KR101732961B1 - Multi- gamma source CT image reconstruction method and apparatus - Google Patents

Multi- gamma source CT image reconstruction method and apparatus Download PDF

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KR101732961B1
KR101732961B1 KR1020150114633A KR20150114633A KR101732961B1 KR 101732961 B1 KR101732961 B1 KR 101732961B1 KR 1020150114633 A KR1020150114633 A KR 1020150114633A KR 20150114633 A KR20150114633 A KR 20150114633A KR 101732961 B1 KR101732961 B1 KR 101732961B1
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image
gamma
projection image
subject
source
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KR20170020647A (en
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조승룡
위선희
박미란
장지은
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한국과학기술원
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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
    • A61B6/52—Devices using data or image processing specially adapted for radiation diagnosis
    • A61B6/5211—Devices using data or image processing specially adapted for radiation diagnosis involving processing of medical diagnostic data
    • A61B6/5229—Devices using data or image processing specially adapted for radiation diagnosis involving processing of medical diagnostic data combining image data of a patient, e.g. combining a functional image with an anatomical image
    • A61B6/5235—Devices using data or image processing specially adapted for radiation diagnosis involving processing of medical diagnostic data combining image data of a patient, e.g. combining a functional image with an anatomical image combining images from the same or different ionising radiation imaging techniques, e.g. PET and CT
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
    • A61B6/42—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment with arrangements for detecting radiation specially adapted for radiation diagnosis
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
    • A61B6/42—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment with arrangements for detecting radiation specially adapted for radiation diagnosis
    • A61B6/4208—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment with arrangements for detecting radiation specially adapted for radiation diagnosis characterised by using a particular type of detector
    • A61B6/4258—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment with arrangements for detecting radiation specially adapted for radiation diagnosis characterised by using a particular type of detector for detecting non x-ray radiation, e.g. gamma radiation

Abstract

A method and apparatus for reconstructing multiple gamma source CT images are disclosed. Irradiating a gamma ray to an empty space by a predetermined sequence of gamma ray sources of one of a plurality of same gamma ray sources to obtain a projected image of an empty space, irradiating the subject simultaneously with gamma rays emitted from a plurality of same gamma ray sources, Estimating a projected image of the subject for each of the gamma-ray sources using the obtained projected image of the empty space, the projected image of the subject, and the reconstructed fundamentally reconstructed image, and reconstructing the projected image of the estimated subject, .

Description

{Multi-gamma source CT image reconstruction method and apparatus}

The present invention relates to an image reconstruction method, and more particularly, to a CT image reconstruction method and apparatus using multiple gamma sources simultaneously as a source.

Currently, multicolor x-ray irradiation apparatus is dominantly used as a source of computerized tomography apparatus. These irradiation devices generate accelerating electrons by hitting the target metal to generate X-rays, and thus have a multi-color energy, which causes a problem of lowering the quality of reconstructed 3D CT images.

First, the energy used to obtain the actual projection image is multicolor. However, since the 3D reconstruction algorithms currently used assume a monochromatic X-ray, the attenuation coefficient of the reconstructed image can be estimated differently from the actual one. This is called beam hardening phenomenon, and the damping coefficient of the central part of the reconstructed image is estimated to be low. In reality, a uniform reconstructed image is reconstructed as a cup-like distorted image as a whole.

Second, when the maximum x-ray tube voltage is used to lower the noise of the reconstructed image, the compton scattering ratio between the x-ray and the object is increased. The higher the ratio of the photoelectric effect, which does not change the direction of the X-ray beam, the better the quality of the reconstructed image. If the ratio of the complex scatter increases, the contrast of the lesion and the soft tissue having a low attenuation coefficient is greatly reduced.

This is not a good quality image for diagnosis. However, when a monochromatic energy image is reconstructed with a commercialized dual energy CT device, the contrast in the soft tissue is maintained and a very low image noise can be obtained. In this case, two scans are performed at different maximal x-ray tube voltages in order to obtain a good quality image, which causes a problem that the dose received by the patient is increased.

Finally, there is a problem that it is difficult to reconstruct quantitative CT images when multiple sources of energy are used as a source. Quantitative CT images are images that provide physicians with CT images taken at different hospitals or on different days with the same conditions, replacing reconstructed images with relative HU values for each CT. This is also directly related to the dose problem delivered to the patient.

