FI62950B - UNDERSOEKNINGSMODUL TILL EN ULTRALJUDSAVBILDNINGSANORDNING - Google Patents

Description

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Patent- and Register-Laws '' Ansttktn utltfd oeh utUkrift— publkand 31.12.82 (32) (33) (31) κ «ιοΙΙμ« - »· | · γ4 prloritM 27.03.78 27.03.78 USA (US) 890377, 890378 Styrkt (71) New York Institute of Technology, Wheatley Road, Old Westhury, New York, USA (72) William E. Glenn, Fort Lauderdale, Florida, USA (7 ^) Leitzinger Oy (5U) Research Module for ultrasound imaging equipment - Undersökningsmodul till en ultraljudsavbildningsanordning

The invention relates to a research module according to the preamble of appended claim 1 for an apparatus for examining parts of the body by means of ultrasound.

In recent years, the use of ultrasound technology has become widespread in clinical diagnoses. This technique has been used for some time in obstetrics, neurology and cardiology and is becoming increasingly important in the visualization of many different parts of the body, such as breast examination for tumors.

Several fundamental factors have led to an increase in the use of ultrasound technology. Ultrasound differs from other forms of radiation in its interaction with living systems in the sense that it is mechanical in nature. Accordingly, it provides information that is different in nature from that obtained by other methods and has been found to be complementary to other diagnostic methods, such as those using X-rays. Likewise, the use of ultrasound appears to have a much lower risk of tissue damage than the use of ionizing radiation, for example X-rays.

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Most diagnostic methods using ultrasound are based on a pulse-echo method, in which ultrasonic energy pulses are continuously generated by a suitable piezoelectric transducer, for example lead zirconate-titanate ceramics. Each short pulse of ultrasound energy is focused into a narrow beam that is sent to the patient's body, where it eventually meets the interfaces between the various structures of the body. When there is a characteristic impedance difference at the interface, some of the ultrasonic energy is reflected back from the boundary point towards the transducer. After the pulse is generated, the transducer operates by "listening," which converts the reflected energy or "echoes" received from the body back into electrical signals. The time of arrival of these echoes depends on the areas of the interfaces encountered and the rate of propagation of the ultrasound. Likewise, the amplitude of the echo indicates the reflection properties of the dividing surface, and accordingly the type of characteristic structures forming the dividing surface.

There are several ways in which the information in the received echoes can be usefully presented. In one general method, an electrical signal representing the echoes observed is amplified and directed to the vertical deflection plates of the cathode ray display. The output of the time strip generator is directed to the horizontal deflection plates. The continuous repetition of the pulse / echo process in sync with the ai-bottom signals forms a continuous display called an "A-study", where time is proportional to the area, and vertical changes in direction represent the presence of dividing surfaces. The height of these vertical changes in direction represents the intensity of the echo.

Another common display format is the so-called "B-study", in which the format of echo data is more reminiscent of a conventional television display; that is, the received echo signals are used to modulate the brightness of the display at each point examined or scanned. This type of display has been found to be particularly useful in transferring ultrasonic energy across the body such that individual "area information" provides individual display lines on the display, and successive transverse positions are used to provide successive sweep lines on the display. The two-dimensional B-research technique provides a cross-sectional image in the plane of the scan, and the resulting screen can be viewed directly or recorded on a photograph or magnetic tape. , 3 62950

Although ultrasonic mirroring has achieved good results, it has several problems that need to be eliminated in order to obtain high-quality ultrasound images easily, reliably, and cost-effectively. With regard to problems that have already been partially solved, it is known, for example, that ultrasound is reflected almost completely from and-copied with gas. This has led to the use of a connection via a liquid, for example water, or to the use of a direct contact type transducer. The latter technique may cause problems in attempting to describe arterial-like structures that may be only a few millimeters below the surface of the skin, with contact mirroring causing abnormalities in the vicinity of the transducer. Fluid coupling is advantageous over direct contact in this sense, but in turn leads to various structural problems and clumsy, usually fixed structures that are difficult to use, especially when attempting to place them in exactly the right place in the patient. In some methods, the patient must be immersed in water or the body part must be suitably arranged in contact with the wall of the water tank.

