KR20180039170A - Multi-resolution three-dimensional x-ray image reconstruction apparatus and method - Google Patents

Abstract

The present invention relates to a multi-resolution x-ray image reconstruction apparatus and method for providing a multi-resolution three-dimensional x-ray image in which a predetermined region of interest has a higher resolution than a surrounding region.
To this end, the present invention relates to a method for reconstructing a subject, comprising: a projection X-ray image acquiring unit for acquiring projection X-ray image data of a subject; an image dividing unit for dividing projection X-ray image data into a peripheral region and a region of interest; An image reconstruction unit for reconstructing the ROI such that the ROI has a higher resolution than the resolution of the surrounding region, and a display unit for displaying the reconstructed neighboring image and the ROI together.

Description

Multi-resolution three-dimensional x-ray image reconstruction apparatus and method

The present invention relates to an apparatus and method for reconstructing a multi-resolution three-dimensional x-ray image capable of acquiring a three-dimensional x-ray image having a relatively high resolution in a region of interest than a surrounding region.

Generally, an X-ray imaging apparatus includes an X-ray source, an X-ray sensor, and an image processing unit.

As shown in FIG. 1, such an X-ray imaging apparatus is configured to position a subject on a field of view (FOV) 2 between an X-ray source 4 and an X-ray sensor 5, The X-ray source 4 and the X-ray sensor 5 are rotated in opposition to each other along the rotation axis 3 passing through the center of the X-ray source 4 and the X-ray source 5 receives the X- And acquires the projection X-ray image data in various directions.

Each of the projection X-ray image data obtained in the above-described manner is a two-dimensional X-ray image, and the image processor obtains a three-dimensional X-ray image of the subject by reconstructing the projection X-ray image data in various directions into a three-dimensional X-ray image. Common reconstruction algorithms include Back Projection (BP), Filter Back Projection (FBP), and FDK (Feldkamp, Davis, and Kress).

On the other hand, the time required to reconstruct the projection X-ray image data in various directions into the three-dimensional X-ray image is determined by the size of the voxel, the size of the imaging area (FOV) The performance of hardware used for reconstruction, and the reconstruction algorithm used for reconstruction.

On the other hand, since the time required for reconstruction and the resolution of the three-dimensional x-ray image have a trade-off relationship, it is difficult to maintain the resolution of the three-dimensional x-ray image high while reducing the time required for the reconstruction, If you increase the resolution of the image, depending on the hardware performance, the reconstruction time may be excessive or even no reconstruction at all.

The present invention aims at reducing the time required for reconstructing an x-ray image. Also, the present invention provides a high-resolution three-dimensional x-ray image for a region of interest that the user mainly views while reducing the time required for reconstructing the x-ray image.

According to an aspect of the present invention, there is provided an apparatus including a projection x-ray image acquiring unit for acquiring projection x-ray image data of a subject, an image dividing unit for dividing the projection x-ray image data into a peripheral region and a region of interest, An image reconstructing unit reconstructing the reconstructed image with the set resolution and having a high resolution higher than the resolution of the surrounding area, and a display unit displaying the reconstructed surrounding image and the target image together.

According to another aspect of the present invention, there is provided a method for acquiring projection X-ray image data on a subject, dividing projection X-ray image data into a peripheral region and a region of interest, Reconstructing the ROI such that the ROI has a higher resolution than that of the surrounding region, and displaying the ROI and the ROI together.

The present invention reduces the time required for reconstruction by reconstructing the photographed region into different voxel sizes by dividing the photographed region into the region of interest and the surrounding region.

In addition, the present invention reconstructs a region of interest at a higher resolution than that of a surrounding region, thereby providing a high-resolution region of interest image.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view showing a photographing method of a general x-
2 is a view showing the relationship between an imaging region, an X-ray source, and an X-ray sensor,
FIG. 3 illustrates a multi-resolution x-ray image reconstruction apparatus according to an embodiment of the present invention.
4 is a diagram showing a method of acquiring a projection X-ray image data,
Figure 5 illustrates the relationship between a region of interest and a region of interest;
6 is a diagram showing a section in which a region of interest is set;
FIG. 7 is a diagram illustrating a reconstruction process of arbitrary projection X-ray image data; FIG. And
8 is a diagram illustrating a method of acquiring projection X-ray image data according to an embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings, It can be easily carried out. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

And throughout the specification, when a part is referred to as being "connected" to another part, it includes not only "directly connected" but also "electrically connected" with another part in between. Also, when a component is referred to as " comprising "or" comprising ", it does not exclude other components unless specifically stated to the contrary . In addition, in the description of the entire specification, it should be understood that the description of some elements in a singular form does not limit the present invention, and that a plurality of the constituent elements may be formed.

