JPH0337937B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an ultrasonic probe attached to an ultrasonic diagnostic apparatus.

[Technical background of the invention and its problems]

An ultrasonic diagnostic device consists of an ultrasonic probe (hereinafter referred to as a probe), a transmitter, a receiver, a signal processor, and a display. , characteristics are required to efficiently convert electrical power applied during transmission into acoustic power, and to efficiently convert acoustic power returned from the subject during reception into electrical power. Furthermore, in view of the influence that ultrasound waves have on living organisms, the transmitting section is required to provide the maximum electrical power to the probe within a range that does not impair safety. Furthermore, the S/N ratio of the receiver is determined mostly by the noise of the first-stage preamplifier system, and this must be kept to a minimum.

In Figure 1a, the probe and transmitter are shown as simple equivalent circuits, the probe is a parallel circuit with conductance G and susceptance B, and the transmitter is a parallel circuit with a power supply V ₀ , its internal resistance γ, and tuning inductance L. Consists of parallel circuits. Therefore, ^the electrical power P applied to the probe can be expressed as follows, where V is the voltage _{applied across} the probe. Here, V() is the frequency characteristic as shown in Figure 1b, and G() is the frequency characteristic as shown in Figure 1c.
It has the frequency characteristics shown below. As is clear from the equation, the electrical power P applied to the probe
In order to increase V() and G(), the band can be increased.

Figures 2a and 2b schematically show the structure of the probe. The probe includes a piezoelectric body 1 and an electrode 2
(2-1, 2-2), a coating layer 3, an acoustic lens 4, and a backing material 5. When a voltage V is applied to the piezoelectric body 1, electrical power is converted to acoustic power, and sound waves are radiated to the front surface (to the right in the figure) and the rear surface of the piezoelectric body 1. The sound waves radiated to the rear surface are absorbed by the backing material 5. Figure 2a shows the actual usage state of the probe, and the probe is
Since it is in close contact with the subject, the front surface of the acoustic lens 4 has an acoustic impedance Z ₂ =1.5 to 1.6×10 ⁶ Kg/
A subject 6 having a time of m ² sec is placed. Piezoelectric body 1
The sound waves emitted to the front surface of the acoustic lens 4 are slightly reflected at the boundary between the acoustic lens 4 and the subject 6. The sound pressure ratio is expressed as: Sound pressure ratio = | (Z ₂ - Z ₁ )/(Z ₁ + Z ₂ ) | Note that Z ₁ represents the acoustic impedance of the acoustic lens 4.

Next, FIG. 2b shows a case where the probe is not in close contact with the subject 6, for example, a case where the probe is driven but left in the air.
Acoustic impedance of air 7 Z ₃ = 10 ^-5 ×10 ⁶ Kg/
m ² sec, in this case most of the sound waves emitted to the front surface of the piezoelectric body 1 are reflected at the interface between the acoustic lens 4 and the air 7, and therefore the electrical power applied to the probe is The power is no longer transmitted to the outside of the probe. That is, these acoustic powers are absorbed in the backing material 5 or the acoustic lens 4 inside the probe, and finally become heat. There is no problem if the conductance G() and susceptance B() are small, but the G() can be reduced by giving the maximum electrical power to the probe within a range that does not impair safety at the transmitter. As B() becomes larger, the temperature of the probe itself increases due to the heat generated within the probe. and,
If the temperature of the probe itself exceeds body temperature, problems arise, such as giving discomfort or anxiety to the subject, such as the patient or operator, and accelerating thermal deterioration of the probe itself.

[Purpose of the invention]

This invention has been made in view of the above circumstances, and an object of the present invention is to provide an ultrasonic probe that minimizes the temperature rise of the ultrasonic probe by efficiently dissipating the heat generated inside the ultrasonic probe to the outside. With the goal.

[Summary of the invention]

The outline of this invention for achieving the above object is as follows:
In an ultrasonic probe in which various parts that emit ultrasonic waves are built into a probe case, the space other than the space occupied by the various parts in the probe case is filled with a molded member having high thermal conductivity and high electrical insulation. It is characterized by this.

[Embodiments of the invention]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 3 is a sectional view showing an ultrasonic probe which is an embodiment of the present invention.

