Patent Publication Number: US-11041945-B2

Title: Ultrasonic diagnostic apparatus and method for controlling ultrasonic probe to transmit a plurality of plane wave sets at a plurality of steering angles so that a grating lobe is outside a region of interest

Description:
TECHNICAL FIELD 
     The present disclosure relates to ultrasound diagnosis apparatuses, ultrasound probes, and methods of controlling the ultrasound probes, and more particularly, to ultrasound diagnosis apparatuses, ultrasound probes, and methods of controlling the ultrasound probes, which may improve the quality of ultrasound images. 
     BACKGROUND ART 
     Ultrasound diagnosis apparatuses transmit ultrasound signals generated by transducers of a probe to an object and receive echo signals reflected from the object, thereby obtaining at least one image of an internal part of the object (e.g., soft tissues or blood flow). In particular, ultrasound diagnosis apparatuses are used for medical purposes including observation of the interior of an object, detection of foreign substances, and diagnosis of damage to the object. Such ultrasound diagnosis apparatuses provide high stability, display images in real time, and are safe due to the lack of radioactive exposure, compared to X-ray apparatuses. Therefore, ultrasound diagnosis apparatuses are widely used together with other image diagnosis apparatuses including a computed tomography (CT) apparatus, a magnetic resonance imaging (MRI) apparatus, and the like. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Technical Solution 
     According to an aspect of an exemplary embodiment, an ultrasound diagnosis apparatus includes a probe configured to transmit a plurality of plane waves at a plurality of steering angles and a controller configured to determine the plurality of plane waves so that a grating lobe of a synthetic transmit focusing beam pattern using the plurality of plane waves is located outside a region of interest. 
     Advantageous Effects of the Invention 
     Provided are ultrasound diagnosis apparatuses, ultrasound probes, and methods of controlling the ultrasound probes which may improve the quality of ultrasound images. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view for explaining an ultrasound diagnosis apparatus according to some exemplary embodiments. 
         FIG. 2  is a block diagram showing a configuration of the ultrasound apparatus according to some exemplary embodiments. 
         FIG. 3  is a view of a plurality of plane waves transmitted by a probe, according to some exemplary embodiments. 
         FIG. 4  is a view for explaining a synthetic transmit focusing beam pattern at one point in a region of interest (ROI), according to some exemplary embodiments. 
         FIG. 5  is a graph showing a plane wave angle function according to some exemplary embodiments. 
         FIG. 6  is a graph showing a synthetic transmit focusing beam pattern according to some exemplary embodiments. 
         FIGS. 7A and 7B  are graphs showing a synthetic transmit focusing beam pattern according to a plane wave angle function for explaining a relationship between a position of a grating lobe and a steering angle, according to some exemplary embodiments. 
         FIGS. 8A and 8B  are graphs showing a synthetic transmit focusing beam pattern according to a plane wave angle function for explaining a relationship between a position of a grating lobe and a size of an ROI, according to some exemplary embodiments. 
         FIGS. 9A and 9B  are views of probes having apertures with different sizes, according to some exemplary embodiments. 
         FIGS. 10A and 10B  are views illustrating a case where a size of an aperture of a probe is adjusted by using a plurality of transducers included in the probe, according to some exemplary embodiments. 
         FIGS. 11A through 11C  are graphs showing a case where a plurality of plane wave sets, in which intervals between sine values of a plurality of steering angles are different from one another, are used, according to some exemplary embodiments. 
         FIGS. 12A and 12B  are graphs showing a case where a plurality of plane wave sets, in which intervals between sine values of a plurality of steering angles are different from one another, are used, according to other exemplary embodiments. 
         FIG. 13  is a graph showing a case where a plane wave angle function is formed by using sine values of arbitrary steering angles, according to some exemplary embodiments. 
         FIGS. 14A and 14B  are graphs showing a case where a plurality of plane wave sets, in which intervals between steering angles are different from one another, are used, according to some exemplary embodiments. 
         FIGS. 15A and 15B  are graphs showing a Hanning window and a rectangular window, according to some exemplary embodiments. 
         FIGS. 16A and 16B  are views illustrating a simulation result for explaining an effect of a synthetic transmit focusing beam pattern in which a grating lobe is located outside an ROI, according to a first exemplary embodiment. 
         FIGS. 17A through 18B  are views illustrating simulation results for explaining an effect of a synthetic transmit focusing beam pattern when a plane wave combination is used so that a size of a grating lobe is less than a size of a main lobe, according to a second exemplary embodiment. 
         FIGS. 19A and 19B  are views of an ultrasound image according to some exemplary embodiments. 
         FIGS. 20A and 20B  are views of an ultrasound image according to comparative examples. 
         FIG. 21  is a view for explaining an ultrasound probe according to some exemplary embodiments. 
         FIG. 22  is a block diagram showing a configuration of the ultrasound probe according to some exemplary embodiments. 
         FIG. 23  is a block diagram showing a configuration of an ultrasound diagnosis apparatus according to some exemplary embodiments. 
         FIG. 24  is a block diagram showing a configuration of a wireless probe according to some exemplary embodiments. 
         FIG. 25  is a flowchart of a method of controlling an ultrasound probe, according to some exemplary embodiments. 
     
    
    
