Abstract:
An ultrasonic diagnostic apparatus has an ultrasonic probe for transmitting and receiving an ultrasonic wave at a group of a plurality of ultrasonic vibrators arranged in an array form to and from a subject and incorporating a preamplifier groups for amplifying the resulting weak ultrasonic echo received after obtaining tissue information about the subject. The ultrasonic vibrator group has a first area to which a first amplifier group is to be connected and a second preamplifier group to which a second amplifier group is to be connected. In an operating mode to cease the first preamplifier group from operating, a control circuit switches to supply the bias current being supplied to the first preamplifier group over to the second preamplifier group.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2006-193086, filed Jul. 13, 2006, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a real-time ultrasonic diagnostic apparatus and ultrasonic diagnostic apparatus and system using an ultrasonic probe that is to obtain in real time an image in a living body while scanning with an ultrasonic beam, and more particularly to an ultrasonic diagnostic apparatus using a probe incorporating an electronic circuit therein. 
     2. Description of the Related Art 
     Recently, the ultrasonic two-dimensional (2D) array probe, etc. tend to incorporate an electronic circuit in the probe head thereof, to generate a transmission waveform and amplify/partially beam-form the resulting reception echo. For example, JP-A-2000-139907 describes an ultrasonic diagnostic apparatus using such a two-dimensional array probe. 
     Meanwhile, it can be considered to use a stack of piezoelectric elements, etc. in order to suppress the impedance increase resulting from the miniaturization of vibrator elements. 
     For example, in the real-time ultrasonic diagnostic apparatus using a probe incorporating an electronic circuit, its probe handle is made up with an ultrasonic vibrator group, a pulser group, a preamplifier group, a sub-array beam former group, and a control circuit for controlling those. Meanwhile, an ultrasonic probe is constituted by the probe handle together with a probe cable, a probe connector and an electronic circuit group and an in-probe-connector control circuit. 
     Meanwhile, in the ultrasonic diagnostic apparatus body to which the ultrasonic probe is connected through the probe connector, amplification is made on the ultrasonic echo signals subjected to reception-delay addition at the in-body amplifier group. The amplified ultrasonic echo signals are matched in timing together at a reception-delay addition circuit and then detected at a signal processing section, to be extracted of an envelope. This is transformed in coordinate at the image processing section and processed suitably for image display, thus being displayed on a display section. This allows for displaying the subject as shape information in a real time. 
     In the meanwhile, by transmitting and receiving an ultrasonic wave at a center frequency f0 to and from the blood flowing through the subject, an ultrasonic beam having a frequency f0+fd is received by means of the moving corpuscles through the action of a Doppler shift fd proportional to the blood velocity. For this reason, by detecting the Doppler shift frequency fd and displaying a change in time thereof, blood-velocity information is to be displayed as a Doppler image. 
     In such a case, by two-dimensionally mapping the detected Doppler shift frequencies fd and displaying those over the ultrasonic image through proper color change, the image of the subject can be displayed in real time as a color Doppler image (not shown) including blood velocity information. 
     The ultrasonic probe recently uses a two-dimensional array of vibrators wherein the number of vibrators amounts to several thousands while reduced in their individual sizes. In such a case, if connecting the probe directly to the ultrasonic diagnostic apparatus, there is a need of increasing number of cables. This however increases cable thickness and hence raises troublesomeness upon handling. Moreover, there encounters a difficulty in delivering a drive waveform to the precise vibrators with efficiency and in conveying an ultrasonic echo, received at the precise vibrators, with quality. 
     Consequently, for two-dimensional array or the like, the ultrasonic probe is mounted with an electronic circuit including transmission and reception circuits. In addition, it is an often practice to reduce the number of input signal lines to the ultrasonic diagnostic apparatus by driving a number of precise vibrators with easiness and efficiency, amplifying a received weak ultrasonic echo with efficiency and summing up the values through partial reception-beam forming as to several vibrators a time. 
