Abstract:
A system for processing three dimensional (3D) distribution image of a radiation source and a processing method using the same are provided. The system includes an image measuring unit comprising a plurality of position sensitive detectors to measure the radiation source, a signal amplifying unit which receives signals from the image measuring unit and amplifies the received signals into an electric signal, a mode selecting unit that receives the electric signal and selects a detection mode and outputs a corresponding mode signal, a data storage unit which stores the signals as a series of items, a data converting unit which converts the data stored at the data storage unit into interactive data, an image reconstructing unit which reconstructs the converted data into the 3D distribution image, and a display unit which displays the 3D distribution image received from the reconstructing unit.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This patent application claims the benefit of priority from Korean Patent Application No. 10-2010-0138959, filed on Dec. 30, 2010, the contents of which are incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a radiological imaging apparatus, and more particularly, to a method for processing 3-dimensional (3D) distribution image of radiation source to acquire 3D distribution of radiological image with improved sensitivity and image resolution, and a system using the same. 
     2. Description of the Related Art 
     The invention relates to a position sensitive detector-based imaging apparatus which acquires a three dimensional (3D) distribution image of a radiation source existing within a living organism. The single-photon emission computed tomography (SPECT) and positron emission tomography (PET) are the two representative examples of a conventional radiological imaging apparatus. SPECT uses a mechanical collimator which is made from materials such as lead or tungsten to acquire image from the radiation source. 
     However, the gamma ray sensitivity and the image resolution are in inverse relationship with each other, according to the aperture size of the collimator. 
     That is, if the sensitivity increases, the resolution degrades, and if the resolution improves, then the sensitivity decreases. There also is a drawback related to the use of mechanical collimator. That is, SPECT imaging equipment has increased size to accommodate the mechanical collimator, and has to be rotated to acquire 3D image. 
     PET concurrently receives 511 keV gamma rays emanating from the radiation source to acquire images of the radiation source distributed within the matter. Unlike SPECT, PET does not have to be rotated due to the circular arrangement of detectors. However, since PET uses higher magnitude of gamma ray energy than SPECT, PET has more Compton scattering due to photoelectric effect of the gamma rays at the detectors, rather than the entire energy is absorbed. 
     Due to the multi-scattering of gamma rays inside the respective detectors, the gamma rays are measured concurrently through a plurality of channels. Since the radiation source is not always present at the center of the imaging apparatus, the gamma rays can enter the apparatus through not only the surface of incidence, but also the side of the apparatus. 
     However, the above causes inaccuracy of position measurement. Such event works as a background event that obscures the image of the imaging apparatus such as PET. Due to the above-mentioned limits, the conventional imaging apparatus including PET has image resolution which is limited within a range of several mm at the maximum. 
     SUMMARY OF THE INVENTION 
     Exemplary embodiments of the present inventive concept overcome the above disadvantages and other disadvantages not described above. Also, the present inventive concept is not required to overcome the disadvantages described above, and an exemplary embodiment of the present inventive concept may not overcome any of the problems described above. 
     An object of the present invention is to provide a method for processing a three-dimensional (3D) distribution image of a radiation source and a system using the same, which are capable of resolving limited sensitivity and image resolution which are generated due to structural limits of a conventional radiological imaging apparatus, by utilizing all the methods that involve interaction between gamma rays and detectors. 
     In one embodiment, a system for processing three dimensional (3D) distribution image of a radiation source may be provided, which may include an image measuring unit which comprises a plurality of position sensitive detectors to measure the radiation source, the plurality of position sensitive detectors each having a devoted channel set therefore, and being arranged in a circularly fashion around the radiation source, a signal amplifying unit which receives signals indicative of energy magnitude and location of the radiation source from the image measuring unit and amplifies the received signals into an electric signal, a mode selecting unit which receives the electric signal generated at the signal amplifying unit, and selects a detection mode according to the energy magnitude and the location and outputs a corresponding mode signal, a data storage unit which stores the signals indicative of the energy magnitude, time of radiation generation, and location of the radiation source, and the signal received from the mode selecting unit as a series of items, a data converting unit which converts the data stored at the data storage unit into interactive data, an image reconstructing unit which reconstructs the converted data into the 3D distribution image, and a display unit which displays the 3D distribution image received from the reconstructing unit. 