     BEST MODE 
     According to an aspect of an exemplary embodiment, an ultrasound diagnosis apparatus includes: a probe configured to transmit a plurality of plane waves at a plurality of steering angles; and a controller configured to determine the plurality of plane waves so that a grating lobe of a synthetic transmit focusing beam pattern using the plurality of plane waves is located outside a region of interest. 
     The controller may determine the plurality of plane waves so that an interval between sine values of the plurality of steering angles is equal to or less than a first reference value. 
     The controller may set a value obtained by dividing a wavelength by a size of an aperture of the probe as the first reference value. 
     The controller may fix a minimum steering angle and a maximum steering angle, and may determine the plurality of plane waves so that a number of the plurality of steering angles is equal to or greater than a second reference value. 
     The controller may adjust a size of the region of interest so that the size of the region of interest is less than a position of the grating lobe. 
     The probe may receive echo signals, and the controller may apply an apodization window having a low side lobe to the echo signals. 
     The controller may determine the plurality of plane waves so that an intensity of a grating lobe is less than an intensity of a main lobe in the synthetic transmit focusing beam pattern using the plurality of plane waves. 
     The plurality of plane waves determined by the controller may include a plurality of plane wave sets, and grating lobes of the plurality of plane wave sets do not overlap one another. 
     The plurality of plane waves determined by the controller may include a plurality of plane wave sets, and intervals between sine values of the plurality of steering angles of the plurality of plane wave sets are different from one another. 
     The plurality of plane waves determined by the controller may include a plurality of plane wave sets, minimum steering angles and maximum steering angles of the plurality of plane wave sets are the same, and numbers of the steering angles of the plurality of plane wave sets are different from one another. 
     The plurality of steering angles of the plurality of plane waves determined by the controller may be arbitrary. 
     The plurality of plane waves determined by the controller may include a plurality of plane wave sets, and intervals of the plurality of steering angles of the plurality of plane wave sets may be different from one another. 
     The probe may receive echo signals, and the controller may apply an apodization window having a low side lobe to the echo signals. 
     The controller may determine the plurality of plane waves so that the grating lobe is located outside a region of interest. 
     According to an aspect of another exemplary embodiment, an ultrasound probe includes: an ultrasound transceiver configured to transmit a plurality of plane waves at a plurality of steering angles; and a controller configured to control the ultrasound transceiver so that a grating lobe of a synthetic transmit focusing beam pattern using the plurality of plane waves is located outside a region of interest. 
     The ultrasound transceiver may receive echo signals, and the controller may apply an apodization window having a low side lobe to the echo signals. 
     According to an aspect of another exemplary embodiment, an ultrasound probe includes: an ultrasound transceiver configured to transmit a plurality of plane waves at a plurality of steering angles; and a controller configured to determine the plurality of plane waves so that an intensity of a size of a grating lobe is less than an intensity of a main lobe in a synthetic transmit focusing beam pattern using the plurality of plane waves and to control the ultrasound transceiver to transmit the determined plurality of plane waves. 
     According to an aspect of another exemplary embodiment, a method of controlling an ultrasound probe includes: determining a plurality of plane waves so that a grating lobe of a synthetic transmit focusing beam pattern using the plurality of plane waves to be transmitted by the ultrasound probe at a plurality of steering angles is located outside a region of interest; and transmitting, by the ultrasound probe, the determined plurality of plane waves. 
     According to an aspect of another exemplary embodiment, a method of controlling an ultrasound probe includes: determining a plurality of plane waves so that an intensity of a grating lobe is less than an intensity of a main lobe in a synthetic transmit focusing beam pattern using the plurality of plane waves to be transmitted by the ultrasound probe at a plurality of steering angles; and transmitting, by the ultrasound probe, the determined plurality of plane waves. 
     Mode of the Invention 
     The terms used in this specification are those general terms currently widely used in the art in consideration of functions regarding the inventive concept, but the terms may vary according to the intention of those of ordinary skill in the art, precedents, or new technology in the art. Also, some terms may be arbitrarily selected by the applicant, and in this case, the meaning of the selected terms will be described in detail in the detailed description of the present specification. Thus, the terms used herein have to be defined based on the meaning of the terms together with the description throughout the specification. 
     When a part “includes” or “comprises” an element, unless there is a particular description contrary thereto, the part can further include other elements, not excluding the other elements. In addition, terms such as “ . . . unit”, “ . . . module”, or the like refer to units that perform at least one function or operation, and the units may be implemented as hardware or software or as a combination of hardware and software. 
     Throughout the specification, an “ultrasound image” refers to an image of an object, which is obtained using ultrasound waves. Furthermore, 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. Also, 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 a human body. 
     Throughout the specification, a “user” may be, but is not limited to, a medical expert, for example, a medical doctor, a nurse, a medical laboratory technologist, or a medical imaging expert, or a technician who repairs medical apparatuses. 
     Some exemplary embodiments will now be explained with the accompanying drawings. 
       FIG. 1  is a view for explaining an ultrasound diagnosis apparatus  100  according to some exemplary embodiments. 
     Referring to  FIG. 1 , the ultrasound diagnosis apparatus  100  includes a probe  110 . Although the ultrasound diagnosis apparatus  100  is connected to the probe  110  by wire in  FIG. 1 , the ultrasound diagnosis apparatus  100  may be wirelessly connected to the probe  110 . Although the ultrasound diagnosis apparatus  100  is connected to only one probe  110  in  FIG. 1 , the ultrasound diagnosis apparatus  100  may be connected to a plurality of probes by wire or wirelessly. 
     The ultrasound diagnosis apparatus  100  may be a cart type apparatus or a portable type apparatus. Examples of portable ultrasound diagnosis apparatuses may include, but are not limited to, a picture archiving and communication system (PACS) viewer, a smartphone, a laptop computer, a personal digital assistant (PDA), and a tablet PC. 
     The probe  110  transmits ultrasound signals to an object  10  and receives echo signals reflected from the object  10 . The probe  110  may include a plurality of transducers. The plurality of transducers oscillate in response to electric signals and generate ultrasound waves that are acoustic energy. The probe  110  according to some exemplary embodiments may transmit ultrasound signals as plane waves. 
     The ultrasound diagnosis apparatus  100  may generate ultrasound data from the echo signals. The ultrasound diagnosis apparatus  100  may generate an ultrasound image based on the ultrasound data. The ultrasound diagnosis apparatus  100  may further include a display that may display the ultrasound image. A user may diagnose the object  10  by seeing the ultrasound image displayed by the ultrasound diagnosis apparatus  100 . 
       FIG. 2  is a block diagram showing a configuration of the ultrasound diagnosis apparatus  100  according to some exemplary embodiments. 
     Referring to  FIG. 2 , the ultrasound diagnosis apparatus  100  includes the probe  110  and a controller  120 . 
     The probe  110  may transmit ultrasound signals as plane waves to an object. The probe  110  may receive echo signals reflected from the object. The probe  110  may transmit a plurality of plane waves. In this case, the probe  110  may transmit the plurality of plane waves so that angles between the probe  110  and the plurality of plane waves are different from one another. Hereinafter, an angle between a plane wave and the probe  110  is referred to as a “steering angle”. For example, the probe  110  may transmit a plurality of plane waves as shown in  FIG. 3 . 
       FIG. 3  is a view of a plurality of plane waves transmitted by the probe  110  according to some exemplary embodiments. 
     Referring to  FIG. 3 , the probe  110  may transmit a plurality of plane waves, for example, first through third plane waves P 1 , P 2 , and P 3 , at a plurality of angles, for example, first through third steering angles θ 1 , θ 2 , and θ 3 . In  FIG. 3 , the x-axis represents a lateral direction and the z-axis represents an axial direction that is a depth direction of an object. 
     The first through third steering angles θ 1 , θ 2 , and θ 3  between the probe  110  and the first through third plane waves P 1 , P 2 , and P 3  are different from one another. The probe  110  may transmit the first plane wave P 1  at the first steering angle θ 1 , may transmit the second plane wave P 2  at the second steering angle θ 2 , and may transmit the third plane wave P 2  at the third steering angle θ 3 . The second steering angle θ 2  may be 0°. The probe  110  may sequentially transmit the first through third plane waves P 1 , P 2 , and P 3 . 
     Although three plane waves, that is, the first through third plane waves P 1 , P 2 , and P 3 , are exemplarily illustrated in  FIG. 3 , the number of plane waves transmitted by the probe  110  or steering angles are not limited. 
     A region of the object to which the second plane wave P 2  whose steering angle with the probe  110  is 0°, that is, that is not steered, is emitted may be referred to as a region of interest (ROI). The ROI may be a region where plane waves are maintained. A region outside the ROI may be a region where transmission of ultrasound waves transmitted from the probe  110  is limited and reception of echo signals is limited. Alternatively, the ROI may be a region of the object that is imaged. 
     A size of the ROI may be determined according to a size D 1  of an aperture of the probe  110 . The size D 1  of the aperture of the probe  110  may be determined by a length of the probe  110 . Alternatively, the size D 1  of the aperture of the probe  110  may be determined by the number of transducers that transmit plane waves among a plurality of transducers included in the probe  110 . Alternatively, when a region smaller than the size D 1  of the aperture of the probe  110  is imaged, a size of the ROI may be less than the size D 1  of the aperture of the probe  110 . 
     Referring back to  FIG. 2 , the controller  120  may determine a plurality of plane waves to be transmitted by the probe  110 . The controller  120  may control the probe  110  to transmit the determined plurality of plane waves. The controller  120  may apply a driving signal to the probe  110 . The probe  110  may transmit the plurality of plane waves to the object according to the driving signal received from the controller  120 . 
     The controller  120  may receive echo signals from the probe  110 . The controller  120  may generate ultrasound data by focusing the echo signals. Also, the controller  120  may generate an ultrasound image based on the ultrasound data. 
     The controller  120  according to some exemplary embodiments may determine the plurality of plane waves so that grating lobes of the plurality of plane waves are suppressed. Also, the controller  120  may focus the echo signals so that the grating lobes are suppressed. 
     Before explaining a method performed by the controller  120  to suppress grating lobes according to some exemplary embodiments, a synthetic transmit focusing beam pattern using a plurality of plane waves will now be explained with reference to  FIGS. 4 through 6 . 
       FIG. 4  is a view for explaining a synthetic transmit focusing beam pattern at one point in an ROI according to some exemplary embodiments. 
     Referring to  FIG. 4 , the probe  110  transmits a plane wave at a steering angle θ. A transmit beam pattern formed at one point (x, z f ) in an ROI may be defined as in Equation 1.
 
