JP2004313291A - Ultrasound diagnostic apparatus, medical image analysis apparatus, and medical image analysis method - Google Patents

Abstract

An ultrasonic diagnostic apparatus, a medical image analyzing apparatus, and a medical image analyzing method that improve measurement accuracy by optimizing a template size when performing pattern patching on medical image data using cross-correlation processing. I do.
An image calculation circuit of an image calculation storage section selects image data of two screens from time-series image data stored in an image data storage circuit, and selects image data of the two screens. Extraction of a plurality of characteristic points that can be easily tracked in the first image data in, and setting of measurement points for measuring physical parameters are performed. Next, a template having a size including a predetermined number or more of the feature points around the measurement point is set, and a cross-correlation process is performed with the second image data using the template. Estimation of physical parameters such as tissue displacement and velocity from.
[Selection diagram] Fig. 1

Description

但し、上記Ｐｘ及びＰｙはテンプレートにおけるＸ方向及びＹ方向の画素数であり、画像Ａ１に設定した計測点ａｘはＰ（Ｐｘ／２，Ｐｙ／２）に設定される。この計算の結果、図７（ｂ）に示すようにｋ＝ｋ１、ｓ＝ｓ１においてγ_１２（ｋ、ｓ）が最大値をもつ場合には計測点ａｘの心筋がＸ方向にｋ１、Ｙ方向にｓ１だけ変位していることを示す。尚、図７（ｂ）ではｋをパラメータにした場合のみを示しているが、ｓをパラメータにした場合についても同様に求めることができる。
【００５８】
次に、画像演算回路２２は、同様の手順によって画像データＡ２と画像データＡ３を読み出す。そして、画像データＡ１に設定した計測点ａｘの画像データＡ２における移動先Ｐ（Ｐｘ／２＋ｋ１、Ｐｙ／２＋ｓ１）を中心としてＸ方向にＰｘ画素、Ｙ方向にＰｙ画素のテンプレートを設定し、このテンプレートと画像データＡ３との間で相互相関処理を行って画像データＡ３における計測点ａｘの変位量を計測する。
【００５９】
更に、同様の手順を繰り返すことによって画像データＡ１において設定した計測点ａｘの画像データＡ３乃至ＡＭにおける移動先、即ち変位量を計測することができる。また、これらの変位量から移動速度（変位の時間に対する１次微分）や移動加速度（変位の時間に対する２次微分）などの物理パラメータを容易に算出することが可能となる（図１０のステップＳ６）。
【００６０】
尚、画像データの時相の更新に伴って画像データが変化し、特徴点の分布状態も変化する。このように時相が変化する画像データに対しても、上記と同様の手順により最適化されたテンプレートサイズによって相互相関処理を行う。即ち、テンプレートサイズの最適化は空間と時間の両領域で行う。
【００６１】
次いで、画像演算回路２２は、上記方法によって得られた計測点ａｘにおける各種物理パラメータの時間的な変化曲線データを画像データ記憶回路２１の第２の記憶領域に保存すると共に、表示部７のモニタ３３において表示する。図８は、このときモニタ３３に表示される超音波画像と各種物理パラメータの変化曲線の１例を示したものであり、例えば、モニタ３３の左領域（図８（ａ））には計測点ａｘの位置情報が重畳された画像データＡ１乃至画像データＡＭが繰り返し表示（ループ表示）され、モニタ３３の右領域（図８（ｂ））には、この計測点ａｘにおける心筋の移動速度（図８（ｂ−１））、変位（図８（ｂ−２））、そして時相を示すＥＣＧ（図８（ｂ−３））が表示され、左領域に表示される画像の時相（Ｔｘ）に同期したマーカが、この各種物理パラメータの変化曲線上に表示される（図１０のステップＳ７）。
【００６２】
以上述べた本実施の形態によれば、指定された観測点の移動変位などの物理パラメータを相互相関処理によって計測する際に、最適な大きさのテンプレートを用いて相互相関処理を行うことができるため、任意の計測点における物理パラメータを高精度で計測することが可能となる。
【００６３】
尚、テンプレートサイズの設定において、このサイズが予め設定されたテンプレートサイズを超えた場合には、物理パラメータの計測を中断し、計測不能である旨を入力部９あるいは表示部７のモニタ３３において表示する。即ち、所望の計測点におけるテンプレートの設定が困難であることを操作者に知らせることによって、操作者は前記計測点の近傍にある第２の計測点を再設定することができるため、常に最適なテンプレートを用いた精度の高い物理パラメータの計測が可能となる。
【００６４】
（変形例）
前記実施の形態では、操作者によって指定された計測点ａｘにおける各種物理パラメータの計測と表示について述べたが、画像データの全ての領域、あるいは操作者が入力部９のマウス等の入力デバイスを用いてマニュアル設定した領域、更には、特開平０８−２５４６０４号公報に記載されているような自動画像輪郭に基づく画像領域などに格子を配置し、複数の格子点を計測点として設定してもよい。
【００６５】
