JPS58225471A - Apparatus and method for dynamic back ground subtraction - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image acquisition system in the medical field.
More particularly, the present invention relates to an image acquisition system for obtaining a subtracted image 1ψ moving image of a subject, in which an image forming device that generates an image of the subject moves relative to the subject during image generation and storage.

Image acquisition systems for visualization of various blood vessels and systems of the body, such as the cardiovascular system, are widely available. For example, coronary films or angiographic videos are made to visually recognize the morphology and function of coronary vessels. However, the ribs and vertebrae (pack ground)
Coronary vessels cannot be seen due to other structures such as. Therefore, various methods have been devised to reduce background and emphasize regions of interest. For example, photographic or digital subtraction has been used to minimize or eliminate background noise.
(The background subtraction method as commonly practiced generally requires the generation and recording of two images. The first image usually uses a contrast medium to highlight the vessels of interest. generated without

The resulting photograph or film is called scout film. A second image is then generated, the second film being obtained after the contrast medium has been injected into the vascular system so that the arterial vessels are enhanced. The common characteristics of the first and second films are the well-known video (electronic), optical (
photograph) or by subtracting the first film image from the second film image using digital subtraction techniques.

To perform such a subtraction, two adjustments are generally required. The first adjustment is the matching of the first and second films, thereby matching corresponding elements of the two films. This can easily be done by translationally and rotationally moving one of the images that are correlated with each other. If there is a movement of the body between the two images, a more complex internal image may be required.

The second adjustment is to convert the image density values to exposure units. This is desirable because the subtracted image faithfully represents blood vessels regardless of whether the /J knock round is dark or bright.

Of course, the techniques described above are useful in any of many different types of image acquisition systems, such as cinema, video, cut film, computed tomography, scanning or ultrasound image acquisition systems.

Until now, optical or digital subtraction techniques have required an image generator, such as a camera in a projection system or an image intensifier in a television or video system;
Also, the subject (the beach) had to remain stationary relative to each other for the entire time that the first and second film or digitized images were generated. Indeed, one of the problems that existed with conventional subtraction techniques was that the subject needed to be guaranteed to be completely still and motionless for the entire time that the image was generated and stored. Any slight movement between the imaging device and the subject will result in a mismatch between the first and second films, resulting in blurring and an inability to define the subtracted image film. .

Moreover, the above-mentioned discrepancies also hinder the application of subtraction techniques in angiography. This is because, in the case of angiography, it is common for a camera or other device to pan (not move up, down, left or right) during the injection of the contrast medium. By this means it is possible to observe the flow of the contrast medium in the arterial blood without damaging the details. If it is desired to use this panning process, a sufficient amount of contrast medium must be injected into the subject to obtain the desired degree of arterial definition without unacceptable levels of background interference. However, this is a subject
may be dangerous to

Recently adopted processing methods to reduce the risk of using too much contrast medium reduce the amount of contrast medium, take additional photographs of the subject, match and average them, and obtain the desired result. The goal was to obtain a definition of degree. Such a technique is disclosed in the application filed by the same applicant entitled "Angiography Image Averaging Method by Matching Combinations with Serial Images," Application Number: 890.603, Filing Date:
This was the subject of March 27, 1978.

This application is a continuation in part of the above-mentioned application.

Although this technique is very effective, it was directed toward multiple images of a subject in a fixed position relative to the image forming device. Such a system is not suitable when the image forming apparatus is panning a subject.

Of course, various other techniques are known for combining multiple images to obtain a composite image. However, such techniques have not been used in conjunction with image subtraction in which there is relative movement between the image forming device and the subject during the panning process.

The present invention provides an apparatus for detecting motion between an image forming apparatus and a subject, storing the motion, and later copying the motion between the image forming apparatus and the subject to enable frame-by-frame background subtraction. Even if there is a relative movement of , the above-mentioned subtraction can be performed. The invention can be applied to radiography, angiography, CAT (computed tomography), scanning, or other image forming fields.

In particular, the present invention detects the relative position parameters between the image forming device and the subject for a certain period of time in order to completely describe the geometric movement between the image forming device and the subject along the movement path selected by the operator. It consists of a device and a method for recording information.

The position parameters are used to generate commands to drive a serve motor system, which causes the imaging device to move and duplicate the original path of movement by the operator. The image forming apparatus in this text includes a mount for the subject, an irradiation source, and an irradiation receiver, and furthermore, the image forming means is moved in order to perform relative movement between the subject and the irradiation receiver. Includes movement of one or more parts.

According to the invention, a series of first images are recorded to define a first moving image when a movement occurs along a travel path under the control of an operator; A series of second images is defined such that when a continuous movement occurs along the image, a second moving image is defined.

The first and second images can be created instantly with each other. In this case, the first video is created while the contrast medium is in the subject's arterial blood, and the second video is created after the contrast medium has been substantially diluted or disappeared from the arterial blood. .

On the other hand, since the first and second videos can be created with a time interval of several years between them, the subtracted image video emphasizes the changes that have occurred in the time interval between the first and second videos. It becomes a differential video. In the latter case, when a contrast medium is used, which is generally desirable for radiographic images, the first and second motion pictures need to be generated while the contrast medium is in the arterial blood. Otherwise, it is better not to create the first and second videos while the contrast medium is in the arterial blood.

