JPH08321995A - Image diagnostic device - Google Patents

Abstract

PURPOSE: To provide the image diagnostic device by which a mask image and a live image are obtained from an image collected by one movement of an image pickup system. CONSTITUTION: The image pickup system consisting of an image pickup device support 11a driven by an image pickup device support driver 11b, an X-ray tube 1, an I.I.3, and a TV camera 4 supported by the image pickup device support 11a collects plural images while being moved along a body axis of a reagent in following to a flow of a contrast medium injected to veins of the reagent. While the images are being collected, the image pickup position is moved by a prescribed amount for each pickup by the image pickup device support driver 11b. Plural division images are obtained by dividing the images collected by one moving pickup by the image pickup system to be classified into a set of division images in which vein forming images are in existence and a set of division images in which vein forming images are not in existence and the mask image is decided from the set of the latter division images.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image diagnostic apparatus for diagnosing a contrasted blood vessel image.

[0002]

2. Description of the Related Art In diagnosing cardiovascular diseases, angiography (angiography) is carried out by inserting a catheter into a blood vessel of a subject and directly injecting a contrast agent.
Has been done. In addition, digital subtraction angiography is performed to subtract the blood vessel images (mask image and live image) before and after injecting a contrast agent into the subject, making it easier to see the blood vessel portion. It is used. Hereinafter, in this specification, the image thus obtained is referred to as a DSA image.

The blood vessel image (mask image and live image) for performing the subtraction process is a digitized image (digital angio image), and the digital angio image is
For example, an X-ray image obtained by exposing X-rays to
I. (Image intensifier) and a TV camera are used for photographing, and the video signal output at this time is digitized by A / D conversion.

In a conventional example of an image diagnostic apparatus for performing such digital subtraction angiography, a mask image and a live image are individually collected. Further, for example, in the case of performing imaging on a lower limb blood vessel of a subject, since the target blood vessel covers a wide range, imaging is performed while sequentially moving the imaging system according to the flow of the contrast agent. In such angiography involving movement of the imaging system, images of the same position are taken twice in order to obtain a mask image before injection of the contrast agent and a live image after injection of the contrast agent. The movement of the shooting system is controlled.

To move the imaging system, there are a method of moving the catheter bed on which the patient is placed with the imaging support fixed, and a method of moving the imaging support with the catheter bed fixed. In the description, the latter method is used.

Now, the process of capturing a mask image and a live image with the movement of the image capturing system and forming a DSA image will be described in detail. FIG. 10 is a diagram for explaining the shooting order of the mask image and the live image.

First, the mask images (M1, M2, M3) before the blood vessel contrast agent is injected into the subject are sequentially photographed. The movement amount of the photographing system corresponds to one photographing area, and the movement timing is immediately after photographing. When the last mask image (mask image M3 in this case) is photographed, the photographing system is located at the tip of the subject (patient) 30. Therefore, the photographing system moves to the position where the mask image M1 is photographed first.

Next, an image after injection of the blood vessel contrast medium, that is, a live image (L1, L2, L3) is taken. The timing of capturing the live image is when the contrast agent reaches the bottom of the capturing area. From the live images (L1, L2, L3) thus obtained, the mask images (M1, M2,
A DSA image is obtained by subtracting M3).

[0009]

The conventional image diagnostic apparatus for moving the image pickup system and individually collecting the mask image and the live image has the following problems. (1) Since the time interval between capturing the mask image and the live image is long, artifacts (false images) occur in the DSA image due to movement of the subject, etc., and a DSA image with sufficient image quality cannot be obtained. (2) In the case of failing to capture a live image after capturing a mask image, or when it is not possible to capture a live image after the stagnation point of the contrast agent due to the flow of the contrast agent being stopped midway. , It is necessary to start the mask image shooting again. For this reason, the mask image that has already been photographed becomes unnecessary, and as a result, useless exposure is given to the patient or the operator. (3) Collecting the mask image and the live image by moving the imaging system twice makes the examination time longer and increases the burden on the patient or the operator.

The present invention has been made to address the above-mentioned circumstances, and an object thereof is to provide an image diagnostic apparatus for obtaining a mask image and a live image from an image collected by one movement of an imaging system.