Compared to these clumsy and difficult-to-handle known devices, the device disclosed in U.S. Patent 4,084,582 already offers a substantial improvement. The device disclosed in this patent publication has a drive part and a portable research module. The drive section typically includes a timing signal generator, a wake-up and receive circuitry, and a display / recorder for displaying and / or storing electronic signals representing the image. The suitably hand-held examination module has a liquid-tight housing with a examination window formed of a flexible material. The converter in the portable research module converts the energy from the excitation circuit into ultrasonic energy and reconverts the received ultrasonic echoes of the column into electrical signals which are connected to the receiver circuit. The alignment lens is connected to the transducer, and, for example, a liquid in water fills the area between the focusing lens of the portable examination module and the examination window. The reflective radar, i.e. the sweep reflector, is placed in the liquid, and the drive motor used synchronously with the timing signals drives the sweep reflector periodically. This movement of the scanning reflector provides the transmission of successive ultrasonic pulses transverse to the direction of the radiation beam necessary for the "B-study".

4 62950 With this known device, a substantial reduction in the size of the examination module is already achieved. However, it would be desirable to make this handheld part even smaller and lighter. For this purpose, the size of the ultrasonic transducer and the scanning reflector used are essential. They have a direct effect on the size of the housing and, in addition, on the energy consumption of the motor that takes care of the rotational movement of the converter or the sweep reflector. However, these components cannot of course be made smaller, since the alignment effect and the intensity of the transducer normally associated with the transducer (in particular the lens) depend on their size. The smaller the converter, the higher the focus point and the worse the accuracy. At the same time, the intensity of the ultrasound decreases.

The object of the present invention is to provide a research module for use in ultrasonic imaging devices which has the smallest and lightest possible structure and the lowest possible energy consumption required for the scanning movement, without substantially compromising the quality of the imaging.

This object is achieved by a research module according to the invention on the basis of the features set out in the appended claims.

The present invention is preferably used as a device comprising a drive part and a portable research module. The drive member typically includes electronic components and a display, and the examination module can be conveniently carried by hand and has a liquid-tight, liquid-containing housing with a window in contact with the body to be examined. The research module includes e.g. the transducer, the alignment means, the exciter / receiver connected to the transducer, and the means for providing a mechanical sweep of the beam into the examination window. Known systems typically used a flexible window that hopefully followed the shape of the body being examined to avoid liquid / air distribution surfaces that could reflect ultrasound in an undesired manner. The present invention uses a relatively narrow elongate examination window. This shape allows the use of relatively rigid window materials, as the entire surface of the window can be brought into good contact with the body.

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In a preferred embodiment of the invention, the examination reflector has an elongate reflecting surface extended in a direction corresponding to the widening direction of the ultrasonic beam hitting it. This shape of the reflector is advantageous in that it has a relatively low moment of inertia about its axis and is relatively easy to use in a liquid.

In a preferred embodiment of the invention, the window through which the examination is performed is arranged obliquely and at an angle to the normal of the ultrasound hitting it. This oblique tends to ensure that the ultrasound, which is unfavorably internally reflected from the window, does not hit the transducer. In this embodiment, an absorbent medium, for example syntactic foam, is placed on the wall of the module to absorb the ultrasound internally reflected from the sloping window.

In the following, the invention will be described in more detail with reference to the accompanying drawings, in which Figure 1 shows the use of a research device according to the invention.

Figure 2 is a side perspective view of a research module according to the invention.

Fig. 3 is a cross-sectional view of the study module of Fig. 2 taken along the section defined by arrows 3-3, and further shows diagrams of parts of the circuitry in the module and associated drive.

Figure 4 shows the scanning of the beam leaving the transducer and the reflector of the research module according to Figure 2.

Fig. 5 is a simplified diagram showing how the shape of the illustrated embodiment allows the use of a shorter reflective probe.

Figure 1 shows a research device using the improvements according to the invention. The actuator 10 is provided with a display 11, which may typically be a television type cathode ray tube imaging surface with a suitable control panel. The drive may also include a VCR or a suitable photographic device. The actuator also typically includes power devices and components from the timing and process circuits of the system described below. A portable examination module or probe 50 (shown in Figure 2) is connected to the drive by a cable 48. At one end of the examination module is a window 52 through which an examination ultrasound beam is transmitted and a reflected beam is received. When the device is operating, the examination module 50 is manually manipulated to position the window 52 at the part of the body to be mirrored. For example, in Figure 1, the examination module is set so as to obtain a cross section in parallel. The description of other parts of the chest or other parts of the body can be easily performed by moving the probe to the desired position and direction, whereby the relative orientation of the examination window determines the angle of the taken cross-section.

