Abstract:
An MRI apparatus includes: an image display device for displaying diffusion emphatic images of respective axes corresponding to one slice; a designation operating device for allowing an operator to designate each diffusion emphatic image targeted for rephotograph from the displayed diffusion emphatic images of axes; a diffusion emphasis imaging device for rephotographing only the axis of each diffusion emphatic image designated by the operator; a diffusion emphatic image substituting device for substituting an original diffusion emphatic image with each diffusion emphatic image obtained at the diffusion emphatic photography; and a diffusion tensor image creating device for creating a diffusion tensor image from a set of the post-substitution diffusion emphatic images.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to an MRI (Magnetic Resonance Imaging) apparatus, and more particularly to an MRI apparatus capable of recreating a diffusion tensor image in a short period of time where an abnormal image exists. 
         [0002]    There has heretofore been known an MRI apparatus which obtains sets of diffusion emphatic images of six or more axes by photography or imaging and creates an intended diffusion tensor image from the sets of the diffusion emphatic images (refer to, for example, patent documents 1 and 2). 
         [0003]    Patent Document 1. Japanese Unexamined Patent Application Publication No. 2005-525208. 
         [0004]    Patent Document 2. Japanese Unexamined Patent Publication No. Hei 9(1997)-70397. 
         [0005]    When a diffusion tensor image is created from sets of diffusion emphatic images of nine axes, for example, imaging or photography free of application of an MPG (Motion Probing Gradient) is done once and the MPG is applied to the nine axes respectively, and their imaging is done to obtain the sets of diffusion emphatic images of the nine axes. Therefore, it is necessary to carry out photographs of 10 times (=1+9) as a whole. 
         [0006]    On the other hand, since the diffusion emphatic imaging or photography executed by application of the MPG is sensitive to motion, the diffusion emphatic image might be an improper abnormal image due to fine motion of a subject. A diffusion tensor image created from a set of diffusion emphatic images including the abnormal image might also be an improper abnormal image. 
         [0007]    In the conventional MRI apparatus, the diffusion emphatic imaging about all axes was redone even when the abnormal image occurred in one axis. That is, when the diffusion tensor image is created from the sets of the diffusion emphatic images of the nine axes as in the example referred to above, the diffusion tensor image has been recreated based on the diffusion emphatic images obtained by retrying ten photographs. 
         [0008]    Under such circumstances, however, a problem arises in that it results in a reduction in detection efficiency. 
       SUMMARY OF THE INVENTION 
       [0009]    It is desirable that a problem described previously is solved. 
         [0010]    In a first aspect, the invention provides an MRI apparatus including an image display device for displaying diffusion emphatic images of respective axes corresponding to one slice, a designation operating device for allowing an operator to designate each diffusion emphatic image targeted for rephotograph from the displayed diffusion emphatic images of axes, a diffusion emphasis imaging device for rephotographing only the axis of each diffusion emphatic image designated by the operator, a diffusion emphatic image substituting device for substituting an original diffusion emphatic image with each diffusion emphatic image obtained at the diffusion emphatic photography, and a diffusion tensor image creating device for creating a diffusion tensor image from a set of the post-substitution diffusion emphatic images. 
         [0011]    In the MRI apparatus according to the first aspect, when an abnormal image exists, only the axis of a diffusion emphatic image designated by the operator is rephotographed without retrying diffusion emphatic imaging about all axes. When an abnormal image occurs in one axis, for example, the diffusion emphatic imaging is retried only once only with respect to the one axis. That is, even when the abnormal image occurs in one axis as in the aforementioned example of the 9-axis diffusion emphatic imaging, such wastage that the ten photographs are retried, can be avoided, and hence detection efficiency can be improved. 
         [0012]    In a second aspect, the invention provides an MRI apparatus wherein in the MRI apparatus according to the first aspect, an abnormal image extracting device for extracting an abnormal image from the diffusion emphatic images of the respective axes corresponding to the one slice, and a warning device for notifying the presence of the abnormal image to the operator are provided. 
