Patent Publication Number: US-2013239690-A1

Title: Mre excitation apparatus, excitation system, and excitation method

Description:
1. TECHNICAL FIELD 
     The present invention relates to an MRE excitation apparatus, excitation system and excitation method for exciting a test object during Magnetic Resonance Elastography (MRE) measurement. 
     2. BACKGROUND ART 
     As methods for exciting a test object (object that is being tested) such as a body during MRE measurement, there are methods that use piezoelectric elements, and there are methods that use sound pressure. In a method that uses a piezoelectric element, such as disclosed in Unexamined Japanese Patent Application Kokai Publication No. 2005-118406, a body is excited by pressing a piezoelectric element against the surface of the body. Moreover, in an excitation method that uses sound pressure, such as disclosed in National Patent Publication No. 2008-501416, a body is excited by way of a probe that is attached to the tip end of a tube and transmitting a longitudinal wave vibration of air that is generated by an acoustic speaker through the tube. 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Literature 1: Unexamined Japanese Patent Application Kokai Publication No. 2005-118406 
         Patent Literature 2: National Patent Publication No. 2008-501416 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     In MRE measurement it is necessary to vibrate the surface of the test object using an excitation apparatus, and to cause that vibration to propagate to the area of the object being measured (deep inside the body). However, in conventional excitation methods that use a piezoelectric element, the amount of displacement of the piezoelectric element was minute at only a few microns. Moreover, even in the case of a piezoelectric element actuator in which a plurality of piezoelectric elements are arranged in series, the amount of displacement is only several tens of microns, so that it was not possible to obtain sufficient amplitude for MRE measurement. Furthermore, in excitation methods that use sound pressure, the longitudinal vibration of the air is dampened while propagating through the inside of the tube, making it impossible to obtain sufficient amplitude during MRE measurement. 
     Taking the problems above into consideration, it is the objective of the present invention to provide an MRE excitation apparatus, excitation system and excitation method that are capable of vibrating a test object with an sufficient excitation amplitude during MRE measurement. 
     Solution to Problem 
     In order to accomplish the objective above, an MRE excitation apparatus according to a first aspect of the present invention is 
     an MRE excitation apparatus that excites a test object during MRE measurement, and comprises: 
     an excitation device that generates vibrations; and 
     a transmitter that is made using a non-magnetic material and that, with one end-section being fastened to the excitation device and the other end-section connecting to the test object, extends along the direction of vibration from the excitation device and transmits longitudinal vibration from the excitation device to the test object; wherein 
     the frequency of the vibration is 125 Hz or greater; 
     the amplitude of the vibration is 0.2 mm or greater; and 
     the primary natural frequency of the longitudinal vibration of the transmitter is further on the high side than the frequency band of the vibration from the excitation device. 
     An MRE excitation apparatus according to a second aspect of the present invention is 
     an MRE excitation apparatus that excites a test object during MRE measurement, and comprises: 
     an excitation device that generates a vibration; 
     a transmitter that is made using a non-magnetic material and extends along the direction that vibration is transmitted from the excitation device; 
     at least one direction changer; and 
     a transmitter on the test object side that is made using a non-magnetic material and that extends in an angle different than the direction that the transmitter extends; wherein 
     the one end-section of the transmitter is fastened to the excitation device, the other end-section of the transmitter is connected to the direction changer, and the transmitter transmits longitudinal vibration from the excitation device to the direction changer; 
     the direction changer changes the direction of the longitudinal vibration that is transmitted by the transmitter, and transmits the longitudinal vibration to the transmitter on the test object side; 
     the transmitter on the test object side is connected with the test object, and transmits the longitudinal vibration to the test object; 
     the frequency of the vibration is 125 Hz or greater; 
     the amplitude of the vibration is 0.2 mm or greater; and 
     the primary natural frequency of the longitudinal vibration of the transmitter and the transmitter on the test object side is further on the high side than the frequency band of the vibration from the excitation device. 
     The transmitter may be made using a non-metallic material. 
     The transmitter may be made using a GFRP material. 
     There may also be a support that is located between the one end-section and the other end-section of the transmitter, and that supports the transmitter. 
     The support may be made using a soft material, and have a holder that holds the transmitter. 
     An MRE excitation system according to a third aspect of the present invention is 
     an MRE excitation system that excites a test object during MRE measurement, and comprises: 
     an excitation device that generates vibration; and 
     a transmitter that transmits a longitudinal vibration from the excitation device to the test object; wherein 
     the frequency of the vibration is 125 Hz or greater; 
     the amplitude of the vibration is 0.2 mm or greater; 
     the primary natural frequency of the longitudinal vibration of the transmitter is further on the high side than the frequency band of the vibration from the excitation device; and 
     during MRE measurement, the frequency and amplitude of the longitudinal vibration that is generated by the excitation device is controlled so that variation in measurement values of the modulus of elasticity in the measurement area in the test object is minimized. 
     It is also possible to comprise a controller that automatically controls the frequency and amplitude of the vibration. 
     An MRE excitation method according to a fourth aspect of the present invention comprises 
     controlling the frequency and amplitude of the vibration so that variation in measurement values of the modulus of elasticity in a measurement area in a test object is minimized; 
     generating a vibration; and 
     exciting the test object with the vibration; wherein 
     the frequency of the vibration is 125 Hz or greater; and 
     the amplitude of the vibration is 0.2 mm or greater. 
     The controlling the frequency and amplitude of the vibration may be automatically controlled. 
     Advantageous Effects of Invention 
     With the present invention, it is possible to provide an MRE excitation apparatus, excitation system and excitation method that are capable of vibrating a test object with a sufficient excitation amplitude. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a drawing for explaining an example of using an MRE excitation apparatus of a first embodiment of the present invention; 
         FIG. 2  is a drawing summarizing the construction of an MRE excitation apparatus of embodiments of the present invention; 
         FIG. 3  is a drawing for explaining a 5 Gauss line; 
         FIG. 4A  is a drawing illustrating the relationship between the specific modulus of elasticity and the natural frequency (primary) for a plurality of transmitter lengths, and  FIG. 4B  is a drawing illustrating the physical properties and vibration transmission characteristics for various materials; 
         FIG. 5  is a partial cross-sectional drawing of a transmitter and a support in section A-A in  FIG. 2 ; 
         FIG. 6  is a perspective view for explaining an example of using an MRE excitation apparatus of another embodiment of the present invention; 
         FIG. 7  is a cross-sectional view of a direction changer in another embodiment of the present invention; 
         FIG. 8  is a drawing illustrating another form of a changer in another embodiment of the present invention; 
         FIG. 9  is a block diagram illustrating automatic control of the frequency and amplitude of vibration; 
         FIG. 10  is a flowchart illustrating the flow of automatic control of the frequency and amplitude of vibration; 
         FIG. 11  is a flowchart explaining an MRE excitation method; 