Figure 3 shows a cross-section of a part of the research module or probe 50 as well as a block diagram of the parts of the circuits in it and in the drive 10 used in connection therewith. At the front end of the liquid-tight housing 51, which is possibly made of rigid plastic, there is an examination window 52. The housing 51 is filled with a suitable liquid 57, for example water. In the present embodiment, the examination window 52 is relatively flat and formed of any suitable material, for example, methyl methacrylate or nylon. The reflective probe 70 is flat in the present embodiment, but may be curved to provide focus if desired, and is further positioned at a suitable location on the rear of the housing 51, substantially facing the window 52. The probe 70 is mounted on a shaft 71 which pierces a suitable seal and is connected to an electric motor 72 mounted in a recess in the housing 51 and providing the desired oscillating motion of the probe, as indicated by the curved double-ended arrow 73.

The ultrasonic transducer 80, the shape of which is explained in more detail below, is housed in the compartment 59 of the housing 51, the transducer mounted in front of the reflective probe 70 in the module 50 with the transducer ultrasound transmitting surface facing substantially rearwardly in the module 50 towards the reflective probe 70. 70 reflects the ultrasound beam it emits back past converter 80 before passing through window 52. In particular, the transducer 80 is positioned so that the ultrasound emitted therefrom and reflected toward the window 52 (or, conversely, the beam reflected from the body 5 back to the transducer 80 through the window 52) has an angle of less than about 45 ° in the reflecting probe.

This angle of the central beam of the ultrasonic beam 7 is preferably shown in Fig. 3 by an angle α, and has an angle of about 30 ° in the reflector 70. The probe 70 preferably has a reflective surface formed of a material that follows a relatively small critical angle so that a beam impinging almost directly on the surface of the reflector does not pass through the reflector. The critical angle of the sapphire surface of the reflector 70 placed in the water 57 is about 14 ° (defined by the mutual marks of refraction between the ultrasonic sapphire and water), so the relative positions and orientations of the transducer, reflector and window in the study module 50 are selected to ensure that the reflector 70 the impacting radius is at an angle exceeding the critical angle. It can be seen that this arrangement makes particularly good use of the volume of liquid in the module 50, as the beam 7 effectively "folds back" past the transducer and travels a relatively long distance through a relatively small amount of water. The beryllium surface also provides a small critical angle, but due to its toxicity, it is difficult to work with. A further alternative is to use a reflective probe with an intervening gas layer, as disclosed in U.S. Patent 4,084,582. As shown, the liquid / gas distribution surface on the surface of the reflector ensures full reflection regardless of the angle of incidence of the beam.

The pulse transmitter / receiver circuit 130 alternately generates excitation pulses and receives echo pulses from the converter 80. As used herein, the term pulse transmitter / receiver includes all combined or separate circuits for generating excitation signals for the transducer and receiving echo signals therefrom. If dynamic focusing is used, the converter 80 can be divided into parts, and the pulse output and / or receiver circuit 130 can be connected to the segments of the converter 80 via a control delay circuit 100 shown in broken lines. The pulse output and / or receiver circuit 130 and the control delay circuit 100 (if present) are typically, though not necessarily, located in the research module 50, for example in compartment 59. The receiver portion of circuit 130 is connected via amplifier 140 to display 11 and recorder 160, which may be any suitable storage device. , a memory and / or photographic device, such as a VCR. If desired, a gain control circuit with interactive gain compensation ("IGC") may be used, as shown in block 141. The interactive gain compensation technique is detailed in U.S. Patent 4,043,181. This circuit compensates or compensates for the signals that have occurred later during the passage through the body tissue, as well as the losses caused by previous reflections. Accordingly, which TGC is used, the amplifier 140 can be used as a gain regulator under the control of the IGC signal from the circuit 141. The timing circuit 170 generates timing signals that synchronize the operation of the system, the timing signals being coupled to the pulse transmitter / receiver 130 and likewise to the scanning circuit 180, which generates the signals controlling the oscillations of the probe 70 and the vertical and horizontal synchronization signals for the display 11 and the recorder 160. If dynamic focusing is used, as disclosed in U.S. Patent Application 665,898, which application is transferred to the assignee of the present application, the timing signals may also be coupled to phase control circuit 120, which generates signals for controlling changes in the delays of control delay circuit 100. The examination module 50 also preferably uses a lens 90, which has a relatively flat surface typically attached to the transducer, and further has a curved concave surface that provides an axially symmetrical focus. The lens may be formed of a plastic material, the material being selected in accordance with the principle set forth in U.S. Patent 3,958,559, which is also assigned to the assignee of the present application. According to this patent, by selecting a lens material according to well-defined parameters, "apodization" is achieved; i.e., adverse side shifts caused by factors such as limited converter size are minimized. According to a further referenced patent, the outline of the lens may be generally elliptical to provide advantageous properties. However, if desired, alternative focusing means can be used, for example electronic focusing using a segmented transducer, or it is also possible to arrange the curvature on the transducer or on the surface of the reflector.