Therefore, there is a study to solve the problem of lowering the dose received by the patient by reconstructing the quantitative CT image.

Korean Patent Laid-Open Publication No. 10-2012-0020623 relates to fusion of a dual-ring magnetic resonance imaging apparatus and a gamma knife for systemic treatment into a single complex medical apparatus, thereby simultaneously performing imaging diagnosis and radiation treatment.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and apparatus for reconstructing multiple gamma source CT images that fundamentally reduce beam curing, which is a major cause of degradation of reconstructed image quality in a conventional CT imaging apparatus.

It is another object of the present invention to provide a method and apparatus for reconstructing multiple gamma source CT images, which enables reconstruction of a quantitative CT image with only one scan by using a source of monochromatic energy.

In order to solve the above object,

According to another aspect of the present invention, there is provided a method for reconstructing multiple gamma source CT images,

Irradiating a gamma ray to an empty space by a predetermined sequence of gamma ray sources of one of a plurality of same gamma ray sources to obtain a projected image of an empty space, irradiating the subject simultaneously with gamma rays emitted from a plurality of same gamma ray sources, Estimating a projected image of the subject for each of the gamma ray sources using the obtained projection image of the hollow space, the projected image of the subject, and the reconstructed fundamentally reconstructed image, and reconstructing the projected image of the estimated subject And generating a corrected reconstructed image.

The multiple gamma source CT image reconstruction apparatus according to the present invention comprises:

A plurality of gamma-rays are formed at predetermined intervals, a gamma ray emitted from the gamma-ray source is projected into an empty space and a subject, and a plurality of gamma sources, which receive the projected images of the object and the projected empty space, A controller for computing and estimating a projection image corresponding to each gamma-ray source using the computed tomography (CT) unit and the received projection image, and reconstructing the separated projection image to generate a reconstructed image; .

According to the method and apparatus for reconstructing multiple gamma source CT images according to the present invention, beam curing phenomenon, which is a main cause of degradation of reconstructed image quality generated in a conventional CT imaging apparatus, can be fundamentally reduced.

In addition, using a single source of energy, it is possible to reconstruct a quantitative CT image with only one scan, thereby enhancing the contrast between the lesion and the soft tissue to improve the lesion detection rate of the reconstructed image.

FIG. 1 is a conceptual diagram for explaining a multiple gamma source CT image reconstructing apparatus according to an embodiment of the present invention.
FIG. 2 is an exemplary diagram for explaining a projection image estimation according to an exemplary embodiment of the present invention. Referring to FIG.
FIGS. 3A through 3E are diagrams for explaining a procedure of reconstructing multiple gamma source CT images according to an exemplary embodiment of the present invention.
FIG. 4 is an exemplary view illustrating a reconstruction image of a gamma-ray source position of a multiple gamma source CT image reconstructing apparatus according to an exemplary embodiment of the present invention. Referring to FIG.
FIG. 5 is an exemplary view for explaining a projection image estimation for a gamma ray source position of a multiple gamma source CT image reconstructing apparatus according to an embodiment of the present invention. Referring to FIG.
6 is a flowchart illustrating a method for reconstructing multiple gamma source CT images according to an embodiment of the present invention.
7 is a flowchart illustrating a method of estimating a projection image according to an embodiment of the present invention.
FIG. 8 is a flowchart illustrating a video reconstruction method according to an embodiment of the present invention.
9 is a flowchart illustrating a method for reconstructing multiple gamma source CT images according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals as used in the appended drawings denote like elements, unless indicated otherwise. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather obvious or understandable to those skilled in the art.

FIG. 1 is a conceptual diagram for explaining a multiple gamma source CT image reconstructing apparatus according to an embodiment of the present invention.

Referring to FIG. 1, the multiple gamma source CT image reconstructing apparatus 1 fundamentally reduces the beam hardening phenomenon, which is a main cause of degradation of reconstructed image quality generated in a conventional CT imaging apparatus. The CT reconstruction device (1) enables reconstruction of quantitative CT images with only one scan by using a source of monochromatic energy. The multiple gamma source CT image reconstructing apparatus 1 includes a multiple gamma source computed tomography (CT) unit 100, a control unit 200, an output unit 300, and a storage unit 400.

