KR20180057024A - Cone Beam Computerized Tomography System Having Seperate Type Filter - Google Patents

Abstract

The present invention relates to a cone beam computed tomography device with a separation type filter capable of easily separating a spectrum of high energy and low energy having a desired energy level in a cone beam CT which applies a dual energy type. The present invention comprises: a vertical body unit (10) which controls the height; a horizontal unit (20) which is horizontally provided on an upper part of the vertical body unit (10); a rotation member (30) which is provided on an end unit of the horizontal unit (20) and is rotated 360 degrees; an X-ray radiating unit (40) which is provided on one end of the rotation member (30) and irradiates X-rays; and a detector (50) which is provided on the other end of the rotation member (30) and detects a transmission absorption value of the X-rays. The dual energy type cone beam computed tomography device, which shoots the X-rays by alternately switching the X-rays between the high energy and the low energy, further comprises a filter (70) and a filter holder (80). The filter (70) is provided in a front side of the X-ray radiating unit (40) and selectively passes a high energy beam and a low energy beam. The filter holder (80) fixes the filter (70) in the X-ray radiating unit (40). The detector (50) obtains high energy image data and low energy image data in half.

Description

Technical Field [0001] The present invention relates to a cone beam computed tomography system having a split filter,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cone-beam computed tomography apparatus having a split-type filter used for photographing a part of a human body, and more particularly to a cone-beam computed tomography apparatus for selectively passing a high energy beam and a low energy beam to the front surface of an X- Ray beam spectra of high energy and low energy, thereby preventing an X-ray beam of an intermediate energy state which does not contribute to image information from being injected into the patient And a dual-energy cone-beam computed tomography apparatus capable of precisely matching the position of the filter with the image of a detector.

Generally, in order to perform an implant treatment or an artificial tooth in a dental clinic, the inside of the mouth is photographed with a computer tomography apparatus to acquire image information of the tooth.

Fig. 1 shows an example of such a computer tomography apparatus.

As shown in FIG. 1, the conventional computerized tomography apparatus includes a vertical body 10 capable of height adjustment, a horizontal part 20 horizontally provided on the upper part of the vertical body part 10, An X-ray radiating part 40 provided at one end of the rotary member 30 to scan the X-ray, A detector 50 provided at the other end of the rotary member 30 for detecting the transmission absorption value of the X-ray, and an operation unit 60 for operating the computer tomography apparatus.

The computer tomography apparatus (hereinafter, simply referred to as 'CT') allows the oral cavity of the patient to be positioned between the X-ray radiating part 40 and the detector 50, An X-ray beam is injected into the oral cavity portion of the patient through the X-ray radiating port (42) while being rotated on the road.

After the X-ray transmission absorption value is detected by the detector 50, the analog signal thus collected is converted into a digital signal, and the signal is processed by a computer to acquire a three-dimensional image.

The image information thus obtained is used for implant treatment, for treating teeth, or for producing artificial teeth.

As shown in FIG. 2A, the CT described above includes a fan beam CT for scanning a fan-shaped X-ray beam, a cone beam CT for scanning a cone-shaped X-ray beam, Beam CT).

According to the cone beam CT, a more accurate three-dimensional image can be obtained.

Generally, X-rays are generated by accelerating electrons emitted from the anode by applying a high voltage between a cathode (a filament is also used) and an anode provided in the X-ray tube, And is generated by impinging electrons on a target anode.

For example, when an X-ray voltage of 80 kV is applied, the generated X-ray becomes a spectrum having an energy level of 0 to 80 keV.

Also, when X-rays pass through the human body, X-rays of low energy range are absorbed by the human body.

Accordingly, the X-ray after the human body has a spectrum of a higher energy region band than that before transmission, which is called beam hardening.

In addition, there is a method of acquiring image information of a tooth by radiating an X-ray having different energy levels, which is referred to as a dual energy method.

In the dual energy system, a relatively high energy is called a high energy and a relatively low energy is called a low energy.

For example, a voltage of 120 kV may be applied to obtain high energy, and a voltage of 60 kV may be applied to obtain low energy.

According to the dual energy system described above, accurate image information can be obtained by separating the hard tissues (bones) and the soft tissues (bones) of the human body, and the bone density can be accurately measured based on the information.

As the dual energy method, a fast kV switching method, a dual source method, a double detector (Sandwich Detector) method, and an alternating rotation method are known.

The above-described high-speed switching scheme continuously switches the high energy beam and the low energy beam while rotating the rotary member 30 (also called 'gantry').

That is, the high-speed switching system alternately rotates the rotary member 30 at a high speed while rotating the high-energy X-ray beam and the low energy X-ray beam at a high speed.

