Patent Publication Number: US-2016235335-A1

Title: Magnetic resonance imaging (mri) apparatus and method of controlling mri apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from Korean Patent Application No. 10-2015-0024310, filed on Feb. 17, 2015, and Korean Patent Application No. 10-2015-0181099, filed on Dec. 17, 2015, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein by reference in their entireties. 
     BACKGROUND 
     1. Field 
     Apparatuses and methods consistent with exemplary embodiments relate to magnetic resonance imaging (MRI) apparatuses and methods of controlling an MRI apparatus. 
     2. Description of the Related Art 
     An MRI apparatus uses a magnetic field to capture an image of a target object, and is widely used in the accurate diagnosis of diseases because it shows stereoscopic images of bones, lumbar discs, joints, nerve ligaments, etc. at angles. 
     The MRI apparatus is configured to acquire MR signals and reconstruct the acquired MR signals into an image to be output. The MRI apparatus uses different pulse sequences according to MR images to be obtained. 
     To obtain an MR image, a target object is used to enter a confined space and undergo scanning for more than several minutes. However, it may be difficult for the target object to remain stationary for a few minutes during the scanning process. Movement of the target object during the scanning process may make it difficult to obtain high quality images. 
     SUMMARY 
     Exemplary embodiments may address at least the above problems and/or disadvantages and other disadvantages not described above. Also, the exemplary embodiments are not required to overcome the disadvantages described above, and may not overcome any of the problems described above. 
     One or more exemplary embodiments provide magnetic resonance imaging (MRI) apparatuses and methods of controlling an MRI apparatus, whereby high quality MR images may be obtained by minimizing motion of a target object during scanning. 
     According to an aspect of an exemplary embodiment, there is provided an MRI apparatus including a signal transceiver configured to transmit a radio frequency (RF) signal to an object, and receive a magnetic resonance (MR) signal from the object. The MRI apparatus further includes a controller configured to control the signal transceiver based on sequence information that is used according to an imaging protocol, determine a degree at which the object is able to move based on the sequence information, to generate operation information, and control a device connected to the MRI apparatus to provide the operation information. 
     The controller may be further configured to determine information of whether the object is able to move based on a time interval. 
     The device may include a display configured to display the operation information to the object as an image. 
     The controller may be further configured to control the display to display the operation information to the object during a time interval when the object is able to move. 
     The controller may be further configured to control the display to display an image for inducing a concentration of the object while the signal transceiver is receiving MR signals of a low frequency region in a k-space, and display an image for helping the object relax while the signal transceiver is receiving MR signals of a high frequency region in the k-space. 
     The controller may be further configured to control the display to display an image showing a level of progress of an examination of the object based on the operation information. 
     The image may include at least one among a progress bar and a text message. 
     The image may distinguish a first time interval when the object is to remain stationary from a second time interval when the object is able to move. 
     The MRI apparatus may further include a bore in which the object is disposed, and the display may include a first display disposed in the bore, a second display disposed outside the bore, a first projector disposed in the bore, and a second projector disposed outside the bore. 
     The MRI apparatus may further include a bore in which the object is disposed, and an immobilizer disposed in the bore, and configured to immobilize motion of the object. The controller may be further configured to control the immobilizer based on the sequence information. 
     The controller may be further configured to control the immobilizer to immobilize a part of the object to be measured based on the sequence information. 
     The controller may be further configured to control the immobilizer to immobilize a part of the object to be measured during a time interval when the object is to remain stationary. 
     The sequence information may include a strength and an application timing of a pulse signal for generating a gradient magnetic field around the object. 
     According to an aspect of another exemplary embodiment, there is provided a method of controlling a magnetic resonance imaging (MRI) apparatus, the method including transmitting a radio frequency (RF) signal to an object, and receiving a magnetic resonance (MR) signal from the object, based on sequence information that is used according to an imaging protocol. The method further includes determining a degree at which the object is able to move based on the sequence information, to generate operation information, and providing the operation information. 
     The determining may include determining information of whether the object is able to move based on a time interval. 
     The providing may include displaying the operation information to the object as an image. 
     The providing may include displaying the operation information to the object during a time interval when the object is able to move. 
     The providing may include displaying an image for inducing a concentration of the object while the signal transceiver is receiving MR signals of a low frequency region in a k-space, and displaying an image for helping the object relax while the signal transceiver is receiving MR signals of a high frequency region in the k-space. 
     The providing may include displaying an image showing a level of progress of an examination of the object based on the operation information. 
     The image may include at least one among a progress bar and a text message. 
     The image may distinguish a first time interval when the object is to remain stationary from a second time interval when the object is able to move. 
     The method may further include immobilizing motion of the object based on the sequence information. 
     The immobilizing may include immobilizing a part of the object to be measured based on the sequence information. 
     The immobilizing may include immobilizing a part of the object to be measured during a time interval when the object is to remain stationary. 
     The sequence information may include a strength and an application timing of a pulse signal for generating a gradient magnetic field around the object. 
     According to an aspect of another exemplary embodiment, there is provided a magnetic resonance imaging (MRI) apparatus including a signal transceiver configured to transmit a radio frequency (RF) signal to an object, and receive a magnetic resonance (MR) signal from the object. The MRI apparatus further includes a controller configured to control the signal transceiver based on sequence information that is used according to an imaging protocol, and determine a degree at which the object is able to move based on the sequence information, to generate the operation information. The MRI apparatus further includes a display configured to display an image to the object based on the operation information. 