The multiple gamma source CT unit 100 sets a plurality of identical gamma ray sources at predetermined intervals, and gamma rays emitted from the formed gamma ray sources project the subject. The multiple gamma source CT unit 100 receives the projected image of the projected subject by one detector. The multiple gamma source CT portion 100 includes a gamma source 110, a shielding metal 120, a gantry 130, and a detector 140.

The gamma-ray source 110 projects the inspected object 10 with a radioactive material that is sealed with a radioactive isotope such as iridium (Ir-192) in a metal cap. Here, the gamma ray emitted from the gamma-ray source 110 may be an amount of the exposed radioactive amount that does not cause damage to the inspected object 10. In particular, the gamma source 110 is shielded by a pinhole collimator (not shown) to emit gamma rays only to the focal size of the X-ray tube that was previously used as a source. The pinhole collimator may be formed of a material having a high density and a sufficient thickness so that the intensity of the radiation emitted from the radioisotope, such as a gamma ray vessel, can be sufficiently reduced to be safely handled.

The gamma ray source 110 includes the same first gamma ray source 111, second gamma ray source 112, third gamma ray source 113, fourth gamma ray source 114 and fifth gamma ray source 115. At this time, the first to fourth gamma ray sources 111, 112, 113, and 114 may be spaced apart by a predetermined interval, and the interval may be adjustable according to user input. 1, the number of the gamma-ray sources is limited by the first to fourth gamma-ray sources 111, 112, 113, and 114. However, the present invention is not limited thereto. Accordingly, the number of gamma rays can be adjusted in consideration of the purpose of the operation, the external environment, the state of the subject, and the like.

Shielding metal 120 shields all gamma rays emitted from gamma source 110. In particular, when imaging is not performed, the shielding metal 120 can control the shielding against radiation that is always emitted from the gamma-ray source 110. For this purpose, the shielding metal 120 is formed at one end of the pinhole collimator. The shielding metal 120 is configured to correspond to the first to fourth gamma sources 111, 112, 113, 114. That is, the shielding metal 120 includes a first shielding metal 121 formed at one end of the first gamma-ray source 111, a second shielding metal 122 formed at one end of the second gamma-ray source 112, a third gamma- Shielding metal 123 formed on one end of the fourth gamma-ray source 114 and a fourth shielding metal 124 formed on one end of the fourth gamma-ray source 114. The one end may be one end of the direction in which the radiation is emitted from each gamma source 110.

Here, the shielding metal 120 can be automatically operated at a long distance, thereby preventing a risk that the user is exposed to radiation.

The gantry 130 is a cylindrical structure formed in the gamma-ray source 110 and the shielding metal 120. The gantry 130 can rotate clockwise or counterclockwise. Thus, the gantry 130 allows gamma rays emitted from the gamma source 110 to project the object in various directions. At this time, the subject 10 is placed in the cylindrical shape of the gantry 130 and projected onto the gamma ray.

The detector 140 receives the image transmitted through the gamma ray emitted from the gamma ray source 110. The detector 140 receives the projection images for the various angles projected from the plurality of gamma ray sources 110. The detector 140 overlays the projection image for the plurality of received gamma rays to detect one projection image. The multiple gamma source CT unit 100 opens all of the shielding metals 120 and emits gamma rays of a plurality of gamma ray sources 110 at the same time to detect a projection image for all angles with one detector 140, May be opened one by one to emit a gamma ray for each gamma ray source 110 to detect a projection image for all angles with one detector 140.

Here, the detector 140 can detect a projection image for the case where the inspected object 10 is present or not.

The controller 200 estimates a projection image of each gamma source 110 based on one projection image detected by the detector 140 and applies an iterative reconstruction algorithm to the estimated projection image. The control unit 200 generates one reconstructed three-dimensional image using the plurality of reconstructed projected images.

In detail, the controller 200 separates the projection image detected by the detector 140 into a projection image for the radiation emitted from each gamma source 110. Accordingly, the number of the separated projection images is equal to the number of the gamma-ray sources 110.

The control unit 200 generates an initial reconstructed image (

Figure 112015078687938-pat00001
) Can be initialized to a predetermined value. Preferably, the controller 200 can initialize to 0.05.