     The image measuring unit may include the plurality of position sensitive detectors in N×M size (N, M=natural number), and the plurality of position sensitive detectors each detect the location of the radiation source, travel time and energy magnitude of the radiation through channels different from each other. 
     The plurality of position sensitive detectors each comprise a plurality of signal electrodes of a predetermined shape with width (k) and height (k). 
     The mode selecting unit categorizes the electric signal received along the respective channels to under coincidence mode. 
     The mode selecting unit categorizes the electric signal received along the respective channels to under single tracking mode of dual gamma ray. 
     The mode selecting unit categorizes the electric signal received along the respective channels to under coincidence mode/gamma ray tracking mode. 
     The mode selecting unit categorizes the electric signal received along the respective channels to under coincidence dual gamma ray tracking mode. 
     The mode selecting unit implements the coincidence mode, single tracking mode of dual gamma rays, coincidence mode/gamma ray tracking mode, and coincidence dual gamma ray tracking mode, depending on the electric signal received through the respective channels. 
     In one embodiment, a system for processing three dimensional (3D) distribution image of a radiation source may be provided, which may include an image measuring unit which comprises a plurality of position sensitive detectors to measure the radiation source, the plurality of position sensitive detectors each having a devoted channel set therefore, and being arranged in a circularly fashion around the radiation source, a signal amplifying unit which receives signals indicative of energy magnitude and location of the radiation source from the image measuring unit and amplifies the received signals into an electric signal, a mode selecting unit which receives the electric signal generated at the signal amplifying unit, and categorizes coincidence mode, single tracking mode of dual gamma ray, coincidence mode/gamma ray tracking mode, and coincidence dual gamma ray tracking mode according to the energy magnitude and the location and outputs a corresponding mode signal, a data storage unit which stores the signals indicative of the energy magnitude, time of radiation generation, and location of the radiation source, and the signal received from the mode selecting unit as a series of items, a data converting unit which converts the data stored at the data storage unit into interactive data, an image reconstructing unit which reconstructs the converted data into the 3D distribution image, and a display unit which displays the 3D distribution image received from the reconstructing unit. 
     In one embodiment, a method for processing a three dimensional (3D) distribution image may be provided, which may include preparing a plurality of position sensitive detectors to measure a radiation source, setting dedicated channels for the position sensitive detectors respectively, and measuring a gamma ray at an image measuring unit in which the plurality of position sensitive detectors is arranged in a circular fashion around the radiation source (step 1), receiving signals, indicative of an energy magnitude, travel time, and location of the radiation source where the radiation is generated, from the image measuring unit and amplifying the received signals at a signal amplifying unit (step 2), storing image data, amplified at the signal amplifying unit, at a data storage unit as a series of items (step 3), converting the image data into interactive data at a data converting unit, using the signals received from the signal amplifying unit (step 4), reconstructing the converted data at an image reconstructing unit into the 3D distribution image (step 5), and displaying the 3D distribution image received from the image reconstructing unit through a display unit (step 6). 
     According to an embodiment of the present invention, background events that deteriorate detection efficiency and image resolution are efficiently reduced, so that a 3D distribution image of radiation source can be acquired with improved image resolution. Additionally, since detection efficiency increases, patients or living organisms can have inspection within a shortened period of measuring time. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and/or other aspects of what is described herein will be more apparent by describing certain exemplary embodiments with reference to the accompanying drawings, in which: 
         FIG. 1  is a block diagram of a system for processing a three-dimensional (3D) distribution image of a radiation source, according to an embodiment; 
         FIG. 2  is a view illustrating in detail the image measuring unit of  FIG. 1 ; 
         FIGS. 3A to 3D  are views illustrating the detection mode implementable at the image measuring unit of  FIG. 1 , in which  FIG. 3A  illustrates coincidence mode,  FIG. 3B  illustrates single tracking mode of dual gamma rays,  FIG. 3C  illustrates coincidence mode/gamma ray tracking mode, and  FIG. 3D  illustrates coincidence tracking mode of dual gamma ray; and 
         FIG. 4  is a flowchart provided to explain a method for processing a 3D distribution image of radiation source, according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Features and advantages of the present invention will be more clearly understood by the following detailed description of the present preferred embodiments by reference to the accompanying drawings. It is first noted that terms or words used herein should be construed as meanings or concepts corresponding with the technical spirit of the present invention, based on the principle that the inventors can appropriately define the concepts of the terms to best describe their own invention. Also, it should be understood that detailed descriptions of well-known functions and structures related to the present invention will be omitted so as not to unnecessarily obscure the important point of the present invention. 
