JP2004294190A - Ultrasonic microscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem of a conventional measuring method that measurement is required to perform twenty first times when data for 100MHz-200MHz are collected by a step of 5MHz, to analyze data of one point. <P>SOLUTION: An impulse comprising frequency components in a wide band, frequency components of 100MHz-200MHz for example is sent from an impulse oscillator 1 to an ultrasonic vibrator 2. Then, the ultrasonic vibrator 2 radiates an ultrasonic wave comprising two or more frequencies on a test piece 5 put on a glass substrate 3 and covered with an ultrasonic transmission medium 4. A reflected wave of the radiated ultrasonic wave is received by the ultrasonic vibrator 2 again. The reflected wave received by the ultrasonic vibrator 2 is received and amplified by a receiver 6, converted from an analog reflection signal to a digital reflection signal by an A/D converter 7, and inputted to a personal computer 8 provided with an acoustic velocity calculation function 8a, a thickness calculation function 8b, and a display transformation function 8c for displaying each output of the velocity function 8a and the thickness calculation function 8b, and results of mathematical operations are displayed on a display 9. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

ここで、Ｃ０は超音波伝播媒体４の音速である。
【０００８】
又、周波数が８０ＭＨｚ程度の短パルスの超音波を用いても、試料５の厚みが１０μｍ 程度では、試料５の表面からの反射波Ａとガラス基板３からの反射波は時間軸上で重なりあい、分離は困難である。そこで、受波信号と周波数領域で解析することにより、ΔｔｄとΔｔｓ を推定する。試料５が無い場合の基板３からのフーリエ変換をＸｒｅｆ（ω）とする。試料５がある場合の受波を、試料５の表面反射とガラス基板の反射面のみの和と仮定すれば、そのフーリエ変換Ｆ（ω）は次式で表される。

ここで、ｋｄとｋｓはガラス基板と試料５の表面からの反射係数である。Ｆ（ω）をＸｒｅｆ（ω）で正規化したスペクトルをＲ（ω）とすれば、これは、

と表される。受波のスペクトルの計算には、高速フーリエ変換（ＦＦＴ）を用いるので、得られる正規化スペクトルも周波数領域において離散化されている。
【０００９】
この離散化されたスペクトル系列を、

