JP2004041324A - Ultrasonograph - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately measure nonlinear characteristics of biological tissues in an ultrasonograph. <P>SOLUTION: A first composite wave shown in (a) is obtained by combining a superimposed wave with the positive amplitude portion of a carrier wave. A second synthetic wave shown in (b) is obtained by combining a superimposed wave with the negative amplitude portion of a carrier wave. When the synthetic waves are radiated to an organism, the waveform of the carrier wave is strained, following a propagation distance. The amount of strain is measured by a positional difference on the time base of the superimposed wave. In that case, a phase difference detection for example is performed. Since the superposing wave can be used as a marker, the strain of the carrier wave can be accurately detected. <P>COPYRIGHT: (C)2004,JPO

Description

また、図１の（ｂ）には、低周波数をもった超音波パルス波（搬送波）ｆ_２（ｔ）の波形が示されている。この搬送波ｆ_２（ｔ）は、以下の（２）式によって表される。
【００２７】
【数２】

生体内には、搬送波と重畳波と合成した合成波Ｕ（ｔ）が送波される。図１の（ｃ）には、合成波Ｕ（ｔ）の波形が示されている。この合成波Ｕ（ｔ）は、以下の（３）式によって表される。
【００２８】
【数３】

合成波Ｕ（ｔ）において、搬送波ｆ_２（ｔ）は大きな振幅を有し、伝搬媒質（生体組織）の非線形特性の影響を十分に受ける。一方、重畳波ｆ_１（ｔ）は小さな振幅を有し、伝搬媒質の非線形特性の影響をあまり受けない。
【００２９】
ここで、合成波Ｕ（ｔ）の生体組織中の伝搬に伴って、搬送波ｆ_２（ｔ）における正振幅部分は、音速が大きくなり、負振幅部分は、音速が小さくなる。つまり、波形が歪む。その際、重畳波ｆ_１（ｔ）は、搬送波ｆ_２（ｔ）の波形の歪みの影響を受け、その重畳波ｆ_１（ｔ）についても、上記同様に、その伝搬速度が変化する。
【００３０】
線形領域での音の伝搬速度をｃとすると、上記の負振幅部分については、その音速がｃよりもｖ_ｎだけ小さくなり、ｃ_ｎ＝ｃ−ｖ_ｎとなる。一方、上記の正振幅部分については、その音速がｃよりもｖ_ｐだけ速くなり、ｃ_ｐ＝ｃ＋ｖ_ｐとなる。
【００３１】
図２の（ａ）には、第１合成波Ｕ_ｐ（ｔ）の波形が示され、図２の（ｂ）には、第２合成波Ｕ_ｎ（ｔ）の波形が示されている。第１合成波Ｕ_ｐ（ｔ）は、搬送波の正振幅部分の（山の）頂点に重畳波が合成されてなる波形である。第２合成波Ｕ_ｎ（ｔ）は、搬送波の負振幅部分の（谷の）頂点に重畳波が合成されてなる波形である。
【００３２】
まず、第１合成波Ｕ_ｐ（ｔ）について見ると、それが非線形媒体中を進行するのに伴って、搬送波の波形が正弦波から三角波に近づくように歪む（Ｎ字形に近づく）。この際、重畳波の位置も、搬送波の歪みの影響を受けて、搬送波の歪み方向へ移動する。つまり、重畳波の伝搬速度が大きくなり、時間軸上では、重畳波の観測時間が早まる。なお、図２の（ｃ）には、第１合成波Ｕ_ｐ（ｔ）から搬送波成分を除外し、重畳波成分のみを表した波形が示されている。図２の（ｄ）には、第２合成波Ｕ_ｎ（ｔ）から搬送波成分を除外し、重畳波成分のみを表した波形が示されている。
【００３３】
ここで、第１合成波Ｕ_ｐ（ｔ）について、超音波振動子より距離ｌだけ離れた位置にある反射体へそれが到着する時間ｔ_ｐｆは、以下のとおりである。
【００３４】
【数４】

その位置で反射した反射波は小振幅であるので、反射波についての非線形効果を事実上無理できるとすると、超音波の往復について、観測時間は以下のようになる。
【００３５】
【数５】

上記に基づき、受信された反射波（受信信号）から、低周波数を有する搬送波の成分を除いた重畳波の成分ｅ_ｐ（ｔ）は、次の（４）式のように表される。なお、図３の（ａ）には、そのｅ_ｐ（ｔ）の波形が示されている。ここで、Ｒ１はピークを示している。
【００３６】
【数６】

但し、ｋは、生体の反射係数である。また、反射時における波形歪み、及び、反射時における音響インピーダンス条件に従った波形の極性反転は考慮していない。
【００３７】
次に、上記と同様に、第２合成波Ｕ_ｎ（ｔ）について、受波された反射波（受信信号）から、低周波数を有する成分を除いた重畳波の成分ｅ_ｎ（ｔ）は、以下のように表される。なお、図３の（ｂ）には、そのｅ_ｎ（ｔ）の波形が示されている。ここで、Ｒ１はピークを示している。
【００３８】
【数７】

上記（４）式を直交検波すると、複素信号
【数８】

が得られる。その実数部は、以下の（６）式にように表される。
【００３９】
【数９】

また、その虚数部は、以下の（７）式のように表される。結局、実数部及び虚数部からなる複素信号は、以下の（８）式のように表される。
【００４０】
【数１０】

上記と同様な方法で、上記（５）式を直交検波すると、複素信号
【数１１】

が得られる。それは以下の（９）式で表される。
【００４１】
【数１２】

よって、両者の複素位相角度は、次の（１０）式で表される。
【００４２】
【数１３】

ここで、
【数１４】

の条件が満たされるので、次の（１１）式が得られる。
【００４３】
【数１５】

上記（１１）式において、位相角θは、距離ｌの関数であるので、各深さでの位相角の変化を求めるには、距離方向に沿って微分演算を行えばよい。非線形効果によるパルスの蓄積変位速度をνで表すと、以下のようになる。
【００４４】
【数１６】

すなわち、各距離での位相角θの微分値はνに比例する。したがって、距離ｌのところでの局所の非線形効果によるパルスの変位速度ν_ｌは、次のように、θの二階微分で表せる。
【００４５】
【数１７】