     However, there is a need to reduce the heat generation at the electronic circuit incorporated in the probe, in order to suppress the temperature rise of the ultrasonic probe within a permissible level. Consequently, there is a problem that the power, to be supplied to the incorporated electronic circuit, could not be increased. Meanwhile, as for the preamplifier group for ultrasonic-echo amplification, FETs (field-effect transistors) in most cases are used as representative amplification elements. The FET preamplifier requires a greater amount of bias current as shown in  FIG. 1 , in order to obtain a broad dynamic range at low noise. 
     The FET M1 has a noise-in-input (thermal noise) that is to be determined as in the following.
 
 v   n =4 kT (2/3)·(1/ gm )
 
 gm= 2· I   D /( VGS−V   TH )
 
     Accordingly, the bias-current must be increased for reducing the noise. 
     Namely, in order to amplify an extremely weak Doppler signal superposed on a great-amplitude clutter (reflection of from heart wall, etc.) as in a continuous wave Doppler (SCW) mode, there is a need to supply a significantly great bias current that is nearly double the bias current for obtaining the usual B-mode image. 
     As a result, heat generation increases on the preamplifiers to increase the probe temperature, thus resulting in excessive heat generation and possible improper operation of the incorporated electronic circuit. In case the bias current is used suppressively in order to avoid it, dynamic range is not fully obtained as to the preamplifiers. This makes it difficult to amplify a weak signal component with fidelity, thus making it impossible to obtain information to a diagnostically required extent. 
     BRIEF SUMMARY OF THE INVENTION 
     Therefore, it is an object to provide an ultrasonic diagnostic apparatus and an ultrasonic diagnostic apparatus and system using an ultrasonic probe that are reduced in noise level at the preamplifiers without increasing consumption power and heat generation but increased in dynamic range thereby securing the reception performance in a continuous wave Doppler mode, etc. and obtaining a good ultrasonic image, wherein the ultrasonic diagnostic apparatus uses a two-dimensional array probe, etc. incorporating an electronic circuit such as preamplifiers. 
     Namely, the first invention comprises: 
     an ultrasonic probe that has a plurality of ultrasonic vibrators arranged in an array form and for transmitting and receiving an ultrasonic wave to and from a subject, and a plurality of preamplifiers connected respectively to the plurality of ultrasonic vibrators and for amplifying a reception signal obtained by transmission and reception thereof; 
     a transmission/reception control section that is configured to transmit and receive, by switchover, a pulse wave and a continuous wave at the ultrasonic probe; and 
     a control circuit that controls to supply a bias current substantially equivalently to the plurality of preamplifiers when sending/receiving a pulse wave, and to supply a bias current greater than a bias current, to be supplied to the preamplifiers to be connected to the ultrasonic vibrators for use in transmission, to the preamplifiers to be connected to the ultrasonic vibrators for use in reception when sending/receiving a continuous wave. 
     Meanwhile, the second invention comprises: 
     a plurality of ultrasonic vibrators that are arranged in an array form to transmit and receive an ultrasonic wave to and from a subject and having a first area and a second area; 
     a pulser group that drives the plurality of ultrasonic vibrators at the first and second areas and causes to transmit an ultrasonic wave; 
     a preamplifier group that amplifies tissue information about the subject received by the plurality of ultrasonic vibrators at the first and second areas; and 
     a control circuit that, in an operating mode to cease from operating a first preamplifier group to be connected to the first area and from operating a second pulser group to be connected to the second area, control is made to supply a bias current, being supplied to the first preamplifier group, to a second preamplifier group to be connected to the second area. 
     Furthermore, the third invention comprises: 
     an ultrasonic probe having
         a plurality of ultrasonic vibrators that are arranged in an array form to transmit and receive an ultrasonic wave to and from a subject and having a first area and a second area,   a pulser group that drives the plurality of ultrasonic vibrators at the first and second areas and causes to transmit an ultrasonic wave,   a first preamplifier group that amplifies tissue information about the subject received at the first area of the plurality of ultrasonic vibrators,   a second preamplifier group that amplifies tissue information about the subject received at the second area of the plurality of ultrasonic vibrators, and   a control circuit that controls to supply a bias current, being supplied to the first preamplifier group, to the second preamplifier group in an operating mode to cease the first preamplifier group from operating; and       

     an ultrasonic diagnostic apparatus connected to the ultrasonic probe and for obtaining information obtained at the ultrasonic probe and supplying power. 