と表すと、これらは次式の関係を満たす。

ただし、

である。ここで、ｅは誤差項であり、仮定した２つの反射成分以外の信号成分を表している。又、ｘはモデルパラメータであり、

と表される。重み付けされた誤差の２乗和、すなわちｅＴＧｅ（Ｔ：複素共役転置）を最小にするｘは、次式により求められる。

ここで、Ｑは重み行列であり、│Ｘｒｅｆ（ω）│の値を用いて設定する。フーリエ変換により求めたＲｎをもとに、（１２）式よりモデルパラメータｘを求め、（１０）式及び（１１）式を満たすΔｔｄとΔｔｓを求める。これらを（１）式及び（２）式に代入すれば、試料の音速と厚みが得られる。
【００１０】
このように、本実施例では、インパルス発振器１から出力された複数の周波数を含むインパルスを超音波振動子２に入力し、超音波振動子２から複数の周波数を含む超音波を試料５に照射することにより、その反射波をＡ／Ｄ変換器７でデジタル信号に変換し、そのデータをパーソナルコンピュータ８の音速演算機能８ａ及び厚さ演算機能８ｂで上記の演算処理で演算することにより、１回の超音波の送受信で複数の周波数のそれぞれの周波数における試料５の音速及び厚さを演算により求めることができる。
【００１１】
【発明の効果】
以上説明したように、本発明の超音波顕微鏡は、インパルス発信機から出力された複数の周波数を含むインパルスを超音波振動子に入力し、超音波振動子から複数の周波数を含む超音波を試料に照射することにより、その反射波をデジタル変換し、そのデータをパーソナルコンピュータの音速演算機能及び厚さ演算機能で演算するすることにより、複数の周波数のそれぞれの周波数における試料の音速及び試料の厚さ演算により求めることができるので、１回の超音波の送受信で組織片の各周波数の組織データを求めことができるという利点がある。
【図面の簡単な説明】
【図１】本発明の実施例の超音波顕微鏡のブロック図である。
【図２】図１の装置において音速及び厚さを求める状態を示した図である。
【符号の説明】
１ インパルス発振器
２ 超音波振動子
３ ガラス基板
４ 伝播媒体（水）
５ 試料
６ 受信機
７ Ａ／Ｄ変換器
８ パーソナルコンピュータ
９ 表示装置[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ultrasonic microscope that measures the sound speed of a cut tissue by one ultrasonic irradiation.
[0002]
[Prior art]
Conventionally, when measuring the sound velocity of a tissue with an ultrasonic microscope, for example, a tissue section of 10 μm is set on a slide glass, and measurement is performed while changing the frequency from 100 MHz to 200 MHz in 5 MHz steps with an ultrasonic microscope, and acquired. The frequency indicating the maximum value and the frequency indicating the minimum value are obtained from the data, and the tissue sound velocity is obtained from the logical calculation graph.
[0003]
[Problems to be solved by the invention]
However, in such a measurement method, 21 measurements are required to obtain data at 100 MHz to 200 MHz in 5 MHz steps in order to analyze one point of data, which requires a great deal of time, There was a problem that the instability of the device became an error factor.
[0004]
[Means to solve the problem]
The present invention is an impulse oscillator that oscillates an impulse including a plurality of frequencies, an ultrasonic oscillator that outputs an ultrasonic wave by inputting an impulse output from the impulse oscillator, a glass substrate on which a sample is mounted, A receiver that receives and amplifies reflected waves of ultrasonic waves applied to the glass substrate and the sample from the ultrasonic transducer, and an A / D converter that converts a reflected wave signal from the receiver into a digital signal A sound speed calculation function for calculating the sound speed of the sample from a digital signal output from the A / D converter, a thickness calculation function for calculating the thickness of the sample, and a display conversion for converting the calculated signal into a display signal And a display device for displaying the output of the personal computer.
[0005]
BEST MODE FOR CARRYING OUT THE INVENTION
According to the present invention, an impulse including a plurality of frequencies output from an impulse oscillator is input to an ultrasonic vibrator, and an ultrasonic wave including a plurality of frequencies is irradiated from the ultrasonic vibrator onto a sample, so that a reflected wave is digitally converted. By converting the data into signals and calculating the data with the sound speed calculation function and the thickness calculation function of the personal computer, the sound speed and thickness of the sample at each of a plurality of frequencies can be calculated by one transmission / reception of ultrasonic waves. You can ask.
[0006]
【Example】
FIG. 1 is a block diagram of an ultrasonic microscope according to an embodiment of the present invention. When an impulse including a frequency component of a wide band, for example, 100 MHz to 200 MHz is applied from an impulse oscillator 1 to an ultrasonic transducer 2, an ultrasonic wave is applied. Since the vibrator 2 irradiates the sample 5 covered with the ultrasonic wave propagation medium 4 with the ultrasonic wave including a plurality of frequencies placed on the glass substrate 3, the reflected wave of the irradiated ultrasonic wave is again supersonic. The reflected wave received by the acoustic transducer 2 and received by the ultrasonic transducer 2 is received and amplified by the receiver 6, converted from an analog reflected signal to a digital reflected signal by an A / D converter 7, The calculation function 8a and the thickness calculation function 8b are input to the personal computer 8 having the display conversion function 8c for displaying the output of the sound velocity calculation function 8a and the thickness calculation function 8b. It is shown.
[0007]
Here, the basic principle for determining the sound velocity and Atsumi of a biological sample in a non-contact manner according to the present invention will be described with reference to FIG. 2. First, a sound wave is input to a sample 5 which is a biological tissue placed on a glass substrate 3. And the reflected wave A (SS) from the surface of the sample 5 and the reflected wave B (Sd) from the glass substrate 3 are received by the ultrasonic vibrator 2, and the reflected wave C ( Sref) is received, and the time difference Δtd between the reflected waves BC is a propagation time difference due to the difference between the sound speed of the sample and the sound speed of the propagation medium. The time difference Δts between the reflected waves AC is a propagation time difference generated by inserting the sample 5. The thickness d and the sound velocity c of the sample 5 can be obtained from the following equation based on the difference between the propagation times.

