Abstract:
In an ultrasonic diagnostic apparatus ( 100 ) capable of generating an ultrasound image equivalent to one generated by combining images shot from various angles, without causing problems concerning an increased number of hardware pieces and a decreased frame rate, a pulsar ( 12 ) generates pulse signals for emitting ultrasound based on trigger signals received from a control unit ( 11 ), and outputs such signals to a group of transducers ( 1 ) via an amplifier ( 13 ). The group of transducers ( 1 ) receives ultrasonic echoes from a scatterer. A buffer ( 17 ) stores the reflected signals received via a delayer ( 14 ) and an A/D converter ( 16 ). A reflection angle detection unit ( 18 ) specifies a reflection angle and a reflection strength pattern of the reflected signals, and a weighting/addition unit ( 15 ) performs weighing based on such reflection strength pattern. A detection unit ( 19 ) performs detection, and a display unit ( 20 ) displays an ultrasound image and the reflection angle.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    (1) Field of the Invention  
           [0002]    The present invention relates to an ultrasonic diagnostic apparatus that displays an ultrasound image on the basis of an echo signal obtained by transmitting and receiving ultrasound.  
           [0003]    (2) Description of the Related Art  
           [0004]    Ultrasonic diagnostic apparatuses have been widely used as indispensable apparatuses in such a field as clinical medicine, since they are capable of obtaining a two-dimensional (2D) image of soft tissues of a living body without invasion as well as offering a high level of safety to such living body to be examined.  
           [0005]    In recent years, ultrasonic diagnostic apparatuses have been required to be capable of quantitatively calculating the size and cross section of a lesion and the like, since changes in their values are used to evaluate the progression and treatment process of the lesion. Therefore, it is also imperative for ultrasonic diagnostic apparatuses to be capable of extracting the contour and boundary of the lesion which are used to calculate its size and cross section.  
           [0006]    The clearer an image is, the more precisely a contour and a boundary are extracted. An ultrasonic diagnostic apparatus receives ultrasonic echoes reflected back from the boundary surface of a scatterer, and generates an ultrasound image based on such reflected echoes. Therefore, if the boundary surface of such scatterer is inclined, the strength of ultrasonic echoes to be received at the points from which the ultrasound was transmitted is reduced. Because of this reason, it is impossible for the existing ultrasonic diagnostic apparatus to reproduce the distribution of actual signal strengths, and therefore to generate a desirable ultrasound image. In order to solve this problem, an existing ultrasonic diagnostic apparatus combines images shot from various angles, so as to generate one ultrasound image.  
           [0007]    [0007]FIG. 1 is a block diagram showing a functional configuration of an existing ultrasonic diagnostic apparatus  500  that combines ultrasound images shot from various angles (Refer to Japanese Laid-Open Patent application No. 5-115479 for example).  
           [0008]    In this ultrasonic diagnostic apparatus  500 , a group of transducers  1  where plural transducers are arranged receives ultrasonic echoes, and converts them into electric signals, which are then delayed by a delayer  3 . Then, such delayed signals are weighted by weighting units  2   a ,  2   b , and  2   c  in respective systems (three systems are shown in FIG. 1), and the weighted electric signals are added by addition units  4   a ,  4   b  and  4   c  in the respective systems. Accordingly, processing is performed based on three received beams  5   a ,  5   b , and  5   c , in appearance, so as to generate an ultrasound image. After this, the electric signals are detected by detection units  19   a ,  19   b , and  19   c  in the respective systems, and these detected electric signals are combined in a secondary addition unit  23 . Finally, a display unit  20  generates and displays an ultrasound image based on such combined signals.  