         [0013]    In the MRI apparatus according to the second aspect, when an abnormal image exists, the abnormal image is automatically extracted and the MRI apparatus warns the operator of its presence. It is therefore possible to reduce a burden on the operator. 
         [0014]    In a third aspect, the invention provides an MRI apparatus wherein in the MRI apparatus according to the second aspect, the abnormal image extracting device extracts an abnormal image on the basis of the average of pixel values of the diffusion emphatic images. 
         [0015]    In the MRI apparatus according to the third aspect, since the average of the pixel values of the diffusion emphatic images becomes a value away from a normal image in the case of the abnormal image, the abnormal image can be extracted based on it. 
         [0016]    In a fourth aspect, the invention provides an MRI apparatus wherein in the MRI apparatus according to any of the first through third aspects, an imaging condition storing device for storing imaging conditions for the diffusion emphatic images of the respective axes therein is provided and the diffusion emphasis imaging device reads an imaging condition for the diffusion emphatic image designated by the operator and performs rephotograph under the read imaging condition. 
         [0017]    In the MRI apparatus according to the fourth aspect, the diffusion emphatic imaging can be retried accurately and under the same imaging condition because the imaging conditions for the diffusion emphatic images of the respective axes are stored. It is possible to save the trouble of resetting the imaging condition. Hence a burden on the operator can be reduced. 
         [0018]    In a fifth aspect, the invention provides an MRI apparatus including an abnormal image extracting device for extracting an abnormal image from diffusion emphatic images of respective axes corresponding to one slice, a diffusion emphasis imaging device for rephotographing only the axis of each extracted diffusion emphatic image, a diffusion emphatic image substituting device for substituting an original diffusion emphatic image with each diffusion emphatic image obtained at the diffusion emphatic photography, and a diffusion tensor image creating device for creating a diffusion tensor image from a set of the post-substitution diffusion emphatic images. 
         [0019]    In the MRI apparatus according to the fifth aspect, when an abnormal image exists, only the axis of the abnormal image is rephotographed without retrying diffusion emphatic imaging about all axes. When an abnormal image occurs in one axis, for example, the diffusion emphatic imaging is retried only once only with respect to the one axis. That is, even when the abnormal image occurs in one axis as in the aforementioned example of the 9-axis diffusion emphatic imaging, such wastage that the ten photographs are retried, can be avoided, and hence detection efficiency can be improved. 
         [0020]    Further, since the abnormal image is automatically extracted and imaging thereof is redone, a burden on an operator can be reduced. 
         [0021]    In a sixth aspect, the invention provides an MRI apparatus wherein in the MRI apparatus according to the fifth aspect, the abnormal image extracting device extracts an abnormal image, based on the average of pixel values of the diffusion emphatic images. 
         [0022]    In the MRI apparatus according to the sixth aspect, since the average of the pixel values of the diffusion emphatic images becomes a value away from a normal image in the case of the abnormal image, the abnormal image can be extracted based on it. 
         [0023]    In a seventh aspect, the invention provides an MRI apparatus wherein in the MRI apparatus according to the fifth or sixth aspect, an imaging condition storing device for storing imaging conditions for the diffusion emphatic images of the respective axes therein is provided, and the diffusion emphasis imaging device reads an imaging condition for each extracted diffusion emphatic image and performs rephotograph under the read imaging condition. 
         [0024]    In the MRI apparatus according to the seventh aspect, the diffusion emphatic imaging can be retried accurately and under the same imaging condition because the imaging conditions for the diffusion emphatic images of the respective axes are stored. 
         [0025]    In an eighth aspect, the invention provides an MRI apparatus including selection operating device for allowing an operator to select a diffusion tensor image targeted for rephotograph from diffusion tensor images of one or more slices, an image display device for displaying diffusion emphatic images of respective axes corresponding to the diffusion tensor image selected by the operator, a designation operating device for allowing the operator to designate a diffusion emphatic image targeted for rephotograph from the displayed diffusion emphatic images of axes, diffusion emphasis imaging device for rephotographing only the axis of the diffusion emphatic image designated by the operator, a diffusion emphatic image substituting device for substituting an original diffusion emphatic image with each diffusion emphatic image obtained at the diffusion emphatic photography, a diffusion tensor image creating device for creating a diffusion tensor image from a set of the post-substitution diffusion emphatic images, and a diffusion tensor image substituting device for substituting an original diffusion tensor image with the created diffusion tensor image. 