For example, if it is assumed that 360 frames are photographed when the rotary member 30 rotates 360 degrees (actually, about 600 frames or more are photographed), the high energy beam is scanned when the rotation angle of the rotary member is 1 degree, In the case of a low energy beam, the low energy beam is scanned and the above process is repeated until it reaches 360 degrees.

That is, as shown in FIG. 4, a high energy X-ray beam is scanned to photograph one sheet (a), and then a low energy beam is scanned to photograph one sheet (b) (C).

Thus, only one of the high energy image data or the low energy image data is stored in one image data.

In the dual-source method, two sources for radiating X-rays are used, and images are taken at different angles, so that a plurality of expensive X-ray sources must be provided.

The double detector method is a method of acquiring high energy data and low energy data in a detector formed of two layers. The dual detector system also requires two detectors, which is disadvantageous in that it is expensive.

In addition, the alternating rotation method is a method of changing to high energy and low energy each time the rotating member rotates.

In other words, high energy data is obtained at one rotation and low energy data is obtained at the next rotation. However, the apparatus is complicated and image quality may be deteriorated due to movement of the patient.

The present invention relates to a cone beam CT employing a high-speed switching scheme among the dual energy schemes described above.

However, according to the cone beam CT of the conventional high-speed switching system, as shown in FIG. 3, a voltage transition period exists and a transition for reaching the target voltage at the time of switching between high energy and low energy A transition time is required.

That is, it takes a certain amount of time to rise from a low energy to a certain level of high energy, and it also takes a certain time to fall from a high energy to a low energy.

Thus, as shown in Fig. 3, the voltage spectrum does not become a "a (dotted line)" in a straight line shape but actually becomes a "b (solid line)" in a curved shape.

This makes it difficult to clearly separate high energy and low energy, and it is difficult to obtain accurate image information.

In addition, the X-ray beam which is not helpful for the image information is continuously injected to the patient, thereby increasing the X-ray dose.

Also, in the conventional CT using the fixed filter, there is a problem that the alignment work of the filter and the detector image is not easy.

As a result of retrieving the prior art related to the present invention, a large number of patent documents have been searched, and some of them will be described as follows.

Patent Document 1 discloses a correction method for correcting an inclination of the two-dimensional projection data when reconstructing a plurality of two-dimensional projection data input from an X-ray city photographing apparatus into a three-dimensional image through mathematical calculation, A first step of receiving 2D projection images obtained by scanning a physical phantom in the 2D projection image and detecting boundary lines of the physical phantom in the 2D projection image; A second step of calculating at least one straight line component of the boundary lines and calculating a slope of the straight line component as a slope of each of the two-dimensional projection data; A third step of rotationally transforming each of the two-dimensional projection data by an inclination to correct the inclination; And a fourth step of reconstructing each of the two-dimensional projection data obtained by correcting the tilting into a three-dimensional image. The tilting correction method of the X-ray city photographing apparatus is described.

In addition, Patent Document 2 discloses a technique of preparing a virtual model, placing the center point of the virtual model on the X-ray city radiographic apparatus in such a manner as to be aligned with the central point of the central axis of the X-ray city radiographing apparatus, The center plan data of the virtual model and the center points of the respective detector plan data are compared with each other to obtain a plurality of detector plan data, A central axis movement of the X-ray CT apparatus, which obtains a movement value of each of the middle plan data of the virtual model, and then corrects movement of the center point of the central axis of the X- And a method of correcting the error is described.

Patent Document 3 also discloses a combined imaging apparatus for x-ray imaging of a subject in a plurality of modes, the imaging apparatus comprising a support structure having an elongated rotating arm, A computer tomography detector and a panoramic imaging detector that are mounted adjacent to the movable platen; and a controller operable to move the position of the movable platen to at least one of the first and second positions relative to the x- Ray source, wherein the first location places the computerized tomographic detector in a direct path of the x-ray source, and the second location places the panoramic imaging detector within the direct path of the x-ray source The present invention is directed to a combined imaging apparatus in which a plurality of imaging units are arranged.

Korean Patent No. 10-1211141 Korean Patent Laid-Open No. 10-2009-41649 Korean Patent Laid-Open No. 10-2012-18758

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems of the prior art, and it is an object of the present invention to easily separate a high energy and a low energy spectrum having a desired energy level in a cone beam CT employing a dual energy method.

Another object of the present invention is to prevent X-ray beam which is not helpful for image information from being injected into a patient in a dual energy type cone beam CT, thereby reducing the X-ray dose of the patient.