     Throughout the disclosure, the expression that a specific element “comprises” a specific constituent intends to mean that the specific element includes the specific constituent and others, and does not confer the meaning that the specific element exclusively includes the specific constituent. Further, the term “unit” or “portion” used throughout the disclosure corresponds to a unit that can process at least one function or operation, and that can be implemented as hardware, software, or a combination of hardware and software. 
     The present invention will now be described in further detail by examples. It would be obvious to those skilled in the art that these examples are intended to be more concretely illustrative and the scope of the present invention as set forth in the appended claims is not limited to or by the examples. 
       FIG. 1  is a block diagram of a system for processing a 3D distribution image of radiation source according to an embodiment. 
     Referring to  FIG. 1 , the system  100  for processing a 3D distribution image of radiation source according to an embodiment may include an image measuring unit  110 , a signal amplifying unit  120 , a data storage unit  130 , a mode selecting unit  125 , a data converting unit  140 , an image reconstructing unit  150  and a display unit  160 . 
     The image measuring unit  110  may include a plurality of position-sensitive detectors to measure the radiation source, in which devoted channels are set respectively. The plurality of position sensitive detectors is arranged in a circular fashion around the radiation source. 
     The signal amplifying unit  120  may receive from the image measuring unit  110  signals indicating a magnitude of energy of the radiation source, travel time, and a location of the radiation source where the radiation is generated, and amplify the received signals by converting the received signals into electric signals. 
     The mode selecting unit  125  may receive the electric signals generated at the signal amplifying unit  120 , and select one mode from among the detection modes including, for example, coincidence mode, single tracking mode of dual gamma rays, coincidence mode/gamma ray tracking mode, and coincidence tracking mode of dual gamma rays, depending on the size of the electric signals and location, and outputs a mode signal according to the selection. Herein, the mode selecting unit  125  may output a mode signal by incorporating two or more modes. 
     Referring to  FIG. 3A  illustrating the coincidence mode, positrons of positron emitting radionuclides are absorbed into the matter, generating a pair of 511 keV gamma rays so that the generated gamma rays are emitted concurrently to opposite directions to conserve kinetic energy. The emitted gamma rays reach a predetermined detecting unit in N×M size and generate signals. The measuring units on two opposite ends notify the arrival of signal, and the radiation source is present on a straight line that connects these two measuring units. Since a plurality of gamma-ray pairs are generated, the source may be determined by connecting the measuring units that generate signals concurrently in straight lines respectively. 
     Referring to  FIG. 3B  which illustrates the single tracking mode of dual gamma rays, since the generated radiation pairs have high magnitude of energy, these secondarily interact with electrons with Compton and photoelectric effects to generate radiation scattering. The possibility is high that one out of the concurrently-generated radiations is measured. Accordingly, by tracking a secondary location of electron due to one of two radiations, location of the radiation is identified. 
     Referring to  FIG. 3C  which illustrates the coincidence mode/gamma ray tracking mode, while the radiation source generates a pair of radiations, part of the radiation source may generate separate radiation. The separate radiation interacts secondarily with the matters at the measuring units with Compton and photoelectric effects to thus generate radiation scattering with electron. The location of the radiation source is identified by tracking the secondary location of the electron due to radiations. 
     Referring to  FIG. 3D  which illustrates coincidence tracking mode of dual gamma rays, the location of the radiation source is identified by concurrently tracking the secondary location due to the pair of concurrently-generated radiations. 
     The data storage unit  130  may receive signals, indicated of the energy magnitude of the radiation source and the location of the radiation source where the radiation is generated, from the signal amplifying unit  120 , and also receive a mode signal transmitted from the mode selecting unit  125 , and database and store the received signals as predetermined items. 
     The data converting unit  140  may convert the data stored in the data storage unit  130  into interactive data. 
     The image reconstructing unit  150  may reconstruct the interactive data into a 3D distribution image. 
     The display unit  160  may receive the 3D distribution image from the image reconstructing unit  150  and display the resultant image. 