           [0009]    [0009]FIG. 2 is a block diagram showing an outline of the processing performed by the existing ultrasonic diagnostic apparatus  500 . First, when the group of transducers  1  receives a group of reflected signals, the delayer  3  delays such received reflected signals. The strength of the resulting reflected signals  501  is strong in the right side. Subsequently, the weighting units  2   a ,  2   b , and  2   c  weight the reflected signals  501  according to a weighting pattern  502  (a leftward weighting pattern  5021 , a center weighting pattern  5022 , and a rightward weighting pattern  5023 ). The weighting according to these three patterns corresponds to the reception of the received beams  5   c ,  5   a , and  5   b  in FIG. 1. By weighting the reflected signals  501  according to the respective weighting patterns, a group of weighted electric signals  503  is obtained.  
           [0010]    As FIG. 2 shows, a group of signals which has been weighted according to the leftward weighting pattern  5021  includes no signal components as a group of signals  5031 . A group of signals which has been weighted according to the center weighting pattern  5022  is weak in signal strength as a group of signals  5032 . And a group of signals which has been weighted according to the rightward weighting pattern  5023  is enhanced in signal strength as a group of signals  5033 . When the addition units  4   a ,  4   b , and  4   c  add these signals, an addition result  504  indicates signal components which are strong rightward. Furthermore, when the detection units  19   a ˜ 19   c  detect the resulting signals, signals to be obtained are ones whose rightward signal components are strong. Then, the secondary addition unit  23  adds a detection result  506 , and signals whose rightward signal components are further stronger are obtained as a secondary addition result  507 .  
           [0011]    As described above, even when most of the ultrasonic echoes are strongly reflected back from a rightward direction, the existing ultrasonic diagnostic apparatus is capable of reliably receiving such reflected ultrasound echoes and generating an ultrasound image.  
           [0012]    However, in order to generate an ultrasound image based on ultrasonic echoes from various directions, either of the following two methods is required: combining plural images which are shot by changing angles at which ultrasonic echoes should be received; and combining plural images which are simultaneously shot from various angles. However, the former method has the problem that a frame rate decreases because of an increased number of times images are shot, whereas the latter method has the problem that more pieces of hardware are required in order to receive reflected signals from various directions all at once.  
           [0013]    The existing ultrasonic diagnostic apparatus  500  solves the former problem about a decreased frame rate, but cannot solve the latter problem about an increased number of required hardware pieces.  
         SUMMARY OF THE INVENTION  
         [0014]    The present invention has been conceived in view of the above problems, and it is an object of the present invention to provide an ultrasonic diagnostic apparatus capable of generating an ultrasound image which is equivalent in quality to an ultrasound image generated by combining plural images shot from various angles, without causing the above problems about an increased number of hardware pieces and a decreased frame rate.  
           [0015]    In order to achieve the above object, the ultrasonic diagnostic apparatus according to the present invention may be an ultrasonic diagnostic apparatus, comprising: an ultrasound transmitting/receiving unit in which a plurality of transducers are arranged, each of the transducers transmitting ultrasound into an object to be examined, receiving the ultrasound reflected back from inside said object, and converting the reflected ultrasound into an electric signal; a feature detection unit operable to detect a feature of the reflected ultrasound based on the electric signal converted by each of the transducers; a weighting unit operable to weight the electric signal of each of the transducers in a specified manner, depending on the detected feature; and an image generation unit operable to generate an ultrasound image based on the weighted electric signal of each of the transducers. Moreover, in order to achieve the above object, in the above ultrasonic diagnostic apparatus, the feature detection unit may compare signal strengths of the respective electric signals of the transducers, and determine a reflection angle as the feature of the ultrasound, based on a position of one of the transducers specified by said comparison and on a position of a predetermined reception focal point.  
           [0016]    The above configuration enables reflected signals to be weighted by hardware in a single system based on the reflection strength of ultrasonic echoes. Accordingly, it becomes possible to perform weighting with a simpler hardware configuration for performing weighting as well as to circumvent the problem about a decreased frame rate.  
           [0017]    Note that, in order to achieve the above object, it is possible for the present invention to be embodied as an ultrasonic diagnostic method which includes, as its steps, the characteristic constitute elements of the above ultrasonic diagnostic apparatus, and as a program which includes all of such steps. Also, such program can not only be stored in a ROM and the like equipped to the ultrasonic diagnostic apparatus, but also be distributed via recording media such as CD-ROM, and transmission media such as a communication network.  