It is still another object of the present invention to improve the accuracy and quality of image information by storing a high energy image and a low energy image together in one detector projection data.

It is still another object of the present invention to enable accurate matching of images of a filter and a detector.

According to an aspect of the present invention, there is provided a vertical body including a vertical body portion having a height adjustable, a horizontal portion horizontally provided on the vertical body portion, a rotary member provided at an end portion of the horizontal portion, An X-ray radiating part provided at one end of the rotary member for scanning the X-ray, and a detector provided at the other end of the rotating member for detecting the transmission absorption value of the X-ray, And a low energy beam, the low energy beam being passed through the X-ray radiating unit, and a filter for passing the high energy beam and the low energy beam selectively, - a filter holder for fixing to the radiation emitter, wherein in the detector the high energy image data and the low energy image data Characterized in that the acquisition by half.

And the n-th high energy image or the low energy image, and the (n + 1) -th high energy image or the low energy image are overlapped with each other.

Further, the filter has a rectangular shape, and the first filter and the second filter of different materials are formed in half.

In addition, one of the first filter and the second filter blocks the low energy region relatively more in the X-ray spectrum so that the ratio of the high energy region is increased, and the other passes the low energy region So that the ratio is increased.

Further, any one of the first filter and the second filter is made of copper, and the other is made of aluminum.

The filter is characterized by comprising a first filter made of a metal and an empty space.

And the space portion allows a low energy beam to pass therethrough.

Further, the filter holder is characterized in that the filter holder is provided so as to be able to move up and down and right and left, or rotate with respect to the X-ray radiating part.

And a plurality of arc-shaped slots are formed in the filter holder, and are fixed to the X-ray radiation part by bolts.

Further, a fixing hole is formed in the lower part of the filter holder, and an arc-shaped slot is formed in the upper part.

Further, a fixing hole is formed in a lower portion of the filter holder, and an angle adjusting bolt and a nut are provided on one side of the filter holder, and a spring member is provided on the other side of the upper side.

According to the present invention, in a cone beam CT adopting a dual energy system, there is an effect that a high energy having a desired energy level and a low energy spectrum can be easily separated.

Also, in a dual-energy cone beam CT, it is possible to reduce the X-ray dose of the patient by preventing the patient from being injected with an intermediate energy X-ray beam that does not contribute to image information.

Also, since both the high energy image and the low energy image can be acquired at the same position, the accuracy and quality of the image information can be improved.

1 is a perspective view of a conventional cone-beam computed tomography apparatus.
FIG. 2A is a sectional view of a conventional fan beam, and FIG. 2B is a sectional view of a cone beam.
3 is a diagram showing energy levels of an X-ray beam in a dual energy system according to the prior art.
4 is a diagram illustrating a process of acquiring high energy image data and low energy image data in a dual energy system according to the related art.
FIG. 5 illustrates a process of acquiring high energy image data and low energy image data in a dual energy scheme according to the first embodiment of the present invention. FIG.
6 shows a filter according to a first embodiment of the present invention.
7A is a view showing a filter holder according to a first embodiment of the present invention.
Figure 7b shows a filter holder according to a second embodiment of the present invention.
7C shows a filter holder according to a third embodiment of the present invention.
8 shows a filter according to a fourth embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

≪ Embodiment 1 >

5, 6 and 7A show a first embodiment of the present invention.

The cone beam CT according to the first embodiment of the present invention includes a vertical body 10 having a height adjustable, a horizontal portion 20 horizontally provided on the vertical body 10, An X-ray radiating part 40 provided at one end of the rotating member 30 and scanning the X-ray, a rotating member 30 provided at an end of the rotating member 30, 30 for sensing the transmission and absorption of X-rays, and a detector (50) for detecting the transmission and absorption of X-rays. The detector (50) A Cone Beam computed tomography apparatus of a dual energy type includes a filter 70 provided in front of the X-ray radiation unit 40 for selectively passing a high energy beam and a low energy beam, And a filter holder (80) for fixing the filter (70) to the X-ray radiation part (40) .

Here, in the detector 50, high energy image data and low energy image data are acquired at the same time.

That is, as shown in FIG. 5, an image by a high energy X-ray beam and an image by a low energy X-ray beam are acquired in half on a single photograph.

As shown in FIG. 4, the conventional high-speed switching method among the dual energy systems alternately acquires the high energy image and the low energy image.

That is, in the conventional method, the high energy image is acquired by radiating only the high energy beam at one position while rotating the rotary member 30, and then only the low energy beam is radiated to acquire the low energy image.

Accordingly, only a high energy image is stored in a in FIG. 4, only a high energy image is stored in b, and a high energy image is stored again in c.

