JPH0230067B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an image conversion device that obtains a cross-sectional image of a desired curved surface from a plurality of consecutive cross-sectional images.

[Technical background of the invention]

For example, as an image diagnostic device used for medical purposes, etc.
There is something called a CT (computer tomography) device.

This device includes, for example, an X-ray source that emits Fan beam X-rays that spread in a flat fan shape as a radiation source, and is placed facing this X-ray source through a subject, and is arranged in a direction in which the Fan beam X-rays spread. Using a radiation detector with a spatial resolution that includes multiple radiation detection elements, the X-ray source and the radiation detector are moved in the same direction around the subject at an angle of about 180° to 360° in 1° increments, for example. After collecting X-ray absorption data from multiple directions on the tomographic plane of the subject while sequentially rotating and scanning, the image is reconstructed using a computer, etc.
Since images can be reconstructed in as many as 2,000 gradations, it is possible to understand the state of the tomographic plane in detail.

By the way, a reconstructed image (hereinafter referred to as a CT image) obtained by such a CT apparatus is determined by the thickness of the Fan beam X-ray and the detection field of the radiation detector. In other words, the area through which the X-rays incident on the radiation detector pass through the subject is obtained as a CT image. This CT image per section is called a 1-slice CT image, but since the slice thickness of 1 slice (the thickness of the X-rays incident on the radiation detector) is small, in order to diagnose the area of interest, it is necessary to CT images for multiple slices are obtained by sequentially shifting the slice position by approximately the slice thickness to cover the entire area.
Try to get information about the area of interest.

However, multiple CTs obtained in this way
Each image is a tomographic image, so in order to know the state of the entire area of interest, these multiple CT images CP1 to CPn are used.
After arranging the slices in the order of slice positions, a desired cross section S is set, and image data on the cross section S is extracted to obtain an image _Ps of the cross section S.

By the way, in the case of such a conventional method, the cross section S that can be set is limited to a two-dimensional plane, and as shown in FIG. 1, the region of interest R is located curved in three-dimensional space like a spine. In this case, the images on the cross section S are a collection of those located on the line _Ls in each CT image CP1 to CPn, and as is clear from the figure, the region of interest R in each CT image does not necessarily exist on this line _Ls . Therefore, even if the cross-section S is set to match the distribution area of the region of interest R as much as possible, the image _Ps on the cross-section S that is actually obtained will have a part of the region of interest missing, as shown in Figure 1. There are things to do. Therefore, when performing a diagnosis in such a case, there is a drawback that the whole picture of the region of interest R cannot be grasped and the diagnosis is difficult to perform, and an improvement is desired.

In addition, in the medical field, as shown by S1 in Fig. 2a, the cross section S in Fig. 1 is set vertically to obtain an image of this cross section (this is called a sagittal image), or as shown in Fig. 2a
As shown in S2, the cross section S is set horizontally to obtain an image of this cross section (this is called a coronal),
The image of this cross section (this is called a paraaxial image) can be obtained by tilting the cross section S around the subject axis as shown in S3 in Fig. 2a, or as shown in S4 in Fig. 2b. In some cases, a cross-sectional image (this is called an oblique) is obtained along axis b inclined with respect to the subject axis a and obliquely with respect to the horizontal, but these are all linear planes. Therefore, if the region of interest is curved, the same inconvenience as explained in FIG. 1 will occur.

For example, for an image P as shown in FIG. 3a, S1
When a sagittal image of a cross section is obtained, it becomes as shown in FIG. 3b, and only a small portion of the region of interest R remains. Furthermore, when an oblique image of a cross section S4 is obtained for the same image P as shown in Fig. 4a, Fig. 4b
In both cases, most of the region of interest is missing, making it impossible to observe the desired image.

[Purpose of the invention]

The present invention was made in view of the above circumstances, and
It is an object of the present invention to provide an image conversion device that can obtain a cross-sectional image obtained by cutting an object along an arbitrary curved surface from a plurality of continuous slice tomographic images obtained by a CT device or the like.

