WO2015072805A1

WO2015072805A1 - Ct photographing device, ct photographing method, target phantom for ct photographing and ct image using same

Info

Publication number: WO2015072805A1
Application number: PCT/KR2014/011059
Authority: WO
Inventors: 최성일; 한태희
Original assignee: 주식회사바텍; (주)바텍이우홀딩스
Priority date: 2013-11-18
Filing date: 2014-11-18
Publication date: 2015-05-21
Also published as: KR20150057013A

Abstract

Disclosed are a CT photographing device, a CT photographing method, a target phantom for CT photographing and a CT image using the same. The CT photographing device according to the present invention comprises: a CT photographing unit for acquiring a CT image of a subject into which a target phantom having a unique CT number is inserted; and an image processing unit for identifying the target phantom from the CT image acquired by the CT photographing unit and adjusting the CT image on the basis of the difference between a CT number of the target phantom, which is displayed on the CT image, and a unique CT number of the target phantom. The CT photographing method according to the present invention comprises the steps of: acquiring a CT image in a state in which a target phantom having the previously known CT number is inserted within CT photographing range of a subject; and identifying the target phantom from the acquired CT image and adjusting the CT image on the basis of the difference between a CT number of the target phantom, which is displayed on the CT image, and a unique CT number of the target phantom.

Description

Citi shooting device, Citi shooting method, target phantom for Citi shooting and Citi image using the same

The present invention relates to a tomography apparatus using X-rays, that is, a CT (computed tomography) apparatus and a CT imaging method, and more particularly, a dental CT imaging apparatus including a tooth as the main subject of the human body; It relates to a CT imaging method using the same.

In the medical field, an X-ray imaging apparatus refers to a device that transmits a predetermined amount of X-rays to a body part to be photographed, and provides an image using an electrical signal generated by the X-ray sensor receiving the transmitted X-rays. Since the X-rays transmitted through the body part generate different electric signals according to the X-ray absorption rate of each point of the body photographing part, the electric signals may be processed through a central processing unit provided in the X-ray imaging apparatus, thereby realizing an image.

In dental practice, dental x-ray computed tomography (CT) imaging devices reconstruct x-ray images taken from different angles, rotating around the entire area of the patient's body, which is the main area of interest, such as the teeth, gums, jaw joints, or head. A tomography image or a device for providing a three-dimensional image as needed.

In general, as a dental CT, cone beam CT (hereinafter referred to as CBCT) is used. CBCT has the disadvantage of providing incorrect values due to the influence of scattered lines and truncated conditions, while providing a level of precision and convenience suitable for dental diagnosis. Since the area to be diagnosed at the dentist has many parts related to the shape of bone tissue such as an implant, even if the accuracy of the CT number detected through the CBCT is somewhat insufficient, it is not enough to be used for dental diagnosis. However, related industries and academia have been continuously researching the accuracy of CT number detected by CBCT with the accuracy of CT number detected by medical CT (MDCT). It has been pointed out.

Recently, as the necessity of diagnosis through oral cancer or bone density examination has emerged in the dentist, it is required to add a function suitable for such diagnosis to dental CBCT equipment, but in view of the accuracy of CT number of dental CBCT at present It is difficult to provide such a diagnostic function. In general, when oral cancer develops, it often occurs on soft tissues until bone destruction occurs. Currently, dental CBCT-level CTs for soft tissues are difficult to identify with images. Bone density is also difficult to diagnose with low CT number accuracy because the density of the subject material is related to the CT number.

On the other hand, until now, as a method of maintaining the accuracy of dental CBCT equipment, it is known to regularly evaluate the image quality and to calibrate the equipment by taking a phantom (Panthom) known in advance the CT number. There is also an example of an invention related to a phantom holder (see Korean Patent Publication No. 10-1181346) for evaluating image quality using a phantom.

An object of the present invention is to improve the accuracy of the CT number detected through the imaging image of the dental CBCT. More specifically, the present invention improves the accuracy of CT numbers for tissues in a subject by calibrating and outputting an image obtained by inserting a target phantom into a subject using a CT number of the target phantom known in advance. It is an object of the present invention to provide a CT imaging apparatus and a CT imaging method.

In order to solve the above problems, a CT imaging apparatus according to an aspect of the present invention, CT imaging unit for acquiring a CT image of the subject with a target phantom having a unique CT number; And identifying the target phantom from the CT image acquired by the CT imaging unit, and adjusting the CT image based on the difference between the CT number of the target phantom and the unique CT number of the target phantom displayed on the CT image. It includes an image processor.

