Abstract:
A radiation diagnosis apparatus, which employs a reduced number of data acquisition units while showing the same effect as that of the related art (PET, SPECT or x-ray CT) includes: a first radiation detector; a second radiation detector an inverter formed at an output terminal of the first radiation detector; a discriminator for receiving a common signal from the first and second radiation detector and outputting a control signal corresponding to the input common signal; and a data acquisition unit and indentifying an output signal of which detector of the first and second detectors the input signal is according to a polarity difference of the input signal, to provide a radiation diagnosis apparatus which employs a reduced number of data acquisition units while showing the same effect as that of the related art.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2011-0117720 filed in the Korean Intellectual Property Office on Nov. 11, 2011, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     (a) Field of the Invention 
     The present invention relates to a radiation diagnosis apparatus. More particularly, the present invention relates to a radiation diagnosis apparatus including a plurality of radiation detectors for outputting signals of a single polarity. 
     (b) Description of the Related Art 
     In general, a radiation diagnosis apparatus employs a radiation detector for detecting a radiation. A radiation includes a gamma ray emitted when a radio isotope is changed while an atomic nucleus thereof remains stable, and an X-ray emitted when an electron collides with an object at a high speed. In this case, the radiation detector detects an emitted radiation. 
     A representative example of such a radiation diagnosis apparatus includes a positron emission tomography (PET) apparatus, a single photon emission computed tomography (SPECT) apparatus, an X-ray computed tomography (X-ray CT) apparatus, and the like. Of course, such radiation diagnosis apparatuses are used in all fields, such as nuclear facilities and nuclear engineering as well as medical fields, where radiations are emitted. 
     As shown in  FIG. 1 , in a radiation diagnosis apparatus according to the related art, all radiation detectors are connected to data acquisition units, respectively such that one data acquisition unit corresponds to an output of each radiation detector. 
       FIG. 1  is a schematic diagram of a radiation diagnosis apparatus according to the related art.  FIG. 1  shows only a relationship between two radiation detectors  10  and  20  and two data acquisition units  100  as an example. 
     That is, as shown in  FIG. 1 , an output of a first radiation detector  10  is input to one data acquisition unit  100 , and an output of a second radiation detector  20  is input to another data acquisition unit  100 . Each of the data acquisition units  100  is connected to a computer for signal processing and analysis. 
     However, in the radiation diagnosis apparatus, since one radiation detector requires one data acquisition unit  100 , data acquisition units  100  corresponding to the number of radiation detectors are necessary. 
     For this reason, the radiation diagnosis apparatus according to the related art has a drawback of a large volume, a heavy weight, and a high price. 
     The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in an effort to provide a radiation diagnosis apparatus which employs a reduced number of data acquisition units while showing the same effect as that of the related art. 
     An exemplary embodiment of the present invention provides a radiation diagnosis apparatus according to an exemplary embodiment of the present invention. The radiation diagnosis apparatus includes: a first radiation detector for detecting a radiation and generating an output signal in response to the detection of the radiation; a second radiation detector for generating an output signal having a same polarity as that of the first radiation detector; an inverter formed at an output terminal of the first radiation detector to invert the polarity of the input output signal; a discriminator for receiving a common signal from the first and second radiation detector and outputting a control signal corresponding to the input common signal; and a data acquisition unit for converting an input signal to a digital signal according to the control signal while taking output signals of the plurality of inverters and the second radiation detector as inputs, and identifying an output signal of which detector of the first and second detectors the input signal is according to a polarity difference of the input signal. 
     Another exemplary embodiment of the present invention provides a radiation diagnosis apparatus. The radiation diagnosis apparatus includes: a first radiation detector for detecting a radiation and generating an output signal corresponding to the detection of the radiation; a second radiation detector for generating an output signal having a same polarity as that of the first radiation detector; an inverter formed at a common signal output terminal of the first radiation detector to invert the polarity of the input common signal; a bipolar discriminator for receiving a common signal from the inverter and the second radiation detector and outputting a control signal corresponding to a polarity difference of the input common signal; and a data acquisition unit for converting an input signal to a digital signal according to the control signal while taking output signals of the first and second radiation detectors as inputs, and identifying an output signal of which detector of the first and second detectors the input signal is according to a polarity difference of the common signal. 