The system operates as follows: When a command is received from the timer circuits, the bag slider in circuit 130 generates excitation pulses from transducer 80, whereby the semnets of transducer 80 are aroused or triggered via adjustable delay circuit 100 under the control of a pulse control circuit using dynamic focusing. (As is known in the art, the depth of the 62950 focal point or focus point can be electronically controlled in a dynamically focused system by applying predetermined delays or phase changes to the various segments of the converter 80.

In this case, the ultrasonic pulse is typically triggered with an adjustable delay circuit set so that the transmitted beam 1a is focused to a point between the center of the field and the point deepest in the body from which the image is sought) by pulsing the transducer Now the timer circuit causes the pulse transmitter / receiver 130 to switch to "reception" or "listening". (When using dynamic focus, section 120 of the phase control circuit is activated). Now that the ultrasonic echoes are received from the body through the window 52 as reflected from the probe 70 to the transducer 80, the transducer converts the received ultrasonic energy into electrical signals. (Again, in dynamic focusing, the converter segments convert the received ultrasonic energy into electrical signals that are combined in a suitable phase ratio to refine certain radiation origins in the range of depths being examined.) synchronize the horizontal pace of the screen so that the active portion of the screen sweep line corresponds to the time of arrival of echoes from a particular area of the body 5, typically from a patient's skin to a predetermined depth in the body. Another dimension of the desired cross-sectional image is provided by a slower mechanical sweep of the reflective probe 70 synchronized by the sweep circuit 180 with the vertical sweep frequency of the display and recorder. The received signals are coupled via an amplifier 140 to a display 11, where the received signals modulate the brightness of the scan or line grid to provide the desired cross-sectional image, with each line of the display representing a body depth echo profile depending on the specific angular direction of the probe 70. The received signals are also stored in the VCR 160.

Fig. 4 shows a sweep of the beam 7, shown as the movement of the sweep point 8 along the dashed line 8A. According to one feature of the invention, the shape of the transducer 80 is preferably generally elliptical and elongate in the sweep direction. The length-to-width ratio of the transducer is preferably at least 2: 1. The dashed lines of the converter show its segmentation in the case where electronic 10 62950 (e.g. dynamic) focusing is used. The thickness of the focusing lens 90 (Figure 3) is axially symmetrical, generally either spherical or rotational ellipsoid. As discussed above, the circumference of the lens is preferably elliptical following the shape of the transducer. It will be appreciated that alternative focusing means may be used, such as electronic focusing using a segmented transducer or providing a suitable curvature to the surface of the transducer or reflector. In this case, the focus should be axially symmetrical over the entire range of the transducer. After focusing, the resultant point 8 is elongated in a direction perpendicular to the scanning direction, because the diffraction limit in the longitudinal direction of the transducer is smaller than the diffraction limit in a direction perpendicular thereto. The thickness of the "part" examined is therefore substantially greater (preferably at least twice as large) as the resolution element in the scanning direction. The reflector 70 may also be extended to be substantially elliptical, as shown in Figure 4. The torque required to operate a reflector depends to a large extent on its size and mass. The substantially elliptical shape of the mirror is advantageous in that its use requires less force compared to larger and more symmetrical mirrors. Likewise, the "rear folding" shape allows the use of a mirror that is smaller in size compared to, for example, a system in which the beam is reflected at an approximately right angle. This results in even less propulsion being required. The simplified diagram of Figure 5 illustrates this principle. Geometrically, it can be seen that the reflector 70 '(which deflects the incident beam at right angles to the focal point 8') is necessarily longer by a factor v ^ than the reflector 70, which reflects the beam directly back towards the focal point 8.

According to a further feature of the invention, the window 52 is arranged at an angle of, for example, about 10 ° with respect to the direction perpendicular to the incoming ultrasound (see Fig. 3). This reference seeks to ensure that the undesired ultrasound reflected from the window (which window can advantageously be formed of a relatively rigid material) does not hit the transducer. For example, the absorbent medium 55 formed of syntactic foam is disposed in the path of the internally reflected ultrasound shown by dashed line 53 in Figure 3. In the illustrated embodiment, the window is sloping toward the top of the module 50 and the absorbent 55 is located on the upper inner surface of the housing 51.

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Figures 6 and 7 show an examination module 50 'according to a further embodiment of the invention, which can be used with the console 10 in the same way as the examination module 50 according to Figure 1. The examination module 50' has a window 52 'at one end through which an examination ultrasound beam is transmitted and a reflected beam is received. . Figure 7 is a cross-sectional view of a portion of the study module or probe 50 ', as well as diagrams of portions of the circuits therein and in the console 10 (Figure 1) used in the same context. The liquid-tight housing 51 is again formed of rigid plastic and has at its front an examination window 52 '. The housing 51 'is filled with liquid 57'. The ultrasonic transducer 80 'is pivotally mounted on the shaft 71'. The shaft 71 'passes through a suitable seal in the housing 51, in which housing it is connected to a motor 72', which is typically a small electric motor and mounted in a liquid-tight manner outside the housing 51 'and used to cause the transducer 80' to oscillate. The motor 12 'can be attached to a shoulder formed in the housing 51', as shown in the figure, and provided with a cover to avoid irregularity in the appearance of the examination module 50 '. According to Fig. 8, the transducer 80 'is elongated in the scanning direction, the shape of the transducer being substantially elliptical as previously described, the length-to-width ratio being preferably at least 2: 1. In the present embodiment, a focusing lens 85 'of the type previously described is attached to the front of the transducer 80'.

In the present embodiment, the rear layer 87 'is attached to the inverter 80' on the rear surface and the rear floor is mounted on a shaft 71 'so that the back layer, the transducer and the lens can oscillate in the direction of arrow 89 of Figures 8 and 9' of the figure. Fig. 8 shows a beam sweep shown by the movement of the sweep point 8 'along the dashed line 8A'. Focusing is performed on a lens 85 '(Fig. 9) attached to the transducer 80', the circumference of which follows the shape of the transducer, and after this focusing the resultant point 8 'is elongated perpendicular to the scanning direction because the diffraction limit in the longitudinal direction of the transducer is less than in a rectangular direction. As in the previous embodiment, the thickness of the "part" to be examined is therefore substantially greater (preferably at least twice as large) as the resolution element in the scanning direction.

The pulse transmitter / receiver circuit 130 'alternately generates excitation pulses at the converter 80' and receives echo signals therefrom. Using 12,62950 dynamic focus, the converter 80 can be segmented, as shown by lines 80A 'in Figure 8, and the pulse transmitter / receiver circuit 130' can be coupled to the segments of the converter 80 'by an adjustable delay circuit 100', shown by a broken line. The pulse transmitter / receiver circuit 130 and the adjustable delay circuit 100 (if present) are typically, though not necessarily, located in the examination module 50 ', for example in the area defined by the cover 135', which cover can be attached to the liquid-tight housing 51 'by conventional means. The receiver portion of the circuit 130 is connected via an amplifier 140 'to the display 11' and the recorder 160 '. Gain control circuits 140 'and 141' may be included as in the embodiment of Figure 3. The timing circuit 195 'generates timing signals that synchronize the operation of the system, the timing signals being coupled to the pulse output and / or receiver 130' and also to the sweeping circuit 196 ', which generates signals controlling the oscillation motion of the motor 72' and the vertical and horizontal synchronous signals 11. for the recorder 160 '. Using dynamic focus as disclosed in U.S. Patent Application 665,898, which is assigned to the assignee of the present application, the timing signals may also be coupled to a phase control circuit 120 'which generates those signals that control the variation of the delays in the adjustable delay circuit 100'.

