KR20180057020A - Cone Beam Computerized Tomography System of Dual Energy Type - Google Patents

Abstract

The present invention relates to a dual-energy type cone beam computerized tomography apparatus, and an objective of the present invention is to process dual energy data quickly and easily by minimizing the angle between projection data in the dual-energy type cone beam CT of a high-speed switching scheme. To this end, the present invention comprises a vertical body unit (10) which is height-adjustable, a horizontal unit (20) which is horizontally provided on the vertical body unit (10), a rotating member (30) which is provided at an end of the horizontal unit (20) to rotate 360 degrees, an X-ray radiating unit (40) which is provided at an end of the rotating member (30) to radiate X-ray beams, and a detector (50) which is provided at the other end of the rotating member (30) to detect transmission and absorption values of the X-ray beams. The dual-energy type cone beam computerized tomography apparatus takes images by switching X-ray beams between high energy and low energy at a high speed, and takes images by rotating the rotating member (30), which rotates around a patient′s body, in a non-uniform motion.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a dual energy type cone beam computed tomography apparatus,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dual-energy cone-beam computed tomography apparatus used for photographing a part of a body, and more particularly to a cone-beam computed tomography apparatus for rotating a rotating member rotating around a body, And more particularly, to a cone beam computerized tomography apparatus capable of easily and quickly processing dual energy image data by minimizing an angle between projection data and low energy projection data, and improving the precision and quality of image information.

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.

2 (a), a fan beam CT (Fan Beam CT) for scanning a fan-shaped X-ray beam and a conical X- And Cone Beam CT (Ray Beam CT).

According to the cone beam CT, the scan area of the beam is wider than that of the fan beam CT, so that 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 high-speed switching method described above continuously switches the high energy X-ray beam and the low energy X-ray beam while rotating the rotary member 30 (also referred to as a '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.

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, there is a disadvantage that image quality may be deteriorated due to motion 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, in the cone beam CT, since the scanning area of the X-ray beam and the area of the detector 50 are larger than the fan beam CT, the acquisition speed of the image data is slowed down (see FIGS. 2A and 2B).

In order to obtain the number of projection data in the cone beam CT by the fan beam CT, there is a problem that it takes a long time to rotate the rotary member 30 one revolution.

Also, if the rotation time of the rotation member 30 is long, it is difficult to obtain accurate image information due to the motion of the patient. Therefore, the shorter the scan time of the rotation member 30 is, the better.

In the fan beam CT, about 2,000 pieces of projection data can be obtained in one rotation of the rotary member 30. [

Accordingly, in the fan beam CT, when the switching time of high energy and low energy is 0.25 ms, the scan time of the rotating member 30 is 2,000 x 0.25 ms = 0.5 sec.

Also, the angle between each projection data in the fan beam CT is 360 degrees / 2,000 sheets = 0.18 degrees.

However, in the cone beam CT, the number of frames obtainable by the detector 50 is about 60 fps (Frame Per Second), so that the projection data can not be obtained as much as the fan beam CT.

That is, in the cone beam CT, 300 high energy images and 300 low energy images can be photographed in one rotation of the rotary member 30.

Accordingly, in the cone beam CT, when the frame rate of the detector is 60 fps and the projection data is 600 days, the scan time of the rotary member 30 becomes 10 seconds.

Also, the angle between each projection data in the cone beam CT is 360 degrees / 600 sheets = 0.6 degrees.

That is, in the cone beam CT, the angle between each projection data is about 3.3 times larger than that of the fan beam CT.

If the angle between the projected line data increases, the dual energy processing becomes complicated and it becomes difficult to realize a high-quality image.

Further, 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 (dotted line)" in a straight line shape, and the actual voltage spectrum becomes "b (solid line)" in a curved shape.

That is, according to the conventional dual energy cone beam CT of the high-speed switching system, a voltage spectrum which does not contribute to image information in a voltage transition period occurs in addition to a certain level of high energy and low energy.

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

Disclosure of Invention Technical Problem [8] The present invention has been made to solve the above-mentioned problems of the prior art, and it is an object of the present invention to provide a dual energy cone beam CT of a high speed switching system capable of quickly and easily processing dual energy data by minimizing the angle between projection data There is a purpose.

Another object of the present invention is to solve the disadvantages of the high-speed switching method in the dual energy cone beam CT.

Another object of the present invention is to minimize the angle between high energy projection data and low energy projection data in a dual energy cone beam CT of a high speed switching system in which the number of frame rates and projection data is limited, .

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, Energy beam of a dual energy system for taking a picture while alternately switching to a low energy mode, wherein the rotating member rotating around the patient's body is rotated while being rotated by a semi-circular motion.

And the rotating member is rotated while being repeatedly accelerated and decelerated at regular intervals.

And the rotational speed of the rotary member is controlled by a sinusoidal curve in which a high speed and a low speed are repeated.

It is also characterized in that the high energy X-ray beam is subjected to high energy imaging in the section having the maximum energy level (section A) and the low energy imaging is performed in the section having the minimum energy level (the section B) with the low energy X-ray beam .

According to the present invention, in the dual energy cone beam CT of the high-speed switching system, the angle between the respective projection data is minimized, so that the dual energy data can be processed quickly and easily.

Also, since the high-speed switching method can be easily implemented in the dual-energy cone-beam CT, the advantage of the high-speed switching method can be maximized.

In addition, in the dual energy cone beam CT of the high-speed switching system in which the number of frame rates and the number of projection data is limited, the angle between the high energy projection data and the low energy projection data is minimized, thereby obtaining high quality image data.