     The first radiation detector and the second radiation detector may be situated at adjacent locations. 
     The data acquisition unit may be a data acquisition (DAQ) board. 
     The bipolar discriminator may be connected to the data acquisition unit through two signal lines to provide a control signal corresponding to a common signal of the first radiation detector whose polarity is inverted through one of the signal lines and provide a control signal corresponding to a common signal of the second radiation detector whose polarity is non-inverted through the other signal line. 
     If the DAQ board identifies a detector corresponding to the input signal, the DAQ board may contain identifying information representing the identified detector in the digital signal to output the identifying information. 
     Another exemplary embodiment of the present invention provides a radiation diagnosis apparatus. The radiation diagnosis apparatus includes: a first radiation detector for detecting a radiation and generating an output signal corresponding to the detection of the radiation; a second radiation detector for generating an output signal whose polarity is the same as that of the first radiation detector; a first inverter formed at a plurality of output terminals of the first radiation detector to invert the polarity of the input output signal; third and fourth radiation detectors for generating output signals whose polarity is the same as that of the first radiation detector; a second inverter formed at a plurality of output terminals of the third radiation detector to invert the polarity of the input output signal; a third inverter formed at a common signal output terminal of the first and second radiation detectors to invert the polarity of the common signal of the first and second radiation detectors; a bipolar discriminator for receiving a common signal from the third inverter and the third and fourth radiation detectors through one input terminal and outputting a control signal corresponding to a polarity difference of the input common signal; and a data acquisition unit for converting an input signal to a digital signal while taking output signals of the first and second inverters and the third and fourth radiation detectors, and identifying an output signal of which detector of the first to fourth radiation detectors the input signal is based on a polarity difference of the common signal and a polarity difference of the input signal. 
     At least two of the first to fourth radiation detectors may be situated at adjacent locations. 
     The exemplary embodiment of the present invention provides a light and inexpensive radiation diagnosis apparatus which employs a reduced number of data acquisition units while showing the same effect as that of the related art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a radiation diagnosis apparatus according to the related art. 
         FIG. 2  is a schematic diagram of a radiation diagnosis apparatus according to an exemplary embodiment of the present invention. 
         FIG. 3  is a detailed diagram of a radiation diagnosis apparatus according to a first exemplary embodiment of the present invention. 
         FIG. 4  is a detailed diagram of a radiation diagnosis apparatus according to a second exemplary embodiment of the present invention. 
         FIG. 5  is a detailed diagram of a radiation diagnosis apparatus according to a third exemplary embodiment of the present invention. 
         FIG. 6  is a detailed diagram of a radiation diagnosis apparatus according to a fourth exemplary embodiment of the present invention. 
         FIG. 7  is a detailed diagram of a radiation diagnosis apparatus according to a fifth exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     In the following detailed description, only certain exemplary embodiments of the present invention have been shown and described, simply by way of illustration. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals designate like elements throughout the specification. 
     Now, the radiation diagnosis apparatuses according to the exemplary embodiments of the present invention will be described in detail. 
       FIG. 2  is a schematic diagram of a radiation diagnosis apparatus according to an exemplary embodiment of the present invention, and shows two radiation detectors  10  and  20  forming a pair as subject objects. Of course, two remaining ones of a plurality of radiation detectors constituting the radiation diagnosis apparatus according to the exemplary embodiment of the present invention form a pair, respectively so as to have the same forms as the two radiation detectors  10  and  20 . That is, as shown in  FIG. 2 , two of the plurality of radiation detectors forms a pair, respectively. 
