EP0000068B1 - Apparatus for ultrasonic imaging using dynamic focussing - Google Patents

Description

The invention relates to a device for the pictorial representation of a body with a transmitting device for emitting energy into the body, a converter for converting energy reflected from the body into electrical signals, which is divided into a plurality of separate elements, a plurality of memory registers Input of each memory register is connected to an associated converter element and a summing circuit for combining the information read from the memory registers in order to obtain an image signal.

Over the past two decades, ultrasound technology has become increasingly important in clinical diagnostics. Ultrasound technology has already been used in the fields of gynecology, neurology and cardiology, among other things, e.g. successfully used to visualize sabcutaneous blood vessels (including smaller ones).

There are significant reasons for the use of ultrasound technology in medicine: Ultrasound differs from other types of radiation due to its harmless effect on living systems because it is purely mechanical wave nature. The ultrasound technology makes it possible to obtain information that cannot be achieved by other methods, for example by examining with y and x-rays. Above all, the risk of injury when using ultrasound is much less than e.g. when using ionizing rays (y or x-rays). Ultrasound is mainly used as a pulse echo method in diagnostic technology, for which pulses of ultrasound energy are periodically emitted by a piezoelectric transmitter, e.g. based on lead-zirconate-titanate ceramic. Each small pulse of ultrasound energy is directed as a sound wave onto the patient's body, penetrating through various surface structures. If an interface of the body has an irregularity at which the phase of the ultrasound wave changes, part of the ultrasound energy is reflected back. After an ultrasound pulse is delivered, the ultrasound device is usually placed on reception in order to be able to convert reflected (or echo) signals from the body back into electrical signals. The time after which these echo signals return to the receiver is directly dependent on the distance between the reflection source and the speed of sound. The strength of the sound echo is also interesting because it provides information about the type of fault.

The echo of sound waves can be represented in different ways. On the one hand, there are devices with amplifiers with which the electrical signals corresponding to the received ultrasonic echo are increasingly applied to the vertically deflecting plates of a cathode ray tube. The output of a time generator is due to the horizontal deflection of the cathode ray tube. A constant repetition of the pulse / echo process, synchronized with the time generator, then leads to a still picture, so-called "A-scan", in which the time is proportional to the depth of penetration and vertical deflections signal existing disorder. The intensity of these vertical deflections is a measure of the intensity of the echo.

Another common type of pictorial representation of ultrasound waves is the so-called B-scan, in which the echo information corresponds to the usual television picture. d. H. the received sound echo signals are used to modulate the brightness of the screen per sampling point. This screen display is used specifically for devices in which the ultrasound beam is swung in the body, each intensity information occupying a scanning line on the screen and the successive positions in succession are used to display successive lines on the screen. With this technique, a transmitted light image is scanned in one plane and the resulting image can be viewed directly or stored by a photograph or magnetic storage tape.

The sound transducer of the devices described has a finite extent, on which the limited resolution of the image obtained from the ultrasound waves depends. It is also known that ultrasonic waves can be directed with suitable lenses as described in U.S. Patent No. 3,598,559 and / or by dividing the ultrasonic transducer into various small parts that are connected by different delay lines. One type of focusing can be achieved, for example, in that sound-absorbing components are formed with a multiplicity of rings of transmission elements lying concentrically one inside the other, which are connected via different delay lines. Because of the relatively low speed of sound, the path difference that the sound waves cross from the center of a transmitter to its edge zone on the way there and back via a theoretical focal point and back plays a major role if beam bundling is provided analogously to electromagnetic waves. The path difference between the short path from the focal point to the center of the transmitter to the path from the focal point to Transmitter edge must be compensated with delay means according to a double pass of the ultrasonic waves. Electrical delay lines on the way from the electrical exciter to the sound transducer have proven their worth.

It is also known to change the ultrasonic measuring depth by varying the delay lines (dynamic focusing). Non-changeable distortion lines only allow an ultrasound measurement with a fixed focal point, which can be adapted to different problems for examination by varying the delay lines. Finally, it must be noted that ultrasound waves stay longer in the body for deeper examination. An examination requires observation of the body at different depths. In the case of a more in-depth examination, the path difference between the central receiving point and peripheral zones is somewhat equalized, which must be taken into account by setting the delay lines accordingly. Because of the large number of delay lines, each of which must be controlled accordingly, the technical scope and use of such devices is very complicated.