[Summary of the invention]

That is, in order to achieve the above-mentioned object, the present invention is an apparatus that obtains data of continuous cross-sectional images of a subject and generates an image of a desired cross-section that intersects the cross-section of the subject from the data. means for setting a center of a desired cross-sectional position of and setting an enlarged reconstruction region centered on the center;
means for performing enlarged reconstruction processing on the enlarged reconstruction region centered on the set cross-sectional position center based on data of the continuous cross-sectional images; A means for obtaining a cross-sectional image of a plane in a predetermined spreading direction passing through the center position by image conversion, and a means for displaying the converted cross-sectional image, and a desired cross-sectional position center for each successive cross-sectional image of the object. and set an enlarged reconstruction area centered on the center position, enlarge and reconstruct the set position and area, and make each enlarged reconstruction center around the set center position. Obtain an enlarged reconstructed image, thereby obtaining a plurality of reconstructed images in which the target region is centered, and from these reconstructed images, a cross section in a plane passing through the center and extending in a predetermined direction is obtained. By obtaining an image, it is possible to obtain a cross-sectional image of a region of interest that is distributed in a curved manner, and by applying an orthogonal projection to this cross-sectional image, it is possible to observe the cross-sectional image in an actual state. Do it like this.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

First, an example of cross-sectional image generation in which a curved region of interest (tissue) is displayed without interruption will be described.

When generating a cross-sectional image, image data obtained by target tracking is used, in which the scanning position of the subject and the center position of the tissue of interest are set and scanned. From the multiple image data obtained in this way, image data corresponding to the target cross section is extracted in the same way, and a curved cross-section transformed image of the target region of interest is obtained by performing cross-section transformation. It will be done.

FIG. 5 is a block diagram showing the configuration of this device, and is an example in which a CT device is used as the image data collection system.

In the figure, numeral 51 is the pedestal of the CT device, and this pedestal 5
1 is rotatably supported, and a hole 51a for placing the subject S is provided in the center. This frame 51
An X-ray source 52 and a detector 53 for detecting X-rays are provided facing each other through the hole 51a.

The X-ray source 52 is equipped with a heavy metal diaphragm on the X-ray emission port side, and this diaphragm makes it possible to radiate a flat Fan beam X-ray FB having a fan-like spread toward the detector 53. ing. The spread angle of this fan beam X-ray FB is set in advance to such an extent that it can cover the opening diameter of the hole 51a in the pedestal 51.

Further, the detector 63 is made up of a plurality of radiation detecting elements 53a that output electrical signals corresponding to the intensity of radiation, which are arranged in parallel at a predetermined interval in the direction in which the fan beam X-rays FB spread. It has spatial resolution. And each radiation detection element 5
3a each radiation detection element 53a and X-ray source 52
X-ray source 5 through the X-ray path (X-ray path) connecting
The intensity of the X-rays arriving from 2 is detected.

Reference numeral 54 denotes a data collection unit, which receives detection outputs for each X-ray projection angle output from each detection element 53a of the detector 53, and obtains data on X-ray intensity.

55 is a high voltage generation and X-ray control unit that applies high voltage to the X-ray source 52 and also controls X-ray exposure; 56 is a bed on which the subject is placed;
This is a pedestal and bed control unit that controls the rotation of the bed 56 and the positioning of the bed 56.

The bed 56 is provided with a top plate on the upper part of the main body,
The object can be placed on this top plate and the top plate can be sent in the direction of the hole 51a of the mount 51, thereby collecting data on the tomographic plane of the object by sequentially changing the slice position. be able to.

A computer 58 controls the entire system, receives data collected by the data collection unit 54, performs arithmetic processing on the data, reconstructs an image, and calculates a desired image including curved surfaces from reconstructed images of a plurality of consecutive sections. It has a function of creating an image of a cross section when the cross section is cut. 59 is the operation/display section
CRT (cathode ray tube) display and keyboard,
It has a trackball or the like, and it is desired to perform various input/output commands to the computer 58 through keyboard operations, display images created by the computer 58 on a CRT display, and display by specifying coordinates, etc. by operating the trackball. It is possible to specify the cross section, etc. Here, a trackball is an input that is a sphere held so that it can be rotated in any direction, and when the sphere is rotated in a desired direction by hand, positional information corresponding to the direction and amount of rotation can be generated. The device is capable of displaying a marker on the CRT display screen corresponding to the position information input using the trackball.

