Ultrasound imaging apparatus for providing simultaneous b-scan and doppler data

The invention relates to an ultrasonic imaging An apparatus according to claim 1st

From US-PS 41 41 347 discloses an ultrasonic An imaging apparatus is known which is equal to term reproduction of a B-scan image and a Blutflußpro fils, which is obtained by a Doppler system allows. The ver here employed Doppler and B-scan converter zugehö of their wrestle electronic processing circuits substantially operated independently. In the same or similar Frequencies and simultaneous operation of the two transducers are against -side interference of the transmission and echo signals unavoidable. Si multanbetrieb the Doppler and B-scan converter is at the be known device only possible if Doppler and B-Abtastwand ler send at (significantly) different wavelengths.

The invention is based on the object B-sample and to obtain Doppler data in Simultanbtrieb without a disturbing Be influencing the reception signals of a transducer by the Gesen stattfin Deten and reflected pulses of the other converter det.

In an ultrasonic imaging apparatus of the initially genann th kind, this object is inventively achieved by the Features of patent claim 1.

The inventive interleaving of the first and second transducers associated ultrasonic pulse transmission phases is the ultrasound imaging device even free from egg gene disorders, if the wavelengths of both transmit signals over attune. When coincident transmitting and Empfangswellenlän gen, the processing circuits Herge cost presents and operated. In particular, the two can Converter to an array or a head who summarized the since the transmission and reflection waves for both systems ver have rable properties. The alignment of the Doppler and B may scanning beam on the respective application cases are perfectly matched.

Although the ultrasonic pulses from the first and second Converters interleaved in time, ie not be overlapping be sent, appear the acquired B-scan and Doppler Data for the operator continuously and simultaneously. The Phase separation is therefore unre for interference-free picture side set effective, but not visible to the user (Simultaneous operation).

Further advantageous embodiments of the invention are in in the sub-claims.

In the following, the invention is based on the Drawing arrangement embodiments illustrated explained in detail.

In the drawings

<b>Fig.</b> 1 is a side view of the imaging device, from the overall shape of the housing and the fields of view of the B-scan and Doppler converter can be seen;

<b>Fig.</b> 2 is a front view of the apparatus according <b>Fig.</b> 1 along the section line 2-2 in <b>Fig.</b> 1;

<b>Fig.</b> 3 is a sectional view of the device along section line 3-3 in <b>Fig.</b> 2;

<b>Fig.</b> 4 is a sectional view taken along section line 4-4 in <b>Fig.</b> 1;

<b>Fig.</b> 5 is another sectional view taken along the Section line 5-5 in <b>Fig.</b> 2 (in this view the motor is not shown, so that the front of device for positioning the Doppler converter better apparent);

<b>Fig.</b> 6 is a plan view of the manual Positionin tion device for positioning the Doppler transducer seen along section line 6-6 in <b>Fig.</b> 5;

<b>Fig.</b> 7 is a sectional rear view of Vorrich tion in accordance <b>Fig.</b> 6 taken along section line 7-7 in <b>Fig.</b> 6;

<b>Fig.</b> 8 is a view on the gear segment for driving the Doppler transducer is used, and the coupling segment with the device in accordance with the <b>Fig.</b> 6 and 7, seen in Rich of the arrows 8-8 in <b>Fig.</b> 6;

<b>Fig.</b> 9 is a partial sectional view taken along Section line 9-9 in <b>Fig.</b> 5 to illustrate lichung attaching the Doppler transducer within the fluid chamber and its Coupling a position potentiometer;

<b>Fig.</b> 10 is a block diagram of a circuit for Ge winnung the continuous B-scan and Doppler data;

<b>Fig.</b> 11 is a graph for describing the operation as the circuit of <b>Fig.</b> 10;

<b>Fig.</b> 12, an alternative embodiment of the circuit of <b>Fig.</b> 10 with a representative circuit;

<b>Fig.</b> 13 is a diagram for describing the operation of the circuit of <b>Fig.</b> 12th

Disclosed is an ultrasound imaging device with a hand-held "head" and associated circuitry.