An example of a device for dynamic focusing in an ultrasound imaging system can be found in the publication "CCD dynamically focused lenses for ultrasonic systems" from "CCD 75 proceedings of CCD applications conference naval electronics laboratory center, San Diego, California 1975 (29.-31. October) ". In this pre-publication it is proposed to use an ultrasound transducer consisting of several ring-shaped elements, each element being connected to a CCD memory. The ultrasound information is output serially into this memory and serial again and displayed on a screen. In order to achieve dynamic focusing, the clock frequency of each individual memory is varied in each case during the input and / or output of the signals into / from the individual memories in such a way that dynamic focusing is achieved by this variation. For this purpose, a separate voltage-controlled oscillator and a frequency multiplier are necessary for each memory. As expressly admitted in this publication, this requires a very large technical outlay, with the resulting costs and a corresponding space requirement.

The invention has for its object to provide an ultrasonic echo meter that enables dynamic focusing and is as simple as possible and consequently economically constructed and works trouble-free. An object of the invention is therefore seen primarily in significantly improving known devices.

This object is achieved in a device of the type described in the introduction by a first clock generator, which is assigned to each of the memory registers, a plurality of second clock generators, each of the memory registers being assigned a second clock generator with a different characteristic clock frequency, a time control circuit for controlling the Reading the signals from the elements into the assigned memory registers with the clock of the second clock generator and then reading out the stored information from each of the memory registers with the clock of the first clock generator.

Advantageous embodiments of the invention are characterized by the features listed in the subclaims.

An ultrasound imaging device, with which an ultrasound beam is emitted in a body for diagnosis, which is partially reflected back as an echo, often has an electroacoustic transducer with a multiplicity of elements which are arranged in concentric rings one inside the other in an area. Such an electroacoustic transducer is advantageously used simultaneously for emitting the ultrasonic waves and for receiving the reflected ultrasonic waves. The device according to the invention also has a multiplicity of register units, preferably memory registers of the so-called "CCD" type (charge transport storage register) which operate in an analog manner. Each register is coupled to a converter element. A clock generator is connected to each register and generates signals with a first clock frequency. A large number of further clock generators are also provided, which are likewise connected to the analog memories. The second type of clock generator delivers clocks with different predetermined clock frequency. In addition, time-dependent clocks are provided which control the operation of the first and second clocks, so that the memories are alternately loaded with the frequency of the second clocks and then read out with the frequency of the first clocks. Finally, an electrical connection is provided for transporting the read signals to an imaging system.

In the present invention, the delay line required for each converter element is replaced by a predetermined frequency of the second clock generator. With the respective clock frequency, a line is read into a memory with a corresponding delay. The signals thus read in with a delayed clock frequency can be read out from the memory with a common frequency for all segments.

Another embodiment of the invention is seen in that opposite to In the previously described reading-in method, the memories are loaded with a common frequency and the delay required for each segment is only taken into account when reading out with a different frequency. In addition, the clock frequency can be matched to the respective segment when reading in and reading out.

• Fig. 1 ein Gerät der Erfindung im Einsatz,
• Fig. 2 im Querschnitt einen Meßkopf des Gerätes mit einem Blockschaltbild der zugehörigen Auswertelektronik,
• Fig. 3 einen Teil der elektrischen Schaltung in Blockform, die zur dynamischen Fokussierung vorgesehen ist,
• Fig. 4A und B Darstellungen, die hilfreich sind, um die Funktion der Schaltung aus Fig. 3 zu erläutern,
• Fig. 5 ein Blockschaltbild einer anderen Schaltung für die Erfindung,
• Fig. 6A und B die zugehörigen Darstellungen zur Erklärung der Funktion der Schaltung nach Fig. 5,
• Fig. 7 eine weitere Ausführung der erfindungsgemäßen Schaltung in Blockform,
• Fig. 8 eine zum Verständis von Fig. 7 geeignete graphische Darstellung.

Further advantageous embodiments of the inventions are described below with reference to the schematically illustrated drawing. Show it

• 1 is a device of the invention in use,
• 2 in cross section a measuring head of the device with a block diagram of the associated evaluation electronics,
• 3 shows part of the electrical circuit in block form, which is provided for dynamic focusing,
• 4A and B representations that are helpful to explain the function of the circuit of FIG. 3,
• 5 is a block diagram of another circuit for the invention;
• 6A and B the associated representations for explaining the function of the circuit of FIG. 5,
• 7 shows a further embodiment of the circuit according to the invention in block form,
• FIG. 8 shows a graphical representation suitable for understanding FIG. 7.

In Fig. 1 the external dimensions of a scanning device according to the invention are shown in comparison with an object. The control panel 10 contains a screen 11, for example a cathode ray tube, or a suitable front panel. In addition, a video tape recorder or other storage e.g. based on photographic signals (screen copier), contained in the control panel 10 to provide the signals for displaying an image. The control panel 10 also contains a power supply and parts of the circuit for generating timing signals and for driving the scanning sound level in the measuring head 50. The measuring head 50 (or probe) is connected to the control panel 10 with an electrical line 48. The measuring head 50 of the present exemplary embodiment is essentially cylindrical / shaped and has, in the vicinity of one end, a scanning window 50 which, for example, consists of an elastically flexible material such as silicone rubber. To handle the device, the measuring head 50 is brought into a position to be held in the hand of the operator, so that the scanning window 50 on the object to be scanned resiliently flexible material, such as silicone object, is to be scanned, for example, the area around a person's heart. Of course, the measuring head can also be used to measure other parts of the body or other objects to which it should be directed with a handle.