Φ θ   t ( x,z   f )= e   −jωt   e   jkd     1     d,d   1   =z   f  cos θ− x  sin θ, k= 2π/λ  [Equation 1]
 
     In Equation 1, k is a wave number, λ is a wavelength, and d 1  is a distance by which a plane wave propagates to the point (x, z f ). 
     The transmit beam pattern of Equation 1 may be modified as in Equation 2.
 
Φ θ   t ( x,z   f )=Φ α   t ( x,z )= e   −jωt   e   jkz     f     β   e   −jkxα ,α=sin θ,β=cos θ,α 2 +β 2 =1  [Equation 2]
 
     As described with reference to  FIG. 3 , the probe  110  transmits a plurality of plane waves at a plurality of steering angles. Each of the plurality of plane waves transmitted by the probe  110  may be represented by using a plane wave angle function A(α). The plane wave angle function A(α) is an intensity of a plane wave with respect to a sine value of a steering angle that is used to transmit the plurality of plane waves. 
     A focal point (x f , z f ) of  FIG. 4  may be an arbitrary point at which imaging is to be performed. When a transmit delay used for each plane wave during synthetic transmit focusing at the focal point (x f , z f ) is τ(x f , z f , α), a synthetic transmit focusing beam pattern may be defined as in Equation 3.
 
Φ t ( x,z   f )=∫ −∞   ∞   A (α)τ( x   f   ,z   f ,α)Φ α   t ( x,z ) dα   [Equation 3]
 
     Since a distance d2 by which the plane wave propagates to the focal point (xf, zf) has to be compensated for by using the transmit delay, the transmit delay may be defined as in Equation 4.
 
τ( x   f   ,z   f ,α)= e   −jkd     2     =e   −jk(z     f     cos θ−x     f     sin θ)   =e   −jkz     f     β   e   jkx     f     α   [Equation 4]
 
     When Equation 2 and Equation 4 are input to Equation 3, Equation 5 may be obtained. 
     
       
         
           
             
               
                 
                   
                     
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     In Equation 5, FT[⋅] is Fourier transform. 
       FIG. 5  is a graph showing a plane wave angle function according to some exemplary embodiments. 
     Referring to  FIG. 5 , a plane wave angle function A(α) is an intensity of a plane wave with respect to a sine value (α=sin θ) of a steering angle θ used to transmit a plurality of plane waves. The plane wave angle function A(α) may be defined as in Equation 6.
 
 A (α)=Σ n=0   N−1 δ(α−α n )  [Equation 6]
 
     In Equation 6, N is the number of steering angles used to transmit a plurality of plane waves, and a total number of times synthesis occurs. N may be the number of plane waves. A sine value cm of each steering angle may be defined as in Equation 7.
 
α n =α min   +Δα·n, ( n= 0,1,2, . . . , N− 1)  [Equation 7]
 
     α min  is a minimum value among sine values of steering angles. That is, α min  is a sine value of a minimum angle among the steering angles. α N−1  is a maximum value α max  among sine values of steering angles. That is, α max  is a sine value of a maximum angle among the steering angles. 
     Δα is an interval between sine values of a plurality of steering angles. Δα may be a difference between sine values of adjacent steering angles. In  FIG. 5 , Δα is constant. In  FIG. 5 , in order to transmit plane waves, steering angles having sine values between which intervals are constant are used. 
     When a plane wave angle function defined in Equations 6 and 7 is used, steering angles of a plurality of plane waves transmitted by the probe  110  are arcsin α 0 , arcsin α 2 , arcsin α 3 , . . . , and arcsin α N−1 . 
     When a plane wave angle function defined in Equations 6 and 7 is used, a synthetic transmit focusing beam pattern may be defined as in Equation 8. 
     
       
         
           
             
               
                 
                   
                     
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     In Equation 8, c 0  and x′ are respectively defined as in Equations 9 and 10.
 
 c   0   =e   −jkx′(α     min     +(N     α     −1)Δα/2)   [Equation 9]
 
 x′=x−x   f   [Equation 10]
 
       FIG. 6  is a graph showing a synthetic transmit focusing beam pattern according to some exemplary embodiments. The graph of  FIG. 6  shows a synthetic transmit focusing beam pattern along an x′-axis using a focal point (x f , z f ) as the center according to some exemplary embodiments. The synthetic transmit focusing beam pattern of  FIG. 6  may be obtained by using Equation 8. 
     Referring to  FIG. 6 , a main lobe M 1  is located at the focal point (x f , z f ) where x′=0. Since a width of the main lobe M 1  is constant irrespective of an axial distance, the quality of an ultrasound image may be improved. 
     Grating lobes G 1 , G 2 , G 3 , and G 4  are located at predetermined intervals from the main lobe M 1  in the synthetic transmit focusing beam pattern. An intensity of each of the grating lobes G 1 , G 2 , G 3 , and G 4  is the same as an intensity of the main lobe M 1 . A position of each of the grating lobes G 1 , G 2 , G 3 , and G 4  may be defined as in Equation 11. 
     
       
         
           
             
               
                 
                   
                     
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     Ultrasound waves having an intensity of the main lobe M 1  are reflected at the focal point (x f , z f ), and echo signals reflected from the focal point (x f , z f ) are received through the probe  110 . The controller  120  may generate ultrasound data by focusing the echo signals. The quality of an ultrasound image may increase as ultrasound waves are more strongly focused on the focal point (x f , z f ). However, an ultrasound beam is strongly focused on points other than the focal point (x f , z f ) due to the grating lobes G(−1), G 1 , G 2 , and G 3 , and thus ultrasound waves having a high intensity are reflected from the points other than the focal point (x f , z f ). Echo signals having a high intensity reflected from the points other than the focal point (x f , z f ) reduce the quality of an ultrasound image. This is because a signal-to-noise ratio (SNR) and a contrast ratio of an ultrasound image may be reduced due to the grating lobes G(−1), G 1 , G 2 , and G 3  and artifacts may occur on the ultrasound image. 
     As described above, the controller  120  according to some exemplary embodiments may determine a plurality of plane waves so that grating lobes of the plurality of plane waves are suppressed. A method performed by the controller  120  to suppress grating lobes according to some exemplary embodiments will now be explained. 
     According to some exemplary embodiments, the controller  120  may determine a plurality of plane waves so that a grating lobe of a synthetic transmit focusing beam pattern is located outside an ROI, which will be referred to as a “first exemplary embodiment”. 
     According to other exemplary embodiments, the controller  120  may determine a plurality of plane waves so that an intensity of a grating lobe is less than an intensity of a main lobe in a synthetic transmit focusing beam pattern using the plurality of plane waves. Next, the controller  120  may control the probe  110  to transmit the determined plurality of plane waves, which will be referred to as a “second exemplary embodiment”. 
     First Exemplary Embodiment 
     A method performed by the controller  120  of the ultrasound diagnosis apparatus  100  to determine a plurality of plane waves so that a grating lobe of a synthetic transmit focusing beam pattern is located outside an ROI according to a first exemplary embodiment will now be explained with reference to  FIGS. 7A through 10B . 
     In some exemplary embodiments, the controller  120  may adjust a plurality of steering angles for transmitting a plurality of plane waves so that a grating lobe is located outside an ROI. 
       FIGS. 7A and 7B  are graphs showing a synthetic transmit focusing beam pattern according to a plane wave angle function for explaining a relationship between a position of a grating lobe and a steering angle according to some exemplary embodiments. In  FIGS. 7A and 7B , D 1  is a size of an aperture of the probe  110 . In  FIGS. 7A and 7B , the size D 1  of the aperture of the probe  110  is equal to a size of an ROI. 
       FIG. 7A  is a graph showing a synthetic transmit focusing beam pattern when a plane wave angle function A 1 (α) in which an interval between sine values of a plurality of steering angles is Δα 1  is used. In  FIG. 7A , a grating lobe G 1   a  of the synthetic transmit focusing beam pattern is located inside the ROI. 
       FIG. 7B  is a graph showing a synthetic transmit focusing beam pattern when a plane wave angle function A 2 (α) in which an interval between sine values of a plurality of steering angles is Δα 2  is used. In  FIG. 7B , the interval Δα 2  is less than the interval Δα 1 . In  FIG. 7B , an ROI is the same as the ROI of  FIG. 7A . In  FIG. 7B , a grating lobe G 1   b  of the synthetic transmit focusing beam pattern is located outside the ROI. 
     Referring to Equation 11, it is found that a position of a grating lobe along an x′-axis in a synthetic transmit focusing beam pattern is inversely proportional to an interval Δα that is an interval between sine values of a plurality of steering angles. Accordingly, it is found that as the interval Δα decreases, the position of the grating lobe is farther from a position (x′=0) of a main lobe. Accordingly, when the interval Δα is adjusted so that a position of a grating lobe that is the closest to the main lobe is greater than the size D 1  of the aperture of the probe  110 , the grating lobe may be located outside an ROI. 
     Accordingly, the controller  120  may determine a plurality of plane waves so that an interval Δα that is an interval between sine values of a plurality of steering angles is equal to or less than a first reference value, as in Equation 12. 
     
