therefore, the positional discontinuity between the two original perspective images 61 and 62 is eliminated, and the image that appears on the right side of the perspective image 61 on the right side of the screen suddenly appears on the left side of the perspective image 62. Can be improved.

In such processing, the parameters of θ, N and R are set to the image reduction device 43, the image shift device 44 and the multiplier 4.
5, the image data and the angle data recorded in the image recording device 42 can be automatically read out. θ is the angle of the interpolated image, and is determined by how many interpolated images are created during the angular interval of the original image, so the number of interpolated images may be input. It is desirable that N be a sufficiently large value (for example, N
= 256). As a result, the interpolation image is read out from the image recording device 42, and the interpolation image is inserted between the original perspective images read out from the image recording device 42, while the perspective images are successively rotated in the rotation direction in the image monitor device 33. Can be displayed.

When N is set to a large value, the processing time is required. Therefore, when the interpolation image is formed in the image memory 47 and the interpolation image is output and displayed, the frame rate becomes slow. . In this case, it is possible to record the interpolated image in the image recording device 42 once, and after all the interpolated images are prepared, read out from the image recording device 42 and display it.

Further, although the coefficient of the multiplier 45 is uniform in the above, since the range in which the subject 10 exists is usually limited to the distance L from the center of rotation, | n | For n that is {NR / L},
The coefficient of the multiplier 45 may be made relatively smaller than the coefficient when n = 0 to improve the accuracy of interpolation.

[0027]

As described above, according to the embodiment,
According to the rotary perspective image display device of the present invention, by displaying the interpolated image between the angular directions reconstructed from the perspective images in the adjacent angular directions, the perspective images in the original adjacent angular directions are displayed. It is possible to eliminate a certain positional discontinuity and improve the jerky unnaturalness when a perspective image is continuously displayed in the rotation direction.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is a diagram for explaining perspective directions and interpolation.

FIG. 3 is a diagram showing an image obtained in the same example.

FIG. 4 is a diagram showing an image of a conventional example.

[Explanation of symbols]

 10 subject 21 X-ray tube 22 image intensifier 23 TV camera 24 C-type arm 25 rotation drive device 26 stand 31 control device 32 image processing device 33 image monitor device 41 A / D converter 42 image recording device 43 image reduction device 44 Image shift device 45 Multiplier 46 Adder 47 Image memory 48 D / A converter

Claims (1)

[Claims] 1. An image reducing means for reducing each of the perspective images in the adjacent angular directions in the rotational arc direction by a new cosine direction between them and the cosine of the angular difference between those angular directions. And an image interpolating means for creating an interpolated image in a new angular direction between the angular directions of the adjacent perspective images. Rotating perspective image display device.