JPH0614927B2 - Method of constructing tomographic image of subject - Google Patents
Method of constructing tomographic image of subjectInfo
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- JPH0614927B2 JPH0614927B2 JP59238804A JP23880484A JPH0614927B2 JP H0614927 B2 JPH0614927 B2 JP H0614927B2 JP 59238804 A JP59238804 A JP 59238804A JP 23880484 A JP23880484 A JP 23880484A JP H0614927 B2 JPH0614927 B2 JP H0614927B2
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- sound
- wave
- subject
- sound pressure
- tomographic image
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Description
【発明の詳細な説明】 技術分野 本発明は、被検体断層像構成方法に関する。TECHNICAL FIELD The present invention relates to a method for constructing a tomographic image of a subject.
従来技術 超音波ＣＴ（Computer Tomography）は、超音波に対す
る被検体の減衰分布や音速分布についての断層像を得る
ものとして知られているが、生体組織のダイナミックス
に関する重要な情報を有する非線形パラメータ分布を得
るように構成されたトモグラフィは未だ提案されていな
い。2. Description of the Related Art Ultrasonic CT (Computer Tomography) is known as a method for obtaining a tomographic image of an attenuation distribution and a sound velocity distribution of a subject with respect to ultrasonic waves, but a non-linear parameter distribution having important information on the dynamics of a living tissue. No tomography adapted to obtain ## EQU1 ## has been proposed yet.
目 的 本発明は、上述のごとき実情に鑑みてなされたもので、
特に、生体等における非線形パラメータ(β)の分布のあ
る積断面における断層像を得ることを目的としてなされ
たものである。The present invention was made in view of the above-mentioned actual circumstances,
In particular, this is done for the purpose of obtaining a tomographic image in a cross section having a distribution of the nonlinear parameter (β) in a living body or the like.
構 成 本発明は、上記目的を達成するために、被検体に対して
周波数の異なる２つの超音波を送波し、被検体透過後の
前記２つの超音波のうち少なくとも一方の超音波の音圧
と該２つの超音波の差音波の音圧を測定し、前記超音波
の音圧の測定値と差音波の音圧の測定値から被検体の断
層像を構成し、前記超音波の音圧の測定値から該音圧の
減衰分布を求め、前記減衰分布により、差音波音圧によ
り構成した被検体の断層像を補正することを特徴とした
ものである。以下、本発明の実施例に基づいて説明す
る。In order to achieve the above-mentioned object, the present invention transmits two ultrasonic waves having different frequencies to a subject, and at least one of the two ultrasonic waves transmitted through the subject is a sound of the ultrasonic wave. Pressure and the sound pressure of the difference sound wave of the two ultrasonic waves are measured, and a tomographic image of the subject is constructed from the measurement value of the sound pressure of the ultrasonic wave and the measurement value of the sound pressure of the difference sound wave. The attenuation distribution of the sound pressure is obtained from the measured pressure value, and the tomographic image of the subject constituted by the sound pressure difference acoustic wave is corrected by the attenuation distribution. Hereinafter, description will be given based on examples of the present invention.
第１図は、本発明による被検体断層像構成方法（超音波
非線形パラメータＣＴ）の一一実施例を説明するための
構成図で、図中、１はプロジエクタ、２はレシーバ、３
は被検試料で、スキニヤングは従来のＣＴシステムと同
様である。すなわち、プロジエクタ１とレシーバ２を同
期して矢印Ａ方向にスキャンし、スキャン終了後に例え
ば０点を中心に所定角度回転して前記と同様に矢印Ａ方
向にスキャンし、以降、同様の操作を３６０゜の角度に
わたって行う。而して、本発明による非線形パラメータ
ＣＴが従来のＣＴと異なる点は、プロジエクタ１から異
なる２つの周波数ｆ１，ｆ２をもつ音波が放射され（実
際には、ＡＭもしくはＤＳＢ）、レシーバ２で、ｆ１，
ｆ２，ｆｓ（＝｜ｆ１−ｆ２｜）の３種の音波（もしく
は、ｆ１（又はｆ２）とｆｓの２種）を測定することで
ある。よって、レシーバ２には２つのトランスジューサ
を用いるか、もしくは、広帯域なハイドロフオンを用い
る。FIG. 1 is a block diagram for explaining an embodiment of a method for constructing a tomographic image of a subject (ultrasonic nonlinear parameter CT) according to the present invention, in which 1 is a projector, 2 is a receiver, and 3 is a receiver.
