JP2006198162A - Ultrasonic probe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic probe where reception sensitivity of ultrasonic waves is improved. <P>SOLUTION: In the ultrasonic probe, a space sealed with a cap 30 at the distal end of the ultrasonic probe 11 is filled with an ultrasonic transmission medium 34. The ultrasonic transmission medium 34 is composed of polyhydric alcohol or polyether compound being chain hydrocarbon having two or more hydroxyl groups, wherein at least a melting point is ≤20°C and at least a boiling point is ≥180°C, desirably the melting point is ≤10°C and the boiling point is ≥200°C. Since the difference of acoustic impedance between the ultrasonic transmission medium 34 and the cap 30 is reduced, occurrence of reflection of an echo signal between the ultrasonic transmission medium 34 and the cap 30 is reduced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ultrasonic probe that mechanically displaces an ultrasonic transducer and scans a living body with ultrasonic waves.

  In recent years, medical diagnosis using ultrasonic images has been put into practical use in the medical field. An ultrasonic image is obtained by irradiating a necessary part of a living body with an ultrasonic wave from an ultrasonic probe and electrically detecting the echo signal. It is also possible to obtain an ultrasonic tomographic image by irradiating while scanning with an ultrasonic wave, and equipped with a mechanical scanning mechanism that mechanically rotates, swings, or slides an ultrasonic transducer that transmits and receives ultrasonic waves. Ultrasonic probes are also known. When acquiring an in-vivo ultrasound image with such an ultrasound probe, the ultrasound probe is inserted into the forceps hole of the endoscope, and the ultrasound probe is scanned with a camera provided at the tip of the endoscope. This is done while observing where the tip is in the body.

  The ultrasonic transducer includes a piezoelectric element, an electrode, and an acoustic matching layer, and is built in a cap at the tip of the ultrasonic probe. In an ultrasonic probe provided with a mechanical scan mechanism, an ultrasonic transmission medium is filled in a cap so that ultrasonic transmission efficiency is improved and displacement of the ultrasonic transducer is smooth.

The ultrasonic transmission medium is not volatile and is required to have fluidity, and for example, water, carboxymethylcellulose (CMC) aqueous solution, physiological saline, castor oil, liquid paraffin, and the like are used. In order to prevent ultrasonic attenuation during use in a high frequency band of 10 MHz or higher, an ultrasonic probe using an oil mainly composed of fatty acid glyceride as an ultrasonic transmission medium has been proposed (see Patent Document 1). .
JP 2002-345819 A

  Here, since the acoustic impedance (= 1.2 Mrayl) of liquid paraffin mainly used as an ultrasonic transmission medium is lower than the acoustic impedance (= 2.3 Mrayl) of a cap made of polyethylene, There is a problem in that the echo signal returning from the living body is reflected between the cap and the sensitivity is lowered.

  In the ultrasonic probe described in Patent Document 1, ultrasonic attenuation can be prevented by using an oil mainly composed of fatty acid glyceride as an ultrasonic transmission medium, but the acoustic impedance of fatty acid glyceride is 1.29 Mrayl. Therefore, the sensitivity is reduced as in the case of liquid paraffin.

  The present invention has been made in view of the above problems, and an object thereof is to provide an ultrasonic probe capable of improving the reception sensitivity of ultrasonic waves.

  In order to achieve the above object, the present invention mechanically displaces an ultrasonic transducer comprising a piezoelectric element, an electrode, and an acoustic matching layer within a cap filled with an ultrasonic transmission medium. In the ultrasonic probe for scanning ultrasonic waves, a polyhydric alcohol or a polyether compound which is a chain hydrocarbon having two or more hydroxyl groups is used as the ultrasonic transmission medium.

  The polyhydric alcohol or polyether compound preferably has a melting point of 20 ° C. or lower and a boiling point of 180 ° C. or higher.

  The polyhydric alcohol is ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, glycerin, 1,2-butanediol, 1,3-butanediol. It is preferably any one of 1,4-butanediol and 1,5-pentanediol.

  The polyether compound is preferably polyethylene oxide or polyethylene glycol having an average molecular weight of up to 400, polypropylene oxide or polypropylene glycol having an average molecular weight of up to 700, or a derivative thereof.

  According to the ultrasonic probe of the present invention, since the polyhydric alcohol or polyether compound, which is a chain hydrocarbon having two or more hydroxyl groups, is used as the ultrasonic transmission medium. The difference in acoustic impedance between the transmission medium and the cap is reduced, and the ultrasonic reception sensitivity can be improved.

  In FIG. 1, the ultrasonic diagnostic apparatus 2 includes an endoscope 10, an ultrasonic probe 11, and an ultrasonic observer 12. The endoscope 10 is made of a soft member, and includes an insertion portion 13 that is inserted into a living body, an operation portion 14 that is connected to a proximal end portion of the insertion portion 13, and an endoscope monitor (not shown). And a cord 15 to be connected. A camera (not shown) for in-vivo photographing is built in the distal end 13a of the insertion portion 13, and an image photographed by this camera can be observed through an endoscope monitor. .

