CN1818573A - Energy exchanger of reflecting probe focusing acoustic field - Google Patents

Abstract

A transverter of reflection probe type used for measuring focus sound field consists of reflection probe and focusing transverter .It features that said probe and said transverter are firm-joined on support separately, focusing transverter is set at outside of sound field generated by transducer to be measured and focal point of focusing transverter is set at center of reflection end face on reflection probe.

Description

Energy exchanger of reflecting probe focusing acoustic field

Affiliated technical field

The present invention relates to a kind of device that the performance of HIFU equipment is measured, it mainly is a kind of energy exchanger of reflecting probe focusing acoustic field, it is reflective probe type nautical receiving set, be used for the measurement of sound field that high intensity focused ultrasound HIFU transducer is produced, the acoustic pressure value and the acoustic pressure that can obtain near the burnt territory of transducer distribute.

Background technology

High intensity focused ultrasound High Intensity Focused Ultrasound is called for short the HIFU technology and is developed into Medical Devices at present, is applied to clinical in tumor treatment.When the high sound intensity ultrasound wave focuses in the burnt territory of millimeter magnitude and after affacting tissue, the temperature of tissue risen, thereby reach the effect of treatment.Than traditional surgical intervention method, therefore the misery that HIFU equipment can be avoided and reduce to perform the operation and bring to patient, is subjected to the attention of countries in the world, has obtained fast development in recent years.

Along with the development of HIFU technology, clinical instrumentation just constantly occurs and is applied, and how attention and the concern that is subjected to all circles just day by day measured and identified to the performance of HIFU equipment.Because HIFU equipment utilization ultrasound wave acts on tissue and reaches therapeutic purposes, therefore, the measurement that ultrasonic power, acoustic pressure and acoustic pressure that it produced are distributed seems particularly important.

For medical ultrasound equipment is carried out the detection of acoustical behavior, the researchist of states such as Europe, the United States has invented multiple measuring method, and up to the present, comparatively mostly the measuring method of Pu Jiing is to rely on piezoelectric hydrophone to carry out.Be generally the probe-type nautical receiving set as measuring piezoelectric hydrophone, in this kind nautical receiving set, pressure-active element is placed in an end of tubular probe, directly receives to measure sound wave and be converted into the correspondent voltage waveform.The probe-type nautical receiving set has been brought into play vital role in the detection of diagnostic ultrasound equipment.But the HIFU therapeutic equipment will produce the continuous wave of number MPa, and traditional probe nautical receiving set will be damaged, therefore, various countries still do not have ripe method to come the performance of HIFU equipment is detected at present, and obviously, this improvement for HIFU The Application of Technology and equipment is disadvantageous.

Summary of the invention

Purpose of the present invention is just in order to overcome the deficiency of above-mentioned technology, and a kind of energy exchanger of reflecting probe focusing acoustic field that can measure high-strength focused transducer that provides can solve high strength focused transducer such as HIFU and measure the difficulty that is faced.

The technical scheme that technical solution problem of the present invention adopts: this energy exchanger of reflecting probe focusing acoustic field, mainly comprise reflective probe and focused transducer, described reflective probe, focused transducer are fixedlyed connected with support respectively, focused transducer is arranged at outside the sound field of tested transducer, and the focus of focused transducer is in the center of reflective probe reflection end face.

Technical solutions according to the invention can be further perfect.

Focused transducer of the present invention is fixedly connected on the crossbeam of support upper end, and reflective probe is fixedly connected on the crossbeam of support lower end, the axial angle that becomes 40 °-50 ° of focused transducer acoustic axis and reflective probe wherein, and the angle of the best is 45 °.

Be provided with acoustic lens, pressure-active element and sound absorption backing in the shell of focused transducer of the present invention, wherein the both positive and negative polarity of pressure-active element is connected with output cable by lead.

Reflective probe of the present invention is solid metal or nonmetal cone, and front end is processed into the plane that diameter is 1mm-2mm.

Support of the present invention is provided with connecting link, is installed on the corresponding measurement mechanism by connecting link.

The effect that the present invention is useful is: 1), compare with traditional nautical receiving set that is operated in the megahertz frequency range, receiving transducer has bigger receiving area and electric capacity, can use relatively long cable in the measurement, and can be connected directly on the general measurement instrument equipment, do not need to carry out the correction of receiving sensitivity, therefore, be very easy to measuring operation.2), intercept and capture and press design direction reflection incident acoustic wave by the end face of probe, the focus of receiving transducer is in the center of metal probe reflection end face, both can reach the purpose of effective reception probe reflection signal, simultaneously, because focused transducer has spatial selectivity to the reception of sound wave, also eliminated effectively from of the interference of other regional sound wave, reached effective reception reflective sound wave, eliminated the purpose that other incident acoustic waves disturb with this to measuring.3), traditional probe nautical receiving set directly receives incident acoustic wave by the piezoelectric element that is fixed in the probe, reflective probe type nautical receiving set of the present invention, utilization is inner no longer to be contained the probe intercepting and capturing of piezoelectricity active component and reflects sound wave to be measured, receiving transducer no longer is under the effect of high strength sound wave, thereby avoided the infringement of sound wave, improved the measurement capability of system the high strength sound wave to pressure-sensing device.

Description of drawings:

Fig. 1 is a main TV structure synoptic diagram of the present invention;

Fig. 2 is the structural representation of focused transducer part among the present invention;

Fig. 3 is the axial acoustic pressure distribution schematic diagram of concave surface pressure sensitive focused transducer among the present invention;

Fig. 4 utilizes the present invention to measure the acoustic pressure distribution plan of HIFU transducer on focal plane under the different driving voltage of acquisition;

Description of reference numerals: reflective probe 1, support 2, focused transducer 3, connecting link 4, acoustic lens 5, PZT element 6, metal shell 7, cork-rubber 8, sound absorption backing 9, lead 10, O-ring seal 11, metal plug 12, bonnet 13, output cable 14.

Embodiment

The invention will be described further with enforcement below in conjunction with accompanying drawing:

The structure of this energy exchanger of reflecting probe focusing acoustic field of the present invention (reflective probe type nautical receiving set) as shown in Figure 1.It is made of reflective probe 1, be rigidly connected support 2 and focused transducer 3, and reflective probe 1 is solid metal or nonmetal circular cone, and front end is processed into the plane that diameter is 1mm-2mm.Focused transducer 3 is arranged at outside the sound field of tested transducer and is fixedly connected on the crossbeam of support 2 upper ends, reflective probe 1 is fixedly connected on the crossbeam of support 2 lower ends, connecting support 2 is made by metal or nonmetallic materials with better rigidity, its effect is to make the focus of focused transducer 3 be positioned at the center of reflective probe 1 end face, and makes the acoustic axis of focused transducer and the angle axial at 45 of reflective probe.Described support 2 is provided with connecting link 4, and reflective probe type nautical receiving set is installed on the corresponding measurement mechanism by connecting link 4.Focused transducer 3 is formed by pressure-sensitive made such as PZT or PVDF, by pressure sensitive being processed into concave or using acoustic lens to make transducer have focus characteristics.

Adopt the acoustic lens principle focused transducer 3 structure as shown in Figure 2, it is made of parts such as acoustic lens 5, PZT pressure-active element 6, sound absorption backing 9, lead 10, shell 7 and bonnets 13.Acoustic lens 5 adopts epoxide resin material, and outside surface is processed to the concave spherical surface shape; The PZT pottery is poured in metal shell 7 and is one with epoxy resin acoustic lens 5, sound absorption backing 9, sound absorption backing 9 adopts epoxy tungsten powder material, the both positive and negative polarity of pressure-active element PZT pottery is connected on the output cable 14 by lead 10 and draws, and uses material such as cork-rubber 8 to reduce extraneous vibration to the transducer Effect on Performance between backing 9 and shell 7; By O RunddichtringO 11, metal plug 12 and bonnet 13, transducer is designed to watertight structure.

If pressure sensitive 6 is designed to the concave surface form, focused transducer will no longer need to use acoustic lens, and directly as external radiation face, all the other structures and lens style focused transducer are identical behind concave surface coating one deck epoxide resin material of PZT pottery.

The principle of work of reflective probe type nautical receiving set:

When using reflective probe type nautical receiving set to carry out the measurement of HIFU transducer focusing acoustic field, the reflection end face of probe will place on the tested point of sound field.Incident acoustic wave with end-acted after, will change the direction of propagation and mode of propagation, be the center with the probe end face, be the spherical wave form at space scattering, acoustic pressure maximal value direction is towards focused transducer.Focused transducer will be in outside the sound field of HIFU transducer and receive reflective sound wave, and be converted into the correspondent voltage signal.Because probe is a solid cylinder body structure, can bear high pressure, sound pressure amplitudes significantly reduced when sound wave arrived transducer face through probe reflection, so this kind reflective probe formula nautical receiving set can be applicable to carry out the measurement of high-strength focused sound field.