Is a test sample, and Skinny Young is similar to the conventional CT system. That is, the projector 1 and the receiver 2 are synchronously scanned in the arrow A direction, and after the scanning is completed, for example, a predetermined angle is rotated around the 0 point and the scan is performed in the arrow A direction as described above. Over an angle of °. Therefore, the non-linear parameter CT according to the present invention is different from the conventional CT. Sound waves having two different frequencies f 1 and f 2 are emitted from the projector 1 (actually AM or DSB), and the receiver 2 , F 1 ,
It is to measure three kinds of sound waves of f 2 and fs (= | f 1 −f 2 |) (or two kinds of f 1 (or f 2 ) and fs). Therefore, the receiver 2 uses two transducers or a wide band hydrophone.
この時、測定される差音波音圧（被検体を透過した２つ
の周波数成分の音圧の差）Ｐｓ（ｕ，θ）（Projection
Data）は、第１図の座標系で、 ただし、 ρｏ，Ｃｏ：一定，ωｓ：差音の角周波数 Ｓｏ：プロジエクタの放射面積 Ｐｏ１，Ｐｏ２：１次波の初期音圧 (1)式は、更に、 で、Ｐ１，Ｐ２は、レシーバで測定される１次波の音圧
である。At this time, the sound pressure difference sound pressure (the difference between the sound pressures of the two frequency components transmitted through the subject) Ps (u, θ) (Projection
Data) is the coordinate system of Fig. 1, However, ρo, Co: constant, ωs: angular frequency of the difference sound So: radiation area of the projector Po 1 , Po 2 : primary sound pressure of the primary wave (1) Where P 1 and P 2 are the sound pressure of the primary wave measured by the receiver.
(2)式において、α１，α２＞＞αｓと考えると、 (3)式において、 Ｐｓ（ｕ，θ）……プロジエクション， Ｖ−ｖ……拡散項， である。Considering α1 and α2 >> αs in the equation (2), In the equation (3), Ps (u, θ) ... projection, Vv ... diffusion term, Is.
ここで、Ｐｓｃ（ｕ，θ）＝Ps/P1・Ｐ２を求め、Ｐｓ
ｃ（ｕ，θ）を再構成（reconstruct）すると、拡散、
減衰の影響により、真の非線形パラメータ分布β（Ｘ，
Ｙ）を得ることができないので、補正が必要である。補
正方法としては、Single Photon EmissionＣＴに用い
られているＭＣＭ法を用いる。Here, Psc (u, θ) = Ps / P 1 · P 2 is obtained, and Ps
When c (u, θ) is reconstructed, diffusion,
Due to the effect of damping, the true nonlinear parameter distribution β (X,
Since Y) cannot be obtained, correction is necessary. As a correction method, the MCM method used in Single Photon Emission CT is used.
第２図は、上記補正の流れを示すフローチヤートであ
り、ここで、Ｃ（Ｘ，Ｙ）は補正係数行列であり、次の
(4)式で与えられる。FIG. 2 is a flow chart showing the flow of the above correction, where C (X, Y) is a correction coefficient matrix, and
It is given by equation (4).
ただし、θは投影角、θは投影角θのときの被検試料
３内の点（Ｘ，Ｙ）からレシーバまでの線分を示す。 Here, θ is the projection angle, and θ is the line segment from the point (X, Y) in the sample 3 to be tested to the receiver at the projection angle θ.
(4)式は、物理的には、被検試料３内の点（Ｘ，Ｙ）に
単位点音源を設定し、減衰が無く、しかも拡散も無いと
仮定したときの再構成値と、それらの影響を受けたとき
の再構成値との比を点（Ｘ，Ｙ）の補正係数と定めるこ
とを意味している。なお、α１（Ｘ，Ｙ），α２（Ｘ，
Ｙ）は、１次波から再構成されたものを用いる。また、
再構成に用いる再構成アルゴリズむには、現在最も普及
しているShepp＆Loganのフイルタで補正した逆投影法を
用いるとよい。Equation (4) physically represents the reconstructed values when a unit point sound source is set at a point (X, Y) in the sample 3 to be tested, and there is no attenuation and no diffusion, and It means that the ratio with the reconstruction value when affected by is determined as the correction coefficient of the point (X, Y). Note that α 1 (X, Y), α 2 (X, Y
For Y), the one reconstructed from the primary wave is used. Also,
For the reconstruction algorithm used for reconstruction, it is recommended to use the back projection method corrected by the Shepp & Logan filter, which is the most popular at present.