     The controller may be further configured to control the display to display an image for inducing a concentration of the object based on the operation information. 
     The controller may be further configured to control the display to display an image showing a level of progress of an examination of the object based on the operation information. 
     According to an aspect of another exemplary embodiment, there is provided a method of controlling a magnetic resonance imaging (MRI) apparatus, the method including transmitting a radio frequency (RF) signal to an object, and receiving a magnetic resonance (MR) signal from the object, based on sequence information that is used according to an imaging protocol, determining a degree at which the object is able to move based on the sequence information, to generate the operation information, and displaying an image to the object based on the operation information. 
     The displaying may include displaying an image for inducing a concentration of the object based on the operation information. 
     The displaying may include displaying an image showing a level of progress of an examination of the object based on the operation information. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and/or other aspects will be more apparent by describing exemplary embodiments with reference to the accompanying drawings, in which: 
         FIG. 1  is a block diagram of a magnetic resonance imaging (MRI) apparatus according to an exemplary embodiment; 
         FIG. 2  is a flowchart of a method of controlling an MRI apparatus according to an exemplary embodiment; 
         FIG. 3  is a block diagram of an MRI apparatus according to another exemplary embodiment; 
         FIG. 4  is a flowchart of a method of controlling an MRI apparatus according to another exemplary embodiment; 
         FIGS. 5A and 5B  are diagrams for explaining a method of controlling an MRI apparatus according to an exemplary embodiment; 
         FIGS. 6A, 6B, 6C, 6D, and 6E  are images provided to a target object via a display of an MRI apparatus, according to an exemplary embodiment; 
         FIG. 7  is a flowchart of a method of controlling an MRI apparatus according to another exemplary embodiment; 
         FIGS. 8A and 8B  are images provided to a target object via a display of an MRI apparatus, according to another exemplary embodiment; 
         FIG. 9  is a block diagram of an MRI apparatus according to another exemplary embodiment; 
         FIG. 10  is a flowchart of a method of controlling an MRI apparatus according to another exemplary embodiment; 
         FIGS. 11A and 11B  are perspective views of immobilizers in an MRI apparatus according to exemplary embodiments; 
         FIG. 12  is a schematic diagram of an MRI system; and 
         FIG. 13  illustrates a configuration of a communication unit according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Exemplary embodiments are described in greater detail below with reference to the accompanying drawings. 
     In the following description, like drawing reference numerals are used for like elements, even in different drawings. The matters defined in the description, such as detailed construction and elements, are provided to assist in a comprehensive understanding of the exemplary embodiments. However, it is apparent that the exemplary embodiments can be practiced without those specifically defined matters. Also, well-known functions or constructions may not be described in detail because they would obscure the description with unnecessary detail. 
     It will be understood that the terms “comprises” and/or “comprising” used herein specify the presence of stated features or components, but do not preclude the presence or addition of one or more other features or components. In addition, the terms such as “unit,” “-er (-or),” and “module” described in the specification refer to an element for performing at least one function or operation, and may be implemented in hardware, software, or the combination of hardware and software. 
     In the present specification, an “image” may refer to multi-dimensional data composed of discrete image elements (e.g., pixels in a two-dimensional (2D) image and voxels in a three-dimensional (3D) image). For example, the image may be a medical image of an object captured by an X-ray apparatus, a computed tomography (CT) apparatus, a magnetic resonance imaging (MRI) apparatus, an ultrasound diagnosis apparatus, or another medical imaging apparatus. 
     Furthermore, in the present specification, an “object” may be a human, an animal, or a part of a human or animal. For example, the object may be an organ (e.g., the liver, the heart, the womb, the brain, a breast, or the abdomen), a blood vessel, or a combination thereof. Furthermore, the “object” may be a phantom. The phantom means a material having a density, an effective atomic number, and a volume that are approximately the same as those of an organism. For example, the phantom may be a spherical phantom having properties similar to the human body. 
     Furthermore, in the present specification, a “user” may be, but is not limited to, a medical expert, such as a medical doctor, a nurse, a medical laboratory technologist, or a technician who repairs a medical apparatus. 
     Furthermore, in the present specification, an “MR image” refers to an image of an object obtained by using the nuclear magnetic resonance principle. 
     Furthermore, in the present specification, a “pulse sequence” refers to continuity of signals repeatedly applied by an MRI apparatus. The pulse sequence may include a time parameter of a radio frequency (RF) pulse, for example, repetition time (TR) or echo time (TE). 
     Furthermore, in the present specification, a “pulse sequence schematic diagram” shows an order of events that occur in an MRI apparatus. For example, the pulse sequence schematic diagram may be a diagram showing an RF pulse, a gradient magnetic field, an MR signal, or the like according to time. 
     An MRI system is an apparatus for acquiring a sectional image of a part of an object by expressing, in a contrast comparison, a strength of a MR signal with respect to an RF signal generated in a magnetic field having a strength. For example, if an RF signal that only resonates an atomic nucleus (for example, a hydrogen atomic nucleus) is emitted for an instant toward the object placed in a strong magnetic field and then such emission stops, an MR signal is emitted from the atomic nucleus, and thus the MRI system may receive the MR signal and acquire an MR image. The MR signal denotes an RF signal emitted from the object. An intensity of the MR signal may be determined according to a density of a predetermined atom (for example, hydrogen) of the object, a relaxation time T 1 , a relaxation time T 2 , and a flow of blood or the like. 