         FIG. 12A  is a drawing illustrating the input waveform and output waveform in a verification experiment, and  FIG. 12B  is a drawing illustrating a comparison of measurement results and theoretical values of the amplitude amplification ratio values in the verification experiment; 
         FIG. 13  is a drawing illustrating experimental results of directional change of the longitudinal vibration by a direction changer; 
         FIG. 14  is a drawing illustrating experimental results of MRE measurement; and 
         FIG. 15  is a drawing illustrating experimental results of MRE measurement. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     In the following, embodiments of the present invention will be explained with reference to the drawings. 
       FIG. 1  is a drawing for explaining an example of a use of an MRE excitation apparatus  100  (excitation apparatus for MRE) of an embodiment of the present invention. In a method of noninvasive imaging of the tissue of an object by Magnetic Resonance Imaging (MRI), the MRE excitation apparatus  100  of this embodiment is used for applying a mechanical vibration to the test object and performing MRE measurement that qualitatively and/or quantitatively measures dynamic characteristics such as the modulus of elasticity in the tissue of the test object. More specifically, as illustrated in  FIG. 1 , a bed  220  is provided so that part thereof can enter inside a gantry  210  of a MRI apparatus  200 , and a living body  300 , which is one example of a test object, is placed on the bed  220 . The body  300  is excited by an MRE excitation apparatus  100 , and a signal that is obtained by the MRI apparatus  200  is analyzed by an MRE image apparatus  400  (image apparatus for MRE), and the elastic properties of the living body  300  are obtained by making it possible to visualize that signal. In MRE measurement, construction other than the MRE excitation apparatus  100  of this embodiment is the same as the conventional construction disclosed, for example, in Unexamined Japanese Patent Application Kokai Publication No. 2005-118406 and National Patent Publication No. 2008-501416, so a detailed explanation of that construction is omitted. The entire specifications, claims and drawings of Unexamined Japanese Patent Application Kokai Publication No. 2005-118406 and National Patent Publication No. 2008-501416 are incorporated in this specification by reference. 
       FIG. 2  is a drawing summarizing the construction of an MRE excitation apparatus  100  of this embodiment. As illustrated in  FIG. 2 , the MRE excitation apparatus  100  comprises, for example, an excitation device  110 , a transmitter  120 , and a support  130 . 
     The excitation device  110  generates vibration. The direction (propagation direction) of the vibration that is generated by the excitation device  110  is, for example, a horizontal direction such as illustrated in  FIG. 1 . In a specified frequency band (for example, 50 to 250 Hz) as the excitation frequency band, the excitation device  110  is able to generate vibration having an amplitude that is equal to or greater than a specified amplitude (for example, 0.2 mm) that is sufficient for exciting the body  300 . As this kind of excitation device  110 , it is possible to employ, for example, a continuously variable electro-dynamic exciter that obtains an excitation force by supplying an alternating current to a driving coil that is located inside a ferromagnetic field that is generated by a permanent magnet or an exciting coil, and is capable of automatically controlling the frequency within a range of 1 to 500 Hz, and preferably within a range of 50 to 250 Hz, and controlling the amplitude within a range of 0.2 mm to 2.0 mm, and preferably within a range of 0.2 mm to 1.0 mm. 
     Here, the installation position of the excitation device  110  will be explained. The excitation device  110 , due to the effect of the magnetostatic field of the MRI apparatus  200 , cannot be placed near the MRI apparatus  200 . Therefore, in the MRE excitation apparatus  100  of this embodiment, the excitation device  110  is placed at a location that is separated far enough from the MRI apparatus  200  so as to not receive the effect on the magnetostatic field, and the vibration that is generated by the excitation device  110  is transmitted by way of the transmitter  120  to the living body  300  inside the MRI apparatus  200 . More specifically, the installation position of the excitation device  110  is set based on the intensity of the stray magnetic field from the MRI apparatus  200 . Typically, as illustrated in  FIG. 3 , a 5 Gauss line that indicates the region where the intensity of the stray magnetic field is 5 Gauss or greater is regulated for the MRI apparatus  200 . Normally, locations on the outside of the 5 Gauss line do not affect the operation of precision equipment such as heart pacemakers. Therefore, in this embodiment, the excitation device  110  is located on the outside of the 5 Gauss line. 
     The transmitter  120  vibrates longitudinally due to the vibration generated by the excitation device  110 , and transmits that longitudinal vibration to the living body  300 . Due to the necessity for the vibration to propagate well into the living body  300 , the transmitter  120  transmits longitudinal vibration, in which the propagation direction and vibration direction coincide with, to the living body  300 . The transmitter  120 , for example, is formed into a cylindrical shape, and as illustrated in  FIG. 2 , extends from the end-section  121  on the excitation device side that is fastened to the excitation device  110  in the direction of vibration of the excitation device  110 , or in other words, in the horizontal direction in  FIG. 1 . Here, the direction of vibration of the excitation device  110  is the same as the direction in which the vibration propagates through the transmitter  120 . As illustrated in  FIG. 1 , an end-section  122  on the test object side, which is the end-section on the opposite side from the excitation device  121 , is connected to the living body  300  by a belt  123  that is wrapped around the abdominal area of the living body  300  such that the longitudinal vibration of the transmitter  120  is transmitted to the living body  300 . Moreover, the length of the transmitter  120  is set according to the installation location of the excitation device  110  with respect to the living body  300  inside the MRI apparatus  200 . In other words, the length of the transmitter  120  has a specified length (for example, 3 m) that corresponds to the distance, for example, between the excitation device  110  that is located on the outside of the 5 Gauss line illustrated in  FIG. 3  and the living body  300  inside the MRI apparatus  200 . However, the length of the transmitter  120  is not limited to this value, and can be appropriately set to correspond with the intensity of the magnetostatic field of the MRI apparatus  200 . 
     Next, the material of the transmitter  120  will be explained. Three conditions for the material of the transmitter  120  are as follows: (1) vibration from the excitation device  110  can be transmitted to the living body  300  without being dampened; (2) the primary natural frequency of the longitudinal vibration is on the high side from the excitation frequency band; and (3) the material is a non-magnetic material. 
     First, the condition that, (1) vibration from the excitation device  110  can be transmitted to the living body  300  without being dampened, will be explained. In the MRE excitation apparatus  100  of this embodiment, this condition is satisfied by taking advantage of an amplitude magnification phenomenon in the transmitter  120 . The amplitude magnification phenomenon will be explained below. 
     The amplitude of the vibration that is generated by the excitation device  110  is amplified when transmitted by the transmitter  120 , and as a result, the vibration amplitude (output amplitude) that is outputted to the living body  300  from the end-section  122  on the test object side is greater than the vibration amplitude (input amplitude) of the excitation device  110 . Here, this phenomenon is called the amplitude magnification phenomenon. The amplitude magnification phenomenon will be explained from theoretical analysis of longitudinal vibration. When the transmitter  120  is modeled such that the length is L, the outer diameter is d, the inner diameter is d i  (0≦d i &lt;d), the density is ρ, the modulus of elasticity is E, the cross-sectional area is A, and the moment of inertial of area I for a hollow cylinder is used, the longitudinal vibration of the transmitter  120  can be expressed by the following expression. 
     