         [0026]    In the MRI apparatus according to the eighth aspect, when an abnormal image exists, only the axis of the diffusion emphatic image designated by the operator is rephotographed without retrying diffusion emphatic imaging about all axes. When an abnormal image occurs in one axis, for example, the diffusion emphatic imaging is retried only once only with respect to the one axis. That is, even when the abnormal image occurs in one axis as in the aforementioned example of the 9-axis diffusion emphatic imaging, such wastage that the ten photographs are retried, can be avoided, and hence detection efficiency can be improved. 
         [0027]    In a ninth aspect, the invention provides an MRI apparatus wherein in the MRI apparatus according to the eighth aspect, an abnormal image extracting device for extracting an abnormal image from the diffusion tensor images of the one or more slices, and a warning device for notifying the presence of the abnormal image to the operator are provided. 
         [0028]    In the MRI apparatus according to the ninth aspect, when an abnormal image exists in the diffusion tensor images, the abnormal image is automatically extracted and the MRI apparatus warns the operator of its presence. It is therefore possible to reduce a burden on the operator. 
         [0029]    In a tenth aspect, the invention provides an MRI apparatus wherein in the MRI apparatus according to the ninth aspect, the abnormal image extracting device extracts an abnormal image on the basis of the average of pixel values of the diffusion tensor images. 
         [0030]    In the MRI apparatus according to the tenth aspect, since the average of the pixel values of the diffusion emphatic images becomes a value away from a normal image in the case of the abnormal image, the abnormal image can be extracted based on it. 
         [0031]    In an eleventh aspect, the invention provides an MRI apparatus wherein in the MRI apparatus according to either of the ninth and tenth aspects, an abnormal image extracting device for extracting an abnormal image from the diffusion emphatic images of the respective axes corresponding to the diffusion tensor image selected by the operator, and a warning device for notifying the presence of the extracted diffusion emphatic image to the operator are provided. 
         [0032]    In the MRI apparatus according to the eleventh aspect, when an abnormal image exists in the diffusion tensor images of the respective axes, the abnormal image is automatically extracted and the MRI apparatus warns the operator of its presence. It is therefore possible to reduce a burden on the operator. 
         [0033]    In a twelfth aspect, the invention provides an MRI apparatus wherein in the MRI apparatus according to the eleventh aspect, the abnormal image extracting device extracts an abnormal image, based on the average of pixel values of the diffusion emphatic images. 
         [0034]    In the MRI apparatus according to the twelfth aspect, since the average of the pixel values of the diffusion emphatic images becomes a value away from a normal image in the case of the abnormal image, the abnormal image can be extracted based on it. 
         [0035]    In a thirteenth aspect, the invention provides an MRI apparatus wherein in the MRI apparatus according to any of the eighth through twelfth aspects, an imaging condition storing device for storing imaging conditions for the diffusion emphatic images of the respective axes therein is provided, and the diffusion emphasis imaging device reads an imaging condition for the diffusion emphatic image designated by the operator and performs rephotograph under the read imaging condition. 
         [0036]    In the MRI apparatus according to the thirteenth aspect, the diffusion emphatic imaging can be retried accurately and under the same imaging condition because the imaging conditions for the diffusion emphatic images of the respective axes are stored. It is possible to save the trouble of resetting the imaging condition. Hence a burden on the operator can be reduced. 
