JPH0571252B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an ultrasonic diagnostic apparatus that performs biological diagnosis using ultrasonic waves, and particularly to an ultrasonic diagnostic apparatus with an improved driving method for an ultrasonic probe.

[Technical background of the invention and its problems]

An ultrasonic diagnostic device brings an ultrasound probe equipped with a piezoelectric vibrator such as lead zirconate titanate porcelain (PZT) into contact with a living body, and electrically excites the piezoelectric vibrator to transmit ultrasound to the living body. transmit waves,
At that time, the ultrasound reflected by the acoustic impedance mismatching of the interface between living tissues is received by the same ultrasound probe and converted into an electrical signal, and an ultrasound tomographic image is obtained based on this. It is displayed on a monitor for diagnosis.

Electricity of piezoelectric vibrator in ultrasound probe
Since the acoustic conversion efficiency is very low, typically 10 to 40%, the remaining 90 to 60% of the energy that is not converted into ultrasound results in a relatively large amount of heat being generated within the ultrasound probe as energy loss. .

By the way, the reflectivity of ultrasound increases as the difference in acoustic impedance between interfaces increases, so if you temporarily leave the ultrasound probe in the air during diagnosis, the tip of the ultrasound probe will Due to the considerable difference in acoustic impedance between the air and the air, most of the ultrasound waves are reflected at this air interface. This reflected ultrasonic wave is then converted into an electric signal, but as mentioned above, the conversion efficiency is very low, so it is ultimately converted into heat.

In this way, ultrasound probes generate heat as energy loss, and the surgeon must perform various diagnostic tasks during diagnosis, so it is necessary to keep the ultrasound probe in constant contact with the living body to generate ultrasound waves. It is virtually impossible to break contact between the tip of the probe and the air. On the other hand, turning off the power switch of the device every time the ultrasound probe is left in the air will lead to a decrease in diagnostic efficiency, so it is best to left in the air in
The disadvantage is that a considerable amount of heat is accumulated as energy loss, and the durability of the ultrasonic probe is greatly reduced.

[Purpose of the invention]

The present invention has been made based on the above circumstances, and its purpose is to provide an ultrasonic probe that makes it possible to prevent the durability of an ultrasonic probe from deteriorating due to heat generation without reducing diagnostic efficiency. The objective is to provide diagnostic equipment.

[Summary of the invention]

In order to achieve such an object, the present invention brings an ultrasound probe into contact with a living body, drives the ultrasound probe using an ultrasound drive circuit, transmits ultrasound waves into the living body, and transmits the reflected waves to the living body. In an ultrasonic diagnostic apparatus capable of non-invasively diagnosing the living body by receiving reflected wave information using an ultrasound probe and displaying the reflected wave information, the ultrasound diagnostic apparatus detects that the ultrasound probe is not in contact with the living body. The present invention is characterized in that it comprises a detection means for detecting, and a control means for non-driving the ultrasonic drive circuit when the ultrasonic probe is not in contact with the living body based on the output of the detection means.

[Embodiments of the invention]

The present invention provides a method for transmitting ultrasonic waves at the tip of the ultrasonic probe, such as at the interface between an acoustic lens and an external medium, when the ultrasonic probe is left away from a human body while transmitting ultrasonic waves while in use. The purpose of this invention is to mainly completely prevent the reception of ultrasonic waves due to reflection, etc., and has been achieved by focusing on the following points. That is, let Q be the electro-acoustic conversion efficiency of the piezoelectric vibrator of the ultrasonic probe, and the interface between the tip member of the ultrasonic probe, such as an acoustic lens, and an external medium having a value approximately equal to the acoustic impedance of this acoustic lens. When configured, the energy converted to heat within the ultrasound probe is expressed by the following equation (1).