The ultrasonic probe 20 shown in FIG. Electrodes 2-1 and 2 for driving each ultrasonic transducer 1 are provided on the surface opposite to the backing material 5 and the surface opposite to the backing material 5, respectively.
Furthermore, an acoustic lens 4 is provided on the ultrasonic transducer 1 across the electrode 2-1, and a ground wire 8 connected to the electrode 2-1 and the electrode 2-2 are attached. In a structure in which signal lines 12 connected via a flexible PC board 9 are collectively pulled out as a cable 11, a backing material 5, an ultrasonic transducer 1, an electrode 2-
1, 2-2, a space other than the space occupied by the acoustic lens 4, flexible PC board 9, ground wire 8, and signal line 12 is filled with a molding material 22 having high thermal conductivity and high electrical insulation. Mold member 2
2 must have high thermal conductivity in order to efficiently dissipate heat generated within the ultrasonic probe case 20 to the outside. The reason why the mold member 22 must have high electrical insulation is to prevent the signal line and the ground line from being shorted due to the high voltage pulse applied to the probe, and to prevent the operator from This is to ensure electrical safety for the subject. Mold member 22
In order for the molded member 22 to be said to have high thermal conductivity and high electrical insulation properties, it depends on the relationship with the materials constituting other members such as the probe case 10 and the acoustic lens 4, but normally the molded member 22 has high thermal conductivity and high electrical insulation properties. It is preferable that the thermal conductivity is 20×10 ^-4 cal/cm・sec°C or higher, and the volume resistivity is
It is preferable that it is 10 ¹⁰ Ω·cm or more. Examples of materials having such thermal conductivity and volume resistivity include materials in which boron nitride, ceramic, etc. are mixed into resin such as epoxy.

The thermal equivalent circuit of the ultrasonic probe 20 having the above configuration is as shown in FIG. In Figure 4, Q _l
and Q _B are the amount of heat generated in the acoustic lens and packing material, and Cp, C _l , C _B ,
C _M , C _c and Cair are the heat capacities of the ultrasonic transducer, acoustic lens, backing material, mold member, probe case and air, respectively, and H _p is the thermal resistance between the ultrasonic transducer and the backing material,
H _A is the thermal resistance between the air and the probe case, H _C is the thermal resistance between the probe case and the mold member, H _M is the thermal resistance between the mold member and the packing material, H _B1 , H _B2 are The thermal resistance of bucking material, H _l1 and H _l2 are the thermal resistance of lens material,
H _X is the thermal resistance of the ground wire. As shown in the thermal equivalent circuit of FIG. 4, the amounts of heat Q _B and Q _l generated in the bucking material 5 and the acoustic lens 4, respectively, are released to the outside of the ultrasonic probe via the mold member 22, and the 20 temperature rises can be prevented.

Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment, and can be implemented with appropriate modifications within the scope of the gist of the invention. Needless to say.

〔Effect of the invention〕

According to this invention, since the probe case is filled with a molded member having high thermal conductivity and high electrical insulation, the ultrasonic vibrator, acoustic lens,
It is possible to reduce the thermal resistance between the packing material, etc. and the cable, and as a result, the amount of heat generated can be released to the outside of the ultrasonic probe, and the temperature rise of the ultrasonic probe can be effectively suppressed. can.

[Brief explanation of the drawing]

Figure 1a is an equivalent circuit of the ultrasound probe and transmitter, Figure 1b is a spectrum diagram showing the spectrum of the voltage V applied to the ultrasound transducer, and Figure 1c is the spectrum diagram of the conductance G of the ultrasound transducer. Characteristic diagram showing the ultrasonic characteristics, Figure 2a is a schematic diagram showing the structure of an ultrasound probe in close contact with a subject, Figure 2b is a schematic diagram showing the structure of an ultrasound probe left in the air, Figure 3 FIG. 4 is a sectional view showing an ultrasonic probe which is an embodiment of the present invention, and FIG. 4 is a circuit diagram showing a thermal equivalent circuit of the embodiment. 20...Ultrasonic probe, 22...Mold member.

Claims (1)

[Claims] 1. In an ultrasonic probe in which various members that emit ultrasonic waves are built into a probe case, a space other than the space occupied by the various members in the probe case,
An ultrasonic probe characterized by being filled with a molded member having high thermal conductivity and high electrical insulation. 2. The ultrasonic probe according to claim 1, wherein the mold member is made of boron nitride.