     MRI systems include characteristics different from those of other imaging apparatuses. Unlike imaging apparatuses such as CT apparatuses that acquire images according to a direction of detection hardware, MRI systems may acquire 2D images or 3D volume images that are oriented toward an optional point. MRI systems do not expose objects or examiners to radiation, unlike CT apparatuses, X-ray apparatuses, position emission tomography (PET) apparatuses, and single photon emission CT (SPECT) apparatuses, may acquire images having high soft tissue contrast, and may acquire neurological images, intravascular images, musculoskeletal images, and oncologic images that are used to precisely capturing abnormal tissues. 
       FIG. 1  is a block diagram of an MRI apparatus  100  according to an exemplary embodiment. 
     Referring to  FIG. 1 , the MRI apparatus  100  according to an exemplary embodiment includes a gantry  120 , a signal transceiver  130 , and a controller  150 . 
     The gantry  120  blocks electromagnetic waves generated by a main magnet, a gradient coil, and an RF coil from being externally emitted. A magnetostatic field and a gradient magnetic field are formed at a bore in the gantry  120 , and an RF signal is irradiated toward a target object. 
     The gantry  120  may further include displays respectively mounted outside and inside the gantry  120 . The gantry  120  may provide predetermined information to the user or the target object via the displays respectively disposed outside and inside the gantry  120 . For example, the display disposed outside the gantry  120  may be configured to provide an image to the user via a mirror attached to a head coil. 
     The gantry  120  may further include in-bore and out-bore projectors respectively located inside and outside the bore. For example, the in-bore projector may be designed to shield against magnetic fields. The out-bore projector may project an image onto an inner wall of the bore, e.g., via a mirror disposed on a table. 
     The controller  150  may control the gantry  120  and devices installed on the gantry  120 . For example, the controller  150  may control displays mounted to the gantry  120 . 
     In detail, the controller  150  may control displays respectively disposed outside and inside the gantry  120 . The controller  150  may control an on/off status of the displays, screens to be output to the displays, etc., via a display controller. 
     The controller  150  may control an RF signal transceiver according to a predetermined sequence. In detail, the controller  150  may control the signal transceiver  130  according to a predetermined sequence. In this case, the pulse sequence may include all pieces of information for controlling a gradient amplifier, an RF transmitter, an RF receiver, and a transmission/reception switch, such as a strength, an application time, and application timing of a pulse signal applied to a gradient coil. 
     The signal transceiver  130  may transmit an RF signal and receive an MR signal. The signal transceiver  130  may control a gradient magnetic field formed inside the gantry  120 , i.e., in the bore, according to a predetermined MR sequence, and control transmission and reception of an RF signal and an MR signal. 
     The signal transceiver  130  may be controlled by the controller  150  to transmit an RF signal to and receive an MR signal from a target object within the gantry  120 . Information about control operation may be input to the controller  150 , and the controller  150  may receive the information to control devices (e.g., displays and other mechanical devices) installed on the gantry  120 . 
     According to one or more exemplary embodiments, the controller  150  may include a plurality of components having different functions. For example, the controller  150  may include a gantry controller for controlling the gantry  120  and a sequence controller for controlling the signal transceiver  130 . 
     According to an exemplary embodiment, the controller  150  may control devices mounted on the gantry  120  to provide operation information to the target object according to sequence information. 
     In the present specification, operation information may include information for distinguishing a time interval during which motion of a target object may significantly affect the quality of an MR image from a time interval during which motion of the target object may not significantly affect the quality of the MR image. The operation information may further include not only visual information such as images and auditory information such as audio but also an operation of a mechanical device. For example, the operation information may include information about movement of an immobilizer as described below. 
     For example, the controller  150  may control displays or other various devices mounted on a table. Furthermore, the displays or other various devices mounted on the table may supply operation information to the target object or help prevent movement of the target object. 
     Furthermore, the displays or the other various devices may provide a time interval during which the target object is able to move. In the present specification, the time interval when the target is able to move may mean a time interval when motion of the target object does not greatly affect MR image quality. For example, the time interval during which the target object is able to move may be a time interval during which data corresponding to high frequencies in a k-space is acquired. 
       FIG. 2  is a flowchart of a method of controlling the MRI apparatus  100  according to an exemplary embodiment. 
     Referring to  FIG. 2 , in operation S 110 , the MRI apparatus  100  transmits an RF signal to and receives an MR signal from a target object according to a sequence. 
     In operation S 130 , the MRI apparatus  100  provides operation information to the target object based on the signal transmission and reception. For example, the MRI apparatus  100  may provide operation information to the target object based on a pulse sequence. In detail, a display of the MRI apparatus  100  may provide the target object with an image based on the operation information. 
     For example, the MRI apparatus  100  may provide operation information via a displayed image during a time interval when an object (e.g., the target object) has to remain stationary. The operation information may be provided simultaneously to an operator and the target object. 
     Thus, the target object may receive the operation information and make a conscious effort not to move, and the MRI apparatus  100  may obtain a high quality image by scanning the motionless object. 