         [0037]    In a fourteenth aspect, the invention provides an MRI apparatus including a selection operating device for allowing an operator to select a diffusion tensor image targeted for rephotograph from diffusion tensor images of one or more slices, an abnormal image extracting device for extracting an abnormal image from diffusion emphatic images of respective axes corresponding to the diffusion tensor image selected by the operator, a diffusion emphasis imaging device for rephotographing only the axis of the extracted diffusion emphatic image, a diffusion emphatic image substituting device for substituting an original diffusion emphatic image with each diffusion emphatic image obtained at the diffusion emphatic photography, a diffusion tensor image creating device for creating a diffusion tensor image from a set of the post-substitution diffusion emphatic images, and a diffusion tensor image substituting device for substituting an original diffusion tensor image with the created diffusion tensor image. 
         [0038]    In the MRI apparatus according to the fourteenth aspect, when an abnormal image exists, only the axis of the diffusion emphatic image designated by the operator is rephotographed without retrying diffusion emphatic imaging about all axes. When an abnormal image occurs in one axis, for example, the diffusion emphatic imaging is retried only once only with respect to the one axis. That is, even when the abnormal image occurs in one axis as in the aforementioned example of the 9-axis diffusion emphatic imaging, such wastage that the ten photographs are retried, can be avoided, and hence detection efficiency can be improved. 
         [0039]    If the operator selects a diffusion tensor image targeted for rephotography, then an abnormal image is automatically extracted and rephotographed. It is therefore possible to reduce a burden on the operator. 
         [0040]    In a fifteenth aspect, the invention provides an MRI apparatus wherein in the MRI apparatus according to the fourteenth aspect, the abnormal image extracting device extracts an abnormal image, based on the average of pixel values of the diffusion emphatic images. 
         [0041]    In the MRI apparatus according to the fifteenth aspect, since the average of the pixel values of the diffusion emphatic images becomes a value away from a normal image in the case of the abnormal image, the abnormal image can be extracted based on it. 
         [0042]    In a sixteenth aspect, the invention provides an MRI apparatus wherein in the MRI apparatus according to the fourteenth or fifteenth aspect, an imaging condition storing device for storing imaging conditions for the diffusion emphatic images of the respective axes therein is provided, and the diffusion emphasis imaging device reads an imaging condition for each extracted diffusion emphatic image and performs rephotograph under the read imaging condition. 
         [0043]    In the MRI apparatus according to the sixteenth aspect, the diffusion emphatic imaging can be retried accurately and under the same imaging condition because the imaging conditions for the diffusion emphatic images of the respective axes are stored. It is possible to save the trouble of resetting the imaging condition. Hence a burden on the operator can be reduced. 
         [0044]    In a seventeenth aspect, the invention provides an MRI apparatus including an abnormal image extracting device for extracting an abnormal image from diffusion tensor images of one or more slices and extracting an abnormal image from diffusion emphatic images of respective axes corresponding to the extracted abnormal image, a diffusion emphasis imaging device for rephotographing only the axis of the extracted diffusion emphatic image, a diffusion emphatic image substituting device for substituting an original diffusion emphatic image with each diffusion emphatic image obtained at the diffusion emphatic photography, a diffusion tensor image creating device for creating a diffusion tensor image from a set of the post-substitution diffusion emphatic images, and a diffusion tensor image substituting device for substituting an original diffusion tensor image with the created diffusion tensor image. 
         [0045]    In the MRI apparatus according to the seventeenth aspect, when an abnormal image exists, only the axis of the abnormal image is rephotographed without retrying diffusion emphatic imaging about all axes. When an abnormal image occurs in one axis, for example, the diffusion emphatic imaging is retried only once only with respect to the one axis. That is, even when the abnormal image occurs in one axis as in the aforementioned example of the 9-axis diffusion emphatic imaging, such wastage that the ten photographs are retried, can be avoided, and hence detection efficiency can be improved. 
         [0046]    Further, since the abnormal image is automatically extracted and imaging thereof is retried, a burden on an operator can be reduced. 
         [0047]    In an eighteenth aspect, the invention provides an MRI apparatus wherein in the MRI apparatus according to the seventeenth aspect, the abnormal image extracting device extracts an abnormal image, based on the averages of pixel values of both the diffusion tensor images and the diffusion emphatic images. 
         [0048]    In the MRI apparatus according to the eighteenth aspect, since the averages of the pixel values of both the diffusion tensor images and the diffusion emphatic images become a value away from a normal image in the case of the abnormal image, the abnormal image can be extracted based on it. 