     As shown in  FIG. 2 , the radiation diagnosis apparatus according to the exemplary embodiment includes a plurality of radiation detectors having an arbitrary form, a multiplexing unit  200  for selectively providing an output signal of a radiation detector of the plurality of radiation detectors one by one while taking an output signal of the two radiation detectors of the plurality of radiation detectors forming a pair as an input signal, and a data acquisition unit for converting an analog signal which is the output signal of the radiation detector input from the multiplexing unit  200  to a digital signal to provide the digital signal to a computer  300 . 
     The radiation detectors (including  10  and  20 ) constituting the radiation diagnosis apparatus according to the exemplary embodiment of the present invention detect gamma rays generated in the process of an unstable atomic nucleus turns into a stable state and an X-ray generated when an electron collides with an object at a high speed (that is, radiations). 
     In this case, the radiation detectors (including  10  and  20 ) have output signals of the same polarity due to detection of a radiation as in radiation detectors such as a photomultiplier tube (PMT) based detector, a cadmium zic telluride (CZT) based detector, an avalanche photo diode (APD) based detector, or a silicon photomultiplier (SiPM) based detector. That is, the radiation detectors (including  10  and  20 ) generate output signals of the same polarity. 
     The radiation detectors forming a pair may be set arbitrarily, but considering the design and wiring problems, they may be two upper and lower radiation detectors adjacent to each other or two left and right radiation detectors adjacent to each other.  FIG. 2  shows two upper and lower radiation detectors adjacent to each other as an example. 
     The two radiation detectors  10  and  20  detect a radiation with a time gap, and accordingly, generate output signals with a time gap to provide the output signals to the multiplexing unit  200 . 
     In this case, it has been described in the exemplary embodiment of the present invention with reference to  FIG. 2  that the output signals of the two radiation detectors are taken as an input of the multiplexing unit  200 , but the exemplary embodiment of the present invention is not limited thereto. 
     The reason will be easily described by those skilled in the art through the following description. 
     Now, a detailed example of the radiation diagnosis apparatus according to the exemplary embodiment of the present invention described with reference to  FIG. 2  will be described with reference to  FIGS. 3 and 4 . 
       FIG. 3  is a detailed diagram of a radiation diagnosis apparatus according to a first exemplary embodiment of the present invention. For convenience&#39; sake, two radiation detectors  10  and  20  forming a pair will be described as subject objects with reference to  FIG. 3 . 
     As shown in  FIG. 3 , the radiation diagnosis apparatus according to the first exemplary embodiment of the present invention includes first and second radiation detectors  10  and  20 , a multiplexing unit  200  including a plurality of inverters  210  and one discriminator  220 , and one data acquisition (DAQ) board  100 . 
     The DAQ board  100  is an example of a data acquisition unit. 
     The first and second radiation detectors  10  and  20  generate radiation detection signals (that is, output signals) corresponding to four sites situated with respect to installation locations thereof, and the four output signals are output through A, B, C, and D output terminals, respectively. 
     The same output terminals of the first and second radiation detectors  10  and  20  are connected to each other, and are connected to input terminals of the DAQ board  100  through a common line, respectively. That is, the A output terminal of the same output terminals of the first and second radiation detectors  10  and  20  is connected to the A input terminal of the DAQ board  100 , the B output terminal is connected to the B input terminal of the DAQ board  100 , the C output terminal is connected to the C input terminal of the DAQ board  100 , and the D output terminal is connected to the D input terminal of the DAQ board  100 . 
     In this case, inverters  210  are installed in the output terminals of the first radiation detectors  10 , respectively. 
     Hereinafter, an output signal output through the A output terminal of the first radiation detector  10  is denoted as S 11 , an output signal output through the B output terminal thereof is denoted as S 12 , an output signal output through the C output terminal thereof is denoted as S 13 , and an output signal output through the D output terminal thereof is denoted as S 14 . 
     Further, an output signal output through the A output terminal of the second radiation detector  20  is denoted as S 21 , an output signal output through the B output terminal thereof is denoted as S 22 , an output signal output through the C output terminal thereof is denoted as S 23 , and an output signal output through the D output terminal thereof is denoted as S 24 . 
     Since the first and second radiation detectors  10  and  20  generate output signals of the same polarity, S 11  to S 14  and S 21  to S 24  have the same polarity and the polarity of the output signals S 11  to S 14  of the first radiation detectors  10  is inverted by the inverter  210  to be input to the DAQ board  100 . In this case, the signals of the first radiation detector  10  whose polarity has been inverted will be denoted as S 11 ′, S 12 ′, S 13 ′, and S 14 ′. 