Reference numeral 60 denotes a large-capacity auxiliary storage device for storing data such as images created by the computer 58 or data collected by the data collection unit 54, such as a magnetic tape device (MT), a floppy disk drive (FDD), a bird disk, etc. equipment etc. are used.

Reference numeral 61 is a line printer for obtaining a hard copy of input/output data from the computer 58 or the like.

Next, the operation of this device having the above configuration will be explained. FIG. 6 is a diagram showing the procedure, and the computer 58 performs processing according to this procedure. That is, in this apparatus, first, control is performed to obtain a Schiano image of the subject. This control is performed by commands from the keyboard.

Here, the Schiyano image is an image obtained by projecting the subject A from one direction as shown by A' in FIG. The top plate of the bed 56 is continuously sent into the hole 51a while being intermittently exposed to X-rays, and at this time, the detection output obtained from the detector 53 is collected as data by the data collection unit 54,
Obtained by arranging in the order of movement. FIG. 7 shows an example in which the X-ray source 52 is located directly beside the subject.

When the image data collection of the Schiyano image is completed, the computer 58 displays the Schiyano image obtained through this collection.
Display on CRT display.

The operator sets desired cross-sectional positions CP _a , CP b , . . . for each slice position (or desired slice position) S _a , S _{b .} . . while viewing this Schiano image.
This is done by operating the keyboard and track ball, and the procedure is as follows.

(1) Specify slice positions S _a , S _b , . . . on the Schiyano image at which future scans will be performed using straight lines.

(2) For each slice position, designate one point on the aforementioned straight line indicating that position. This designated point is later used to determine the center of reconstruction in the enlarged reconstruction processing routine.

(3) The “enlarged reconstruction region” used in the enlarged reconstruction processing routine is a rectangular ROI (Region Of
Specify using Interest (region of interest specification function).

After these specifications are completed, the computer 58 controls the system to begin the scan data collection operation.

This involves sequentially rotating and scanning the gantry 51 and shifting the top of the bed 56 in order to obtain CT images at each slice position in accordance with the plan created in (1) above, and data is collected via the data collection unit 54. collect.

After data collection is completed, the computer 58 creates reconstructed images at the positions S _a , S _{b ,} such as P _a , P _b , . . . in FIG. 7, and then begins enlarged reconstruction work.

This work involves enlarging and reconstructing the tomographic image of the desired area.The collected data is enlarged and reconstructed based on the center position and enlarged area determined in the previous settings, and PZ _a in Fig. 7, Magnified reconstructed images of S _a and S _b such as PZ _b , . . . are obtained. As a result, a reconstructed image centered on the center position determined in the previous settings is obtained.

Next, curved surface cross section conversion processing begins. This uses the previously obtained enlarged and reconstructed image to perform cross-sectional conversion processing.

These image data have been enlarged and reconstructed focusing on the region of interest R, but these images are treated as if they were CT images obtained by normal scanning, and the direction of spread of the cross section is A conventional cross-section conversion process is performed on that plane. Although this plane is the projection direction of the Schiano image, it is also possible to designate a desired direction if necessary.

The cross-sectional image thus obtained is the image shown by PC in FIG. By processing the above-mentioned procedure, this cross-sectional image PC becomes a developed image of a cross-section S s ' along the cross-sectional position S _s where the region of interest, which is the curved R, of the subject as shown by A in FIG. ₈ is located. becomes. Thereafter, the computer 58 performs display control to display this cross-sectional image PC. This results in
A cross-sectional image PC obtained by performing the above curved cross-section conversion process is displayed on the CRT display.

Incidentally, if necessary, the above-mentioned images or the collected data and the Schiyano image data are stored in the auxiliary storage device 60 so that they can be used later.