The target phantom may be one having two or more different unique CT numbers. The target phantom may have a unique code embedded in at least one of a shape, a marker, an arrangement, and a structure, and the image processor may identify the target phantom and the unique CT number with the unique code. have.

The image processing unit may include: a target phantom identification module identifying the target phantom from the CT image; A target phantom data module for obtaining information about a unique CT number of the identified target phantom; And an image adjustment module for adjusting the CT image such that the target phantom is displayed according to a unique CT number.

Here, the target phantom may have a unique code embedded in its own shape or in the form and arrangement of a marker, and the target phantom identification module may identify the unique code from the CT image.

The target phantom data module may be to acquire a unique CT number corresponding to the target phantom identified from a data group previously stored in a data storage inside or outside the CT imaging apparatus.

A target phantom according to one aspect of the present invention is inserted into a CT field of view (FOV) including a subject and CT shot with the subject, two or more having a unique CT number.

The target phantom may be a mouthpiece or a bite block inserted into the subject during CT imaging.

CT imaging method according to an aspect of the present invention comprises the steps of acquiring a CT image with a target phantom having a unique CT number inserted into the CT imaging range (FOV, Field Of View) with the subject; And identifying the target phantom from the acquired CT image, finding a correction condition based on the difference between the CT number of the target phantom and the target phantom displayed on the CT image and the unique CT number, and based on the correction condition. Adjusting the image.

In a CT image according to an aspect of the present invention, a target phantom having two or more unique CT numbers exists within a CT field of view (FOV) including a subject, and the target phantom is the two or more unique CT numbers. The portion corresponding to at least one of the portions is represented by the gray scale level corresponding to the unique CT number of the portion.

According to the present invention, there is an effect of improving the accuracy of the CT number detected through the captured image of the dental CBCT. More specifically, according to the present invention, an image obtained by inserting a target phantom into a subject is calibrated and output using a previously known CT number of the target phantom, thereby improving the accuracy of the CT number for the tissue in the subject. There is an effect of providing a CT imaging apparatus and a CT imaging method to be improved.

FIG. 1A illustrates an example of acquiring a CT image of a subject into which a target phantom is inserted in a CT imaging apparatus according to an exemplary embodiment.

FIG. 1B illustrates an example in which the CT image of FIG. 1A is adjusted so that the target phantom is displayed according to a unique CT number in a CT imaging apparatus according to an exemplary embodiment.

2 is a perspective view showing a target phantom according to an embodiment of the present invention.

3 is a cross-sectional view of the target phantom of FIG.

4 is a cross-sectional view showing a target phantom tomography according to an embodiment of the present invention.

5 is a perspective view showing a target phantom according to an embodiment of the present invention.

6 is a perspective view showing a target phantom according to an embodiment of the present invention.

7 is a block diagram showing the configuration of a CT imaging apparatus according to an embodiment of the present invention.

8 is a flowchart showing a CT imaging method according to an embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention. The embodiments described below may be modified in various forms, and the scope of the present invention is not limited to the following embodiments. Embodiment of the present invention is provided to clearly convey the technical spirit of the invention to those skilled in the art.

FIG. 1A illustrates an example of acquiring a CT image of a subject into which a target phantom is inserted in a CT imaging apparatus according to an exemplary embodiment. That is, FIG. 1A shows a CT image of a state before calibrating an image using the target phantom 10. In the CT imaging apparatus according to the present invention, as shown, a CT image is acquired with a target phantom 10 having a known unique CT number in advance in a field of view (FOV) of a subject, for example, a patient's mouth. do. Here, the CT image is obtained by using a X-ray generator, an X-ray sensor, and a driving device for driving the same as in a general CT imaging apparatus, and photographing a plurality of X-ray images from various angles, and reconstructing a plurality of X-ray images. This is done by obtaining a tomographic image corresponding to a slice (monolayer) of.

However, the CT image taken by the dental CBCT is less accurate than the CT image taken by the medical CT. In particular, the accuracy of CT numbers for soft tissues is poor. The biggest causes of the accuracy of CT numbers in CBCT are scatter lines and truncated conditions. Scattered line is a problem that occurs due to the characteristics of CBCT, and scattered X-rays are included in X-ray image data of slices to be viewed, which are different from each other. Because of the difference, compensation methods are difficult and inaccurate. In addition, in CBCT with many truncated conditions, it is difficult to extract accurate data on the CT number of air, which hinders the uniformity of the overall CT number.