     The discriminator  220  generates a control signal synchronized with input of common signals c 1  and c 2  while taking the common signals c 1  and c 2  output from the first and second radiation detectors  10  and  20  as inputs, and inputs the control signal to the trigger terminal of the DAQ board  200 . An example of such a discriminator  220  may include a leading edge discriminator (LED) or all types of discriminators which discriminates the input signal that exceeds certain threshold to output a control signal. 
     Here, the first and second radiation detectors  10  and  20  generate common signals c 1  and c 2  when a radiation is detected, that is, when an output signal is generated. In this case, since the first and second radiation detectors  10  and  20  have a time gap when a radiation is detected, the common signals c 1  and c 2  do not overlap each other. 
     The DAQ board  100  inputs the output signals S 11 ′ to S 14 ′ or S 21  to S 24  of the first and second radiation detector  10  through the four input terminals A, B, C, and D. In addition, the DAQ board  100  provides an output signal input according to a control signal input from a trigger terminal to the computer  300 . 
     Thus, the DAQ board  100  sequentially converts the inverted signals S 11 ′ to S 14 ′ output from the first radiation detector  10  and the signals S 21  to S 24  output from the second radiation detector  20  to digital signals to output the digital signals. 
     The computer  300  determines a signal input from a specific DAQ board  100  as an output of the first radiation detector  10  if the input signal is an inverted signal, and determines the signal as an output of the second radiation detector  20  if the signal is not an inverted signal. 
     Of course, the DAQ board  100  identifies a radiation detector according to whether an input output signal is an inverted signal S 11 ′ to S 14 ′ or an non-inverted signal S 21  to S 24 , and the identifying information of the radiation detector may be contained in a digital signal transmitted to the computer  300  to be transmitted. 
     Hereinafter, a radiation diagnosis apparatus according to a second exemplary embodiment of the present invention will be described with reference to  FIG. 4 .  FIG. 4  is a detailed diagram of a radiation diagnosis apparatus according to a second exemplary embodiment of the present invention. 
     As shown in  FIG. 4 , the radiation diagnosis apparatus according to the second exemplary embodiment of the present invention includes first and second radiation detectors  10  and  20 , a multiplexing unit  200  including one inverter  210   a  and one bipolar discriminator  220   a , and one data acquisition (DAQ) board  100 . 
     The first and second radiation detectors  10  and  20  are the same as the first and second radiation detectors  10  and  20  according to the first exemplary embodiment of the present invention shown in  FIG. 3 . Further, like in the first and second radiation detectors  10  and  20  according to the first exemplary embodiment of the present invention, the same output terminals of the first and second radiation detectors  10  and  20  are connected to each other and are connected to the input terminals of the DAQ board  100  through a common line. 
     However, an inverter is not installed in each of the output terminals of the first radiation detector  10 . 
     A S 11  output signal or S 21  output signal is input to an A input terminal of the DAQ board  100 , an S 12  output signal or S 22  output signal is input to a B input terminal thereof, an S 13  output signal or S 23  output signal is input to a C input terminal thereof, and an S 14  output signal or S 24  output signal is input to a D input terminal thereof. 
     The inverter  210   a  is installed on a common line of the first radiation detector  10  to invert the polarity of the common signal c 1  to the polarity of the common signal c 1 ′. 
     The bipolar discriminator  220   a  generates a control signal synchronized with input of common signals c 1 ′ and c 2  while taking an inverted common signal c 1 ′ and a non-inverted common signal c 2  input from the first and second radiation detectors  10  and  20  as inputs, and inputs the control signal to a trigger terminal of the DAQ board  200 . 
     The bipolar discriminator  220   a  may be a bipolar leading edge discriminator (BLED) as an example, but the present invention is not limited thereto. 
     In this case, the bipolar discriminator  220   a  and the DAQ board  200  are connected to each other through two trigger signal lines, a control signal generated in response to the inverted common signal c 1 ′ is input to the first trigger terminal of the DAQ board  100  through one trigger signal line, and a control signal generated in response to the non-inverted common signal line c 2  is input to the second trigger terminal of the DAQ board  100  through another trigger signal line. 
     If a control signal is input to the first trigger terminal, the DAQ board  100  recognizes the input signal as an output signal of the first radiation detector  10 , and if a control signal is input to the second trigger terminal, and the DAQ board  100  recognizes the input signal as an output signal of the second radiation detector  20 . 