  The ultrasonic probe 11 is inserted into the forceps hole 16 of the endoscope 10, a sheath 17 made of a flexible member like the insertion portion 13, a translator 18 in which a motor 49 and the like (see FIG. 3) described later are built, And a cord 19 connected to the ultrasonic observation device 12. On the other hand, the ultrasonic observation device 12 includes a monitor 20 that displays an ultrasonic image. Note that the endoscope monitor and the monitor 20 may be combined.

  In FIG. 2, a cap 30 made of polyethylene is attached to the distal end 17 a of the sheath 17, and an ultrasonic transducer 31 is built in the cap 30. The ultrasonic transducer 31 is placed on a pedestal 33 to which a control cable 32 is connected. The control cable 32 includes a flexible shaft 32a and a flexible tube 32b that covers the flexible shaft 32a. The distal end of the flexible shaft 32a is connected to the pedestal 33, and the proximal end thereof is extended into the translator 18, and a predetermined rotational speed (for example, 10 to 40 revolutions) is provided by a motor 49 (see FIG. 3) built in the translator 18. / Second). As a result, the ultrasonic transducer 31 is rotated at a predetermined rotation speed with the flexible shaft 32a as a rotation axis.

  An ultrasonic transmission medium 34 is filled in the space sealed by the cap 30. The ultrasonic transmission medium 34 functions as a lubricating oil that improves the transmission efficiency of the ultrasonic wave and smoothes the rotation of the ultrasonic transducer 31, and has at least a melting point of 20 ° C. or lower and a boiling point of 180 ° C. or higher. More preferably, it consists of a polyhydric alcohol or a polyether compound which is a chain hydrocarbon having two or more hydroxyl groups having a melting point of 10 ° C. or lower and a boiling point of 200 ° C. or higher. In addition, you may use together the oil which has a fatty acid glyceride as a main component as described in Unexamined-Japanese-Patent No. 2002-345819 as needed.

Examples of the polyhydric alcohol include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, glycerin, 1,2-butanediol, 1,3-butanediol, , 4-butanediol, or 1,5-pentanediol is used. Of these, tetraethylene glycol, glycerin and the like having a specific gravity greater than 1 (water) and an oral toxicity LD ₅₀ value of 2000 mg / kg or more are particularly preferably used.

  As an example, when tetraethylene glycol is used as the ultrasonic transmission medium 34, since the acoustic impedance of tetraethylene glycol is 1.85 Mrayl, compared with liquid paraffin (1.2 Mrayl) conventionally used as an ultrasonic transmission medium. Thus, the difference from the acoustic impedance (2.3 Mrayl) of the cap 30 is reduced, and reflection of the echo signal between the ultrasonic transmission medium 34 and the cap 30 is reduced. This improves the reception sensitivity of the echo signal by 10 dB.

Further, as the polyether compound, any one of polyethylene oxide or polyethylene glycol having an average molecular weight of up to 400, polypropylene oxide or polypropylene glycol having an average molecular weight of up to 700, or derivatives thereof (for example, polyether polyol) is used. . Polypropylene oxide or polypropylene glycol may be either diol type or triol type. Among these, polyethylene glycol having an average molecular weight of 200 to 400 and a polypropylene glycol having an average molecular weight of 200 to 700 having a specific gravity greater than 1 (water) and an oral toxicity LD ₅₀ value of 2000 mg / kg or more are particularly preferably used.

  As an example, when polyethylene glycol having an average molecular weight of 200 is used as the ultrasonic transmission medium 34, the acoustic impedance of polyethylene glycol having an average molecular weight of 200 is 1.8 Mrayl. The difference is reduced, and reflection of the echo signal between the ultrasonic transmission medium 34 and the cap 30 is less likely to occur. This improves the reception sensitivity of the echo signal by 10 dB.

  As shown in FIG. 3, the ultrasonic transducer 31 includes, in order from the pedestal 33 side, a ferrite rubber backing material 40, a piezoelectric element 41 made of a thin film of PZT (lead zirconate titanate), and an acoustic matching made of epoxy resin. The layer 42 is configured such that the piezoelectric element 41 is sandwiched between the electrodes 43a and 43b. Wires 44a and 44b are connected to both electrodes 43a and 43b, respectively. The wiring 44b on the electrode 43b side is connected to the ground. On the other hand, the wiring 44 a on the electrode 43 a side is inserted into the control cable 32 and connected to the transmission / reception switching circuit 45 in the translator 18.

  The transmission / reception switching circuit 45 performs ultrasonic transmission / reception switching by the ultrasonic transducer 31 at predetermined time intervals. The transmission / reception switching circuit 45 is connected to a pulse generation circuit 46 and a voltage measurement circuit 47. The pulse generation circuit 46 applies a pulse voltage to the piezoelectric element 41 when generating ultrasonic waves from the ultrasonic transducer 31 (when transmitting ultrasonic waves). Thereby, the ultrasonic transducer 31 generates an ultrasonic wave having a predetermined frequency.