Each frame of the first and second videos is correlated to a particular position along the travel path whether taken with or without a contrast medium; 6. The first video frame is correlated with the corresponding second video frame by orienting the frame according to the correlated position information. On the other hand, for example, the subject's breathing,
Some discrepancies will naturally occur due to movement and cardiac cycles, but techniques such as timing, multiplexing, or projecting the second video at very low speeds can help produce a second video frame that closely matches the first video frame. obtain,
Or you can choose. The invention also allows the use of translational movements, rotational movements, and complex transformations to achieve satisfactory internal frame matching. Similarly, recording information, image enhancement information and step wedge information enable appropriate non-linear subtraction.

The present invention comprises an image acquisition system for obtaining a subtracted variable density video of selected features of a subject when there is relative movement between the open subject being videoed and the light receiving means. A system according to the invention includes: an energy radiation source, such as an x-ray tube; an ultrasound source or other suitable means for illuminating selected features of a subject; It has a means for generating.

The mount for the subject is placed between the irradiation energy source and the light receiving means. When the light receiving means and the pedestal move relative to each other, the position detecting means is interconnected to detect the relative position between the pedestal and the light receiving means (7). Means is provided for selectively changing the relative position between the pedestal and the light receiving means to define a relative movement path, and the position detection means is configured to detect a position representing the relative position along the first relative movement path. Means is provided for subsequently storing the detected position signals and generating position control signals from these stored signals. said position control signal to means for driving either said cradle or said receiving means to change the relative position of said frame, thereby defining a second relative movement path substantially indicative of said first relative movement path; Supplied.

generating a first animation of a variable density image of a selected feature of the subject during relative movement along the first relative movement path; Also included is means for generating a second animation of variable density images of selected features of the subject during the relative movement path. The first video is defined by a plurality of first 7 frames, where each first frame defines a photograph taken at a particular geometric position along the first relative path of movement. Similarly, said second moving image comprises a plurality of second frames, each second frame being provided with means for orienting with a second frame of a particular plane along said second relative movement path. wherein each oriented first and second frame represents a variable density image of a substantially corresponding geometric position relative to the object along the first and second relative movement paths, respectively. Finally, each second room taken along said second path 5 is subtracted from each correspondingly oriented first frame taken along the first path, and the subtracted Means is provided for defining a plurality of variable density frames that are subtracted to define a variable density video.

When a relative movement occurs between an image forming apparatus including an irradiation source; a pedestal for the object, and an irradiation receiver 7, and the object; a first moving image is generated; an image acquisition system and method for controlling the image forming device to copy its travel path while generating a second moving image. the first and second video frames are then oriented and matched;
Subtracted to obtain a subtracted image video.

In this case, the difference between the first video and the second video is visible.

The resulting subtracted image video can be used in many ways. For example, the device and method are useful in angiography. In this case a contrast medium is injected into the subject,
A first animation is created while the contrast medium is in the patient's or subject's arterial blood. The first moving image can therefore be created, for example, when the image forming means images a stationary subject. In this case only dilute solution contrast media are used. The contrast medium is then generated along the same path of travel once it is sufficiently diluted or has disappeared from the subject's arterial blood. Generally, the second video can be created within a few minutes after the first video is created. The resulting subtracted video is therefore a video of the arterial blood enhanced by the contrast medium flowing through the arterial blood. The subtraction process substantially eliminates density changes due to background images of bone and tissue.

The present invention can also be used to generate subtracted image animations that highlight recurring physiological differences in a subject, such as alterations or treatments of particular organs of the subject. A subtracted image animation showing such differences is obtained by first positioning the subject on the cradle and then moving the illumination receiver and/or cradle along the operator-selected first travel path. This can be done by generating a video of 1. This first animation can be generated with or without a contrast medium in the subject's arterial blood.

After a certain time, hours, weeks, or even years, the subject is again placed on the mount in a position as close as possible to the position when the first video was taken. The travel path initially selected by the operator is automatically copied by the computer control by instructing the irradiator and/or the platform to move, and the travel path previously selected by the operator is automatically copied by the computer control. The selected travel route is selected.

If the first video is taken while the contrast medium is present in the arterial blood, it is desirable that the second video also includes the contrast medium in the subject's arterial blood. Generally, contrast media are utilized when the image acquisition system is radiological. However, it is not used when the imaging device is an ultrasound system. Of course, it is recognized that it is not absolutely necessary to use a radiographic image acquisition system to generate a subtracted video showing differences in an organ of a subject over a period of time.

Specific devices for performing relative movement between the image forming device and the subject are known. For example, the bilateral suspension system manufactured by General Electric Medical Systems Division uses fluorocon (irradiated 7-
)) provides a device that can be positioned along three orthogonal translational axes. Once the fluorocon is positioned, the pedestal moves while the fluorocon remains stationary.

Other systems may also move the illumination receiver along up to three orthogonal translational axes or up to three orthogonal rotational axes. In such systems, the cradle remains stationary and the illumination receiver moves relative to the cradle and the subject. Therefore, by utilizing such a system, an operator can select and move in one or more of six different degrees of freedom.

In addition to moving the cradle, it is also possible for both the irradiation register or the irradiation receiver and the cradle to define a movement and also to move the irradiation energy source. Typically, the radiation energy source is placed on one side of the subject, and the radiation receiver is placed on one side of the subject.
It is placed on the other side of the subject. When the irradiation receiver moves, it is necessary to move the irradiation energy source so that the irradiation receiver is not located outside the energy range emitted from the irradiation energy source.