この変位速度ν_ｌは、組織の音響的な非線形性による音速を表し、生体組織の性状を反映している。この値を知ることにより、組織診断が可能となる。
【００４６】
以上から理解されるように、搬送波に重畳波を重畳させて、その重畳波の時間軸上の位置の変化あるいは位相の変化を観測することにより、搬送波に生じた歪みを計測でき、ひいては、生体組織の性状を診断できる。よって、上記のように２つの合成波を利用し、それらを比較するのが特に望ましいが、いずれかの合成波を利用して、歪みの計測を行うことも可能である。また、２つの合成波の比較方法としては、位相差を求める方法、ピーク位置間の時間差（例えば図３のＲ１間）を計測する方法など各種の手法を採用しうる。
【００４７】
上記の搬送波については、生体組織の非線形効果を十分に受ける周波数に設定する必要がある。例えば、１ＫＨｚ〜１ＭＨｚの範囲内に設定してもよい。重畳波については、搬送波と容易に分離できる周波数に設定するのが望ましく、特に搬送波よりも高い周波数に設定される。例えば、１〜２０ＭＨｚの範囲内に設定してもよい。その波数は、任意に定められるが、そのマーカとしての機能から最適な数値に定めるのが望ましい。
【００４８】
生体組織の非線形効果による超音波の歪みは、その超音波の振幅に大きく依存する。一般に、送波された超音波の二乗に比例する。そこで、搬送波の振幅についてはそれが非生体組織の線形効果を十分に受けるように設定し、一方、重畳波の振幅については、精度よく観測可能で、かつ、生体組織の非線形効果をあまり受けない（事実上無視し得る）程度に設定するのが望ましい。
【００４９】
但し、搬送波が受ける非線特性の効果が非常に大きく、重畳波の１波長（あるいは１／２波長）以上にその重畳波の位置が変位すると、いわゆるエイリアシングにより、正確な変位計測を行えなくなる。そこで、搬送波の振幅を制御し、非線形特性による効果を制御するようにしてもよい。
【００５０】
搬送波上における重畳波の位置は、振幅の頂点又はその付近であるのが望ましい。また、２つの合成波を用いることなく、１つの搬送波に対して、その正振幅部分に第１重畳波を合成し、その負振幅部分について第２重畳波を合成することも可能である。その場合には、第１重畳波及び第２重畳波を弁別できるように、その周波数を変える、互いに異なる符号を与える、などの処理を施すのが望ましい。また、高帯域の超音波振動子を利用し、搬送波と重畳波とを同じ超音波振動子で生成することも可能であるが、帯域の異なる２つの超音波振動子を用いて、音響的に合成波を生成することも可能である。受信時においては、それぞれの超音波振動子からの受信信号が加算され、あるいは別々に処理され、いずれにしても重畳波に相当する成分が抽出される。
【００５１】
図４には、本発明に係る超音波診断装置の好適な実施形態が概念的に示されている。
【００５２】
プローブ１０は、体表面上に当接して用いられ、あるいは体腔内に挿入して用いられる超音波探触子である。プローブ１０は例えば複数の振動素子からなるアレイ振動子を有している。
【００５３】
このアレイ振動子によって超音波ビームが形成され、その超音波ビームは電子走査される。その場合の走査方式としては電子セクタ走査や電子リニア走査などを挙げることができる。
【００５４】
本実施形態においては、上述した合成波の送受信を行うために、上記アレイ振動子として、広帯域を持ったアレイ振動子あるいは二つのアレイ振動子が用いられる。前者のアレイ振動子を用いる場合には、それぞれの素子が少なくとも搬送波及び重畳波の両者をカバーする周波数特性をもっている必要がある。この場合には搬送波と重畳波の合成は電気的になされる。一方、後者の場合、すなわち搬送波と重畳波とで異なるアレイ振動子（超音波振動子）を用いる場合には、それぞれのアレイ振動子は、それに対応する超音波の帯域に対応した周波数特性を有する。この場合においては、一般に、搬送波と重畳波とが音響的に合成され、また搬送波の受波においても、それぞれのアレイ振動子が異なる周波数特性を有することから、それぞれのアレイ振動子においては、対応する周波数の反射波が観測されることになる。それにより得られた各周波数に対応する受信信号は必要に応じて加算される。
【００５５】
送信部１２は、送信ビームフォーマーとして機能する。この送信部１２は周波数ｆ_１の信号を搬送波用信号として生成する送信器１４と、周波数ｆ_２の信号を重畳波用信号として生成する送信器１６とを有している。上記のように、搬送波と重畳波との合成が電気的に行われる場合には、それぞれの信号が電気的に合成され、その合成された信号がプローブ１０へ供給される。もちろん、あらかじめ合成された信号を出力するようにしてもよい。一方、音響的な超音波の合成が行われる場合には、それぞれの信号が対応するアレイ振動子に供給される。
【００５６】
受信部２２は、複数の振動素子から出力される受信信号に対して整相加算処理を実行する受信ビームフォーマーとして機能する。本実施形態においてはその受信部２２がバンドパスフィルタ（ＢＰＦ）２３を有している。このＢＰＦ２３は重畳波に相当する信号成分のみを抽出する回路である。このＢＰＦ２３は、整相加算前の段階において各チャンネルごとに成分抽出を行うものであってもよいし、整相加算後において信号成分の抽出を行うものであってもよい。また、重畳波に相当する信号成分を抽出する代わりに、搬送波の周波数を遮断・除外する回路など設けるようにしてもよい。また後述する直交検波部２４において直交検波条件を調整することにより、上記のＢＰＦ２３と同等の機能を発揮させるようにしてもよい。いずれにしても受信信号中から重畳波に相当する信号成分が抽出されることになる。
【００５７】
制御部１８は送信部１２及び受信部２２の他、装置内における各構成の動作制御を行っている。この制御部１８は特に送受信制御を行っており、定められた送受信シーケンスに従って送信ビームの形成及び受信ビームの形成を行っている。例えば、走査面を構成する各ビーム方位ごとに第１合成波の送受信と第２合成波の送受信とが時分割で実行されるように送受信制御を行っている。もちろん、各ビーム方位ごとに複数回の第１合成波の送受波を行った後、複数回の第２合成波の送受信を行い、それを繰り返すようにしてもよい。
【００５８】
制御部１８は第１合成波が送受信される場合には、送信部１２に対して搬送波の正振幅部分に重畳波が合成されるように制御命令を出し、第２合成波が送受信される場合には搬送波の負振幅部分に重畳波が合成されるように送受信指令を出している。
【００５９】
本実施形態においては制御部１８に対して操作パネル２０が接続されている。操作パネル２０は例えばキーボードやトラックボールなどを有する。その操作パネル２０を利用して、ユーザーは搬送波の振幅及び重畳波の振幅を独立して調整することができ、また搬送波及び重畳波のそれぞれについて独立して周波数を可変することができる。それらの周波数が可変された場合、制御部１８は送信部１２及び受信部２２に対して必要な制御指令を出力する。
【００６０】
直交検波部２４は、整相加算後の受信信号に対して直交検波を実行する。この場合においては、直交検波で用いられる参照信号として重畳波の生成において用いられた送信信号と同一の周波数をもった信号が直交検波部２４に出力されている。直交検波部２０はその信号及びそれを９０度だけ位相をずらした信号を用いて直交検波を実行する。これにより、受信信号は実数部Ｒ及び虚数部Ｉからなる複素信号に変換される。
【００６１】
直交検波部２４においては、第１合成波に対応する第１受信信号と、第２合成波に対応する第２受信信号の両者に対して、時分割で直交検波処理が実行される。最初に現れる第１受信信号は遅延回路部２６に出力され、その複素信号における実数部及び虚数部のそれぞれの信号成分がディレイライン２８，３０に一旦格納される。それぞれのディレイライン２８，３０は、送受信シーケンスに対応した遅延量を有し、具体的には第２受信信号が得られるまで、先に得られた第１受信信号を格納している。したがって、ディレイライン２８，３０は送信パルス繰り返し周期の正数倍の中から上記の条件を満たす遅延時間でのその処理を実行している。
【００６２】
複素乗算器３２は、第１の複素信号及び第２の複素信号の両者間において自己相関演算を実行し、これにより位相差に相当する情報を得る回路である。そのために、この分野において周知の自己相関器を用いることができる。
【００６３】
複素乗算器３２の出力信号は複素信号として与えられ、その複素信号は位相演算器３４に入力される。この位相演算器３４はいわゆる逆正接を演算する回路であり、これによって第１情報としての位相差あるいは速度情報が得られることになる。
【００６４】
位相演算器３４から出力される位相に関する情報は微分演算器３６に入力され、そこで２階微分を実行することにより、第２情報として、各深さごとの非線形特性を表す情報あるいは各深さごとの生体組織の性状を表す情報が取得される。その情報は表示処理部３８に入力される。
【００６５】
表示処理部３８は例えばデジタルスキャンコンバータ（ＤＳＣ）によって構成され、座標変換機能や補間機能などを有している。それが有するフレームメモリ上には上述した生体組織の性状を表す情報がマッピングされる。これによって二次元断層画像が構成され、その二次元断層画像が表示器４０に表示される。
【００６６】
もちろん、本実施形態に係る装置は、三次元画像を形成する場合においても用いることができ、またＭモード画像などを形成する場合にも用いることができる。
【００６７】
いずれにしても、搬送波にマーカとしての重畳波を合成し、そのマーカの時間軸上のシフトをもって搬送波に生じた歪みを高精度に特定可能であるので、生体組織の非線形性を従来よりも高感度に検出することが可能となる。
【００６８】
上記実施形態においては複素乗算を用いて位相差の検出を行ったが、例えばいわゆる折り返し現象などのために正確に位相差が検出できないような場合には、例えば搬送差の振幅を小さくしてその問題に対処するようにしてもよい。また、生体組織によっては搬送波及び重畳波のそれぞれの周波数を適宜異ならせた方が望ましい場合があるため、その場合には操作パネル２０を利用して実際の画像を見ながら最適な周波数の選択を行うようにしてもよい。
【００６９】
また、上記の位相差の検出に代えて、例えば各重畳波についてエンベロープの差を利用し、つまり、そのエンベロープに生じるピークを特定してピーク間の時間差を求めることにより歪み量の計測を行うことも可能である。いずれにしても、図２（ｃ）及び（ｄ）に示したような２つの重畳波の時間差を検知する方法として各種の方法を採用しうる。
【００７０】
上記の生体組織の性状に関する情報は、生体組織の堅さあるいは弾性率を表す情報として用いることもでき、そのような情報を体内から圧力を加えた場合と同等の情報として疾病診断を行うようにしてもよい。
【００７１】
次に、図５及び図６を用いて図４に示したプローブ１０における構成例について説明する。なお、図５及び図６には音響的に２つの超音波の合成を行う場合における概念図が示されている。
【００７２】
図５に示す例では、搬送波を送受信する超音波振動子５０と重畳波を送受信する超音波振動子５２が互いに積層関係で配置されている。すなわち後側にある超音波振動子５０にて発生した超音波はその前側にある超音波振動子５２を伝搬して生体側へ放射される。これと同時に、超音波振動子５２にて生じた超音波も生体側へ放射される。よって、それらにより音響的な合成がなされた超音波が生体内に放射される。なお、図５においてはバッキングや整合層あるいは探触子ケースなどといった部材については図示省略されている。これは図６についても同様である。
【００７３】
図６に示す例では、例えば搬送波を生成する超音波振動子５４に対して重畳波を生成する超音波振動子５６が斜めに対向して配置されている。すなわち超音波振動子５６から放射された超音波は超音波振動子５４の表面上で反射され生体側へ放射される。一方、超音波振動子５４にて発生した超音波はそのまま生体側へ放射される。このように音響的に合成された超音波が生体に放射されることになる。
【００７４】
ちなみに、図５及び図６のいずれの実施形態においても２つの振動子の幾何学的な配置関係が異なることに起因してそれぞれの超音波の位相を調整し、第１合成波及び第２合成波が正確に生成されるようにするのが望ましい。また、図５及び図６に示す実施形態において、各超音波振動子はいわゆるアレイ振動子であってもよい。
【００７５】
また、第１アレイ振動子を構成する複数の振動素子と第２アレイ振動子を構成する複数の振動素子とを互い違いに配置して１つの大きなアレイ振動子を構成してもよい。この場合においては第１アレイ振動子に相当する複数の振動素子によって搬送波が送受波され、第２アレイ振動子を構成する複数の振動素子よって重畳波が送受波されることになる。さらに、第１アレイ振動子と第２アレイ振動子を互いに平行に並べて配置するようにしてもよい。プローブ１０の構成については各種のものを採用でき、いずれにしても第１合成波と第２合成波との送受信を行えるようにする。
【００７６】
【発明の効果】
以上説明したように、本発明によれば、生体組織の性状を計測するための新しい方式を提供できる。また、本発明によれば生体組織の非線形特性を高精度に計測することが可能となる。
【図面の簡単な説明】
【図１】合成波の生成原理を説明するための図である。
【図２】搬送波の歪みと重畳波の発生位置の発生位置のずれを示す図である。