         [0049]    In a nineteenth aspect, the invention provides an MRI apparatus wherein in the MRI apparatus according to the seventeenth or eighteenth aspect, an imaging condition storing device for storing imaging conditions for the diffusion emphatic images of the respective axes therein is provided, and the diffusion emphasis imaging device reads an imaging condition for each extracted diffusion emphatic image and performs rephotograph under the read imaging condition. 
         [0050]    In the MRI apparatus according to the nineteenth aspect, the diffusion emphatic imaging can be retried accurately and under the same imaging condition because the imaging conditions for the diffusion emphatic images of the respective axes are stored. It is possible to save the trouble of resetting the imaging condition. Hence a burden on the operator can be reduced. 
         [0051]    According to the MRI apparatus of the invention, when an abnormal image exists, only the axis of the abnormal image is rephotographed without retrying diffusion emphatic imaging about all axes. It is therefore possible to retry the diffusion emphatic imaging in a short period of time and recreate a diffusion tensor image. Thus, detection efficiency can be enhanced. 
         [0052]    The MRI apparatus of the invention is available for diffusion emphatic imaging and diffusion tensor imaging. 
         [0053]    Further objects and advantages of the present invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0054]      FIG. 1  is a block diagram showing a function configuration of an MRI apparatus according to a first embodiment. 
           [0055]      FIG. 2  is a flowchart illustrating a diffusion emphatic imaging process according to the first embodiment. 
           [0056]      FIG. 3  is a flowchart following  FIG. 2 . 
           [0057]      FIG. 4  is a flowchart following  FIG. 3 . 
           [0058]      FIG. 5  is a flowchart following  FIG. 3 . 
           [0059]      FIG. 6  is a diagram illustrative of a display screen of diffusion tensor images. 
           [0060]      FIG. 7  is a diagram illustrative of a display screen of diffusion emphatic images. 
           [0061]      FIG. 8  is a diagram illustrative of a display screen of diffusion tensor images 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0062]    The invention will be explained below in more detail in accordance with an embodiment illustrated in the drawings. Incidentally, the invention is not limited to or by it. 
       First Embodiment 
       [0063]      FIG. 1  is a block diagram showing a function configuration of an MRI apparatus  100  according to a first embodiment. 
         [0064]    In the present MRI apparatus  100 , a magnet assembly  1  has a spatial portion (bore) for inserting a subject thereinside, and is equipped with an X-axis gradient coil  1 X for forming an X-axis gradient magnetic field, a Y-axis gradient coil  1 Y for forming a Y-axis gradient magnetic field, a Z-axis gradient coil  1 Z for forming a Z-axis gradient magnetic field, a transmitting coil  1 T for applying each RF pulse for exciting the spin of a nucleus in the subject, a receiving coil  1 R for detecting an NMR signal from the subject, and a permanent magnet pair  1 M for forming a static magnetic field, so as to surround the spatial portion. 
         [0065]    A superconducting magnet may be used in place of the permanent magnet pair  1 M. 
         [0066]    The X-axis gradient coil  1 X is connected to an X-axis gradient coil driving circuit  3 X. The Y-axis gradient coil  1 Y is connected to a Y-axis gradient coil driving circuit  3 Y. The Z-axis gradient coil  1 Z is connected to a Z-axis gradient coil driving circuit  3 Z. The transmitting coil  1 T is connected to an RF power amplifier  4 . 
         [0067]    The X-axis gradient coil driving circuit  3 X includes an X-axis gradient amplifier. The Y-axis gradient coil driving circuit  3 Y includes a Y-axis gradient amplifier. The Z-axis gradient coil driving circuit  3 Z includes a Z-axis gradient amplifier. The RF power amplifier  4  includes an RF amplifier. 