     According to the invention, there is provided an ultrasonic diagnostic apparatus and ultrasonic diagnostic apparatus and system using an ultrasonic probe, which is reduced in noise level at the preamplifiers without increasing consumption power and heat generation but increased in dynamic range thereby securing the reception performance in a continuous wave Doppler mode, etc. and obtaining a good ultrasonic image, wherein the ultrasonic diagnostic apparatus uses a two-dimensional array probe, etc. incorporating an electronic circuit such as preamplifiers. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principle of the invention. 
         FIG. 1  is a view explaining the relationship between a bias current to the ultrasonic-echo amplifying FET and a noise, in the prior art; 
         FIG. 2  is a block diagram showing a construction of a real-time ultrasonic diagnostic apparatus using a probe incorporating an electronic circuit, according to a first embodiment of the present invention; 
         FIG. 3  is a figure exemplifying shape information about the subject-to-observe displayed in real time on a display section of the  FIG. 2  ultrasonic diagnostic apparatus; 
         FIG. 4  is a flowchart explaining the operation of the ultrasonic diagnostic apparatus of the first embodiment of the invention; 
         FIG. 5A  is a figure explaining the ultrasonic vibrators and preamplifiers in a usual pulse transmission/reception mode; 
         FIG. 5B  is a figure explaining the ultrasonic vibrators and preamplifiers in an SWC mode; 
         FIG. 6  is a figure exemplifying blood velocity information displayed as an SCW Doppler image; and 
         FIG. 7  is a flowchart explaining the operation of an ultrasonic diagnostic apparatus according to a second embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to the drawings, explanation is now made below on embodiments according to the present invention. 
     First Embodiment 
     Referring to  FIG. 2 , there is illustrated a block diagram showing a construction of a real-time ultrasonic diagnostic apparatus using a probe incorporating an electronic circuit, according to a first embodiment of the invention. 
     In  FIG. 2 , the ultrasonic diagnostic apparatus of this embodiment includes an ultrasonic probe  10 , and an ultrasonic diagnostic apparatus body  50  to which the ultrasonic probe  10  is connected through a body-end probe connector  40 . 
     The ultrasonic probe  10  is made up with a probe handle  12 , a probe cable  14  having one end connected to the probe handle  12 , and a probe connector  16  connected to the other end of the probe cable  14 . 
     The probe handle  12  is made up with an ultrasonic vibrator group  20 , a pulser group  22 , a preamplifier group  24 , a sub-array beam former group  26 , and an in-probe-handle control circuit  28  for placing those under control. 
     The ultrasonic vibrator group  20  are arranged, say, in an N×M array form as referred later, to transmit and receive an ultrasonic wave to and from a subject  30  (e.g. heart). The pulser group  22  is connected to the ultrasonic vibrator group  20 , to drive the ultrasonic vibrator group  20  in accordance with the different timing generated by the in-probe-handle control circuit  28 , thus generating an ultrasonic beam having a predetermined directivity. Due to this, an ultrasonic beam is to be irradiated from the ultrasonic vibrator  20  to the subject  30 , according to an electric signal from the pulser group  22 . 
     The preamplifier group  24  is to perform processing such as low-noise amplification and buffering in order to favorably obtain a weak ultrasonic echo signal to be received at the ultrasonic vibrator group  20 , by transmitting the ultrasonic beam from the ultrasonic vibrator group  20  in a manner to reflect upon an interface where acoustic impedance is different, e.g. boundary of textures of the subject  30  and obtain information about the structure, movement, etc. of the subject  30 . The sub-array beam former group  26  is to sum up the output signals of from the preamplifier group  24  by providing a delay time based on each group of several channels, thereby reducing the number of the output signal lines of from the ultrasonic probe  10 . This reduces the number of probe cables  14 . 
     The in-probe-handle control circuit  28  is to take control the operations of the pulser group  22 , the preamplifier group  24  and the sub-array beam former group  26 . According to the control signal of from the in-probe-handle control circuit  28 , the preamplifier group  24  is set with operating conditions, e.g. bias current, on its element-by-element basis. 