図９は、この変形例における物理パラメータの表示方法の１例を示したものであり、図９（ａ）は、例えば超音波画像データＡｘに設定した格子点（計測点）の各々において得られた移動速度のＸ方向成分であり、図９（ｂ）は同じ計測点において得られた移動速度のＹ方向成分を示す。これらの移動速度成分の大きさはカラーコーディングされ、ユニカラーで表示されるＢモード画像に重畳してカラーで表示される。また、移動速度のＸ方向成分の大きさを明度に変換し、またＹ方向成分の大きさを色彩に変換して１枚のＢモード画像に重畳してカラー表示してもよい。更に、Ｂモード画像データに移動速度などの物理パラメータを重畳した画像データと、図１あるいは図２に示した送受信・画像データ生成部５０のドプラモード処理部５にて生成される組織ドプラモード画像データ、あるいは血流ドプラモード画像データを表示部７のモニタ３３において並べて表示することにより、より多くの心機能情報を得ることが可能となる。
【００６６】
尚、心筋の移動を評価する場合には、上記Ｘ方向及びＹ方向の替わりに、各測定点における心筋の走行方向、及び走行方向と直角な方向に対する夫々の移動速度成分を表示することも有効である。
【００６７】
（第２の実施の形態）
次に、本発明の第２の実施の形態について図１１乃至図１３を用いて説明する。尚、図１３は本実施の形態における画像データ収集と物理パラメータ計測の手順を示すフローチャートである。
【００６８】
この第２の実施の形態の特徴は、超音波画像上に表示される心筋などの診断対象部位の大きさに基づいて、テンプレートサイズの最適化を行うことにある。一般に、臓器の大きさは被検体の体格、あるいは病状によって大きく異なる。このため、例えば肥大した心臓に対して最適化されたテンプレートサイズを通常の大きさの心臓画像データに適用して相互相関処理を行った場合には、運動方向の異なる部位の画像データが同一テンプレート内に含まれる確率が増大し、計測精度の低下を招く。
【００６９】
この第２の本実施の形態における超音波診断装置１００の構成、超音波画像データの生成及び保存については第１の実施の形態と同様であるため（図１３のステップＳ１１）、詳細な説明は省略し、以下では収集された超音波画像データに対する物理パラメータの計測について述べる。
【００７０】
第１の実施の形態と同様な手順によって、画像演算記憶部６の画像データ記憶回路２１に記憶された１心拍分に対応するＭ枚のＢモード画像データを用い、心筋の診断部位における変位や速度などの物理パラメータの計測を行う。操作者は入力部９において、画像データ記憶回路２１に保存されているＢモード画像データの中から１心拍分の画像データＡ１乃至画像データＡＭを選択し、次いで、物理パラメータとして心筋の変位を選択する（図１３のステップＳ１２）。入力部９に入力されたこれらの指示信号は、システム制御部８を介して画像演算回路２２に供給され、画像演算回路２２は、画像データＡ１と画像データＡ２を画像データ記憶回路２１から読み出す。そして、システム制御部８の指示信号に従って画像データＡ１をモニタ３３に表示する。
【００７１】
次いで、操作者はモニタ３３に表示された心臓の超音波画像に対して、例えば弁輪間隔あるいは心尖長軸長などの計測を入力部９のマウスなどの入力デバイスを用いて行う。図１１は、心臓の超音波画像における弁輪間隔及び心尖長軸長の計測方法を示したものであり、弁輪間隔の計測においては、画像上の僧坊弁の起始部である弁輪部ｂ１及びｂ２をマウスを用いて指定することによって、弁輪部ｂ１及びｂ２の位置情報はシステム制御部８を介して画像演算回路２２に供給されて弁輪間隔Ｌ１が計測される。更に、心尖内壁ｂ３を指定することによって弁輪部ｂ１と弁輪部ｂ２を結んだ線分から心尖内壁ｂ３までの距離、即ち心尖長軸長Ｌ２が計測される。また、同様な手順によって心腔の面積や体積、更には心筋壁厚などについても計測される（図１３のステップＳ１３）。
【００７２】
上記計測パラメータの中の１つ、あるいは複数のパラメータを計測することによって、被検体の心臓の大きさや局所的な肥大の状況等が把握でき、測定された臓器の大きさに関わる情報に基づいて画像演算回路２２は画像間の相互相関処理に用いるテンプレートの大きさの最適化を行う。
【００７３】
この画像演算回路２２の記憶回路は、上記計測パラメータの標準値に対する最適なテンプレートサイズが計測部位別に記憶されたテーブルを備えている。図１２（ａ）は計測パラメータ別及び計測部位別に設定されたテンプレートサイズの最適値が記憶されているテーブルを模式的に示したものであり、上記計測部位を図１２（ｂ）に示す。但し、このテーブルに保存されているテンプレートサイズの値は、過去の診断経験の結果から得られる。尚、図１２（ｂ）に示した計測領域の設定は、米国心エコー図学会（ＡＳＥ）の壁運動評価基準に準じているが、この設定方法に限定されるものではなく、更に細分化された計測領域を設定してもよい。
【００７４】
そして、画像演算回路２２は、計測パラメータの実測値と、このテーブルに保存されている標準値とを比較し、比例計算によって最適なテンプレートサイズを計測部位別に算出する。例えば、弁輪間隔がＬ１の心臓の計測部位Ｒ１におけるテンプレートサイズＳ１は、Ｓ１＝Ｓ０・Ｌ１／Ｌ０によって求められる。但し、Ｓ０は弁輪間隔が標準値Ｌ０の場合の計測部位Ｒ１における最適テンプレートサイズである（図１３のステップＳ１４）。
【００７５】
このようにして、各計測部位における最適なテンプレートサイズが算出されたならば、第１の実施の形態と同様な方法によって、画像データＡ１と画像データＡ２，画像データＡ２と画像データＡ３・・・・、画像データＡ（Ｍ−１）と画像データＭにつき、上記の最適なテンプレートサイズを用いて相互相関処理を行い、所望の物理パラメータの計測（図１３のステップＳ１５）と表示（図１３のステップＳ１６）を行う。尚、これらの画像処理方法については第１の実施の形態と同様であるため説明は省略する。
【００７６】
以上述べた第２の実施の形態によれば、過去の経験を生かしてテンプレートサイズの最適化を行うため、第１の実施の形態における特徴点の抽出が不要となり、画像演算に要する時間を短縮することが可能となる。
【００７７】
（第３の実施の形態）
次に、本発明の第３の実施の形態について図１４を用いて説明する。
【００７８】
上記の第１の実施の形態及び第２の実施の形態においては、画像データに基づいて最適なテンプレートサイズを設定し、この最適なテンプレートを用いて所定部位の物理パラメータの計測を行ったが、画像データに含まれるノイズが大きな場合には計測精度が安定しない場合がある。この第３の実施の形態は、このような問題点を解決するためになされるものであり、その特徴は、サイズの異なる複数のテンプレートを使用して物理パラメータを複数回計測し、得られた複数の計測値の中から再現性の良いデータを抽出して物理パラメータの値を決定することにある。
【００７９】
この第３の実施の形態における超音波診断装置１００の構成、超音波画像データの生成及び保存についても第１の実施の形態と同様であるため、詳細な説明は省略し、収集された超音波画像データに対する物理パラメータの計測方法について述べる。
【００８０】
第１の実施の形態と同様な手順によって、画像演算記憶部６の画像データ記憶回路２１に保存された１心拍分に対応するＭ枚のＢモード画像データを用い、心筋の診断部位における変位や移動速度などの物理パラメータの計測を行う。操作者は、入力部９において、画像データ記憶回路２１に保存されているＢモード画像データの中から１心拍分の画像データＡ１乃至画像データＡＭを選択し、次いで、計測する物理パラメータ（例えば心筋の変位）と計測点ａｘを選択することによってシステム制御部８は、画像データＡ１と画像データＡ２を用い、画像データＡ１の計測点ａｘにおける上記物理パラメータの計測モードに切り換える。
【００８１】
そして、図１の画像演算記憶部６の画像演算回路２２は、例えば第１の実施の形態、あるいは第２の実施の形態と同様な方法によって、計測点ａｘに最適なテンプレートサイズを設定し、更に、この最適テンプレートサイズを中心にサイズの異なるＮｘ種類のテンプレートサイズ（テンプレートサイズＴＲ−１乃至ＴＲ−Ｎｘ）を設定する。このようにして、Ｎｘ種類のテンプレートサイズを設定したならば、画像データＡ１と画像データＡ２に対して上記のＮｘ種類のテンプレートサイズを適用し、第１の実施と同様な手順によって、相互相関処理を順次行い、更に、この相互相関処理の結果から心筋の変位Ｑ−１乃至Ｑ−Ｎｘを求める。
【００８２】
図１４はこのようにして得られたＮｘヶの変位量Ｑ−１乃至Ｑ−Ｎｘの分布（ヒストグラム）であり、横軸は量子化された物理パラメータの値、即ち変位の大きさを示し、縦軸はこの量子化された変位量が発生する頻度を示す。画像演算記憶部６の画像演算回路２２はこのようなヒストグラムを作成し、更に、このヒストグラムにおいて特異なデータＣａ、Ｃｂを除去した後、ヒストグラムの中心値Ｑｘを求めて計測点ａｘにおける物理パラメータ（変位）の値に設定する。同様にして、画像データＡ２と画像データＡ３・・・・、画像データＡ（Ｍ−１）と画像データＭについても、夫々Ｎｘ種類のテンプレートサイズを用いてＮｘの変位の値を求め、そのヒストグラムの中心値から最終的な変位を設定する。
【００８３】
次いで、画像演算回路２２は設定された最適なテンプレートを用いて相互相関処理を行う。また、画像データ上に複数個の計測点を設定した場合においても、夫々の計測点について上記の手順をくりかえすことによって、その計測点における物理パラメータを精度良く求めることができる。
【００８４】
以上述べた本実施の形態によれば、ヒストグラムの中心値を物理パラメータの値に設定することによって、等価的に最適なテンプレートサイズによって物理パラメータの計測を行ったことになり、この方法は統計的な手法を導入しているため、Ｓ／Ｎが劣化した画像データであっても精度の良い物理パラメータ計測が可能となる。
【００８５】
尚、本発明における物理パラメータの計測は、超音波診断装置１００の送受信・画像データ生成部５０や超音波プローブ１と分離して構成することができる。即ち、図１５に示すように入力部９、画像演算記憶部６、システム制御部８、表示部７とを備える医用画像処理装置５１として独立して構成することが可能である。この場合画像演算記憶部６の画像データ記憶回路２１に保存される複数枚の超音波画像データは別途構成される超音波診断装置やＸ線ＣＴ装置、あるいはＭＲＩ装置などの画像診断装置から、記憶媒体あるいは通信ケーブルを介して供給され、画像演算回路２２は、これらの画像診断装置によって得られた画像データに対して同様な物理パラメータの計測を行うことが可能である。
【００８６】
以上、本発明の実施の形態について述べてきたが、本発明は上記の実施の形態に限定されるものでは無く、変形して実施することが可能である。例えば、物理パラメータの計測におけるパターマッチング法として相互相関処理について説明したが、他の方法であってもよい。また、心臓の超音波画像データにおける物理パラメータの計測について述べたが、本発明は他の医用画像データに対して適用することも可能である。
【００８７】
更に、計測パラメータとして弁輪間隔、心尖長軸長、面積、体積、心臓壁厚、また、物理パラメータとして心筋の変位、移動速度、移動加速度、歪について説明したが、これらに限定されない。また、診断対象臓器として心臓について述べたが他の臓器においても有効であることは言うまでもない。
【００８８】
【発明の効果】
本発明によれば、画像データ間の相関処理におけるテンプレートの大きさを画像データに基づいて最適化できるため、診断を短時間で、しかも常に精度よく行うことができる。
【図面の簡単な説明】
【図１】本発明の第１の実施の形態における超音波診断装置全体の構成を示す図。
【図２】同実施の形態における送受信・画像データ生成部の構成を示す図。
【図３】同実施の形態における画像上の格子と計測点を示す図。
【図４】同実施の形態におけるテンプレートサイズと相関処理の精度を示す図。
【図５】同実施の形態におけるコーナー検出法を模式的に示す図。
【図６】同実施の形態における画像上の特徴点を示す図。
【図７】同実施の形態における画像間の相互相関処理を示す図。
【図８】同実施の形態における超音波画像と各種物理パラメータの表示方法を示す図。
【図９】同実施の形態における超音波画像と各種物理パラメータの他の表示方法を示す図。
【図１０】同実施の形態における画像データ収集と物理パラメータ計測の手順を示すフローチャート。
【図１１】本発明の第２の実施の形態における心筋の弁輪間隔及び心尖長軸長の計測方法を示す図。
【図１２】同実施の形態におけるテンプレートサイズの最適値が記憶されているテーブルの模式図。
【図１３】同実施の形態における画像データ収集と物理パラメータ計測の手順を示すフローチャート。
【図１４】本発明の第３の実施の形態における物理パラメータ計測値のヒストグラム。
【図１５】本発明の医用画像処理装置の具体例を示す図。
【符号の説明】
１…超音波プローブ
２…送信部
３…受信部
４…Ｂモード処理部
５…ドプラモード処理部
６…画像演算記憶部
７…表示部
８…システム制御部
９…入力部
１０…生体信号計測部
２１…画像データ記憶回路
２２…画像演算回路
３１…表示用画像メモリ
３２…変換回路
５０…送受信・画像データ生成部
１００…超音波診断装置[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ultrasonic diagnostic apparatus, a medical image analyzing apparatus, and a medical image analyzing method capable of performing useful clinical diagnosis by estimating local function information of a living tissue from medical image data.
[0002]
[Prior art]
An ultrasonic diagnostic apparatus emits ultrasonic waves generated from an ultrasonic transducer built in an ultrasonic probe into a subject, and receives a reflected signal generated by a difference in acoustic impedance of a subject tissue by the ultrasonic transducer. It is displayed on the monitor.
[0003]
This diagnostic method is widely used for functional diagnosis and morphological diagnosis of an organ such as a heart, because a real-time two-dimensional image can be easily observed by a simple operation of merely bringing an ultrasonic probe into contact with a body surface.
[0004]
Particularly in the ultrasonic diagnosis of tissues such as the heart, it is extremely important to evaluate the function objectively and quantitatively, and the test items include the motor function of heart tissue (systolic capacity and diastolic capacity) and blood There are velocity and turbulence of the flow, area and volume in the heart chamber, and the like. In the past, doctors manually set measurement sites on M-mode images, but in recent years, by applying pattern matching to ultrasonic image data, quantitative measurements such as cardiac function have been made. In a short time.
[0005]
In this pattern matching method, for example, a two-dimensional correlation processing region (hereinafter, referred to as a region of interest) is set in first image data of ultrasonic image data for two screens (hereinafter, simply referred to as two). A cross-correlation coefficient is calculated while moving the image data (hereinafter, referred to as a template) in the region of interest with respect to the second ultrasonic image data in a predetermined direction by a predetermined distance. The displacement of the myocardium, the moving speed and the moving acceleration of the myocardium are estimated from the moving position (see, for example, Patent Document 1).
[0006]
Examples of the measurement quantities useful for the analysis of the cardiac function include a movement vector, a movement trajectory, and a cross-correlation value in a local part of the myocardium.Based on these measurement amounts, the displacement, the movement speed, the movement acceleration, and the Analysis of the strain and the like is performed to evaluate the heart function. The displacement and strain of the myocardium and the moving speed at the time of contraction or dilation reflect the heart function itself, and the moving acceleration is used as a clue to know the start timing of contraction or dilation of the myocardium.
[0007]
[Patent Document 1]
JP-A-2002-140690 (Pages 5-6, FIG. 1-6)
[0008]
[Problems to be solved by the invention]
Since the measurement accuracy in the pattern matching method to which the above-described cross-correlation processing is applied depends on the size of the template, it is preferable to set the measurement accuracy to the optimal size of the template. In other words, for image data of an organ that is moving uniformly, the larger the template size, the higher the measurement accuracy in the cross-correlation process. When a large template is set, the image data of the organs having different movement directions are mixed on the same template, so that the measurement accuracy may be reduced. Therefore, optimization of the template size is required.
[0009]
However, since the template size in the pattern matching method using the conventional cross-correlation processing is always fixed regardless of the diagnosis site, sufficient measurement accuracy may not be obtained in some cases.
[0010]
An object of the present invention has been made in view of the above problems, and an object of the present invention is to improve the accuracy of cross-correlation processing in pattern matching by optimizing the size of a template, and to perform measurement in a short time. Another object of the present invention is to provide an ultrasonic diagnostic apparatus, a medical image analyzing apparatus, and a medical image analyzing method that can be performed with high accuracy.
[0011]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, an ultrasonic diagnostic apparatus according to the present invention according to claim 1 includes an ultrasonic probe including an ultrasonic vibrator for transmitting and receiving ultrasonic waves to and from a subject; Transmitting / receiving means for transmitting / receiving data to / from the child, image data generating means for generating ultrasonic image data from a received signal obtained by the transmitting / receiving means, and ultrasonic image data for a plurality of screens generated by the image data generating means Image data storage means for storing ultrasonic image data for at least two screens from among the ultrasonic image data for a plurality of screens stored in the image data storage means; A feature point extracting means for extracting a feature point from the first image data of the image data for at least two screens, and a feature point extracted by the feature point extracting means. Template size setting means for setting the size of the template at one or more measurement points of the first image data based on points; and using the template of the size set by the template size setting means to select the image data. Image calculation means for performing an inter-image operation with the second image data selected by the means, physical parameter measurement means for measuring a physical parameter at the measurement point based on a result of the inter-image operation, Display means for displaying the measurement result of the physical parameter.
[0012]
In the medical image analyzing apparatus of the present invention according to claim 13, an image data storing means for storing medical image data for a plurality of screens generated by the medical image diagnostic apparatus, and a plurality of image data stored in the image data storing means. Image data selecting means for selecting at least two screens of medical image data from among the screens of medical image data; and a feature point for the selected first image data of the at least two screens of image data. A template size setting unit configured to set a template size at one or a plurality of measurement points of the first image data based on the feature points extracted by the feature point extraction unit; Using the template of the size set by the template size setting means, the template selected by the image data selecting means Image operation means for performing an inter-image operation with the second image data, physical parameter measurement means for measuring a physical parameter at the measurement point based on a result of the inter-image operation, and a measurement result of the physical parameter. Display means for displaying.
[0013]
The medical image analysis method of the present invention according to claim 16, further comprising: selecting medical image data for at least two screens from the stored medical image data for a plurality of screens; Extracting feature points from the first image data of the minute image data; and determining a size of the template at one or more measurement points of the first image data based on the extracted feature points. Setting, performing an inter-image operation with the second image data using the template of the set size, and measuring physical parameters at the measurement points based on the result of the inter-image operation And a step of displaying a measurement result of the physical parameter.