       
         
           
             
               
                 
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                     ⁢ 
                     
                         
                     
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                     12 
                   
                   ] 
                 
               
             
           
         
       
     
     According to Equation 12, the controller  120  may set a value obtained by dividing a wavelength by the size of the aperture of the probe  110  as the first reference value. The controller  120  may determine a plurality of plane waves by adjusting a plurality of steering angles based on the interval Δα that is equal to or less than the first reference value. Accordingly, a grating lobe may be located outside the ROI. 
     As described with reference to  FIGS. 7A and 7B , the controller  120  may allow a grating lobe to be located outside an ROI by adjusting a plurality of steering angles for transmitting a plurality of plane waves. 
     Alternatively, according to some exemplary embodiments, the controller  120  may allow a grating lobe to be located outside an ROI by adjusting the number of steering angles of a plurality of plane waves transmitted by the probe  110 . This is because when α min  and α max  are fixed according to a minimum steering angle and a maximum steering angle, the interval Δα may be adjusted by adjusting the number N of steering angles. 
     As described with reference to  FIG. 7B , α min2  and α max2  may be fixed according to a minimum steering angle, and a maximum steering angle and the number (e.g., N 2 =9) of steering angles may be determined so that a grating lobe is located outside an ROI. The controller  120  may adjust the number of steering angles to be equal to or greater than a second reference value. The second reference value may be obtained by using Equation 13 that is a modification of Equation 12.
 
 N≥D 1(α max −α min )/λ+1  [Equation 13]
 
     The controller  120  may determine a plurality of plane waves by adjusting a plurality of steering angles based on the number N of the steering angles that is equal to or greater than the second reference value and satisfies Equation 13. Accordingly, a grating lobe may be located outside an ROI. 
     According to some exemplary embodiments, the controller  120  may allow a grating lobe to be located outside an ROI by adjusting a size of the ROI. 
       FIGS. 8A and 8B  are graphs showing a synthetic transmit focusing beam pattern according to a plane wave angle function for explaining a relationship between a position of a grating lobe and a size of an ROI according to some exemplary embodiments. 
     In  FIGS. 8A and 8B , plane wave angle functions are the same, and thus synthetic transmit focusing beam patterns are also the same. In both  FIGS. 8A and 8B , intervals between sine values of a plurality of steering angles are Δα. However, a size of an ROI (referred to as ROIa) in  FIG. 8A  is D 1  and a size of an ROI (referred to as ROIb) in  FIG. 8B  is D 2  which is less than D 1 . A grating lobe G 1  is located inside the ROIa in  FIG. 8A  whereas the grating lobe G 1  is located outside the ROIb in  FIG. 8B . 
     Accordingly, when the size D 2  of the ROIb is adjusted to be less than a position of the grating lobe G 1  as shown in  FIG. 8B , the grating lobe G 1  may be located outside the ROIb. When the size D 2  of the ROIb satisfies Equation 14, the grating lobe G 1  may be located outside the ROIb. 
     
       
         
           
             
               
                 
                   
                     D 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     2 
                   
                   ≤ 
                   
                     λ 
                     
                       Δ 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       α 
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     14 
                   
                   ] 
                 
               
             
           
         
       
     