The control unit 200 displays the projection image of the empty space in the state in which the inspected object 10 is not present

Figure 112015078687938-pat00002
) And an initial reconstructed image,
Figure 112015078687938-pat00003
). Here, the projected image of the empty space includes the gamma-ray source 110 structure information of the multiple gamma source CT unit 100.

The control unit 200 receives the projection image of the subject 10

Figure 112015078687938-pat00004
) And the virtual projection image to estimate and separate the projection image of the corresponding subject 10 for each of the gamma-ray sources 110. The control unit 200 can estimate and separate the projection image of the subject 10 using Equation (1).

Figure 112015078687938-pat00005

here,

Figure 112015078687938-pat00006
Denotes an estimated projection image of the i-th gamma-ray source,
Figure 112015078687938-pat00007
Means a projection image of a subject,
Figure 112015078687938-pat00008
Denotes a virtual projection image of the i-th gamma ray source.

The control unit 200 log-converts the projection image of the separated body. The log transformation is a transformation of the projection image of the subject into a form that can be applied to the reconstruction algorithm. The control unit 200 can perform logarithmic conversion using Equation (2).

Figure 112015078687938-pat00009

here,

Figure 112015078687938-pat00010
Is the logarithmically transformed estimated projection image of the i-th gamma-ray source,
Figure 112015078687938-pat00011
Denotes a projection image for an empty space of the i-th gamma ray source,
Figure 112015078687938-pat00012
Is the estimated projection image of the i-th gamma-ray source.

The control unit 200 generates a reconstructed image based on the system matrix of each gamma ray source. The reconstructed image may be a 3D image. The controller 200 applies a reconstruction algorithm to the logarithm-transformed projected image, and then generates a reconstructed image by matching the plurality of applied projection images.

The controller 200 can apply the reconstruction algorithm to the Adaptive Steepest Descent-Projection Onto Convex Sets (ASD-POCS) algorithm and the TV Minimization (Total Variation Minimization) algorithm. At this time, the TV minimization algorithm may be included in the ASD-POCS algorithm. The ASD-POCS algorithm is an algorithm for reconstructing a three-dimensional reconstructed image by reconstructing a separate projection image, and the TV minimization algorithm is an algorithm for minimizing a total change in a 3D reconstructed image.

The controller 200 filters the estimated projection image using Equation (3), and reconstructs the data of the filtered projection image.

Figure 112015078687938-pat00013

here,

Figure 112015078687938-pat00014
Is a vector of the reconstructed image,
Figure 112015078687938-pat00015
Means the TV norm. In particular, Equation (3) must satisfy the following condition.

[Conditional expression]

Figure 112015078687938-pat00016
,
Figure 112015078687938-pat00017
,
Figure 112015078687938-pat00018

here,

Figure 112015078687938-pat00019
Denotes a system matrix,
Figure 112015078687938-pat00020
Is a logarithmically transformed projected image,
Figure 112015078687938-pat00021
Is a projected image of log-transformed reconstructed image,
Figure 112015078687938-pat00022
Means a reconstructed image.

The control unit 200 can repeatedly perform image reconstruction by generating a virtual projection image, estimating a projection image, and applying a reconstruction algorithm using the generated reconstruction image. Thus, the quality of the reconstructed image can be improved. At this time, the repetitive execution is performed at least 100 times, preferably 150 times.

If the number of times of repetition is less than 100, the resolution of the reconstructed image becomes lower and it becomes difficult to check the image. If the number of iterations is 150 or more, the resolution of the reconstructed image is improved, but the time and cost are consumed.

In particular, the controller 200 updates the reconstructed reconstructed image to the reconstructed reconstructed image, and then proceeds to repeat the reconstructed reconstructed image.

The output unit 300 outputs the projection image detected by the multiple gamma source CT unit 100 and the image reconstructed by the control unit 200. The output unit 300 may output the reconstructed image repeatedly performed in accordance with the preset setting or may output the reconstructed reconstructed image finally.

The output unit 300 may be a liquid crystal display (LCD), a thin film transistor-liquid crystal display (TFT LCD), an organic light-emitting diode (OLED), a flexible display display, a monitor, a projector, and a printer.

The storage unit 400 stores the projection image detected by the multiple gamma source CT unit 100, and the reconstructed image is stored in the control unit 200.