           [0018]    As described above, since the ultrasonic diagnostic apparatus according to the present invention assigns weights to reflected signals in an appropriate manner according to a reflection angle of ultrasonic echoes. Accordingly, it is not necessary to combine images even when ultrasonic echoes are strongly reflected in a slanting direction, and therefore it becomes possible to simplify an existing hardware configuration required to perform weighting and secondary addition for a plural number of times. Therefore, the present invention is significantly effective at reducing the number of hardware pieces related to transducers which are arranged in a three-dimensional manner. Moreover, the present invention makes it possible for a reflection angle to be visualized as information about tissues of an examined object in the direction of the scatterer.  
           [0019]    Furthermore, the present invention is capable of obtaining, from a single received beam, an image in accordance with the strength of reflected signals, without needing to generate an ultrasound image from plural received beams passing through the same point as required in an existing technique. Accordingly, it is possible to circumvent the problem about a decreased frame rate attributable to receiving beams for a number of times and the problem about an increased number of hardware pieces attributable to receiving beams from a number of angles.  
           [0020]    For further information about the technical background to this application, Japanese Paten application No. 2003-008749 filed on Jan. 16, 2003 is incorporated herein by reference. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    These and other objects, advantages and features of the invention will become apparent from the following description thereof taken in conjunction with the accompanying drawings that illustrate a specific embodiment of the invention. In the Drawings:  
         [0022]    [0022]FIG. 1 is a block diagram showing a functional configuration of an existing ultrasonic diagnostic apparatus that combines ultrasound images shot from various angles;  
         [0023]    [0023]FIG. 2 is a block diagram showing an outline of processing performed by the existing ultrasonic diagnostic apparatus;  
         [0024]    [0024]FIG. 3 is a block diagram showing a functional configuration of an ultrasonic diagnostic apparatus according to the present invention;  
         [0025]    [0025]FIG. 4 is a diagram showing an example distribution of strengths of ultrasonic echoes reflected back from a scatterer;  
         [0026]    FIGS.  5 A˜ 5 C are diagrams showing examples of weighting patterns to be specified by a weighting unit;  
         [0027]    [0027]FIG. 6 is a diagram showing an example method of detecting reflection angles in a reflection angle detection unit;  
         [0028]    [0028]FIG. 7 is a block diagram showing an outline of processing performed in the ultrasonic diagnostic apparatus according to the present invention;  
         [0029]    [0029]FIG. 8 is a flowchart showing a flow of entire processing performed in the ultrasonic diagnostic apparatus according to the present invention;  
         [0030]    [0030]FIG. 9 is a flowchart showing, in detail, an example of the reflection angle detection processing in FIG. 8; and  
         [0031]    [0031]FIG. 10 is a flowchart showing, in detail, an example of the weighting/addition processing in FIG. 8. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0032]    The following explains the preferred embodiment according to the present invention with reference to the figures.  
         [0033]    [0033]FIG. 3 is a block diagram showing a functional configuration of an ultrasonic diagnostic apparatus  100  according to the present embodiment. As FIG. 3 shows, the ultrasonic diagnostic apparatus  100  is an apparatus that generates an ultrasound image by taking into account angles at which ultrasonic echoes are reflected back from a tissue and the like of an object to be examined (to be also referred to as “scatterer” hereinafter). Such ultrasonic diagnostic apparatus  100  is comprised of a control unit  11 , a pulsar  12 , an amplifier  13 , the group of transducers  1 , a delayer  14 , an A/D converter  16 , a buffer  17 , a weighting/addition unit  15 , a reflection angle detection unit  18 , a detection unit  19 , and a display unit  20 .  