       
         
           
             
               
                 
                   
                     ρ 
                      
                     
                       
                         
                           ∂ 
                           2 
                         
                          
                         u 
                       
                       
                         ∂ 
                         
                           t 
                           2 
                         
                       
                     
                   
                   = 
                   
                     E 
                      
                     
                       
                         
                           ∂ 
                           2 
                         
                          
                         u 
                       
                       
                         ∂ 
                         
                           x 
                           2 
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     Expression 
                      
                     
                         
                     
                      
                     1 
                   
                   ] 
                 
               
             
           
         
       
     
     Here, u is the displacement in the axial direction of the transmitter  120 . The amplification factor α (output amplitude/input amplitude) of the displacement amplitude at the tip end of the shaft when the shaft is excited at a frequency f is as expressed by the following expression. 
     
       
         
           
             
               
                 
                   
                     α 
                      
                     
                       ( 
                       f 
                       ) 
                     
                   
                   = 
                   
                      
                     
                       
                         cos 
                         
                           - 
                           1 
                         
                       
                        
                       
                         ( 
                         
                           2 
                            
                           π 
                            
                           
                               
                           
                            
                           fL 
                            
                           
                             
                               ρ 
                               E 
                             
                           
                         
                         ) 
                       
                     
                      
                   
                 
               
               
                 
                   [ 
                   
                     Expression 
                      
                     
                         
                     
                      
                     2 
                   
                   ] 
                 
               
             
           
         
       
     
     As illustrated by Expression 2, the amplitude amplification factor α is expressed by a function of the excitation frequency f, length L and specific modulus of elasticity E/ρ. Therefore, in order to transmit the vibration from the excitation device  110  to the living body  300  without being damped, the material of the transmitter  120  should be selected so as to have a specific modulus of elasticity that results in an amplitude amplification factor α being 1.0 or greater in the excitation frequency band. 
     Next, that condition that, (2) the primary natural frequency of the longitudinal vibration is on the high side from the excitation frequency band, will be explained. Here, when the transmitter  120  is such that the length is L, the density is ρ, and the modulus of elasticity is E, the n-th natural frequency f ns  of the longitudinal vibration of the transmitter  120  is expressed by the following expression. 
     
       
         
           
             
               
                 
                   
                     f 
                     ns 
                   
                   = 
                   
                     
                       
                         
                           
                             2 
                              
                             
                                 
                             
                              
                             n 
                           
                           + 
                           1 
                         
                         
                           4 
                            
                           
                               
                           
                            
                           L 
                         
                       
                        
                       
                         
                           E 
                           ρ 
                         
                       
                     
                     = 
                     
                       
                         
                           
                             2 
                              
                             
                                 
                             
                              
                             n 
                           
                           + 
                           1 
                         
                         4 
                       
                        
                       
                         1 
                         L 
                       
                        
                       
                         
                           E 
                           ρ 
                         
                       
                        
                       
                           
                       
                        
                       
                         ( 
                         
                           
                             n 
                             = 
                             0 
                           
                           , 
                           1 
                           , 
                           2 
                           , 
                           … 
                         
                          
                         
                             
                         
                         ) 
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     Expression 
                      
                     
                         
                     
                      
                     3 
                   
                   ] 
                 
               
             
           
         
       
     
     As illustrated in Expression 3, the natural frequency of the longitudinal vibration is expressed as a function of the length L and specific modulus of elasticity E/ρ. In this embodiment, by assuming that the length L of the transmitter  120  has been set in advance by setting the installation location of the excitation device  110 , the material of the transmitter  120  should be selected so as to have a specific modulus of elasticity that results in the primary natural frequency of the longitudinal vibration being separated on the high side from the excitation frequency band. As a result, it is possible to prevent damage due to resonance of the transmitter  120 . 
       FIG. 4A  is a drawing illustrating the relationship between the specific modulus of elasticity and the primary natural frequency found from Expression 3 for lengths L=1, 2 and 3 m. For example, when L=3 m, by selecting a material having a specific modulus of elasticity of 9 MPa·m 3 /kg or greater, the primary natural frequency exceeds the upper frequency limit of 250 Hz when the excitation frequency band is taken to be 250 Hz or less, so it is possible to prevent damage due to resonance of the transmitter  120 . 
     Next, the condition that, (3) the material is a non-magnetic material, will be explained. The reason for this, is that when the material of the transmitter  120  is ferromagnetic material, it is attracted toward the magnetostatic field of the MRI apparatus  200 . Moreover, it is further preferred that the material of the transmitter  120  be a non-metallic material. Even in the case where the material is a non-magnetic metal, when the transmitter  120  is caused to vibrate inside the magnetostatic field, an eddy current occurs inside the metal body due to electromagnetic induction. There is a possibility that a magnetic field will be generated due to this eddy current, and will affect the magnetostatic field of the MRI apparatus  200 . 
     Next,  FIGS. 4A and 4B  will be used to explain in detail how to determine the material of the transmitter  120  based on the conditions (1) to (3) explained above. In the following explanation, as an example, the case in which the excitation frequency band is 50 to 250 Hz, and the length of the transmitter  120  is 3 m will be explained.  FIG. 4A  is a drawing illustrating the relationship between the specific modulus of elasticity and the primary natural frequency resulting from Expression 3, and  FIG. 4B  illustrates the physical properties and the vibration transmission characteristics of various materials. First, for condition (1), the material listed in  FIG. 4A  and  FIG. 4B  satisfy this condition. Moreover, from the aspect of condition (2), ABS (Acrylonitrile Butadiene Styrene) and acryl are not appropriate, because the primary natural frequency is within the excitation frequency band. Furthermore, for condition (3), stainless steel, titanium and duralumin, which are non-magnetic, satisfy this condition. As was described above, there is a possibility of affecting the magnetostatic field inside the gantry  210  of the MRI apparatus  200 , so that preferably the transmitter  120  is made of a non-metallic material. Therefore, in the MRE excitation apparatus  100  of this embodiment, preferably the material of the transmitter  120  is GFRP (Glass Fiber Reinforced Plastic). However, material suitable for the transmitter  120  is not limited to this, and as long as the material satisfies the conditions (1) to (3) above, it is possible to select any suitable material according to the excitation frequency band, amplitude amplification factor and length of the transmitter  120  and the like. 
     The support  130  is located between the end-section  121  on the excitation device side of the transmitter  120  and the end-section  122  on the test object side, and supports the transmitter  120  so that the transmitter  120  can transmit longitudinal vibration. Moreover, the support  130  suppresses transverse vibration that occurs due to the weight of the transmitter  120 . 
     Here, for a model that is the same as that in the case of longitudinal vibration described above, the natural frequency of the transverse vibration of the transmitter  120  is expressed by the following expression. 
     