The imaging head described and associated circuitry simultaneously provide a B-Abtastwiedergabe and Doppler data. (The Doppler data in Tonfrequenzform again given; However, they are also, for example, under United use of a fast Fourier transform processing.) In the following description, the "B-scan converter" and "Doppler transducer" reference. It is clear that the Hin , to "B-scan" and "Doppler" not special wall lertypen designate, but specify which echoes from these converters are included. For the purposes of Be case, however, it is convenient to the respective transducer as "B-scan converter" or "Doppler transducer" to designate.

In the <b>Fig.</b> 1 to 9 is an imaging head is shown, both B-scan converter as well as the Doppler transducer ent holds. The signals, in particular those from the B-sample converters, are for playback in general in such manner processed, which is described in US-PS 42 41 412th However, there are some differences in the electrical Ver processing. First, the echo of each "vector" the B-scan converter at predetermined locations in memory stored, ie there is a one-to-one mapping between the angular position of the B-scan converter and the Posi tions in the memory. The memory addresses for storing the B-scan converter data received directly from the encoder described below determined. These addresses are used to both the tangent and the Sekansfunktionen (in a read only memory) look up. Therefore, it is not necessary for the tangent and the secant be in accordance with the Patent og from the known method to calculate. Also, a "look-up table "to determine the refraction in the invention not mandatory. As will be explained, is the Angle between the transducers and the interface with the Body due to the use of a flexible interface not known.

The other aspects of the electrical processing of the the transducers derived signals significantly different are of the known method, used in conjunction with the <b>Fig.</b> 10 and 11. This includes the Circuit that a continuous audio signal (The Doppler data) delivers, although the Doppler transducer is sometimes turned off to the B-scan type continuously to bring up to date. This circuit allows (From the user's point of view) a simultaneous B-scan and Doppler data extraction when the beam bunch are interleaved in time.

Hereinafter, first to the <b>Fig.</b> 1 and 2 taken. The imaging head is a hand-held device, which has a handle <b>20</b> and a housing <b>25</b> having. The flexible membrane <b>27</b> the patient is opened for investigation and makes it possible for the beam of the wall learning <b>16</b> and <b>17</b> along the short fluid path between these transducers and the membrane <b>27</b> pass. In the described embodiment, a GE knew preamp derived from these transducers Signals from a circuit on a printed scarf tion card performed in the handle <b>20</b> appropriate (cf.. circuit card <b>68</b> according to <b>Fig.</b> 3). An elec trical coupling between the head and the electrical Processing device and the display units go via the cable <b>21</b>,

The B-scan converter <b>16</b> performs an oscillatory and sweeps the with <b>16</b>a designated field of view. The Doppler transducer <b>17</b>Which is opposite to the transducer <b>16</b> ver is is arranged developed a beam bundle to the field of view <b>16</b>a coplanar. The angular position of converter <b>17</b> is by the handwheel <b>23</b> set manually, to a field of view <b>17</b>a overcoat.

In the described embodiment, the view is field corresponding to the sector <b>16</b>A deeper if the B-Ab tastwandler is operated without the Doppler transducer. currency rend of simultaneous B-scan and Doppler operation is the field depth of the B-scan converter on with <b>16</b>b designated field of vision is reduced. Doppler echoes from actually any point within the field of view <b>16</b>b can by adjusting the angle of the transducer <b>17</b> and by adjusting the area for the cutout Echoes are sampled by this converter. (A Be reichstoreinstellung is not on the head but on a separate keypad provided.)

The B-scan converter <b>16</b> is an ordinary, commercially available transducer at a frequency of approximately z. B. 7.5 MHz is operated. Because of the reciprocating movement the converter would on the pivot ends more pulses and hervorge fewer pulses in the pivotal central region call when the pulse frequency of the converter would be constant. To avoid this, a sinusoidal distribution the pulse repetition frequency provided to a uniform To achieve spacing of vectors or beams. The average pulse repetition frequency is approximately 2.5 kHz during the sole B-scan operation. The Doppler transducer<b>17</b> operates at a genau.-controlled frequency of,., about 3 MHz and a pulse sequence frequency of 10 kHz. How be will be written, some pulses are of this converter locked to the B-sample representation continuously on the to bring state. A verfüg commercially Barer ultrasonic transducer serves as a Doppler transducer <b>17</b>,

The housing, the head consists of three glasfaserverstärk th polycarbonate injection molded components. The lower housing component serves as Abtastkopfchassis and forming one half a fluid chamber. The middle housing part ver vollständigt the fluid chamber and contains the Converter waves, dynamic seals and a flow medium inlet. The upper housing part serves as a cover, which decrease access to all Abtastkopfvorrichtungen and allows for the electronics to service the equipment and adjust. The three housing components are watertight finished, so that the head for cleaning purposes in a cleaning liquid can be immersed.