【図３】第１合成波と第２合成波における重畳波の位置の差を説明するための図である。
【図４】本発明に係る超音波診断装置の好適な実施形態を示すブロック図である。
【図５】図４に示すプローブの一例を示す図である。
【図６】図４に示すプローブの他の例を示す図である。
【符号の説明】
１０　プローブ、１２　送信部、１８　制御部、２２　受信部、２４　直交検波部、３２　複素乗算器、３４　位相演算器、３６　微分演算器、３８　表示処理部。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ultrasonic diagnostic apparatus, and more particularly, to an apparatus for measuring a nonlinear characteristic of a living tissue.
[0002]
[Prior art and its problems]
It is known that living tissue has nonlinear characteristics. When an ultrasonic wave propagates through a living tissue, the waveform of the ultrasonic wave is distorted due to its non-linear characteristics. The reflected wave from the living tissue contains the distortion component, and the distortion component can be observed, for example, by extracting the second harmonic in the reflected wave. The harmonic imaging method is a technique for imaging the second harmonic as a tomographic image.
[0003]
However, in a general harmonic imaging method, since the tomographic image is formed by associating the amplitude of the second harmonic in the reflected wave with the luminance, the luminance of the image also depends on the magnitude of the reflected wave. It does not indicate the properties (non-linear characteristics) of itself. In addition, there is a problem that satisfactory sensitivity cannot always be obtained.
[0004]
It is to be noted that a technique is also known in which a reflected wave when an external force is applied to a living tissue is compared with a reflected wave when no external force is applied to the living tissue, thereby detecting displacement of the living tissue. By imaging the displacement, for example, the elastic properties of the living tissue can be displayed. However, this requires a large-scale mechanism for generating an external force.
[0005]
An object of the present invention is to enable a property of a living tissue to be accurately measured.
[0006]
Another object of the present invention is to provide a new measurement method based on non-linear characteristics of a living tissue.
[0007]
[Means for Solving the Problems]
(1) The present invention transmits a synthesized wave obtained by synthesizing a superimposed wave having a high frequency to a carrier having a low frequency to a living body, receives a reflected wave from the living body, and thereby converts a received signal. It is characterized by including transmitting and receiving means for outputting, component extracting means for extracting a superimposed signal component corresponding to the superimposed wave from the received signal, and analyzing means for analyzing the superimposed signal component.
[0008]
According to the above configuration, when the synthesized wave (transmitted ultrasonic wave) is transmitted to the living body, the synthesized wave is distorted by the influence of the nonlinear characteristics of the living tissue. Under desirable conditions, the distortion of a carrier having a low frequency becomes particularly significant. Under the influence of this distortion, the superimposed wave superimposed on the carrier wave is displaced. Since the displacement depends on the non-linear characteristic of the living tissue, measuring the displacement makes it possible to evaluate the non-linear characteristic of the living tissue. That is, the superimposed wave functions as a marker for observing the distortion of the carrier wave.
[0009]
When distortion occurs in the composite wave (particularly, the carrier wave), the distortion of the positive amplitude portion and the distortion of the negative amplitude portion are opposite to each other. Therefore, a first synthetic wave in which the superimposed wave is superimposed on the positive amplitude portion of the carrier and a second synthesized wave in which the superimposed wave is superimposed on the negative amplitude portion of the carrier are used to relatively compare distortions generated in both. You may do so. However, since distortion occurs in both the first synthesized wave and the second synthesized wave, it is also possible to observe the nonlinear characteristics of the living tissue using one of them.
[0010]
The analysis result of the analysis means may be numerically displayed, or may be imaged as a tomographic image. The present invention can be applied to a case where three-dimensional measurement is performed on a living body.
[0011]
Preferably, the analysis unit is configured to determine first information indicating a degree of a waveform distortion generated in the carrier based on a change in the superimposed signal component, and a first information calculation unit configured to determine the first information based on the first information. And second information calculating means for obtaining second information relating to the property of the living tissue. The information on the property of the living tissue may be the nonlinear property itself, or may be information indicating the elastic property of the tissue.
[0012]
Preferably, the first information calculating means obtains the first information based on a change in position of the superimposed signal component on a time axis. Preferably, the second information calculating means obtains the second information for each depth on the ultrasonic beam. Preferably, the amplitude of the carrier wave is larger than the amplitude of the superimposed wave. Preferably, the superimposed wave is synthesized near a local maximum of a positive amplitude portion or a negative amplitude portion of the carrier.
[0013]