In the CT imaging apparatus according to the present invention, the acquired CT image is based on the unique CT number of the target phantom 10 that is inserted into the subject, more specifically, to a portion adjacent to the tissue of interest and photographed together. By calibrating the CT number of the entire image, it is possible to increase the accuracy of the CT number for the tissue of interest detected by CT imaging.

The CT number is a value related to the X-ray transmittance, and since there is a fixed defined value for bone, soft tissue, water, and air, the CT of the subject by using a target phantom made using a material having a unique CT number close to this value The number can be detected more accurately. By dividing the target phantom into multiple regions and having different unique CT numbers for each region, multiple calibration reference values may be provided in one target phantom. In FIG. 1A, a target phantom 10 consisting of regions having three CT numbers is disclosed.

In the CT image, the CT number of the tissue is represented by a gray scale level. However, the level expressed in the CT image before calibration as shown in FIG. 1A does not exactly match the CT number of the corresponding tissue. This is because an error due to scattering lines or truncated conditions exists as described above. Since the influence of the scattering line or the error due to the truncated condition varies depending on the state of the subject or the position in the subject, the target phantom 10 is disposed at a position close to the tissue of interest even in the subject, It is desirable to calibrate and adjust the image. On the other hand, in the CT imaging apparatus according to the present invention as described above, the CT image before the adjustment may not be displayed on the screen. However, depending on the user's selection, it may be displayed for the purpose of comparison before and after adjustment.

FIG. 1B illustrates an example in which the CT image of FIG. 1A is adjusted so that the target phantom is displayed according to a unique CT number in a CT imaging apparatus according to an exemplary embodiment. As described above, in the present embodiment, the target phantom 10 is composed of three regions each having a unique CT number. In general, an image processor mounted on a CT imaging apparatus displays CT numbers of parts of a tomography of a subject, which are detected through a CT image reconstructing a plurality of X-ray image data, on a screen corresponding to a gray scale level that can be expressed. The mapping of the gray scale levels to the detected CT numbers, that is, the mapping operation, is performed by using a kind of lookup table that is preset and stored in the image processing unit. It may be performed to correspond to.

However, the CT imaging apparatus according to the present invention already knows the unique CT numbers for the respective regions of the target phantom 10. In order for the target phantom 10 to be displayed on the screen according to the unique CT number, the CT imaging apparatus according to the present invention previews the CT numbers in the CT image before adjusting the three regions of the detected target phantom 10. Each unique CT number is used as a calibration reference value, and the adjustment is made by applying the same adjustment conditions as the adjustment conditions for the corresponding area to the entire CT image before adjustment. Increase the accuracy of the CT number on the subject tissue.

Based on this embodiment in which the target phantom 10 has three different unique CT numbers, examples of the adjustment condition will be described as follows. The first example is selected based on any one of the three unique CT numbers, for example, close to the CT number of the tissue of interest in the subject, and the CT number before the adjustment of the corresponding region of the target phantom 10 and the corresponding unique CT. The adjustment condition that applies the formula to correct the number difference is applied to the entire CT image before the adjustment. As a second example, an adjustment condition for obtaining a correction equation for matching the CT numbers before adjustment of the three regions of the target phantom 10 with corresponding unique CT numbers, and applying the correction expression to the entire CT image before adjustment Can be mentioned. Further, as a third example, the difference between the three unique CT numbers or some of them and the CT number before the adjustment of the corresponding area is obtained, and the CT number is an intermediate value between them, such as the CT number before the adjustment and the unique CT number. A correction equation that matches the mean value can also be obtained and applied to the entire CT image before adjustment.

FIG. 2 is a perspective view illustrating a target phantom according to an embodiment of the present invention, and FIG. 3 is a cross-sectional view illustrating a target phantom of FIG. 2. The target phantom 10 according to the present embodiment consists of three regions, which have different unique CT numbers for each region. To this end, the three regions may be made of different materials m1, m2, and m3. For example, it may be made of a metal having a unique CT number similar to a CT number of bone, or a synthetic resin (eg, PMMA) having a unique CT number similar to Teflon, water, or soft tissue. The target phantom 10 may be selected to include a region of the subject having a unique CT number that is similar to the approximate CT number of the tissue of interest.