The fluid chamber <b>33</b> (<b>Fig.</b> 4) ent between to set parallel walls <b>37</b> and <b>38</b> educated. The Rear wall <b>32</b> this chamber is best in <b>Fig.</b> 5 to see. One end of the chamber is a by a rubber membrane or rubber Shoe <b>27</b> educated. A filling opening with a closure to stuff <b>30</b> permit filling the chamber after At sembly of the imaging head. Both converters<b>16</b> and <b>1</b>- are arranged in the interior of the fluid chamber in such a way that its beam, the membrane <b>27</b> pierced.

The membrane <b>27</b> is a silicone rubber membrane in iron oxide is embedded, and a density of about 1.4 to 1.5 Has. The acoustic resistance of this membrane is to approached 1.5 according to the usual value of the acoustic Resistance of the human tissue.

It should be noted that the membrane <b>27</b> flexible is such that a shape when placed on the skin- Patient changes. This means that the angle of incidence of leaving the ultrasonic head and back to this non specific periodic ultrasound beam. For this Therefore, it is important that the speed of the Ultra sound in the in the chamber <b>33</b> contained fluid as close as possible to that in the human Ge tissue is adapted.

As in the <b>Fig.</b> 1, 3, 4 and 9 can be seen, both converter <b>16</b> and <b>17</b> arranged so that their beams in a common plane extend, ie coplanar are. Both transducers are in a common plane between the walls <b>37</b> and <b>38</b> pivotally mounted.

The converter <b>16</b> is on a shaft <b>49</b> attached, their one end of a bearing in the wall <b>37</b> is mounted. The other end of the shaft is a dynamic log tion <b>34</b> performed and ends outside the chamber <b>33</b> as crankshaft <b>49</b>, The for the connection of the transducer<b>16</b> be constrained electrical lines are passing through the center wave <b>49</b> led to the outside, as best shown in <b>Fig.</b> 3 is to recognize and 9th (It should be noted that the Lei obligations in <b>Fig.</b> 3 for clarity over the housing <b>25</b> are led out; Usually the cables within the housing to the printed circuit board <b>68</b> or cable <b>21</b> out.) According to <b>Fig.</b> 9 is also the converter <b>17</b> between the walls <b>37</b> and <b>38</b> ge to pin superimposed, which pivotal movement in the motion level of the transducer <b>16</b> enable. A pin<b>40</b> is through a dynamic seal (not shown) in the Ge housing wall <b>38</b> stored. The journal<b>40</b> is connected to the transmission sector <b>42</b> (<b>Fig.</b> 5). The transmission sector<b>42</b> becomes via a pin <b>45</b> driven. The teeth on the gear sector <b>42</b> mesh with a gear <b>46</b>a; this gear drives the potentiometer <b>46</b>, At the output of the potentiometer is determined, a signal of the angular position Doppler transducer displays. (This output is to Together with the range setting a pointer to the B-Abtastwiedergabe.)

The following is the <b>Fig.</b> 3 and 4 reference is made. The wave <b>49</b> the transducer <b>16</b> is at one end with a crank <b>50</b> connected. The other end of the crank arm<b>50</b> is connected to one end of a drive rod <b>51</b> connected. The other end of the drive rod <b>51</b> is eccentric with a drive wheel <b>55</b> connected, which directly from the engine <b>54</b> (<b>Fig.</b> 4) is driven. The motor<b>54</b> drives the drive wheel <b>55</b>. whereby the driving rod <b>51</b> reciprocation and executes the transducer <b>16</b> oscillating on the shaft <b>49</b> emotional.