The storage unit 400 may be a storage medium such as a memory. The storage unit 400 may be a flash memory type, a hard disk type, a multimedia card micro type, a card type memory (for example, SD or XD memory) (Random Access Memory), a static random access memory (SRAM), a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), a programmable read-only memory (PROM) A magnetic disk, and / or an optical disk.

FIG. 2 is an exemplary diagram for explaining a projection image estimation according to an exemplary embodiment of the present invention. Referring to FIG. FIG. 2 (a) is a view showing that a subject is projected from two identical gamma-ray sources and detected as one projected image, and FIG. 2 (b) is a view showing a projected image of two identical gamma- And the projection image is divided into the respective projection images.

Referring to FIG. 2, the controller 200 separates the projection image received from the detector 140 into a projection image projected from each gamma ray source 110. The received projection image is an image in which a gamma ray emitted from two gamma-ray sources 111 and 115 is projected on a projection image of the subject 10.

Accordingly, the controller 200 estimates one overlaid projection image and separates the overlaid projection image into the projection images corresponding to the gamma-ray sources 111 and 115. The controller 200 separates the images projected from the gamma-ray sources 111 and 115 using Equation (1). At this time, the control unit 200 separates the projection image based on the information according to the angle at which the gamma ray source is located.

2B is a projection image in which the subject 10 is projected by the gamma rays emitted from the fifth gamma ray source 115 and the lower projection image is gamma rays emitted from the first gamma source 111, And the projected image is a projected image of the subject 10.

The right part of the projection image of the subject 10 to the fifth gamma ray source 115 is an image of the empty space in which the subject 10 is not projected. That is, the right portion corresponds to a portion of the gamma ray emitted as the fifth gamma ray source 115 is located on the right side of the subject 10, and is directly received by the detector 140 without being able to project the subject 10.

The left portion of the projection image of the subject 10 with respect to the first gamma-ray source 111 is an image of the empty space in which the subject 10 is not projected. That is, the left part corresponds to a part detected by the detector 140 without being able to project the subject 10 out of the gamma rays emitted as the first gamma-ray source 111 is positioned to the left of the subject 10.

FIGS. 3A through 3E are diagrams for explaining a procedure of reconstructing multiple gamma source CT images according to an exemplary embodiment of the present invention.

Referring to FIGS. 3A to 3E, the controller 200 reconstructs the projection image of the subject 10 through repetitive filtering.

The controller 200 initializes the initial reconstructed image to a specific constant of 0.05 at the first performing step where the initial reconstructed image is unknown. Then, the controller 200 generates a virtual projection image for the projection image of the subject using the position information of the gamma source 110 and the detector 140, that is, the scan structure information (FIG.

The controller 200 estimates the projection image using the generated virtual projection image. The controller 200 separates the projection image into the projection image estimated from each gamma source 110 through the projection image estimation (FIG. 3B).

The control unit 200 reconstructs the image using the system matrix having the position information of each gamma ray source of the estimated projection image and the ASD-POCS reconstruction algorithm (FIG. 3C). The control unit 200 reconstructs the image by applying the TV minimization algorithm (FIG. 3D).

The controller 200 updates the corrected reconstructed image to the initial reconstructed image, and then repeatedly performs the projection image estimation and the two algorithms to improve the image quality (FIG. 3E). At this time, the controller 200 may perform the repetition more than 150 times.

(Experimental Example: Gamma-ray  Depending on location Reconstruction video )

FIG. 4 is a view for explaining a reconstruction image for a gamma ray source position of a multiple gamma source CT image reconstructing apparatus according to an embodiment of the present invention, FIG. 5 is a view for reconstructing multiple gamma source CT images reconstructed according to an embodiment of the present invention FIG. 8 is an exemplary diagram for explaining a projection image estimation for a gamma ray source position of the apparatus.

Referring to FIGS. 4 and 5, the multiple gamma source CT image reconstructing apparatus 1 can project the subject 10 by adjusting the interval of the gamma source 110.

FIG. 4 is a reconstruction image of two identical gamma-ray sources 111 and 115 obtained by repeating the algorithm about 300 times. 4 (a) is a reference image. FIG. 4 (b) shows a case where the angles of two gamma ray sources differ by 1 °, FIG. 4 (c) FIG. 4 (e) is a reconstruction image when the angles of the two gamma sources are 20 ° apart, when the angles of the two gamma sources are 10 ° apart.

