Ultrasonic probe

Abstract: An ultrasonic transducer element is supported by a member. The transducer element and the supporting member are disposed within a casing filled with ultrasonic wave propagation medium. At least part of the casing forms an ultrasonic wave transmission window. In a first case, the casing has a first portion accommodating the transducer element and the supporting member and a second portion 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 second case, a sensor 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 Some medical ultrasonic diagnostic systems produce sectional images of bodies. These systems generally have ultrasonic probes which scan beams of ultrasonic wave pulses to produce sectional images of bodies. There are ultrasonic probes of the mechanically scanning type. Some ultrasonic probes are inserted into and used in coeloms of a body to produce sectional inages of internal organs. As will be described hereinafter, conventional ultrasonic probes have various problems. EP-A-0 039 045 describes an ultrasonic diagnostic apparatus for endoscope, an insert section of which is formed of two rigid cylindrical tubes which are bendably coupled by means of a hinge. The distal tube can be bent freely by operating a control knob at a control section, so that an ultrasonic transducer member at the tip of the distal tube may be brought closely into contact with a body wall. SUMMARY OF THE INVENTION It is a first object of this invention to provide a small ultrasonic probe which can absorb load variations. 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 ultrasonic probe which can produce sectional images over a wide range. It is a fourth object of this invention to provide an easily handleable ultrasonic probe. It is a fifth object of this invention to provide an ultrasonic probe which can produce sectional images in a region where sectional images are generally unavailable heretofore. It is a sixth object of this invention to provide an ultrasonic probe which inflicts an acceptably low level of pain on a patient during insertion of the probe into the body of the patient. It is a seventh object of this invention to provide an ultrasonic probe which allows an excellent yield during manufacture. In an ultrasonic probe according to the invention, an ultrasonic transducer element is supported by a member. A casing has a first portion and a second portion. The first casing portion accommodates the transducer element and the supporting member and is filled with ultrasonic wave propagation medium. At least part of the first casing portion forms an ultrasonic wave trasmission window. The second casing portion extends in rear of the first casing portion and may be narrower than the first casing portion. The probe comprises means for detecting at least one condition related to operation of a mechanism driving the supporting member. Said detecting means comprises means for sensing the load on said driving means, and means for sensing the temperature of said driving means. BRIEF DESCRIPTION OF THE DRAWINGS 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 the invention, but the sensing means are not shown. Fig. 4 is a sectional view of the ultrasonic probe taken along the line VII-VII in Fig. 3. Fig. 5 is a sectional view of an ultrasonic probe according to another embodiment of this invention. Fig. 6 is a diagram of an internal design of the condition sensor unit of Fig. 5. 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 ratatable 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. Figs. 3 and 4 show an ultrasonic probe according to an embodiment of this invention, but the sensing means of the invention is not shown. The ultrasonic probe of Figs. 3 and 4 includes a casing 301 having a drive member accommodating portion 302, a narrow elongated portion 303, and a transducer element accommodating portion 304. A first enlarged end of the elongated portion 303 is connected to the drive member accommodating portion 302 by a connection member 305 fixed to the casing portions 302 and 303 via threads. A second enlarged end of the elongated portion 303 is connected to the transducer element accommodating portion 304. A motor 311 and an encoder 312 are disposed within the casing portion 302. A drive shaft 310 is coaxially disposed within the casing portion 303. An ultrasonic transducer element 306 and a support 307 are disposed within the casing portion 304. At least part of the transducer element accommodating portion 304 is formed with an acoustic window. When the ultrasonic probe is used, it is inserted into a coelom of a body in the direction D (see Fig. 3) corresponding to a longitudinal axis of the casing 301. The transducer element 306 is attached to an outer surface of the support 307. The support 307 is rotatably connected to a frame 308 via a shaft 309 extending perpendicular to the longitudinal axis of the casing 301 or the insertion direction D. The shaft 309 is also perpendicular to the drive shaft 310. The support 307 and the transducer element 306 can rotate about the shaft 309. The frame 308 is supported by the casing portion 303. An end of the drive shaft 310 is rotatably supported by the frame 308. The other end of the drive shaft 310 is connected via a coupling 314 to an output shaft 313 of the motor 311 so that the drive shaft 310 can be rotated by the motor 311. The motor 311 is supported by the connection member 305. A power transmission mechanism connects the drive shaft 310 and the support 307 so that the support 307 rotates about the shaft 309 as the drive shaft 310 rotates. The power transmission mechanism changes the direction of a transmitted rotational force such that the axis of rotation of the support 307 is perpendicular