While viewing the Schiano image in this way, set the center position for enlarged reconstruction of the region of interest at each slice position using a cross cursor, etc., and set the area for enlarged reconstruction. Rotational scanning is performed to collect data for a CT image, and then enlarged reconstruction is performed for the specified enlarged reconstruction region using the set center position as the center for these collected data, and the data for each slice position is Since the data of the respective set center positions are extracted from the enlarged reconstructed image and arranged in the order of slice positions to obtain a cross-sectional image, an image of a desired curved cross-section viewed from a desired projection direction with respect to the subject can be obtained. Therefore, it is possible to obtain an image of the region of interest in which the curved region of interest is cut out at a desired cross section along the distribution direction.

In addition, in the above example, the curved cross-section conversion was set using the Schiyano image, and then the curved cross-section conversion was performed, but the curved cross-section conversion can be applied in the following cases without using the Schiyano image. . In other words, as shown in FIG. 9, there is a plurality of data of images a to d in which the continuous region of interest R is captured, and the cross-sectional position S for each of them can be specified using Roy or the like. The image obtained by performing cross-sectional transformation based on the table position and extracted data of the image becomes a curved cross-sectional transformed image.

The cross-sectional image obtained by the above explanation is an expanded image of a cross-section along a desired curved curve.
Moreover, the cross section is exposed to X to obtain the Schiyano image.
It must be parallel to the direction of the line. This X
Setting a cross section in any direction (without twisting) regardless of the direction of the line can be achieved using the method described below.

Here, in order to ensure accuracy, when performing cross-sectional conversion in a CT device, the center position of each planned slice of the tissue of interest is set to be different as shown in Fig. 10 before acquiring scan data of the object. Determination is made from scanned images from two directions (of course, in this case, it is also possible to perform the determination based on scanned images from one direction as in the method described above), and the enlarged reconstructed image after scanning is determined. Make the area of interest visible in the center. If conventional cross-sectional conversion is performed from these multiple scan images on any plane parallel to the central axis direction line d _ax shown in FIG.
A cross-sectional image indicated by B in the figure is obtained. When this cross-sectional image is converted in consideration of the relative position of the actual subject, an image shown by C in FIG. 11 is obtained.

The final image obtained is the curved surface S _c in Figure 12.
This is equivalent to the cross-sectional image that appears when the tissue of interest R, which is not on a plane, that is, is distributed in a curved manner, is cut with a curved cross section that matches the distribution area.

Examples thereof will be described below.

FIG. 13 is a flowchart showing the procedure, and the explanation will be made along this flowchart. The computer 58 generates an image according to this procedure.

First, a Schiyano image in a certain direction 1 is taken (S1). Next, a Schiyano image is taken in another direction 2 that is not opposite to direction 1 (S2). The position of the region of interest of the subject is determined based on the Schiyano image (S3). Here, we will implement this using the following steps.

Step 1 - Setting the center of the image display area The operator starts the curved cross-section conversion program and displays the Schiyano image in directions 1 and 2 in the direction of the CRT display. A point on the region of interest R on this image is designated with a cursor using a trackball. Next, the Schiyano image in directions 2 and 1 is displayed on the display. Since the position in one direction has already been determined, a point on the line (displayed by the program) corresponding to that position is specified with the cursor M _c (Figure 10b). Repeat this operation for each scanned image to determine the center of each image.

Step 2 - Designation of enlarged size A rectangle is displayed on the image, and its size is freely set using the track ball to be the size of the enlarged reconstruction area after scanning.

When this is finished, the rotation scanning of the pedestal 51 and the bed 5 are performed.
3, and perform a scan to obtain a CT image to collect data (S4). In this method, the number of images to be photographed is determined first, the enlargement size is kept constant, and the top of the bed is moved so that the scan slice plane includes the center position, and the scans are performed sequentially.

Then, enlarged reconstruction (S5) is started. This will send the data collected by the above scan to S3C
Enlarged reconstruction is performed based on the center of the image display area and the enlarged size determined in (FIG. 14). (The above is nothing but target tracking.) Next, a curved surface section conversion process (S6) is executed. This involves adding the following processing to the enlarged and reconstructed image data.