         [0068]    A sequence storage circuit  8  controls or operates the gradient coil driving circuits  3 X,  3 Y and  3 Z, based on a pulse sequence stored therein in accordance with a command issued from a computer  7  to thereby generate gradient magnetic fields from the gradient coils  1 X,  1 Y and  1 Z. Along with it, the sequence storage circuit  8  operates a gate modulator  9  to modulate a carrier output signal produced from an RF oscillator  10  to a pulsated signal represented in the form of a predetermined timing/predetermined envelope/predetermined phase and adds it to the RF power amplifier  4  as an RF pulse, where it is power-amplified. Thereafter, the RF power amplifier  4  applies the same to the transmitting coil  1 T. 
         [0069]    The receiving coil  1 R is connected to a pre-amplifier  5 . 
         [0070]    The pre-amplifier  5  amplifies the NMR signal from the subject, which is received by the receiving coil  1 R and inputs the same to a phase comparator  12 . The phase comparator  12  phase-detects the NMR signal sent from the pre-amplifier  5  in response to a reference signal outputted from the RF oscillator  10  and applies it to an AD converter  11 . The AD converter  11  converts the post-phased detection analog signal to digital data and inputs it to the computer  7 . 
         [0071]    The computer  7  takes charge of the whole control such as the reception of information inputted from an operation console  13 . Along with it, the computer  7  reads the digital data from the AD converter  11  and performs arithmetic processing thereon to generate an image and causes a display unit  6  to display the image and a message thereon. 
         [0072]    The computer  7  includes a CPU and a memory therein. 
         [0073]      FIG. 2  is a flowchart illustrating a procedure for a diffusion emphatic imaging process by the MRI apparatus  100 . At Step W 1 , an axis counter is initialized to a=0. 
         [0074]    At Step W 2 , a slice counter is initialized to s=1. 
         [0075]    At Step W 3 , diffusion emphatic imaging for a sth slice is effected on an ath axis. However, photography or imaging free of application of an MPG is carried out upon diffusion emphatic imaging about a 0th axis. 
         [0076]    At Steps W 4  and W 5 , Step W 3  is repeated from a first slice to an S(≧1)th slice. 
         [0077]    At Steps W 6  and W 7 , Steps W 2  to W 5  are repeated from the 0th axis to an A(≧6)th axis. 
         [0078]    At Step W 8 , the slice counter is initialized to s=1. 
         [0079]    At Step W 9 , an Ath diffusion emphatic image is created from a 0th diffusion emphatic image for the sth slice and stored together with imaging conditions corresponding to the respective diffusion emphatic images. Since, however, the 0th diffusion emphatic image is subjected to the imaging free of MPG application, it is not a diffusion emphatic image in fact. Thus, an imaging condition corresponding to the  0 th diffusion emphatic image may not be stored. 
         [0080]    At Step W 10 , a diffusion tensor image for the sth slice is created from the 0th diffusion emphatic image for the sth slice, based on the Ath diffusion emphatic image and stored. 
         [0081]    At Steps W 11  and W 12 , Steps W 9  and W 10  are repeated from the first slice to the Sth slice. Then, the procedure proceeds to Step W 21  of  FIG. 3 . 
         [0082]    At Step W 21  of  FIG. 3 , an abnormal image is extracted from the diffusion tensor images from the first slice to the Sth slice. This extracting method calculates, for example, the average of pixel values of the respective diffusion tensor images and determines or regards the image as the abnormal image if it is beyond a predetermined allowable range. 
         [0083]    At Step W 22 , the diffusion tensor images from the first slice to the Sth slice and a message are displayed. A display screen at the time that abnormal images are extracted is illustrated by way of example in  FIG. 6 . 
         [0084]    In the example of  FIG. 6 , frames are applied to the abnormal images alone and displayed as being distinguishable from others, and a message indicative of such a case is displayed. Further, buttons for “full-auto”, “semi-auto”, “respective-axes display” and “end” are displayed. When it is desired to leave all to the apparatus and rephotograph, an operator clicks the “full-auto” to select one diffusion tensor image manually. Thereafter, when it is desired to leave to the apparatus that after manual selection of one diffusion tensor image, abnormal images are extracted from diffusion emphatic images that become the basis for the diffusion tensor image and rephotograph thereof is done, the operator manually selects one diffusion tensor image and thereafter clicks the “semi-auto”. When it is desired to display a diffusion emphatic image that becomes the basis for one diffusion tensor image after the manual selection of the one diffusion tensor image, the operator manually selects one diffusion tensor image and thereafter clicks the “respective-axes display”. When it is desired to end or terminate the processing, the operator clicks the “end”. 