In order to facilitate understanding of the present invention, the FOV and the region of interest (ROI) will be described first.

2 is a diagram showing the relationship between the photographing area 2, the x-ray source 4, and the x-ray sensor 5. Fig.

As shown in Fig. 2, the photographing area 2 has a predetermined width w1 and a height t1. The X-ray source 4 and the X-ray sensor 5 rotate in opposite directions along the rotation axis 3 passing through the center of the photographing area 2 to obtain the projection X-ray image data in various directions, . On the other hand, the region of interest exists in the photographing region 2 and is an area which is helpful for diagnosing the subject, that is, an area which the user is interested in. For example, in a dental field, the subject may be tofu, and the area of interest may be an arch.

Generally, the subject is placed in a predetermined position in the photographing area 2, and then the subject is photographed with the X-ray, so that the subject is present at a consistent position of the X-ray image data of the subject and the reconstructed X- In a three-dimensional x-ray image, the subject exists in a coherent position in the three-dimensional x-ray image. Accordingly, for example, if the region of interest is an arch, the arch (region of interest) present in the three-dimensional x-ray image is in a coherent location.

Hereinafter, a multi-resolution X-ray image reconstruction apparatus using the above-described features will be described.

3 is a diagram illustrating a multi-resolution X-ray image reconstruction apparatus according to an exemplary embodiment of the present invention.

3, the apparatus for reconstructing a multi-resolution X-ray image according to an exemplary embodiment of the present invention includes a projection X-ray image acquisition unit 100, an image segmentation unit 200, an image reconstruction unit 300, and a display unit 400 . Although not shown in the drawing, the apparatus for reconstructing a multi-resolution X-ray image according to an exemplary embodiment of the present invention may include an input unit, a controller, a storage unit, and the like. The X-ray image acquisition unit 100, The image reconstruction unit 300, the display unit 400, the input unit, the control unit, and the storage unit may be implemented by a single or a plurality of computer devices.

For reference, the input unit may be a mouse. In addition, the input unit may include a keyboard, a keypad, a touchpad, and the like of the computer, but the type of the input unit is not limited thereto. For example, the input unit may include a graphical user interface that can be controlled using the input unit described above.

The control unit corresponds to a central processing unit that controls overall operation of the multi-resolution X-ray image reconstruction apparatus according to an embodiment of the present invention. In one embodiment, the control unit may include application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices Devices: PLDs), Field-Programmable Gate Arrays (FPGAs), processors, controllers, micro-controllers, and microprocessors. . The control unit may also be implemented as a firmware / software module executable on the aforementioned hardware platform. In this case, the firmware / software module may be implemented by one or more software applications written in an appropriate program language.

The storage unit stores various images or variable values or first projection X-ray image data, final processed three-dimensional X-ray image data, and intermediate processed X-ray image data for controlling the operation of the multi-resolution X-ray image reconstruction apparatus according to an embodiment of the present invention. And so on. In one embodiment, the storage unit may be a flash memory type, a hard disk type, a MultiMedia Card (MMC), a card type memory (for example, SD (Secure Digital) card or XD (Random Access Memory), SRAM (Static Random Access Memory), ROM (Read Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), PROM (Programmable Read-Only Memory) , A magnetic memory, a magnetic disk, and an optical disk, but those skilled in the art will recognize that the embodiment of the storage device is not limited thereto.

The display unit 400 is a video output device capable of outputting video. The display unit 400 may include various display devices such as an LCD display, an LED display, an AMOLED display, and a CRT display, and may be a touch display device. In this case, the input unit may be replaced with a touch display device.

In at least one of the control unit and the storage unit, a projection X-ray image acquisition unit 100, an image segmentation unit 200, and an image reconstruction unit 300 are installed as a main part of a multi-resolution X-ray image reconstruction apparatus according to an embodiment of the present invention .

Let's look at each in detail.

First, the projection X-ray image acquiring unit 100 acquires projection X-ray image data in various directions with respect to the subject.

To this end, the projection X-ray image acquisition unit 100 may include an X-ray imaging apparatus including an X-ray source 110 and an X-ray sensor 130, or may be connected to an X-ray imaging apparatus by wire or wireless. Here, the X-ray imaging apparatus may be, for example, a dental CBCT (Cone Beam CT) apparatus.

As shown in FIG. 4, the X-ray imaging apparatus includes an X-ray source 110 and an X-ray sensor 130, which are opposed to each other with an imaging region on which a subject is placed. The X-ray source 110 and the X-ray sensor 130 irradiate the X-ray source while rotating around the rotation axis 150 passing through the substantial center of the imaging region with the imaging region interposed therebetween, Receives the X-ray, and obtains the projection X-ray image data in various directions with respect to the photographing area.

