ULTRASONIC PROBE

Abstract: An ultrasonic transducer element (l30) is supported by a member (l20). The transducer element and the supporting member are disposed within a casing (l00) filled with ultrasonic wave propagation medium (l50). At least part of the casing forms an ultrasonic wave transmission window. In a first case, the supporting member (l20) is rotatable about a first axis (A) and about a second axis (B), and the position of the supporting member is detected (20). In a second case, the casing (30l) has a first portion (304) accommodating the transducer element (306) and the supporting member (307) and a second portion (303) extending in rear of the first portion and being narrower than the first portion, and the transducer element is allowed to emit and receive ultrasonic wave to and from a region extending in front of the casing with respect to a direction of insertion of the casing into a body to be examined. In a third case, a sensor (322) detects at least one condition related to operation of a mechanism driving the supporting member.

Description: BACKGROUND OF THE INVENTION Field of the Invention This invention relates to an ultrasonic probe usable in ultrasonic systems such as medical ultrasonic diagnostic systems. Description of the Prior Art An ultrasonic probe is disclosed in document JP-A-53/83 370. This ultrasonic probe comprises an ultrasonic transducer element which is supported by a supporting member. The supporting member is rotatable about a first and a second axis which are defined by a shaft, respectively. The shafts are arranged perpendicularly to each other. Furthermore, document EP-A-0 039 045 discloses an ultrasonic diagnostic apparatus with an ultrasonic transducer. The ultrasonic transducer is rotatably supported in a bendable tube so that the tip of the insert section of the bendable tube may be brought closely into contact with the body wall. The conventional ultrasonic probes have a large casing or limited angular ranges. SUMMARY OF THE INVENTION It is a first object of this invention to provide a small ultrasonic probe. It is a second object of this invention to provide an ultrasonic probe which generates an acceptably low level of vibration. It is a third object of this invention to provide an easily handleable ultrasonic probe. It is a fourth object of this invention to provide an ultrasonic probe which can produce sectional images in a region where sectional images are generally unavailable heretofore. According to the invention, these objects are accomplished by an ultrasonic probe comprising: a) an ultrasonic transducer element; b) a member supporting the transducer element; c) means for rotating the supporting member about a first axis defined by a first shaft and also about a second axis defined by a second shaft said first shaft extending perpendicularly to said second shaft; d) a casing accomodating the transducer element and the supporting member and filled with ultrasonic wave propagation medium, wherein at least part of the casing forms an ultrasonic wave transmisssion window; e) means for detecting positions of the supporting member; f) a chassis disposed in said casing which chassis can rotate about said second shaft, said transducer element rotating together with said chassis, so that scanning along a circular plane is performed; a rotating force being transmitted through said second shaft to said transducer element to rotate said transducer element about said first shaft, so that a sector plane is scanned and, by combining the two ways of scanning, a hemispherical image of a body can be obtained. Thus, the ultrasonic probe according to the present invention can produce sectional images of a body over a wide range. Furthermore the ultrasonic probe can produce a hemispherical image of a body when a sector scan and a circular scan are combined. The power drive train of this ultrasonic probe may be basically composed of gears and pulleys so that the level of generated vibrations is acceptably low. The advantages of the invention will become apparent and obvious to those skilled in the pertinent art upon referring to the following description provided in connection with the accompanying drawings, of which Fig. 1 is a diagram of a known ultrasonic probe. Fig. 2 is a sectional view of an organ and another known ultrasonic probe. Fig. 3 is a sectional view of an ultrasonic probe according to a first embodiment of this invention. Fig. 4 is a diagram showing rotations of the support and the transducer element, and scanning planes in the ultrasonic probe of Fig. 3. Fig. 5 is a sectional view of an ultrasonic probe according to a second embodiment of this invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to the description of embodiments of this invention, known ultrasonic probes will be desribed hereinafter for a better understanding of this invention. Fig. 1 shows a known ultrasonic probe of the mechanically scanning type disclosed in Japanese published unexamined patent application 53-83370. In the known ultrasonic probe of Fig. 1, an ultrasonic transducer element or head 1 is rotatably supported on a frame 3 via a shaft 2. The transducer element 1 is connected via a link 4A to a power source 5A, such as an electric motor, a pneumatic