The operation of the system of Figure 7 is similar to that of the system of Figure 3 except that in this case the transducer itself vibrates and not the reflective radar. The torque required to operate the transducer (with backplane and lens in this embodiment) depends to a large extent on the size and mass of the transducer, and the present shape has the advantage over conventional transducer shapes that significantly less force is required to operate the transducer. This allows the shape of Figures 6 and 7 in which the transducer oscillates directly from the fluid.

As in the previous embodiment, the window 52 'is preferably arranged at an oblique angle which tends to cause the ultrasound reflected from the window in an undesired manner to bypass the transducer and be absorbed by the absorbent 55'.

The invention has been described herein with reference to certain embodiments, but many modifications may be made by those skilled in the art without departing from the scope of the invention. For example, it is possible to place some console circuits in the research module or vice versa, in which case the basic condition is to keep the module portable and at the same time minimize the noise sensitivity of the sub-signals passing through the cables between the research module and the console.

Claims (12)

62950 14 A research module for ultrasound imaging of body parts by transmitting ultrasound energy to the body and determining the characteristics of the ultrasound energy reflected from the body, the apparatus comprising generating timer signals for a timer member (170, 195 '); an exciter / receiver member (130) operating alternately in response to the timer signals; a display / recording element (11, 160) synchronized with the timer signals for displaying and / or storing image signals from the wake-up / receiver element; wherein the examination module has a liquid-tight housing (51) having a window (52) on the front side, the housing having a reflective probe (70) and a fixed transducer (80) for converting energy from the exciter / receiver member (130) into an ultrasonic beam and reflected ultrasound for converting to electrical signals, the housing (51) being filled with liquid and provided with actuators (72) synchronized with the timer signals for periodically moving the probe members (70), characterized in that the reflective probe (70) is mounted at a distance from the window (52) (80) is mounted in front of the reflective probe (70) in the housing (51) and the ultrasound-transmitting upper surface of the transducer (80) is opposite the reflective probe (70) in such a way that the ultrasonic beam emitted by the transducer (80) and reflected from the transducer (70) ) before piercing the window, and that the reflecting radar (7 0) is mounted in this way on the wheel that the ultrasonic beam sweeps the window (52) in such a way that the angle (α) formed between the center beam of the beam radiating from the reflecting probe and the plane at which the center beam of the beam reflected from the probe moves is substantially constant and non-zero. Research module according to claim 1, characterized in that said substantially constant angle (α) is less than 45 °. A research module according to claim 2, characterized in that said angle is about 30 °. Examination module according to one of Claims 1 to 3, characterized in that the reflective upper surface of the probe (70) has a layer of sapphire material. Survey module according to one of Claims 1 to 3, characterized in that the reflective surface of the probe (70) has a beryllium layer. Research module according to one of Claims 1 to 5, characterized in that it comprises an alignment lens (90) connected to the transducer (80). Research module according to one of Claims 1 to 6, characterized in that the transducer (80) is extended in the scanning direction of the beam. Examination module according to one of Claims 1 to 7, characterized in that the reflecting probe (70) has an elongate reflecting surface which is extended in the direction of the widening of the ultrasonic beam impinging on it. An examination module according to claim 8, characterized in that the reflective probe (70) is mounted in a liquid on an axis (71) perpendicular to the longitudinal direction of the probe. Research module according to one of Claims 1 to 9, characterized in that the window (52) is extended in the scanning direction of the beam. Examination module according to one of Claims 1 to 10, characterized in that the window (52) is inclined at an angle to the normal of the ultrasonic beam facing the window. Examination module according to Claim 11, characterized in that the examination module contains an ultrasonic absorbing substance which is arranged in the passage of the ultrasound reflected from the window (52) inclined in the housing (51). 16 62950