Although any of a number of different mechanisms can be correlated to obtain the translational or rotational movement of either the irradiation receiver or the pedestal and the appropriate change in position of the required irradiation energy source, as shown in FIG. The system shown and described below provides a stationary pedestal and a movable illumination receiver. In this case, the movement can take place about one or more of three orthogonal translational axes and three orthogonal rotational axes. However, other moving mechanisms are possible according to the invention, and the system of FIG. 1 is merely illustrative of the invention.

Referring to FIG. 1, one exemplary sixty-six stage free system lθ that can be used with the present invention incorporates a pair of elevated spaced stationary rails 12 and 14. A beam 16 is movably attached to the rails 12 and 14, and has an axis 1B parallel to the rails 12 and 14.
Perform translational movement along. End 2 separated from beam 16
A telescope cylinder 20 having a diameter of 4 is movably attached to said beam 16 by any suitable means for translational movement along an axis 22 parallel to beam 16 and orthogonal to axis 18. The telescope cylinder 20 has a remote end 24 to which the illumination receiver 26 is rotatably mounted. The telescope cylinder has an axis 2 perpendicular to both axes 18 and 22.
8 in the vertical direction.

The illumination receiver 26 is located at the end 24 of the telescope cylinder 20.
is rotatably mounted on one or more of up to three orthogonal axes. For example, the illumination receiver 26 is attached to the telescope cylinder 20 and rotates around a vertical axis 28, tilts around a tilt axis 34 perpendicular to the vertical axis of rotation 28, and rotates around both the vertical axis of rotation 28 and the tilt axis 34. Pivot the rotation of the pidet shaft 36 perpendicular to . The specific interconnections and support mechanisms for rotatably mounting the illumination receiver for rotation, tilting, and pivoting about orthogonal axes are known and are not specifically described herein. Of course, it is within the scope of the invention to obtain a rotational movement about one or more rotational axes or a translational movement about one or more orthogonal axes to effect a relative movement between the subject 31 on the cradle 30 and the radiation receiver. It is possible to combine many other mechanisms within.

On the other hand, any of the six-stage freedom systems utilizes a hitherto unknown mechanical device that allows the fourth rotor to selectively move the gantry 30 or the radiation receiver 26, and As the position of the illumination receiver 26 moves along a path, it generates a first animation, and then retraces and orients its path of movement to generate a second animation that can match, and then the first animation. Subtract each frame from
While there is relative movement between the subject 3 and the irradiation receiver 26,
A subtracted video of the subject can be obtained.

According to the invention, therefore, the device illustrated in FIG.
8. The calyx advancement position of the irradiation receiver along 22 and 28 and the axis of rotation 2 during movement of the irradiation receiver by the operator.
The angular position of each of 8, 34 and 36 is detected. In one embodiment, the detection device may be any suitable gas demotor known in the system art. As is well known, servo motors act as signal generators or motors, depending on whether the servo produces rotation in response to an external mechanical force or the motor rotates in response to an electrical signal. be able to. The respective position signals can thus be generated by suitably connecting the servo motors to detect or generate translational and rotational movements along or around the respective translational and rotational axes. This position signal changes over time and represents the path of travel along each axis. By digitizing and storing these signals and then using the stored signals as servo instruction signals, the original travel path selected by the operator can be substantially duplicated.

Thus, referring again to FIG. 1, a suitable rail servo motor 50 may be secured to the movable beam 16 and positioned to engage the stationary rail 12. Thus, as the movable beam 16 moves along the stationary rail, the rail sensor yso rotates and generates a signal indicating the position of the movable beam 16 relative to the stationary rail 12. Such mechanical interrelationships are achieved by means of suitable -hv near gear teeth 13 provided along the rail 12.
Alternatively, it can be obtained by other suitable means.

On the other hand, the position signal can be generated indirectly by suitable sensors. One such indirect sensor can be obtained by a resistive piece placed over the entire length of one of the stationary rails. In this case, the resistive piece has a sloped resistance along its length. Therefore, the pressure 7 runno is fixed to a movable beam and pressurized against a resistive piece.
They can be arranged to complete a circuit. Beam 16
As it moves, the position of the pressurized material changes and the resistance also changes. Therefore, the change in voltage across the resistive strip is caused by the static rail 12
and the position of the movable beam 16 relative to 14.

Similarly, a beam sensor 52 may be secured to the telescope cylinder 20 and engaged with a gear 17 or other mechanism along the movable beam 16 to generate a signal indicative of the position of the telescope cylinder 20 along the movable beam axis 22. can.

Similarly, a cylinder servo 54 is fixed to the telescope cylinder 20 and generates, in response to time, an electrical signal representing the vertical position of the telescope cylinder 20 along the vertical axis 2"8 at each point, thereby causing the vertical It can show the height of the direction.

Similarly, the rotation servo motor 56, the tilt servo motor 58, and the The setter motor 60 can be suitably and conventionally mounted, and the illumination receiver 260 of the rotary shaft 28, tilt shaft 34, and bidet shaft 36, respectively.
A signal indicating angular position can be generated.

Servo motor 50.62. ．． 54.66.5B and 6
The time-varying analogue position signals produced by 0 are interconnected to a suitable analog-to-digital converter 48 which digitizes these analogue position signals. Each digital position signal consists of a series of numbers representing the position of the illumination receiver along a particular axis of movement at a particular instant in time.