actuator, or a hydraulic actuator. The power source 5A can rotate the transducer element 1 about the shaft 2 in a limited angular range. A synchronizing device 7 controls operation of the power source 5A. The rotation of the transducer element 1 by the power source 5A allows a sector scan of a beam of ultrasonic wave pulses emitted from the transducer element 1. This scan produces a sectoral section image of a body. A direction shaft 6 carrying the frame 3 is connected via a link 4B to a power source 5B, such as an electric motor, a pneumatic actuator, or a hydraulic actuator. The power source 5B can rotate the frame 3 about the direction shaft 6. Accordingly, at varying directions or angular positions of the frame 3, sectoral section images of the body are available. The synchronizing device 7 controls operation of the power source 5B. In the known ultrasonic probe of Fig. 1, the transducer element drive mechanism composed of the link 4A and the power source 5A considerably limits the angle of the sector scan of the beam of ultrasonic wave pulses. The links 4A and 4B cause the probe to be large. Since the transducer element 1 and the frame 3 are subjected to reciprocating rotational movements in limited angular ranges, great mechanical vibrations tend to be generated. Japanese published unexamined patent application 59-131339 discloses an ultrasonic probe designed to be used in coeloms of a body to produce sectional images of internal organs. Fig. 2 shows such a known ultrasonic probe. In the known ultrasonic probe of Fig. 2, a pulse motor 11 is connected to a damper 14 via a micro gear head 12 and a shaft 13. The damper 14 carries an ultrasonic transducer element or head 15. The shaft 13 is supported by a plate 16. The devices 11-16 are accommodated in a casing 17. As shown in Fig. 2, the ultrasonic probe is inserted into an organ 18 of a body. The pulse motor 11 serves to rotate the damper 14 and the transducer element 15 about the shaft 13. The micro gear head 12 reduces the rotational speed of the transducer element 15 in comparison with the rotational speed of the pulse motor 11. The rotation of the transducer element 15 by the pulse motor 11 allows a sector scan of a beam of ultrasonic wave pulses emitted from the transducer element 15. This scan of the beam of ultrasonic wave pulses produces a sectoral section image of the organ 18. In the known ultrasonic probe of Fig. 2, since the transducer element 15 is rotatable only about the shaft 13, a section of the organ 18 which can be imaged extends along a plane (denoted by the broken line in Fig. 2) perpendicular to the shaft 13. Accordingly, it is generally difficult to take a sectional image of a portion of the organ 18 extending at and around an assumed extension of the shaft 13. Specifically, it is difficult to take a sectional image of a portion of the organ 18 extending in front of the casing 17 with respect to a direction of the insertion of the probe into the organ 18. In addition, since the casing 17 has a large outside diameter, a patient tends to suffer pain during the insertion and use of the probe. In the known ultrasonic probes of Figs. 1 and 2, it is generally difficult to limit variations in loads on the power sources 5A and 5B, and the pulse motor 11 within acceptably small ranges. Since the speeds of the transducer elements 1 and 15 fluctuate with variations in loads on the power devices 5A, 5B, and 11, available sectional images are degraded by these load variations. Such power device load variations are generally caused by dimensional errors of parts of the drive arrangements between the power devices and the transducer elements, and caused by temperature variations. Accordingly, in the known ultrasonic probes of Figs. 1 and 2, a yield tends to be low. Fig. 3 shows an ultrasonic probe according to a first embodiment of this invention. In the ultrasonic probe of Fig. 3, a motor 19 and an encoder 20 are disposed within a cylindrical casing 40. A cable 30 containing electric leads extends into the casing 40 and is electrically connected to the motor 19 and the encoder 20. The cable 30 is also electrically connected to a main portion of a medical ultrasonic diagnostic system (not shown). Various signals are transmitted between the main portion of the diagnostic system and the motor 19, and between the main portion of the diagnostic system and the encoder 20 via the cable 30. A chassis 80 is disposed within a housing or container 100 fixed to the casing 40. An ultrasonic transducer element or head 130 is attached to an outer surface of a support 120 which is rotatably connected to the chassis 80 via a shaft 110. The transducer element 130 is preferably provided with an acoustic matching layer and an acoustic lens in a known manner. A signal transmission device 50 preferably composed of a slip ring is mounted on the chassis 80. A rotary transformer (not shown) is disposed within the support 120. The transducer element 130 is electrically connected to the cable 30 via the signal transmission device 50, the rotary transformer, and leads (not shown). It should be noted that the rotary transformer may be replaced by a slip ring. The container 100 is filled with a liquid ultrasonic wave propagation medium. An O-ring 60 provided