[0014]
Therefore, according to the present invention, the size of the template in the correlation process between the image data can be optimized based on the image data, so that the diagnosis can be performed in a short time and with high accuracy.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
(First Embodiment)
Hereinafter, a first embodiment in which the present invention is applied to ultrasonic image data of the heart obtained by the sector scanning method will be described with reference to FIGS. FIG. 1 is a block diagram showing an overall configuration of an ultrasonic diagnostic apparatus according to the present embodiment, and FIG. 2 is a block diagram of a transmission / reception / image data generation unit constituting the ultrasonic diagnostic apparatus.
[0016]
An ultrasonic diagnostic apparatus 100 shown in FIG. 1 transmits and receives an ultrasonic signal to and from an object, and transmits and receives an electric signal to and from the ultrasonic probe 1. A transmission / reception / image data generation unit 50 for generating ultrasonic image data from the apparatus, and a plurality of ultrasonic image data obtained by the transmission / reception / image data generation unit 50 are sequentially stored, and the stored ultrasonic image is An image calculation storage unit 6 for performing image calculation by using a computer, a biological signal measurement unit 10 for measuring a biological signal such as an ECG (electrocardiographic waveform) of a subject, a system control unit 8 for controlling these units in a unified manner, A display unit 7 and an input unit 9 are provided.
[0017]
The ultrasonic probe 1 transmits and receives ultrasonic waves by bringing its front surface into contact with the surface of the subject, and has a plurality of minute ultrasonic transducers arranged one-dimensionally at its distal end. ing. This ultrasonic transducer is an electroacoustic transducer, which converts an electric pulse into an ultrasonic pulse (transmitted ultrasonic wave) during transmission, and converts an ultrasonic reflected signal (received ultrasonic signal) into an electric signal during reception. have. The center frequency of an ultrasonic pulse that greatly affects the resolution and sensitivity of an ultrasonic image is substantially determined by the thickness of the ultrasonic transducer. The ultrasonic probe 1 is configured to be small and lightweight, and is connected to the transmission unit 2 and the reception unit 3 of the transmission / reception / image data generation unit 50 via a cable. The ultrasonic probe 1 has a sector scan correspondence, a linear scan correspondence, a convex scan correspondence, and the like. The probe is arbitrarily selected from these probes according to a diagnosis site. The case where the ultrasonic probe 1 of the above is used will be described.
[0018]
The transmission / reception / image data generation unit 50 illustrated in FIG. 2 includes a transmission unit 2 that generates a drive signal for generating a transmission ultrasonic wave from the ultrasonic probe 1 and a reception unit that receives a reception ultrasonic signal from inside the subject. 3, a B-mode processing unit 4 that performs signal processing for generating B-mode image data on the received ultrasonic signal, and color Doppler image (blood Doppler image) data or tissue on the received ultrasonic signal. A Doppler mode processing unit 5 that performs signal processing for Doppler image data generation is provided.
[0019]
The transmission unit 2 includes a rate pulse generator 41, a transmission delay circuit 42, and a pulser 43. The rate pulse generator 41 generates a rate pulse that determines the repetition period of the ultrasonic pulse radiated into the subject, and the transmission delay circuit 42 sets the convergence distance and deflection angle of the ultrasonic beam during transmission. And sets the timing for driving a plurality of ultrasonic transducers. The pulser 43 is a drive circuit that generates a high-voltage pulse for driving the ultrasonic transducer.
[0020]
The rate pulse generator 41 supplies a rate pulse for determining a repetition period of the ultrasonic pulse radiated into the subject to the transmission delay circuit 42. The transmission delay circuit 42 is composed of a plurality of independent delay circuits as many as the number of ultrasonic transducers used for transmission, and is used to converge the ultrasonic wave to a predetermined depth in order to obtain a narrow beam width in transmission. A delay time and a delay time for transmitting an ultrasonic wave in a predetermined direction are given to the rate pulse and supplied to the pulser 43.
[0021]
The pulsar 43 has the same number of independent driving circuits as the number of ultrasonic transducers used for transmission, similarly to the transmission delay circuit 42, and drives the ultrasonic transducers incorporated in the ultrasonic probe 1, A drive pulse for emitting a transmission ultrasonic wave to the subject is formed.
[0022]
The receiving unit 3 includes a preamplifier 44, a reception delay circuit 45, and an adder 46. The preamplifier 44 amplifies a small signal converted into an electric signal by the ultrasonic transducer and secures a sufficient S / N. The reception delay circuit 45 scans the subject by sequentially deflecting the ultrasonic beam in a predetermined direction and a convergence delay time for converging a received ultrasonic signal from a predetermined depth to obtain a narrow reception beam width. After giving a delay time to the output of the preamplifier 44 to the adder 46, the adder 46 adds a plurality of received signals from the ultrasonic transducers and combines them into one.
[0023]
The B-mode processing unit 4 includes a logarithmic converter 47, an envelope detector 48, and an A / D converter 49. The input signal of the B-mode processing unit 4 has a function of logarithmically converting the amplitude of the received signal by a logarithmic converter 47 to relatively emphasize a weak signal. Generally, a received signal from the subject has an amplitude having a wide dynamic range of 80 dB or more, and in order to display this on a normal television monitor having a dynamic range of about 20 to 30 dB, a weak signal is emphasized. Required amplitude compression. The envelope detector 48 performs envelope detection on the log-converted received signal, removes ultrasonic frequency components, and detects only the amplitude. The A / D converter 49 A / D converts the output signal of the envelope detector 48 to generate B-mode image data.
[0024]
On the other hand, the Doppler mode processing unit 5 includes a reference signal generator 51, a π / 2 phase shifter 52, mixers 53-1 and 53-2, LPFs (low-pass filters) 54-1 and 54-2, an A / D converter. 55-1 and 55-2, a Doppler signal storage circuit 56, an FFT analyzer 57, and a calculator 58 are provided, and mainly perform quadrature phase detection and FFT analysis.