       
         
           
             
               
                 
                   
                     
                       f 
                       n 
                     
                     = 
                     
                       
                         
                           1 
                           
                             2 
                              
                             π 
                           
                         
                          
                         
                           
                             λ 
                             n 
                             2 
                           
                           
                             L 
                             2 
                           
                         
                          
                         
                           
                             EI 
                             
                               ρ 
                                
                               
                                   
                               
                                
                               A 
                             
                           
                         
                       
                       = 
                       
                         
                           
                             λ 
                             n 
                             2 
                           
                           
                             8 
                              
                             π 
                           
                         
                          
                         
                           1 
                           
                             L 
                             2 
                           
                         
                          
                         
                           
                             E 
                             ρ 
                           
                         
                          
                         
                           
                             
                               d 
                               2 
                             
                             + 
                             
                               d 
                               i 
                               2 
                             
                           
                         
                       
                     
                   
                    
                   
                       
                   
                    
                   
                     
 
                   
                    
                   
                     ( 
                     
                       
                         λ 
                         = 
                         4.730 
                       
                       , 
                       
                         7.853 
                          
                         
                             
                         
                          
                         … 
                       
                     
                      
                     
                         
                     
                     ) 
                   
                 
               
               
                 
                   [ 
                   
                     Expression 
                      
                     
                         
                     
                      
                     4 
                   
                   ] 
                 
               
             
           
         
       
     