between the chassis 80 and a shaft 190 prevents leakage of the ultrasonic wave propagation liquid. An O-ring 70 provided between the chassis 80 and the container 100 also prevents leakage of the ultrasonic wave propagation liquid. The container 100 is preferably made of a material permeable to ultrasonic waves so that the container 100 forms an ultrasonic wave transmission window. It should be noted that only a portion of the container 100 may be designed to form an ultrasonic wave transmission window. The motor 19 has a rotatable output shaft coaxial with the shaft 190. A clutch 200 provided between the motor shaft and the shaft 190 selectively connects and disconnects the shaft 190 to and from the motor shaft. The shaft 190 extends along a central axis of the chassis 80. A bevel gear 90 is fixedly mounted on a shaft 91 rotatably supported by the chassis 80. The shaft 91 extends perpendicular to the shaft 190. The bevel gear 90 meshes with a bevel gear 180 fixedly mounted on the shaft 190. A pulley 170 fixedly mounted on the shaft 91 is coupled via an endless belt 160 to a pulley 140 fixedly mounted on the shaft 110. The shaft 110 extends parallel to the shaft 91 and perpendicular to the shaft 190. In cases where the clutch 200 connects the shaft 190 to the motor shaft, when the motor 19 is activated, a rotational force is transmitted from the motor 19 to the support 120 via the motor shaft, the clutch 200, the shaft 190, the bevel gears 90 and 180, the shaft 91, the pulley 170, the belt 160, the pulley 140, and the shaft 110 so that the support 120 and the tranducer element 130 rotate about the shaft 110. This rotation of the support 120 and the transducer element 130 is denoted by the arrow A in Fig. 4. A gear 210 is fixedly carried on a slider 230 connected to the motor shaft. The connection between the slider 230 and the motor shaft preferably includes a key coupling which allows the slider 230 to rotate together with the motor shaft and allows the slider 230 to move axially relative to the motor shaft. Since the gear 210 is fixed to the slider 230, the gear 210 rotates together with the motor shaft but is axially movable relative to the motor shaft. A gear 220 is secured to the chassis 80. As the gear 210 is moved axially by the slider 230, the gear 210 comes into and out of mesh with the gear 220. The chassis 80 is rotatably supported on the container 100 via bearings. The chassis 80 can rotate about the motor shaft and the shaft 190. Since the transducer element 130 is connected to the chassis 80 via the support 120 and the shaft 110, the transducer element 130 rotates together with the chassis 80. In cases where the clutch 200 disconnects the motor shaft from the shaft 190, when the gear 210 is moved into mesh with the gear 220 and the motor 19 is activated, a rotational force is transmitted from the motor 19 to the chassis 80 so that the chassis 80 and the transducer element 130 rotate about the motor shaft and the shaft 190. This rotation of the transducer element 130 is denoted by the arrow B in Fig. 4. The clutch 200 is preferably of the electromagnetic type. In this case, the clutch 200 is electrically connected to the cable 30 via electric leads so that the clutch 200 is controllable via an electric signal output from the main portion of the diagnostic system. It should be noted that the clutch 200 may be controllable via a mechanical device which can be handled outside the casing 40. The slider 230 is preferably driven by an electric actuator or a solenoid disposed within the casing 40. In this case, the actuator or the solenoid is electrically connected to the cable 30 via electric leads so that the slider 230 is controllable via an electric signal output from the main portion of the diagnostic system. It should be noted that the slider 230 may be controllable via a mechanical device which can be handled outside the casing 40. The encoder 20 is associated with the motor shaft. The encoder 20 generates an electric signal or signals representing the angular position of the motor shaft and the rotational speed of the motor shaft. These signals are transmitted to the main portion of the diagnostic system via the cable 30. The encoder 20 is preferably of the optical type or the electromagnetic type generating electric pulses in accordance with the rotation of the motor shaft. Since the position of the transducer element 130 depends on the angular position of the motor shaft, the position of the transducer element 130 is detected via the signal representing the angular position of the motor shaft. The ultrasonic probe of Fig. 3 operates as follows. The ultrasonic probe is generally inserted into a coelom of a body to be examined. First, the operation of the ultrasonic probe will be described with respect to cases where the slider 230 is moved to a position at which the gear 210 separates from the gear 220, and where the clutch 200 is controlled so that the shaft 190 is coupled to the motor shaft. Under these conditions, as the motor 19 is activated, the support 120 and the transducer element 130 rotate about the shaft 110 and in the direction denoted by the arrow A of Fig. 4. When the position of the transducer element 130 which is detected via the signal from the encoder 20 