次に、β分布ＣＴの測定計算手順を示す。Next, the procedure for measuring and calculating the β distribution CT will be described.
(1)、プロジエクションＰ１，Ｐ２を測定 (2)、プロジエクションＰｓを測定 (3)、プロジエクションＰ１，Ｐ２の測定値を用いてＣ
Ｔアルゴリズムにより減衰分布α１（Ｘ，Ｙ），α
２（Ｘ，Ｙ）を再構成する。(1), measure the projections P 1 and P 2 (2), measure the projection Ps (3), use the measured values of the projections P 1 and P 2 to calculate C
Damping distribution α 1 (X, Y), α by T algorithm
2 Reconstruct (X, Y).
(4)、Ｐ１，Ｐ２，ＰＳの測定値を用いてプロジエクシ
ョンの補正値 (5)、上記(4)で求めたプロジエクションの補正値を用い
てＣＴアルゴリズムにより の再構成を計算 (6)、Ｃ（Ｘ，Ｙ）を計算 (7)、上記(5)で求めた再構成（Reconstruction）ＸＣ
（Ｘ，Ｙ）よりβ分布を求める。 (4), P 1, P 2, the correction value of the pro-diethyl transfection using measurements of PS (5), by the CT algorithm using the correction value of projection obtained in (4) above (6), C (X, Y) is calculated (7), and the reconstruction XC obtained in (5) above is calculated.
The β distribution is obtained from (X, Y).
第３図は、上記超音波ＣＴの原理を用いて被検試料片の
非線形パラメータ値を測定するシステムの一例を示す図
で、図中、１１は容器、１２は水、１３は送波用超音波
トランスジューサ、１４は受波用ハイドロフォン、１５
は試料片で、試料片として、生体（Tissue Charactiri
gation）の非線形パラメータ値(β)を求める例について
説明する。FIG. 3 is a diagram showing an example of a system for measuring the non-linear parameter value of a sample piece to be tested using the principle of the above-mentioned ultrasonic CT. In the figure, 11 is a container, 12 is water, and 13 is a transmitting ultrasonic wave. Sound wave transducer, 14 is a hydrophone for receiving waves, 15
Is a sample piece, and as a sample piece, a living body (Tissue Charactiri
An example of obtaining the nonlinear parameter value (β) of gation) will be described.
生体組織の弾性特性を反映していると思われる非線形パ
ラメータ(β)は、生体変質の様子を知る上で重要なパラ
メータであると考えられている。この生体のβ値の測定
法として、従来、有限振幅超音波の高調波音圧を測定
し、これからβ値を計算する方法と、超音波信号波に有
限振幅レベルのポンプ波をあてて位相変調を起させ、こ
れをフーリエー変換してβ値を計算する方法がある。但
し、前者の方法は高調波を利用しているため、生体内で
の減衰が激しくハイドロフォンによる検出が難しい。後
者の方法は、ポンプ波として正弦波のスキャンまたはパ
ルスを用いているので広帯域のトランスデューサが必要
であるが、実用的に満足なトランスデューサを得るのが
難しい等の欠点があり、今だに、簡便で正確なβ値の計
測法が得られていない。The non-linear parameter (β), which is considered to reflect the elastic properties of biological tissues, is considered to be an important parameter for understanding the state of biodeterioration. As a method of measuring the β value of this living body, conventionally, a method of measuring the harmonic sound pressure of a finite amplitude ultrasonic wave and calculating the β value from this, and applying a pump wave of a finite amplitude level to the ultrasonic signal wave to perform phase modulation There is a method of calculating the β value by causing it to be Fourier transformed. However, since the former method uses harmonics, it is difficult to detect with a hydrophone because it is heavily attenuated in vivo. The latter method requires a wideband transducer because it uses a sinusoidal scan or pulse as the pump wave, but it has the drawback that it is difficult to obtain a transducer that is practically satisfactory. Therefore, an accurate method of measuring β value is not available.