     As illustrated in Expression 4, the natural frequency of the transverse vibration is expressed as a function of the length L, specific modulus of elasticity E/ρ, outer diameter d and inner diameter d i . Here, fundamentally, it is necessary to determine the material of the transmitter  120  so that both the natural frequency of this transverse vibration and the natural frequency of the longitudinal vibration described above are outside the excitation frequency band. However, for example, in the case of a model where the material of the transmitter  120  is GFRP (modulus of elasticity E=31 GPa, density ρ=1800 kg/m 3 ), and is a hollow cylinder having an outer diameter d=10 mm and inner diameter d i =8 mm, the primary natural frequency of the transverse vibration is 3.6 Hz. In this way, the primary natural frequency of the transverse vibration is very low, and it is difficult to make that primary natural frequency outside the excitation frequency band. Therefore, in this embodiment, the transverse vibration is absorbed and suppressed by the support  130  supporting the transmitter  120 . 
     Next, the detailed construction of the support  130  will be explained. The support  130 , as illustrated in  FIG. 2  and  FIG. 5 , for example, comprises a column  131  that extends upward from the floor, and a holder  132  that is provided on the top end-section. The column  131  is made of an acrylic resin that is non-magnetic for example, and an upward facing concave section  131   a  having a U-shaped cross section is formed in the top end-section of that column section  131 . The column  131  supports the transmitter  120  by way of the holder  132  that is provided inside this concave section  131   a.    
     The holder  132  is for holding the transmitter  120 . The holder  132 , for example, as illustrated in  FIG. 5 , has a curved surface  132   a  that comes in contact around part of the circumferential surface of the transmitter  120 . Moreover, the holder  132  is made of a non-magnetic material such as urethane resin. 
     Furthermore, the holder  132  is preferably a viscoelastic member that is capable of suitably transmitting longitudinal vibration and absorbing transverse vibration. In this case, due to the elastic component of the holder  132 , the holder  132  itself deforms and allows displacement in the axial direction of the transmitter  120 , so it is possible to suppress damping of the longitudinal vibration. Therefore, chattering vibration cause by friction, which becomes a problem in normal contact support, does not occur, and thus there is an advantage in that disorder in the waveform of the longitudinal vibration that is caused by that chattering vibration does not occur. Moreover, due to the viscoelastic component of the holder  132 , it is possible to effectively absorb and suppress transverse vibration that occurs in the transmitter  120 . As the material for the holder  132 , a soft material, such as soft urethane or sponge, is preferred. 
     In  FIG. 1 , the transmitter  120  is supported by two supports  130 , however, the number of supports  130  is not limited to this. The greater the number of supports  130 , the more the transverse vibration can be absorbed and suppressed. 
     The operation during excitation of the MRE excitation apparatus  100 , which is constructed as described above, will be explained. In MRE measurement, the excitation device  110  is controlled so that a vibration having a specified frequency in the excitation frequency band (for example, 50 to 250 Hz) and a specified amplitude (for example, 0.25 mm) is outputted. The end-section  121  on the excitation device side of the transmitter  120 , which extends in the direction of vibration, is excited by the vibration generated by the excitation device  110 . Longitudinal vibration of the transmitter  120  that is generated by the excitation of the end-section  121  on the excitation device side is transmitted to the living body  300  by way of the end-section  122  on the test object side. During this time, due to the amplitude amplification phenomenon described above, the amplitude of the longitudinal vibration, which is transmitted to the living body  300  by way of the end-section  122  on the test object side, is transmitted without being dampened. Moreover, the primary natural frequency of the transmitter  120  is further on the high side than the excitation frequency band, so that there is no damage to the transmitter  120  due to resonance. Furthermore, transverse vibration that is generated in the transmitter  120  is absorbed and suppressed by the holder  132  of the support  130 . 
     With this kind of construction, the MRE excitation apparatus  100  of this embodiment is able to transmit vibration, which is generated by an excitation device  110 , to a body  300  as longitudinal vibration without being dampened by way of a transmitter  120  that is made using a non-magnetic material and that has a primary natural frequency that is further on the higher side than the excitation frequency band. Therefore, in MRE measurement, it is possible to excite a test object with sufficient excitation amplitude. Moreover, by absorbing and suppressing transverse vibration while at the same time allowing longitudinal vibration in the support  130 , it is possible to output vibration having little noise to the living body  300 . 
     Furthermore, in the MRE excitation apparatus  100  of this embodiment, the transmitter  120  is made using a non-metallic material, so that the magnetostatic field of the MRI apparatus  200  is not affected even when the transmitter  120  vibrates. 
     In the MRE excitation apparatus  100  of this embodiment, the transmitter  120  is made using a GFRP material, so that it is possible to transmit longitudinal vibration, having an amplitude that is suitably amplified, to the living body  300  without affecting the magnetostatic field generated by the MRI apparatus  200 . 
     Moreover, in the MRE excitation apparatus  100  of this embodiment, the support  130  is made using a soft material and has a holder  132  that holds the transmitter  120 , so it is possible to suitably absorb and suppress transverse vibration in the transmitter  120 . 
     The present invention is not limited to the embodiment described above, and various modifications and applications are possible. For example, as illustrated in  FIG. 1 , the end-section  122  on the test object side of the transmitter  120 , is connected to the living body  300  by a belt  123  that is placed around the abdominal area of the living body  300 . However, the connection method is not limited to this, and as long as it is possible to transmit the longitudinal vibration of the transmitter  120  to the living body  300 , the connection method can be appropriately changed according the measurement site on the living body  300 . For example, when the head area of the living body  300  is to be measured, it is possible to fasten the other end-section of the transmitter  120  to a helmet fitted to the living body  300 , and to transmit the longitudinal vibration to the head of the living body  300  by way of the helmet. 
     Moreover, in this embodiment, the case of providing a support  130  that supports the transmitter  120  and that is located between one end-section and the other end-section of the transmitter  120  was explained, however, it is also possible for the transmitter to be supported by the excitation device  110  and the belt  123  without providing a support  130 . 
     Furthermore, in this embodiment, the case of using a living body  300  as the test object was explained, however, as long as the test object is an object having a low modulus of elasticity, the test object could be, but is not limited to, an object such as a biological sample such as an organ, a polymer gel, a food such as konnyaku, agar and the like. 
     In this embodiment, as illustrated in  FIG. 1 , a case that a vibration generated by an excitation device  110  is linearly transmitted to a living body  300  by way of a transmitter  120  and the living body  300  is excited by the vibration was explained; however, the transmission direction for transmitting the vibration is not limited to a linear direction, and it is possible for the transmission direction for transmitting the vibration to change en route. For example, the MRE excitation apparatus  150  is not limited to the following components; however, as illustrated in  FIG. 6 , can also comprise a transmitter  140  that is made using a non-magnetic material and that extends along the direction that the vibration is generated from the excitation device  110 , a direction changer  144 , a transmitter  142  on the test object side that is made using a non-magnetic material and that extends at an angle that is different than the direction in which the transmitter  140  extends, and a support  130  that is located between one end-section and the other end-section of the transmitter  140  and that supports the transmitter  140 . It is also possible to have a support  146  having an arch shape, for example, that supports the direction changer  144 , and to provide that support  146  between the bed  220  and the direction changer  144 . The support  146 , for example, as illustrated in  FIG. 6 , is provided so that the bottom section of the support  146  comes in contact with the top surface of the bed  220 , and the top section of the arch shape of the support  146  comes in contact with the bottom surface of the direction changer  144 . The transmitter  142  on the test object side comprises a test object excitation probe that is provided on the tip end thereof. As the material for the support  146 , it is possible to use, for example, a fiber reinforced plastic (FRP). 
     In the form illustrated in  FIG. 6 , one end-section of the transmitter  140  is fastened to the excitation device  110 , and the other end-section of the transmitter  140  is connected to the direction changer  144 . The transmitter  140  has the function of transmitting longitudinal vibration from the excitation device  110  to the direction changer  144 . The direction changer  144  has the function of changing the direction of the longitudinal vibration that is transmitted by way of the transmitter  140  to a substantial perpendicular direction, and transmitting the longitudinal vibration to the transmitter  142  on the test object side. The transmitter  142  on the test object side has the function of a test object excitation probe provided on the tip end thereof connecting to the test object (living body  300 ), and transmitting the longitudinal vibration to the test object. The other construction and functions are the same as the construction and functions of the MRE excitation apparatus  100  illustrated in  FIG. 1 , so a detailed explanation is omitted. 