An encoder <b>57</b> is on a wheel <b>56</b> at ex drive shaft of the motor <b>54</b> attached. In the encoder<b>57</b> are a plurality of slots formed which Lagein a formation through the converter <b>16</b> arise. An inner track, consisting of three elongated, arcuate slots <b>58</b>, Used for development of commutation for the engine <b>54</b>, The outer track<b>60</b> consists of a plurality of sinusoidally distributed openings for generating triggering signals for the transducer <b>16</b> serve. use is also a single slot <b>61</b> between the inner and outer tracks.

The light from light-emitting diodes, which behind the disc <b>57</b> arranged, but not shown, is of detectors <b>59</b> and a detector <b>62</b> collected. The the slots <b>58</b> penetrating light of the Detek tors <b>59</b> detected. The output of these detectors is use of motor Kommutatorzerhackern. The motor<b>54</b> is a six-pole brushless direct current three-phase motor, which is actuated by a synchronous motor. During loading drive without Doppler (only B-scan) runs approximately 10 revolutions per second (<b>20</b> Frames per second) to and in the Doppler modes run at 2 revolutions per second (<b>4</b> Frames per second) to.

Through the slot <b>61</b> Light incident is from the detector <b>62</b> detected, a reference signal once per revolution of the disk <b>57</b> developed. This reference signal is used to determine the Wheel position (position of the transducer <b>16</b>).

The slots in the outside lane <b>60</b>, Are, as stated above, arranged on the disk in a sinusoidal distribution, and the through these slots <b>60</b> transmitted light is of the detector <b>62</b> collected. The output of this Detector is used to generate transmit command signals to Triggering of the transducer <b>16</b>, Due to the sinusoidal distri ment of the slots <b>60</b> are from the transducer <b>16</b> generated Ultrasonic pulses evenly (spatially) distributed so not produced in uniform temporal division. The Pulses are developed at a higher repetition frequency, when the converter is in the center position of its Schwenkbe movement is because it is there at a higher Winkelge rate moves. The pulses are a niedri sent Geren repetition frequency when the transducer the End of its swinging approaches. (In the described from leadership example, the converter <b>16</b> a total swing angle of about 28 °, ie + 14 ° from a normal to the Mem brane <b>27</b> extending line.)

A thumbwheel <b>23</b> (<b>Fig.</b> 3) is connected via a cable with the pen <b>45</b> ganged. A movement of the adjusting rads <b>23</b> lets the pen <b>45</b> the sector gear <b>42</b> move, whereby the angular position of the transducer <b>17</b> changes. In the described embodiment, the can converter move through an angle of approximately 45 °. (When a Line from the center of the transducer <b>17</b> normal to the diaphragm <b>27</b> is pulled, moves the transducer <b>17</b> in between 10 and 55 degrees with respect to this line.)

The following is the <b>Fig.</b> 5, 6, 7 and 8 GE accepted. A special positioning device serves altering the angular position of the transducer <b>17</b>, As in the <b>Fig.</b> 5 and 6 it can be seen, this apparatus is the imaging head by a C-shaped bracket <b>76</b> and a U-shaped bracket <b>77</b> attached. A metallic Füh extension tube <b>74</b>a is connected to one end of the support <b>77</b> and up the other side to one end of the support <b>76</b> connected. The other end of the support <b>76</b> to an end of a Füh tion pipe <b>74</b>b on; the other end of the guide tube<b>74</b>b is connected to the other end of the support <b>77</b> connected. The guide tubes <b>74</b>a and <b>74</b>b are tubes of corrosion-free Steel, which are welded to the supports and in United connection with the supports a closed rigid frame component form.

As best seen in <b>Fig.</b> 6 and 7 can be seen, is the thumbwheel <b>23</b> via a bearing <b>80</b> in the support <b>77</b> supported tert. The wire<b>82</b> is through the guide tubes and through a slot <b>81</b> on the drive axle end <b>78</b> of thumbwheel <b>23</b> out. The cable is provided with two windings to the drive axle end <b>78</b> wrapped. A fuse ring <b>79</b> not even run these turns of the Drive axle.

The free ends of the wire rope <b>82</b> are, as best shown in <b>Fig.</b> can be seen 8, by a sleeve <b>84</b> carried out; on End of the rope forms a loop <b>82</b>a, which at the pen <b>45</b> is wrapped. The bow<b>82</b>A is around the pen <b>45</b> tightened (it is for better representation in <b>Fig.</b> 8 loose shown). The wire<b>82</b> is then clamped and the sleeve <b>84</b> compressed to the wire rope fixed down.