第３図は、音波に対する減衰分布及びβ分布が均一な試
料片のβ値を計測する簡便で正確な計測方法を説明する
ための構成図で、図示のように、水１２中において対向
して送波用超音波トランスデューサ１３と受波用ハイド
ロフォン１４を設置し、その間の空間に被測定物である
試料片１５を配置されている。図示状態で送波用超音波
トランスデューサ１３より角周波数ω｜およびω２の２
つの超音波を同時に有限振幅レベルでビーム状に放射
し、水１２及び被検物生体１５の非線形特性に基づいて
生起する非線形相互作用の結果生じる差音（ω１〜
ω２）の音圧レベルを測定する。この場合、送波用トラ
ンスデューサ１１から放射される音波がビーム状にコリ
メートされるようにω１，ω２の角周波数とトランデュ
ーサの口径を調整するものとする。非線形相互作用の特
徴として、１次波（ω１，ω２）がビーム状であれば差
音（ω１，ω２）も十分にコリメートされることにな
る。FIG. 3 is a configuration diagram for explaining a simple and accurate measurement method for measuring the β value of a sample piece having a uniform attenuation distribution and β distribution with respect to a sound wave. An ultrasonic transducer 13 for wave transmission and a hydrophone 14 for wave reception are installed, and a sample piece 15 as an object to be measured is arranged in a space between them. Angular frequency omega from transmitting ultrasonic transducer 13 in the illustrated state | and omega 2 of 2
Two ultrasonic waves are simultaneously radiated in a beam shape at a finite amplitude level, and a difference sound (ω 1 ~) generated as a result of a nonlinear interaction generated based on the nonlinear characteristics of the water 12 and the living body 15 to be inspected.
The sound pressure level of ω 2 ) is measured. In this case, the angular frequencies of ω 1 and ω 2 and the diameter of the transducer are adjusted so that the sound wave radiated from the transmitting transducer 11 is collimated into a beam. As a characteristic of the non-linear interaction, if the first-order waves (ω 1 , ω 2 ) are beam-shaped, the difference sound (ω 1 , ω 2 ) is also sufficiently collimated.
今、試料片のβ分布とα分布（減衰分布）が一様、均一
であるとすると、ハイドロフォンにて受波する差音の音
圧は次式のごとくなる。Now, assuming that the β distribution and the α distribution (attenuation distribution) of the sample piece are uniform and uniform, the sound pressure of the differential sound received by the hydrophone is given by the following equation.
ただし、(5)，(6)式において、 Ｓｏ：送波トランスデューサの面積 Ｒｏ：トランスデューサとハイドロフォン間の距離 ωｓ：差音の角周波数（＝ω１，ω２） ｋｓ：差音波の波数 Ｐｏ：１次数の初期音圧 (x)：密度分布 Ｃ(x)：音速分布 α(x)：１次波の減衰定数分布 αｓ(x)：差音の減衰定数分布 β(x)：非線形パラメータ分布 上記(5)式が示すように、Ｐｓはρ(x)Ｃ(x)が一定とす
ると、初期音圧Ｐｏを一定に保つことにより非線形パラ
メータβだけに依存することになる。今、第３図のごと
き配置を考えると、Ｃ(x)，ρ(x)はそれぞれ水中および
試料片中で一定であり、α(x)，αｓ(x)も水中で一定で
あると考えられ、試料片中においてもそれぞれ一定と仮
定している。したがって、 水中の音速：Ｃω 水の密度 ：ρω 水の非線下パラメータ：βω 水中の音波減衰定数：αω（１次波），αｓω（差音） 試料片中の減衰定数：αＡ（１次波），αｓＡ（差音） 試料片中の非線形パラメータ：βＡ 試料片中の密度 ：ρＡ とおくことができる。この場合(5)式からβＡは次のよ
うに考える。。 However, in the equations (5) and (6), So: area of the wave transmission transducer Ro: distance between the transducer and the hydrophone ωs: angular frequency of the difference sound (= ω 1 , ω 2 ) ks: wave number of the difference sound wave Po -1st order initial sound pressure (x): Density distribution C (x): Sound velocity distribution α (x): First-order damping constant distribution αs (x): Difference sound damping constant distribution β (x): Non-linear parameter Distribution As shown by the above equation (5), Ps depends only on the nonlinear parameter β by keeping the initial sound pressure Po constant when ρ (x) C (x) is constant. Considering the arrangement as shown in FIG. 3, it is considered that C (x) and ρ (x) are constant in water and the sample piece, respectively, and α (x) and αs (x) are also constant in water. Therefore, it is assumed that the sample pieces are constant. Therefore, sound velocity in water: Cω water density: ρω non-linear parameter of water: βω sound wave attenuation constant in water: αω (first order wave), αsω (difference sound) attenuation constant in sample piece: α A (first order) Wave), α s A (difference tone) Non-linear parameter in sample piece: β A Density in sample piece: ρ A In this case, β A is considered as follows from the equation (5). .