     The material of the transmitter  140  and the transmitter  142  on the test object side is the same as that of the transmitter  120  described above, and is appropriately selected so as to satisfy the following three conditions: (1) capable of transmitting longitudinal vibration from the excitation device  110  to the living body  300  without the vibration being dampened, (2) the primary natural frequency of the longitudinal wave is on the high side from the excitation frequency band, and (3) the material is non-magnetic. 
     The direction changer  144  comprises a housing  144   a  and a changer  144   b .  FIG. 7  is a cross-sectional drawing illustrating the direction changer  144  and the method of changing the direction of the longitudinal vibration. In  FIG. 7 , the shape (ring shape) of the direction changer before the longitudinal vibration is transmitted to the direction changer is illustrated with dashed lines ( 144   b ), and the shape of the direction changer when changing the direction of the longitudinal vibration is illustrated by the solid line ( 144   b ′). 
     As illustrated in  FIG. 7 , the changer  144   b  is pressed in the direction of the arrow F 1  by the longitudinal vibration that is transmitted from the transmitter  140  and that advances in the direction indicated by the arrow F 1 . The pressed changer  144   b  deforms as illustrated in  FIG. 7 , and the direction of the longitudinal vibration is changed to the direction indicated by the arrow F 2  by being constrained between the changer  144   b  and the housing  144   a , and is then transmitted to the transmitter  142  on the test object side. 
     In  FIG. 7 , a form in which the shape of the changer  144   b  is a ring-shaped single member is explained; however, the shape can be appropriately selected within a range that allows for the function described above; for example, a polygonal shape or the like that comprises a hinge  148  such as illustrated in  FIG. 8  is also possible. Moreover, characteristics, such as rigidity, of the changer  144   b  are also appropriately selected within a range that allows for the function described above. 
     In  FIG. 6 , a form in which an arch-shaped support  146  is provided between the bed  220  and the direction changer  144  was explained, however, the shape, material and installation position of the support  146  is appropriately selected within a range that allows for the function described above. 
     With the direction changer  144 , it is possible in the MRE excitation apparatus  150  to easily change the excitation direction of the longitudinal vibration that is generated by the excitation device  110 , and thus it becomes possible to reduce loss that occurs when transmitting the longitudinal vibration. Therefore, it is possible to provide a highly precise and strong longitudinal vibration to the living body  300  even when the longitudinal vibration that is generated by the excitation device  110  and transmitted by way of a first transmitter  140  that extends in the substantially horizontal direction excites the living body  300  in a substantially vertical direction. Consequently, even in the case of a site on the living body  300  where it is desired that excitation be in the substantially vertical direction, it is possible to apply excitation with a highly precise and strong longitudinal vibration using an MRE excitation apparatus  150 , and thus it is possible to perform good MRE measurement in many different sites. 
     Furthermore, in the embodiment illustrated in  FIG. 6 , the case in which the angle between the transmitter  140  and the transmitter  142  on the test object side is substantially a right angle was explained; however, as long as the angle is within a range that allows for the function described above, it is possible for the angle between the transmitter  140  and the transmitter  142  on the test object side to be an angle other than a substantially right angle. Furthermore, in the embodiment illustrated in  FIG. 6 , the case in which only one direction changer  144  is used was explained; however, it is also possible to provide two or more direction changers. 
     In this embodiment, an aspect in which a support  130  or the like was used was explained, however, in other aspects, an MRE excitation system that excites a test object during MRE measurement and that comprises an excitation device that generates vibration, and a transmitter that transmits longitudinal vibration from the excitation device to a test object is also possible. In an MRE excitation system, in order to minimize variation in the measurement values of the modulus of elasticity in the measured area in a test object, the frequency and amplitude of the longitudinal vibration that is generated by the excitation device are controlled. Moreover, in an MRE excitation system, as in the case of an MRE excitation apparatus  100 , the primary natural frequency of the longitudinal vibration of the transmitter is further on the high side than the frequency of the vibration from the excitation device. 
     For a frequency and amplitude of the longitudinal vibration which minimizes variation in the measurement values of the modulus of elasticity in a measured area of a test object, preferably a longitudinal vibration is selected such that the frequency is in the range 125 to 500 Hz, and the amplitude is in the range 0.2 to 2.0 mm. More preferably a longitudinal vibration is selected such that the frequency is in the range 125 to 250 Hz, and the amplitude is in the range 0.2 to 1.0 mm. Even more preferably, a longitudinal vibration is selected such that the frequency is in the range 125 to 250 Hz, and the amplitude is in the range 0.2 to 0.5 mm, and yet even more preferably, a longitudinal vibration is selected such that the frequency is 250 Hz, and the amplitude is 0.5 mm. Therefore, preferably, when a longitudinal vibration having a frequency of 125 to 500 Hz and an amplitude of 0.2 to 2.0 mm, and more preferably, a longitudinal vibration having a frequency of 125 to 250 Hz and an amplitude of 0.2 to 1.0 mm, and even more preferably, a longitudinal vibration having a frequency of 125 to 250 Hz and an amplitude of 0.2 to 0.5 mm, and yet even more preferably, a longitudinal vibration having a frequency of 250 Hz and an amplitude of 0.5 mm is selected, the precision of the MRE measurement becomes higher, or in other words, the reliability becomes greater, imaging becomes possible using an MRE image apparatus  400  without the need for special data processing by a computer, and it becomes easier to obtain the elastic property of the living body  300 . When the frequency is too high, it becomes difficult to synchronize the phase of the longitudinal vibration and the phase of the Motion Sensitizing Gradient (MSG), so using a longitudinal vibration having a high frequency and large amplitude within a range where it is possible to synchronize the phase of the longitudinal vibration and the MSG phase, where it is possible to transmit the longitudinal vibration a long distance, and where it is possible to measure within deep sections in the test object is even more preferable. 
     Above, a preferable range, a more preferable range, an even more preferable range and yet an even more preferable range for the frequency and amplitude of the longitudinal vibration were explained; however, the frequency and amplitude of the longitudinal vibration that is generated by the excitation device  110  can be appropriately selected within a range where it is possible to transmit the longitudinal vibration a long distance, where it is possible to measure sections including within deep sections in the test object, and where it is possible to obtain an image with the MRE image apparatus  400  without the need for special data processing by a computer, and where it is possible to easily obtain the elastic property of the living body  300 . For example, including but not limited to the following, it is possible to select a longitudinal vibration having a frequency of 62.5 Hz and an amplitude of 5.0 mm, or to select a longitudinal vibration having a frequency of 300 Hz and an amplitude of 0.3 mm. 
     The frequency and amplitude of the longitudinal vibration can be controlled manually, or can be controlled automatically. In the case where control is performed manually, the user adjusts the frequency and amplitude of the longitudinal vibration of an alternating current that is supplied to the excitation device  110  while monitoring the condition of the variation in the modulus of elasticity that appears in the image of the MRE image apparatus  400 . 
     Moreover, when the frequency and amplitude of the longitudinal vibration are controlled automatically, control is performed such as described in the following. 
     As illustrated in  FIG. 9 , there is a controller  160  that sets the operation parameters for the excitation device  110  and MRI apparatus  200 . 
     The controller  160  is provided with a CPU (Central Processing Unit), a memory, an input/output device and the like, and sets the operation parameters for the excitation device  110  and MRI apparatus  200  in response to instructions from the user. 
     Next, the processing by the controller  160  for controlling the frequency and amplitude of the longitudinal vibration will be explained with reference to  FIG. 10 . 
     For example, in response to an instruction from the user to start processing to search for the optimum frequency and amplitude, the controller  160  sets the frequency f of the vibration generated by the excitation device  110  to the lower limit value f o  of the variable range, for example, 125 Hz (step S 01 ). Next, the controller  160  sets the amplitude A m  of the vibration to the minimum value A 0 , for example, 0.2 mm (step S 02 ). 