reaches a desired position or range, the main portion of the diagnostic system outputs an activation signal to the transducer element 130 via the cable 30, the signal transmission device 50, and the rotary transformer (not shown) within the support 120 so that the transducer element 130 is energized. Accordingly, the transducer element 130 emits a beam of ultrasonic wave pulses, which travels to the body via the ultrasonic wave propagation liquid 150 and the walls of the container 100. The body generally has uneven acoustic impedances which cause the ultrasonic wave pulses to be reflected. The reflected ultrasonic wave pulses return to the transducer element 130. The transducer element 130 converts the reflected and returned ultrasonic wave pulses into a corresponding electric signal, which is transmitted to the main portion of the diagnostic system via the rotary transformer within the support 120, the signal transmission device 50, and the cable 30. The main portion of the diagnostic system processes this electric signal and thereby derives a display data signal corresponding to one scanning line in a known way. The data signal is indicated by a display such as a cathode-ray tube. The previously-mentioned operation to derive a display data signal corresponding to one scanning line is periodically reiterated while the transducer element 130 is rotated through a desired angular range by the motor 19. In this way, the beam of ultrasonic wave pulses emitted from the transducer element 130 is scanned along a sector plane 300 as shown in Fig. 4, so that a corresponding sector sectional image of the body is obtained on the display. During this sector scanning process, the main portion of the diagnostic system monitors the position of the transducer element 130 via the signal from the encoder 20 and controls the position of the transducer element 130 in accordance with the monitored information via the signal to the motor 19 in conventional closed loop control. Furthermore, the main portion of the diagnostic system controls the speed of the motor 19 in accordance with the speed signal from the encoder 20 to regulate the rotational speed of the support 120 and the transducer element 130 at a constant value. The angle of the sector scan of the ultrasonic wave beam is, for example, 100°. The sector scan angle may be 360° or other values. The support 120 and the transducer element 130 may be rotated in reciprocatory motion by a suitable actuator to produce a sector scan of the ultrasonic wave beam. Second, the operation of the ultrasonic probe will be described with respect to cases where the clutch 200 is controlled so that the shaft 190 is disconnected from the motor shaft, and where the slider 230 is moved to a position at which the gear 210 meshes with the gear 220. Under these conditions, as the motor 19 is activated, the support 120 and the transducer element 130 rotate together with the chassis 80 about the motor shaft and the shaft 190 and in the direction denoted by the arrow B of Fig. 4. In these cases, the transducer element 130 is generally prelocated so as to face in the direction perpendicular to the motor shaft and the shaft 190. When the position of the transducer element 130 which is detected via the signal from the encoder 20 reaches a desired position or range, the main portion of the diagnostic system outputs an activation signal to the transducer element 130 via the cable 30, the signal transmission device 50, and the rotary transformer (not shown) within the support 120 so that the transducer element 130 is energized. Accordingly, the transducer element 130 emits a beam of ultrasonic wave pulses, which travels to the body via the ultrasonic wave propagation liquid 150 and the walls of the container 100. The body generally has uneven acoustic impedances which cause the ultrasonic wave pulses to be reflected. The reflected ultrasonic wave pulses return to the transducer element 130. The transducer element 130 converts the reflected and returned ultrasonic wave pulses into a corresponding electric signal, which is transmitted to the main portion of the diagnostic system via the rotary transformer within the support 120, the signal transmission device 50, and the cable 30. The main portion of the diagnostic system processes this electric signal and thereby derives a display data signal corresponding to one scanning line in a known way. The data signal is indicated by the display. In general, the previously-mentioned operation to derive a display data signal corresponding to one scanning line is periodically reiterated while the transducer element 130 is rotated through an angle of 360° by the motor 19. In this way, the beam of ultrasonic wave pulses emitted from the transducer element 130 is scanned along a circular plane 400 as shown in Fig. 4, so that a corresponding circular sectional image of the body is obtained on the display. During this circular scanning process, the main portion of the diagnostic system monitors the position of the transducer element 130 via the signal from the encoder 20 and controls the position of the transducer element 130 in accordance with the monitored information via the signal to the motor 19 in conventional closed loop control. Furthermore, the main