1.1 probe reflection

Near the focus of HIFU transducer, sound wave will be propagated with the plane wave form.After it acted on the reflection end face of probe, reflection wave was equal to the sound wave of launching with the planar transducer of same diameter, and the acoustic pressure amplitude depends on the material of incident sound wave intensity and probe.

If frequency be the plane wave normal incidence of f in the stainless steel disc surfaces, the reflection back is the r distance at the distance reflecting surface, becomes the sound pressure level at θ angle place can use following formulate with the incident axis:

$P_r(f,r,\mathrm{\θ})=\frac{1}{2}{P}_0\left(f\right)\frac{{\mathrm{ka}}^2}{r}\left(\frac{Z_m-Z_w}{Z_m+Z_w}\right)\left[\frac{2J_1\left(\mathrm{ka}\sin \mathrm{\θ}\right)}{\mathrm{ka}\sin \mathrm{\θ}}\right]---\left(1\right)$

Wherein, J ₁Be first-order bessel function, P ₀Be the plane of incidence wave-amplitude, k is a wave number, and a is the radius of reflective probe; Z _wAnd Z _mBe respectively aqueous medium and reflecting material characteristic impedance.

Therefore, plane sound wave acoustic pressure distribution form in the space after probe reflection is identical with the planar piston transducer with same diameter.

When the plane wave of incident became angle theta with the normal direction of disk, according to reflection law, the angle of cut of reflective sound wave and incident acoustic wave was 2 θ.Therefore, intersect 45 as the axis direction of reflective probe and incident wave, through behind the end face reflection, the principal maximum direction of reflective sound wave will with incident acoustic wave at an angle of 90.For the plane wave that along continuous straight runs is propagated, after through the probe end face reflection, the principal maximum of sound wave will appear at vertical direction.

1.2 focused transducer

The focused transducer emitting sound wave will be assembled on its focus, form stronger acoustic pressure.When this kind transducer is used to receive sound wave, to be received effectively from the sound wave in its burnt territory, be converted to the correspondent voltage signal, and significant difference will appear from other regional sound waves phase place when arriving the sensitive element surface, cause acoustic wave energy to be cancelled out each other, the voltage signal of conversion obviously descends.Therefore, focused transducer has stronger spatial selectivity to the reception of the sound wave in the sound field.

The focused transducer that constitutes with the concave surface piezoelectric is an example, if the radius-of-curvature of pressure sensitive is R, bore is d, and action is h, and sound field distributes and can be formulated as on acoustic axis:

$p\left(x\right)=j{\mathrm{\&rho;}}_0{\mathrm{<figure-callout\; id="0"\; label="c"\; filenames="A20061004977900111.png,A20061004977900112.png"\; state="\{\{state\}\}">c</figure-callout>}}_0\frac{2v_0}{q^{\&prime;}}\sin [k(B-x)/2]\&CenterDot;e^{J\left[(\mathrm{\&omega;t}-k(B+x)/2)\right]}---\left(2\right)$

q′＝1-x/R (3)

$B=\sqrt{{(x-h)}^2+{(d/2)}^2}---\left(4\right)$

Wherein, ρ ₀Be the density of aqueous medium, c ₀Be the velocity of sound in the aqueous medium, v ₀Vibration velocity for the focused transducer surface.Can draw the peaked position of acoustic pressure, just focal position on the axis according to following formula.If d/R=0.45, acoustic pressure distributes as shown in Figure 3 on the axis, and its maximal value appears at x ≈ 0.9R.As use this transducer as receiving hydrophone, will be from the sound wave of the x ≈ 0.9R of focus place by the most effective reception.

1.3 reflective probe type nautical receiving set sensitivity

The sensitivity of reflective probe type nautical receiving set is by the reflection strength of probe, the common decision of sensitivity and the institute of the relative position between probe and the transducer of focused transducer.

The sensitivity of focused transducer is by the characteristic decision of structure, active material and the passive material of transducer.Under the resonance frequency of piezoelectric element can irrespective condition greater than the scattering of the wavelength of measuring the frequency range sound wave, back lining materials and reflections affect far above the radius of frequency of operation, focused transducer, the receiving sensitivity response of transducer will be tending towards smooth.Analyze for convenient, if the center of reflective probe end face is positioned at the sphere center position of focused transducer,, propagate to the focused transducer direction behind the probe end face reflection from the sound wave of HIFU transducer, the sound wave that then arrives focused transducer sensitive element surface will be in same-phase.According to formula (1), the acoustic pressure integration that acts on transducer face can be expressed as:

$\stackrel{\&OverBar;}{P}=2\mathrm{\&pi;}\&CenterDot;a\&CenterDot;r{P}_0\left(f\right)\&CenterDot;\left(\frac{Z_m-Z_w}{Z_m+Z_w}\right)\underset{0}{\overset{\mathrm{\&alpha;}}{\&Integral;}}{J}_1\left(\mathrm{ka}\sin \mathrm{\&theta;}\right)\mathrm{d\&theta;}---\left(5\right)$

In the formula, α is that sound wave is focused half of wave beam angle of release that transducer receives after probe reflection.When wave length of sound λ＞a, (5) formula can further be reduced to:

$\stackrel{\&OverBar;}{P}=\mathrm{\&pi;}{a}^2{P}_0\left(f\right)\&CenterDot;r\&CenterDot;\frac{\mathrm{\&omega;}}{c}(1-\cos \mathrm{\&alpha;})---\left(6\right)$

(6) formula shows, owing to can present more and more stronger spatial direction through the sound wave of probe reflection along with the rising of frequency, more acoustic wave energy will be received by transducer face.Therefore, the sensitivity of reflective probe formula nautical receiving set will increase with the speed of every octave 6dB.But in the actual fabrication process, be subjected to the influence of factors such as probe and focused transducer relative position, the sensitivity of reflective probe type nautical receiving set will be lower than above-mentioned theory result of calculation with gathering way of frequency.

2. use reflective probe type hydrophone measurements:

Hold up company by utilization reflective probe type nautical receiving set the acoustic pressure on the HIFU transducer focal plane to be distributed at Chong Qinghai in September, 2005 and carried out actual measurement, measurement result is seen shown in the accompanying drawing 4.

Measurement is carried out in half anechoic tank,, by anchor clamps the HIFU transducer is fixed in the pond, reflective probe type nautical receiving set is installed in the pond in the coordinate mechanism, this coordinate mechanism can be along X, Y, Z-direction translation, wherein, X-direction overlaps with the acoustic axis direction of HIFU transducer, and Y, Z-direction are vertical with the acoustic axis direction of transducer, and the round dot of coordinate axis is positioned on the focus of transducer.In the measurement, reflective probe type nautical receiving set along continuous straight runs Z axle is done scanning motion, and the motion stepping is 0.2mm; The voltage of input transducer is respectively 200V, 400V, 800V, 1kV, 1.5kV and 1.8kV.

Measurement result shows that the focus diameter of this HIFU transducer is about 2mm, and this result is identical with traditional probe hydrophone measurements, has verified the correctness of new type reflection sonde-type hydrophone measurements thus.Fig. 4 result shows that also this reflective probe type nautical receiving set can use in bigger dynamic range, can measuring amplitude reach the above acoustic pressure of 10MPa, the acoustic pressure amplitude that can detect far above common probe nautical receiving set; What use in the measuring process is continuous wave, and Fig. 4 demonstrates the acoustic pressure distribution results of comparatively desirable HIFU transducer, this experimental result has shown that novel reflective probe type nautical receiving set has better spatial resolving power and stronger antijamming capability, and these features of reflective probe type nautical receiving set make it extremely be suitable for carrying out the measurement of HIFU transducer.

Claims (5)

1, a kind of energy exchanger of reflecting probe focusing acoustic field, mainly comprise reflective probe (1) and focused transducer (3), it is characterized in that: described reflective probe (1), focused transducer (3) are fixedlyed connected with support (2) respectively, focused transducer (3) is arranged at outside the sound field of tested transducer, and the focus of focused transducer (3) is in the center of reflective probe (1) reflection end face.

2, energy exchanger of reflecting probe focusing acoustic field according to claim 1, it is characterized in that: described focused transducer (3) is fixedly connected on the crossbeam of support (2) upper end, reflective probe (1) is fixedly connected on the crossbeam of support (2) lower end, wherein the axial angle that becomes 40 °-50 ° of focused transducer (3) acoustic axis and reflective probe (1).

3, energy exchanger of reflecting probe focusing acoustic field according to claim 1 and 2, it is characterized in that: be provided with acoustic lens (5), pressure-active element (6) and sound absorption backing (9) in the shell (7) of described focused transducer (3), wherein the both positive and negative polarity of pressure-active element (6) is connected with output cable (14) by lead (10).

4, energy exchanger of reflecting probe focusing acoustic field according to claim 1 and 2 is characterized in that: described reflective probe (1) is solid metal or nonmetal cone, and front end is processed into the plane that diameter is 1mm-2mm.

5, energy exchanger of reflecting probe focusing acoustic field according to claim 1 is characterized in that: described support (2) is provided with connecting link (4), is installed on the corresponding measurement mechanism by connecting link (4).

Images