The projection X-ray image data in various directions with respect to the imaging region are transmitted to the projection X-ray image acquisition unit 100 of the multi-resolution X-ray image reconstruction apparatus according to an embodiment of the present invention.

Next, the image dividing section 200 divides the image capturing region into the region of interest 190 and other peripheral regions, divides the projection X-ray image data of the various directions transmitted through the image capturing region into the region of interest 190 and the peripheral region do.

Here, the region of interest 190 is preset to include the region of interest 170 of the subject, as shown in FIG. For example, the region of interest 170 may be an arch, and the region of interest 190 may be horseshoe shaped including an arch. At this time, the ROI 190 may be set by the user, and may be set and adjusted through the input unit before and after the projection X-ray image acquiring unit 100 acquires the projection X-ray image data in various directions.

The image dividing unit 200 includes the region of interest 170 of the subject in the photographing region using a feature that the region of interest 170 of the subject exists in a coherent position within the region of the photographing region in a three- Ray image data of the ROI 190 into the ROI 190 and the surrounding ROI.

For example, if the region of interest 190 of the subject includes an arch, the region of interest 190 may be set to have a horseshoe shape, as shown in FIG. Then, the image dividing unit 200 divides the entire region of the projection X-ray image into a region of interest 190 corresponding to the horseshoe-shaped region and a region corresponding to the other regions.

On the other hand, the horseshoe shape is for illustrative purposes only, and any shape using at least one polygon, circle, ellipse, or a combination thereof is acceptable.

6, the region of interest 190 is between the jaw 171 of the subject and the sinus 173 when the region of interest 190 of the subject includes the arch. Thus, referring to FIGS. 5 and 6, it will be appreciated that the region of interest 190 will be in the form of a horseshoe-shaped column.

Next, the image reconstructing unit 300 reconstructs the region of interest 190 partitioned by the image partitioning unit 200 into a relatively high-resolution image having a relatively small voxel size, and enlarges the peripheral region partitioned by the image dividing unit 200 Reconstruct the voxel size to a relatively low resolution. For example, assuming that the unit pixel size of the X-ray sensor is 0.1 mm, the ROI 190 is reconstructed into a voxel having a constant size of 0.1 mm or more on each side, 0.0 > mm, < / RTI > preferably about 0.4 mm. Thus, the image reconstructing unit 300 can acquire the projection X-ray image data having the high resolution of the region of interest 190 higher than the surrounding region. Meanwhile, BP (Back Projection), FBP (Filter Back Projection), FDK (Feldkamp, Davis and Kress) and the like can be used as algorithms used for reconstructing the projection X-ray image data.

More specifically, FIG. 7 is a schematic diagram showing a reconstruction process of arbitrary projection X-ray image data. For convenience, the photographing area FOV includes only a part including the area of interest 190, and is transmitted through a part of the area of interest 190 for the sake of understanding and is received by the first and second pixels P1 and P2 of the X-ray sensor, respectively Look at only a part of the projection X-ray image data.

First, the X-rays irradiated from the X-ray source are transmitted through the subject and received by the X-ray sensor 130. As a result, the first and second pixels P1 and P2 of the X- , p2) are generated. The two-dimensional array of the pixel values becomes the value of the projection X-ray image data, and each projection X-ray image data is transmitted to the projection X-ray image acquisition unit 100.

The image dividing unit 200 divides the image capturing region into the region of interest 190 and other peripheral regions, and divides the projection X-ray image data of various directions transmitted through the image capturing region into the region of interest 190 and the surrounding region.

Then, the image reconstructing unit 300 reconstructs the region of interest 190 with a relatively high resolution of a relatively small voxel size, and reconstructs the surrounding region partitioned by the image dividing unit 200 into a relatively low-resolution voxel size larger than that. Assuming that the voxel size of the region of interest 190 corresponds to one pixel size of the x-ray sensor 130 and the voxel size of the peripheral region corresponds to two pixel sizes of the x-ray sensor 130, the image reconstruction unit 300 assigns the first and second values (p1, p2) of the first and second pixels P1 and P2 to the voxel R1 and the second pixel P2 of the region of interest, The average values of the first and second values p1 and p2 obtained by binning the first and second values p1 and p2 of the first and second pixels P1 and P2, do.

In other words, the projection X-ray image data includes a two-dimensional array of a plurality of pixel values of the X-ray sensor 130 for each direction, and the image reconstructing unit 300 generates a plurality of X- A first pixel value of n (where n is more than 1) is assigned to the first voxel, and a second pixel of relatively small number m (where m is less than 0 and less than m) Reconfigure by assigning a value. In this case, the size of the first voxel is larger than the size of the second voxel, and the first and second pixel values may represent an average value of n, m pixel values or n, m pixel values, respectively.