Processing 1 - Cross-section conversion using a plane parallel to the body axis The operator performs cross-section conversion using a conventional cross-section conversion operation on a plane that passes through the center of the image and is parallel to the body axis.

Processing 2 - Mapping to obtain the original cross-sectional image The cross-sectional image obtained in Processing 1 in S6 is mapped using a mapping function determined by the plane used in Processing 1 and the two Schiano directions, to create a curved cross-sectional image. Get the transformed image.

Then, display of the curved cross-section converted image (S7) is executed, and the above-mentioned cross-section image is displayed on the CRT display.

That is, in this embodiment, in order to obtain a cross-sectional image of the curved region of interest R of the subject shown by A in FIG. 12, a cross section is set along the distribution area of the region of interest R.
An image PS _c of S _c can be orthogonally projected to obtain an image PS _c ′ by the orthogonal projection.

In principle, as shown in FIG. 14, enlarged reconstructed images PZ _a , PZ _b ,
...obtain PZ _o , thereby bringing the region of interest R to the center of each image, and arranging this at the slice position to obtain an image of the subject A viewed with the region of interest R as a reference as shown in FIG. 11, For this image, mapping is performed on an image PA obtained by cutting the region of interest R at a planar cross section S _f to restore a realistic image P _r .

That is, as shown in FIG. 15, a cross-sectional image appearing on a plane S _f parallel to the body axis direction y and passing through the center O in the enlarged and reconstructed image of the subject A shown in FIG. 11 is defined as PA. When a positional correction in the direction (direction 3) perpendicular to the straight line R on PA is applied to the cross-sectional image, an image _Pr converted to a curved cross-section is obtained.

The meanings of the symbols in the diagram are shown below.

θ ₁ : Angle formed by direction 1 and direction 3 θ ₂ : Angle formed by direction 2 and direction 3 l ₁ (y), l ₂ (y): Direction 1 component and direction 2 component of the vector required to move the center position (varies depending on y) l ₀ (y): Position correction in direction 3 (varies depending on y) l ₀ is obtained by the following equation.

l ₀ (y) = l ₁ (y) cosθ ₁ + l ₂ (y) cosθ ₂ Find l ₀ at the point where the center position is set,
Mapping f is performed using them.

FIG. 16 shows this situation.

In the above example, Schiyano images obtained from two non-parallel directions were used as a means of determining the center position of the region of interest, but this is because the data for determining the position of the tissue is subjected to cross-sectional transformation. This is an effective method when no request has been made before.

Therefore, when the above data is available, it becomes possible to perform curved cross-section conversion without using the 2-Schiano image, and an example thereof is as shown below.

When a CT reconstructed image has been obtained If a reconstructed image has already been obtained, the first
As shown in Figure 7, images PO1 and ~PO4 in which the site of interest (cross section) ti appears are extracted from multiple images, and each image center I _c is moved with the cursor (+ in the figure).
mark) and find the positional relationship between the specified image center I _c and ti. When the plane that cuts ti is specified by a straight line L on one image, ti of each image is cut at the slope of the straight line L. Step 13 from the above operations
Since the process S3 shown in the figure has been added, the curved cross-section conversion of the process S6 becomes possible.

However, two or more images containing ti are required.

Furthermore, in the case of , it is clear that if there is one Schiyano image, it can be used together with the reconstructed image to determine the I _c -ti positional relationship.

When a tomographic image is obtained using a device other than CT: Curved cross-section conversion is also possible from a tomographic image obtained from an X-ray tomography device.

According to the above embodiment, an image obtained by orthogonally projecting an image of a curved cross-section of a region of interest which is distributed in a curved manner onto a plane can be obtained, thereby making it possible to observe an image that corresponds to the actual situation. becomes.

The present invention is not limited to medical use, but can be fully applied to destructive inspection, measurement, etc. in industrial use, and image data can be used not only with CT equipment but also with NMR-CT equipment.
The present invention can be applied to images obtained by various devices such as (the magnetic resonance CT device), positron CT, or ultrasound device.