       FIG. 2  is a view illustrating the image measuring unit of  FIG. 1  according to an embodiment. 
     Referring to  FIG. 2 , the image measuring unit  110  may include the plurality of position sensitive detectors  10  in N×M size (N, M=natural number). The position sensitive detectors  10  may respectively include different channels from each other and detect the location and energy magnitude of the radiation source (e.g., source of gamma ray, beta ray, or the like). 
     The position sensitive detectors  10  may each be formed in square shape (e.g., width, height=r o ), and include a plurality of signal electrodes (width, height=k). 
       FIGS. 3A to 3D  are views illustrating the detection mode implementable at the image measuring unit of  FIG. 1 , in which  FIG. 3A  illustrates coincidence mode,  FIG. 3B  illustrates single tracking mode of dual gamma rays,  FIG. 3C  illustrates coincidence mode/gamma ray tracking mode, and  FIG. 3D  illustrates coincidence tracking mode of dual gamma rays. 
       FIG. 3A  illustrates the coincidence mode, in which positrons of positron emitting radionuclides are absorbed into the matter, generating a pair of 511 keV gamma rays so that the generated gamma rays are emitted concurrently to opposite directions to conserve kinetic energy. 
     The emitted gamma rays reach a predetermined detecting unit in N×M size (e.g., position sensitive detectors) and generate signals. The measuring units (e.g., position sensitive detectors) on two opposite ends notify the arrival of signal, and the radiation source is present on a straight line that connects these two measuring units. 
     Since a plurality of gamma-ray pairs are generated, the source may be determined by connecting the measuring units that generate signals concurrently in straight lines respectively. 
       FIG. 3B  illustrates the single tracking mode of dual gamma rays. Since the generated radiation pairs have high magnitude of energy, these secondarily interact with electrons with Compton and photoelectric effects to generate radiation scattering. 
     The possibility is high that one out of the concurrently-generated radiations is measured. Accordingly, by tracking a secondary location of electron due to one of two radiations, location of the radiation is identified. 
       FIG. 3C  illustrates the coincidence mode/gamma ray tracking mode. While the radiation source generates a pair of radiations, part of the radiation source may generate separate radiation. 
     The separate radiation interacts secondarily with the matters at the measuring units with Compton and photoelectric effects to thus generate radiation scattering with electron. The location of the radiation source is identified by tracking the secondary location of the electron due to radiations. 
       FIG. 3D  illustrates coincidence tracking of dual gamma rays, in which the location of the radiation source is identified by concurrently tracking the secondary location due to the pair of concurrently-generated radiations. 
       FIG. 4  is a flowchart provided to explain a method for processing 3D distribution image of radiation source according to an embodiment. 
     Referring to  FIG. 4 , the method for processing 3D distribution image of radiation source may include the following steps (S 10  to S 60 ). 
     In the first step (S 10 ), a plurality of position sensitive detectors is provided to measure the radiation source, devoted channels are set for the respective detectors, and the image measuring unit  110 , in which the plurality of position sensitive detectors is arranged in a circular fashion, measures the radiation source. 
     In the second step (S 20 ), signals, indicative of the energy magnitude and location of the radiation source where the radiation is generated, are received and amplified at the signal amplifying unit  120 . 
     In the third step (S 30 ), the amplified image data from the signal amplifying unit  120  is stored at the data storage unit  130 . 
     In the fourth step (S 40 ), the image data is converted into interactive data at the data converting unit  140  using the signal received from the signal amplifying unit  120 . 
     In the fifth step (S 50 ), the converted data is reconstructed into 3D distribution image at the image reconstructing unit  150 . 
     In the sixth step (S 60 ), the 3D distribution image received from the image reconstructing unit  150  is displayed through the display unit  160 . 
     According to an embodiment of the present invention, background events that deteriorate sensitivity and image resolution are efficiently reduced, so that a 3D distribution image of radiation source can be acquired with improved image resolution. Additionally, since sensitivity increases, patients or living organisms can have diagnostic examination within a shortened period of time. 
     The foregoing exemplary embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of apparatuses. Also, the description of the exemplary embodiments of the present inventive concept is intended to be illustrative, and not to limit the scope of the claims, and many alternatives, modifications, and variations will be apparent to those skilled in the art.