to the axis of rotation of the drive shaft 310. For example, the power transmission mechanism includes a combination of gears 315 and 316. The first gear 315 is fixedly mounted on the end of the drive shaft 310. The second gear 316 is attached to a side of the support 317. The gears 315 and 316 are in mesh. As the motor 311 is activated, the motor shaft 313 and the drive shaft 310 rotate together so that the support 307 and the transducer element 306 rotate together about the shaft 309. The elongated portion 303 and the transducer element accommodating portion 304 are filled with ultrasonic wave propagation liquid 317 composed of deaerated water, butanediol, or others. A sealing member 318 provided between the connection member 305 and the motor shaft 313 prevents leakage of the ultrasonic wave propagation liquid 317. Such a location of the sealing member 318 ensures the narrow design of a major part of the elongated casing portion 303. As shown in Fig. 4, the elongated casing portion 303 includes an outer tube 319 and an inner tube 320 extending coaxially. The outer tube 319 is made of insulating material such as synthetic resin to prevent electric leakage from the ultrasonic probe to an examined body. The inner tube 320 is made of metal to increase the strength of the casing 301. The motor 311 is electrically connected via a cable (no reference character) to a main portion (not shown) of a medical ultrasonic diagnostic system so that the motor 311 is controlled via an electric signal outputted from the main portion of the diagnostic system. The encoder 312 is associated with the motor shaft 313. The encoder 312 generates an electric signal or signals representing the angular position of the motor shaft 313 and the rotational speed of the motor shaft 313. Since the position of the transducer element 306 depends on the angular position of the motor shaft 313, the electric signal outputted by the encorder 312 also represents the position of the transducer element 306. The encoder 312 is electrically connected via the cable to the main portion of the diagnostic system so that the signal or signals are transmitted from the encoder 312 to the main portion of the diagnostic system. The transducer element 306 is electrically connected to the main portion of the diagnostic system so that electric signals are transmitted between the transducer element 306 and the main portion of the diagnostic system. The electrical connection between the transducer element 306 and the main portion of the diagnostic system includes the cable, and leads disposed in the casing 301 and extending between the transducer element 306 and the cable. As shown in Fig. 4, the inner casing tube 320 has an axial hole 321 through which these leads extend. The metal inner tube 320 is electrically grounded to reduce the ingress of foreign noises into signals travelling along the leads. It should be noted that the leads are electrically insulated from the metal inner tube 320 by a suitable insulating arrangement. For example, the transducer element accommodating portion 304 has an outside diameter of about 20 mm and a length of about 30 mm, and the elongated portion 303 has an outside diameter of about 10 mm and a length of about 110 mm. The ultrasonic probe of Figs. 3 and 4 operates as follows. When the ultrasonic probe is used, it is inserted into a coelom of a body to be examined. The narrow design of the casing elongated portion 303 allows much eased pain to be inflicted on a patient during the insertion of the ultrasonic probe into the body of the patient. After the ultrasonic probe is inserted into the body, the motor 311 is activated so that the drive shaft 310 rotates together with the motor shaft 313 and the coupling 314. The rotational force is transmitted from the drive shaft 310 to the support 307 via the gears 315 and 316, thereby rotating the support 307 and the transducer element 306. During the rotation of the transducer element 306, the transducer element 306 is activated so that a beam of ultrasonic wave pulses are emitted from the transducer element 306 into the examined body via the ultrasonic wave propagation liquid 317 and the acoustic window of the casing portion 304. Some of the emitted ultrasonic wave pulses are reflected by the examined body and return to the transducer element 306 via the acoustic window of the casing portion 304 and the ultrasonic wave propagation liquid 317. The transducer element 306 converts the reflected and returned ultrasonic wave pulses into a corresponding electric signal, which is transmitted to the main portion of the diagnostic system. 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. In general, the previously-mentioned operation to derive a display data signal corresponding one scanning line is periodically reiterated while the transducer element 306 is rotated through a desired angle by the motor 311. In this way, the beam of ultrasonic wave pulses emitted from the transducer element 306 is scanned along a sector plane extending frontward of the ultrasonic probe with respect to the insertion direction D, so that a corresponding sector sectional image of the portion of the body extending frontward of the ultrasonic probe is obtained on the display. During this sector scanning process, the main portion of the diagnostic system monitors the position of the transducer element 306 via the signal from the encoder 312 and controls the position of the transducer element 306 in accordance with the monitored information via the signal to the motor 311 in conventional closed loop control. Furthermore, the main portion of the diagnostic system controls the speed of the motor 311 in accordance with the speed signal from the encoder 312 to regulate the speed of