(2) The present invention transmits a first synthesized wave, which is obtained by synthesizing a superimposed wave having a high frequency to a positive amplitude part of a carrier having a low frequency, to a living body, and receives a first reflected wave from the living body. And outputs a first reception signal, and transmits a second synthesized wave obtained by synthesizing the superimposed wave to the negative amplitude portion of the carrier wave to a living body, and receives a second reflected wave from the living body. Transmitting and receiving means for outputting a second reception signal, thereby extracting a first superposition signal component corresponding to the superposition wave from the first reception signal, and corresponding to the superposition wave from the second reception signal It is characterized by including a component extracting means for extracting a second superimposed signal component, and an analyzing means for executing an analysis based on the first superimposed signal component and the second superimposed signal component.
[0014]
According to the above configuration, the distortion generated in the carrier can be measured with high accuracy by utilizing the fact that the direction of the distortion in the positive amplitude portion and the direction of the distortion in the negative amplitude portion are different from each other.
[0015]
Preferably, a control means is provided for causing the transmission of the first composite wave and the transmission of the second composite wave to be performed alternately in a time-division manner. For example, a plurality of times of transmitting the first combined wave and a plurality of times of transmitting the second combined wave may be alternately performed, or one transmission of the first combined wave and one second combining may be performed. Wave transmission may be performed alternately. The transmission sequence can be appropriately set according to measurement conditions, purpose, and the like.
[0016]
Preferably, the carrier included in the first carrier and the carrier included in the second carrier have a phase inversion relationship. When performing mutual comparison between two received signals, it is necessary to synchronize. According to the above configuration, the positions where the superimposed waves from the transmission trigger are superimposed can be aligned. It is desirable that the phases of the superposed carriers are the same.
[0017]
Preferably, control means is provided for individually controlling the waveform of the carrier wave and the waveform of the superimposed wave. The control of the waveform includes amplitude control, frequency control, and waveform shape control.
[0018]
Preferably, the analysis unit obtains first information indicating a degree of waveform distortion generated in the carrier based on a difference in a position on the time axis between the first superimposed signal component and the second superimposed signal. An information calculation unit; and a second information calculation unit that obtains second information relating to a property of the living tissue based on the first information.
[0019]
Preferably, the first information calculating means includes a phase difference calculating means for calculating the first information by calculating a phase difference between the first superimposed signal component and the second superimposed signal component. If the phase difference is used, highly accurate distortion observation can be performed.
[0020]
Preferably, the first information calculating means calculates the first information by comparing a detected waveform of the first superimposed signal component with a detected waveform of the second superimposed signal component. including. According to the waveform comparison after the detection, it is possible to cope with the aliasing which becomes a problem when using the phase difference. The concept of detection includes, for example, envelope detection and power calculation.
[0021]
Preferably, the second information calculating means includes a differential calculating means for calculating the second information by differentiating the first information along a depth direction on the ultrasonic beam. The distortion included in the reflected wave is due to the influence of the entire path of the ultrasonic wave (particularly, the transmission ultrasonic wave having a large power), and corresponds to the sum of the effects of the nonlinear characteristics. Therefore, by performing a differential operation, it is possible to obtain a non-linear characteristic at each depth.
[0022]
Preferably, the wave transmitting / receiving means acoustically combines the carrier and the superimposed wave. According to the acoustic synthesis, it is not necessary to use a broadband ultrasonic transducer. Note that a carrier signal and a superimposed wave are electrically combined to generate a combined signal (transmission signal) (or to generate such a combined signal), and the combined signal is supplied to a wideband ultrasonic transducer. You may.
[0023]
Preferably, the wave transmitting / receiving means includes a first ultrasonic vibrator having a frequency band corresponding to the carrier wave, and a second ultrasonic vibrator having a frequency band corresponding to the superimposed wave. Preferably, the first ultrasonic transducer and the second ultrasonic transducer are in a stacked relationship. Preferably, the first ultrasonic vibrator and the second ultrasonic vibrator have an arrangement relationship in which one is opposed to the other.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
First, the principle of the embodiment will be described using mathematical expressions with reference to conceptual diagrams of respective waveforms shown in FIGS.
[0025]
FIG. 1A shows an ultrasonic pulse wave (superimposed wave) f having a high frequency. ₁ The waveform of (t) is shown. This superimposed wave f ₁ (T) is represented by the following equation (1).
[0026]
(Equation 1)

FIG. 1B shows an ultrasonic pulse wave (carrier) f having a low frequency. ₂ The waveform of (t) is shown. This carrier f ₂ (T) is represented by the following equation (2).
[0027]
(Equation 2)

A synthesized wave U (t) obtained by synthesizing the carrier wave and the superimposed wave is transmitted into the living body. FIG. 1C shows the waveform of the composite wave U (t). This composite wave U (t) is represented by the following equation (3).
[0028]
[Equation 3]

In the composite wave U (t), the carrier f ₂ (T) has a large amplitude and is sufficiently affected by the nonlinear characteristics of the propagation medium (living tissue). On the other hand, the superimposed wave f ₁ (T) has a small amplitude and is less affected by the nonlinear characteristics of the propagation medium.
[0029]
Here, with the propagation of the composite wave U (t) in the living tissue, the carrier f ₂ In the positive amplitude part in (t), the sound speed increases, and in the negative amplitude part, the sound speed decreases. That is, the waveform is distorted. At that time, the superimposed wave f ₁ (T) is the carrier f ₂ Under the influence of the waveform distortion of (t), the superimposed wave f ₁ Also for (t), the propagation speed changes as described above.
[0030]
Assuming that the propagation speed of sound in the linear region is c, the sound speed of the negative amplitude portion is v _n Only smaller, c _n = Cv _n It becomes. On the other hand, the sound speed of the above positive amplitude portion is v _p Only faster, c _p = C + v _p It becomes.
[0031]
FIG. 2A shows the first synthesized wave U _p The waveform of (t) is shown, and FIG. _n The waveform of (t) is shown. First synthetic wave U _p (T) is a waveform in which the superimposed wave is synthesized at the (peak) vertex of the positive amplitude portion of the carrier wave. Second synthetic wave U _n (T) is a waveform in which the superimposed wave is synthesized at the (vertical) vertex of the negative amplitude portion of the carrier wave.
[0032]
First, the first synthesized wave U _p Looking at (t), as it travels through the nonlinear medium, the waveform of the carrier is distorted from a sine wave to a triangle wave (approaching an N-shape). At this time, the position of the superimposed wave also moves in the carrier wave distortion direction under the influence of the carrier wave distortion. That is, the propagation speed of the superimposed wave increases, and the observation time of the superimposed wave is shortened on the time axis. FIG. 2C shows the first synthesized wave U _p (T) shows a waveform in which the carrier component is excluded and only the superimposed wave component is represented. FIG. 2D shows the second composite wave U _n (T) shows a waveform in which the carrier component is excluded and only the superimposed wave component is represented.
[0033]
Here, the first synthesized wave U _p For (t), the time t at which it arrives at the reflector located at a distance l from the ultrasonic transducer _pf Is as follows.
[0034]
(Equation 4)

Since the reflected wave reflected at that position has a small amplitude, if the nonlinear effect on the reflected wave can be practically impossible, the observation time for the reciprocation of the ultrasonic wave is as follows.
[0035]
(Equation 5)

Based on the above, a component e of a superimposed wave obtained by removing a component of a carrier having a low frequency from a received reflected wave (received signal) _p (T) is represented by the following equation (4). In addition, FIG. _p The waveform of (t) is shown. Here, R1 indicates a peak.
[0036]
(Equation 6)

Here, k is the reflection coefficient of the living body. Also, the waveform distortion at the time of reflection and the polarity inversion of the waveform according to the acoustic impedance condition at the time of reflection are not considered.
[0037]
Next, similarly to the above, the second synthesized wave U _n Regarding (t), a component e of a superimposed wave excluding a component having a low frequency from the received reflected wave (received signal) _n (T) is expressed as follows. In addition, FIG. _n The waveform of (t) is shown. Here, R1 indicates a peak.
[0038]
(Equation 7)