(7)式において、差音の音圧Ｐｓは測定値であり、それ
以外のパラメータは既知であるので、 (7)式の数値積分を実施することにより非線形パラメー
タ値βが求まる。ここにおいてαω，αｓωは既知であ
るが、試料片の減衰パラメータαＡ，αｓＡの測定は以
下の手順になる。 In the equation (7), the sound pressure Ps of the difference sound is a measured value, and the other parameters are known, so that the nonlinear parameter value β can be obtained by performing the numerical integration of the equation (7). Here, αω and αsω are known, but the measurement of the attenuation parameters α A and αs A of the sample piece follows the procedure below.
但し、Ｐω：水のみの時の受波音圧，ＰＡ：試料片を挿
入した時の受波音圧，ＰｓＡ，Ｐｓωについても同様
（但し、周波数はωｓを用いる）。 However, the same applies to Pω: the received sound pressure when only water is used, P A : The received sound pressure when the sample piece is inserted, Ps A , and Psω (however, ωs is used as the frequency).
効 果 以上の説明から明らかなように、本発明によると、従
来、不可能であった生体のダナミック特性を表わすβ分
布のＣＴ像を得ることができる。また、本発明の動作原
理である非線形パラメトリック作用によって生じる差音
を検出することによって距離減衰が少なく、大きな試料
片のβ値の測定が可能となる。Effects As is clear from the above description, according to the present invention, it is possible to obtain a CT image of β distribution which represents the dynamic characteristics of a living body, which has been impossible in the past. Further, by detecting the difference sound generated by the non-linear parametric action which is the operating principle of the present invention, the distance attenuation is small and the β value of a large sample piece can be measured.
第１図は、本発明の一実施例を説明するための構成図、
第２図は、本発明の動作説明をするためのフローチャー
ト、第３図は、本発明の応用例を説明するための図であ
る。 １……プロジエクタ（超音波トランスジューサ）、 ２……ハイドロフォン（超音波レシーバ）、３……被検
試料。FIG. 1 is a block diagram for explaining an embodiment of the present invention,
FIG. 2 is a flow chart for explaining the operation of the present invention, and FIG. 3 is a diagram for explaining an application example of the present invention. 1 ... Projector (ultrasonic transducer), 2 ... Hydrophone (ultrasonic receiver), 3 ... Test sample.
Claims (1)
波を送波し、被検体透過後の前記２つの超音波のうち少
なくとも一方の超音波の音圧と該２つの超音波の差音波
の音圧を測定し、前記超音波の音圧の測定値と差音波の
音圧の測定値から被検体の断層像を構成し、前記超音波
の音圧の測定値から該音圧の減衰分布を求め、前記減衰
分布により、差音波音圧により構成した被検体の断層像
を補正することを特徴とする被検体断層像構成方法。1. An ultrasonic wave having different frequencies is transmitted to a subject, and a sound pressure of at least one of the two ultrasonic waves after passing through the subject and a difference between the two ultrasonic waves. The sound pressure of the sound wave is measured, a tomographic image of the subject is constructed from the measured value of the sound pressure of the ultrasonic wave and the measured value of the sound pressure of the differential sound wave, and the tomographic image of the sound pressure is measured from the measured value of the sound pressure of the ultrasonic wave. A method for constructing a tomographic image of a subject, characterized by obtaining an attenuation distribution and correcting the tomographic image of the subject formed by the sound pressure difference of the sound wave by the attenuation distribution.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP59238804A JPH0614927B2 (en) | 1984-11-13 | 1984-11-13 | Method of constructing tomographic image of subject |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP59238804A JPH0614927B2 (en) | 1984-11-13 | 1984-11-13 | Method of constructing tomographic image of subject |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS61115542A JPS61115542A (en) | 1986-06-03 |
| JPH0614927B2 true JPH0614927B2 (en) | 1994-03-02 |
Family
ID=17035534
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP59238804A Expired - Lifetime JPH0614927B2 (en) | 1984-11-13 | 1984-11-13 | Method of constructing tomographic image of subject |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0614927B2 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1935346A1 (en) * | 2006-12-21 | 2008-06-25 | Stichting voor de Technische Wetenschappen | Imaging apparatus and method |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5955245A (en) * | 1982-09-25 | 1984-03-30 | 富士通株式会社 | Ultrasonic diagnostic treatment system |
| JPS6010165A (en) * | 1983-06-30 | 1985-01-19 | Fujitsu Ltd | Apparatus for measuring ultrasonic non-linear parameter distribution |
-
1984
- 1984-11-13 JP JP59238804A patent/JPH0614927B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPS61115542A (en) | 1986-06-03 |
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