     If the DAQ board  100  recognizes the first radiation detector  10  or the second radiation detector  20  according to the type of the trigger terminal to which a control signal is input, the DAQ board  100  generates identifying information for recognizing the first or second radiation detector  10  or  20  in a digitalizing process such that the input signal is contained in the identifying information. 
     Thus, if the output signals S 11  to S 14  or S 21  to S 24  of the first or second radiation detector  10  or  20  are input through the input terminals A, B, C, and D of the four signal lines and a control signal is input from one of the first and second trigger terminals, the DAQ board  100  contains identifying information representing whether the input signal is an output signal of the first radiation detector  10  or an output signal of the second radiation detector  20  while converting the input signal to a digital signal to provide the digital signal to the computer  300 . 
     The computer  300  receives the digital signal input from the DAQ board  100  and determines whether the input digital signal is an output signal of the first radiation detector  10  or an output signal of the second radiation detector  20  through the identifying information contained in the digital signal. 
     Hereinafter, the radiation diagnosis apparatus according to a third exemplary embodiment of the present invention will be described with reference to  FIG. 5 . 
       FIG. 5  is a detailed diagram of a radiation diagnosis apparatus according to a third exemplary embodiment of the present invention. As shown in  FIG. 5 , the radiation diagnosis apparatus according to the third exemplary embodiment of the present invention is configured such that outputs of two pairs of radiation detectors, that is, four radiation detectors ( 10  and  20  forms a pair and  30  and  40  forms a pair) are transmitted to a computer  300  through one data acquisition unit  100 . 
     That is, the radiation diagnosis apparatus according to the third exemplary embodiment of the present invention includes four radiation detectors  10  to  40 , a multiplexing unit  200  including a plurality of inverters  210  and  210   a  and a bipolar discriminator  220   a , and one DAQ board  100 . 
     Here, the two pairs (hereinafter, referred to as “group”) coupled to the one data acquisition unit  100  may be set arbitrarily, but considering a design and wiring problem, they may be upper and lower pairs or left and right pairs adjacent to each other. 
     The inverter  210  is connected to output lines of the two radiation detectors forming a pair of the group. Thus, the pairs output output signals in the same structure as that of the first exemplary embodiment of the present invention. That is, one radiation detector  10  or  40  forming a pair outputs inverted signals S 11 ′ to S 14 ′ or S 41 ′ to S 44 ′ through the inverter  210 , and the remaining radiation detector  20  or  30  forming the pair output non-inverted signals S 21  to S 24  or S 31  to S 34 . 
     In this state, the same output terminals of the four radiation detectors  10  to  40  forming the group are connected to each other to be connected to an input terminal of one DAQ board  100 , respectively. 
     That is, A output terminals of the first to fourth radiation detectors  10  to  40  are connected to each other to be connected to an A input terminal of the DAQ board  100 , B output terminals thereof are connected to each other to be connected to a B input terminal of the DAQ board  100 , C output terminals thereof are connected to each other to be connected to a C input terminal of the DAQ board  100 , and D output terminals thereof are connected to each other to be connected to a D input terminal of the DAQ board  100 , 
     Thus, output signals of S 11 ′, S 21 , S 31 , and S 41 ′ are input to the A input terminal of the DAQ board  100 , output signals of S 12 ′, S 22 , S 32 , and S 42 ′ are input to the B input terminal, output signals of S 13 ′, S 22 , S 32 , and S 42 ′ are input to the C input terminal, and output signals of S 14 ′, S 24 , S 34 , and S 44 ′ are input to the D input terminal. 
     Meanwhile, common signals c 1  and c 2  of the first and second radiation detectors  10  and  20  forming a pair are inverted through the inverter  210   a  to be input to the bipolar discriminator  220   a , and common signals c 3  and c 4  of the third and fourth radiation detectors  30  and  40  forming a pair are connected to the bipolar discriminator  220   a  in a non-inverted state. That is, the bipolar discriminator  220   a  inputs common signals of c 1 ′, c 2 ′, c 3 , and c 4  through one input terminal. 
     Meanwhile, the bipolar discriminator  220   a  and the DAQ board  100  are connected to each other through two trigger signal lines, a control signal generated in response to the common signals c 1 ′ and c 2 ′ inverted through one trigger signal line is input to a first trigger terminal of the DAQ board  100 , and a control signal generated in response to the common signals c 3  and c 4  non-inverted through another trigger signal line are input to a second trigger terminal of the DAQ board  100 . 
     Thus, the DAQ board  100  recognizes one of the first to fourth radiation detectors  10  to  40  according to whether the input signal is an inverted signal or a non-inverted signal and whether the control signal is input to the first trigger terminal or the second trigger terminal. 
     The recognizing process can be expressed in a table as follows. 
     