When the above equation (4) is subjected to quadrature detection, a complex signal
(Equation 8)

Is obtained. The real part is represented by the following equation (6).
[0039]
(Equation 9)

The imaginary part is represented by the following equation (7). After all, a complex signal composed of a real part and an imaginary part is expressed by the following equation (8).
[0040]
(Equation 10)

When the above equation (5) is subjected to quadrature detection in the same manner as above, a complex signal
[Equation 11]

Is obtained. It is expressed by the following equation (9).
[0041]
(Equation 12)

Therefore, the complex phase angle of both is expressed by the following equation (10).
[0042]
(Equation 13)

here,
[Equation 14]

Is satisfied, the following equation (11) is obtained.
[0043]
[Equation 15]

In the above equation (11), the phase angle θ is a function of the distance l. Therefore, in order to obtain a change in the phase angle at each depth, a differential operation may be performed along the distance direction. The accumulated displacement speed of the pulse due to the non-linear effect is represented by ν as follows.
[0044]
(Equation 16)

That is, the differential value of the phase angle θ at each distance is proportional to ν. Therefore, the displacement velocity ν of the pulse due to the local nonlinear effect at the distance l _l Can be expressed by the second derivative of θ as follows.
[0045]
[Equation 17]

This displacement speed ν _l Represents the speed of sound due to the acoustic nonlinearity of the tissue, and reflects the properties of the living tissue. Knowing this value enables tissue diagnosis.
[0046]
As can be understood from the above, by superimposing the superimposed wave on the carrier wave and observing the change in the position or the phase on the time axis of the superimposed wave, it is possible to measure the distortion generated in the carrier wave, and consequently, Diagnosis of tissue characteristics. Therefore, it is particularly desirable to use two synthesized waves and compare them as described above. However, it is also possible to measure distortion using either of the synthesized waves. As a method of comparing the two combined waves, various methods such as a method of obtaining a phase difference and a method of measuring a time difference between peak positions (for example, between R1 in FIG. 3) can be adopted.
[0047]
The carrier needs to be set to a frequency at which the nonlinear effect of the living tissue is sufficiently received. For example, it may be set in the range of 1 KHz to 1 MHz. The superimposed wave is desirably set to a frequency that can be easily separated from the carrier, and particularly set to a frequency higher than the carrier. For example, it may be set within the range of 1 to 20 MHz. Although the wave number is arbitrarily determined, it is desirable to determine the wave number to an optimal value from the function as the marker.
[0048]
Ultrasonic distortion due to the non-linear effect of living tissue greatly depends on the amplitude of the ultrasonic wave. Generally, it is proportional to the square of the transmitted ultrasonic wave. Therefore, the amplitude of the carrier wave is set so as to sufficiently receive the linear effect of the non-living tissue, while the amplitude of the superimposed wave is accurately observable, and is not significantly affected by the non-linear effect of the living tissue. It is desirable to set it to a level that is practically negligible.
[0049]
However, the effect of the non-linear characteristic received by the carrier is very large, and if the position of the superimposed wave is displaced by more than one wavelength (or １ ／ wavelength) of the superimposed wave, accurate displacement measurement cannot be performed due to aliasing. Thus, the amplitude of the carrier may be controlled to control the effect due to the non-linear characteristics.
[0050]
The position of the superimposed wave on the carrier is desirably at or near the peak of the amplitude. Further, it is also possible to combine the first superimposed wave on the positive amplitude part and the second superimposed wave on the negative amplitude part of one carrier wave without using two synthesized waves. In such a case, it is desirable to perform processing such as changing the frequency or giving different codes so that the first superimposed wave and the second superimposed wave can be discriminated. It is also possible to generate a carrier wave and a superimposed wave with the same ultrasonic oscillator using a high-band ultrasonic oscillator, but acoustically using two ultrasonic oscillators having different bands. It is also possible to generate a composite wave. At the time of reception, signals received from the respective ultrasonic transducers are added or processed separately, and in any case, a component corresponding to a superimposed wave is extracted.
[0051]
FIG. 4 conceptually shows a preferred embodiment of the ultrasonic diagnostic apparatus according to the present invention.
[0052]
The probe 10 is an ultrasonic probe used in contact with the body surface or inserted into a body cavity. The probe 10 has, for example, an array vibrator composed of a plurality of vibrating elements.
[0053]
An ultrasonic beam is formed by the array transducer, and the ultrasonic beam is electronically scanned. As the scanning method in that case, an electronic sector scan, an electronic linear scan, or the like can be used.
[0054]
In the present embodiment, an array transducer having a wide band or two array transducers is used as the array transducer in order to transmit and receive the above-described synthesized wave. When the former array vibrator is used, each element needs to have a frequency characteristic covering at least both the carrier wave and the superimposed wave. In this case, the combination of the carrier wave and the superimposed wave is made electrically. On the other hand, in the latter case, that is, when different array transducers (ultrasonic transducers) are used for the carrier wave and the superimposed wave, each array transducer has a frequency characteristic corresponding to the corresponding ultrasonic band. . In this case, in general, the carrier wave and the superimposed wave are acoustically synthesized, and also at the time of receiving the carrier wave, since each array vibrator has a different frequency characteristic, each array vibrator has a corresponding frequency. Thus, a reflected wave of a frequency of the reflected wave is observed. The received signals corresponding to the respective frequencies thus obtained are added as necessary.
[0055]
The transmission unit 12 functions as a transmission beamformer. This transmitting unit 12 has a frequency f ₁ A transmitter 14 for generating the carrier signal as a carrier signal, and a frequency f ₂ And a transmitter 16 for generating the signal of the above as a signal for a superimposed wave. As described above, when the carrier wave and the superimposed wave are electrically combined, the respective signals are electrically combined, and the combined signal is supplied to the probe 10. Of course, a signal synthesized in advance may be output. On the other hand, when acoustic ultrasonic waves are synthesized, each signal is supplied to the corresponding array transducer.
[0056]
The reception unit 22 functions as a reception beamformer that performs a phasing addition process on reception signals output from the plurality of vibration elements. In the present embodiment, the receiving section 22 has a band pass filter (BPF) 23. The BPF 23 is a circuit that extracts only a signal component corresponding to a superimposed wave. The BPF 23 may extract components for each channel at the stage before the phasing addition, or may extract the signal components after the phasing addition. Further, instead of extracting the signal component corresponding to the superimposed wave, a circuit for cutting off or eliminating the frequency of the carrier wave may be provided. In addition, a function equivalent to that of the above-described BPF 23 may be exhibited by adjusting a quadrature detection condition in a quadrature detection unit 24 described later. In any case, a signal component corresponding to the superimposed wave is extracted from the received signal.
[0057]
The control unit 18 controls the operation of each component in the apparatus in addition to the transmission unit 12 and the reception unit 22. The control unit 18 particularly controls transmission and reception, and forms a transmission beam and a reception beam in accordance with a predetermined transmission and reception sequence. For example, transmission / reception control is performed such that transmission / reception of the first composite wave and transmission / reception of the second composite wave are performed in a time-division manner for each beam direction constituting the scanning plane. Of course, after transmitting and receiving the first combined wave a plurality of times for each beam direction, transmission and reception of the second combined wave may be performed a plurality of times, and this may be repeated.
[0058]
When the first synthesized wave is transmitted and received, the control unit 18 issues a control command to the transmitting unit 12 so that the superimposed wave is synthesized with the positive amplitude portion of the carrier wave, and when the second synthesized wave is transmitted and received. , A transmission / reception command is issued so that a superimposed wave is combined with the negative amplitude portion of the carrier wave.