It can be seen that when turning the thumbwheel <b>23</b> the wire rope inside the tubes <b>74</b>a and <b>74</b>b is moved, and the drive pin <b>45</b> adjusted, in turn, the angle position of the transducer <b>17</b> changes.

A significant advantage of the above-described Vorrich tion is that it is already fully assembled can be before it is inserted into the imaging head becomes. The thumbwheel<b>23</b> is in the support <b>77</b> built-in and the wire rope around the pin <b>45</b> tensioned before the Device is installed in the head. this makes possible an expedient and slight tension of the wire rope. When installed in the head, the whole device is about the supports fixed and the pin <b>45</b> in the gear segment <b>42</b> pressed. Since the pipes with the supports firmly welded, the voltage changes in the wire rope not when installing the device in the head.

There are several modes in which use of the head becomes. While a pure B-scan (without Doppler) are from the transducer <b>16</b> 20 frames per second for the recovery produced by B-scan data. In simultaneous B-sample and Doppler operation are at four frames per second B-scan data generated along with the Doppler data. The Maximum B-scan pulse repetition rate in this simultaneity term operation is 800 Hz. The disc <b>57</b> and the Doppler pulses are asynchronous, so that pulses (or pulse requirements) of both transducers simultaneously or close can occur at the same time. Of course this is uner wishes, largely because a light emanating from a transducer Transmission signal is received as an echo in the other converter can. To avoid this, finds a Impulsverschachte ment instead. As will be described below, are despite this nesting and the shutdown of Doppler transducer uninterrupted simultaneous Be operation from the viewpoint of the operator.

The B-scan pulses have opposite the Doppler pulses Priority. Doppler pulses are interrupted when a B-scan during the simultaneous operation of the Converter is necessary. In one embodiment, the Invention is used a preset circuit which the waveform of the initiated by the Doppler echoes Audio signal pretending.

The following is on <b>Fig.</b> Reference 10 taken. While simultaneous operation of the B-scan and Doppler emits converter and receives the Doppler transducer signals far more often than the B-scan converter. The pulse generator<b>126</b> receives a 10 kHz signal, and causes the transducer <b>17</b> Pulses with this frequency emits. The echoes of converter <b>17</b> be at a receiving and mixing stage <b>99</b> applied. The frequency shift of the echo from the 3 MHz transmit pulse is determined and gives the Doppler data. In the described preferred Ausführungsbei game develops the receiving and mixing stage <b>99</b> two Output data channels (quadrature channels <b>1</b> and <b>2</b>). Two channels are used to determine the direction of the frequency shift required, which corresponds to the direction of blood flow. The receiving and mixing stage <b>99</b> operates in a similar Manner as a Einseitenbanddetektor.

The audio signal on the line <b>132</b> (Channel <b>1</b>) and the corresponding audio signal for the channel <b>2</b> will the development of the final audio frequency or audio signal. An additional 90 ° phase shift is introduced between these signals are then the sum and the difference of these two signals ge gained to a "stereophonic" sound for the Operation to create man. When a signal is ahead of the other runs, as an audio-frequency output signal is in a sound speaker designed; when a channel relative to the other indulges, is an output signal in the other volume speaker developed. From this, the operator can so continued determine the direction of current difference. also be quick in the described embodiment, Fourier transformations of these audio signals ver used to provide additional data on the characteristics the bloodstream to win.

The trigger pulses for the B-scan converter that of the encoder <b>57</b> (<b>Fig.</b> 3 to be developed), are a line <b>90</b> to a pulse generator and tarry tion circuit <b>91</b> transfer. The signal on the line<b>90</b> calls for a B-scan pulse of the pulse Gene erator <b>125</b>, However, a B-scan does not occur as long as on until the pulse generator <b>125</b> an enable signal a line <b>130</b> receives. The signal on a line<b>129</b> is an enable / breaker circuit for the Doppler pulse generator <b>126</b> applied. In the next On enter the 10 kHz signal provides-release / Breakers circuit <b>128</b> an enable signal on the line <b>130</b> and the pulse generator <b>125</b>, This is also the delivery a sound pulse by the transducer <b>17</b> interrupted. Therefore, the B-scan pulses with the 10 kHz signal can be synchronized, and instead the development of a Doppler impulses occurs B strobe. In this way ensures an interleaved converter operation. As described in connection with <b>Fig.</b> 11 will be described, is only one Doppler pulse for each B-Abtastan lost receivables.