         [0034]    The control unit  11 , which is intended for exercising an overall control of the ultrasonic diagnostic apparatus  100 , is equipped with a CPU, a ROM, a RAM, and the like. In particular, the control unit  11  controls timings (e.g. synchronization) at which each unit in the ultrasonic diagnostic apparatus  100  performs processing. Moreover, the control unit  11  outputs trigger signals for controlling timings at which pulse signals generated by the pulsar  12  are outputted. Also, the control unit  11  receives a reflection angle detected by the reflection angle detection unit  18 , and notifies the display unit  20  of the received reflection angle. Furthermore, the control unit  11  outputs, to the delayer  14 , delay control signals used for performing focus processing.  
         [0035]    The pulsar  12  generates pulse signals according to the trigger signals outputted from the control unit  11 , and outputs such pulse signals to the amplifier  13 . In this case, taking into account that the number of transducers is “T” (“T” is an arbitrary natural number, which is generally 32, 64, and 128), the control unit  11  outputs, to the delayer  14 , delay control signals that allow ultrasonic echoes to be focused on at least one focal point which is located at a certain depth inside an object to be examined and to which ultrasound shall be transmitted (to be referred to as “transmission focal points” hereinafter). Then the control unit  11  determines timings of outputting the trigger signals.  
         [0036]    The amplifier  13  amplifies the pulse signals generated by the pulsar  12 , and the resultant is inputted to the group of transducers  1 . The first “T”th transducers in the group of transducers  1  emit ultrasound focusing on a predetermined focal point (e.g. one of or some of the positions indicated by p 1 ˜p 4  in FIG. 3). Here, transmission beams shall be formed in a horizontal direction with respect to a scanning line  21  which runs vertically to the direction in which the group of transducers  1  is laid out.  
         [0037]    Note that ultrasound transmitted into the examined object is reflected at positions “pm”s at the depth of “m” (“m”=1, 2, . . . ) one by one. The group of transducers  1  receives such reflected ultrasonic echoes, and converts them into electric signals. The converted electric signals (to be referred to as “reflected signals” hereinafter) are inputted to the delayer  14  which corresponds to each transducer in the group of transducers  1 .  
         [0038]    The delayer  14  delays the reflected signals so that the focal point at which the reflected signals should be received (to be referred to as “reception focal point(s)” hereinafter) shifts to p 1 →p 2 →. . . →p 4  sequentially with the elapse of time (processing so-called “dynamic focus”), according to an instruction from the control unit  11 . Then, the delayer  14  transmits the delayed signals to the A/D converter  16 .  
         [0039]    The A/D converter  16  performs A/D conversion on the reflected signals sent by the delayer  14 , and outputs the resulting signals one by one to the buffer  17  and the reflection angle detection unit  18 . Here, the buffer  17  is a storage device made up of a RAM and the like for storing data indicating reflected signals corresponding to all pixels on the display unit  20 .  
         [0040]    The weighting/addition unit  15  is intended for weighting and adding the reflected signals stored in the buffer  17 , and is made up of a weighting unit  151  and an addition unit  152 .  
         [0041]    Referring to FIG. 4, an explanation is given here of the concept of weighting performed by the weighting/addition unit  15 .  
         [0042]    [0042]FIG. 4 is a diagram showing an example distribution of strengths of ultrasonic echoes reflected back from the scatterer (to be referred to as “reflection strengths” hereinafter). Generally, ultrasound is reflected at a boundary surface  204  of a scatterer  203  (e.g. a tissue in the examine object). However, when the boundary surface  204  is inclined at an angle of θ, meaning that the boundary surface  204  is not positioned vertically to the direction in which the ultrasound is transmitted, such ultrasound is strongly reflected toward a direction different from the one in which it was transmitted (in FIG. 4, such direction is one reached by inclining the boundary surface  204  by −2θ anticlockwise). Thus, when ultrasound is strongly reflected toward a direction different from the one in which it was transmitted, the weighting unit  151  performs weighting in a predetermined manner, depending on the strength of such reflected ultrasound. By performing weighting in the above manner, it is possible to generate a sharper ultrasound image.  