2, the measuring head 50 is shown in cross-section, to which associated parts of the evaluation electronics are connected, which can be arranged partly in the measuring head 50 and partly in the control panel 10. The housing of the measuring head 50 includes a front sound guiding chamber 52, which contains a liquid, and a rear sound measuring chamber 53, which contains part of the electronics. Both chambers 52 and 53 have a cylindrical shape with the same diameter, so that they can be assembled into a cylinder with the aid of a tube 54 which has an annular extension 55 on its outside. The (inner) tube 54 carries a flat sound transducer 80 and a sound collecting lens 90, from which the two housing parts are separated from one another (cf. US Pat. No. 3,958,559). The scanning window 51 is located at the end of the chamber 52. An attachment is provided around the window opening, on which an elastically flexible membrane 56, for example silicone rubber membrane, is fitted. The front sound chamber 52 is filled with a liquid 57, for example water. The membrane 56 should be so elastic that it lies smoothly with the measuring head on the surface of the body to be measured in order to keep disturbing reflections of sound waves at the transition point between the liquid of the device and the object as low as possible.

A flat, e.g. Metallic, sound-reflecting scanning device 70 is arranged in the liquid 57 between the sound lens 90 and the scanning window 51. Of course, the surface of the non-curved scanning device can be curved and focus or scatter even reflected sound waves. The scanning device 70, which is referred to below as a scanning sound mirror or simply a scanning mirror, is fastened to an axis 71 lying perpendicular to the plane of the drawing, which can be passed through the housing wall of the front sound guide chamber 52, in order to be connected from the outside with a small electric motor 72, which Hind float generated to be operated.

The electroacoustic transducer 80 is divided into a plurality of elements which lie in concentric rings around a central element in one plane. In the illustration, only three elements, labeled 81, 82 and 83, are shown instead of a confusing variety. Of course, the electroacoustic transducer has many more elements. The elements of the electroacoustic transducer 81 to 83 are connected to an electrical pulse generator 120, from which they can be excited in a known manner to emit ultrasound. The sound transducer elements are also connected to the new circuit for dynamically adjusting the focus according to the invention.

The circuit designated 130 preferably works only when receiving sound waves and forwards electrical signals in accordance with the reflected echo signals from the ultrasound for imaging on a screen. Pre-amplifications and amplifiers, which are not shown in detail in the figure, may also be present in this circuit. The output of the circuit 130 for dynamically focusing the focal point is connected to a screen 11 and a further receiver 16), which is used for storing the television picture by video equipment. A particularly advantageous circuit for amplifier control is described in more detail in US Pat. No. 4,043,181. With such an amplifier control, later arriving echo signals are amplified in accordance with their weakening experienced during passage through the body tissue.

The timing circuit 170 is provided to generate pulses at equal intervals with which the system is synchronized; the pulses of the timing circuit 170 are alternately fed to the pulse generator 120 and the dynamically focusing pulse receiver 130 and furthermore from the scanning mirror drive and the circuit for deflecting the electron beam 180, so that ultrasonic pulses are alternately emitted and received and that the movement of the mirror drive and the vertical and horizontal deflection of the electron beam of the cathode ray tube 11 can be coordinated.

Broadly speaking, the circuit works as follows: a trigger signal from the timing circuit 170, conducted via the connection 178, stimulates the pulse generator 120 to generate pulses which are transmitted to the elements of the electroacoustic transducer 80, concentric ring elements of ultrasonic transducers become Alignment of an ultrasound beam on a focal point, as is known, excited via delay lines. A further beam alignment is possible through the lens 90. The ultrasound beam introduced into the body to be examined via the scanning mirror 70, the area of which is represented by dotted lines in the figure, is received again as an echo after the sound has been released by the subsequent switchover of the device to reception. The electroacoustic transducer 80 now converts the echo signals reflected back via the scanning mirror into electrical impulses in the opposite direction.

After processing by the circuit 130, the electrical signals are made visible on a screen 11. The screen shows a section in the direction of the ultrasound wave sent through the object, the so-called B-scan image. The second dimension of the image is the swivel range of the ultrasonic wave, which is obtained by moving the scanning mirror 70 back and forth relatively slowly in the direction of the double-sided arrow 7.