         [0085]    When the “full-auto” is clicked on the display screen shown in  FIG. 6  at Step W 23 , the procedure proceeds to Step W 31  of  FIG. 4 . If not so, then the procedure proceeds to Step W 24 . 
         [0086]    When one diffusion tensor image is selected and the “semi-auto” is clicked at Step W 24  on the display screen shown in  FIG. 6 , the procedure proceeds to Step W 32  of  FIG. 4 . If not so, then the procedure proceeds to Step W 25 . 
         [0087]    When one diffusion tensor image is selected and the “respective-axes display” is clicked on the display screen shown in  FIG. 6  at Step W 25 , the procedure proceeds to Step W 51  of  FIG. 5 . If not so, then the procedure proceeds to Step W 26 . 
         [0088]    When the “end” is clicked on the display screen shown in  FIG. 6  at Step W 26 , the processing is terminated. If not so, then the procedure returns to Step W 23 . 
         [0089]    At Step W 31  of  FIG. 4 , each abnormal image is extracted from the first diffusion emphatic image to the Ath diffusion emphatic image, which becomes the basis for each abnormal diffusion tensor image. This extracting method calculates, for example, the average of pixel values of respective diffusion emphatic images and determines the image as the abnormal image if it is beyond the predetermined allowable range. Then, the procedure proceeds to Step W 33 . 
         [0090]    At Step W 32  of  FIG. 4 , each abnormal image is extracted from the first diffusion emphatic image to the Ath diffusion emphatic image, which becomes the basis for each selected diffusion tensor image. This extracting method calculates, for example, the average of pixel values of respective diffusion emphatic images and determines the image as the abnormal image if it is beyond the predetermined allowable range. Then, the procedure proceeds to Step W 33 . 
         [0091]    At Step W 33 , one of abnormal images is selected and an imaging condition therefor is read. 
         [0092]    At Step W 34 , it is confirmed whether rephotograph is done according to the read imaging condition. If it is found that the rephotograph has been done, then the procedure proceeds to Step W 41 . If not so, then the procedure proceeds to Step W 35 . 
         [0093]    At Step W 35 , an imaging condition is recorded and the procedure proceeds to Step W 36 . 
         [0094]    At Step W 36 , the slice counter is initialized to s=1. 
         [0095]    At Step W 37 , diffusion emphatic imaging for an sth slice is carried out according to the read imaging condition (including axial information). That is, the rephotograph for the sth slice is effected on the axis of an abnormal image. 
         [0096]    At Step W 38 , a diffusion emphatic image for the sth slice about the axis of the abnormal image is created from data obtained by rephotograph, and the original diffusion emphatic image is substituted therewith. 
         [0097]    At Steps W 39  and W 40 , Steps W 37  and W 38  are repeated from a first slice to an S(≧1)th slice. 
         [0098]    At Step W 41 , Steps W 33  through W 40  are repeated with respect to all abnormal images. 
         [0099]    At Step W 42 , the slice counter is initialized to s=1. 
         [0100]    At Step W 43 , a diffusion tensor image for the sth slice is created based on the  0 th emphatic image to Ath diffusion emphatic image for the sth slice and then stored. 
         [0101]    At Steps W 44  and W 45 , Step W 43  is repeated from the first slice to the Sth slice. Then, the procedure returns to Step W 21  of  FIG. 3 . 
         [0102]    At Step W 51  of  FIG. 5 , each abnormal image is extracted from the first diffusion emphatic image to the Ath diffusion emphatic image, which becomes the basis for the selected diffusion tensor image. This extracting method calculates, for example, the average of pixel values of respective diffusion emphatic images and determines the image as the abnormal image if it is beyond the predetermined allowable range. 