I ₁ = (1-Q)A+Q(1-y)A +QAxy(1-y)+QAxy ² (1-Q) ...(1) (A is the initially applied electrical energy, x is the energy applied outside the ultrasound probe) The rate at which the ultrasound returns after being reflected, and y is the rate of propagation loss of the ultrasound inside the ultrasound probe.) The first term on the right side is the electro-acoustic conversion when electrical energy is converted to ultrasound. Loss, the second term is the propagation loss within the probe when transmitting ultrasonic waves, the third term is the propagation loss within the probe when receiving ultrasonic waves, and the fourth term is when ultrasonic waves are converted into electrical energy. is the electric-acoustic conversion loss.

Furthermore, when the external medium is air, the energy converted into heat within this ultrasonic probe is expressed by the following equation (2).

I ₂ = (1-Q)A+Q(1-y)A +QAx′y(1-y)+QAx′y ² (1-Q) …(2) Compared to the above equation (1), equation (2) ′ is the only difference. However, when the external medium is approximately equal to the acoustic impedance of the acoustic lens, most of the ultrasonic waves pass through the boundary surface, so x can be approximated to zero, and when the external medium is air, the ultrasonic waves Since most of the ultrasonic waves are reflected at the boundary surface, the above x' can be approximated to 1. Therefore, the difference in thermal energy expressed by the above two equations (I ₂ - I ₁ ), that is, the difference between when the ultrasonic wave is reflected at the boundary surface and when it is external The difference in thermal energy generated within the ultrasonic probe when transmitted into the medium is expressed by the following equation (3).

ΔI = I ₂ - I ₁ = QAy (1-y) + QAy ² (1-Q) ... (3) Therefore, the ultrasound transmitted from the ultrasound probe can be propagated outside the ultrasound probe and absorbed. If possible, the thermal energy generated by the reflected ultrasonic waves, that is, the generation of ΔI described above, can be suppressed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An ultrasonic diagnostic apparatus according to the present invention will be described below according to an embodiment shown in the drawings.

In the figure, UE is an ultrasonic transmitting system, an ultrasonic receiving system,
The main body of the ultrasound diagnostic apparatus is equipped with a signal processing system and an image display system, and is equipped with a monitor MON as the image display system.

The PLB is electrically connected to the ultrasound diagnostic equipment main body UE, and its ultrasound transmitting/receiving surface is in contact with the living body P during diagnosis.It is, for example, an ultrasound probe for linear electronic scanning, and its tip has a piezoelectric transducer, λ /4 matching layer, acoustic lens, etc. Also,
This ultrasonic probe PLB has a temperature sensing element TMH1 such as a thermistor in the λ/4 matching layer at the tip and a part that does not affect normal ultrasonic wave transmission and reception.
TMH2 are buried apart from each other.

AMP1 and AMP2 are temperature sensing elements TMH1 and AMP2, respectively.
This is an amplifier that amplifies the output from TMH2,
CMP1 and CMP2 are comparators that take in the outputs from amplifiers AMP1 and AMP2 and output signals only when their values are between the respective set minimum value E1 and maximum value E2, and GT1 is the comparator CMP
1. It is a gate circuit that generates the logical product of the output signals of CMP2, BF1 is a buffer circuit that generates the negation of the screen stop (freeze) signal from the ultrasound diagnostic equipment main body, and GT2 is the freeze negation signal generated by buffer circuit BF1. This is a gate circuit that creates a logical sum of the signal from the gate circuit GT1 and the signal from the gate circuit GT1, and the output of this gate circuit GT2 is given to the ultrasound diagnostic apparatus main body UE as a pulser-on (ultrasonic transmission system activation) signal.

Next, the operation of this embodiment configured as described above will be explained.

First, when the ultrasonic probe PLB is not in close contact with the body surface of the living body P, that is, when it is left in the atmosphere, the outputs of the temperature sensing elements TMH1 and TMH2 detect a temperature close to the atmospheric temperature, and the amplifiers AMP1 and
Each output level of AMP2 is determined by comparator COM1,
The value does not fall between the set values E1 and E2 of COM2, and as a result, both gate circuits GT1 and GT2 are turned off, and no pulser-on signal is given to the ultrasound diagnostic apparatus main body UE. Therefore ultrasound probe PLB
When the is away from the living body P, no ultrasonic waves are emitted.