FIG. 3 shows a block diagram of the electrical circuit for dynamic focusing for the circuit 130, which is connected to the elements of the ultrasound transducer 80. A memory 131 to 133 is connected to each element 81 to 83. The memories are preferably components that operate analogously as so-called CCD components. The output of this memory is applied to an adder 147, the output of which is at the input of gate 148. The output of the gate 148 is connected to the screen 11 via a filter 149, through which impressed clock pulses are filtered out.

Clock generators 141, 142 and 143 are each assigned to a sound converter 81-83, on which they generate clocks with which information is fed into the registers 131-133. The clock generator 141 generates a predetermined frequency F _o , the clock generator 142 a predetermined frequency Y Fa + LlF1 and the clock generator 143 a predetermined frequency F ₀ + ΔF ₂ . The outputs of the clock generators 141-143 are connected to the corresponding register inputs via AND gates 151, 152 and 153, through which the reading into the memories is controlled. The second input of each AND gate 151-153 is at the output of the switch 154. The output of the AND gate 151 is connected, in addition to the input of the memory 131, to the counter 155, which counts pulses with a frequency F _o .

In the example of the present invention, each register 131-133 has n memory locations, and accordingly the counter 155 counts up to the number n at a maximum Timing circuit 170 is turned on. The counting signal described in this way can advantageously be used to switch the device from transmission to reception. The clock frequency of the timing circuit 170 is also set such that only echo waves are received in the intended measuring range of the measuring depth in the body.

A pulse generator 135 supplies pulses of frequency F _c , which are connected to each memory 131 to 133, and after which the information is read from the memories. The output of generator 135 is connected to the memories via gate 139. The gate 139 is also connected to a counter 136 which counts a maximum of m digits. Its output signal sets the counter 136 to 0 when the maximum permissible pulses m are reached and switches the switch 137 off, which is switched on in response to a signal from the counter 155. The output signal of switch 137 is present at AND gate 139 and at gate 148.

• Nach einem Signal der Zeittaktschaltung 170 öffnet sich der Schalter 154, der seinerseits die Gatter 151-153 öffnet. Somit können elektrische Signale von den Elektroakustischen Wandlern 81-83 in den Speichern 131-133 mit der jeweils vorgewählten Taktrate der Taktgeneratoren 141-143 eingelesen werden, bis n Takte, die vom Zähler 155 mitgezählt werden, gespeichert, sind. Der Speicher 131 wird dabei mit der niedrigen Frequenz F_o aufgefüllt, bis der Zähler 155 m Takt gezählt hat, nach denen er sich selbst auf 0 setzt, den Schalter 154 schließt und den Schalter 137 öffnet. Der Schalter 154 schließt auch die Gatter 151-153 und beendet somit den Speichervorgang, dem nun, durch den Schalter 137 ausgelöst, das Auslesen folgt, indem die Gatter 139 und 148 geöffnet werden. Die Information aus den Speichern 131-133 gelangt über Addierer 147 und Gatter 148, sowie Filter 149 auf den Bildschirm 11. Von dem Filter 149 werden aufgeprägte Taktfrequenzen wieder entfernt. Das Auslesen wird mit einem Zähler 136 kontrolliert, der die beim Auszählen aufgeprägten Impulse vom Impulsgenerator 135 bis zu einer Zahl maximal m zählt, wobei im vorliegenden Fall angenommen werden soll, daß n=m ist, wonach der Zähler 136 den Schalter 137 wieder schließt und Gatter 139 und 148 wieder sperrt.

The scarf shown in detail in Fig. 3 Tung 130 works broadly as follows:

• After a signal from the timing circuit 170, the switch 154 opens, which in turn opens the gates 151-153. Thus electrical signals from the electroacoustic transducers 81-83 can be read into the memories 131-133 at the respectively preselected clock rate of the clock generators 141-143 until n clocks, which are counted by the counter 155, are stored. The memory 131 is filled with the low frequency F _o until the counter has counted 155 m clock, after which it sets itself to 0, closes the switch 154 and opens the switch 137. The switch 154 also closes the gates 151-153 and thus ends the storage process, which is now triggered by the switch 137 and is followed by the reading by the gates 139 and 148 being opened. The information from the memories 131-133 reaches the screen 11 via adder 147 and gate 148, as well as filter 149. Imprinted clock frequencies are removed from the filter 149 again. The reading is controlled with a counter 136 which counts the impulses imposed during the counting from the pulse generator 135 to a maximum number of m, in the present case it should be assumed that n = m, after which the counter 136 closes the switch 137 and Gate 139 and 148 locks again.

A delay in the ultrasound pulses is therefore only simulated after they have been received by the fact that the signals supplied by the ultrasound transducer are read in with a higher clock frequency rising towards the edge of the transducer. As a result, the path difference to the edge visible from FIGS. 4A and B is compensated.

When using the frequencies F _o , F ₀ + ΔF ₁ and F _o + ßF ₂ , the difference to the central converter element is n times ΔT ₁ and n times AT ₂ (where F = 1: T). The delay is thus set directly by the clock generators 141-143.

Since the difference in the delay depends on the penetration depth (cf. FIGS. 4A and B, in which measurement at different focal points Z a to Z c is shown), the difference in the delay of the adjacent transducer elements has to be set inversely to the penetration depth Focusing lens 90 (FIG. 2), the delay effect of which, however, should not be greater than the minimum delay at the maximum penetration depth. If measuring devices with an arbitrarily large penetration depth are to be developed, then the focusing lens 90 would have to be omitted.

FIGS. 4A and 4B exemplarily show the path and resulting transit time differences for two different focal points Za and Zb. It can be seen from this figure that sound waves from the intended focal point Za to the first ring take 2.5 µsec and to the second receiver ring 5.0 µsec longer than to the center. With a greater depth of penetration, the difference that ultrasonic waves require from the focal point to the outer receiver zones is correspondingly smaller (FIG. 4B).

If one assumes that the memories 131-133 are designed with 1000 memory locations and that the counter 155 counts to the number 1000, if one continues from a clock frequency F _o = 20 megahertz with a shift OF, 1.05 megahertz and OF ₂ = 2.22 megahertz, then clock generators 141-143 deliver pulses with a frequency of 20 megahertz, 21.05 megahertz and 22.22 megahertz.

• Die Zeittaktschaltung 170 gibt das Einschaltsignal etwa zu dem Zeitpunkt, wenn das zuerst eintreffende Signal vom Punkt Za in Segment 81 aufgenommen wird. Die taktweise Speicherung der Signale im Speicher 131 dauert bei der Frequenz von 20 Megahertz 0,05 µsec pro Takt des Taktgebers 141. Der gesamte Eintaktvorgang bei 1000 Speicherplätzen dauert dann also 50 µsec. Der Zähler 155 zählt diese 1000 Takte genau mit, bis der Speicher vollständig aufgefüllt ist, so daß auf dem zuletzt aufgefüllten Speicherplatz ein Echoinformation vom Brennpunkt Za vorhanden ist. (Die in dem dargestellten bevorzugten Ausführungsbeispiel zur Anwendung kommenden Ladungstrans- portspeiche.r -arbeiten dergestalt, daß die am einen Ende eingegebene Information während des Speichervorganges durchläuft, in der Darstellung der Fig. 3 beispielsweise von rechts nach links, so daß die am Eingang des Speichers zuerst eingegebene Information nach dem Speichervorgang dem Ausgang des Speichers am nächsten abgespeichert ist und die folgenden Informationen sich daran, in der Darstellung der Figur von links nach rechts anschließen). Der Speichervorgang in den Speichern 132 und 133 wird nun von den Taktgebern 142 bzw. 143 mit den höheren Frequenzen 21,05 Megahertz und 22,22 Megahertz getaktet, so daß das Einspeichern pro Speicherplatz 0,0475 bzw. 0,045 µsec dauert. Das Einlesen der Signale auf die 1000 Speicherplätze dauert demzufolge 47,5 µsec bzw. 45 µsec.

In this example, the device works as follows:

• The timing circuit 170 outputs the switch-on signal approximately at the point in time when the signal arriving first is picked up from the point Za in segment 81. The clock-wise storage of the signals in the memory 131 takes 0.05 microseconds per clock cycle of the clock generator 141 at the frequency of 20 megahertz. The entire in-clocking process with 1000 memory locations then takes 50 microseconds. The counter 155 counts these 1000 clocks exactly until the memory is completely filled, so that there is echo information from the focal point Za in the last filled-up memory location. (The charge transport storage devices used in the preferred exemplary embodiment shown work in such a way that the information entered at one end passes through during the storage process, for example in the illustration in FIG. 3 from right to left, so that the information at the input of the The information entered first after the storage process is stored next to the output of the memory and the following information is connected to it in the representation of the figure from left to right). The storage process in the memories 132 and 133 is now clocked by the clock generators 142 and 143 with the higher frequencies 21.05 megahertz and 22.22 megahertz, so that the storage takes 0.0475 and 0.045 microseconds per memory location. The reading of the signals into the 1000 memory locations therefore takes 47.5 µsec or 45 µsec.

As mentioned, the read-in process is ended by the switch 154 when the counter 155 has counted a thousand pulses from the clock generator 141, that is to say after 50 μsec in the example. As a result, the memories 132 and 133 are read in longer than is necessary to occupy the memory locations. Since the storage process ends at the same time as in the memory 131, the additional information from the initial phase of the storage process is deleted after the storage space on the output side (leftmost in the figure) is occupied. A simple consideration shows that after the memory is finished process, the information coming from the focal point Za is also stored in the memories 132 and 133 in the memory location closest to the memory output. The deleted information corresponds exactly to the difference in the transit time of the sound wave from the focal points Za to the outer rings 82 and 83 of the sound converter 80.

FIG. 4B shows a focal point Zb which is further away from the sound converter 80 and whose distance from Za corresponds to a transit time of 40 microseconds. The signal impinging on the converter element 81 from this focal point is accordingly stored 40 p.sec after the start of the reading process in the memory 131, specifically, counted by the memory output, in the 800th memory location, that is to say 200 locations from the memory input. As a simple calculation shows, the corresponding memory space in memories 132 and 133 contains signals due to the increased clock frequencies when reading in, which are 0.5 µsec (200x0.0025) or 1.0 µsec (200x0.005 _j usec) later the associated converter rings 82 and 83 have arrived. This difference corresponds, as shown in FIG. 4B, exactly to the transit time difference of the sound waves from the focal point Zb to the rings 82 and 83. The same reasoning can be made for each focal point which lies between Za and Zc, where Zc marks the focal point that the ultrasound beam is focused due to the lens 90 without additional electronic delay.

The electrical shift of the focal point predetermined by the different clocking of course only takes effect when the memories are read out again at the same frequency. Since the memory location first read out, which is closest to the memory output, as the above considerations show, contains the signal corresponding to the focal point Za in all memories 131 to 133 and the last memory location contains the signal corresponding to the focal point Zc, the signals also arrive at the adder 147 at the same time and accordingly to the screen 11. That is, the image is dynamically focused for the entire area between the focal points Za and Zc. An even greater shift can be achieved if reading is carried out with clock frequencies that change in reverse order. This is relatively simple in terms of circuitry, because the control required for this is already provided for recording and storing the signals. A corresponding circuit is shown in Fig. 7 and will be described below.

A particularly advantageous device of the invention is seen in the fact that components for setting the number of cycles of each register are operably connected by a common drive shaft in such a way that they simultaneously determine the number of cycles in proportion to the distance between the focal point and in relation to the change in the number of cycles of the adjacent memories.

It should be noted in this connection that the frequencies of the clocks 141 to 143 are different, but each is constant in the normal embodiment of the invention. Such an embodiment is generally completely sufficient to obtain a sufficiently sharp dynamic focus. The additional, common, slight change in the clock frequencies makes sense only under certain circumstances, in order to enable even better correction of even the smallest misfocusing.

In a further embodiment of the invention, an electrical circuit with corresponding block symbols is shown in FIG. 5, in which the corresponding components are provided with reference symbols which differ from the reference symbols in FIG. 3 by a 2 in the hundreds if they fulfill corresponding tasks .

• Nach einem Signal des Zeitgenerators 170 öffnet sich der Schalter 237, der seinerseits das Gatter 239 öffnet. Somit können elektrische Signale von den elektroakustischen Wandlern 81 bis 83 in die Speicher 231 bis 233 mit der Taktrate Fc des Taktgenerators 235 eingelesen werden, bis n Takte, die vom Zähler 236 mitgezählt werden, gespeichert sind. Die Speicher 231 bis 233 werden dabei mit der Frequenz Fc aufgefüllt, bis der Zähler 236 n Takte gezählt hat, nach denen er sich selbst auf 0 setzt, den Schalter 237 schließt und den Schalter 254 öffnet. Der Schalter 237 schließt auch das Gatter 239 und beendet somit den Speichervorgang, dem nun, durch den Schalter 254 ausgelöst, das Auslesen folgt, indem die Gatter 251 bis 253 und 248 geöffnet werden. Die Information aus den Speichern 231 bis 233 gelangt über Addierer 247 und Gatter 248, sowie Filter 249 auf den Bildschirm 11. Von dem Filter 249 werden aufgeprägte Taktfrequenzen wieder entfernt. Das Auslesen wird mit einem Zähler 255 kontrolliert, der die beim Auszählen aufgeprägten Impulse vom Impulsgenerator 235 bis zu einer Zahl maximal m zählt, wobei m gleich n ist, wonach der Zähler 255 den Schalter 254 und die Gatter 239 und 248 wieder schließt.

The circuit 130 shown in detail in FIG. 5 operates on the whole as follows:

• After a signal from the time generator 170, the switch 237 opens, which in turn opens the gate 239. Electrical signals from the electroacoustic transducers 81 to 83 can thus be read into the memories 231 to 233 at the clock rate Fc of the clock generator 235 until n clocks, which are counted by the counter 236, are stored. The memories 231 to 233 are filled with the frequency Fc until the counter 236 has counted n clocks, after which it sets itself to 0, closes the switch 237 and opens the switch 254. The switch 237 also closes the gate 239 and thus ends the storage process, which is now triggered by the switch 254 and is followed by reading out by opening the gates 251 to 253 and 248. The information from the memories 231 to 233 reaches the screen 11 via adder 247 and gate 248, as well as filter 249. Imprinted clock frequencies are removed again from the filter 249. The reading is controlled with a counter 255, which counts the impulses impressed during counting from the pulse generator 235 up to a maximum number of m, where m is n, after which the counter 255 closes the switch 254 and the gates 239 and 248 again.

5 differs from that described in FIG. 3 in that the clocks 241 to 243 with their different frequencies, which, as shown in the figure, from F _o for the clock 241 via Fo + L1F, rise of the clock 242 F _o + oF ₂ for the clock 243 may be used for reading instead for reading the information. The clock 241 is connected to the memory 233, which is assigned to the outermost ring 83 of the sound transducer, ie the reading takes place in this embodiment with frequencies increasing from the outermost sound transducer ring 83 to the innermost sound transducer ring 81. In contrast, in this embodiment the reading takes place with the aid of a clock 235 connected to all memories 231 to 233, ie with the same frequency for all memories.

In addition, fixed delay elements 201 and 202 are connected to the read-in lines of the memories 231 and 232 located further inside. These delay the reading in of the signals from the transducer rings 82, 81 located further inwards by fixed amounts increasing from the outside in.

5 is explained in more detail with reference to FIGS. 6A and 6B. FIG. 6A shows the imaging relationships at a relatively obvious focal point Zq, FIG. 6B at a farther away focal point Zr. As shown in FIG. 6A, the delay D ₁ in the middle transducer element 81 corresponds to the transit time difference t _{2 of} the ultrasound from the focal point Zq to the middle transducer element 81 compared to the transit time from the focal point Zq to the outermost transducer element 83. The fixed delay D ₁ in the read-in line of the transducer element 82 corresponds to the difference of the corresponding runtime differences between the runtimes t ₂ and t assigned to the elements 83 and 82.

Because of these fixed delays, a focal point Zq is fixed, which is now dynamically adapted for different focal points further away by reading out the signals from the memories 231 to 233 with different frequencies. The processes are basically the same as described above, the difference essentially being that by reading out at different frequencies, the signals of the innermost transducer element are accelerated the further the focal point is. As a result, the fixed delay D ₁ is compensated to the extent necessary so that dynamic focusing is achieved here as well.

In Fig. 7, an embodiment is shown in which the clock frequency of the memories 331 to 333 differs progressively both when reading in and when reading out, the highest frequency F, + AF, of the clock generator 343, the outermost transducer element 83 with the associated memory 333 is assigned, while the lowest clock frequency F ₀ -ΔF _{1 of} the clock generator 341 is assigned to the central converter element 81 during reading. This can be clearly seen from the figure. The clock 342 has the corresponding average frequency F _o .

The assignment is reversed when reading out, i.e. the highest frequency of the clock generator 343 controls the reading out from the memory 331 assigned to the central converter element 81. The circuit shown with the gates 351 to 353 and 361 to 363 in connection with the switch 354 makes the reading and with the switch 337 the reading out controlled.

The flip-flop 355 controls the switching process with the aid of the counter 336, which counts the signals of the clock generator 341 when reading in and those of the clock generator 343 when reading out. The gates 358 and 359 together with the inverter 357 also serve to control the reading and reading process in an easily recognizable manner. When the switch 354 is turned on by a signal from the timing circuit 170, as in the other embodiments, the flip-flop 355 is simultaneously set to logic 1 and the AND gate 358 is thus opened. If the counter 336 has reached its highest counter reading N when it is read in, it outputs an output signal and resets itself. Since the AND gate 358 is open, the counter output signal goes to the switch 337, thereby turning on the readout operation by opening the AND gates 361 to 363 and the gate 348. At the same time, the read-in switch 354 is closed and the flip-fop 355 is reset. A logic 0 is thus present at the output of the flip-flop 355, so that the AND gate 359 is opened via the inverter 357. If, when reading the counter 336 when counting the signals of the clock generator 343, the counter reading N is reached again, it in turn generates an output signal which switches the switch 337 off via the opened AND gate 359 and thus ends the reading.

In the embodiment shown in FIG. 7, fixed delay elements with delays D, and D _{2 are} provided, which on their own bring about focusing on a central focal point.

In the embodiment of Fig. 7, both of the forms of deceleration described in connection with Figs. 3 and 5 are applied on opposite sides of the center focus. When reading in, the signals are more and more delayed from sound transducer elements located to the center, because they are read in at an increasingly lower frequency, so that, for example, the information which comes to rest in the last stage of the allocated memory comes from the dynamic focusing device has been delayed to a maximum. The relative delay due to the read-in process decreases increasingly for the earlier stages (similar to the situation in the embodiment according to FIG. 3), as is shown by the dashed line "A" in FIG. 8. The reverse situation applies to the reading process (similar to the embodiment according to FIG. 5). This is in Fig. 8 represented by the dashed line "B". The total delay by the dynamic focusing system is shown in FIG. 8 by line "C" (equal to AB). Approximately in the middle of the memory (which corresponds approximately to the center of the depth range of the ultrasound device), the delay is 0 and only the fixed delay devices mentioned are effective.