[0011]

An image diagnostic apparatus of the present invention comprises a collecting means for moving an imaged region along a body axis of a subject and collecting X-ray images of a plurality of regions of the subject, and the collecting means. There is a dividing unit that divides each acquired X-ray image into a plurality of divided images in a direction intersecting the body axis of the subject, and a blood vessel image in which each divided image obtained by the dividing unit is imaged. The classification means for classifying the divided image and the divided image in which the contrasted blood vessel image does not exist and the mask image corresponding to the divided image in which the contrasted blood vessel image exists in the divided image in which the contrasted blood vessel image does not exist And a subtraction image creating unit that creates a subtraction image based on the divided image in which the contrasted blood vessel image is present and the mask image determined by the mask image determining unit. It is characterized in.

[0012]

According to the image diagnostic apparatus of the present invention, a mask image and a live image can be obtained from an image collected by one moving photographing.

[0013]

1 is a block diagram showing a hardware configuration of an image diagnostic apparatus according to a first embodiment of the present invention. The image diagnostic apparatus according to the first embodiment is an X-ray tube 1 for irradiating a subject (not shown) placed on a catheter bed 2 with X-rays.
And the X-ray tube 1 and the catheter bed 2, which are opposed to each other, detect the X-rays transmitted through the subject and convert the X-rays into an optical image. I. (Image Intensifier) 3 and I.
I. TV camera 4 that captures the optical image output from 3 and converts it into a video signal, and A / D converter 5 that converts the video signal output from TV camera 4 into a digital video signal
And input the video signal output from the A / D converter 5,
It has a frame memory 6 for storing this as an image (digital angio image).

An image processing memory 7 and a mask image storage memory 7a for storing an image obtained by inputting an image stored in the frame memory 6 and subjecting the CPU (central processing unit) 12 to image processing. A subtraction processing device 8 for inputting an image-processed image from the image memory 7 and the mask image storage memory 7a and performing subtraction processing to create a DSA image
And input the DSA image output from the subtraction processing device 8,
D / A converter 9 for converting this into an analog video signal
And a monitor 10 for displaying a DSA image of the analog video signal output from the D / A converter 9.

An input device 13 for inputting an instruction from an operator is connected to the CPU 12, and the photographing support 1
A photographing support driving device 11b for driving 1a is connected. The imaging support 11 is generally called a C-arm because of its shape, and is compatible with the X-ray tube 1 and the I.D. I. 3, and is driven by the photographing support driving device 11b to move.

The apparatus of this embodiment having the above structure is
Although "imaging" is mainly performed in which the X-ray tube 1 is irradiated with relatively strong X-rays to the subject for a short time, "fluoroscopy" in which relatively weak X-rays are irradiated for a long time can also be performed. ing. In addition, the image obtained by “perspective” can be supplied to the monitor 10 and displayed. Further, the perspective image can be digitized by the A / D converter 5 and supplied to the image processing memory 7 for image processing.

FIG. 2 is a flow chart for explaining the outline of the operation of the image diagnostic apparatus according to the first embodiment.
First, in step S1, images are collected. Here, the imaging supporter 11a driven by the imaging supporter drive device 11b and the X-ray tube 1, I. I. An imaging system including the TV camera 3 and the TV camera 4 acquires a plurality of images while moving along the body axis direction of the subject according to the flow of the contrast medium injected into the blood vessel of the subject. During image acquisition, the imaging position is moved by a predetermined amount for each imaging by the imaging supporter driving device 11b controlled by the CPU 12.

As described above, in the conventional apparatus, while the imaging system is moved along the body axis direction of the subject, the imaging-movement is sequentially repeated to collect the mask image, and then the imaging system is set to the imaging start position of the mask image. After returning and injecting the contrast agent, the live image is collected by the second moving image capturing while moving along the body axis of the subject again.
It is intended to obtain a mask image and a live image from the images collected by moving images once. In this example, first, the first image is taken at the imaging start position of the imaging system before the injection of the contrast agent, and then the imaging-movement is sequentially repeated, and the collection is completed by one moving imaging. .

By the way, when collecting an image, if the timing control of imaging (movement) is performed while detecting the flow of the contrast agent in real time, the collection accuracy is improved. That is, fluoroscopy may be performed in parallel with image acquisition, and imaging may be performed while observing (moving) the image based on the angiographic image that appears in the fluoroscopic image by being imaged. Regarding the timing of image capturing, any position may be used as long as the angiographic image is projected from the current image capturing region due to the penetration of the contrast agent. This may be achieved by always recognizing the distal end portion on the fluoroscopic image by a method of automatically tracking an angiographic image described later and obtaining a trigger for imaging at a predetermined position, or the fluoroscopic image displayed on the monitor 10. The operator may visually recognize the image and use the input device 13 to give a trigger for photographing.