     The probe handle  12  and the probe connector  16  are connected together through the probe cable  14 . The probe connector  16  incorporates therein an electronic circuit group  34  configured by a plurality of electronic circuits and an in-probe-connector control circuit  36 . The electronic circuit group  34  is to perform additional processing, such as amplification, buffering and band adjustment, on the ultrasonic echo signal, as required. Meanwhile, the in-probe-connector control circuit  36  is to control the operation of the electronic circuit group  34 , and to generate a control signal, delivered from the in-probe-handle control circuit  28 , on the basis of the control signal received from the ultrasonic diagnostic apparatus body  50 , referred later. 
     The ultrasonic diagnostic apparatus body  50  is configured with an in-body preamplifier group  52 , an in-body reception-delay addition circuit  54 , a signal processing section  56 , an image processing section  58 , a display section  60 , an in-body transmission-delay circuit  62 , an in-body pulser group  64 , an in-body control circuit  66  and an operation panel  68 . 
     The in-body preamplifier group  52  is to amplify the ultrasonic echo signals that were first subjected to reception-delay addition at the ultrasonic probe  10  on the group-by-group basis of several channels. The ultrasonic echo signals amplified are matched in timing together by the in-body reception-delay addition circuit  54 . The ultrasonic echo signals are then detected by the signal processing section  56 , to extract an envelope. Furthermore, the ultrasonic echo signals, extracted of the envelope, are transformed in coordinate in accordance with a sectional plane of the subject  30  at the image processing section  58 , processed in intensity level suitably for image display or so, thus being displayed on the display section  35 . This allows the display section  60  to display in real time the shape information about the subject, as shown in  FIG. 3 . 
     Meanwhile, the in-body control circuit  66  is to control the operation of the processing sections in the ultrasonic diagnostic apparatus body  50  and to supply control information to the in-probe-connector control circuit  36  of the probe connector  16 . The operation panel  68  is input means for the operator to input or select information, e.g. to execute a continuous wave Doppler (SCW) mode in which beam steering is available, as an operation mode. 
     Incidentally, the in-body transmission-delay circuit  62  and the in-body pulser group  64  are to be operated where the ultrasonic probe does not incorporate an electronic circuit, i.e. where the usual probe is connected to drive the ultrasonic vibrators  20  by the ultrasonic diagnostic apparatus body  50 . It is usually incorporated in the ultrasonic diagnostic apparatus body  50  but may be omitted to provide. 
     Referring to the flowchart of  FIG. 4 , description is now made on the ultrasonic diagnostic apparatus according to the first embodiment of the invention. 
     When power is put on by means of a not-shown power supply, the present routine is started. At step S 1 , a control code is transferred to the preamplifier group  24  at all the channels, to establish a basic bias current ib. From the vibrator group  70  in a 2D N×M array arrangement as shown in  FIG. 5A , ultrasonic echo signals amplified at the N×M preamplifier group  24  are transferred to the ultrasonic diagnostic apparatus body  50 . The in-body preamplifier group  52  amplifies the ultrasonic echo signals that were first subjected to reception-delay addition at the ultrasonic probe  10  on the group-by-group basis of several channels. The ultrasonic echo signals are matched in timing at the in-body reception-delay addition circuit  54  and detected by the signal processing section  56 , to extract an envelope. Then, the image processing section  58  transforms those in coordinate in accordance with a sectional plane of the subject  30  and processed in intensity level suited for image display. This allows the display section  60 , at step S 2 , to display an image in the usual mode, e.g. B mode. 
     In this state, observation is assumed conducted in the SCW mode. Thereupon, at step S 3 , the operator is to select an SCW mode by operating the operation panel  68  of the ultrasonic diagnostic apparatus body  50 . In this case, an SCW mode is selected by putting on a not-shown switch on the operation panel  68 . Based on the input to the operation panel  68 , the in-body control circuit  66  sets up the ultrasonic diagnostic apparatus body  50  to operate in the SCW mode. Simultaneously, a control signal is supplied to the in-probe-connector control circuit  36  of the ultrasonic probe  10 . Thereupon, the in-probe-connector control circuit  36  regulates the control signal into a form to be processed by the in-probe-handle control circuit  28 . Thus, the regulated control signal (control code) is conveyed to the in-probe-handle control circuit  28 . 