portion of the diagnostic system controls the speed of the motor 19 in accordance with the speed signal from the encoder 20 to regulate the rotational speed of the transducer element 130 at a constant value. It should be noted that the angle of the circular scan of the ultrasonic wave beam may be smaller than 360°. As understood from the previous description, the ultrasonic probe of Figs. 3 and 4 can produce sectional imgages of a body over a wide range. Furthermore, the ultrasonic probe of Figs. 3 and 4 can produce a hemispherical imgage of a body when a sector scan and a circular scan are combined. In the ultrasonic probe of Figs. 3 and 4, the power drive train is basically composed of the gears and the pulleys so that the level of generated vibrations is acceptably low. Fig. 5 shows an ultrasonic probe according to a second embodiment of this invention. The second embodiment is similar to the embodiment of Figs. 3 and 4 except for design changes described hereinafter. In the ultrasonic probe of Fig. 5, the clutch 200 and the slider 230 (see Fig. 3) are omitted, and the shaft 190 is directly coupled to the output shaft of the motor 19. A second motor 19A and a second encoder 20A are disposed within the casing 40. A gear 210 fixedly mounted on an output shaft of the motor 19A meshes with a gear 220 fixed to the chassis 80. The second motor 19A is electrically connected to the cable 30 so that the second motor 19A can be controlled via an electric signal output from the main portion of the diagnostic system. The second encoder 20A is associated with the output shaft of the second motor 19A. The second encoder 20A generates an electric signal or signals representing the angular position of the output shaft of the second motor 19A and the rotational speed of the output shaft of the second motor 19A. The second encoder 20A is electrically connected to the cable 30 so that the electric signals are transmitted from the second encoder 20A to the main portion of the diagnostic system via the cable 30. As the motor 19 is activated, the shaft 190 rotates so that the support 120 and the transducer element 130 rotate about the shaft 110. This rotation of the transducer element 130 allows a sector scan of the ultrasonic wave beam. As the second motor 19A is activated, the chassis 80 rotates so that the support 120 and the transducer element 130 rotate together with the chassis 80. This rotation of the transducer element 130 allows a circular scan of the ultrasonic wave beam. Since the position of the transducer element 130 depends on the angular position of the output shaft of the motor 19 and on the angular position of the output shaft of the second motor 19A the signals output from the encoders 20 and 20A represent the position of the transducer element 130. The main portion of the diagnostic system controls the motors 19 and 19A in accordance with the signals from the encoders 20 and 20A. In the ultrasonic probe of Fig. 5, the sector scanning mechanism and the circular scanning mechanism include separate motors and encoders respectively, so that a quick change between the sector scan and the circular scan is allowed. It should be noted that in the motor power drive trains of the embodiments of Figs. 3-5, the gears and the pulleys may be replaced by other suitable elements.

Claims: An ultrasonic probe comprising a) an ultrasonic transducer element (130); b) a supporting member (120) for supporting said transducer element (130); c) means for rotating said supporting member (120) about a first axis defined by a first shaft (110) and also about a second axis defined by a second shaft (190), said first shaft (110) extending perpendicularly to said second shaft (190); d) a casing (100) accommodating the transducer element (130) and the supporting member (120) and filled with ultrasonic wave propagation medium, wherein at least part of the casing forms an ultrasonic wave transmisssion window; e) means (20) for detecting positions of the supporting member (120); f) a chassis (80) disposed in said casing (100) which chassis can rotate about said second shaft (190), said transducer element (130) rotating together with said chassis (80), so that scanning along a circular plane (400) is performed; a rotating force being transmitted through said second shaft (190) to said transducer element (130) to rotate said transducer element (130) about said first shaft (110), so that a sector plane is scanned and, by combining the two ways of scanning, a hemispherical image of a body can be obtained. An ultrasonic probe according claim 1, characterized in that said rotating means comprises a motor (19), and means for allowing said motor (19) to rotate said supporting member selectively about said first axis and about said second axis. An ultrasonic probe of claim 1, characterized in that, said rotating means comprises a first motor (19), means for allowing said first motor (19) to rotate the supporting member about the first axis, a second motor (19A), and means for allowing said second motor (19A) to rotate said supporting member about said second axis.

Inventors: KAWABUCHI, MASAMI, MURAMATSU, FUMIO
Applicants: MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1987
Main classification: A61B8
IPC codes: A61B8, G10K11