     A size of an ROI may be determined by a size of an aperture of the probe  110 . Accordingly, the controller  120  may adjust the size of the aperture of the probe  110  to be less than a position of a grating lobe. In detail, the size of the aperture of the probe  110  may be adjusted to satisfy Equation 12. 
     Alternatively, the controller  120  may limit a region that is to be imaged without adjusting the size of the aperture of the probe  110 . For example, when the size of the aperture of the probe  110  is D 1 , a size of an ROI may be adjusted so that a size of the region that is to be imaged is determined to be D 2  that is less than the size D 1  of the aperture of the probe  110 . 
     Exemplary embodiments in which a size of an aperture of the probe  110  is adjusted in order to adjust a size of an ROI will now be explained with reference to  FIGS. 9A through 10B . 
       FIGS. 9A and 9B  are views of probes having apertures with different sizes according to some exemplary embodiments. 
     Referring to  FIG. 9A , a size of an aperture of a probe  110   a  is D 1  and a size of an aperture of a probe  110   b  is D 2 . That is, a probe may be selected from among the plurality of probes  110   a  and  110   b  based on a size of an ROI to be adjusted. Referring to  FIGS. 8A through 9B , the probe  110   b  whose aperture has the size D 2  may be selected, a size of an ROIb may be adjusted to D 2 , and a grating lobe may be located outside the ROIb. 
       FIGS. 10A and 10B  are views illustrating a case where a size of an aperture of the probe  110  is adjusted by using a plurality of transducers included in the probe  110  according to some exemplary embodiments. 
     Referring to  FIGS. 10A and 10B , the probe  110  includes a plurality of transducers  115 . A size of an aperture of the probe  110  may be adjusted according to the number of transducers for transmitting plane waves among the plurality of transducers  115  included in the probe  110 . 
     In  FIG. 10A , all of the transducers  115  included in the probe  110  transmit plane waves and a size of an aperture of the probe  110  is D 1 . In  FIG. 10B , only some transducers among the transducers  115  included in the probe  110  transmit plane waves and a size of an aperture of the probe  110  is D 2 . In  FIG. 10B , only four transducers among eight transducers  115  are activated. 
     Referring to  FIGS. 8A and 8B  and  FIGS. 10A and 10B , a size of an ROIb may be adjusted to D 2  and a grating lobe may be located outside the ROIb by adjusting the number of activated transducers so that a size of an aperture of the probe  110  is D 2 . 
       FIGS. 10A and 10B  are exemplary views for convenience of explanation, and the number of transducers included in the probe  110  and the number of activated transducers are not limited thereto. 
     As shown in  FIGS. 9A through 10B , a size of an ROI may be adjusted and a grating lobe may be located outside the ROI by adjusting a size of an aperture of the probe  110 . 
     The first exemplary embodiment in which a grating lobe is located outside an ROI by adjusting one of a steering angle and a size of the ROI has been explained with reference to  FIGS. 7A through 10B . The controller  120  of the ultrasound diagnosis apparatus  100  may allow a grating lobe to be located outside an ROI by adjusting one of a steering angle and a size of the ROI, or both the steering angle and the size of the ROI. That is, the controller  120  may allow a grating lobe to be located outside an ROI by adjusting at least one of a steering angle and a size of the ROI. Since a plane wave is not maintained in a region outside an ROI, normal synthetic focusing is not performed in the region outside the ROI. Accordingly, an intensity of a grating lobe may be reduced to be much less than an intensity of a main lobe and the quality of an ultrasound image may be improved. 
     Second Exemplary Embodiment 
     The controller  120  of the ultrasound diagnosis apparatus  100  may determine a plurality of plane waves that are plane waves combinations so that an intensity of a grating lobe is less than an intensity of a main lobe in a synthetic transmit focusing beam pattern using the plurality of plane waves according to a second exemplary embodiment. The plurality of plane waves determined by the controller  120  may include a plurality of plane wave sets, and grating lobes of the plurality of plane wave sets may not overlap one another. 
     A method of determining a plurality of plane waves so that an intensity of a grating lobe is less than an intensity of a main lobe according to the second exemplary embodiment will now be explained with reference to  FIGS. 11A through 14B . 
       FIGS. 11A through 11C  are graphs showing a case where a plurality of plane wave sets in which intervals between sine values of a plurality of steering angles are different from one another are used according to some exemplary embodiments. 
       FIG. 11A  is a graph showing a first synthetic transmit focusing beam pattern when a first plane wave angle function A 1 (α) in which an interval between sine values of a plurality of steering angles is Δα 1  is used.  FIG. 11B  is a graph showing a second synthetic transmit focusing beam pattern when a plane wave angle function A 2 (α) in which an interval between sine values of a plurality of steering angles is Δα 2  is used. 
     Referring to  FIGS. 11A and 11B , main lobes M 1   a  and M 1   b  are located at the same position (x′=0) whereas positions of grating lobes G 1   a  and G 1   b  do not overlap each other. This is because the intervals Δα 1  and Δα 2  between the sine values of the plurality of steering angles for determining the positions of the grating lobes G 1   a  and G 1   b  are different from each other. 
     When a plane wave angle function A(α) obtained by summing the first plane wave angle function A 1 (α) and the second plane wave angle function A 2 (α) is used as shown in  FIG. 11C , a synthetic transmit focusing beam pattern is obtained by summing the first synthetic transmit focusing beam pattern of  FIG. 11A  and the second synthetic transmit focusing beam pattern of  FIG. 11B . In the synthetic transmit focusing beam pattern of  FIG. 11C , intensities of the grating lobes G 1   a  and G 1   b  are less than an intensity of a main lobe M 1 . Since the main lobe M 1   a  in the first plane wave angle function A 1 (α) and the main lobe M 1   b  in the second plane wave angle function A 2 (α) are located at the same position to overlap each other, that is, x′=0, an intensity of the main lobe M 1  is increased. In contrast, since the grating lobe G 1   a  in the first plane wave angle function A 1 (α) and the grating lobe G 1   b  in the second plane wave angle function A 2 (α) do not overlap each other, intensities of the grating lobes G 1   a  and G 1   b  are less than an intensity of the main lobe M 1 . 
     That is, the controller  120  of the ultrasound diagnosis apparatus  100  may use a plurality of plane wave sets in which intervals Δα between sine values of a plurality of steering angles are different from one another as shown in  FIGS. 11A through 11C . Although a plurality of plane waves include two plane wave sets in  FIGS. 11A through 11C , some exemplary embodiments are not limited thereto. The plurality of plane waves may include three or more plane wave sets. The controller  120  may reduce an intensity of a grating lobe relative to a main lobe by using a plurality of intervals Δα. 
     As shown in  FIGS. 11A through 11C , a plurality of plane waves determined by the controller  120  may include a plurality of plane wave sets, and intervals between sine values of a plurality of steering angles for the plurality of plane wave sets may be different from one another. 
       FIGS. 12A and 12B  are graphs showing a case where a plurality of plane wave sets in which intervals between sine values of a plurality of steering angles are different from one another are used according to other exemplary embodiments. 
     Referring to  FIGS. 12A and 12B , α min  and α max  of a first plane wave angle function A 1 (α) and a second plane wave angle function A 2 (α) are the same and the numbers N 1  and N 2  of steering angles included in the first and second plane wave angle functions A 1 (α) and A 2 (α) are different from each other. That is, although minimum steering angles and maximum steering angles of the first plane wave angle function A 1 (α) and the second plane wave angle function A 2 (α) are the same, the numbers N 1  and N 2  of the steering angles are different from each other. Accordingly, intervals Δα 1  and Δα 2  between sine values of the plurality of steering angles are different from each other. 
     When a plane wave angle function A 1 (α)+A 2 (α) obtained by summing the first and second plane wave angle functions A 1 (α) and A 2 (α) in which the numbers N 1  and N 2  of the steering angles are different from each other are used, a plurality of plane wave angle functions in which the intervals Δα 1  and Δα 2  between sine values of a steering angles are different from each other may be used as shown in  FIGS. 11A through 11C . Accordingly, the controller  120  may reduce an intensity of a grating lobe to be less than an intensity of a main lobe. 
     As shown in  FIGS. 12A and 12B , a plurality of plane waves determined by the controller  120  may include a plurality of plane wave sets, minimum steering angles and maximum steering angles of the plurality of plane wave sets may be the same, and the numbers of steering angles of the plurality of plane wave sets may be different from one another. 