     For example, while the signal transceiver  130  is receiving MR signals corresponding to a low frequency region in a k-space, a display may provide an image that may induce a concentration of the target object. Various images may be used to induce a concentration of the target object. Furthermore, the image may be selected based on user modeling information of the target object. In this case, the target object may remain motionless by concentrating on the image, and the MRI apparatus  100  may obtain a high quality image by scanning a motionless object. 
     Furthermore, the display may provide the target object with an image showing a level of progress of an examination based on an operation of the controller  150 . For example, the display may provide an operation of a pulse sequence via at least one of a progress bar and text information. As another example, the display may display a progress bar in such a manner as to distinguish a time interval when the target object has to remain stationary from another time interval. Thus, the target object may make a conscious effort not to move based on an image showing a level of progress of an examination (e.g., a progress bar), and the MRI apparatus  100  may obtain a high quality image by scanning a motionless object. 
     Furthermore, the gantry  120  may include therein an immobilizer configured to prevent movement of the target object based on signal transmission and reception. For example, the immobilizer may immobilize a part of the target object being measured, based on signal transmission and reception. 
     For example, if the MRI apparatus  100  captures an image of a target object&#39;s head, the immobilizer may immobilize the head based on signal transmission and reception. If the MRI apparatus  100  captures an image of the target object&#39;s heart, the immobilizer may immobilize a target object&#39;s chest based on signal transmission and reception. 
     Thus, the MRI apparatus  100  may provide operation information to the target object based on signal transmission and reception, so that the target object may recognize an imaging situation and make a conscious effort to minimize movement, and the MRI apparatus  100  may obtain a high quality image by scanning a motionless target object. 
       FIG. 3  is a block diagram of an MRI apparatus  100   a  according to another exemplary embodiment. 
     Referring to  FIG. 3 , the MRI apparatus  100   a  according to another exemplary embodiment includes gantry  120 , the signal transceiver  130 , and the controller  150 . Furthermore, the gantry  120  includes a display  121 . 
     The controller  150  and the signal transceiver  130  shown in  FIG. 3  may operate in a similar way to their counterparts described with reference to  FIG. 1 . 
     The signal transceiver  130  may be controlled by the controller  150  to transmit an RF signal to and receive an MR signal from a target object within the gantry  120 . Information about control operation may be input to the controller  150 , and the controller  150  may receive the information to control the display  121 . 
     The display  121  may include an in-bore display, an out-bore display, an in-bore projector, and an out-bore projector. For example, the out-bore display may be installed to provide a user with an image via a mirror attached to a head coil. For example, the in-bore projector may operate in a manner that shields against magnetic fields. The out-bore projector may project an image onto an inner wall of the bore, e.g., via a mirror disposed on a table. 
     The gantry  120  may further include displays disposed outside and inside the gantry  120 . The MRI apparatus  100   a  may provide predetermined information to the user or target object via the displays disposed outside and inside the gantry  120 . 
     The controller  150  may control the gantry  120  and the display  121  installed in the gantry  120 . The controller  150  may control the on/off status of the displays, screens to be output to the displays, etc., via a display controller. 
     An operation of the display  121  will now be described in detail with reference to  FIGS. 4 through 8B . 
       FIG. 4  is a flowchart for explaining a method of controlling the MRI apparatus  100   a  according to another exemplary embodiment. 
     Referring to  FIG. 4 , in operation S 110 , the MRI apparatus  100   a  transmits an RF signal to and receives an MR signal from a target object according to a sequence. 
     In operation S 131 , the MRI apparatus  100   a  provides operation information to the target object based on the signal transmission and reception. For example, while the signal transceiver  130  is receiving an MR signal for a low frequency region in a k-space, the display  121  provides an image for inducing a concentration or an attention of the target object. According to another exemplary embodiment, the display  121  may provide an image simultaneously to an operator or target object. 
       FIGS. 5A and 5B  are diagrams for explaining a method of controlling the MRI apparatus  100   a  according to an exemplary embodiment.  FIGS. 6A, 6B, 6C ,  6 D, and  6 E are images provided to a target object via the display  121  of the MRI apparatus  100   a , according to an exemplary embodiment. 
     Referring to  FIGS. 3 and 5A , the controller  150  may receive MR signals corresponding to different frequency regions according to time intervals via the signal transceiver  130 . For example, as shown in  FIG. 5A , the controller  150  may receive an MR signal for a high frequency region during a first time interval (e.g., an interval corresponding to a lapse of about 30 seconds after the start of a scan), an MR signal corresponding to a low frequency region during a second time interval (e.g., an interval corresponding to a lapse of about 1 minute after the start of the scan), and, again, an MR signal corresponding to the high frequency region during a third time interval (e. g., an interval corresponding to a lapse of about 30 minutes after the start of the scan). 
     In addition, because the quality of an MR image is influenced by a signal for a low frequency region more than by a signal for a high frequency region, motion of a target object during the second time interval may significantly degrade the quality of an MR image. 
     Thus, as shown in  FIG. 5B , the display  121  may provide a first image IM_ 1  that may help the target object relax during the first time interval, a second image IM_ 2  that induces a concentration of the target object during the second time interval, and a third image IM_ 3  that may help the target object relax during the third time interval. 
     However, images provided by the display  121  are not limited to the first through third images IM_ 1  through IM_ 3  shown in  FIG. 5B  and include other various images. For example, various types of images shown in  FIGS. 6A through 6E  may be used to attract the target object&#39;s concentration. 