         [0043]    The weighting unit  151  is capable of reading out, from the buffer  17 , the data indicating the reflected signals, so as to perform weighting on the read-out data according to an instruction from the reflection angle detection unit  18 . For example, the weighting unit  151  selects one of the pre-registered weighting patterns based on the signal strength pattern of a group of reflected signals specified by the reflection angle detection unit  18  to be explained later, and performs weighting according to such selected weighting pattern. This weighting unit  151  is made up of a plurality of amplifiers (not illustrated in the diagram), which perform gain control on each data under the instructions from the reflection angle detection unit  18  and the control unit  11 .  
         [0044]    Note that the above method is not an exclusive method of weighting reflected signals, and therefore that weighting may also be performed according to an equation.  
         [0045]    Here, an explanation is given of an example method of performing weighting according to an equation. Letting that “h(t)” is the strength of a signal to be inputted from a transducer t (t:1≦t≦T, T: tonal number of transducers) to the reflection angle detection unit  18 , the weight “w(t)” that the weighting unit  151  assigns to an electric signal corresponding to the transducer t can be represented by the use of the following equation (1):  
                 w        (   t   )       =         s        (   t   )           ∑     k   =   1     T                     s        (   k   )              where       ,       s        (   t   )       =         h        (   t   )       -       min     1   ≦   j   ≦   T            (     h        (   j   )       )               max     1   ≦   i   ≦   T            (     h        (   i   )       )       -       min     1   ≦   j   ≦   T            (     h        (   j   )       )                     (   1   )                               
 
         [0046]    In the above equation (1), the weight w(t) of each transducer is represented as a value which is obtained by determining a ratio (s(t)) of the difference between the reflection strength of each transducer t and the minimum reflection strength value with respect to the variations of the reflection strengths (i.e. the difference between the maximum and minimum reflection strength values) and by further normalizing each s(t). In the above equation (1), “max” and “min” are functions which respectively indicate the maximum value and the minimum value of the reflection strengths when i, j, or k changes, where 1≦i, j or k≦T.  
         [0047]    Such weighting unit  151  is capable of dynamically changing weighting patterns. Accordingly, even when ultrasonic echoes are reflected in various directions from each position on the scanning line, it is possible for the weighting unit  151  to perform weighting according to a weighting pattern appropriate to the respective directions. Subsequently, the addition unit  152  performs addition on each weighted reflected signal outputted by the weighting unit  151  on a pixel-by-pixel basis in the display unit  20 .  
         [0048]    FIGS.  5 A˜ 5 C are diagrams showing examples of the weighting patterns to be specified by the weighting unit  151 . FIG. 5A shows the weighting pattern  31  to be used when a group of signals with strong signal strength appears in the left side of the group of transducers  1 . FIG. 5B shows the weighting pattern  32  to be used when a group of signals with strong signal strength appears in the center of the group of transducers  1 . FIG. 5C shows the weighting pattern  33  to be used when a group of signals with strong signal strength appears in the right side of the group of transducers  1 .  
         [0049]    Note that, as indicated by broken lines in FIGS.  5 A˜ 5 C, more simplified weighting patterns  41 ˜ 43  may also be used in the respective cases.  
         [0050]    The reflection angle detection unit  18  determines a reflection angle of the ultrasonic echoes based on the values of the respective reflected signals which are outputted from the A/D converter  16  and which are obtained from the respective transducers  1 ˜T. Furthermore, the reflection angle detection unit  18  specifies a signal strength pattern of the reflected signals, and sends the specified signal strength pattern to the weighting unit  151 . For example, the reflection angle detection unit  18  detects, from among the reflected signals obtained via the group of transducers  1 , a group of signals with strong signal strength, and specifies a signal strength pattern of such signals. Moreover, the reflection angle detection unit  18  determines a reflection angle on the basis of the position of a transducer that corresponds to the reflected signal with the strongest signal strength out of the group of reflected signals (A detailed explanation is given later of a method of detecting a “reflection angle”).  
         [0051]    Note that the present invention is not limited to the above-explained weighting pattern specification method, and therefore that another method may also be used. An example is pattern matching utilizing a neural network and a method that simply limits a section in which weighting should be performed.  