[0025]
That is, the input signal of the Doppler mode processing unit 5 is input to the first input terminals of the mixers 53-1 and 53-2. On the other hand, the output of the reference signal generator 51 having a frequency substantially equal to the center frequency of this input signal is directly sent to the second input terminal of the mixer 53-1 and is sent to the 90 ° via the π / 2 phase shifter 52. The phase-shifted output is sent to the second input terminal of mixer 53-2. The outputs of the mixers 53-1 and 53-2 are sent to LPFs 54-1 and 54-2, and are the components of the sum of the frequency of the input signal of the Doppler mode processing unit 5 and the signal frequency from the reference signal generator 51. Is removed, and only the difference component is extracted.
[0026]
The A / D converters 55-1 and 55-2 convert the outputs of the LPFs 54-1 and 54-2, that is, the quadrature phase detection outputs into digital signals, and the FFT analyzer 57 converts the digitized quadrature components into Doppler signals once. After storing in the storage circuit 56, FFT analysis is performed. On the other hand, the arithmetic unit 58 calculates the center frequency and the spread (variance) of the frequency spectrum of the Doppler signal obtained by the FFT analyzer 57.
[0027]
Returning to FIG. 1, the image calculation storage unit 6 includes an image data storage circuit 21 for storing the image data generated by the transmission / reception and image data generation unit 50, and an inter-image calculation such as a cross-correlation process on the image data. And an image operation circuit 22 for performing the above. The image operation circuit 22 has a high-speed operation unit and a storage circuit (not shown), and reads out desired image data from a plurality of image data stored in the image data storage circuit 21. Extraction, setting the calculation area (template size) of the cross-correlation processing based on the number of feature points, and performing inter-image calculations such as cross-correlation processing between images. Find the physical parameters of For example, physical parameters such as myocardial displacement, moving speed, moving acceleration, and strain are measured by cross-correlation processing using ultrasonic image data of the heart. Further, data relating to a graph or a distribution chart is formed based on the measurement results of the physical parameters.
[0028]
On the other hand, the image data storage circuit 21 stores the B-mode image data generated by the B-mode processing unit 4 of the transmission / reception / image data generation unit 50 and the Doppler mode image data generated by the Doppler mode processing unit 5. And a second storage area for storing measurement results of various physical parameters measured by the image operation circuit 22 in correspondence with the image data.
[0029]
The system control unit 8 controls each unit such as the transmission / reception / image data generation unit 50, the image calculation storage unit 6, the input unit 9, and the display unit 7 based on the instruction signal from the input unit 9, and controls the entire system. And supervise.
[0030]
The input unit 9 includes input devices such as a display panel, a keyboard, a trackball, and a mouse on an operation panel, and includes patient information, an image data collection mode, measurement parameters, physical parameters, a maximum template size, and an image used for image calculation. It is used for inputting an instruction signal necessary for collecting image data and calculating between images, such as a time phase and a grid interval. Measurement parameters in an ultrasonic image of the heart include annulus spacing, apical long axis length, area, volume, and heart wall thickness, and physical parameters such as myocardial displacement, moving speed, moving acceleration, and strain. There is.
[0031]
The display unit 7 includes a display image memory 31, a conversion circuit 32, and a monitor 33. The display unit 7 uses the ultrasonic image data stored in the image data storage circuit 21 of the image calculation storage unit 6 and uses the ultrasonic image data. The additional information such as a graph and a distribution chart relating to various physical parameters obtained by the inter-image calculation is synthesized in the display image memory 31, and further subjected to D / A conversion and television format conversion in the conversion circuit 32. , CRT, or liquid crystal.
[0032]
The biological signal measurement unit 10 has a sensor function of detecting an ECG signal by being attached to the body surface of a subject, and a function of converting an ECG signal detected by the sensor function into a digital signal. The ECG signal obtained at the same time as the two-dimensional image data is stored in the image data storage circuit 21 of the image calculation storage unit 6 as supplementary information of the plurality of pieces of ultrasonic image data, and the monitor 33 of the display unit 7 corresponds to the physical parameters. Is displayed in.
[0033]
Next, a procedure for collecting two-dimensional image data according to the first embodiment of the present invention will be described with reference to FIGS. 1, 2, and 10. FIG. 10 is a flowchart showing a procedure of image data collection and physical parameter measurement in the present embodiment.
[0034]
Prior to the image data collection, the operator sets the ultrasonic scanning method, the ultrasonic probe 1 to be used, and the image data acquisition mode using the input unit 9. The data is sent to and stored in a memory (not shown). In the present embodiment, a sector scan is performed on the heart of the subject, and B-mode image data and tissue Doppler mode image data are collected (step S1 in FIG. 10).
[0035]
When the above-mentioned initialization is completed, the operator fixes the tip (ultrasonic transmitting / receiving surface) of the ultrasonic probe 1 at a predetermined position on the body surface of the subject, and acquires the ultrasonic image data in the time phase T1. To start. When transmitting the ultrasonic wave, the rate pulse generator 41 in FIG. 2 synchronizes with the control signal from the system control unit 8 and sends a rate pulse for determining the repetition period of the ultrasonic pulse radiated into the subject to the transmission delay circuit 42. Supply.
[0036]
The transmission delay circuit 42 is provided with approximately the same number of independent delay circuits as the ultrasonic transducers used for transmission, and a delay time for converging the ultrasonic wave to a predetermined depth in order to obtain a narrow beam width in transmission, A delay time for transmitting an ultrasonic wave in a predetermined direction (θ1) is given to the rate pulse, and the rate pulse is supplied to the pulser 43.
[0037]
The pulsar 43 has substantially the same number of independent driving circuits as the number of ultrasonic transducers used for transmission in the same manner as the transmission delay circuit 42. The ultrasonic transducer incorporated in the ultrasonic probe 1 is driven to emit an ultrasonic pulse into the subject.