The enable / disable circuit <b>128</b> is a blocking signal to an AND gate <b>127</b>, This signal occurs simultaneously with the enable signal on. A Bereichstorsignal is just if applied to the input of this AND gate. This Bereichstorsignal is the electrical "Fenstery" laid the specifies when the converter <b>17</b> received echoes are valid. This signal is of course a function of depth, from the echo to be received, and by applying a signal on the line <b>131</b> to a sample-and-hold circuit <b>140</b> set. When the output signal of the AND gate <b>127</b> is at a high level, repeatedly Ab palpable and hold circuit <b>140</b> the previous sample. Therefore, when the output signal of the AND gate on a high level, the output signal of the receiver is ignored and mixing stage.

The following is on <b>Fig.</b> Reference 11 taken in the shown waveform for a typical audio signal is, as it on the line <b>133</b> arises. Assume that at a time shortly before the line 123 on the Lei tion <b>90</b> a signal is received. At the time<b>123</b> would normally a further Doppler pulse occur. This Doppler pulse is suppressed and, instead, occurs a B-sampling on. Since a signal on the line<b>131</b> is present, the output signal on the line <b>133</b> to the previous scan. In other words, the prior the time <b>123</b> signal level existing at the time <b>123</b> in the in <b>Fig.</b> 11 manner shown repeatedly. For time Point <b>124</b> is processed a regular Doppler signal. It should be noted that, as shown in <b>Fig.</b> 11 a kon tinuierliches audio signal is generated, although a Doppler pulse is missing.

An alternative embodiment of the circuit according to <b>Fig.</b> 10 is in <b>Fig.</b> 12 shown. In this embodiment, contact the B-scan and Doppler pulses in a real asynchronous Follow on with a circuit to the right of exclusive OR gate <b>94</b> a given audio signal to Kompen generates sation of lost Doppler data.

If a B-strobe request shortly after the keys a Doppler pulse is received, it is necessary sending out B-sample pulses long enough to ver hesitate to accommodate the Doppler data (a time margin of no more than 100 microseconds in the ver applied field depth required). The delay of the B-Abtastsendung affects playback does not remember Lich. Thereafter, the Doppler pulses are sufficiently long ge blocks to a transmission and reception of the B-sample impulse enable. In practice, the B-scan to run requirement signals of the actual triggering of the B-scan converter through approximately 100 microseconds advance, so that it is not necessary for the triggering of the transducer <b>16</b> selectively delaying. On the other hand, in this Arrangement necessary to Doppler transducer for at least 200 microseconds (250 microseconds normally) to lock.

It is assumed that during the simultaneous Doppler and B-scan operation a pulse on line <b>90</b> (<b>Fig.</b> 12) received; this pulse is to monoflop<b>92</b> and <b>93</b> applied. This immediately put two high (H) signals to an OR gate <b>94</b>, One of these signals disables the pulse generator<b>98</b> and thus prevented over a period of 250 microseconds keying further Doppler pulses. The Durchschaltbe conditions of the exclusive-OR gate <b>94</b> are while does not meet the first 100 microseconds, so that during this Time, the receiving and mixing stage <b>99</b> is not locked. Therefore, the receiver echoes due to those sending impulse of the transducer <b>17</b> record that the front reception Pulse on line <b>90</b> were sampled. After, 100 Microsecond period, the output signal of a monoflop <b>93</b> from, and the turn-on conditions of the gate <b>94</b> are met. This is a high signal at the output the gate <b>94</b> developed that the receiving and mixing stage <b>99</b> locks. At about this time ending the delay of Pulse generator and delay circuit <b>91</b>, and a B strobe is from the transducer <b>16</b> emitted.