       
         
               
               
               
             
           
               
                   
               
               
                 Type of Radiation 
                 Polarity of Input 
                 Polarity of Output Signal 
               
               
                 Detector 
                 Signal 
                 (Type of Trigger Terminal) 
               
               
                   
               
             
             
               
                 First Radiation Detector 
                 Inverted 
                 Inverted (First Trigger) 
               
               
                 Second Radiation 
                 Non-inverted 
                 Inverted (First Trigger) 
               
               
                 Detector 
                   
                   
               
               
                 Third Radiation Detector 
                 Non-inverted 
                 Non-inverted  
               
               
                   
                   
                 (Second Trigger) 
               
               
                 Fourth Radiation Detector 
                 Inverted 
                 Non-inverted  
               
               
                   
                   
                 (Second Trigger) 
               
               
                   
               
             
          
         
       
     
     The DAQ board  100  identifies a radiation detector according to the polarity of an input signal and the type of a trigger terminal as expressed in the above table, and accordingly after creating identifying information on the corresponding radiation detector, contains the input signal in the identifying information created in the digitalizing process to transmit the input signal to the computer  300 . 
     The computer  300  receives a digital signal input from the DAQ board  100 , and determines whether the digital signal is an output signal of the first radiation detector  10  or to an output signal of the fourth radiation detector  40  through identifying information contained in the digital signal. 
     Meanwhile, as another exemplary embodiment of the present invention, an inverter is installed in one of the plurality of output terminals in one radiation detector and an inverter is installed at an output terminal at another location in the other radiation detector forming a pair, so that a radiation detector is identified according to a location difference of output terminals of the two radiation detector whose output signals have different polarities. 
     The above-mentioned another embodiment of the present invention will be described in detail with reference to  FIGS. 6 and 7 . 
       FIG. 6  is a detailed diagram of a radiation diagnosis apparatus according to a fourth exemplary embodiment of the present invention. 
     As shown in  FIG. 6 , the radiation diagnosis apparatus according to the fourth exemplary embodiment of the present invention includes first and second radiation detectors  10  and  20 , a multiplexing unit  200  including a plurality of inverters  210  and one discriminator  220 , and one data acquisition (DAQ) board  100 . Here, the DAQ board  100  is an example of a data acquisition unit. 
     The configuration of the radiation diagnosis apparatus according to the fourth embodiment of the present invention is similar to that of the radiation diagnosis apparatus according to the first exemplary embodiment of the present invention. 
     However, the radiation diagnosis apparatus according to the fourth exemplary embodiment of the present invention is different from the first exemplary embodiment of the present invention in that two inverters  210  are installed on output wirings A and B of the output terminals A, B, C, and D. 
     According to the exemplary embodiment of the present invention, since the output terminals of the second radiation detector  20  generates output signals having a non-inverted polarity, it is easier in determining the polarity difference to output signals having an inverted polarity from the output terminals of the first radiation detector  10  as in the first exemplary embodiment of the present invention. 
     However, since output signals of the first radiation detector  10  are input to the discriminator  220  at the same time, even through at least one output signal of the four output signals of the first radiation detector  10  has an inverted polarity, it is possible to determine a polarity difference between the at least one output signal and the output signals of the second radiation detectors  20 . 
     Moreover, as shown in  FIG. 6 , if signals of the four output signals of the first radiation detector  10  output from two adjacent output terminals have an inverted polarity, it is possible to more clearly determine a polarity difference between the output signals of the first radiation detector  10  and the second radiation detector  20 . 
     As a result, according to  FIG. 6 , the DAQ board  100  determines the polarities of the output signals of the first or second radiation detector  10  or  20  input from the input terminals A, B, C, and D to determine that a signal input to the A input terminal and the B input terminal is an output signal of the first radiation detector if the signal has an inverted polarity. Of course, although  FIG. 6  illustrates that an inverter is connected to the output terminals A and B, the present invention is not limited thereto but an inverter may be connected to B and C, C and D, A and D, A and C, one of A, B, C, and D, or three of A, B, C, and D. 
       FIG. 7  is a detailed diagram of a radiation diagnosis apparatus according to a fifth exemplary embodiment of the present invention. 
     As shown in  FIG. 7 , the radiation diagnosis apparatus according to the fourth exemplary embodiment of the present invention includes first and second radiation detectors  10  and  20 , a multiplexing unit  200  including a plurality of inverters and one discriminator  220 , and a data acquisition (DAQ) board  100 . Here, the DAQ board  100  is an example of a data acquisition unit. 