Here, C0 is the sound speed of the ultrasonic wave propagation medium 4.
[0008]
Even when a short pulse ultrasonic wave having a frequency of about 80 MHz is used, when the thickness of the sample 5 is about 10 μm, the reflected wave A from the surface of the sample 5 and the reflected wave from the glass substrate 3 overlap on the time axis. Separation is difficult. Therefore, Δtd and Δts are estimated by analyzing the received signal and the frequency domain. The Fourier transform from the substrate 3 when there is no sample 5 is defined as Xref (ω). Assuming that the received wave in the presence of the sample 5 is the sum of only the surface reflection of the sample 5 and the reflection surface of the glass substrate, the Fourier transform F (ω) is expressed by the following equation.

Here, kd and ks are reflection coefficients from the surface of the glass substrate and the sample 5. Assuming that a spectrum obtained by normalizing F (ω) with Xref (ω) is R (ω), this becomes

It is expressed as Since the fast Fourier transform (FFT) is used to calculate the spectrum of the received wave, the resulting normalized spectrum is also discretized in the frequency domain.
[0009]
This discretized spectral series is

, These satisfy the following relationship:

However,

It is. Here, e is an error term and represents a signal component other than the two assumed reflection components. X is a model parameter,

It is expressed as The sum of squares of the weighted errors, that is, x that minimizes eTGe (T: complex conjugate transpose) is obtained by the following equation.

Here, Q is a weight matrix, which is set using the value of | Xref (ω) |. Based on Rn obtained by Fourier transform, a model parameter x is obtained from Expression (12), and Δtd and Δts satisfying Expressions (10) and (11) are obtained. By substituting these into equations (1) and (2), the sound velocity and thickness of the sample can be obtained.
[0010]
As described above, in the present embodiment, the impulse including a plurality of frequencies output from the impulse oscillator 1 is input to the ultrasonic oscillator 2, and the ultrasonic wave including the plurality of frequencies is irradiated from the ultrasonic oscillator 2 onto the sample 5. Then, the reflected wave is converted into a digital signal by the A / D converter 7, and the data is calculated by the above-described calculation processing by the sound speed calculation function 8 a and the thickness calculation function 8 b of the personal computer 8, whereby 1 The sound speed and thickness of the sample 5 at each of a plurality of frequencies can be obtained by calculation by transmitting and receiving the ultrasonic waves twice.
[0011]
【The invention's effect】
As described above, the ultrasonic microscope of the present invention is configured such that an impulse including a plurality of frequencies output from an impulse transmitter is input to an ultrasonic oscillator, and an ultrasonic wave including a plurality of frequencies is sampled from the ultrasonic oscillator. The reflected wave is converted into a digital signal, and the data is calculated by the sound speed calculation function and the thickness calculation function of the personal computer, whereby the sound velocity of the sample and the thickness of the sample at each of a plurality of frequencies are calculated. Since it can be obtained by calculation, there is an advantage that tissue data of each frequency of a tissue piece can be obtained by one transmission / reception of ultrasonic waves.
[Brief description of the drawings]
FIG. 1 is a block diagram of an ultrasonic microscope according to an embodiment of the present invention.
FIG. 2 is a diagram showing a state in which a sound speed and a thickness are obtained in the apparatus of FIG. 1;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Impulse oscillator 2 Ultrasonic transducer 3 Glass substrate 4 Propagation medium (water)
5 Sample 6 Receiver 7 A / D converter 8 Personal computer 9 Display device

Claims (2)

An impulse oscillator that oscillates an impulse including a plurality of frequencies, an ultrasonic oscillator that outputs an ultrasonic wave by inputting an impulse output from the impulse oscillator, a glass substrate on which a sample is mounted, and the ultrasonic vibration A receiver that receives and amplifies reflected waves of the ultrasonic wave applied to the glass substrate and the sample from a probe, an A / D converter that converts a reflected wave signal from the receiver into a digital signal, A sound speed calculation function for calculating the sound speed of the sample from a digital signal output from the / D converter, a thickness calculation function for calculating the thickness of the sample, and a display conversion function for converting the calculated signal into a display signal are provided. An ultrasonic microscope comprising: a personal computer; and a display device for displaying an output of the personal computer.

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