4 (b) to 4 (e), it can be seen that the smaller the angle formed by the two gamma ray sources 111 and 115 is, the clearer the reconstructed image appears.

Particularly, FIG. 5 (a) is a virtual transmission image when the angles of two gamma ray sources are different by 10 degrees, and FIG. 5 (b) is a virtual transmission image when the positions of two gamma ray sources are different by 20 degrees. Analysis of FIGS. 4 (d) and 4 (e) based on this result shows that as the angle formed by the two gamma ray sources 111 and 115 is smaller, the number of overlapped portions increases, so that the quality of the reconstructed image can be improved.

(First embodiment: multiple gamma source CT image reconstruction method)

6 is a flowchart illustrating a method for reconstructing multiple gamma source CT images according to an embodiment of the present invention.

Referring to FIG. 6, the method of reconstructing multiple gamma source CT images can fundamentally reduce beam curing, which is a main cause of degradation of reconstructed image quality in a conventional CT imaging apparatus. Multiple gamma source CT reconstruction methods are capable of reconstructing quantitative CT images with only one scan by using a source of monochromatic energy, thereby improving the lesion detection rate of reconstructed images by increasing the contrast between lesions and soft tissues.

The multiple gamma source CT image reconstructing apparatus 1 obtains a projection image of a hollow space projected from a plurality of identical gamma ray sources (S100). The multiple gamma source CT image reconstructing apparatus 1 irradiates a gamma ray to a vacant space according to a preset sequence of one gamma ray source to detect a projected image of an empty space. Here, the multiple gamma source CT image reconstructing apparatus 1 may detect a projection image of an empty space to confirm the position information of the gamma-ray source 110 and the detector 140.

The multiple gamma source CT image reconstructing apparatus 1 detects and obtains a projected image of a subject projected from a plurality of same gamma ray sources (S110). The multiple gamma source CT image reconstructing apparatus 1 simultaneously irradiates the subject 10 with a gamma ray to detect a projected image of the subject 10.

At this time, in steps S100 and S110, a plurality of gamma ray sources are spaced apart at predetermined intervals, and gamma rays are emitted from the separated gamma ray sources at a predetermined angle. Also, the emitted gamma rays simultaneously project the empty space or the inspected object 10 and project the projected image to the single detector 140.

The multiple gamma source CT image reconstructing apparatus 1 estimates a projection image obtained from each gamma ray source (S120). The multiple gamma source CT image reconstructing apparatus 1 separates the estimated projection images from each gamma ray source.

The multiple gamma source CT image reconstructing apparatus 1 generates a reconstructed image (S130). The multiple gamma source CT image reconstructing apparatus 1 applies a plurality of projection images estimated by each gamma ray source to a reconstruction algorithm, reconstructs the reconstructed image, and generates a corrected reconstruction image.

7 is a flowchart illustrating a method of estimating a projection image according to an embodiment of the present invention.

Referring to FIG. 7, the projection image estimation method performs the following steps.

The multiple gamma source CT image reconstructing apparatus 1 initializes the reconstructed reconstructed image (S200). The multiple gamma source CT image reconstructing apparatus 1 sets an initial value of a reconstructed basic image necessary for projection image estimation. At this time, the initial value may be 0.05.

The multiple gamma source CT image reconstructing apparatus 1 generates a virtual projection image (S210). The multiple gamma source CT image reconstructing apparatus 1 generates a virtual projection image using information that is a structure of a plurality of gamma ray sources 110 included in a projection image of an empty space and a set basic reconstruction image.

The multiple gamma source CT image reconstructing apparatus 1 estimates a projected image of the subject (S220). The multiple gamma source CT image reconstructing apparatus 1 estimates and separates a projected image irradiated by gamma rays emitted from each gamma ray source 110 using the generated virtual projection image. The multiple gamma source CT image reconstructing apparatus 1 can estimate the projection image of the subject using Equation (1).

The multiple gamma source CT image reconstructing apparatus 1 log-transforms the separated projection images (S230). The multiple gamma source CT image reconstructing apparatus 1 logarithmically transforms a projected image of a subject 10 separated by using a projection image of an empty space. The log transformation is performed to apply the reconstruction algorithm to be performed later.