     In the in-probe-handle control circuit  28 , the pulser group  22  and the preamplifier group  24  are controlled based on the control signal. This divides the 2D N×M array arrangement of vibrator group  70 , into an area  70   a  for transmission of an ultrasonic wave and an area  70   b  for reception, as shown in  FIG. 5B . At step S 4 , the in-probe-handle control circuit  28  transfers a control code to turn off the pulser group  22  lying under the SCW reception area  70   b.    
     Furthermore, at the next step S 5 , the in-probe-handle control circuit  28  transfers a control code to turn off the preamplifier group  24   a  lying under the SCW transmission area. Then, at step S 6 , control is made to add the bias current ib, usually used at the preamplifier group  24   a , to the bias current ib to the preamplifier  24   b  lying under the SCW reception area  70   b  as shown in  FIG. 5A . 
     In the usual pulse transmission/reception mode, the 2D N×M array  70  serves for transmission/reception at all of its elements as shown in  FIG. 5A . In such a case, the bias current to the N×M preamplifier group  24  is given ib. 
     In the SCW mode, the probe is used separated in region, i.e. a region for transmission and a region for reception. Namely, division is as an (N/2)×M array (SCW transmission area)  70   a  and an (N/2)×M array (SCW reception area)  70   a , as shown in  FIG. 5B . For this reason, the preamplifier group  24  is turned off (bias current rendered 0) at its (N/2)×M elements in a region to be connected to the SCW transmission area  70 . The bias current (ib), being supplied to the preamplifier group  24   a  lying under the SCW transmission area, is added to the bias current to the preamplifier group  24   b  lying under the SCW reception area. Namely, the bias current, for the preamplifier group  24   b  lying under the SCW reception area, is given as ib+ib (=2ib). Thus, the bias current is increased. Incidentally, consumption power does not increase at the incorporated electronic circuit because the increase of bias current corresponds to the amount of consumption at the preamplifiers to be desirably put off. 
     In this embodiment, by controlling the probe-handle  12  consumption power not to exceed a predetermined value, the preamplifiers lying under the area for SCW reception can be operated to favorably amplify the extremely slight Doppler signal that is superposed on a high-amplitude clutter (reflection from the heart wall, etc.) at less noise and in an improved dynamic range without increasing the generation heat at the probe handle  12 . As a result, an ultrasonic wave is transmitted at a center frequency f0 to the blood flowing through the subject. By moving blood corpuscles together with the slow movement of the heart and blood vessel walls, a weak ultrasonic echo based on the transmission beam frequency is favorably received at a frequency f0+fd experienced a Doppler shift in proportion to the blood velocity, in a state superposed on a great-amplitude clutter component resulting from the slow movement of the heart and blood cell wall, etc. By detecting the Doppler shift frequency fd and displaying the change thereof in time, blood velocity information is displayed as an SCW Doppler image as shown in  FIG. 6 . 
     Second Embodiment 
     Now description is made on a second embodiment according to the invention. 
     In the first embodiment, the ultrasonic vibrator group  20  and preamplifier group  24  were divided by on the software under control of the in-body control circuit  66 , in-probe-connector control circuit  36  and in-probe-handle control circuit  28 . The second embodiment is to divide the ultrasonic vibrator group  20  and preamplifier group  24  by means of hardware. 
     From now on, the second embodiment of the invention is described. Incidentally, the real-time ultrasonic diagnostic apparatus, using a probe incorporating an electronic circuit, is similar in configuration to that of the first embodiment. Hence, by attaching identical reference numeral to identical element to thereby omit to explain, i.e. explanation will be made only on the operation. 
     Referring to  FIG. 7 , there is illustrated a flowchart explaining the operation of the ultrasonic diagnostic apparatus, according to the second embodiment of the invention. 