When the ultrasonic probe PLB is in close contact with the body surface of the living body P, the outputs of the temperature sensing elements TMH1 and TMH2 detect the body surface temperature, and the output levels of the amplifiers AMP1 and AMP2 are set to the set values of the comparators COM1 and COM2. The value between E1 and E2 is taken, and as a result, the gate circuit GT1 is turned on, and the main body of the ultrasound diagnostic equipment is turned on.
When the UE is not frozen, the gate circuit GT2 opens and gives a pulser-on signal to the ultrasound diagnostic apparatus main body UE. Therefore, when the ultrasound probe PLB is in close contact with the living body P, ultrasound is emitted.

As described above, in this example, the temperature sensing elements TMH1 and TMH2 are embedded in the ultrasonic probe PLB,
Whether or not the ultrasound probe PLB is in contact with the living body P is detected based on temperature information, and ultrasonic waves can be emitted only when the ultrasound probe PLB is in contact with the living body P, thereby eliminating unnecessary driving. The characteristic deterioration caused by the heat generation of the piezoelectric vibrator due to this is suppressed, and power consumption is also reduced.

In addition, temperature-sensitive elements buried apart from each other
Since both output signals of TMH1 and TMH2 are used to determine whether or not the transmitting/receiving surface of the ultrasound probe PLB is in close contact with the living body P, incomplete contact may occur when the ultrasound probe PLB is in uneven contact. can be prevented.

In the above embodiment, two temperature sensing elements are used, but a plurality of them may be used as long as they do not affect the transmission and reception of ultrasonic waves. Alternatively, the pulser-on signal may be directly given to the ultrasound diagnostic apparatus main body UE by the output of the temperature sensing element without referring to the freeze signal. Furthermore, a pressure sensitive element may be used instead of the temperature sensitive element.

The present invention is not limited to the above embodiments, but can be implemented with various modifications without departing from the gist of the present invention.

〔Effect of the invention〕

As described above, according to the present invention, there is provided a detection means for detecting that the ultrasound probe is not in contact with the living body, and an output of the detection means that indicates that the ultrasound probe is not in contact with the living body. Since the present invention includes the control means for disabling the sonic drive circuit, it is possible to provide an ultrasonic diagnostic apparatus that can prevent deterioration of durability due to heat generation of the ultrasonic probe without reducing diagnostic efficiency.

[Brief explanation of the drawing]

The figure is a block diagram showing an embodiment of an ultrasonic diagnostic apparatus according to the present invention. UE...Ultrasonic diagnostic equipment main body, TMH1, TMH2
...Temperature sensing element, AMP1, AMP2...Amplifier, COM
1, COM2... comparator, GT1, GT2... gate circuit, BF1... buffer circuit.

Claims (1)

[Claims] 1. An ultrasonic probe is brought into contact with a living body, and an ultrasonic drive circuit drives the ultrasound probe to transmit ultrasound into the living body, and the reflected wave is transmitted to the ultrasound probe. In an ultrasonic diagnostic apparatus capable of non-invasively diagnosing the living body by receiving reflected wave information and displaying an image, the ultrasound probe detects that the ultrasound probe is not in contact with the living body. and a control means for non-driving the ultrasonic drive circuit when the ultrasonic probe is not in contact with the living body based on the output of the detection means. 2. The ultrasonic diagnostic apparatus according to claim 1, wherein the detecting means is a temperature sensing element provided near the living body contacting surface of the ultrasonic probe. 3. The control means deactivates the ultrasonic drive circuit when a logical sum condition is established between the output of the detection means indicating that the ultrasonic probe is not in contact with the living body and the ultrasonic screen stop (freeze) signal. An ultrasonic diagnostic apparatus according to claim 1, characterized in that: