JPH0452040B2 - - Google Patents

Description

An ultrasonic beam generating/receiving device characterized in that it comprises means 430, 500 for directing the beam. 2. Means 43 for defocusing and delaying the electrical pulses sent towards and received from the transducer elements 200 in the active group 220;
0 and arranged to delay the pulse coming from each transducer element in proportion to the distance between that transducer element and the center of the active group. The ultrasonic beam generating/receiving device described above. 3. The means for connecting the active groups comprises a matrix switch 440, the means for sequentially changing the transducer elements within the active group comprises a read-only memory 460, and an output terminal of the read-only memory 460 connects the switch and the read-only memory. 3. The ultrasonic beam generating/receiving device according to claim 1 or 2, wherein the ultrasonic beam generating/receiving device is connected to operate a sequence circuit 470 connected to sequentially address. 4. The defocusing means comprises a negative lens 500 arranged in the path of the ultrasound energy emitted by the transducer elements 200 of the active group 220. Ultrasonic beam generation and reception equipment.

[Detailed description of the invention]

The present invention includes a plurality of ultrasound transducer elements arranged along a curved line to generate and/or receive a scanned beam of ultrasound energy, each ultrasound an array of sonic transducer elements oriented to direct ultrasound energy toward the center of the curvature and receive ultrasound energy coming from the center of the curvature; and output electrical pulses toward the ultrasound transducer elements; means for outputting electrical pulses and means for receiving electrical pulses from the ultrasound transducer elements; means for connecting the group of active transducer elements to the means for outputting electrical pulses and the means for receiving electrical pulses, the active elements means for the group to comprise a preselected number of adjacent transducer elements in the array, the preselected number being greater than or equal to two and less than the total number of transducer elements in the array; ; an ultrasonic beam generating/receiving apparatus comprising means for sequentially changing the transducer elements in the active group to gradually shift the active group along a curvature; It is possible to image organs within a human body using a device that emits pulses of ultrasound energy into the human body and detects the echoes that return as the ultrasound energy reflects off tissue boundaries and other discontinuities within the body. It is also possible to grasp the characteristics of organs using other methods. Such devices typically focus ultrasound energy into a relatively narrow beam that is delivered into the human body. The internal structure of the human body is visually displayed or mapped using electrical signals that define the position and direction of the ultrasonic beam with respect to the human body, as well as the relative arrival time and amplitude of the echo. However, controlling the direction of the ultrasound beam is often left to the medical technician's manual intervention (typically by manually moving the head of the probe in a pattern over the area of the body desired to be viewed). Although this is sufficient for imaging, manually moving the probe typically takes a considerable amount of time and does not allow real-time imaging of rapidly moving human organs (e.g., moving heart valves). .
Therefore, ultrasonic imaging devices that display such rapidly moving human body organs in real time use electromechanical or electronic means to switch the position and direction of the beam relative to the human body. Moving this ultrasonic beam relative to the human body is achieved by arranging a large number of transducer elements in a linear array and operating these transducer elements in sequence. This can be effectively implemented in which an area of the human body is scanned with a series of substantially parallel ultrasound beams. This type of device is described in US Pat. No. 3,013,170. Alternatively, it is also possible to perform a so-called "sector-scan" by swinging the ultrasound beam around a single origin. This sector scanning is therefore particularly useful. This is because if the lid is closed, the ultrasonic beam can be directed to the back side of the ribs through the gap between the ribs, and the inside of the thorax can be scanned. This fan-shaped scanning has been used in the past, but in the prior art, one or more transducers are rapidly rotated around a rotating axis, or the transducer is fixed, and the transducer is fixed. Fan scanning has been achieved by reflecting the energy output from a transducer on a rotating ultrasonic reflector, or by sequentially operating individual transducer elements arranged in a curved array. German Published Patent Application No. 2818915 describes operating the individual transducers on the last curved transducer array individually to obtain a sector scan. The lateral spatial resolution of a device that sequentially operates each transducer element in such an ultrasonic transducer array is related to the dimensions of each transducer element in the array, and the resolution is To increase the height, the transducer element must be made smaller. However, on the other hand, the amount of ultrasonic energy output from each transducer element is limited by its dimensions, and the S/N ratio of the reflected ultrasonic echoes is necessarily lower than the ultrasonic energy emitted toward the human body. Since it depends on the amount of energy, if you try to make each transducer element small and operate them one by one for scanning, the S/N ratio will inevitably deteriorate. Another disadvantage is that emitting a beam of ultrasonic energy from a single small ultrasonic transducer element causes diffraction phenomena that cause the beam to spread out. For this reason, the device described in DE 2818915 passes the ultrasound beam through a small window to reduce its lateral dimensions, which further reduces the amount of energy in the beam. It has the disadvantage of being smaller. Thus, in the prior art, the amount of energy in the beam produced by a flat linear array is increased by simultaneously operating a group of adjacent transducer elements. In this case, means are provided for stepping the operative transducer elements along the array, resulting in high resolution and high S/N.
The ratio was obtained. However, although this technique is good when scanning with a parallel beam using a transducer array in which transducer elements are arranged in a straight line, in the case of a curved array, a group of adjacent transducer elements are simultaneously scanned. In operation, the disadvantage is that the ultrasonic beam essentially focuses at the center of the array arc, making it impossible to obtain a fan-shaped scan with high resolution. The object of the invention is a device of the type mentioned above, which
Moreover, it is an object of the present invention to provide an apparatus that can operate a group of adjacent transducers simultaneously without generating a focused ultrasound beam. The method is characterized by means for defocusing the ultrasound energy generated and received by the transducer elements in the active group and for directing the ultrasound energy into a substantially parallel beam. The invention will be explained with reference to the drawings. FIG. 1 shows a conventionally known linear ultrasound transducer array 110. Here, individual ultrasonic transducer elements 100 are arranged in a straight line 1
They are arranged in a line along 01. An electrode 102 is separately attached to each ultrasonic transducer element of this linear ultrasonic transducer array, and these electrodes 102 are connected to an electronic circuit (not shown) to sequentially operate each transducer element. The ultrasonic beam source can be moved along the straight line 101 by moving the ultrasonic beam source. FIG. 2 illustrates the use of the linear ultrasound transducer array 110 of FIG. A group of mutually adjacent transducer elements 111
simultaneously operate to generate a beam of ultrasonic energy 11.
2 is sent into the human body 113. The linear ultrasound transducer array 110 is placed on the surface of a probe assembly 114. This probe assembly 114 includes a switching circuit 115. This switching circuit moves the operating transducer element group 111 along the transducer array, moves the ultrasonic beam 112 in parallel,
Scan the human body in a straight line. The operation of a prior art imaging device that advances a group of moving transducer elements along an array is described in Proceedings of the IEEE, Vol. 67, No. 4 (1979). April issue)
Albert Macovski's article ``Ultrasonic Imaging Using Arrays'' and Maxwell G.
Maginness)'s paper ``Methods and Terminology, Ultrasound Imaging Systems''
(Methods and Terminology for Diagnostics
Ultrasound Imaging Systems), and these papers can be referred to as materials for understanding the background of the present invention. As pointed out in these papers, operating a group of transducer elements in an array together and stepping them takes up less space than operating each individual transducer element sequentially. Increase resolution and improve S/N ratio. GB 1,546,445 describes an ultrasonic transducer array having a curvilinear arrangement of transducer elements which are individually operated to generate an ultrasonic beam for use in fan-shaped operations. Therefore, a lens with a positive focal length (convergent lens) is used together with the ultrasonic transducer array.
is used to focus the ultrasound beam and pass it through the space between the ribs. But this British patent no. 1546445
In the ultrasonic transducer array of No. 1, only one transducer element is active at a time, so the spatial resolution and signal-to-noise ratio are quite low. However, the performance of this curved ultrasonic transducer array cannot be improved by directly applying the technique of stepping the operating transducers of FIG. 2 to this curved array structure. Simultaneously operating a group of adjacent transducer elements on a capped, curved ultrasound transducer array necessarily causes the output beam to be strongly focused, which diverges in the far field. This is because it is inappropriate as a medical imaging device. FIG. 3 is a schematic diagram of a probe including a curved ultrasonic transducer array made by the manufacturing method of the present invention. A large number of electricity along the arc
The acoustic transducer elements 200 are arranged and the ultrasonic transducer elements are oriented to emit ultrasonic energy towards the center of the arc and to receive ultrasonic energy coming from that direction.
Electrodes 202 are attached to each of these ultrasonic transducer elements 200, and these ultrasonic transducer elements 200 are connected to a pulse generation/reception circuit (not shown) via a sequence circuit. The entire ultrasound transducer array is then housed within a housing 204 that includes a window 206 through which ultrasound waves can pass. The interior of the housing 204 is filled with an ultrasound-transmissive fluid 208, such as castor oil, that matches the ultrasound transmission characteristics of the human body. Alternatively, housing 204 may be filled with a solid material. Generally, these filler materials need to have an acoustic attenuation rate intermediate between that of water and that of human tissue, and their acoustic impedance needs to match that of human tissue. A group of mutually adjacent transducer elements (eg, 220) is activated each time an ultrasound pulse is sent out and a reflected echo is received. Then, each time a pulse is issued, a group of transducer elements, which operate by one transducer element, are shifted along the array to perform fan-shaped scanning with the ultrasonic beam. In such a curved ultrasonic transducer array, the ultrasonic beam is originally focused strongly, but in order to weaken this, a means for weakening the focusing effect is included. Combining such defocusing means with a curved ultrasonic transducer array that advances the operating transducer elements creates a prior art ultrasonic transformer that operates the transducer elements one by one. Higher spatial resolution than deuser arrays can be obtained,
The S/N ratio also becomes higher. FIG. 4 shows one preferred embodiment of means for weakening such a focusing effect. Assume that at a certain instant, a group of transducers (AK) 220 in the ultrasonic transducer array are activated by a sequence switch (not shown for clarity). The central transducer F in this group 220 is a direct transmit/receive switch 26
Connect to 0. The transmitting/receiving switch 260 is connected to a circuit 240 that outputs an electrical signal for generating ultrasonic pulses and a circuit 250 that receives an electrical signal generated by converting the received ultrasonic pulse.
A pair of transducers E and G on both sides of the central transducer F are connected to a transmit/receive switch 260 via a first delay circuit 270. The next adjacent pair of transducers D
and H are connected to the transmitting/receiving switch 260 via a second delay circuit 280 whose delay time is longer than that of the first delay circuit 270. This group 220 is operating a pair of adjacent transducers (i.e., C and I, B and J, A and K) that are successively adjacent to each other in this group.
delay circuits 290, 30 whose delay time is proportional to the distance from the center F to the transducer;
0,310 to receive switch 260. The length of the delay time is well known in the art and is selected using the techniques described, for example, in the previously named Makovsky paper. Attenuates the effect and causes the ultrasonic energy beam to become a more parallel beam. This allows the ultrasound beam to be focused at a point deep within the patient's body. FIG. 5 shows an apparatus for stepping a group of operative transducers along an ultrasonic transducer array. A pulser 400, a receive amplifier 410, and an associated transmit/receive isolator 420 are connected to a first side end of a group of bidirectional delay lines 430 in a conventional manner. The delay time of each delay line in this group of delay lines 430 can be varied and its value can be adjusted to provide a defocusing effect on the transducer elements operating in the manner described above with respect to FIG. calculate. The opposite end of each delay line in group of delay lines 430 is connected to a row of switches in analog matrix switches 440 . The switches in each column of analog matrix switches 440 are connected to one individual transducer element 200 in ultrasound transducer array 450 . At each intersection (ie, the intersection of each row and each column) within the analog matrix switch 440, there is a separate switch (which may be a MOS transistor). These switching elements are individually operated by signals emerging from the output leads of read only memory (ROM) 460. Read only memory 460 is addressed by the output of sequence circuit 470 connected at the end of its input conductor. This sequence circuit 470 can be a sequence counter, which is driven by a clock 480. Sequencing circuit 470 addresses sequential words in read-only memory 460 and defines the connection pattern between individual transducer elements in the ultrasound transducer array;
A corresponding delay line is set to step the active transducer elements with reduced focus along the ultrasound transducer array. As an example, Table 1 shows the first three words of read-only memory 460. This is 4 delay lines~
A working group of seven transducers is moved twice along the ultrasound transducer array by establishing a connection to the ultrasonic transducer array.

[Table] The bit patterns in Table 1 have been shortened for clarity, but the principle shown here applies even when the number of transducer elements in a group of operating transducers is larger. It can also be applied to small objects. FIG. 6 is another embodiment of a probe including a curved ultrasonic transducer array,
Here, a lens 500 with a negative focal length (divergent lens) is used as a means for weakening focusing. Again, as in the embodiment of FIG. 3, a group of transducers is sequentially shifted along the ultrasonic transducer array to effect sector scanning. All transducers in group 220 can also operate simultaneously. Alternatively, means for weakening the focus by the delay line together with a lens 500 having a negative focal length (FIG. 4)
You can also use Lens 500 can be made of metal or plastic and is preferably divided into two negative lens elements, with the cavity 510 between them filled with fluid. FIG. 7 shows the first step of one preferred method of manufacturing a curved ultrasound transducer array as described above. The ultrasonic transducer array is preferably constructed from a single rectangular piezoelectric ceramic (eg, type PZT-5) rod 600. The front main surface 6 of this piezoelectric ceramic rod 600
Copper electrodes 605 and 610 are bonded to 01 and the rear main surface 602 using epoxy resin mixed with silver powder. Next, a flexible alignment window 615 is cast directly onto the front electrode 605. This alignment window 615 is made of two parts of Stycast 1264.
(Stycast 1264; trade name) It is best to make it from a mixture of resin adhesive and 1 part tungsten powder. The alignment window 615 is formed by pouring the mixture directly onto the surface of the front electrode 605 and precipitating the tungsten powder. After the resin is cured, the window is cut to a thickness of 1/4 of the acoustic wavelength corresponding to the operating frequency of the array. For example, if a window is designed to operate at 3.5MHz, it will be cut to a thickness of approximately 0.09mm. A series of parallel grooves 620 are then cut from the back electrode 610 through the top side of the piezoceramic rod and into the piezoceramic rod, dividing it into a number of individual transducer elements with associated back electrodes. In a typical case, the width of the groove is approximately 0.13 mm, and this groove is inserted to 75% of the thickness of the ceramic rod. In one preferred embodiment of the transducer array, the ceramic rods are approximately 80.5 mm long and 12.5 mm wide.
and the thickness is 2.0mm. This ceramic stick
Cut 71 grooves to form 72 transducer elements. However, since the rear electrodes on the transducer elements at both ends are connected to the front electrodes, only 70 transducer elements function as transducer elements. FIGS. 8 and 9 show alternative structures for ultrasonic transducer arrays. A grooved ceramic rod 600 and associated electrodes 605, 610 and window 615 are mounted around a semi-cylindrical mandrel 650. The grooves 620 in the ceramic rod 600 are parallel to the axis of the cylinder. As shown in detail in FIG. 9, the ceramic rod 600 has a crack under each groove 620.
Transducer elements 630 with individual electrodes are arranged in a curved array. Each transducer element 630 is held in place by front electrode 605 and alignment window 615. Next, a resin adhesive 6 containing air bubbles for support is applied to the gaps between the transducer elements 630 and around the curved rear surface of the ultrasonic transducer array.
Pour 60. This air-filled resin adhesive 660 holds the transducer elements in place and also provides a low acoustic impedance backing for each individual transducer element. The resin adhesive containing air bubbles can be, for example, an epoxy resin adhesive mixed with glass beads containing minute bubbles. In one preferred embodiment of the invention, the rear electrode 61
0 is made wider than the ceramic bar and bent along the edges of the resin adhesive to provide electrical connections to the individual transducer elements.

[Brief explanation of the drawing]

FIGS. 1 and 2 are explanatory diagrams of a conventional ultrasonic transducer array in which ultrasonic transducers are arranged in a straight line and each of these transducer elements is operated sequentially, and FIG. A plan view (partially cut away) of a probe having a curved ultrasonic transducer array related to the present invention, FIG. 4 shows the focusing action used in the ultrasonic transducer array of FIG. An explanatory diagram showing the operating principle of a delay circuit that acts as a weakening device, FIG. 5 is a block diagram of a device for operating the ultrasonic transducer array of FIG. 3, and FIG. A plan view of a probe equipped with an ultrasonic transducer array, FIG. 7 is an explanatory diagram of the first step of the method for manufacturing a curved ultrasonic transducer array, and FIG. 8 shows the completed probe after being attached to a mandrel. The explanatory diagram, FIG. 9, is a detailed diagram of a part thereof. 600... Piezoelectric ceramic rod, 601... Front main surface (front surface), 602... Back main surface (rear surface),
605...Front electrode, 610...Back electrode, 61
5... Matching window, 620... Groove, 630... Transducer element, 650... Mandrel.

Claims (1)

Claims: 1. A plurality of ultrasound transducer elements 200 arranged along a curved line to generate and/or receive a scanned beam of ultrasound energy. an array comprising: an array in which each ultrasonic transducer element is oriented to direct ultrasonic energy toward the center of the curvature and receive ultrasonic energy coming from the center of the curvature; Means 240 for outputting to the element and means 250 for receiving electrical pulses from the ultrasonic transducer element.
and; a group 220 of active transducer elements 20
0 to means 240 for outputting electrical pulses and means 250 for receiving electrical pulses, the active elements comprising a preselected number of adjacent transducer elements in the array;
means 440, wherein the preselected number is greater than or equal to two and less than the total number of transducer elements in the array; sequentially changing the transducer elements in the active groups and moving the active groups along the curvature; an ultrasonic beam generating and receiving apparatus comprising progressively shifting means 460, 470 for defocusing the ultrasonic energy generated and received by the transducer elements in the active group; into a nearly parallel beam