[0059]
In the present embodiment, the operation panel 20 is connected to the control unit 18. The operation panel 20 has, for example, a keyboard and a trackball. Using the operation panel 20, the user can independently adjust the amplitude of the carrier wave and the amplitude of the superimposed wave, and can independently vary the frequency of each of the carrier wave and the superimposed wave. When those frequencies are changed, the control unit 18 outputs necessary control commands to the transmission unit 12 and the reception unit 22.
[0060]
The quadrature detector 24 performs quadrature detection on the received signal after the phasing addition. In this case, a signal having the same frequency as the transmission signal used in the generation of the superimposed wave is output to the quadrature detection unit 24 as a reference signal used in the quadrature detection. The quadrature detection unit 20 performs quadrature detection using the signal and a signal whose phase is shifted by 90 degrees. Thereby, the received signal is converted into a complex signal including the real part R and the imaginary part I.
[0061]
In the quadrature detection unit 24, quadrature detection processing is performed on both the first received signal corresponding to the first combined wave and the second received signal corresponding to the second combined wave by time division. The first received signal that appears first is output to the delay circuit unit 26, and the signal components of the real part and the imaginary part of the complex signal are temporarily stored in the delay lines 28 and 30, respectively. Each of the delay lines 28 and 30 has a delay amount corresponding to the transmission / reception sequence, and specifically stores the first received signal obtained earlier until the second received signal is obtained. Therefore, the delay lines 28 and 30 execute the processing with a delay time that satisfies the above condition from among positive multiples of the transmission pulse repetition period.
[0062]
The complex multiplier 32 is a circuit that performs an autocorrelation operation between both the first complex signal and the second complex signal, thereby obtaining information corresponding to a phase difference. For this purpose, an autocorrelator known in this field can be used.
[0063]
The output signal of the complex multiplier 32 is provided as a complex signal, and the complex signal is input to the phase calculator 34. The phase calculator 34 is a circuit for calculating a so-called arc tangent, whereby the phase difference or the speed information as the first information is obtained.
[0064]
The information on the phase output from the phase calculator 34 is input to the differential calculator 36, where the second-order differentiation is performed, and as the second information, information representing the non-linear characteristic at each depth or each depth. Of the living tissue is obtained. The information is input to the display processing unit 38.
[0065]
The display processing unit 38 is configured by, for example, a digital scan converter (DSC), and has a coordinate conversion function, an interpolation function, and the like. Information indicating the above-mentioned properties of the living tissue is mapped on the frame memory of the memory. Thus, a two-dimensional tomographic image is formed, and the two-dimensional tomographic image is displayed on the display 40.
[0066]
Of course, the device according to the present embodiment can be used also when forming a three-dimensional image, and can also be used when forming an M-mode image or the like.
[0067]
In any case, since the superimposed wave as a marker is synthesized with the carrier wave, and the distortion generated in the carrier wave can be identified with high accuracy by shifting the marker on the time axis, the nonlinearity of the living tissue can be improved more than before. Sensitivity can be detected.
[0068]
In the above embodiment, the phase difference is detected by using complex multiplication.However, when the phase difference cannot be accurately detected due to, for example, a so-called aliasing phenomenon, for example, the amplitude of the transport difference is reduced to reduce the amplitude. Problems may be addressed. Depending on the living tissue, it may be desirable to make the frequencies of the carrier wave and the superimposed wave different from each other as appropriate. In this case, the operator selects an optimal frequency while viewing the actual image using the operation panel 20. It may be performed.
[0069]
Instead of detecting the phase difference, for example, using the difference in envelope for each superimposed wave, that is, measuring the amount of distortion by determining the peak difference occurring in the envelope and determining the time difference between the peaks Is also possible. In any case, various methods can be adopted as a method for detecting the time difference between the two superimposed waves as shown in FIGS. 2C and 2D.
[0070]
The information on the properties of the living tissue described above can be used as information indicating the hardness or elastic modulus of the living tissue, and such information should be used as the same information as when pressure is applied from inside the body to diagnose a disease. You may.
[0071]
Next, a configuration example of the probe 10 shown in FIG. 4 will be described with reference to FIGS. FIGS. 5 and 6 are conceptual diagrams in the case of acoustically combining two ultrasonic waves.
[0072]
In the example shown in FIG. 5, an ultrasonic transducer 50 for transmitting and receiving a carrier wave and an ultrasonic transducer 52 for transmitting and receiving a superimposed wave are arranged in a stacked relationship with each other. That is, the ultrasonic wave generated by the ultrasonic transducer 50 on the rear side propagates through the ultrasonic transducer 52 on the front side and is emitted to the living body side. At the same time, the ultrasonic waves generated by the ultrasonic transducer 52 are also radiated toward the living body. Therefore, the ultrasonic waves synthesized acoustically by them are emitted into the living body. In FIG. 5, members such as a backing, a matching layer, and a probe case are not shown. This is the same for FIG.
[0073]
In the example shown in FIG. 6, for example, an ultrasonic transducer 56 for generating a superimposed wave is disposed obliquely opposite to an ultrasonic transducer 54 for generating a carrier wave. That is, the ultrasonic waves radiated from the ultrasonic transducer 56 are reflected on the surface of the ultrasonic transducer 54 and radiated toward the living body. On the other hand, the ultrasonic waves generated by the ultrasonic transducer 54 are radiated to the living body as it is. Ultrasonic waves thus acoustically synthesized are emitted to the living body.
[0074]
Incidentally, in each of the embodiments shown in FIGS. 5 and 6, the phases of the respective ultrasonic waves are adjusted due to the difference in the geometrical arrangement of the two transducers, and the first synthesized wave and the second synthesized wave are adjusted. It is desirable to ensure that the waves are generated exactly. In the embodiments shown in FIGS. 5 and 6, each ultrasonic transducer may be a so-called array transducer.
[0075]
Further, a plurality of vibrating elements forming the first array vibrator and a plurality of vibrating elements forming the second array vibrator may be alternately arranged to form one large array vibrator. In this case, a carrier wave is transmitted / received by a plurality of vibrating elements corresponding to the first array vibrator, and a superimposed wave is transmitted / received by a plurality of vibrating elements constituting the second array vibrator. Further, the first array transducer and the second array transducer may be arranged in parallel with each other. Various configurations of the probe 10 can be adopted, and in any case, transmission and reception of the first combined wave and the second combined wave can be performed.
[0076]
【The invention's effect】
As described above, according to the present invention, a new method for measuring the properties of a living tissue can be provided. Further, according to the present invention, it is possible to measure the non-linear characteristics of the living tissue with high accuracy.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining a generation principle of a synthetic wave.
FIG. 2 is a diagram illustrating a difference between a carrier wave distortion and a superimposed wave generation position.
FIG. 3 is a diagram for explaining a difference between positions of superimposed waves in a first combined wave and a second combined wave.
FIG. 4 is a block diagram showing a preferred embodiment of the ultrasonic diagnostic apparatus according to the present invention.
FIG. 5 is a diagram showing an example of the probe shown in FIG.
FIG. 6 is a view showing another example of the probe shown in FIG. 4;
[Explanation of symbols]
10 probe, 12 transmitter, 18 controller, 22 receiver, 24 quadrature detector, 32 complex multiplier, 34 phase calculator, 36 differential calculator, 38 display processor.