     Furthermore, images provided by the display  121  may be determined based on information about the target object. For example, the first through third images IM_ 1  through IM_ 3  may be determined based on the age, gender, occupation, etc., of the target object. Furthermore, the display  121  may display an image for inducing a concentration of the target object regardless of information about the target object. 
       FIG. 7  is a flowchart of a method of controlling the MRI apparatus  100   a  according to another exemplary embodiment. 
     Referring to  FIG. 7 , in operation S 110 , the MRI apparatus  100   a  transmits an RF signal to and receives an MR signal from a target object according to a sequence. 
     In operation S 132 , the display  121  provides operation information to the target object via an image (e.g., a progress bar or text message) showing a level of progress of an examination based on the signal transmission and reception. 
     For example, the display  121  may display a progress bar by which the target object or an operator may recognize the operation information during or a few seconds before a time interval when the target object is able to move. 
     Furthermore, the display  121  may provide operation information to the target object by using text together with a progress bar. 
       FIGS. 8A and 8B  are images provided to a target object via the display  121  of the MRI apparatus  100   a , according to another exemplary embodiment. 
     Referring to  FIG. 8A , the display  210  may display a progress bar together with text &lt;Please Relax&gt; during a first time interval, display a progress bar together with text &lt;Please Stay Still&gt; during a second time interval, and display a progress bar together with text &lt;Almost complete&gt; during a third time interval. 
     According to an exemplary embodiment, a shape, a form, and a color of the progress bar as well as content, a font, and a size of text do not limit the scope of the exemplary embodiments. Furthermore, the time intervals may be classified in various ways. 
     Furthermore, referring to  FIG. 8B , the MRI apparatus  100   a  may transmit an RF signal based on a sequence used according to an imaging protocol and receive an MR signal from a target object. The display  121  may provide information about whether the target object is able to move by using a progress bar. In detail, the progress bar may indicate information about first through third protocol photographing intervals P_ 1  through P_ 3 . Furthermore, the progress bar may indicate information about first through third rest intervals R_ 1  through R_ 3 , each being interposed between consecutive protocol photographing intervals. The progress bar may provide the target object with information about a current level t x  of progress of examination. 
     By using the progress bar, the display  120  may provide to the target object, in the form of text, information indicating that the target object is not allowed to move during the first through third photographing intervals P_ 1  through P_ 3  and information indicating that the target object is allowed to move during the rest intervals R_ 1  through R_ 3 . For example, the progress bar may indicate information in the form of text “Not Allowed to Move” during the first through third protocol photographing intervals P_ 1  through P_ 3  and indicate information in the form of text “Allowed to Move” during the rest intervals R_ 1  through R_ 3 . However, the method of providing information via the progress bar is not limited thereto, and the progress bar may indicate the information in other forms such as by using voice or sound. 
       FIG. 9  is a block diagram of an MRI apparatus  100   b  according to another exemplary embodiment. 
     Referring to  FIG. 9 , the MRI apparatus  100   b  according to another exemplary embodiment includes the gantry  120 , the signal transceiver  130 , and the controller  150 . Furthermore, the gantry  120  includes an immobilizer  123 . 
     The controller  150  and the signal transceiver  130  may operate in a similar way to their counterparts described with reference to  FIG. 1 . 
     The gantry  120  may immobilize a target object via the immobilizer  123  according to a time interval. Thus, the MRI apparatus  100   b  may obtain a high quality image by immobilizing the target object directly during a time interval. In other words, the MRI apparatus  100   b  may minimize motion of the target object by preventing movement of the target object via the immobilizer  123  during a time interval that is highly related to image quality. 
     The controller  150  may control the gantry  120  and the immobilizer  123  mounted to the gantry  120 . In detail, the controller  150  may control an operation of the immobilizer  123  via a table controller. 
     For example, the controller  150  may control the immobilizer  123  to prevent movement of a target object&#39;s head during a first time interval so that motion of the target object&#39;s head is minimized. Furthermore, the controller  150  may control the immobilizer  123  to prevent movement of a target object&#39;s torso during a second time interval so that motion of the target object&#39;s torso is minimized. 
     According to an exemplary embodiment, the controller  150  may control the immobilizer  123  to immobilize the target object according to sequence information. 
     The signal transceiver  130  may be controlled by the controller  150  to transmit an RF signal to and receive an MR signal from the target object within the gantry  120 . Information about control operation may be input to the controller  150 , and the controller  150  may receive the information to control the immobilizer  123 . 
     An operation of the immobilizer will now be described in more detail with reference to  FIGS. 10, 11A, and 11B . 
       FIG. 10  is a flowchart of a method of controlling the MRI apparatus  100   b  according to another exemplary embodiment. 
     Referring to  FIG. 10 , in operation S 110 , the MRI apparatus  100  transmits an RF signal to and receives an MR signal from a target object according to a sequence. In operation S 130 , the MRI apparatus  100  provides operation information to the target object based on the signal transmission and reception. 
     In operation S 150 , the MRI apparatus  100  may prevent or immobilize, via the immobilizer  123 , motion of the target object based on the signal transmission and reception. According to another exemplary embodiment, the MRI apparatus  100  may prevent motion of the target object, via the immobilizer  123 , by skipping operation S 130 , i.e., without providing the operation information. 