From the output of the gate <b>94</b> Two switches <b>96</b> and <b>97</b> controlled. In the<b>Fig.</b> 12 position shown the switch is designed for operation without presetting, that is, for the operation in which the B-scan and Doppler signals not interleaved. During this operation, the output signal from the channel <b>1</b> via the switch <b>96</b> to the sample and hold circuit <b>106</b> transfer. The Off passage of the sample and hold circuit <b>106</b> is about switch <b>97</b> directly to the line <b>120</b> connected. This Signal is not processed, with the exception of the Sample and hold circuit <b>106</b> evoked scan and delay. If the Doppler signals are interrupted, is the output signal of the NOR gate <b>94</b> high and the switch <b>96</b> couples the line <b>117</b> with the sample and hold circuit <b>106</b>While the switch <b>97</b> the administration <b>120</b> with the line <b>116</b> connects.

The command or setting circuit containing the sample and hold circuits <b>106</b>. <b>107</b> and <b>109</b>, The output of circuit <b>106</b> is via line <b>115</b> to the input of circuit <b>107</b> connected and for illustrative purposes "B". The output of the circuit<b>107</b> is connected to "A" referred to and having an input terminal of a unit <b>108</b> coupled. The other input of the unit<b>108</b> is the management <b>115</b>, That is connected to "B". The unit<b>108</b> multiplies the signal on the line <b>115</b> 2 and subtracts "A" from the result. Therefore, the output signal on line <b>116</b> equal to 2B-A. In the setting circuit use conventional, commercially available components.

The timing for the sample and hold circuits <b>106</b>. <b>107</b> and <b>109</b> is recovered from the 10 kHz pulse frequency, is used by the Doppler transducer. This signal drives the circuit <b>109</b> directly. The signal is from a Verzö delay circuit <b>111</b> for controlling the sample-and- hold circuit <b>107</b> delayed. The output signal of the circuit<b>111</b> controls after further delay through tolerate the delay tion circuit <b>110</b> the sample and hold circuit <b>106</b>, The delay circuits <b>110</b> and <b>111</b> ensure the Transfer of the samples from a sample and hold circuit to the other for the development of the signal <b>2</b>BA on the line <b>116</b>,

With reference to <b>Fig.</b> 13, it is assumed that the there left of the line 100 shown on the audio signal management <b>120</b> is given. This corresponds to the signal in the channel <b>1</b> after signal sampling by the sample and hold circuit <b>106</b>, Next, assume that a B-scan pulse to be nested. The output of NOR gate <b>94</b> goes to H level, and the switch <b>96</b> and <b>97</b> turn into the opposite view Positions around. At this time, the output signal the sample and hold circuit <b>107</b> an "A", the portion or scan directly to the left of line 100 in <b>Fig.</b> 13. The output on line <b>116</b> 2B-A, the on the line <b>120</b> is given. As in<b>Fig.</b> to see 13 is set 2B-A the same Tonfrequenzsignalverlauf Direction (downward) continues, with the same general My pitch (waste) as that before the line 100th The <b>2</b>BA signal is applied to the sample and hold circuit <b>109</b> applied and forms the next input signal for the Ab palpable and hold circuit <b>106</b>, Therefore, the course is the Outputs of the unit <b>108</b> corresponding to the next output <b>122</b> in <b>Fig.</b> 13. This "predetermined" Doppler output signals are continued until the signal the output of the gate <b>94</b> falls and real Doppler data to the circuit <b>106</b> of the receiving and mixing stage <b>99</b> be applied.

The setting circuit described above provides a relatively simple linear specification or prediction. It is clear to the skilled person that complex algorithms ge for prescribing or predicting the Tonfrequenzverlaufs according to <b>Fig.</b> 13 used during those periods can, in which interrupted the correct Doppler echo are.

In the alternative described above Ausführungsbei game is the Doppler transducer for fixed periods under broken. The above system requires that a Doppler has been pulse being sent when a request for a B-sample pulse via the line <b>90</b> received. By tracking the actual time at which a Doppler pulse is sent, the waiting time for the Doppler transducer be reduced. For example, when a Doppler pulse<b>90</b> Microseconds before the request for a B-sample has been sent pulse, a B-scan in 10 Microseconds start, rather than a full period of 100 microseconds to service.