That is, according to the conventional method, it is impossible to acquire both the high energy image and the low energy image at the same position.

However, according to the present invention, the n-th row energy image and the (n + 1) -th high energy image are photographed so as to overlap each other.

Accordingly, both the high energy image data and the low energy image data can be obtained at the same position, and the half high energy image and the low energy image are separately stored.

As a result, the high energy beam spectrum and the low energy beam spectrum can be completely separated from each other, thereby improving the quality of image information.

Further, the filter 70 according to the present invention may be formed in a rectangular shape as shown in FIG.

Here, the first filter 70a and the second filter 70b of different materials are preferably formed in the filter 70 in half.

One of the first filter 70a and the second filter 70b blocks a relatively low energy region in the X-ray spectrum so that the ratio of the high energy region is increased.

And the other filter is passed so that the ratio of the low energy region is higher than that of the high energy region.

Also, any one of the first filter 70a and the second filter 70b may be made of copper and the other may be made of aluminum.

However, the present invention is not limited thereto, and the shape and material of the filter 70 may be variously configured.

The filter holder 80 for fixing the filter 70 is provided so as to be able to move up or down or to move left or right with respect to the X-ray radiating part 40.

Accordingly, when the position of the filter holder 80 is adjusted, the position of the filter 70 can be adjusted.

The filter 70 may be detachably attached to the filter holder 80 to facilitate maintenance.

Although not shown in the drawing, the filter holder 80 is formed with a hole through which the X-ray beam emitted from the X-ray radiating port 42 passes.

7A, the filter holder 80 according to the first embodiment of the present invention has a plurality of arc-shaped slots 81 formed on the outer periphery of the filter 70, It may be fixed to the radiation portion 40 or a separate structure.

With the above structure, the image of the filter 70 and the detector 50 can be precisely matched while the position of the filter holder 80 is adjusted.

Hereinafter, the operation and effect of the cone beam CT according to the present invention will be described.

In order to photograph the tooth state in the oral cavity by the cone beam CT, the oral cavity portion of the patient is positioned between the X-ray radiating portion 40 and the detector 50, and then the number of images to be photographed per rotation is determined on the operation portion 60 (See Fig. 1).

Then, the rotary member 30 is rotated 360 degrees so that the X-ray beam is radiated from the X-ray radiating port 40.

Then, the detector 50 detects the absorption absorption value of the X-ray, and the analog signal thus collected is converted into a digital signal.

Then, the digital signal is processed to acquire a three-dimensional image. The obtained image information is used for implant treatment, tooth treatment, or artificial tooth preparation.

Dual energy can also be used for bone density diagnosis or more accurate image acquisition.

Among the dual energy schemes described above, the high-speed switching scheme alternately switches between a high energy beam and a low energy beam.

However, according to the high-speed switching method, as shown in FIG. 3, transition periods exist in the process of switching between high energy and low energy, respectively.

It takes a certain amount of time to rise from a low energy to a certain level of high energy, and it takes a certain time to fall from a high energy to a low energy.

Accordingly, as shown in Fig. 5, the energy spectrum is not formed as a straight line "a (dotted line) ", but is in the form of a curve" b (solid line) " .

In the present invention, the X-ray beam is not scanned in the human body in the section that does not help acquisition of the image information. To this end, a filter 70 is provided in front of the X-ray radiation port 42.

In order to obtain accurate image information, it is ideal to acquire both a high energy image and a low energy image at the same position.

However, according to the dual energy method of switching the high energy beam and the low energy beam while rotating the rotating member, it is impossible to acquire both the high energy image and the low energy image at the same position.

In order to solve the problem of the dual energy system as described above, the filter 70 comprises the first filter 70a and the second filter 70b in half.

Also, any one of the first filter 70a and the second filter 70b blocks a relatively low energy region in the X-ray spectrum and passes the high energy region at a high ratio.

And the other passes through the lower energy region at a higher ratio than the high energy region.

In addition, in the detector 50, the high energy image and the low energy image are distinguished from each other by half by the structure of the filter 70.

The n-th high energy image or the low energy image and the (n + 1) -th high energy image or the low energy image are superimposed on each other in half.

According to the present invention, since the high energy image and the low energy image can be separated in half and can be obtained in half, processing of the image data is simplified.

Also, since both the high energy image and the low energy image can be acquired at the same position, the disadvantage of the high speed switching method can be solved.

Also, since the nth image and the (n + 1) th image at the same position are separately stored, the high energy image and the low energy image can be separately processed.

≪ Embodiment 2 >

7B shows a second embodiment of the present invention.