As described above, the image reconstructing unit 300 reconstructs the ROI 190 with a relatively high resolution of a relatively small voxel size for each projection X-ray image data, and reconstructs the surrounding region partitioned by the image partitioning unit 200 into a larger voxel size In a relatively low resolution.

The pixel size of the X-ray sensor 130, the voxel size of the region of interest and the surrounding region may be variously modified, and the peripheral region may have at least one pixel value average value corresponding thereto It is also possible to assign any pixel value as a representative value in addition to the allocation.

Finally, the display unit 400 displays a three-dimensional x-ray image generated by the image reconstruction unit 300, that is, a three-dimensional x-ray image composed of a peripheral region reconstructed with different voxel sizes and a region of interest 190 do.

FIG. 8 is a flowchart of a method for reconstructing a multi-resolution X-ray image according to an embodiment of the present invention, and a specific embodiment thereof has been described in detail in the description of the multi-resolution X-ray image reconstruction apparatus of FIG. The process will be briefly described below.

First, projection X-ray image data of various directions are acquired for a subject (S510).

Next, the projection X-ray image data is partitioned into a peripheral region and a region of interest 190 (S530). For example, the region of interest 190 may be preset to include the region of interest of the subject.

Next, the neighboring region partitioned in step S530 is reconstructed to a predetermined low resolution of a relatively large voxel size (S550).

Next, in step S570, the region of interest 190 partitioned in step S530 is reconstructed to have a relatively high resolution of a relatively small voxel size so as to have a resolution higher than that of the surrounding region (S570).

In steps S550 and S570, for example, the ROI 190 may be reconstructed into voxels of 0.1 mm or more on each side, and the surrounding region may be reconstructed into voxels of 0.4 mm or more on each side. Thus, the region of interest 190 can acquire a multi-resolution three-dimensional x-ray image having a high resolution higher than the resolution of the surrounding region.

Finally, in steps S550 and S570, a multi-resolution three-dimensional x-ray image composed of a peripheral region and a region of interest 190 having different resolutions is displayed (S590).

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, Various permutations, modifications and variations are possible without departing from the spirit of the invention.

Therefore, the scope of the present invention should not be construed as being limited to the embodiments described, but should be determined by the scope of the appended claims, as well as the appended claims.

Claims (7)

A projection x-ray image acquiring unit for acquiring projection x-ray image data of a plurality of directions with respect to a subject in an imaging region;
An image dividing unit dividing the imaging region and the projection X-ray image data in various directions into a peripheral region and a region of interest;
An image reconstruction unit reconstructing the surrounding region with a relatively low voxel size and reconstructing the region of interest with a high resolution of a voxel size relatively smaller than the surrounding region; And
And a display unit for displaying a three-dimensional x-ray image of the subject including the reconstructed peripheral image and the interest image
Multi - resolution three - dimensional x - ray image reconstruction device. The method according to claim 1,
Further comprising an input unit for inputting a command of a user,
The imaging region is divided into the peripheral region and the ROI by the user's command, and the image partition separates the projection X-ray image data of the various directions into the peripheral region and the ROI according to the user's command Multi - resolution three - dimensional x - ray image reconstruction device. The method according to claim 1,
Wherein the projection X-ray image data in the multiple directions are acquired through an X-ray source and an X-ray sensor rotating in opposite directions with the imaging region interposed therebetween. The method of claim 3,
Wherein the projection x-ray image data comprises a two-dimensional array of pixel values of the x-ray sensor for each direction,
Wherein the reconstructing unit assigns a relatively large number of pixel values to the unit voxels in the peripheral region and a relatively small number of pixel values to the unit voxels in the region of interest, Resolution three-dimensional x-ray image reconstruction device. 5. The method of claim 4,
Wherein the reconstructing unit allocates one or more pixel values or one or more pixel values to the unit voxel. 3. The method according to claim 1 or 2,
Wherein the subject is a head, and the region of interest is a horseshoe-like shape including the arch of the subject between the jaw and the sinus of the subject. Acquiring projection X-ray image data of a plurality of directions with respect to a subject in an imaging region;
Dividing the imaging region and the projection X-ray image data of the plurality of directions into a peripheral region and a region of interest;
Reconstructing the surrounding region with a relatively high voxel size and reconstructing the region of interest with a high resolution of a voxel size relatively smaller than the surrounding region; And
Dimensional x-ray image of the subject including the reconstructed peripheral image and the interest image
Multi - resolution three - dimensional x - ray image reconstruction method.

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