[0038]
A part of the ultrasonic wave radiated into the subject is reflected on a boundary surface or a tissue between organs in the subject having different acoustic impedances. When this ultrasonic wave is reflected by a moving reflector such as a heart wall or a blood cell, the ultrasonic frequency undergoes a Doppler shift. Ultrasonic waves (received ultrasonic signals) reflected by the subject tissue are received by the same ultrasonic transducer as at the time of transmission and are converted into electric signals. This received signal is amplified by approximately the same number of independent preamplifiers 44 as the number of ultrasonic transducers used for reception, and sent to the same number of reception delay circuits 45 as the number of ultrasonic transducers used for reception.
[0039]
The reception delay circuit 45 provides a delay time for converging an ultrasonic wave from a predetermined depth to obtain a narrow beam width in reception, and a strong reception directivity in a predetermined direction (θ1) with respect to the ultrasonic beam. After giving the received signal a delay time for receiving the signal, the signal is sent to the adder 46. The adder 46 adds and combines a plurality of reception signals input via the preamplifier 44 and the reception delay circuit 45, combines them into one reception signal, and sends it to the B-mode processing unit 4 and the Doppler mode processing unit 5.
[0040]
Next, when a B-mode image is collected, the output of the adder 46 is sent to the B-mode processing unit 4 and subjected to logarithmic conversion, envelope detection, and A / D conversion. The image data is stored in the image data storage circuit 21 of the unit 6.
[0041]
On the other hand, in order to obtain the Doppler shift of the ultrasonic reception signal in the Doppler mode processing unit 5, the system control unit 8 continuously transmits and receives the ultrasonic wave a plurality of times in the same direction (θ1). Is subjected to FFT (Fast-Fourier-Transform) analysis. That is, the Doppler mode processing unit 5 performs quadrature phase detection on the output of the adder 46 using the mixers 53-1 and 53-2 and the LPFs 54-1 and 54-2, converts the output into a complex signal, and performs A / D conversion. After conversion into digital signals by the devices 55-1 and 55-2, the signals are stored in the Doppler signal storage circuit 56. A similar process is performed on a reception signal obtained by performing multiple scans in the same transmission / reception direction (θ1), and the FFT analyzer 57 obtains a frequency spectrum for a plurality of reception signal data stored in the Doppler signal storage circuit 56. .
[0042]
Next, the calculator 58 calculates the center (average velocity of tissue or blood flow) of the frequency spectrum output from the FFT analyzer 57, and the system controller 8 uses the calculation result as Doppler mode image data. The image data is stored in the image data storage circuit 21 of the image calculation storage unit 6 in FIG. 1 together with the B-mode image data.
[0043]
However, the frequency spectrum of the Doppler signal obtained by the FFT analyzer 57 includes a tissue Doppler component generated by movement of a tissue such as a myocardium and a blood flow Doppler component generated by a blood flow, and the former is composed of a lower frequency component than the latter. Have been. Therefore, in order to measure the tissue velocity of the myocardium as in the present embodiment, an optimal filtering constant for extracting a Doppler signal component (hereinafter referred to as a tissue Doppler component) reflecting the tissue velocity is set.
[0044]
In calculating the tissue Doppler component of the ultrasonic reception signal, an MTI filter and an autocorrelation function are used instead of the method using the FFT analysis as described above, and the center of the Doppler component spectrum (that is, the average velocity), the power, or the like. The variance value may be obtained.
[0045]
Next, the transmission / reception direction of the ultrasonic wave is changed to θ1 + (N−1) Δθ while sequentially updating the transmission / reception direction of the ultrasonic wave by Δθ, and the transmission / reception of the ultrasonic wave is performed in the same procedure as above by scanning in the N direction, and the inside of the subject is scanned in real time. I do. At this time, the system control unit 8 sequentially switches the delay times of the transmission delay circuit 42 and the reception delay circuit 45 of the transmission / reception / image data generation unit 50 in accordance with the ultrasonic transmission / reception direction according to the control signal. Each of the mode image data and the Doppler mode image data is collected.
[0046]
Further, the system control unit 8 converts the B-mode image data and the Doppler mode image data at θ1 + Δθ to θ1 + (N−1) Δθ into a two-dimensional image at the time phase T1 in the same manner as the already obtained θ1 direction image data. The data is sequentially stored in the image data storage circuit 21 of the image operation storage unit 6 and displayed on the monitor 33 of the display unit 7.
[0047]
Next, in the time phase T2 to the time phase TM, the B-mode image data and the Doppler mode image data are collected in exactly the same procedure as described above, and stored in the image data storage circuit 21. These image data are displayed on the monitor 33 of the display unit 7 in real time. Here, for convenience, the above-mentioned M pieces of image data are obtained during one heartbeat period, but a plurality of pieces of image data obtained in real time during one or more heartbeat periods are usually stored in the image data storage circuit 21. Electrocardiographic waveform information stored and supplied from the biological signal measuring unit 10 via the system control unit 8 is added to each image data as supplementary information (step S2 in FIG. 10).
[0048]
Next, a procedure for measuring physical parameters according to the first embodiment will be described with reference to FIGS.
[0049]
That is, the image calculation circuit 22 of the image calculation storage unit 6 selects and uses the B-mode image data for one heartbeat (M frames) stored in the image data storage circuit 21 and uses the B-mode image data for the displacement and the movement speed at the diagnosis site of the myocardium. Measure physical parameters such as In this case, feature points related to the accuracy of the correlation processing are defined in the B-mode image data of the diagnosis site, and the size of the template used for the cross-correlation processing is optimized based on the number and distribution of the feature points. Then, various physical parameters are measured from the cross-correlation processing between the images using the optimized template, and displayed on the monitor 33 of the display unit 7 together with the B-mode image data.
[0050]
Hereinafter, the measurement procedure will be described in more detail. The operator uses the input unit 9 to select one heartbeat of the heart (for example, the time phase T1 collected at the R-R interval of the electrocardiographic waveform) from the B-mode image data stored in the image data storage circuit 21. To time phase TM) of M image data A1 to AM. Specifically, the first image A1 and the last image AM in one heartbeat period are displayed while displaying the B-mode image data and the electrocardiographic waveform information stored in the image data storage circuit 21 on the monitor 33 of the display unit 7. Specify (Step S3 in FIG. 10).