         [0103]    At Step W 52 , the first diffusion emphatic image to the Ath diffusion emphatic image that becomes the basis for the selected diffusion tensor image, and a message are displayed. A display screen at the time that abnormal images are extracted is illustrated by way of example in  FIG. 7 . 
         [0104]    In the example of  FIG. 7 , frames are applied to the abnormal images alone and displayed as being distinguishable from others. Further, buttons for “auto”, “rephotograph”, and “return” are displayed. When it is desired to leave all to the apparatus and rephotograph, an operator clicks the “auto” to designate one or more diffusion emphatic images manually. Thereafter, when it is desired to rephotograph the axes of the one or more diffusion emphatic images, the operator clicks the “rephotograph” after having designated the one or more diffusion emphatic images manually. When it is desired to return to the display of the diffusion tensor image, the operator clicks the “return”. 
         [0105]    At Step W 53 , the procedure proceeds to Step W 33  of  FIG. 4  when the “auto” is clicked on the display screen shown in  FIG. 7 . If not so, then the procedure proceeds to Step W 54 . 
         [0106]    At Step W 54 , when one or more diffusion emphatic images are selected and the “rephotograph” is clicked on the display screen shown in  FIG. 7 , the procedure proceeds to Step W 56 . If not so, then the procedure proceeds to Step W 55 . 
         [0107]    At Step W 55 , the procedure returns to Step W 21  of  FIG. 3  when the “return” is clicked on the display screen shown in  FIG. 7 . If not so, then the procedure returns to Step W 53 . 
         [0108]    At Step  56 , the designated diffusion emphatic image is assumed to be an abnormal image, and the procedure proceeds to Step W 33  of  FIG. 4 . 
         [0109]    When it is found at Step W 21  of  FIG. 3  that no abnormal image is extracted, such a display screen as shown in  FIG. 8  is shown at Step W 22 . 
         [0110]    In the example shown in  FIG. 8 , a message free of detection of an abnormal image is displayed. Further, buttons for “semi-auto”, “respective-axes display” and “end” are displayed. When it is desired to leave to the apparatus that after one diffusion tensor image has been selected manually, an abnormal image is extracted from diffusion emphatic images that become the basis for the one diffusion tensor image and rephotograph is effected thereon, the operator clicks the “semi-auto” after the manual selection of the one diffusion tensor image. When it is desired to display the diffusion emphatic images that become the basis for the one diffusion tensor image after the manual selection of the one diffusion tensor image, the operator clicks the “respective-axes display” after the manual selection of the one diffusion tensor image. When it is desired to terminate the processing, the operator clicks the “end”. 
         [0111]    According to the MRI apparatus  100  of the first embodiment, when an abnormal image is found, only the axis of the corresponding abnormal image is rephotographed without redoing diffusion emphatic imaging about all axes. Therefore, the diffusion emphatic imaging can be redone in a short period of time. It is thus possible to improve detection efficiency. 
       Second Embodiment 
       [0112]    In the first embodiment, the recreation of the diffusion emphatic image about the rephotographed axis at Step W 38  and the substitution thereof with the original diffusion emphatic image have been performed with respect to all slices. On the other hand, however, whether the original diffusion emphatic image for the corresponding slice contains an abnormal image or a designated image is determined and the corresponding diffusion emphatic image may be replaced only with respect to each slice having contained it. 
         [0113]    Further, while the recreation of the diffusion tensor image at Step W 43  and the substitution thereof with the original diffusion tensor image have been performed with respect to all slices, whether the diffusion tensor image for the corresponding slice is an abnormal image or a selected image is determined and the corresponding diffusion tensor image may be created and replaced only in such a case. 
         [0114]    Upon replacement of the created diffusion emphatic image+diffusion tensor image, the original image and a newly-created image are displayed and the execution of its replacement may be decided manually. 
         [0115]    Many widely different embodiments of the present invention may be configured without departing from the spirit and the scope of the present invention. It should be understood that the present invention is not limited to the specific embodiments described in the specification, except as defined in the appended claims.