       FIGS. 11A and 11B  are perspective views of immobilizers in the MRI apparatus  100   b  according to exemplary embodiments. For example, the immobilizer  123  may be shaped as shown in  FIG. 11A , so that it may be pulled down from a top side to a bottom side of a head to immobilize the head. As another example, the immobilizer  123  may be shaped as shown in  FIG. 11B  to immobilize the head securely from left and right sides thereof. 
       FIG. 12  is a block diagram of an MRI system. Referring to  FIG. 1 , the MRI system includes a gantry  20 , a signal transceiver  30 , a monitor  40 , a system controller  50 , and an operator  60 . 
     The gantry  20  prevents external emission of electromagnetic waves generated by a main magnet  22 , a gradient coil  24 , and an RF coil  26 . A magnetostatic field and a gradient magnetic field are formed in a bore in the gantry  20 , and an RF signal is emitted toward an object  10 . 
     The main magnet  22 , the gradient coil  24 , and the RF coil  26  may be arranged in a predetermined direction of the gantry  20 . The predetermined direction may be a coaxial cylinder direction. The object  10  is disposed on a table  28  that is capable of being inserted into a cylinder along a horizontal axis of the cylinder. 
     The main magnet  22  generates a magnetostatic field or a static magnetic field for aligning magnetic dipole moments of atomic nuclei of the object  10  in a constant direction. A precise and accurate MR image of the object  10  may be obtained due to a magnetic field generated by the main magnet  22  being strong and uniform. 
     The gradient coil  24  includes X, Y, and Z coils for generating gradient magnetic fields in X-, Y-, and Z-axis directions crossing each other at right angles. The gradient coil  24  may provide location information of each region of the object  10  by differently inducing resonance frequencies according to the regions of the object  10 . 
     The RF coil  26  may emit an RF signal toward a patient and receive an MR signal emitted from the patient. In detail, the RF coil  26  may transmit, toward atomic nuclei included in the patient and having precessional motion, an RF signal having the same frequency as that of the precessional motion, stop transmitting the RF signal, and then receive an MR signal emitted from the atomic nuclei included in the patient. 
     For example, to transit an atomic nucleus from a low energy state to a high energy state, the RF coil  26  may generate and apply an electromagnetic wave signal that is an RF signal corresponding to a type of the atomic nucleus, to the object  10 . When the electromagnetic wave signal generated by the RF coil  26  is applied to the atomic nucleus, the atomic nucleus may transit from the low energy state to the high energy state. Then, when electromagnetic waves generated by the RF coil  26  disappear, the atomic nucleus to which the electromagnetic waves were applied transits from the high energy state to the low energy state, thereby emitting electromagnetic waves having a Lamor frequency. In other words, when the applying of the electromagnetic wave signal to the atomic nucleus is stopped, an energy level of the atomic nucleus is changed from a high energy level to a low energy level, and thus the atomic nucleus may emit electromagnetic waves having a Lamor frequency. The RF coil  26  may receive electromagnetic wave signals from atomic nuclei included in the object  10 . 
     The RF coil  26  may be realized as one RF transmitting and receiving coil having both a function of generating electromagnetic waves each having an RF that corresponds to a type of an atomic nucleus and a function of receiving electromagnetic waves emitted from an atomic nucleus. Alternatively, the RF coil  26  may be realized as a transmission RF coil having a function of generating electromagnetic waves each having an RF that corresponds to a type of an atomic nucleus, and a reception RF coil having a function of receiving electromagnetic waves emitted from an atomic nucleus. 
     The RF coil  26  may be fixed to the gantry  20  or may be detachable. When the RF coil  26  is detachable, the RF coil  26  may be an RF coil for a part of the object, such as a head RF coil, a chest RF coil, a leg RF coil, a neck RF coil, a shoulder RF coil, a wrist RF coil, or an ankle RF coil. 
     The RF coil  26  may communicate with an external apparatus via wires and/or wirelessly, and may also perform dual tune communication according to a communication frequency band. 
     The RF coil  26  may be a birdcage coil, a surface coil, or a transverse electromagnetic (TEM) coil according to structures. 
     The RF coil  26  may be a transmission exclusive coil, a reception exclusive coil, or a transmission and reception coil according to methods of transmitting and receiving an RF signal. 
     The RF coil  26  may be an RF coil having various numbers of channels, such as 16 channels, 32 channels, 72 channels, and 144 channels. 
     The gantry  20  further includes a display  29  disposed outside the gantry  20 , and may further include a display disposed inside the gantry  20 . The gantry  20  may provide predetermined information to the user or the object  10  through the display  29  and the display respectively disposed outside and inside the gantry  20 . 
     The signal transceiver  30  may control the gradient magnetic field formed inside the gantry  20 , i.e., in the bore, according to a predetermined MR sequence, and control transmission and reception of an RF signal and an MR signal. 
     The signal transceiver  30  includes a gradient amplifier  32 , a transmission and reception switch  34 , an RF transmitter  36 , and an RF receiver  38 . 
     The gradient amplifier  32  drives the gradient coil  24  included in the gantry  20 , and may supply a pulse signal for generating a gradient magnetic field to the gradient coil  24  under the control of a gradient magnetic field controller  54 . By controlling the pulse signal supplied from the gradient amplifier  32  to the gradient coil  24 , gradient magnetic fields in X-, Y-, and Z-axis directions may be synthesized. 