       FIG. 13  is a graph showing a case where a plane wave angle function is formed by using sine values of arbitrary steering angles according to some exemplary embodiments. 
     Referring to  FIG. 13 , a plane wave angle function A(α) may be formed by using sine values α of arbitrary steering angles. Although a plane wave angle function in which intervals between sine values of steering angles are constant has been used in the previous exemplary embodiments, intervals between sine values of adjacent steering angles are not constant in  FIG. 13 . 
     As shown in  FIG. 13 , a plurality of steering angles of a plurality of plane waves determined by the controller  1250  may be arbitrary. Accordingly, the controller  120  may reduce an intensity of a grating lobe to be less than an intensity of a main lobe. 
       FIGS. 14A and 14B  are graphs showing a case where a plurality of plane waves in which intervals between steering angles are different from one another are used according to some exemplary embodiments. 
       FIG. 14A  shows a first plane wave angle function A 1 (θ) in which an interval between steering angles, that is, a difference between adjacent steering angles, is a first angle Δθ 1 .  FIG. 14B  shows a second plane wave angle function A 2 (θ) in which an interval between steering angles is a second angle Δθ 2 . 
     Accordingly, when a plane wave angle function obtained by summing the first plane wave angle function A 1 (θ) and the second plane wave angle function A 2 (θ) is used, it may be similar to a case where a plurality of plane wave sets (e.g., see  FIGS. 11A through 11C ) in which intervals between sine values of a plurality of steering angles are different from one another are used. 
     The second exemplary embodiment in which a plurality of plane waves are determined so that an intensity of a grating lobe is less than an intensity of a main lobe in a synthetic transmit focusing beam pattern using a plurality of plane waves has been described with reference to  FIGS. 11A through 14B . A plurality of plane waves may be determined in various ways according to the second exemplary embodiment as shown in  FIGS. 11A through 14B . Also, methods of  FIGS. 11A through 14B  may be used by being combined in various ways. 
     Also, according to methods other than the methods of  FIGS. 11A through 14B , the controller  120  may determine a plurality of plane waves so that an intensity of a grating lobe is less than an intensity of a main lobe. 
     For example, the controller  120  may use different plane wave combinations whenever compounding for synthesizing a series of received ultrasound images is performed. Accordingly, the effect of a grating lobe during the compounding may be reduced. 
     Also, although the first exemplary embodiment in which a plurality of plane waves are determined so that a grating lobe is located outside an ROI and the second exemplary embodiment in which a plurality of plane waves are determined so that an intensity of a grating lobe is less than an intensity of a main lobe have been separately described, the first exemplary embodiment and the second exemplary embodiment may be used by being combined with each other. 
     As described above, the controller  120  of the ultrasound diagnosis apparatus  100  may determine a plurality of plane waves according to at least one of the first exemplary embodiment and the second exemplary embodiment. The controller  120  may control the probe  110  to transmit the determined plurality of plane waves. 
     The probe  110  may receive echo signals reflected from an object. The controller  120  may apply an apodization window to the echo signals received by the probe  110 . In this case, the controller  12  may use an apodization window having a low side lobe. For example, an apodization window having a low side lobe such as a Hanning window or a Hamming window may be used. Accordingly, a grating lobe of the echo signals may be reduced. 
       FIGS. 15A and 15B  are graphs showing a Hanning window W 1  and a rectangular window W 2  according to some exemplary embodiments. In some exemplary embodiments, the controller  120  may apply the Hanning window W 1  to echo signals received by the probe  110  as shown in  FIG. 15A . Since the Hanning window W 1 , instead of the rectangular window W 2 , is used, an intensity of a grating lobe may be reduced compared to an intensity of a main lobe in the received echo signals. 
     An apodization window having a low side lobe such as a Hamming window, instead of the Hanning window W 2  of  FIG. 15A , may be used. 
       FIGS. 16A and 16B  are views illustrating a simulation result for explaining the effect of a synthetic transmit focusing beam pattern in which a grating lobe is located outside an ROI according to the first exemplary embodiment.  FIG. 16A  is a view illustrating a simulation result of a synthetic transmit focusing beam pattern in which a grating lobe is located inside an ROI.  FIG. 16B  is a view illustrating a simulation result of a synthetic transmit focusing beam pattern in which a grating lobe is located outside an ROI. 
       FIG. 16A  illustrates a synthetic transmit focusing beam pattern when a plurality of plane waves that are plane wave combinations having Δα=0.05 (2.866°) and N=5 are used. An intensity of the synthetic transmit focusing beam pattern constantly increases within an ROI (−20 mm&lt;x&lt;20 mm) This is because grating lobes are located in the ROI (−20 mm&lt;x&lt;20 mm) in addition to a region (x=0) where a main lobe is located. Since the grating lobes are located in the ROI (−20 mm&lt;x&lt;20 mm) that is to be imaged, the quality of an ultrasound image is reduced. 
       FIG. 16B  illustrates a synthetic transmit focusing beam pattern when a plurality of plane waves that are plane wave combinations having Δα=0.005 (0.287°) and N=40 are used. An intensity of the synthetic transmit focusing beam pattern is not large in an ROI (−20 mm&lt;x&lt;20 mm) except in a region (x=0) where a main lobe is located. This is because grating lobes are located outside the ROI (−20 mm&lt;x&lt;20 mm) by reducing an interval Δα. Since an ultrasound beam does not strongly reach a region outside the ROI (−20 mm&lt;x&lt;20 mm), an intensity of a grating lobe is reduced to be less than an intensity of the main lobe. 
       FIGS. 17A through 18B  are views illustrating simulation results for explaining the effect of a synthetic transmit focusing beam pattern when a plane wave combination is used so that an intensity of a grating lobe is less than an intensity of a main lobe according to the second exemplary embodiment.  FIGS. 17A and 17B  illustrate a synthetic transmit focusing beam pattern when a plane wave combination using one interval Δα is used.  FIGS. 18A and 18B  illustrate a synthetic transmit focusing beam pattern when a plane wave combination using a plurality of intervals Δα is used. 
       FIGS. 17A and 17B  illustrate a synthetic transmit focusing beam pattern when a plane wave combination having Δα=0.019 (1.083°) and N=23 is used.  FIG. 17A  illustrates an intensity of a synthetic transmit focusing beam pattern according to a lateral distance and an axial distance.  FIG. 17B  is an intensity of a synthetic transmit focusing beam pattern according to a lateral distance. 
     Referring to  FIGS. 17A and 17B , two grating lobes are located in an ROI (−20 mm&lt;x&lt;20 mm), and an intensity of each of the two grating lobes is almost the same as an intensity of a main lobe. Thus, the quality of an ultrasound image may be reduced. 
       FIGS. 18A and 18B  illustrate a synthetic transmit focusing beam pattern when a plane wave combination including a plurality of plane wave sets having Δα=0.406, 0.207, 0.139. 0.084, 0.060 (24°, 12°, 8°, 4.8°, 3.43°) and N=2, 3, 4, 6, 8 (23 in total) is used.  FIG. 18A  illustrates an intensity of a synthetic transmit focusing beam pattern according to a lateral distance and an axial distance.  FIG. 18B  illustrates an intensity of a synthetic transmit focusing beam pattern according to a lateral distance. Positions of grating lobes of plane wave sets having different intervals Δα are different from one another. Although main lobes of the plane wave sets overlap one another and thus intensities of the main lobes are increased, since the grating lobes of the plane wave sets do not overlap one another, intensities of the grating lobes are reduced to be less than those of the main lobes. 
     Accordingly, the quality of an ultrasound image when the plurality of intervals Δα are used as shown in  FIGS. 18A and 18B  may be higher than the quality of an ultrasound image when one interval Δα is used as shown in  FIGS. 17A and 17B . 
       FIGS. 19A and 19B  are views of an ultrasound image according to some exemplary embodiments. 
       FIG. 19A  illustrates a simulation result of a plane ultrasound image synthesized by reducing an intensity of a grating lobe according to some exemplary embodiments.  FIG. 19B  is an actual plane ultrasound image of a human phantom synthesized by reducing an intensity of a grating lobe. 
       FIGS. 20A and 20B  are views of an ultrasound image according to comparative examples. 
       FIG. 20A  illustrates a simulation result of a plane ultrasound image synthesized without considering a grating lobe.  FIG. 20B  is an actual ultrasound image of a human phantom synthesized without considering a grating lobe. 
     In  FIGS. 20A and 20B , it is found that artifacts occur around bright points in an image that is a point target due to the effect of a grating lobe, unlike in  FIGS. 19A and 19B . 