The plurality of collected images are converted into an A / D converter 5
Is stored in the frame memory 6 via the. Next, in step S2, the image is divided. First step S
The images collected in 1 and stored in the frame memory 6 are sequentially sent to the image processing memory 7. Hereinafter, processing is performed in the image processing memory 7 until the mask image is determined.

Then, by dividing the image sent to the image processing memory 7 in the direction intersecting the moving direction of the imaging system (direction intersecting the body axis direction of the subject), a plurality of images as shown in FIG. Get the divided images of.

In this embodiment, the image is equally divided into a size equal to the moving amount of the photographing position. In the case of dividing into an arbitrary size instead of equal division, it is only necessary to add a process for making one set of images correspond to the captured image in the time difference process, the subtraction process, and the like, which will be described later.

Next, in step S3, the divided images are classified. Here, each of the divided images divided in step S2 is classified into a group of divided images in which an angiographic image exists and a group of divided images in which an angiographic image does not exist. Here, an example of a method of classifying divided images will be described. As shown in FIG. 4, the first classification method tracks (searches) the tip of the blood vessel on the image, that is, the tip of the angiographic image 20 imaged with a contrast agent, and classifies based on the tracking result. The tip portion of the angiographic image may be tracked using a known blood vessel tracking method. Known blood vessel tracking methods, such as the Chicago University Double Square Box Region of Search method, Reference (Automated
tracking of the vascular tree in DSA images using
a double-square-box region-of-search algorithm: ke
nneth R. Hoffmann, Kunio Doi, Heang-Pin Chan, Laura Fe
ncil, Hiroshi Fujita, Alan Muraki; The Kurt Rossmann
Laboratories for Radiologic Image Research Depart
ment of Radiology, The University of Chicago), a double square box is used and an angiographic image is tracked by tracking points.

Then, in the blood vessel tracking process, the one having the tracking point passing therethrough is determined as the divided image in which the angiographic image exists. For example, in image Ti of FIG. 4, position a,
The divided image at the position b is determined to have an angiographic image because the tracking point of the blood vessel passes or exists, and the divided images at positions c to e are determined to have no angiographic image because the tracking point has never passed or existed. .

Next, another example of classification of divided images will be described. As shown in FIG. 5, the second classification method obtains a time difference image Si for divided images Ti and Ti + 1 obtained by photographing the same part. For this time difference image Si, a profile curve in a direction perpendicular to the moving direction of the imaging system is sequentially obtained from the first line, and it is checked whether or not there is a maximum point above a predetermined threshold value on this profile curve. . This maximum point represents an angiographic image, and when it exists, it can be determined as a divided image with an angiographic image, and when it does not exist, a divided image without an angiographic image. Note that all the other divided images at the positions where the divided images determined to have the angiographic image exist are regarded as having the angiographic image, and the above-described processing for classification is not performed.

Next, in step S4, a mask image is determined from the divided images. More specifically, step S
Among the plurality of divided images obtained by classifying the angiographic image contrasted in 3 as a divided image having no angiographic image and capturing the same region of the subject collected at different time points, the last collected divided image of the divided region of Determined as a mask image for the live image. That is, for the divided image Dt at a certain position of the image Tt obtained at a certain time t, among the divided images Di (i <= t) obtained by photographing the same part as this divided image,
The final divided image in which the angiographic image does not exist is determined as the mask image of the divided image Dt.

The determination of such a mask image will be described with various examples. In FIG. 4 described above, the imaging region is sequentially moved by moving the imaging system (imaging indicator 11a) along the body axis of the subject in accordance with the flow of the contrast agent from the upper side to the lower side in FIG. Multiple images obtained are shown.

For example, focusing on the position e in the figure, the image Ti
There is an angiographic image for the first time at +2. Therefore, the mask image of the divided image at the position e is the divided image at the position e of the previous image before the image Ti + 2, and the divided image at the position e of the image Ti + 1 after the image Ti + 2.

For example, the mask image at the position e of the image Ti + 1 is itself, and the mask image of the divided image at the position c of the image Ti + 2 is the divided image of the position c of the image Ti and the image Ti + 3. Position f
The mask image of the divided image is the divided image at the position f 1 of the image Ti + 1.

The divided image determined as the mask image is sent from the image processing memory 7 to the mask image storage memory 7a,
Stored for later subtraction. Through the above steps S1 to S4, a mask image and a live image can be obtained in units of divided images from the images collected by one-time moving photographing of the photographing system.