         [0052]    The detection unit  19  detects the reflected signals obtained in the weighting/addition unit  15 , and outputs the resultant to the display unit  20 . The display unit  20  generates an ultrasound image on the basis of the reflected signals outputted from the detection unit  19 , and displays the image on the CRT or the like. Furthermore, the display unit  20  displays, as the inclination of the boundary surface  204 , the value of the reflection angle itself sent by the control unit  11  or such reflection angle. Accordingly, the user of the ultrasonic diagnostic apparatus  100  can know the inclination of the examined object. Note that possible methods of representing or presenting such inclination include a method of representing the inclination as color information and a method of presenting the inclination as a numeric value, but the present invention is not limited to these methods.  
         [0053]    Also note that an ultrasonic diagnostic apparatus is normally required to take into account an anti-noise measure and signal dampening attributable to propagated distance. However, such details are not directly related to the features of the present invention, and therefore an explanation of them is omitted here.  
         [0054]    [0054]FIG. 6 is a diagram showing an example method of detecting reflection angles in the reflection angle detection unit  18 . As FIG. 6 shows, the direction on the scanning line in which the ultrasonic echo with the strongest signal reception strength shifts to a direction  221 →a direction  222 →a direction  223 →a direction  224 , along with the shift of the reception focal points to positions p 1 →p 2 →. . . →p 4 .  
         [0055]    Here, let us focus on the reception focal point p 1 , and give an explanation of a method of detecting a reflection angle on the basis of the ultrasonic echo reflected back from such position p 1 . Generally, the following values are known beforehand (i.e. the following values are under the control of the control unit  11 ): (i) the timing at which ultrasound is transmitted; (ii) the timing at which ultrasonic echoes are received; and (iii) the transmission speed at which the ultrasound is transmitted inside the examined object. Therefore, based on these values (i)˜(iii), it is possible to determine a vertical distance  11  from the bottom of the group of transducers  1  to the position p 1  as well as a distance L1 from the scanning line  21  to the transducer that receives the ultrasonic echo with the strongest reflection strength, and to determine θ1 from |1 and L1. Note that θ2˜θ4 at p 2 ˜p 4  shall also be determined in this manner.  
         [0056]    Next, referring to FIGS.  7 ˜ 10 , an explanation is given of the operation of the ultrasonic diagnostic apparatus  100  with the above configuration.  
         [0057]    [0057]FIG. 7 is a block diagram showing an outline of the processing performed in the ultrasonic diagnostic apparatus  100 .  
         [0058]    First, when the A/D converted reflected signals are stored into the buffer  17  ( 501 ), the reflection angle detection unit  18  notifies the weighting/addition unit  15  that the reflection strength in the right side of the group of transducers  1  is strong, based on such reflected signals. Then, the reflection angle detection unit  18  detects a reflection angle, and notifies the weighting/addition unit  1  of the detected reflection angle. Here, an area of interest  5012  shall be the right side of the group of transducers  1  indicating a strong reflection strength. In this case, the weighting/addition unit  15  selects a weighting pattern  6021  with which weighting is performed in a specified manner, performs weighting on the area of interest  5012  according to such selected weighting pattern  6021  ( 603 ), and adds up the reflected signals ( 604 ). As a result, the result of adding the reflected signals in the area of interest  5012  as well as the detection result in the detection unit  19  will be further enhanced (in FIG. 7, such enhanced results are indicated as “Extremely strong”).  
         [0059]    [0059]FIG. 8 is a flowchart showing the flow of the entire processing performed in the ultrasonic diagnostic apparatus  100 .  
         [0060]    First, the pulsar  12  receives trigger signals from the control unit  11 , generates pulse signals for emitting ultrasound based on such trigger signals, and outputs the generated pulse signals to the group of transducers  1  via the amplifier  13  (S 501 ). In this case, the delayer  14  generates the pulse signals so that ultrasonic pulses can be focused on at least one transmission focal point located at a certain depth inside the examined object according to delay control signals sent by the control unit  11 .  