In operation, the operator simply grasps the illumination receiver 26 and manually moves it along the desired travel path relative to the subject. As the illumination receiver 26 moves, each of the aforementioned servo motors generates an analog or digital signal indicative of the position of the illumination receiver along each of the three orthogonal translational axes and about each of the orthogonal rotational axes 3'. Occur.

In the present invention, the position signals, both analog and digital, are stored in a suitable memory, such as a combinator memory.

While the operator moves the illumination receiver relative to the subject 31 and generates a position signal, the illumination receiver generates and stores a series of video frames to define a first animation. Each frame of the first moving image is stored using a suitable memory such as a computer core, disk, tape cassette memory, or photosensitive storage medium such as photosensitive film. As discussed above, a second animation is created by the illumination receiver by the system retracing and essentially copying the first path of travel.

Of course, when the first and second videos are created,
It is desirable that the subject on the gantry be in substantially the same position.

An example of this is generally when the first moving image and the second moving image are created in several minutes using the method described above. That is, the first video is taken of the contrast medium of the subject's arterial blood, and the second video is taken after the contrast medium has been sufficiently diluted or cleaned from the subject's arterial blood.

On the other hand, in the case of the second condition mentioned above, the time interval between the occurrence of the first animation and the occurrence of the second animation is several hours, weeks or years, and the difference is due to treatment or deterioration of one human body organ. If indicated, it is necessary to position the subject during the generation of the second animation in substantially the same position as when the first animation was generated. However, according to one aspect of the invention, the subjects need not be placed at exactly the same position on the gantry as long as the approximate positions are substantially the same. In particular, according to the matching method that can be used with this invention, each frame can be moved up, down, left and right, and in fact between two corresponding but slightly offset image frames of the first and second video, respectively. Each frame can be shifted slightly to obtain a match. Therefore, unlike conventional subtraction systems, it is not essential to place the subject at exactly the same position on the gantry in order to obtain matching images. Specific means for obtaining frame coincidence between the first and second images will be described in detail below.

Referring to FIG. 1, previously stored position data is output from computer memory and converted back to a nine time varying analog signal by digital-to-analog converter 48. This analog position signal Hallel Serdemor so, beam?
-i motor 52, cylindrical servo motor 54, rotation servo yl
="56, tilt servo 58 and bit servo 60
f. are interconnected to drive each to cause the illumination receiver to duplicate the original travel path followed by the operator; A second animation is therefore generated and stored in the same way as the first animation was generated; as the illumination receiver retraces the original travel path selected by the operator.

Referring to FIG. 2, the shift-and-done photographic system according to the present invention includes: an irradiation source, such as an x-ray tube 70 providing an x-ray source; a pedestal 72 supporting a subject 74 in a beam of x-rays 76; and an irradiation receiver 78, such as a fluorocon, positioned on the subject 74 to receive the x-rays 76 passing through the subject 74. The irradiation source, the stand, and the irradiation receiver constitute six imaging devices.

Yu. The X-rays passing through the subject are variably attenuated depending on the local thickness of the subject; producing a variable density image of the subject, which is received by the radiation receiver 78. Cine Camera 80 or Video Digitide 109
and a recording device, such as memory 110, generates a first moving image as the illumination receiver and/or cradle is moved along the travel path by an operator.

When movement occurs along the first path of movement, the servo or suitable indirect position sensor 82 moves the mount 72 and therefore the subject 74.
A plurality of position signals are generated indicative of the geometrical position of the illumination register 78 relative to the irradiation register 78. Therefore, each position signal is a digital
It is digitized by an analog converter 84 to define a digitized position signal. These signals are stored in position/meter memory 86. Therefore, the digitized position information stored in the position parameter memory 86 is sequentially output in the same order in which it was stored, and converted into a plurality of analog signals by the digital-to-analog converter 88.

The resulting analog signals are each directed to one of the servo motors to move the illumination register/s 78 and/or the cradle 72 along substantially the same path as the first relative movement path.

The illumination receiver 78 and/or the cradle 72 move in response to the servo 90 to reproduce a first relative movement path. These images are recorded again on the recording device as before to generate a second movie.

In an embodiment in which a cinegraph moving image is generated, the first cinegraph moving image and the second cinegraph moving image are optically matched frame by frame.Therefore, photo subtraction processing is performed frame by frame to generate a subtracted cinegraph moving image. The theory and method of this special photographic subtraction is described in Ac1a Radlologica Diagnosi
s vol, 1 photo subtraction from 161975! The theory of subtractive images” by Hardstedt and Welander.
slg January 17, 1976 1 Photo Subtraction "Technical Theory and Methods" (Hardsted L. Rundelius and Welander) These articles are listed here as references.

On the other hand, the first cinegraph moving image and the second cinegraph moving image can be digitized frame by frame in the Cinegra7 dezotizer 92.

In this case, Cinegra 7 film is divided into an array of pixels, each pixel having a unique x,y coordinate address within the frame, and each pixel having a numerical value representing the irradiation energy density at that pixel coordinate address. ing. Each digitized frame is then stored in memory 94, and each frame of the first cinegraph animation and each digitized frame of the second cinegraph animation is stored in memory 94.

This cinegrapher 77'' digitizer 94 may be, for example, simply a television video camera.

This video camera is used to transfer motion pictures from some film media to electronic or video tube media when the motion pictures are being projected.