Next, in step S5, subtraction processing (subtraction) is performed in the subtraction device 8. Here, the subtraction process is performed on the divided image (live image) in which the angiographic image exists and the set of divided images of the mask image determined in step S4. As a result, a DSA image having the size of the divided image is obtained.

Then, in step S6, the DSA image is displayed. DS obtained in step S5
The A image is supplied to the monitor 10 via the D / A converter 9 and displayed.

By the way, the DSA image created in step S5 is created in units of divided images, and in this embodiment, the DSA images corresponding to the size of the photographing region are obtained by combining the respective DSA images. be able to.

Further, since the DSA image is obtained in units of divided images, it is possible to create a DSA image of a size obtained by arbitrarily multiplying the divided image as a minimum unit. Therefore, for example, it is possible to output an image having a size according to the diagnostic needs, such as wanting to diagnose a wide area of the subject such as a lower limb blood vessel with one diagnostic image (DSA image). If the live image is not captured in the middle, the failed portion may be retaken in units of divided images.

As described above, according to the image diagnostic apparatus of the first embodiment of the present invention, a mask image and a live image can be obtained from an image collected by one movement of the imaging system. Therefore, artifacts due to movement of the subject are reduced, and a DSA image with sufficient image quality can be obtained. In addition, there is no useless exposure to the patient or the operator. Further, the inspection time can be shortened and the burden on the patient or the operator can be reduced.

Next, an image diagnostic apparatus according to the second embodiment of the present invention will be described. In the description of the second embodiment, the same parts as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. In the second embodiment, the size of the divided image is set to half the size of the image obtained by one shot, and the blood vessel structure on the fluoroscopic image obtained by fluoroscopy performed in parallel with the image acquisition. The tip portion of the shadow image is always tracked by, for example, the above-described tracking method, and when the tip portion reaches the center of the fluoroscopic image due to the penetration of the contrast agent, an image is taken and the size of the divided image is increased as shown in FIG. This is different from the first embodiment in that the photographing system is moved by a movement amount equal to the length.

FIG. 7 is a diagram for explaining how to obtain a DSA image from the images thus collected. In the images acquired as in the present embodiment, the angiographic image always exists in the upper half of the image and the angiographic image does not exist in the lower half. Therefore, the acquired image is divided into half sizes to obtain two divided images, the upper half divided image is used as a live image, and the lower half divided image of the image just captured is easily determined as a mask image. can do. Therefore, there are advantages that the processing is simplified and speeded up. However, for example, when the angiographic image is mistakenly photographed when the angiographic image is located at a position other than the center of the fluoroscopic image, it becomes impossible to obtain a set of a mask image and a live image for each divided image, and the collected image On the other hand, it is wasted.

Here, I.D. I. The correction for the image distortion and the geometric distortion by the method will be described. I. I. The correction of the image distortion and the geometric distortion due to is performed in advance on the collected images as a process before the image division. FIG. 8 is a diagram for explaining a problem caused by geometrical distortion. Geometric distortions can occur in X-ray tubes and I.S. I. When and move in parallel, the positions of the subject, the X-ray focal point, and the image receiving surface change, and the magnification of the projected image of the subject, the projection direction, and the like change sequentially. In the figure, in the output image corresponding to the position of the imaging system, the same subject region (a,
The aspects of b) are different from each other. Therefore, there are problems in that the shapes, sizes, and the like are different from each other, and an appropriate diagnostic image cannot be obtained.

Therefore, as shown in FIG. I. Only the X-ray irradiation area is moved to the I.D. I. The X-ray tube is rotated with its position fixed so that it becomes the entrance surface. By collecting images in this way,
As shown in the figure, the same subject parts (a, b) have the same aspect, and it is possible to appropriately perform the subtraction process between the divided images obtained on different image receiving surfaces.

The present invention is not limited to the above-mentioned embodiments, but can be modified in various ways. For example, first, second
In the embodiment, the lower extremity blood vessel of the subject has been described as an example of the diagnosis target, but the diagnosis target is not limited to this.

The tracking of the tip portion of the angiographic image may be performed manually by observing the fluoroscopic image display monitor by the operator. In addition, the I.D. I. For correction of geometrical distortion due to
It may be performed also in the first embodiment. If an external storage device (for example, a disk) is added to FIG. 1 to store the collected images, the image acquisition and DSA can be performed discontinuously in time.