         [0061]    Next, when the group of transducers  1  receives ultrasonic echoes reflected back from the scatterer (Yes in S 502 ), the reflected signals are stored in the buffer  17  via the delayer  14  and the A/D converter  16  (S 503 ).  
         [0062]    Subsequently, the reflection angle detection unit  18  specifies a reflection angle and the signal strength pattern of the reflected signals (S 504 ), and the weighting/addition unit  15  performs weighting and addition processing accordingly (S 505 ).  
         [0063]    Then, the detection unit  19  detects the reflected signals (S 506 ), and the display unit  20  displays a generated ultrasound image and the reflection angle (S 507 ). The above steps are repeated until the diagnosis completes (S 501 ˜S 508 ).  
         [0064]    [0064]FIG. 9 is a flowchart showing, in detail, an example of the reflection angle detection process ( 5503 ) in FIG. 8.  
         [0065]    First, the reflection angle detection unit  18  specifies reflected signals received at the reception focal point pm, upon the instruction of the control unit  11  (S 601 ), and reads out necessary data from the buffer  17  (S 602 ).  
         [0066]    Next, the reflection angle detection unit  18  compares the sizes of such received reflected signals on a transducer-by-transducer basis (S 603 ), and specifies a weighting pattern based on the signal strength pattern of the reflected signals ( 5604 ). Furthermore, the reflection angle detection unit  18  specifies a transducer Tx that has received the reflected signal with the strongest signal strength (S 605 ).  
         [0067]    Subsequently, the reflection angle detection unit  18  determines a reflection angle from the position of the reception focal point pm and the position of the transducer Tx (S 606 ). Then, the reflection angle detection unit  18  sends the determined reflection angle to the control unit  11  and the weighting/addition unit  15  (S 607 ).  
         [0068]    [0068]FIG. 10 is a flowchart showing, in detail, an example of the weighting/addition process (S 504 ) in FIG. 8.  
         [0069]    First, the weighting unit  151  receives the reflection strength pattern and the reflection angle from the reflection angle detection unit  18  (S 701 ). On the basis of such reflection angle (S 702 ), the weighting unit  151  selects one weighting pattern (e.g. one of the weighting patterns  31 ˜ 33 ) (S 703 ˜S 705 ).  
         [0070]    Next, the addition unit  152  weights the reflected signals according to the selected weighting pattern (S 706 ), and adds the resulting signals (S 707 ).  
         [0071]    Then, the addition unit  152  outputs the added reflected signals to the detection unit  19  (S 708 ).  
         [0072]    As described above, the ultrasonic diagnostic apparatus according to the present invention specifies a reflection angle on the basis of the strength of ultrasonic echoes and weights reflected signals according to such reflection angle. Accordingly, with a hardware configuration simpler than that of an existing ultrasonic diagnostic apparatus, it becomes possible to generate an ultrasound image which is equivalent in quality to an ultrasound image generated by such existing ultrasonic diagnostic apparatus.  
         [0073]    Note that the above-explained embodiment presents an example in which the weighting unit  151  specifies a weighting pattern, but it is also possible that the reflection angle detection unit  18  specifies a weighting pattern instead.  
         [0074]    Also, the above-explained embodiment presents an example in which a method of selecting a weighting pattern based on the reflection angle and a method using the equation (1) are used as the methods of determining a weighting pattern. However, the present invention is not limited to these methods, and therefore a weighting pattern may also be determined, for example, by using the learning algorithm in the neural network as well as by employing pattern matching.  
         [0075]    Furthermore, the above-explained embodiment presents an example in which transducers are arranged in a one-dimensional array, but the present invention is not limited to such arrangement. Therefore, the present invention is also applicable to a group of transducers in two-dimensional or three-dimensional array.  
         [0076]    Moreover, the ultrasonic diagnostic apparatus may be implemented as any one of an analog circuit, a digital circuit, and software.