Therefore, the video information is
oroseopy: Dlgltal 5ubtra
atlon for Intravenous Angi
ocardiography and arteriog
raphy 'Crummy and others, 1980 1
February AJR: 135, pages 1131 to 1140
Common methods such as those described in can be easily digitized.

The digitized cinegraph motion picture stored in memory 94 and the second cinegraph motion picture stored in memory 94 were filed in co-pending application No. 890,103 on March 3, 1978.
may be matched as described in the No. Therefore, each frame of the digitized first video has the same relative position along its travel path between the imaging device 78 and the subject 74 as the position at which the matched first video frame was generated. The frames of the digitized second video generated at the time are matched.

Such matching can be done manually before cinegraph digitization, so that the first frame of the first cinegraph rough video corresponds to the first frame of the digitized second cinegraph video. do. Each successive frame of the first and second cinegraph videos is similarly matched if the first and second videos are shot at the same film speed.

Such a match naturally yields good results, but subject 7
4, pixels are slightly shifted up or down sequentially in the first and second moving pictures. This is done until the sum of the differences between corresponding pixel densities of the subgroup is minimized.

This subgroup matching is done by computer using a Fortran program named LANDMARK. LANDMARK list is program list A
is shown.

As adjacent subgroups of pixels are overlapped or separated after the individual pixel subgroups are shifted, a second computer program is used to further shift each pixel subgroup up or down, or alternatively. They are usually shifted laterally and placed in different positions. Furthermore, each matched frame of the first and second video appears to be generated at only slightly different geometric positions along the first relative movement path.

Therefore, once the frame-by-frame matching described above is achieved,
It is necessary to provide a means for matching the images of each matched video frame pair. Such correspondence between each frame of the second motion picture and each oriented first motion picture frame is obtained by means of a suitable computer algorithm using processor 96. Thereby, such gaps and superpositions of the subgroups of second video frames can be eliminated.

This process can similarly be accomplished on a computer using a Fortran program named TRANSFOR and a Fortran program named PIR. These program lists are listed in Program List B. By utilizing such a technique, each frame of the second video can be adjusted vertically, horizontally, and υ, and in fact rotated to obtain optical coincidence with the corresponding frame of the first video. It can be twisted.

When the two frames match through the pixel position adjustment process described above, the irradiation energy density of each pixel of each second video frame is calculated from the irradiation energy density of the matched pixel of the corresponding first video frame (linearly or nonlinearly)
Subtracted. This results in a plurality of digitally subtracted video frames, which together define a digitally subtracted video. This digital subtraction is 5
This can be done on a computer using the Fortran subtraction program named UBTRACX. A list of said flowograms is shown in Grodarum List C. This digitally subtracted video may be displayed on a television monitor or other device in a conventional manner.

Of course, digital subtraction of stationary radiographic images is known, and it can be appreciated that such subtraction can be performed linearly or non-linearly. In particular, multiple images are subtracted to produce a composite image that presents features of interest separated from the same features in each of the two images. This is done, for example, in angiography. In this case, a background scout film is first made and then a film of the side of the artery after injection of the contrast medium is made.

By subtracting the scout film from the contrast media film, the background is removed leaving only the image of the arterial blood with the contrast media in it. Such subtraction can be accomplished by analog technology, such as a video system, or by digital technology if represented digitally.

Image density can be calculated as a linear function of irradiation or other illumination energy. A simple linear subtraction is therefore appropriate. This occurs, for example, when the range of concentrations is small. However, in general, 5 has a large density range and is non-linear, so in order to obtain a highly satisfactory subtraction image, it is necessary to employ an appropriate technique.

In particular, the length of a cord passing through a blood vessel is a function of the incident and incident light, which is attenuated when the biological blood vessel is filled with contrast medium.

Referring to FIG. 3, when no contrast medium is presented within the blood vessel and the background is uniform tissue, the incident radiation is attenuated to I8T, in which case ST has radiation that passes only through the tissue. Represents a scout film. In the same case, if the cords in the blood vessel are the same and the blood vessel is filled with a homogeneous mixture of contrast medium and blood vessel, the attenuated radiation is 'CT', in which case CT is the tissue represents a contrast medium that only passes through. If the concentration of the contrast medium is not too high, the length of the cord can be approximated by a linear function '8T'CTmiAT.

If the pack ground is slightly different, ie with bone in the same ray containing the vascular cord, the length of the cord is again approximated by the differential attenuation ■5ll=■cIl=AB. In this case, B means there is bone as part of the pack ground for both the scout film and the contrast media film.

Film density is a nonlinear function of attenuated illumination. As a result, the length of the cord that caused the attenuation differential of AT in the tissue was D8
This produces a film density difference of T-DCT=FT. The equivalent length of the rope in the pack ground containing bone is D8B-D
A film density difference of cB and three FB occurs. Generally F as shown in FIG.

is not equivalent to FB.

If the relationship between density and irradiation is given, the irradiation value I corresponding to the density value can be obtained. That is, I = F(D
) can be expressed as The resulting attenuation difference between the scout film and the contrast medium film provides an unbiased estimate of the relative rope lengths.

This relationship has been demonstrated empirically by the use of at least one contrast media frame, as shown by wedge 85 in FIG. It can be generated empirically.

To obtain the radiation attenuation A from the film density difference F, simply divide the film density difference F by the local induction value of I = F(D). As a result, a value proportional to the length of the rope is obtained no matter what the ground is.