     The RF transmitter  36  and the RF receiver  38  may drive the RF coil  26 . The RF transmitter  36  may supply an RF pulse in a Lamor frequency to the RF coil  26 , and the RF receiver  38  may receive an MR signal received by the RF coil  26 . 
     The transmission and reception switch  34  may adjust transmitting and receiving directions of the RF signal and the MR signal. For example, the transmission and reception switch  34  may emit the RF signal toward the object  10  through the RF coil  26  during a transmission mode, and receive the MR signal from the object  10  through the RF coil  26  during a reception mode. The transmission and reception switch  34  may be controlled by a control signal output by an RF controller  56 . 
     The monitor  40  may monitor or control the gantry  20  or devices mounted on the gantry  20 . The monitor  40  includes a system monitor  42 , an object monitor  44 , a table controller  46 , and a display controller  48 . 
     The system monitor  42  may monitor and control a state of the magnetostatic field, a state of the gradient magnetic field, a state of the RF signal, a state of the RF coil  26 , a state of the table  28 , a state of a device measuring body information of the object  10 , a power supply state, a state of a thermal exchanger, and a state of a compressor. 
     The object monitor  44  monitors a state of the object  10 . In detail, the object monitor  44  may include a camera for observing a movement or position of the object  10 , a respiration measurer for measuring the respiration of the object  10 , an electrocardiogram (ECG) measurer for measuring the electrical activity of the object  10 , or a temperature measurer for measuring a temperature of the object  10 . 
     The table controller  46  controls a movement of the table  28  where the object  10  is positioned. The table controller  46  may control the movement of the table  28  according to a sequence control of a sequence controller  50 . For example, during moving imaging of the object  10 , the table controller  46  may continuously or discontinuously move the table  28  according to the sequence control of the sequence controller  50 , and thus the object  10  may be photographed in a field of view (FOV) larger than that of the gantry  20 . 
     In an exemplary embodiment, the table controller  46  may operate according to control by the gantry controller  58 . The table controller  46  may control the immobilizer  123  according to a sequence of operations of the controller  150 . Thus, a high quality image may be obtained by directly preventing motion of the target object. 
     The display controller  48  controls the display  29  disposed outside the gantry  20  and the display disposed inside the gantry  20 . In detail, the display controller  48  may control the display  29  and the display to be on or off, and may control a screen image to be output on the display  29  and the display. Also, when a speaker is located inside or outside the gantry  20 , the display controller  48  may control the speaker to be on or off, or may control sound to be output via the speaker. 
     In an exemplary embodiment, the display controller  48  may operate according to control by the gantry controller  58 . The display controller  48  may display  121  according to a sequence of operations of the controller  150 . Thus, the target object may view an image and make a conscious effort to not move, and thus, a high quality image may be obtained. 
     The system controller  50  includes a sequence controller  52  for controlling a sequence of signals formed in the gantry  20 , and a gantry controller  58  for controlling the gantry  20  and the devices mounted on the gantry  20 . 
     The sequence controller  52  includes the gradient magnetic field controller  54  for controlling the gradient amplifier  32 , and the RF controller  56  for controlling the RF transmitter  36 , the RF receiver  38 , and the transmission and reception switch  34 . The sequence controller  52  may control the gradient amplifier  32 , the RF transmitter  36 , the RF receiver  38 , and the transmission and reception switch  34  according to a pulse sequence received from the operator  60 . The pulse sequence includes all information used to control the gradient amplifier  32 , the RF transmitter  36 , the RF receiver  38 , and the transmission and reception switch  34 . For example, the pulse sequence may include information about a strength, an application time, and application timing of a pulse signal applied to the gradient coil  24 . 
     The operator  60  may request the system controller  50  to transmit pulse sequence information while controlling an overall operation of the MRI system. 
     The operator  60  includes an image processor  62  for receiving and processing the MR signal received by the RF receiver  38 , an output interface  64 , and an input interface  66 . 
     The image processor  62  may process the MR signal received from the RF receiver  38  to generate MR image data of the object  10 . 
     The image processor  62  receives the MR signal received by the RF receiver  38  and performs any one of various signal processes, such as amplification, frequency transformation, phase detection, low frequency amplification, and filtering, on the received MR signal. 
     The image processor  62  may arrange digital data in a k space (for example, also referred to as a Fourier space or a frequency space) of a memory, and rearrange the digital data into image data via 2D or 3D Fourier transformation. 
     The image processor  62  may perform a composition process or difference calculation process on the image data. The composition process may include an addition process on a pixel or a maximum intensity projection (MIP) process. The image processor  62  may store not only the rearranged image data but also image data on which a composition process or a difference calculation process is performed, in a memory or an external server. 
     The image processor  62  may perform any of the signal processes on the MR signal in parallel. For example, the image processor  62  may perform a signal process on a plurality of MR signals received by a multi-channel RF coil in parallel to rearrange the plurality of MR signals into image data. 
     The output interface  64  may output image data generated or rearranged by the image processor  62  to the user. The output interface  64  may also output information used for the user to manipulate the MRI system, such as a user interface (UI), user information, or object information. The output interface  64  may be a speaker, a printer, a cathode-ray tube (CRT) display, a liquid crystal display (LCD), a plasma display panel (PDP), an organic light-emitting device (OLED) display, a field emission display (FED), a light-emitting diode (LED) display, a vacuum fluorescent display (VFD), a digital light processing (DLP) display, a flat panel display (FPD), a 3D display, a transparent display, or any one of other various output devices. 