FIG. 8 is a flowchart illustrating a video reconstruction method according to an embodiment of the present invention.

Referring to FIG. 8, the image reconstruction method performs the following steps.

The multiple gamma source CT image reconstructing apparatus 1 applies the ASD-POCS reconstruction algorithm according to the scanning condition of each gamma ray source 110 (S310). The multiple gamma source CT image reconstructing apparatus 1 applies a TV minimization algorithm (S320). Here, the ASD-POCS reconstruction algorithm can include a TV minimization algorithm and can be performed simultaneously.

The multiple gamma source CT image reconstructing apparatus 1 reconstructs a projection image of a separated body using the system matrix of each gamma ray source, and then generates a corrected reconstruction image. At this time, the generated one reconstructed reconstructed image may be an overlaid image of a plurality of reconstructed projected images. The multiple gamma source CT image reconstructing apparatus 1 can reconstruct the data of the projection image using Equation (2).

(Second Embodiment: Multiple Gamma Source CT Image Reconstruction Method)

9 is a flowchart illustrating a method for reconstructing multiple gamma source CT images according to another embodiment of the present invention.

Referring to FIG. 9, the multiple gamma source CT image reconstruction method can improve the quality of the reconstructed image by reconstructing the projection image repeatedly.

The multiple gamma source CT image reconstructing apparatus 1 is obtained by detecting a projected image of a blank space projected from a plurality of identical gamma ray sources (S400). The multiple gamma source CT image reconstructing apparatus 1 irradiates a gamma ray to a vacant space according to a preset sequence of one gamma ray source to detect a projected image of an empty space. Here, the multiple gamma source CT image reconstructing apparatus 1 may detect a projection image of an empty space to confirm the position information of the gamma-ray source 110 and the detector 140.

The multiple gamma source CT image reconstructing apparatus 1 detects and obtains a projected image of a subject projected from a plurality of identical gamma ray sources (S410). The multiple gamma source CT image reconstructing apparatus 1 simultaneously irradiates the subject 10 with a gamma ray to detect a projected image of the subject 10.

At this time, in steps S400 and S410, the plurality of gamma ray sources are spaced apart at predetermined intervals, and gamma rays are emitted from the separated gamma ray sources at a predetermined angle. Also, the emitted gamma rays simultaneously project the empty space or the inspected object 10 and project the projected image to the single detector 140.

The multiple gamma source CT image reconstructing apparatus 1 estimates a projection image obtained from each gamma ray source (S420). The multiple gamma source CT image reconstructing apparatus 1 separates the estimated projection images from each gamma ray source.

In detail, the multiple gamma source CT image reconstructing apparatus 1 sets up the basic reconstruction image necessary for projection image estimation. Here, the basic reconstruction image can be set to 0.05.

The multiple gamma source CT image reconstructing apparatus 1 generates a virtual projection image using structure information of a plurality of gamma-ray sources 110 included in a projection image of an empty space and the basic reconstruction image.

The multiple gamma source CT image reconstructing apparatus 1 estimates and separates a projected image irradiated by the gamma rays emitted from each gamma ray source 110 using the generated virtual projection image and the projection image of the inspected object 10. The multiple gamma source CT image reconstructing apparatus 1 can estimate the projection image of the subject using Equation (1).

The multiple gamma source CT image reconstructing apparatus 1 logarithmically transforms a projected image of a subject 10 separated by using a projection image of an empty space. The log transformation is performed to apply the reconstruction algorithm to be performed later.

The multiple gamma source CT image reconstructing apparatus 1 generates a reconstructed image (S430). The multiple gamma source CT image reconstructing apparatus 1 applies a plurality of projection images estimated by each gamma ray source to a reconstruction algorithm, reconstructs the reconstructed image, and generates a corrected reconstruction image.

The multiple gamma source CT image reconstructing apparatus 1 determines whether the image has been reconstructed a predetermined number of times (S440). The multiple gamma source CT image reconstructing apparatus 1 confirms the number of times the projection image is reconstructed and then finishes reconstructing the image if the number of reconstructed images is equal to or greater than a preset number, and performs step S420 if the reconstructed image is less than the preset number of times. Here, the preset number of times is 100 to 200, preferably 150.