     According to some exemplary embodiments, the quality of an ultrasound image using plane waves may be improved. An SNR and a contrast ratio of an ultrasound image may be increased and artifacts may be removed or reduced in the ultrasound image by allowing a grating lobe that causes image quality degradation to be located outside an ROI or reducing an intensity of a grating lobe relative to a main lobe. 
     Some of the above exemplary embodiments have been performed in the ultrasound diagnosis apparatus  100  of  FIGS. 1 and 2 . However, the some exemplary embodiments may be performed even in an ultrasound probe, instead of the ultrasound diagnosis apparatus  100 . An ultrasound probe according to some exemplary embodiments will now be explained. 
       FIG. 21  is a view for explaining an ultrasound probe  200  according to some exemplary embodiments. 
     Referring to  FIG. 21 , the ultrasound probe  200  may be wirelessly connected to a medical imaging apparatus  300 . The ultrasound probe  200  may be referred to as a “wireless probe”. 
     The ultrasound probe  200  transmits ultrasound signals to the object  10  and receives echo signals reflected from the object  10 . The ultrasound probe  200  may generate ultrasound data from the echo signals. The ultrasound probe  200  may generate an ultrasound image based on the ultrasound data. The ultrasound probe  200  may wirelessly transmit the ultrasound data or the ultrasound image to the medical imaging apparatus  300 . 
     The medical imaging apparatus  300  may display the ultrasound image based on the ultrasound data or the ultrasound image received from the ultrasound probe  200 . The medical imaging apparatus  300  may be any apparatus that may be wirelessly connected to the ultrasound probe  200  and may display the ultrasound image. The medical imaging apparatus  300  may be the ultrasound diagnosis apparatus  100  of  FIGS. 1 and 2 . 
       FIG. 22  is a block diagram showing a configuration of the ultrasound probe  200  according to some exemplary embodiments. 
     Referring to  FIG. 22 , the ultrasound probe  200  may include an ultrasound transceiver  210 , a communication unit  220 , and a controller  230 . 
     The controller  230  may perform an operation similar to an operation performed by the controller  120  of the ultrasound diagnosis apparatus  100 . 
     The controller  230  may determine a plurality of plane waves according to at least one of the first exemplary embodiment and the second exemplary embodiment. The above description may apply, and thus a repeated explanation will not be given. 
     The controller  230  may control the ultrasound transceiver  210  to transmit the plurality of plane waves determined by the controller  230 . 
     The ultrasound transceiver  210  may transmit the plurality of plane waves and may receive echo signals under the control of the controller  230 . 
     The controller  230  may apply an apodization window having a low side lobe to the echo signals. The controller  230  may generate ultrasound data by focusing the echo signals. The controller  230  may obtain an ultrasound image based on the ultrasound data. 
     The controller  230  may control the communication unit  220  to transmit the ultrasound data or the ultrasound image to the medical imaging apparatus  300  through the communication unit  220 . 
     The communication unit  220  may include a wireless communication module so that the ultrasound probe  200  wirelessly communications with the medical imaging apparatus  300 . 
       FIG. 23  is a block diagram showing a configuration of an ultrasound diagnosis apparatus  1000  according to some exemplary embodiments. Referring to  FIG. 23 , the ultrasound diagnosis apparatus  1000  may include a probe  20 , an ultrasound transceiver  1100 , an image processor  1200 , a communication unit  1300 , a display  1400 , a memory  1500 , an input device  1600 , and a controller  1700 , which may be connected to one another via buses  1800 . 
     The ultrasound diagnosis apparatus  1000  of  FIG. 23  may be some exemplary embodiments of the ultrasound diagnosis apparatus  100  of  FIGS. 1 and 2 . The probe  20  and the controller  1700  of the ultrasound diagnosis apparatus  1000  correspond to the probe  110  and the controller  120  of the ultrasound diagnosis apparatus  100  of  FIG. 2 , and thus a repeated explanation thereof will not be given. 
     The ultrasound diagnosis apparatus  1000  may be a cart type apparatus or a portable type apparatus. Examples of portable ultrasound diagnosis apparatuses may include, but are not limited to, a PACS viewer, a smartphone, a laptop computer, a PDA, and a tablet PC. 
     The probe  20  transmits ultrasound waves to the object  10  in response to a driving signal applied by the ultrasound transceiver  1100  and receives echo signals reflected by the object  10 . The probe  20  includes a plurality of transducers, and the plurality of transducers oscillate in response to electric signals and generate acoustic energy, that is, ultrasound waves. Furthermore, the probe  20  may be connected to the main body of the ultrasound diagnosis apparatus  1000  by wire or wirelessly. According to some exemplary embodiments, the ultrasound diagnosis apparatus  1000  may include a plurality of the probes  20 . 
     The probe  20  according to some exemplary embodiments may transmit a plurality of plane waves at a plurality of steering angles. 
     A transmitter  1110  applies a driving signal to the probe  20 . The transmitter  1110  includes a pulse generator  1112 , a transmission delaying unit  1114 , and a pulser  1116 . The pulse generator  1112  generates pulses for forming transmission ultrasound waves based on a predetermined pulse repetition frequency (PRF), and the transmission delaying unit  1114  delays the pulses by delay times necessary for determining transmission directionality. The pulses which have been delayed correspond to a plurality of piezoelectric vibrators included in the probe  20 , respectively. The pulser  1116  applies a driving signal (or a driving pulse) to the probe  20  based on timing corresponding to each of the pulses which have been delayed. 
     A receiver  1120  generates ultrasound data by processing echo signals received from the probe  20 . The receiver  1120  may include an amplifier  1122 , an analog-to-digital converter (ADC)  1124 , a reception delaying unit  1126 , and a summing unit  1128 . The amplifier  1122  amplifies echo signals in each channel, and the ADC  1124  performs analog-to-digital conversion on the amplified echo signals. The reception delaying unit  1126  delays digital echo signals output by the ADC  1124  by delay times necessary for determining reception directionality, and the summing unit  1128  generates ultrasound data by summing the echo signals processed by the reception delaying unit  1126 . Also, according to some exemplary embodiments, the receiver  1120  may not include the amplifier  1122 . In other words, if the sensitivity of the probe  20  or the capability of the ADC  1124  to process bits is enhanced, the amplifier  1122  may be omitted. 
     The image processor  1200  generates an ultrasound image by scan-converting ultrasound data generated by the ultrasound transceiver  1100 . The ultrasound image may be not only a grayscale ultrasound image obtained by scanning an object in an amplitude (A) mode, a brightness (B) mode, and a motion (M) mode, but also a Doppler image showing a movement of an object via a Doppler effect. The Doppler image may be a blood flow Doppler image showing flow of blood (also referred to as a color Doppler image), a tissue Doppler image showing a movement of tissue, or a spectral Doppler image showing a moving speed of an object as a waveform. 
     A B mode processor  1212  in a data processor  1210  extracts B mode components from ultrasound data and processes the B mode components. An image generator  1220  may generate an ultrasound image indicating signal intensities as brightness based on the extracted B mode components. 
     Similarly, a Doppler processor  1214  in the data processor  1210  may extract Doppler components from ultrasound data, and the image generator  1220  may generate a Doppler image indicating a movement of an object as colors or waveforms based on the extracted Doppler components. 
     According to some exemplary embodiments, the image generator  1220  may generate a three-dimensional (3D) ultrasound image via volume-rendering with respect to volume data and may also generate an elasticity image by imaging deformation of the object  10  due to pressure. Furthermore, the image generator  1220  may display various pieces of additional information in an ultrasound image by using text and graphics. In addition, the generated ultrasound image may be stored in the memory  1500 . 
     The display  1400  displays the generated ultrasound image. The display  1400  may display not only an ultrasound image, but also various pieces of information processed by the ultrasound diagnosis apparatus  1000  on a screen image via a graphical user interface (GUI). In addition, the ultrasound diagnosis apparatus  1000  may include two or more displays  1400  according to some exemplary embodiments. 
     The communication unit  1300  is connected to a network  30  by wire or wirelessly to communicate with an external device or a server. The communication unit  1300  may exchange data with a hospital server or another medical apparatus in a hospital, which is connected thereto via a PACS. Furthermore, the communication unit  1300  may perform data communication according to the digital imaging and communications in medicine (DICOM) standard. 