Claims (10)

1. Apparatus for the pictorial representation of a body with

-a transmitter device (130, 80) for the emission of energy into the body,

- a transducer (80), for the conversion of energy reflected from the body into electrical signals, which is subdivided into a plurality of separate elements (81-83),

-a plurality of memory registers (131-133), the input of each memory register (131-133) being connected with an associated transducer element (81-83) and,

-an integrator hookup (147) for the compilation of the information read off from the memory registers (131-133) in order to obtain a pictorial signal, characterised by,

-a first clock generator (135) which is associated with each of the memory registers (131-133),

- a plurality of second clock generators (141-143), each of the memory registers (131-133) being associated with a second clock generator (141-143) with a different characteristic pulse frequency,

-a time-control circuit (170, 136, 137, 154, 155) for controlling the input of the signals from the elements (81-83) into the associated memory registers (131-133) with the pulse of the second clock generators (141-143) and of the subsequent read out of the stored information from each of the memory registers (131-133) with the pulse of the first clock generator (135).

2. Apparatus for the pictorial representation of a body with

a transmitter device (130, 80) for the emission of energy into the body,

-a transducer (80) for the conversion of energy reflected from the body into electrical signals, which is subdivided into a plurality of separate elements (81-83),

-a plurality of memory registers (231-233), the input of each memory register (231-233) being connected with an associated transducer element (81-83) and,

- an integrator hookup (247) for the compilation of the information read off from the memory registers (231-233) in order to obtain a pictorial signal, characterised by

- a first clock generator (235) which is associated with each of the memory registers (231-233),

- a plurality of second clock generators (241-243), each of the memory registers (231-133) being associated with a second clock generator (241-243) with a different characteristic pulse frequency,

-a time control circuit (170, 236, 237, 254, 255) for controlling the input of the signals from the elements (81-83) into the associated memory registers (231-233) with the pulse of the first clock generator (235) and of the subsequent read out of the stored information from each of the memory registers (231-233) with the pulse of the second clock generators (241-243).

3. Apparatus for the pictorial representation of a body with

-a transmitter device (130, 80) for the emission of energy into the body,

- a transducer (80), for the conversion of energy reflected from the body into electrical signals, which is subdivided into a plurality of separate elements (81-83),

-a plurality of memory registers (331-33), the input of each memory register (331-33) being connected with an associated transducer element (81-83) and,

- an integrator hookup (347) for the compilation of the signals read off from the memory registers (331-33) in order to obtain a pictorial signal, characterised by,

-a plurality of clock generators (341-343) with different characteristic pulse frequencies,

- time-control device (170,336, 337, 351-355, 357-359, 361-363) for controlling the input of the signals from the elements (81-83) into the associated memory registers (331-333) with different pulse frequencies, which are produced by the different clock generators (341-343), whereby a first correlation exists between the clock generators (341-343) and the memory registers (331-333) and of the subsequent read out of the stored information from the memory registers (331-333) with different pulse frequencies, which are produced by the different clock generators, whereby there exists a secondary correlation, different from the first, between the clock generators (341-343) and the memory registers (331-333).

4. Apparatus according to one of claims 1-3, characterised in that ultrasonic energy is used.

5. Apparatus according to one of claims 1-4, characterised in that the energy transducer (8) consists of a central element (81) and several ring-shaped elements (82, 83) surrounding this.

6. Apparatus according to claim 5, characterised in that one of the clock generators (141-143; 341-343) which, in the case of the input is associated with the central element (81) has a lower characteristic pulse frequency than the clock generators (142, 143; 342, 343) associated with the ring-shaped elements (82, 83).

7. Apparatus according to claim 6, characterised in that the clock generators (242, 243; 342, 343) associated with the ring-shaped transducer elements (82, 83) have an increasingly higher characteristic pulse frequency.

8. Apparatus according to claim 5, characterised in that one of the clock generators (241-243; 341-343) which, in the case of the read out is associated with the central element (81) has a higher pulse frequency than the clock generators (242, 243; 342, 341) associated with the ring-shaped elements (82, 83).

9. Apparatus according to claim 8, characterised in that the clock generators (242, 243; 342, 341) associated with the ring-shaped transducer elements (82, 83) have an increasingly lower characteristic pulse frequency.

10. Apparatus according to one of claims 1-9, characterised in that the memory registers (131-133; 231-233; 331-333) are analogue registers of the charge transfer type (CCD memories).

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