As such, when the target phantom is composed of a plurality of regions made of different materials, a calibration equation for calibration may be set for each region of the target phantom. In this case, the CT image may be adjusted by determining the CT number distribution of the CT image before the adjustment, matching each region of the image with the region of the target phantom, and applying a calibration reference value of the corresponding target phantom region to the image. In other words, if the unique CT numbers of the different materials m1, m2, and m3 that make up the three regions of the target phantom are similar to the CT number of the bone, the CT number of the soft tissue, and the air and CT numbers, the CT image before the adjustment is CT. The area of the three substances can be classified based on the number, and the CT number of the three substances can be adjusted based on the calibration reference value of each target phantom region to improve the image quality for each region of the substance constituting the subject. have.

The target phantom 10 may include a marker c1 for internalizing the identification code. The marker c1 may be made of a material whose X-ray transmission characteristic is clearly distinguished from other regions of the target phantom 10, and may be identified as shown in FIG. 3 in a tomography image. The CT imaging apparatus according to the present invention, when the marker c1 is recognized, the CT number of the material m1 constituting the furthest region from the target phantom 10 to which it belongs, the CT number of the material m2 constituting the middle region, and Information about the CT number of the material m3 forming the nearest region can be extracted from a pre-stored data group, and these can be used to adjust the CT image.

When the portion corresponding to the target phantom 10 in the CT image before adjustment is recognized through the marker c1, information about the target phantom corresponding to the code represented by the marker c1 is extracted from the data group. The extracted information may include information such as a specification of the target phantom 10 including the marker c1, a material composition according to the distance from the marker c1, and a CT number according to the distance. The various materials (m1, m2, m3) that make up the target phantom 10 in this way

Once each unique CT number for is identified, the CT image is adjusted using some or all of them as calibration reference values. Various adjustment conditions for adjusting the CT image are as described above.

4 is a cross-sectional view showing a target phantom tomography according to an embodiment of the present invention. The target phantom 11 according to the present embodiment is made of three materials (m1, m2, m3) having different unique CT numbers, but the same as the embodiment of FIGS. The arrangement of the markers c1, c2, c3, which is a means of internalizing the identification code, is different. As illustrated, each of the constituent materials m1, m2, and m3 of the target phantom may be identified according to the number of unit markers.

5 is a perspective view showing a target phantom according to an embodiment of the present invention. The target phantom 12 according to the present embodiment is made of three materials m1, m2, and m3 having different unique CT numbers, and is the same as the embodiment of FIGS. 2 to 3, and the target phantom 12 The only difference is that the means for internalizing the identification code is a ratio of the size of each of the constituent materials (m1, m2, m3). As such, the unique code for identifying the CT number of the target phantom 12 or the CT number of each region belonging thereto may be internalized in various forms. For example, it can be variously internalized in the form of the shape, relative size of the target phantom each region or the shape and arrangement of the markers.

6 is a perspective view showing a target phantom according to an embodiment of the present invention. Target phantom 13 according to the present embodiment shows an example formed in the shape of a mouthpiece so that the patient can take a CT image in the state of the door between the upper and lower jaw. The unique CT number is composed of three materials (m1, m2, m3) different from each other is the same as the embodiment of Figs.

As described through the above embodiments, the target phantom may have any form as long as it can be inserted into a subject's photographing area, that is, a field of view (FOV), and a unique CT number may be used for the material forming the target phantom. Any known substance does not matter what kind of substance it is. However, in order to increase the accuracy of CT number detection on the tissue of interest of the subject, it is advantageous to have a form of a bite block or a mouthpiece made of a material similar to the tissue of interest and inserted into and photographed adjacent to the tissue of interest. .

7 is a block diagram showing the configuration of a CT imaging apparatus according to an embodiment of the present invention. The CT imaging apparatus according to the present exemplary embodiment includes an image capturing unit 21, an image processing unit 22, and a display unit 23.

The image capturing unit 21 is for acquiring CT images of a subject, and photographs a plurality of X-ray images from various angles using an X-ray generator, an X-ray sensor, and a driving device for driving the same as in a general CT imaging apparatus. do. However, it is preferable to have a configuration suitable for taking a CT image with a target phantom whose CT number is known in advance is inserted into the FOV.