Claims (18)

A transmitting / receiving means for transmitting a synthesized wave obtained by combining a superimposed wave having a high frequency with a carrier having a low frequency to a living body, receiving a reflected wave from the living body, and thereby outputting a received signal,
Component extraction means for extracting a superimposed signal component corresponding to the superimposed wave from the received signal,
Analysis means for analyzing the superimposed signal component,
An ultrasonic diagnostic apparatus comprising: The device of claim 1,
The analysis means,
First information calculation means for obtaining first information indicating a degree of waveform distortion generated in the carrier based on a change in the superimposed signal component;
Second information calculation means for obtaining second information on the property of the living tissue based on the first information;
An ultrasonic diagnostic apparatus comprising: The device according to claim 2,
The ultrasonic diagnostic apparatus according to claim 1, wherein the first information calculation means obtains the first information based on a change in position of the superimposed signal component on a time axis. The device according to claim 2,
The ultrasonic diagnostic apparatus according to claim 2, wherein the second information calculating means obtains the second information for each depth on an ultrasonic beam. The device of claim 1,
An ultrasonic diagnostic apparatus, wherein the amplitude of the carrier wave is larger than the amplitude of the superimposed wave. The device of claim 1,
An ultrasonic diagnostic apparatus wherein the superimposed wave is synthesized near a local maximum of a positive amplitude portion or a negative amplitude portion of the carrier wave. A first synthesized wave obtained by synthesizing a superimposed wave having a high frequency with a positive amplitude portion of a carrier having a low frequency is transmitted to the living body, and a first reflected wave from the living body is received, thereby receiving the first reflected wave. A received signal is output, and a second synthesized wave obtained by synthesizing the superimposed wave with the negative amplitude portion of the carrier wave is transmitted to a living body, and a second reflected wave from the living body is received. Transmitting and receiving means for outputting a received signal,
Component extraction means for extracting a first superimposed signal component corresponding to the superimposed wave from the first received signal, and extracting a second superimposed signal component corresponding to the superimposed wave from the second received signal;
Analysis means for performing analysis based on the first superimposed signal component and the second superimposed signal component;
An ultrasonic diagnostic apparatus comprising: The device according to claim 7,
An ultrasonic diagnostic apparatus comprising control means for alternately performing transmission of the first combined wave and transmission of the second combined wave in a time-division manner. The device according to claim 7,
An ultrasonic diagnostic apparatus, wherein a carrier included in the first combined wave and a carrier included in the second combined wave have a phase inversion relationship. The device according to claim 7,
An ultrasonic diagnostic apparatus comprising control means for individually controlling the waveform of the carrier wave and the waveform of the superimposed wave. The device according to claim 7,
The analysis means,
First information calculation means for obtaining first information indicating a degree of waveform distortion generated in the carrier based on a difference in a position on the time axis between the first superimposed signal component and the second superimposed signal;
Second information calculation means for obtaining second information on the property of the living tissue based on the first information;
An ultrasonic diagnostic apparatus comprising: The apparatus according to claim 11,
The first information calculating means includes a phase difference calculating means for calculating the first information by calculating a phase difference between the first superimposed signal component and the second superimposed signal component. Ultrasound diagnostic device. The apparatus according to claim 11,
The first information calculating means includes a waveform comparing means for calculating the first information by comparing a detected waveform of the first superimposed signal component with a detected waveform of the second superimposed signal component. An ultrasonic diagnostic apparatus characterized by the above-mentioned. The apparatus according to claim 11,
The ultrasonic diagnostic apparatus according to claim 2, wherein the second information calculating means includes a differential calculating means for calculating the second information by differentiating the first information along a depth direction on an ultrasonic beam. . The device according to claim 7,
The ultrasonic diagnostic apparatus, wherein the transmitting / receiving means acoustically combines the carrier wave and the superimposed wave. The device according to claim 7,
The wave transmitting and receiving means includes a first ultrasonic vibrator having a frequency band corresponding to the carrier wave, and a second ultrasonic vibrator having a frequency band corresponding to the superimposed wave. Ultrasound diagnostic equipment. The apparatus of claim 16,
An ultrasonic diagnostic apparatus, wherein the first ultrasonic transducer and the second ultrasonic transducer are in a stacked relationship. The apparatus according to claim 16,
An ultrasonic diagnostic apparatus, wherein one of the first ultrasonic transducer and the second ultrasonic transducer has an arrangement relationship facing the other.

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