     The user may input object information, parameter information, a scan condition, a pulse sequence, or information about image composition or difference calculation by using the input interface  66 . The input interface  66  may be a keyboard, a mouse, a track ball, a voice recognizer, a gesture recognizer, a touch screen, or any one of other various input devices. 
     The signal transceiver  30 , the monitor  40 , the system controller  50 , and the operator  60  are separate components in  FIG. 12 , but respective functions of the signal transceiver  30 , the monitor  40 , the system controller  50 , and the operator  60  may be performed by another component. For example, the image processor  62  converts the MR signal received from the RF receiver  38  into a digital signal in  FIG. 12 , but alternatively, the conversion of the MR signal into the digital signal may be performed by the RF receiver  38  or the RF coil  26 . 
     The gantry  20 , the RF coil  26 , the signal transceiver  30 , the monitor  40 , the system controller  50 , and the operator  60  may be connected to each other by wire or wirelessly, and when they are connected wirelessly, the MRI system may further include an apparatus for synchronizing clock signals therebetween. Communication between the gantry  20 , the RF coil  26 , the signal transceiver  30 , the monitor  40 , the system controller  50 , and the operator  60  may be performed by using a high-speed digital interface, such as low voltage differential signaling (LVDS), asynchronous serial communication, such as a universal asynchronous receiver transmitter (UART), a low-delay network protocol, such as error synchronous serial communication or a controller area network (CAN), optical communication, or any of other various communication methods. 
       FIG. 13  is a block diagram of a communication interface  70  according to an exemplary embodiment. Referring to  FIG. 13 , the communication interface  70  may be connected to at least one selected from the gantry  20 , the signal transceiver  30 , the monitor  40 , the system controller  50 , and the operator  60  of  FIG. 12 . 
     The communication interface  70  may transmit and receive data to and from a hospital server or another medical apparatus in a hospital, which is connected through a picture archiving and communication system (PACS), and perform data communication according to the digital imaging and communications in medicine (DICOM) standard. 
     As shown in  FIG. 13 , the communication interface  70  may be connected to a network  80  by wire or wirelessly to communicate with a server  92 , a medical apparatus  94 , or a portable device  96 . 
     In detail, the communication interface  70  may transmit and receive data related to the diagnosis of an object through the network  80 , and may also transmit and receive a medical image captured by the medical apparatus  94 , such as a CT apparatus, an MRI apparatus, or an X-ray apparatus. In addition, the communication interface  70  may receive a diagnosis history or a treatment schedule of the object from the server  92  and use the same to diagnose the object. The communication interface  70  may perform data communication not only with the server  92  or the medical apparatus  94  in a hospital, but also with the portable device  96 , such as a mobile phone, a personal digital assistant (PDA), or a laptop of a doctor or patient. 
     Also, the communication interface  70  may transmit information about a malfunction of the MRI system or about a medical image quality to a user through the network  80 , and receive a feedback regarding the information from the user. 
     The communication interface  70  may include at least one component enabling communication with an external apparatus. 
     For example, the communication interface  70  includes a local area communication interface  72 , a wired communication interface  74 , and a wireless communication interface  76 . The local area communication interface  72  refers to an interface for performing local area communication with an apparatus within a predetermined distance. Examples of local area communication technology according to an exemplary embodiment include, but are not limited to, a wireless local area network (LAN), Wi-Fi, Bluetooth, ZigBee, Wi-Fi direct (WFD), ultra wideband (UWB), infrared data association (IrDA), Bluetooth low energy (BLE), and near field communication (NFC). 
     The wired communication interface  74  refers to an interface for performing communication by using an electric signal or an optical signal. Examples of wired communication technology according to an exemplary embodiment include wired communication techniques using a pair cable, a coaxial cable, and an optical fiber cable, and other wired communication techniques. 
     The wireless communication interface  76  transmits and receives a wireless signal to and from at least one selected from a base station, an external apparatus, and a server in a mobile communication network. The wireless signal may be a voice call signal, a video call signal, or data in any one of various formats according to transmission and reception of a text/multimedia message. 
     In addition, the exemplary embodiments may also be implemented through computer-readable code and/or instructions on a medium, e.g., a computer-readable medium, to control at least one processing element to implement any above-described embodiments. The medium may correspond to any medium or media that may serve as a storage and/or perform transmission of the computer-readable code. 
     The computer-readable code may be recorded and/or transferred on a medium in a variety of ways, and examples of the medium include recording media, such as magnetic storage media (e.g., ROM, floppy disks, hard disks, etc.) and optical recording media (e.g., compact disc read only memories (CD-ROMs) or digital versatile discs (DVDs)), and transmission media such as Internet transmission media. Thus, the medium may have a structure suitable for storing or carrying a signal or information, such as a device carrying a bitstream according to one or more exemplary embodiments. The medium may also be on a distributed network, so that the computer-readable code is stored and/or transferred on the medium and executed in a distributed fashion. Furthermore, the processing element may include a processor or a computer processor, and the processing element may be distributed and/or included in a single device. 
     The foregoing exemplary embodiments are examples and are not to be construed as limiting. The present teaching can be readily applied to other types of apparatuses. Also, the description of the exemplary embodiments is intended to be illustrative, and not to limit the scope of the claims, and many alternatives, modifications, and variations will be apparent to those skilled in the art.