Abstract:
The present invention relates to a scintillation detector, which is largely divided into a scintillator and a photomultiplier, as a constituent element of a medical diagnostic imaging equipment, a scintillator, and a medical diagnostic imaging equipment using the same, and more specifically, to a plastic scintillator, and a scintillation detector and a medical diagnostic imaging equipment using the same wherein a plastic scintillator is provided as a scintillator constituting a scintillation detector of a medical diagnostic imaging equipment instead of a known crystal scintillator, thereby allowing easy processing of a scintillator, improving detection due to various configurations and remarkably reducing processing costs.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of Korean Patent Application No. 10-2010-0008138, filed with the Korean Intellectual Property Office on Jan. 28, 2010, the disclosure of which is incorporated herein by reference in its entirety. 
       BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present invention relates to a scintillator of a scintillation detector that detects high energy particles and a method of binding a scintillator in medical diagnostic imaging equipment, more specifically to a scintillator that emits light by detecting high energy particles generated by an object examined by a common medical diagnostic imaging equipment and a scintillation detector and medical diagnostic imaging equipment using such a scintillator. 
         [0004]    2. Background Art 
         [0005]    Medical diagnostic imaging equipment commonly includes computed tomography (CT), magnetic resonance imaging (MRI) and the like. Such imaging technologies are increasingly used for a more accurate examination by spotting a region having growing tissues to identify a thrombus, a scar, dead cancer tissue and the like from living tissues. In the medical device industry, which has recently attracted more attention, the market size of the medical diagnostic imaging equipment has reached nearly 50% of the entire medical device markets. 
         [0006]    As every kind of diagnostic imaging equipment has been accomplishing faster diagnosing time, real-time diagnosis and multi-dimensional imaging (e.g., 3D imaging and 4D imaging), various diagnostic methods have been developed for application in the medical diagnostic imaging equipment. However, not only does it take a great length of time to perform diagnosis using the medical diagnostic imaging equipment (e.g., 12 hours for full-body CT, 24 hours for full-body MRI, and 1 hour for full-body PET), but the examination cost is too high for the general public to afford, restraining a wide use of the medical diagnostic imaging equipment. 
         [0007]    A cause of the above problems is the scintillator, which is an essential element that emits light by being in contact with high energy particles during an examination, and of which a crystal scintillator is commonly used. The crystal scintillator, which is expensive and processing of which is difficult and costly, is a main cause of raising the price of medical diagnostic imaging equipment and increasing the examination time due to its difficulty of constituting in a wide area. 
       SUMMARY 
       [0008]    To overcome the limitations of structural improvement for enhancement of detection efficiency due to processing difficulty and high material costs caused by using the conventional scintillator, the present invention provides a plastic scintillator and a scintillation detector and medical diagnostic equipment using the plastic scintillator that can shorten the examination time and lower the manufacturing cost dramatically by utilizing a scintillator having a same effect and using a more economical material. 
         [0009]    To achieve the above object, the present invention can use a plastic scintillator to maximally reduce a gap between scintillators by allowing the scintillators to have various cross-sectional shapes, constitute the scintillator by including optical fiber, which is an effective detecting material, to enhance detectability, and dramatically increase an area where the scintillator is constituted when utilized in a medical diagnostic imaging equipment. 
         [0010]    With the present invention, the cost of raw material becomes remarkably lower than the conventional scintillator, and it becomes much easier for processing, thereby allowing for more efficient configuration and processing for detection of a high energy particle. Ultimately, the detection area of the medical diagnostic imaging equipment can be dramatically larger to reduce the detection time, allowing for increased convenience for users and supply at lower costs. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  shows conventional medical diagnostic imaging equipment. 
           [0012]      FIG. 2  is a perspective view illustrating an embodiment of the present invention. 
           [0013]      FIG. 3  is a perspective view illustrating some embodiments of the present invention. 
           [0014]      FIG. 4  is a cross-sectional view illustrating an embodiment of the present invention. 
           [0015]      FIG. 5  is an exploded view illustrating an embodiment of the present invention. 
           [0016]      FIG. 6  is a perspective view illustrating some embodiments of the present invention. 
           [0017]      FIG. 7  shows a configuration of an embodiment of the present invention. 
           [0018]      FIG. 8  is a cross-sectional view illustrating an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    Hereinafter, some embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
         [0020]    Several kinds of medical diagnostic imaging equipment have been developed, for example, positron emission tomography (PET), single photon emission computed tomography (SPECT), computed tomography (CT), magnetic resonance imaging (MRI) and the like. These kids of medical diagnostic imaging equipment detects a high energy particle generated at a particular region with a scintillator (a crystal exhibiting scintillation when struck by a particle), amplifies the high energy particle through a photomultiplier, converts the high energy particle into, and images a photocurrent detection signal to display the particular region where a problem occurs. As described above in the background art, most of these kinds of medical diagnostic imaging equipment are very expensive and thus are hardly utilized in a popular fashion. One of the causes of this shortcoming is the costly scintillator. 
         [0021]    In the conventional medical diagnostic imaging equipment, a photomultiplier  100  has a scintillator (S) inserted therein. As illustrated in  FIG. 1 , a plurality of the scintillators (S) are inserted into the photomultiplier  100  to form a scintillation detector  200 , which is arranged on a main body of the medical diagnostic imaging equipment to surround a cross-section of an examined object. 