     The controller  160  then transmits the frequency f and amplitude A m  that were set to the excitation device  110 , and causes the excitation device  110  to start excitation (step S 03 ). 
     Next, the controller  160  sets the operation parameters for the MRI apparatus  200  so that the excitation operation and imaging operation of the MRI apparatus  200  is synchronized with the longitudinal vibration generated by the excitation device  110 , and starts the excitation operation and imaging operation (step S 04 ). Moreover, the controller  160  sets the resolution of the image to be obtained to a resolution that is lower than the resolution of the image that will finally be obtained. 
     After the MRI apparatus  200  and MRE image apparatus  400  obtain an image, the controller  160  obtains this image data (voxel data), and saves that data in a memory  170  (step S 05 ). 
     Next, the controller  160  reads the values of all pixels of the image data stored in the memory  170  (values corresponding to the modulus of elasticity of the site corresponding to the test object), and finds the variation (variance σ 2  or standard deviation σ). In other words, the controller  160 , as a variation calculator, calculates the variation in the modulus of elasticity in a measured area of the test object. The controller  160  stores the calculated variation, together with the frequency f and amplitude A m , in the memory  170  (step S 06 ). 
     The controller  160  then determines whether or not the amplitude A m  has reached an upper limit value, for example, 1.5 mm (step S 07 ), and when it is determined that the amplitude A m  has not reached the upper limit value (step S 07 : NO), the controller  160  adds a minute value ΔA m , for example, 0.1 mm, to the amplitude A m  (step S 08 ). After that, the controller  160  repeats the processing of step S 03  to step S 07 . 
     When it is determined that the amplitude A m  has reached the upper limit (step S 07 : YES), the controller  160  then determines whether or not the vibration f has reached an upper limit value, for example, 250 Hz (step S 09 ), and when it is determined that the vibration f has not reached the upper limit value (step S 09 : NO), the controller  160  adds a minute value Δf, for example, 2.5 Hz, to the frequency f (step S 10 ). After that, the controller  160  repeats the processing of step S 02  to step S 09 . 
     When it is determined that the frequency f has reached the upper limit value (step S 09 : YES), the controller  160  then selects the frequency and amplitude for which variation is a minimum (optimum frequency and amplitude) from the variation of the modulus of elasticity, the frequency f and amplitude A m  saved in the memory  170  in step S 06  (step S 11 ). The frequency and amplitude of the longitudinal vibration are automatically controlled by the steps described above. 
     Next, with the test object that was used for selecting the optimum frequency and amplitude in step S 01  to step S 11  in place on the bed as is, the controller  160  transmits the optimum frequency and amplitude to the excitation device  110  and causes excitation to begin. The controller  160  then synchronizes the longitudinal vibration that is generated by the excitation device  110  with the excitation operation and imaging operation by the MRI apparatus  200 . Then, MRE measurement is performed in which the MRI apparatus  200  and MRE image apparatus  400  obtain a final image. 
     Moreover, it is also possible to place a test object that is different than the test object that was used for selecting the optimum frequency and amplitude on the bed, and then have the controller  160  transmit the optimum frequency and amplitude above to the excitation device  110  and cause the excitation device to start excitation, synchronize the longitudinal vibration that is generated by the excitation device  110  with the excitation operation and imaging operation of the MRI apparatus  200 , and perform MRE measurement in which the MRI apparatus  200  and MRE image apparatus  400  obtain a final image. 
     Also, an MRE excitation method that uses the MRE excitation apparatus  100  is performed, for example, as described in the following ( FIG. 11 ). 
     From step S 01  through step S 11  described above, the controller  160  automatically controls the frequency and amplitude of the longitudinal vibration (step S 101 ). 
     The excitation device  110  generates vibration of which the frequency and amplitude have been automatically controlled by step S 101  (step S 102 ), transmits a longitudinal vibration to a test object (a living body  300 ) using a transmitter  120  and a belt  123 , and performs MRE excitation of the living body  300  (step S 103 ). Here, steps S 102  and S 103  can be performed at the same time. It is also possible to manually control the frequency and amplitude of the longitudinal vibration that is generated by the excitation device  110 . 
     Here, the process for performing MRE excitation using an MRE excitation apparatus  100  was explained; however, it is also possible to perform MRE excitation using an MRE excitation apparatus  150 , or to perform MRE excitation using an MRE excitation system. 
     EXAMPLES 
     The present invention will be explained in detail using some examples. 
     Example 1 
     In the following, the result of a verification test that was performed for comparing input and output waveforms by the MRE excitation apparatus  100  described above will be explained. 
     In this example, the excitation frequency band was taken to be 50 to 250 Hz, and a pipe made of GFRP was used as the transmitter  120 . This pipe has a length L=3 m, and outer diameter d=10 mm, and inner diameter d i =8 mm, and the primary natural frequency of the longitudinal vibration that is calculated from Expression 3 is 346 Hz. This value was greater than 250 Hz, which is the upper limit of the excitation frequency band. 
     Next,  FIG. 12A  illustrates the input waveform, and the output waveform at the other end of the pipe, when one end-section of the pipe was excited by an electro-dynamic exciter with an input amplitude of 250 μm and an excitation frequency of 250 Hz. As illustrated in  FIG. 12A , it was found that the output waveform was in the same phase with the input waveform and was a sine wave having little noise.  FIG. 12B  illustrates the measurement results of the amplitude amplification ratio at excitation frequencies from 50 to 250 Hz. As illustrated in  FIG. 12B , the amplitude amplification ratio showed a tendency to coincide well with the theoretical value over the entire excitation frequency band. 
     From the verification test described above, it was found that, in the longitudinal vibration of the end-section  122  on the test object side when the end-section  121  on the excitation device side of the transmitter  120  in this embodiment was excited, the output amplitude was greater than the input amplitude and thus a sufficient output amplitude can be obtained in MRE measurement. 
     Example 2 
     In the following, test results that illustrate direction change by the direction changer  144  will be explained. 
       FIG. 13  is a drawing illustrating the waveforms of 125 Hz and 250 Hz vibrations before and after direction change. Two accelerometers for measuring the response before direction change and after direction change were used, and data processing was performed with measurement software LabVIEW (National Instruments Corporation). In  FIG. 13 , vibration on the input side that was generated by the excitation device  110  and transmitted to the changer  144   b  by way of the transmitter  140  (direction before change) is illustrated by the dark colored line (line A), and the vibration on the output side for which direction has been changed by the changer  144   b  (direction after change) is illustrated by the gray color line (line B). As illustrated in  FIG. 13 , line A (input side) and line B (output side) are in the same phase, and the amplitude of the output side is amplified and is greater than the amplitude on the input side. Therefore, it was found that when the direction changer  144  was used, the output amplitude was also amplified and was also greater than the input amplitude, and sufficient output amplitude was also obtained for MRE measurement. 
     Example 3 
     In the following, testing of MRE measurement will be explained. 
       FIG. 14  and  FIG. 15  are drawings illustrating the test results of MRE measurement. 
     The MRE measurement illustrated in  FIG. 14  and  FIG. 15  was performed using an exciter as described below and under the test conditions also described below. In this test, agarose gel was used instead of a living body  300 . 
     (1) Exciter 
     Model: C-5015 D-MASTER (Asahi Inc.) 
     Excitation source: Electro-dynamic 
     Excitation direction: Longitudinal 
     Frequency range: 1 to 500 Hertz (Hz) 
     Displacement: 0 to 15 (mm p-p) 
     Maximum load: 2 (kg) 
     Acceleration: 490 (m/s 2 ) 
     (2) Test Conditions 
     (Measured Object) 
     Material: Agarose gel (1.2% by weight, 50 mm×130 mm×40 mm) 
     Boundary condition: Base surface (fixed), other surfaces (free) 
     (Transmitter) 
     Material: GFRP 
     Length: 2 m 
     (Oscillatory Waves) 
     Wave pattern: Sine wave 
     Direction: Y direction (longitudinal direction) 
     Frequency: 62.5 Hz, 125 Hz, 250 Hz 
     Amplitude: 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm 
     (Micro MRI Apparatus) 
     Model: Compact MRI (MRTechnology, Inc.) 
     Magneto-static field: 0.3 Tesla 
     Magnet type: Permanent magnet 
     RF coil size: 125 mm×280 mm×65 mm (measurement zone) 
     Magnetic field homogeneity space: SR 50 mm 
     Gradient magnetic field: (G x , G y , G z )=(18, 18, 28) mT/m 
     (Magnetic Resonance Image) 
     Sequence: Spin echo 
     Image size: 128 pixels×256 pixels 
     Resolution: 1.2 (mm/pixel) 
     MSG timing: Phase difference with the vibration is 0, π/2, π, 3π/2 
     The relationship between the storage modulus of elasticity at each measurement point in MRE measurement, the average value of the values for the storage modulus of elasticity at all measurement points, and the variation in the storage modulus of elasticity at each measurement point is expressed by the following expression. 
     