For example, referring to Figure 3, if the image density is a nonlinear function of the radiation from the radiation source, the density value of the entire image will be normalized, so for example, if the density value of the entire image is a scout frame where the pack ground is tissue, The difference in density between part of the scout frame and the overlapped part of the contrast medium frame 0 is the same as the difference in density between part of the scout frame and the overlapped part of the contrast medium frame when the pack ground is bone. . Such normalization is obtained by dividing the difference between D8T-DcT, F, by the slope of the curve I=F(D) at a point along the curve between D8T and DcT. Generally, the slope of the curve 1=F(D) between point DIIT and point DcT is approximately constant. .

Similarly, the density value DdB of the portion of the image passing through the bone is subtracted from the density 1i[ of the matched portion of the scout film to yield the difference FB. Is this the point D8B and the eye? In FD
Dividing by the slope of a point or the average slope of the curve I=F(D) between cB yields the same normalized concentration value.

Such a value is the desired result, since the only difference in both cases is that the illumination passes through different backgrounds.

Referring again to FIG. 2, the first and second animations can be generated directly from the video signal generated by the illumination receiver 78, such as when the illumination receiver 78 is a fluorocon.

In such embodiments, the video signal generated by illumination receiver 78 is transmitted to analog-to-digital converter 1.
09, video frame/position memory 1
10.

To align each digitized first moving video frame with a corresponding second digitized moving image frame, it is necessary to identify the point along the relative travel path at which each frame was generated. One method of storing geometric position data for each video frame is to generate a sample enable signal after each frame is digitized and stored in video/frame position memory 110.

As a result, this sample enable signal causes switch 1 to
12 is closed, position data is sampled and stored in video/frame position memory 110 along with the video information. Thus, each frame of video information stored in memory 110 is correlated with position information that defines the position along the travel path at which the video frame was generated.

Therefore, once the travel path is reconstructed, the video information is generated again and stored in the video/frame position memo IJ I 10 in the same way. Position data is sampled and stored at the end of each frame of the second video.

Sampling the position data for the second video frame may include sampling the digitized command information transferred from the position meter memory 86 to the digital-to-analog converter 88, or otherwise determining the actual position of the illumination receiver. This is done by sampling the digitized position data from the analog-to-digital converter 84 shown.

Sequences of some video frames Once the correlated positions of each frame are generated along the first movement path for the first video and the second video, the frames of the first and second video are similar to those described above. The processor 120
will be processed.

In particular, all frames of the first video can be matched with corresponding frames of the second video.

This match is obtained by comparing the position data stored with the frame pixel data and matching those frames that have substantially the same data as the stored position data, and is determined by comparing these frames with relative movement. It can be seen that they were generated at the same relative position along the path.

Of course, the position data of corresponding frames of the first moving image and the second moving image do not have to be exactly the same. This is position r
- It is also avoided that the evening sampling cannot occur at the same position along the travel path of the first and second moving images. Therefore, the processor 120 can be used to round or chamfer the position data, or otherwise give some degree of freedom to specific position data of the first and second moving images. This results in an unambiguous comparison of the position data, allowing corresponding frames of the first and second videos to be matched.

Once each frame of the first video and the second video is matched, processor 120 can make appropriate match adjustments for one or both of the pairs of matched frames as described above. As a result, linear or non-linear subtraction as described above can be performed.

Note that although in the above example a match was made between the oriented frames of the first video and the second video, the matching routine attached hereto may be used to first match some adjacent video information. By averaging the frames, a first composite video can be generated and used. A second composite video consisting of a plurality of sequential composite frames can be generated and used in a similar manner. In this case, each composite frame combines several adjacent frames of the first video and then
, No. 103, by averaging frames that have been matched using the techniques previously described in connection with No. 103.

Of course, this invention can be modified in various ways without changing the gist of the invention. That is, the invention generates a first animation when the illumination receiver and/or the pedestal moves along a relative movement path, and then moves the illumination receiver and/or the pedestal to the relative movement initially selected by the operator. To provide an apparatus and method for automatically generating a second moving image by following a path. The first and second moving images are subtracted frame by frame after the following 7 direction and matching processing is performed, to obtain a moving image of the subject in which the common ground information disappears and only the difference appears.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram of a system including a plurality of serve motors and sensors that detect relative movement between the image forming apparatus and the mount and enable continuous repetition of the relative movement; The figure is a block diagram of a typical system combined with a cinegraph camera; and FIG. 3 is a graph showing the characteristics of image density versus light intensity. 18.22... Axis, 26... Irradiation receiver, 28.
... Vertical rotation axis, 34 ... Tilt axis, 36 ... - human axis, 30 ... Frame, 31 ... Subject, 50 ...
・Rail servo motor, 52...Beam servo motor, 5
4... Cylindrical serve motor, 56... Rotating search motor, 58° tilt sensor? Motor, 60... Pivot sir & motor, 78... Image forming device, 80...
Cine camera, 88...Digital-to-analog converter, 1
09...Video digitizer, 96...Zorosesa,
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U Mo-1 Prisoner FIG, l Continued from page 1 0 Inventor Robert H. Selzer Published by California, United States 643 McCudden Place, Los Angeles, United States 0 Inventor David H. Blankenhorn Pasadena, California, United States・1165 391 Afton Street

Claims (1)