  The voltage measurement circuit 47 measures the voltage generated in the piezoelectric element 41 when an echo signal from a living body is received by the ultrasonic transducer 31 (at the time of receiving an ultrasonic wave). The voltage measurement circuit 47 transmits this measurement result to the controller 48. The controller 48 converts the measurement result transmitted from the voltage measurement circuit 47 into an ultrasonic image and transmits it to the ultrasonic observer 12.

  When acquiring an in-vivo ultrasonic image, the insertion portion 13 of the endoscope 10 into which the ultrasonic probe 11 is inserted into the forceps hole 16 is inserted into the living body, and the inside of the living body is observed by the endoscope monitor. While being done, the required part in the living body is searched. When the distal end 17a of the sheath 17 reaches the required part in the living body and an instruction to acquire an ultrasonic image is given, the ultrasonic transducer 31 is rotated at a predetermined rotational speed with the flexible shaft 32a as the rotation axis. . Then, while transmission / reception of the ultrasonic transducer 31 is switched by the transmission / reception switching circuit 45, an ultrasonic wave is emitted from the ultrasonic transducer 31 by applying a pulse voltage from the pulse generation circuit 46, and the living body is passed through the cap 30. Ultrasonic waves are scanned. Further, an echo signal from the living body is received by the ultrasonic transducer 31, and the voltage generated in the piezoelectric element 41 is measured by the voltage measurement circuit 47.

  The echo signal from the living body reaches the piezoelectric element 41 through the cap 30, the ultrasonic transmission medium 34, and the acoustic matching layer 42. As the ultrasonic transmission medium 34, a chain hydrocarbon having two or more hydroxyl groups. Since the difference in acoustic impedance between the ultrasonic transmission medium 34 and the cap 30 is reduced using the polyhydric alcohol or the polyether compound, the echo signal is transmitted between the ultrasonic transmission medium 34 and the cap 30. Less reflections occur. Therefore, the reception sensitivity of ultrasonic waves can be improved.

  The measurement result of the voltage measurement circuit 47 is transmitted to the controller 48 and converted into an ultrasonic image by the controller 48. The converted ultrasonic image is transmitted to the ultrasonic observation device 12 through the code 19 and displayed on the monitor 20 of the ultrasonic observation device 12.

As described above, since the polyhydric alcohol or polyether compound, which is a chain hydrocarbon having two or more hydroxyl groups, is used as the ultrasonic transmission medium 34, the ultrasonic reception sensitivity can be improved. . Further, after the ultrasonic probe 2 is used, it is necessary to disinfect the insertion portion 13 by heating at 160 ° C., for example, but at least the melting point is 20 ° C. or less and the boiling point is at least 180 ° C., more preferably the melting point is 10 Since a polyhydric alcohol or polyether compound having a boiling point of 200 ° C. or lower and a boiling point of 200 ° C. or higher is used, there is no risk of evaporation during disinfection. Furthermore, if an oral toxicity LD ₅₀ value of 2000 mg / kg or more is used, even if the ultrasonic transmission medium 34 leaks from the cap 30 when the ultrasonic probe 2 is used, there is a risk of affecting the biological function. Absent.

  In the above embodiment, the ultrasonic probe 11 that rotates the ultrasonic transducer 31 with the flexible shaft 32a as the rotation axis has been described as an example. However, the present invention is not limited to this, and the ultrasonic transducer 31 is swung. The present invention can also be applied to an ultrasonic probe that slides and scans a living body with ultrasonic waves.

It is the schematic which shows the structure of an ultrasound diagnosing device. It is an expanded sectional view showing the structure of the tip of an ultrasonic probe. It is explanatory drawing which shows the structure of an ultrasonic transducer, and the electrical structure of a translator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 Ultrasonic diagnostic apparatus 10 Endoscope 11 Ultrasonic probe 12 Ultrasonic observer 30 Cap 31 Ultrasonic transducer 34 Ultrasonic transmission medium 41 Piezoelectric element 42 Acoustic matching layer 43a, 43b Electrode 48 Controller

Claims (4)

In an ultrasonic probe that mechanically displaces an ultrasonic transducer including a piezoelectric element, an electrode, and an acoustic matching layer in a cap filled with an ultrasonic transmission medium, and scans the living body through the cap with ultrasonic waves,
An ultrasonic probe using a polyhydric alcohol, which is a chain hydrocarbon having two or more hydroxyl groups, or a polyether compound as the ultrasonic transmission medium.   The ultrasonic probe according to claim 1, wherein the polyhydric alcohol or the polyether compound has a melting point of 20 ° C. or lower and a boiling point of 180 ° C. or higher.   The polyhydric alcohol is ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, glycerin, 1,2-butanediol, 1,3-butanediol, The ultrasonic probe according to claim 1, wherein the ultrasonic probe is any one of 1, 4-butanediol and 1,5-pentanediol. 3. The polyether compound according to claim 1, wherein the polyether compound is one of polyethylene oxide or polyethylene glycol having an average molecular weight of up to 400, polypropylene oxide or polypropylene glycol having an average molecular weight of up to 700, or a derivative thereof. The described ultrasonic probe.

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