[0042]

As described above, according to the present invention, it is possible to provide an image diagnostic apparatus having the following effects. (1) An image diagnostic apparatus that obtains a mask image and a live image from an image collected by moving the imaging system once. (2) An image diagnostic apparatus in which artifacts due to movement of a subject are reduced and an image with sufficient image quality can be obtained. (3) An image diagnostic apparatus that does not give unnecessary radiation to a patient or an operator. (4) An image diagnostic apparatus that shortens the examination time and reduces the burden on the patient or operator.

[Brief description of drawings]

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

FIG. 2 is a flowchart for explaining the outline of the operation of the image diagnostic apparatus according to the first embodiment.

FIG. 3 is a diagram schematically showing the operation of the first embodiment.

FIG. 4 is a diagram for explaining image division.

FIG. 5 is a diagram for explaining another example of classification of divided images.

FIG. 6 is a diagram for explaining a shooting order of a shooting system according to a second embodiment.

FIG. 7 is a diagram for explaining determination of a mask image and a live image according to the second embodiment.

FIG. 8 is a diagram for explaining a problem caused by geometrical distortion.

FIG. 9 is a diagram for explaining a geometric distortion correction method.

FIG. 10 is a view for explaining the order of capturing conventional mask images and live images.

[Explanation of symbols]

1 ... X-ray tube, 2 ... Catheter bed, 3 ... I. I. (Image intensifier), 4 ... TV camera, 5 ... A /
D converter, 6 ... Frame memory, 7 ... Image processing memory,
7a ... Mask image storage memory, 8 ... Subtraction processing device, 9 ... D
/ A converter, 10 ... Monitor, 11a ... Shooting support, 11
b ... Shooting support driving device, 12 ... CPU, 13 ... Input device.

Claims (6)

[Claims] 1. A collection unit that moves an imaging region along a body axis of a subject to collect X-ray images of a plurality of regions of the subject, and X-ray images collected by the collection unit, A dividing unit that divides the divided image into a plurality of divided images in a direction intersecting the body axis of the subject, and each divided image obtained by the dividing unit is a divided image in which a contrasted blood vessel image exists and a contrasted blood vessel image. And a mask image determining means for determining a mask image corresponding to a divided image in which a contrasted blood vessel image exists from the divided images in which the contrasted blood vessel image does not exist. And a subtraction image creating means for creating a subtraction image based on the divided image in which the contrasted blood vessel image is present and the mask image determined by the mask image determining means. Diagnostic imaging apparatus according to symptoms. 2. The image forming apparatus further comprises a tracking unit for tracking the tip portion of the imaged blood vessel image on each of the divided images obtained by the dividing unit, wherein the classifying unit is based on the tracking result by the tracking unit. The image diagnostic apparatus according to claim 1, wherein the image is classified into a divided image having the contrasted blood vessel image and a divided image having no contrasted blood vessel image. 3. A time difference for obtaining a difference image for each divided image obtained by the dividing means by obtaining a difference between divided images of the same part of the subject collected at different times by the collecting means. And a profile curve calculating means for calculating a profile curve in a direction perpendicular to the moving direction of the collecting means from the difference image obtained by the time difference means, wherein the classifying means calculates the profile curve. The profile curve calculated by the means is compared with a predetermined threshold value to classify into a divided image having the contrasted blood vessel image and a divided image having no contrasted blood vessel image. Item 1. The image diagnostic apparatus according to Item 1. 4. The mask image determination means is classified as a divided image in which a contrasted blood vessel image does not exist, and finally among a plurality of divided images of the same site of the subject collected at different times. The image diagnostic apparatus according to any one of claims 1 to 3, wherein the acquired divided image is determined as a mask image of the site. 5. The apparatus further comprises acquisition control means for controlling the image acquisition by the acquisition means such that the tip portion of the contrasted blood vessel image is located at the center of the image, and the dividing means is controlled by the acquisition control means. The plurality of images collected by the collecting means are divided into half sizes, and the mask image determining means collects the mask image corresponding to the upper half divided image divided by the dividing means immediately before. The image diagnostic apparatus according to claim 1, wherein the image is a divided image of the lower half of the image. 6. A series of subtraction images of the subject created by the subtraction image creating means are joined together, and the size of one subtraction image is set as a minimum unit, and the size is an arbitrary multiple of this minimum unit. The image diagnostic apparatus according to claim 1, further comprising an output unit that outputs a subtraction image.