rotation of the support 307 and the transducer element 306 at a constant value. Two or more ultrasonic transducer elements 306 may be arranged on the support 307. In this case, the support may be rotated in one direction only. In the case where a single transducer element 306 is provided, the support 307 may be rotated through a given angular range in reciprocatory motion. The mechanical scanning arrangement may be replaced by an electronic scanning system in which the transducer element is of the linear array type, the faced array type, or the convex array type. Figs. 5 and 6 show an ultrasonic probe according to another embodiment of this invention. This embodiment is similar to the embodiment of Figs. 3 and 4 except for design changes described hereinafter. In the embodiment of Figs. 5 and 6, a condition sensor unit 322 disposed within the casing portion 302 generates an electric signal representing conditions related to operation of the motor 311. The condition sensor unit 322 is electrically connected to the main portion of the diagnostic system via the cable so that the electric signal is transmitted from the condition sensor unit 322 to the main portion of the diagnostic system. As shown in Fig. 6, the condition sensor unit 322 includes a load section 323 and a temperature section 324 connected in series with a constant current supply (not shown). An electric line 325 connected between the condition sensor unit 322 and the main portion of the diagnostic system transmits the electric signal from the condition sensor unit 322 to the main portion of the diagnostic system. The load section 323 includes a variable resistor. The resistance of this variable resistor is predetermined as follows. After the assembly of the ultrasonic probe is completed, the motor 311 is driven by a varying drive direct current at a given temperature, and the value of the drive current at which the speed of the motor 311 equals a reference speed is detected. The resistance of the variable resistor is preset so as to correspond to this detected value of the drive current. Accordingly, the electric signal outputted via the electric line 325 represents this detected value of the drive current. The temperature section 324 includes a temperature responsive device or devices such as a diode and a thermistor. The reistance of the temperature section 324 varies with the temperature within the casing portion 302. Accordingly, the electric signal outputted via the electric line 325 represents the temperature within the casing portion 302. The main portion of the diagnostic system includes a phase-locked loop (PLL) circuit which basically serves to control the drive current of the motor 311 in accordance with the signal from the encoder 312 so as to regulate the rotational speed of the support 307 and the transducer element 306 at a constant value. The signal outputted from the condition sensor unit 322 is used in the constant rotational speed control of the support 307 and the transducer element 306 to increase the reliability and the response characteristic of the control. Specifically, the signal outputted from the condition sensor unit 322 is used to compensate variations in the load on the motor 311 caused by dimensional errors of the parts and temperature changes. Accordingly, the PLL circuit can operate effectively and the yield during manufacture can be improved. It should be noted that modification may be made in the embodiment of Figs. 5 and 6. For example, the condition sensor unit 322 may be located at other places. The condition sensor unit 322 may be embedded in the walls of the casing portion 302. One of the load section 323 and the temperature section 324 may be omitted from the condition sensor unit 322.

Claims: An ultrasonic probe comprising: a) an ultrasonic transducer element (306); b) a supporting member (307) for supporting said transducer element (306); c) a casing having a first portion (304) and a second portion (303), said first casing portion (304) accommodating said transducer element (306) and said supporting member (307) and being filled with ultrasonic wave propagation medium (317), wherein at least part of said first casing portion (304) forms an ultrasonic wave transmission window, and said second casing portion (303) extending in rear of said first casing portion (304); d) means for driving said supporting member (307); and e) means (322) for detecting at least one condition related to the operation of said driving means, characterized in that said detecting means comprises means for sensing the load (323) on said driving means, and means for sensing the temperature (324) of said driving means. An ultrasonic probe according to claim 1, characterized in that said temperature sensing means comprises at least one thermistor. An ultrasonic probe according to claim 1, characterized in that said temperature sensing means comprises at least one diode. An ultrasonic probe according to claim 1, characterized in that said load sensing means comprises a variable resistor having a predetermined resistance. An ultrasonic probe according to any one of the preceding claims, characterized by means for allowing the transducer element (306) to emit and receive ultrasonic waves to and from a region extending in front of said first casing portion with respect to a direction (D) of said casing into a body to be examined. An ultrasonic probe according to any one of the preceding claims, characterized in that said second casing portion (303) comprises an outer tube (319) made of synthetic resin and an inner tube (320) made of metal, said inner tube having an axial hole (321) accomodating electric leads connected to said transducer element (306).

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