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 shows energy levels of an X-ray beam in a dual energy system according to the prior art.
4 is a view showing a rotational speed of a rotating member according to the prior art;
5 is a view showing the rotational speed of the rotating member according to the present invention.
6 is a view showing a time point of photographing a high energy image and a low energy image according to the present invention;

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

The dual energy cone beam CT of the high speed switching system according to the present invention includes a vertical body 10 capable of height adjustment, a horizontal part 20 horizontally provided on the upper part of the vertical body 10, An X-ray radiating part 40 provided at one end of the rotating member 30 and scanning the X-ray, and a rotating member 30 provided at an end of the rotating member 30, And a detector 50 provided at the other end of the X-ray detector 30 for detecting the transmission absorption value of the X-ray. The detector 50 switches the X-ray to high energy and low energy, In a cone beam computerized tomography apparatus of a dual energy system, the rotating member 30 rotating around a patient's body is photographed while rotating in a semi-circular motion.

That is, the present invention is characterized not by rotating the rotary member 30 at a constant speed as in the prior art, but by rotating the rotary member 30 while repeating acceleration and deceleration at regular intervals.

Further, the rotational speed of the rotary member 30 may be controlled by a sinusoidal curve in which high and low speeds are repeated.

Hereinafter, the technical differences between the prior art and the present invention will be described with reference to FIGS. 4 and 5. FIG.

4 shows a case of rotating the rotating member 30 at a constant speed in a conventional dual energy cone beam CT.

In FIG. 4, the abscissa represents the time (sec), and the ordinate represents the rotation speed of the rotary member 30. The frame rate of the detector 50 is 60 fps and the projection data is 600 sheets.

According to the above-described conditions, the scan time per rotation of the rotary member 30 is 10 seconds.

Accordingly, as shown in Fig. 4, six sheets of high projection data and six sheets of low projection data are obtained in 0.2 seconds.

Since the horizontal axis represents time (sec) and the vertical axis represents the rotation speed (deg / sec), the hatched area in FIG. 4 becomes the angle at which the rotary member 30 moves, 0.0167 = 0.6 degrees.

However, according to the present invention, as shown in FIG. 5, the moving angle of the rotary member 30, that is, the hatched area becomes 0.218.

The hatched area in FIG. 5 can be calculated by the following equation (1).

That is, according to the present invention, the angle at which the rotary member 30 is moved during the high-energy photographing and the low-energy photographing becomes smaller than the conventional angle.

This is because, in the present invention, when the high energy photographing and the low energy photographing are not performed, the speed of the rotary member 30 is increased.

Thus, the angle between the high energy projection data and the low energy projection data can be minimized.

By minimizing the angle between the high energy projection data and the low energy projection data, the dual energy processing process is simplified, and higher quality image data can be obtained.

Also, as shown in FIG. 3, the high-speed switching method has a transition period 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.

Thus, as shown in Fig. 3, the energy spectrum is not formed as a straight line "a (dotted line) ", but is in the form of a curve" b (solid line) ".

However, in FIG. 3, the "b1" period and the "b2" period are intermediate energy states between the high energy and the low energy, and thus do not help acquire image information.

6, the high energy X-ray beam is subjected to high energy imaging in a section (section A) having the maximum energy level, and the low energy X-ray beam is irradiated with the minimum energy And low energy is taken in a section having a level (section B).

In the upper part of FIG. 6, the horizontal axis represents time and the vertical axis represents energy level according to voltage.

Hereinafter, the operation and effect of the dual energy 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 port 42 and the detector 50 (see FIG. 1) Determine the number of copies per shot.

Then, while the rotary member 30 is rotated 360 degrees, the X-ray beam is radiated from the X-ray radiation 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 above-mentioned dual energy systems, the high-speed switching system alternately switches between a high energy beam and a low energy beam and emits them by switching at a high speed.

However, according to the cone beam CT of the high-speed switching system, since the scanning area of the X-ray beam and the area of the detector 50 are wider than the fan beam CT, the acquisition speed of the image data is slowed down.

In contrast, in the cone beam CT, the maximum number of frames that can be obtained by the detector 50 per one revolution is about 60 fps, so that projection data equivalent to the fan beam CT can not be obtained (in the case of the fan beam CT, I can do it.

That is, in the dual energy type cone beam CT, the number of the frame rate and the projection data is very limited as compared with the fan beam CT.

As a result, dual energy processing of the cone beam CT becomes difficult.

According to the present invention, however, the angle between the high-energy projection data and the low-energy projection data can be minimized by rotating the rotary member at a high speed in a section where shooting is not performed and by rotating the rotary member at low speed in a shooting section.

Accordingly, the dual energy data can be easily and quickly processed while applying the high-speed switching method, and the quality of the image information can be improved.

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-
50: Detector
60:

Claims (4)

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- And a dual energy type Cone Beam for photographing while switching the X-ray to high energy and low energy at a high speed. In a computed tomography apparatus,
Wherein the rotating member (30) rotating around the patient's body is rotated while being rotated by a semi-circular motion. The method according to claim 1,
Wherein the rotating member (30) is rotated while being repeatedly accelerated and decelerated at regular intervals. The method according to claim 1,
Wherein the rotational speed of the rotary member (30) is controlled by a sinusoidal curve in which a high speed and a low speed are repeated. The method according to claim 1,
The high energy X-ray beam is photographed at a high energy in a section having a maximum energy level (section A), and the low energy X-ray beam is photographed at a low energy part in a section having a minimum energy level (section B) A dual-energy cone-beam computed tomography apparatus.

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