〔Effect of the invention〕

As described above, the present invention is an apparatus that obtains data of continuous cross-sectional images of a subject and generates an image of a desired cross-section intersecting with the cross-section of the subject from the data. Means for setting a cross-sectional position center and an enlarged reconstruction region centered on the center, and the enlarged reconstruction region centered on the set cross-sectional position center based on data of the continuous cross-sectional images. means for performing enlarged reconstruction processing of the enlarged and reconstructed continuous cross-sectional images of the subject; means for obtaining, by image conversion, a cross-sectional image of a plane in a predetermined spreading direction passing through the center position of the enlarged and reconstructed continuous cross-sectional images of the subject; a means for displaying an image, setting a desired cross-sectional position center for each of successive cross-sectional images of a subject, setting an enlarged reconstruction area centered on the center position, and displaying the set position and area. Through each enlarged reconstruction, an enlarged reconstructed image centered on the set center position is obtained, thereby obtaining a plurality of reconstructed images in which the target region is centered, respectively. By obtaining a cross-sectional image on a plane extending in a predetermined direction passing through the center from the reconstructed image, it is possible to obtain a cross-sectional image of a region of interest distributed in a curved manner. Therefore, it is now possible to obtain an image of a curved cross-section of a region of interest, which is partially interrupted in the past, without any interruption in the image, and it is also possible to perform orthogonal projection on this cross-sectional image. As a result, it is possible to provide an image conversion device that is extremely effective for diagnosis, such as allowing the cross-sectional image to be observed in a realistic state.

[Brief explanation of drawings]

Figure 1 is a diagram for explaining an example of a conventional image conversion method, Figure 2 is a diagram showing an example of how to take a cross section, and Figures 3 and 4 are diagrams showing a converted image obtained by that method of taking a cross section. FIG. 5 is a block diagram showing an embodiment of the present invention, and FIG. 6 is a diagram for explaining an example.
The figure is a flowchart showing an example of the processing procedure of the apparatus of the present invention, FIGS. 7 and 8 are diagrams illustrating the processing procedure, FIG. 9 is a diagram for explaining a modified example, and FIG. 12 and 14 are diagrams for explaining a method for obtaining an orthogonal projection image of a desired cross section from a Schiano image viewed from two directions, FIG. 13 is a flow chart thereof, and FIG. 15 , FIG. 16 is a diagram for explaining the principle of orthogonal projection, and FIG. 17 is a diagram for explaining a modification. 51... Frame, 52... X-ray source, 53... Detector, 54... Data collection unit, 56... Bed, 57
... cradle, bed control section, 58 ... computer,
59... operation/display unit, 60... auxiliary storage device.

Claims (1)

[Scope of Claims] 1. A device that obtains data of continuous cross-sectional images of a subject and generates an image of a desired cross-section that intersects the cross-section of the subject from the data, and a desired cross-sectional position of the continuous cross-sectional images of the subject. means for setting a center and an enlarged reconstruction area centered on the center; and enlargement of the enlarged reconstruction area centered on the set cross-sectional position center based on data of the continuous cross-sectional images. means for performing reconstruction processing; means for obtaining, by image conversion, a cross-sectional image of a plane in a predetermined spreading direction passing through the center position of the enlarged and reconstructed continuous cross-sectional images of the subject; and means for converting the converted cross-sectional images. An image conversion device comprising display means. 2. A device that obtains data of continuous cross-sectional images of a subject and generates an image of a desired cross-section that intersects with the cross-section of the subject from the data, and sets the center of the desired cross-sectional position of the continuous cross-sectional images of the subject. means for setting an enlarged reconstruction area centered on the center; and means for performing enlarged reconstruction processing on the enlarged reconstruction area centered on the set cross-sectional position center based on data of the continuous cross-sectional images. , means for obtaining, by image conversion, a cross-sectional image of a plane in a predetermined spreading direction passing through the center position of the enlarged and reconstructed continuous cross-sectional images of the subject; and means for orthogonally projecting the transformed cross-sectional images. , and means for displaying a cross-sectional image obtained by this orthogonal projection processing.