     The communication unit  1300  may transmit or receive data related to diagnosis of an object, e.g., an ultrasound image, ultrasound data, and Doppler data of the object, via the network  30  and may also transmit or receive medical images captured by another medical apparatus  34 , e.g., a computed tomography (CT) apparatus, a magnetic resonance imaging (MRI) apparatus, or an X-ray apparatus. Furthermore, the communication unit  1300  may receive information about a diagnosis history or medical treatment schedule of a patient from a server and utilizes the received information to diagnose the patient. Furthermore, the communication unit  1300  may perform data communication not only with a server or a medical apparatus in a hospital, but also with a portable terminal of a medical doctor or patient. 
     The communication unit  1300  is connected to the network  30  by wire or wirelessly to exchange data with a server  32 , the medical apparatus  34 , or a portable terminal  36 . The communication unit  1300  may include one or more components for communication with external devices. For example, the communication unit  1300  may include a local area communication module  1310 , a wired communication module  1320 , and a mobile communication module  1330 . 
     The local area communication module  1310  refers to a module for local area communication within a predetermined distance. Examples of local area communication techniques according to some exemplary embodiments may include, but are not limited to, wireless 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 module  1320  refers to a module for communication using electric signals or optical signals. Examples of wired communication techniques according to some exemplary embodiments may include communication via a twisted pair cable, a coaxial cable, an optical fiber cable, and an Ethernet cable. 
     The mobile communication module  1330  transmits or receives wireless signals to or from at least one selected from a base station, an external terminal, and a server on a mobile communication network. The wireless signals may be voice call signals, video call signals, or various types of data for transmission and reception of text/multimedia messages. 
     The memory  1500  stores various data processed by the ultrasound diagnosis apparatus  1000 . For example, the memory  1500  may store medical data related to diagnosis of an object, such as ultrasound data and an ultrasound image that are input or output, and may also store algorithms or programs which are to be executed in the ultrasound diagnosis apparatus  1000 . 
     The memory  1500  may be any of various storage media, e.g., a flash memory, a hard disk drive, electrically erasable programmable read-only memory (EEPROM), etc. Furthermore, the ultrasound diagnosis apparatus  1000  may utilize web storage or a cloud server that performs the storage function of the memory  1500  online. 
     The input device  1600  refers to a means via which a user inputs data for controlling the ultrasound diagnosis apparatus  1000 . The input device  1600  may include hardware components, such as a keypad, a mouse, a touch pad, a touch screen, and a jog switch. However, exemplary embodiments of the inventive concept are not limited thereto, and the input device  1600  may further include any of various other input units including an electrocardiogram (ECG) measuring module, a respiration measuring module, a voice recognition sensor, a gesture recognition sensor, a fingerprint recognition sensor, an iris recognition sensor, a depth sensor, a distance sensor, etc. 
     The controller  1700  may control all operations of the ultrasound diagnosis apparatus  1000 . In other words, the controller  1700  may control operations among the probe  20 , the ultrasound transceiver  1100 , the image processor  1200 , the communication unit  1300 , the display  1400 , the memory  1500 , and the input device  1600  of  FIG. 23 . 
     The controller  1700  may perform the above operations according to some exemplary embodiments. 
     The controller  1700  may determine a plurality of plane waves so that a grating lobe of a synthetic transmit focusing beam pattern using the plurality of plane waves is located outside an ROI according to the first exemplary embodiment. 
     Alternatively, the controller  1700  may determine a plurality of plane waves so that an intensity of a grating lobe is less than an intensity of a main lobe in a synthetic transmit focusing beam pattern using the plurality of plane waves according to the second exemplary embodiment. 
     Alternatively, the controller  1700  may determine a plurality of plane waves according to at least one of the first exemplary embodiment and the second exemplary embodiment. 
     The first exemplary embodiment and the second exemplary embodiment have been described above, and thus a repeated explanation thereof will not be given. 
     The controller  1700  may apply an apodization window having a low side lobe to echo signals. 
     All or some of the probe  20 , the ultrasound transceiver  1100 , the image processor  1200 , the communication unit  1300 , the display  1400 , the memory  1500 , the input device  1600 , and the controller  1700  may be implemented as software modules. However, exemplary embodiments of the inventive concept are not limited thereto, and some of the components stated above may be implemented as hardware modules. Furthermore, at least one selected from the ultrasound transceiver  1100 , the image processor  1200 , and the communication unit  1300  may be included in the controller  1700 . However, exemplary embodiments of the inventive concept are not limited thereto. 
       FIG. 24  is a block diagram showing a configuration of a wireless probe  2000  according to some exemplary embodiments. As described above with reference to  FIG. 23 , the wireless probe  2000  may include a plurality of transducers, and, according to some exemplary embodiments of the inventive concept, may include some or all of the components of the ultrasound transceiver  1000  of  FIG. 23 . 
     The wireless probe  2000  of  FIG. 24  according to some exemplary embodiments may include a transmitter  2100 , a transducer  2200 , and a receiver  2300 . Since descriptions thereof are given above with reference to  FIG. 23 , detailed descriptions thereof will be omitted here. In addition, according to some exemplary embodiments, the wireless probe  2000  may selectively include a reception delaying unit  2330  and a summing unit  2340 . 
     The wireless probe  2000  may transmit ultrasound signals to the object  10 , receive echo signals from the object  10 , generate ultrasound data, and wirelessly transmit the ultrasound data to the ultrasound diagnosis apparatus  1000  shown in  FIG. 23 . 
     The wireless probe  2000  of  FIG. 24  may be some exemplary embodiments of the ultrasound transceiver  210  of the ultrasound probe  200  of  FIG. 22 , and thus a repeated explanation thereof will not be given. The wireless probe  2000  of  FIG. 24  may further include the communication unit  220  and the controller  230 , like in  FIG. 22 . 
       FIG. 25  is a flowchart of a method of controlling an ultrasound probe according to some exemplary embodiments. 
     Referring to  FIG. 25 , in operation S 110 , an ultrasound system may determine a plurality of plane waves to be transmitted at a plurality of steering angles by using the ultrasound probe. The plurality of plane waves may be determined according to at least one of the first exemplary embodiment and the second exemplary embodiment. The plurality of plane waves are determined in the first exemplary embodiment so that a grating lobe of a synthetic transmit focusing beam pattern is located outside an ROI and the plurality of plane waves are determined in the second exemplary embodiment so that an intensity of a grating lobe is less than an intensity of a main lobe in a synthetic transmit focusing beam pattern. The first exemplary embodiment and the second exemplary embodiment have been described above, and thus a repeated explanation thereof will not be given. 
     In operation S 120 , the ultrasound system may transmit the determined plurality of plane waves through the ultrasound probe. 
     The ultrasound system that performs the method of controlling the ultrasound probe of  FIG. 25  may be the ultrasound diagnosis apparatus  100  or  1000  or the ultrasound probe  200  or  2000 . Each operation of the method of controlling the ultrasound probe of  FIG. 25  may be performed in a manner as described above. 
     The above some exemplary embodiments may be embodied as a program executed in a computer, and may be implemented in a general-purpose digital computer for executing the program by using a non-transitory computer-readable recording medium. 
     Examples of the computer-readable recording medium include storage media such as magnetic storage media (e.g., read-only memories (ROMs), floppy discs, or hard discs), optically readable media (e.g., compact disk-read only memories (CD-ROMs), or digital versatile disks (DVDs)), etc. 
     While the inventive concept has been particularly shown and described with reference to exemplary embodiments thereof, they are provided for the purposes of illustration and it will be understood by one of ordinary skill in the art that various modifications and equivalent other embodiments can be made from the inventive concept. Accordingly, the true technical scope of the inventive concept is defined by the technical spirit of the appended claims.