       
         
           
             
               
                 
                   
                     
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     In  FIG. 14  and  FIG. 15 , u y  indicates displacement in the y direction.  FIG. 14  illustrates images when noise removal processing has not been performed, and  FIG. 15  illustrates images when noise removal processing has been performed. 
     In this example, the measured object is presumed to be a uniform object, so when the value of G is the same for all measurement points, the difference between the average values is zero, and G′ for all of the measurement points becomes 100%, so that in the images in  FIG. 14  and  FIG. 15 , there are only white areas. The G′ images in  FIG. 14  and  FIG. 15  illustrate that the larger the area of light color there is, the smaller the variation in data is, and the larger the area of dark color there is, the larger the variation in data becomes. Here, the less the variation in data is, the higher the precision of MRE measurement and greater the reliability becomes, so the precision of MRE measurement becomes higher and the reliability becomes greater at a frequencies and amplitudes that result in larger areas of light color. 
     From the distribution of light color areas in the G′ images at each condition in  FIG. 14  and  FIG. 15 , it was found that when the longitudinal vibration was controlled so that frequency was within the range 125 to 250 Hz, and the amplitude was within the range of 0.2 to 0.5 mm, variation in the data could be made even less. Therefore, from  FIG. 14  and  FIG. 15 , when the longitudinal vibration is controlled so that the frequency is 125 to 250 Hz and the amplitude is 0.2 to 0.5 mm, the test object is excited during MRE measurement with a sufficient excitation amplitude, the precision of MRE measurement becomes higher, or in other words, the reliability becomes greater, so that it is possible to obtain an image with the MRE image apparatus  400  without the need for special data processing by a computer, and to more easily obtain the elastic property of the living body  300 . 
     The present invention is not limited to the embodiments described above, and various modifications and applications are possible. 
     Part or all of the embodiments above and the examples above are described in the supplementary notes below, however, are not limited to the following. 
     (Supplementary Note 1) 
     An MRE Excitation apparatus that excites a test object during MRE measurement, comprises: 
     an excitation device that generates vibration; 
     a transmitter that is made using a non-magnetic material that, with one end-section being fastened to the excitation device and the other end-section connecting to the test object, extends along the direction of vibration from the excitation device and transmits longitudinal vibration from the excitation device to the test object; and 
     a support that is located between the one end-section and the other end-section of the transmitter, and that supports the transmitter; wherein 
     the primary natural frequency of the longitudinal vibration of the transmitter is outside the frequency band of the vibration from the excitation device. 
     (Supplementary Note 2) 
     The MRE excitation apparatus according to Supplementary note 1, wherein the transmitter is made using a non-metallic material. 
     (Supplementary Note 3) 
     The MRE excitation apparatus according to Supplementary note 1 or Supplementary note 2, wherein the transmitter is made using a GFRP material. 
     (Supplementary Note 4) 
     The MRE excitation apparatus according to any one of the Supplementary notes 1 to 3, wherein the support is made using a soft material, and has holder that holds the transmitter. 
     This application is based on Japanese Patent Application No. 2010-188514 filed on Aug. 25, 2010 and including specification, claims, drawings and summary. The disclosure of the above Japanese Patent Application No. 2010-188514 is incorporated herein by reference in its entirety. 
     REFERENCE SIGNS LIST 
     
         
         
           
               100  MRE excitation apparatus 
               110  Excitation device 
               120  Transmitter 
               121  End-section on the excitation device side 
               122  End-section on the test object side 
               123  Belt 
               130  Support 
               131  Column 
               131   a  Concave section 
               132  Holder 
               132   a  Curved surface 
               140  Transmitter 
               142  Transmitter on the test object side 
               144  Direction changer 
               144   a  Housing 
               144   b  Changer 
               146  Support 
               148  Hinge 
               150  MRE excitation apparatus 
               160  Controller 
               170  Memory 
               200  MRI apparatus 
               210  Gantry 
               220  Bed 
               300  Living body 
               400  MRE image apparatus