         [0022]    Used for the scintillator arranged in the scintillation detector is a crystal, but a highly pure crystal (BGO and various kinds of crystal) requires a long time of growth and is difficult to manufacture, making it costly to process and utilize the crystal for the scintillator of a medical diagnostic imaging equipment. 
         [0023]    In the present invention, the conventional crystal (such as BGO) is not utilized as the scintillator of the medical diagnostic imaging equipment, but as illustrated in  FIG. 2 , a plastic scintillator  10  and optical fiber  20  constituted therein are provided to have the same effectiveness as the conventional crystal but with a significant economical effect. 
         [0024]    By using the plastic scintillator  10  for the scintillator constituted in the scintillation detector, the performance and detecting effect of the scintillator in accordance with the present invention is unchanged from the conventional crystal scintillator, but is so easy to process that it can be fabricated in various shapes at incomparably low costs. 
         [0025]    It is so difficult and costly to process the conventional crystal scintillator that the scintillator is formed in the shape of a hexahedral cylinder, in which a cross-section on a side of detecting the high energy particle is close to a square, and bound with the photomultiplier. However, as illustrated in  FIG. 3 , with the plastic scintillator in accordance with an embodiment of the present invention, it is possible to form a cross-section on a side of detecting the high energy particle in the shapes of various polygons, such as a triangle, a rectangle, a pentagon, a hexagon, a heptagon, an octagon, etc. 
         [0026]    In the present invention, the effectiveness of detection can be enhanced by minimizing a gap among the scintillators, as the scintillation detector  200  is constituted with the photomultiplier  100  in which the plastic scintillator  10  in the shape of a hexagon is used. That is, as illustrated in  FIG. 4 , in the case that the scintillation detector  200  of medical diagnostic imaging equipment is constituted with the plastic scintillator  10  having a hexagonal cross-section, which is commonly referred to as a honeycomb structure, gaps that can occur among the scintillators  10  are relatively smaller than those of other cross-sectional shapes, making it possible to detect the high energy particles more efficiently. 
         [0027]    As illustrated in  FIGS. 2 ,  5 ,  6  and  7 , it is possible to process and constitute this kind of plastic scintillator  10  in a highly efficient form and thus to form a hollow section h. Although it is possible to bind the plastic scintillator  10  as is with the photomultiplier  100 , an integrated plastic scintillator  10 ′ can be constituted by forming a hollow section h inside a central part thereof and inserting the optical fiber  20  into the hollow section h in order to collect the light emitted from the plastic scintillator and transfer the light to the photomultiplier.  100 . In such a configuration, it is possible to allow the optical fiber  20  to penetrate through the plastic scintillator  10  or allow the optical fiber  20  to penetrate the scintillator  10  where the scintillator  10  makes contact with the photomultiplier  100  and penetrate the scintillator  10  or be formed not to be exposed to an outside on the side of detecting the high energy particle. Moreover, it is possible to form a plurality of hollow sections h and insert a plurality of optical fiber  20  accordingly, or use a fiber optic core selectively or clad an external part of the core (not shown). 
         [0028]    In constituting the scintillation detector  200  applied with the plastic scintillator  10  in which the optical fiber  20  is formed, one side of the optical fiber  20  can be directly connected with the photomultiplier  100  in order to enhance the effect of detection. It shall be appreciated that, in the case of a plastic scintillator  10  that does not include optical fiber  20 , its cross-section can be bound to the photomultiplier  100  in a conventional way. 
         [0029]    As illustrated in  FIG. 8 , the light can be better collected by forming a reflecting film on an external surface of the plastic scintillator  10 , in which case the reflecting film  30  can have a lower refractive index than a conventional plastic scintillator  10 . 
         [0030]    Although there can be various methods of forming a plastic scintillator, in an embodiment of the present invention, fluorescent additives, which can be classified into a primary fluorescent additive and a secondary fluorescent additive, can be used for the plastic scintillator  10 . Used as the primary fluorescent additive can be p-terphenyl (PT) or 2,5-dephenyloxazole (PPO). Used as the secondary fluorescent additive, i.e., a wavelength transfer agent, can be POPOP or 4-bis(2-Methylstyryl)benzene (bis-MSB). 
         [0031]    Used as the fluorescent additive for the optical fiber can be K27, BBQ(7H-benzimidazo[2,1-a]benz[de]isoquinoline-7-one) of National Diagnostics, or Lumogen of BASF. Accordingly, the fluorescent additive in the color of red, orange, yellow, green, blue, purple or pink can be added according to the usage of detection to use an entire wavelength between 200 nm and 900 nm, thereby allowing for use in the conventional photomultiplier tube (PMT), silicon photomultiplier (SIPM) or multi pixel photon counter (MPPC). 
         [0032]    Used for a material to clad the optical fiber can be poly methyl metha acrylate (PMMA), of which the refractive index is 1.59 and the density is 1.19, in the case that PS is used as a core of the optical fiber for primary cladding of the optical fiber. In addition, any material (e.g., PTFE or PEFE) having the refractive index that is smaller than that of PMMA can be used for secondary cladding over the primary cladding, or the secondary cladding can be optionally omitted. 
         [0033]    In the case that PMMA is used for the core of the optical fiber, it is preferable that PTFE or PEFE, of which the refractive index is smaller than that of PMMA, is used for the cladding. That is, it is preferable that aluminum or titanium dioxide (TiO 2 ) is used for the reflecting film located outside a scintillating cell,