The second embodiment of the present invention is a modification of the structure of the filter holder 80 in the first embodiment described above.

That is, as shown in FIG. 7B, a fixing hole 82 is formed in a lower portion of the filter holder 80, and an arc-shaped slot 81 is formed in an upper portion.

A pin (not shown) having a rotatable structure is assembled to the fixing hole 82, and a bolt is assembled in the arc-shaped slot 81.

According to the above-described structure, the filter holder 80 can be rotated at a certain angle around the pin assembled in the fixing hole 82.

Accordingly, the position of the filter 70 and the image of the detector 50 can be accurately aligned.

The other points are the same as those in the first embodiment, and therefore duplicate descriptions will be omitted.

≪ Third Embodiment >

7C shows a third embodiment of the present invention.

The third embodiment of the present invention is a modification of the structure of the filter holder 80 in the above-described first embodiment.

7C, a fixing hole 82 is formed in a lower portion of the filter holder 80. An angle adjusting bolt 83 and a nut 84 are provided at one side of the upper portion and a spring member 85 is provided at an upper side of the filter holder 80, .

A pin (not shown) having a rotatable structure is assembled to the fixing hole 82, and the nut 84 is fixed to the X-ray radiating part 40 or a separate structure.

According to the above structure, the image of the filter 70 and the detector 80 can be made to coincide with each other by rotating the bolt 83 and moving the filter holder 80.

The other items are the same as those in the first embodiment described above.

<Fourth Embodiment>

Fig. 8 shows a fourth embodiment of the present invention.

8, the filter 70 includes a first filter 70a made of a metal and an empty space 70c. The first filter 70a is made of a metal, .

Here, the space D is for passing a low energy beam.

The other points are the same as those in the first embodiment, and therefore duplicate descriptions will be omitted.

The foregoing description of preferred embodiments of the present invention has been provided for purposes of illustration and description. It will be understood by those skilled in the art that various changes and modifications may be made without departing from the scope of the present invention.

10: vertical body part
20:
30: Rotating member
40: X-
42: X-ray discharger
50: Detector
60:
70: Filter
70a: first filter
70b: second filter
70c:
80: Filter Holder
81: Circular slot (Slot)
82: Fixing hole
83: Angle adjusting bolt
84: Nut
85: spring member

Claims (11)

A horizontal part 20 provided horizontally on the upper part of the vertical body part 10 and a rotary part 20 provided on the end part of the horizontal part 20 and rotated 360 degrees, An X-ray radiating part 40 provided at one end of the rotary member 30 for scanning the X-ray, and an X- A dual energy type Cone Beam computer which includes a detector 50 for detecting X-rays while alternately switching between X-rays with high energy and low energy, In the tomographic imaging apparatus,
A filter 70 disposed in front of the X-ray radiating part 40 for selectively passing the high energy beam and the low energy beam, and a filter 70 for fixing the filter 70 to the X- Further comprising a filter holder (80)
Wherein the detector (50) acquires the high energy image data and the low energy image data in one sheet at a time. The method according to claim 1,
the n-th high energy image or the low energy image, and the (n + 1) -th high energy image or the low energy image overlap each other. The method according to claim 1,
Wherein the filter (70) has a rectangular shape, and a first filter (70a) and a second filter (70b) of different materials are formed in half. The method of claim 3,
One of the first filter 70a and the second filter 70b blocks a relatively low energy region in the X-ray spectrum so that the ratio of the high energy region is increased, and the other passes through the high energy region Wherein the ratio of the lower energy region is higher than that of the lower energy region. The method of claim 3,
Wherein one of the first filter (70a) and the second filter (70b) is made of copper and the other is made of aluminum. The method according to claim 1,
Wherein the filter (70) comprises a first filter (70a) made of a metal and an empty space (70c). The method according to claim 6,
Wherein the space (D) allows a low energy beam to pass therethrough. The method according to claim 1,
Wherein the filter holder (80) is provided so as to be capable of being moved up or down, left or right, or rotated with respect to the X-ray radiating part (40). 9. The method of claim 8,
Wherein a plurality of arc-shaped slots (81) are formed in the filter holder (80) and are fixed to the X-ray radiating part (40) or another structure by bolts. 9. The method of claim 8,
Wherein a fixing hole (82) is formed in a lower portion of the filter holder (80), and an arc-shaped slot (81) is formed in an upper portion of the filter holder (80). 9. The method of claim 8,
A fixing hole 82 is formed in a lower portion of the filter holder 80 and an angle adjusting bolt 83 and a nut 84 are provided on an upper side of the filter holder 80 and a spring member 85 is provided on the other side of the upper portion. Computer tomography apparatus.

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