[Scope of Claims] 1. The apparatus includes an irradiation source, a mount for a subject, and an irradiation receiver, generates an image of a selected feature of the subject, is movable by an operator, and is movable by an operator; an image forming means that moves along an image forming path and causes relative movement between the subject and the irradiation receiver; moving the image forming means so that relative movement between the subject and the irradiation receiver occurs in the image forming path; done along
means for copying said imaging path;
defining a second video when the first set of frames of the image and the relative movement between the subject and the illumination receiver along the imaging path are copied to define a video of means for generating and storing a second series of frames of said images; means for orienting and aligning said first and second moving images frame by frame; and a relative relationship between said illumination receiver and said subject; subtracting the subtracted second moving image from the first moving image frame by frame to generate a subtracted image moving image of the subject when movement occurs in the imaging path; An image acquisition system for generating a subtracted image animation of selected features of a biopsy specimen, comprising: means for generating a subtracted image animation of selected features of a biopsy specimen. 2. The system of claim 1, wherein the radiation source is an X-ray generator and the radiation receiver is sensitive to X-ray energy. 3. The system according to claim 1, wherein the irradiation source is an ultrasound source, and the irradiation receiver is sensitive to ultrasound energy. 2. The system of claim 1 further comprising means for maintaining a constant source exposure level during generation of the second motion picture. 5. The system of claim 1, wherein said first and second moving images are photographically generated and said subtracting means comprises a device for subtracting photographs every seven frames. 6. The system of claim 1, wherein the subject mount is fixed and the illumination receiver is movable to define relative movement to the imaging path. 7. Is the irradiation source fixed and the subject p mount in the image forming path? 2. The system of claim 1, wherein the system is movable so as to define a relative movement. 8. Each first frame and each second frame @1
digitized to define a plurality of first frame pixels of each frame and a second plurality of second frame pixels of each frame, 6 first frame pixels and 6 second frame pixels within the frame. and an irradiation energy concentration value that defines the concentration of energy irradiated to the pixel, the generation storage means further comprising a memory means for storing the irradiation energy concentration value of each pixel, and the subtraction The means further includes means for repeatedly selecting a first frame generated at a selected location along the imaging path and a corresponding second frame generated at substantially the same location overflowing the imaging path; and pixel identification means for subtracting the irradiation energy of each pixel in the selected second video frame from the irradiation energy concentration value of the pixel in the selected first video frame having a corresponding pixel address. Claim 1 characterized in that
System described in section. 9. The means for generating the series of first and second frames comprises: means for generating a series of unprocessed first frames; at least one of the first unprocessed frames; and means for averaging the combined raw first frames to define six first frames. , Section 5, or Section 8
System described in section. 10. The means for generating a series of first frames and a second series of frames further includes a series of unprocessed second frames.
means for generating at least two of said unprocessed second frames; and averaging the matched unprocessed second frames to define a second frame. 9. The system according to claim 1, 5 or 8, characterized in that the system comprises means. 11. The means for generating the series of first and second frames further comprises: means for generating a series of unprocessed second frames; at least two of the unprocessed second frames; and means for averaging the matched unprocessed second frames to define six second frames. system. 12. An irradiation energy source for irradiating the object; means for receiving the irradiation energy and generating a variable density image; a mount for positioning the object between the irradiation source and the light receiving means; a first relative movement path; means for selectively changing the relative position between the mount and the light receiving means in order to define a detection position signal representing the relative position between the subject and the light receiving means along the first relative movement path; position detection means for detecting the relative position between the mount and the light receiving means so that the light receiving means is generated; means for storing the position detection signal; means for generating a position control signal from the stored position signal; said pedestal and said light receiving means to change relative positions therebetween in response to said position control signal to define a second relative movement path that substantially duplicates said first relative movement path; means for continuously driving at least one; generating a first moving image of a variable density image of the subject during relative movement along the first relative movement path;
f. means for generating a second moving image of a variable density image of the subject during relative movement along a second relative movement path;
The first animation has a plurality of first frames, each first frame defining an image at a particular geometric position along the first relative movement path, and the second animation has a plurality of second frames, each second frame having a plurality of second frames;
means for generating said first and second moving images such as to define an image at a particular geometrical position along a relative movement path of; a first seven frames of said first moving image and said second moving image; means for orienting a second frame of a moving image, the six first frames being oriented;
and a second receiver is configured to display a variable density image of a geometrical position substantially corresponding to the subject relative to the first and second relative movement paths. means for orienting two frames; and each correspondingly oriented first frame to define a plurality of subtracted variable density frames to define a subtracted variable density video.
and means for subtracting six second frames from the frames of the subtracted variable density video of the biological subject when there is relative movement of the subject while the video is being taken. Image acquisition system. 13. The system of claim 12, wherein the irradiation energy source is an X-ray generator, and the receiving means is responsive to X-ray energy. 14. The system of claim 12, wherein the irradiation energy source is an ultrasound generator and the receiving means is sensitive to ultrasound energy. 15. defining an array of digitized pixel densities, wherein the received illumination at a plurality of predetermined locations is detected and digitized such that the array defines a digitized video frame; means for selectively moving the image forming means along an image forming path to obtain relative movement between the subject and the image forming means; forming an image on the subject; means for synchronously generating digitized position information representative of the position of the means; means for storing said digitized position information; and; on said movement forming path? continuously and automatically controlling the imaging means in response to the stored digitized position information to substantially retrace the relative movement between the subject and the imaging means during the generating a first successive digitized first 7V-me group during selective movement in said imaging path, and during successive retracing in said imaging path; means for generating a second series of digitized second frames; said first series of digitized first frames and said second series of denotated second frames; means for storing the groups; each digitized first