     When putting on power by means of a not-shown power supply, the present routine is started. At step S 11 , a basic bias current ib is supplied through an exclusive line to the preamplifier group  24  at all the channels. Then, the in-body preamplifier group  52  amplifies the ultrasonic echo signals subjected to the first reception-delay addition on the group-by-group basis of several channels at the ultrasonic probe  10 . The amplified ultrasonic echo signals are matched in timing at the in-body reception-delay addition circuit  54  and then detected at the signal processing circuit  56 , to be extracted of an envelope. Then, those are transformed in coordinate matched to the sectional plane of the subject  30  at the image processing section  58  and processed in intensity level suitably for image display. This allows the display section  60 , at step S 12 , to display an image in the usual mode, e.g. B mode. 
     In this state, observation is conducted at step S 13  in the SCW mode. Thereupon, the operator selects an SCW mode by operating the operation panel  68  of the ultrasonic diagnostic apparatus body  50 . In this case, SCW mode is selected by putting on a not-shown switch on the operation panel  68 . Based on the input to the operation panel  68 , the in-body control circuit  66  sets the ultrasonic diagnostic apparatus body  50  to operate in the SCW mode. Simultaneously, a control signal is supplied to the in-probe-connector control circuit  36  of the ultrasonic probe  10 . Thereupon, the in-probe-connector control circuit  36  regulates the control signal into a form to be processed by the in-probe-handle control circuit  28  within the probe handle  12 . The regulated control signal (control code) is supplied to the in-probe-handle control circuit  28 . 
     Based on the control signal, the in-probe-handle control circuit  28  controls the pulse group  22  and the preamplifier group  24 . This divides the 2D N×M array arrangement vibrator group  70  into an area  70   a  for transmission of an ultrasonic wave and an area  70   b  for reception, as shown in  FIG. 5B . At step S 14 , power is turned off to the pulser group  24  lying under the SCW reception area  70   b . Namely, the power line or the bias current is shut off by means of a relay or semiconductor switch provided, say, on the in-probe-handle control circuit  28 . 
     Furthermore, at the following step S 15 , power is shut off to the preamplifier  24  lying under the SCW transmission area. Namely, the power line or the bias current is shut off by means of a relay or semiconductor switch provided, say, in the in-probe-handle control circuit  28 . Then, at step S 16 , to the preamplifier group  24  is supplied a bias current  2   ib  in an amount double the bias current ib usually used on the exclusive line as shown in  FIG. 5A . 
     With this structure, consumption power does not increase at the incorporated electronic circuit because the increase of bias current corresponds to the amount of consumption at the preamplifiers that are desirably to be put off. 
     Incidentally, in the second embodiment, the hardware was exemplified with the relay or semiconductor switch provided in the in-probe-handle control circuit  28  and for turning off the power to the pulser group  22  and preamplifier group  24 . However, this is not limitative, e.g. it may be provided in the pulser group  22 , the preamplifier group  24  or the like. 
     In the first and second embodiments, the consumption power at the preamplifier group is naturally controlled in its total amount not to exceed the upper limit thereof even if changing the ratio of transmission and reception areas at the ultrasonic vibrators. 
     Although the first and second embodiments described the two-dimensional array case of the ultrasonic vibrator group  20 , it is not limitative. Application is similarly possible to the array vibrators arranged in a one-dimensional or irregular form. 
     The preamplifier group  24  is not limited to the incorporation in the probe handle  12 . It can be built in the probe connector  16 , in which case effects are similarly obtainable. Furthermore, SCW mode is not limitative but application is possible quite similarly as to the mode to use by separating the ultrasonic vibrator group  20  into different purposes of operating areas. 
     Although the invention was described by way of the embodiment, the invention is to be modified in the scope not departing from the gist thereof besides the embodiment described so far. 
     Furthermore, the foregoing embodiment includes various aspects of the invention, wherein various inventions are to be extracted by suitably combining a plurality of constituent elements disclosed. For example, in case certain elements are deleted from all the elements disclosed in the embodiment, the structure deleted of the elements is to be extracted as an invention where the problem mentioned in the introductory part can be solved and the effect therein can be obtained. 
     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.