At this time, the basic reconstruction image necessary for the projection image estimation is updated to the corrected reconstruction image, and then the step S420 is performed.

The present invention can also be embodied as computer-readable codes on a computer-readable recording medium. A computer-readable recording medium includes all kinds of recording apparatuses in which data that can be read by a computer apparatus is stored. Examples of the computer-readable recording medium include a hard disk, a ROM, a RAM, a CD-ROM, a hard disk, a magnetic tape, a floppy disk, an optical data storage device, and the like.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation in the embodiment in which said invention is directed. It will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the scope of the appended claims.

1: multiple gamma source CT reconstruction device
10:
100: multiple gamma source CT section
110: gamma ray
111: 1st gamma ray source
112: second gamma ray
113: Third gamma ray
114: fourth gamma ray source
115: 5th gamma ray
120: shielding metal
121: first shielding metal
122: Second shielding metal
123: Third shielding metal
124: fourth shielding metal
125: Fifth shielding metal
130: Gentry
140: detector
200:
300:
400:

Claims (10)

A method for reconstructing multiple gamma source CT images performed on a multiple gamma source CT image reconstructing apparatus including a multiple gamma source computerized tomography unit receiving a gamma ray projected image of a subject and a control unit,
Wherein the multiple gamma source computer tomography unit irradiates a gamma ray to an empty space according to a predetermined sequence of gamma ray sources of one of a plurality of same gamma ray sources to obtain a projected image of an empty space;
The multiple gamma source computerized tomography unit irradiating gamma rays emitted from a plurality of same gamma ray sources simultaneously to a subject to obtain a projected image of the subject;
Estimating a projection image of the subject for each gamma ray source using the projection image of the obtained empty space, the projection image of the subject, and the basic reconstruction image; And
And the controller reconstructs the estimated projection image of the subject to generate a corrected reconstruction image.
The method according to claim 1,
Obtaining a projection image by irradiating the void space and irradiating the inspected object to obtain a projection image,
Wherein the plurality of gamma-ray sources are spaced apart at predetermined intervals, and gamma rays emitted from the separated gamma-ray sources are detected by one detector.
The method according to claim 1,
Wherein the step of estimating the projection image of the subject comprises:
Setting the basically reconstructed image to a predetermined value;
Generating a virtual projection image of the subject using the set basic reconstruction image and the projection image of the empty space;
Estimating and separating a projection image of a subject corresponding to each of the gamma-ray sources using the projection image of the subject and the generated virtual projection image; And
Further comprising the step of logarithmically transforming the projection image of the subject separated using the projection image of the empty space.
The method of claim 3,
Wherein the step of estimating and separating the projection image of the subject comprises:
A method of reconstructing multiple gamma source CT images, comprising: estimating and separating a projection image of the subject using the following equation:
[Mathematical Expression]
Figure 112015078687938-pat00023

here,
Figure 112015078687938-pat00024
Denotes an estimated projection image of the i-th gamma-ray source,
Figure 112015078687938-pat00025
Means a projection image of a subject,
Figure 112015078687938-pat00026
Denotes a virtual projection image of the i-th gamma ray source.
The method according to claim 1,
Wherein the generating the reconstructed image comprises:
Reconstructing the estimated projection image using the following equation: < EMI ID =
[Mathematical Expression]
Figure 112015078687938-pat00027
,
Figure 112015078687938-pat00028
,
Figure 112015078687938-pat00029
,
Figure 112015078687938-pat00030

here,
Figure 112015078687938-pat00031
Is a vector of the reconstructed image,
Figure 112015078687938-pat00032
Means the TV norm,
Figure 112015078687938-pat00033
Denotes a system matrix,
Figure 112015078687938-pat00034
Is log-transformed and estimated projection image data,
Figure 112015078687938-pat00035
Is the projection image data of the log-transformed reconstructed image,
Figure 112015078687938-pat00036
Means a reconstructed image.
The method according to claim 1,
Estimating a projection image of the subject and generating the reconstructed image,
Wherein the reconstructed reconstructed image is reconstructed after updating the reconstructed reconstructed image.
delete A computer-readable recording medium storing a program for causing a computer to execute the method according to any one of claims 1 to 6.
delete delete
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KR101146833B1 (en) 2011-12-09 2012-05-21 전남대학교산학협력단 The non-rotation ct system
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