     The configuration of the radiation diagnosis apparatus according to the fifth embodiment of the present invention is similar to that of the radiation diagnosis apparatus according to the first exemplary embodiment of the present invention. 
     However, the radiation diagnosis apparatus according to the fifth exemplary embodiment of the present invention is different from the fourth exemplary embodiment of the present invention in that two of four inverters  210  are installed on output wirings A and B of the output terminals A, B, C, and D of the first radiation detector  10 , and the remaining two inverters  210  are installed on output wirings C and D of the output terminals A, B, C, and D of the second radiation detector  20 . 
     That is, the fifth exemplary embodiment of the present invention is distinguished in that an inverter is installed in a wiring of an output terminal of the first radiation detector  20 . 
     In this case, in the fifth exemplary embodiment of the present invention, an output terminal installed when the inverter  210  is installed in the first and second radiation detectors  10  and  20  is different from those of the other exemplary embodiments of the present invention. That is, a type of an input terminal of the DAQ board to which the inverter  210  installed at an output terminal of the first radiation detector  10  is connected and a type of an input terminal of the DAQ board to which the inverter  210  installed at an output terminal of the second radiation detector  20  are different from each other. 
     A detailed example is as shown in  FIG. 7 . As shown in  FIG. 7 , the inverters  210  of the first radiation detector  10  are connected to output wirings of A and B output terminals connected to A and B input terminals of the DAQ board  100 , respectively. 
     On the contrary, the inverters  210  of the second radiation detector  20  are connected to output wirings of C and D output terminals connected to C and D input terminals of the DAQ board  100 . 
     In this case, the number of inverters  210  installed in the first radiation detector  10  may be not more than 3, and the number of inverters  210  installed in the second radiation detector  20  may also be not more than 3. However, output signals with an inverted polarity from the first radiation detector  10  and outputs signals with original polarity from the second radiation detector  20  or vice versa, are input to the input terminal of the same DAQ board  100  so that the DAQ board  100  can identify the radiation detectors  10  and  20  based on a polarity difference of output signals of the radiation detectors  10  and  20 . 
     With reference to  FIG. 7  as an example, if an inverted signal is input to the A and B input terminals, the DAQ board  100  determines that the input signal is an output signal of the first radiation detector  10 , and if an inverted signal is input to the C and D input terminals, the DAQ board  100  determines that the input signal is an output signal of the second radiation detector  20 . 
     Meanwhile, the fourth and fifth embodiments of the present invention may include four radiation detectors  10  to  40  like the third embodiment of the present invention. In this case, a configuration of the third embodiment of the present invention as an example is modified as follows. 
     Modification 1. Up to three inverters  210  are installed at four output terminals of a first radiation detector  10 , and no inverter  210  is installed at four output terminals of a second radiation detector  20 . Further, up to three inverters  210  are installed at four output terminals of a fourth radiation detector  40 , and no inverter  210  is installed at four output terminals of a third radiation detector  30 . 
     Modification 2. Up to three inverters are installed at four output terminals of a first radiation detector  10 , and up to three inverters  210  are also installed at four output terminals of a second radiation detector  20 . In this case, a type of an input terminal of the DAQ board to which an inverter  210  installed at an output terminal of the first radiation detector  10  and a type of an input terminal of the DAQ board to which an inverter  210  installed at an output terminal of the second radiation detector  20  are different from each other. 
     Up to three inverters  210  are installed at four output terminals of the fourth radiation detector  40 , and up to three inverters  210  are also installed at four output terminals of the third radiation detector  30 . In this case, a type of an input terminal of the DAQ board to which an inverter  210  installed at an output terminal of the fourth radiation detector  40  and a type of an input terminal of the DAQ board to which an inverter  210  installed at an output terminal of the third radiation detector  30  are different from each other. 
     Here, the number of inverters connected to the output terminals of the first and second detectors  10  and  20  may exceed N, but is preferably N for precise identification. Further, the number of inverters connected to the output terminals of the third and fourth detectors  30  and  40  may exceed N, but is preferably N for precise identification. 
     The above-mentioned exemplary embodiments of the present invention are not embodied only by an apparatus and method. Alternatively, the above-mentioned exemplary embodiments may be embodied by a program performing functions, which correspond to the configuration of the exemplary embodiments of the present invention, or a recording medium on which the program is recorded. These embodiments can be easily devised from the description of the above-mentioned exemplary embodiments by those skilled in the art to which the present invention pertains. 
     While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 &lt;Description of symbols&gt; 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 10, 20, 30, 40:  
                 Radiation detector 
               
               
                   
                 100:  
                 Data acquisition unit, DAQ board 
               
               
                   
                 200:  
                 Multiplexing unit  
               
               
                   
                 300:  
                 Computer