and a second frame of digitized V-frames are generated, the digitized position information is sampled, and the sampled and digitized position information is respectively stored in each digitized frame. 1 image frame and each digitized second image 7V- frame;
means for indicating a position along the imaging path of a point at which the first frame and the second frame are generated; and following a correspondence between the sampled and digitized position information; generating a subtracted image animation of a biological specimen, comprising a frame and means for orienting the first frame and the second frame in relation to a second frame. image acquisition system. 16. The system according to claim 15, wherein the image forming means is an X-ray image forming device. 17. The system according to claim 15, wherein the image forming means is an ultrasonic image forming device. 18. Using an apparatus having an illumination source, a mount for a subject, and an illumination receiver, the apparatus is moved by an operator, thereby causing relative movement between the subject and the illumination receiver along an imaging path. generating a characteristic image of the selected object; and generating a characteristic image of the selected object such that relative movement between the object and the illumination receiver follows the imaging path to copy the imaging path. moving a forming means; when an operator makes a relative movement between the subject and the illumination receiver to define the image forming path, moving the series of images so as to define a first animation; a first frame and a second series of said images such that relative movement between said subject exposed to said imaging path and said irradiation register defines a second motion picture when copied; generating and storing frames; orienting and matching the first animation and the second animation frame by frame; and subtracting a second animation to generate a subtracted image animation of the object when relative movement between the object and the illumination receiver occurs along the imaging path; A method for generating a subtracted image video of selected features of a biological specimen characterized by: 19. The method further comprises the step of: maintaining a constant illumination source exposure level during generation of the first moving image and during generation of the second moving image. The method described in section. 20. The method of claim 18, wherein the first and second motion pictures are photographically generated and the subtracting step comprises frame-by-frame photographic optical subtraction. 21. The image generating step further comprises the steps of fixing the mount of the subject, moving the irradiation receiver, and defining relative movement along the image forming path. The method according to scope item 18. 22. The image generation step further comprises the steps of fixing the irradiation receiver, moving the mount of the subject, and defining relative movement along the image forming path. The method according to scope item 18. 23. digitizing each first video frame and each second video frame and defining a plurality of first frame pixels for each first frame and a plurality of second frame pixels for each second frame; Each first frame pixel and each second 7-frame pixel is defined by an address indicating a position within the frame and a light density value to define the concentration of irradiation energy from the irradiation source that irradiates the pixel. and the step of generating and storing further comprises the step of storing an irradiation energy concentration value for each pixel, and the step of subtracting further comprises a step of storing a first frame generated at a selected position along the imaging path. and a corresponding second seven frames generated at substantially the same location exposed to the imaging path; a pixel in the selected first video frame having a corresponding pixel address; 19. The method of claim 18, further comprising the step of subtracting a pixel illumination energy concentration value for each pixel in the selected second video frame from the pixel illumination energy concentration value. . 24. Generating a series of first and second frames comprises: generating a series of unprocessed first frames; matching at least two of said first unprocessed frames; and averaging the matched unprocessed first frames to define the famous handwriting 1 frame. , or the method according to paragraph 22. 25. Generating a series of first and second frames comprises: generating a series of unprocessed second frames; and matching at least two of said unprocessed second frames. and means for averaging the matched unprocessed second frames to define each second frame. Method described. 26. The step of generating a series of first and second frames comprises generating a series of unprocessed second frames; matching at least two of said unprocessed second frames; and averaging the matched raw second frames to define each second frame. 27, where the subject is a biological vessel amenable to injection of a contrast medium, injecting the subject with a contrast medium immediately before generating the first animation, whereby the contrast medium is injected into the subject; the first moving image being a moving image of the contrast medium as it passes through the subject; and the second moving image after the contrast medium disappears from the subject.
claim 18, further comprising the step of: generating a video of the second video, whereby the second video is taken when there is substantially no detectable contrast medium within the specimen. Method described. 28. The step of generating and storing the generated second video results in an extended time period after performing the step of generating and storing the first video, and the resulting subtracted image video is 19. A method as claimed in claim 18, characterized in that only image differences that occur during an extended period of time are shown. 29. The method further comprises the step of injecting a contrast medium into the subject immediately before generating both the first moving image and the second moving image.
The method described in Section 8. 30. The radiation source is an X-ray generator, and the first and second moving images are generated by X-rays interacting with selected features of the subject. The method according to item 18. 31. The irradiation source is an ultrasound generator, and the first and second moving images are generated from ultrasound waves interacting with selected features of the subject. 3 foxes (described in Section 1S). 32, an image forming means having an irradiation source, a mount for a subject, and an irradiation receiver, and generating a characteristic image of a selected subject, said image forming means being movable by an operator υ, so that said operator The subject and the irradiation register along the image forming path selected by
means for moving the image forming means so that relative movement between the subject and the irradiation receiver is made along the image forming path and copying the image forming path; a series of first image frames defining a first animation when an operator makes a relative movement between the subject and the illumination receiver to define the imaging path; means for generating and storing a second series of image frames defining a second animation when relative movement between the subject and the illumination receiver is copied; means for orienting and matching frame by frame; and subtracting the oriented second moving image from the first moving image frame by frame; and means for generating a subtracted image animation of a selected feature of a subject.