The image processor 22 reconstructs a plurality of X-ray images thus obtained to acquire a tomography image corresponding to an arbitrary slice (tomography). The image processor 22 identifies the target phantom from the obtained CT image, and adjusts the CT image so that the target phantom is displayed according to a unique CT number in the CT image. To this end, the image processor 22 may include a target phantom identification module 201 for identifying the target phantom from a CT image before adjustment, and the target identified from a data group previously stored in a data storage inside or outside the CT imaging apparatus. And a target phantom data module 202 for acquiring a unique CT number corresponding to the phantom, and an image adjusting module 203 for calibrating the CT image such that the target phantom is displayed according to its unique CT number.

The target phantom data module 202 may include a data group for various target phantoms and an interface for accessing the data group to extract necessary data and transmit the data. The data population may be, for example, a kind of database structured including a variety of target phantoms or a unique code that can identify each constituent when they consist of a plurality of materials and unique CT number data corresponding to the unique code.

The image adjustment module 203 may display the CT number of the target phantom detected in the CT image before adjustment so that the target phantom is displayed on the screen of the display unit 23 according to the unique CT number. Is corrected by the unique CT number extracted by the same and applied to the rest of the pre-adjusted CT image, that is, the tissue part of the subject, to be calibrated. Increase the accuracy of CT numbers for subject tissue in adjusted CT images.

Hereinafter, the CT imaging method according to the present invention will be described.

8 is a flowchart showing a CT imaging method according to an embodiment of the present invention. According to the present embodiment, a step of acquiring a CT image in a state in which a target phantom whose unique CT number is known in advance is inserted into a CT imaging range including a subject, that is, a field of view (FOV) (s1) and the acquired CT Identifying the target phantom from an image and adjusting the CT image so that the target phantom is displayed according to a unique CT number in the CT image, which is the result of the so-called image processing step (s2) and the image processing step (s2). And an image display step (s3) of outputting the adjusted CT image in the form of a screen or a print.

Here, the image processing step (s2) identifies the unique code of the target phantom inserted in the FOV including the subject from the CT image (s21), and the unique code corresponding to the unique code identified from the previously acquired data group. Acquiring CT number data (s22), and calibrating the CT image as a whole (s23) so that the target phantom is displayed on the display screen according to its unique CT number. Each process of the image processing step (s2) may be understood in more detail through the description of the image processor 22 in the description of the CT imaging apparatus according to the embodiment of FIG.

Claims

A CT imaging unit for acquiring a CT image of a subject with a target phantom having a unique CT number; And

An image for identifying the target phantom from the CT image acquired by the CT imaging unit, and adjusting the CT image based on a difference between a CT number of the target phantom and a unique CT number of the target phantom displayed on the CT image. Including a processing unit,

CT imaging device.
The method according to claim 1,

The target phantom has two or more different unique CT numbers,

CT imaging device.
The method according to claim 1 or 2,

The target phantom has a unique code embedded in at least one of a shape, a marker, an arrangement, and a structure, and the image processor identifies the target phantom and the unique CT number with the unique code.

CT imaging device.
The method according to claim 3,

The image processor,

A target phantom identification module for identifying the target phantom from the CT image;

A target phantom data module for obtaining information about a unique CT number of the identified target phantom; And

And an image adjustment module for adjusting the CT image such that the target phantom is displayed according to a unique CT number.

CT imaging device.
The method according to claim 4,

The target phantom data module acquires a unique CT number corresponding to the target phantom identified from a data group previously stored in a data storage inside or outside the CT imaging device.

CT imaging device.
Inserted into a CT field of view (FOV) including the subject and CT scan with the subject, wherein at least two have a unique CT number,

Target patum.
The method according to claim 6,

The target phantom is a mouthpiece or bite block inserted into the subject during CT imaging,

Target phantom.
Acquiring a CT image with a target phantom having a unique CT number inserted with a subject within a CT field of view (FOV); And

Identify the target phantom from the acquired CT image, find a correction condition based on the difference between the CT number of the target phantom and the target phantom displayed on the CT image, and the CT image based on the correction condition. Including adjusting the

How to take a CT scan.
There is a target phantom having two or more unique CT numbers within a field of view (FOV) including the subject,

The target phantom is a portion corresponding to at least one of the two or more unique CT numbers is represented by a gray scale level corresponding to the unique CT number of the portion,

CT imaging.