[0051]
Next, by selecting the displacement of the myocardium as a physical parameter, the system control unit 8 starts measuring the displacement of the myocardium at the diagnostic site (measurement point) of the image data A1 using the image data A1 and the image data A2. At this time, the image calculation circuit 22 of the image calculation storage unit 6 displays the image data A1 on the monitor 33 according to the instruction signal of the system control unit 8, and furthermore, displays a grid of a predetermined interval (Δg) on this image. Deploy. FIG. 3 is a B-mode image of a heart on which a grid is arranged, and the grid interval Δg is usually preferably 2 mm to 3 mm. Then, the operator designates a measurement point at an arbitrary intersection of the grid, so that the displacement of the myocardium is measured at the designated measurement point.
[0052]
That is, the intersections of the grids arranged on the ultrasonic image indicate the measurement points a1, a2, a3,... Of the physical parameters, and the operator performs a plurality of measurement operations shown on the ultrasonic image. A measurement point ax closest to a desired diagnostic site is selected from the points, and a template of a preset size (standard size) is set around the measurement point ax. By the way, as described above, the size of this template has a great influence on the accuracy of the cross-correlation processing. FIG. 4 shows the template size and the accuracy of the cross-correlation process in the present embodiment. It is well known that good measurement accuracy cannot be obtained when the template size is small. On the other hand, if the template size is set to an unnecessarily large size in the image data of an organ that is performing a complicated motion such as the heart, the image data of the parts in different directions of movement are mixed in the same template. Accuracy decreases. Therefore, optimization of the template size is required.
[0053]
In the present embodiment, a feature point is newly defined as a standard for obtaining stable measurement accuracy in the cross-correlation processing. These feature points are always generated with good S / N and are associated with image data that facilitates tracing between images. If the number of feature points in the template is equal to or greater than a predetermined value, good measurement is performed in the cross-correlation process. Accuracy is ensured.
[0054]
There are various methods for extracting the feature points. In the present embodiment, a corner detection method generally used in detecting a structure is applied. FIG. 5 schematically shows extraction of a feature point by the corner detection method. If the luminance value of the pixel P1 (x, y) in the myocardial image data is f1 (x, y), the X direction is assumed. 1st derivative value of the component and the Y-direction component, that is, Δf1 (xo, yo) = f1 (xo + 1, yo) −f1 (xo, yo) and Δf1 (xo, yo) = f1 (xo + 1, yo) −f1 ( xo, yo) or a pixel P1 (xo, yo) having a value greater than a predetermined value is defined as a feature point (step S4 in FIG. 10).
[0055]
FIG. 6 shows grids and feature points set on the ultrasonic image by the above procedure, and the feature points are generally arranged at irregular intervals. When performing cross-correlation processing between images using templates of the same size, centered on measurement points indicated by grid points on the ultrasonic image data, measurement accuracy differs depending on the measurement points. For this reason, the image operation circuit 22 of the image operation storage unit 6 in the present embodiment is configured so that a predetermined number (for example, 5 to 6) of feature points is included in the template set at the measurement point ax, for example. The template size is set, and if necessary, this template is displayed on the monitor 33 of the display unit 7 so as to be superimposed on the ultrasonic image A1 (step S5 in FIG. 10).
[0056]
Next, the image calculation circuit 22 calculates the displacement of the myocardium at the measurement point ax using the image data A1 and the image data A2. As shown in FIG. 7A, the signal intensity of the template P1 (p, q) set to the optimum size around the measurement point ax of the image data A1 is f1 (p, q), and the image If the signal intensity of the pixel P2 (p, q) of the data A2 is f2 (p, q), the following cross-correlation function γ ₁₂ By calculating (k, s), the displacement between the images at the measurement point ax can be measured.
[0057]
(Equation 1)

Here, Px and Py are the numbers of pixels in the X and Y directions in the template, and the measurement point ax set in the image A1 is set to P (Px / 2, Py / 2). As a result of this calculation, as shown in FIG. 7B, γ at k = k1 and s = s1 ₁₂ When (k, s) has the maximum value, it indicates that the myocardium at the measurement point ax is displaced by k1 in the X direction and s1 in the Y direction. Although FIG. 7B shows only the case where k is a parameter, the same can be obtained when s is a parameter.
[0058]
Next, the image operation circuit 22 reads out the image data A2 and the image data A3 in the same procedure. Then, a template of a Px pixel in the X direction and a template of a Py pixel in the Y direction is set around the movement destination P (Px / 2 + k1, Py / 2 + s1) in the image data A2 of the measurement point ax set in the image data A1, and this template is set. A cross-correlation process is performed between the image data A3 and the image data A3 to measure the displacement of the measurement point ax in the image data A3.
[0059]
Further, by repeating the same procedure, it is possible to measure the movement destination, that is, the displacement amount in the image data A3 to AM of the measurement point ax set in the image data A1. Further, it is possible to easily calculate physical parameters such as the moving speed (first derivative with respect to the displacement time) and the moving acceleration (second derivative with respect to the displacement time) from these displacement amounts (step S6 in FIG. 10). ).
[0060]
Note that the image data changes as the time phase of the image data is updated, and the distribution state of the feature points also changes. The cross-correlation processing is performed on the image data whose time phase changes as described above with the template size optimized by the same procedure as described above. That is, the optimization of the template size is performed in both the spatial and temporal regions.
[0061]
Next, the image calculation circuit 22 stores the time-varying curve data of various physical parameters at the measurement point ax obtained by the above method in the second storage area of the image data storage circuit 21 and monitors the display unit 7. Displayed at 33. FIG. 8 shows an example of an ultrasonic image displayed on the monitor 33 and a change curve of various physical parameters at this time. For example, the measurement points are shown in the left area of the monitor 33 (FIG. 8A). The image data A1 to image data AM on which the position information of ax is superimposed are repeatedly displayed (loop display), and the moving speed of the myocardium at the measurement point ax (see FIG. 8B) is displayed in the right area (FIG. 8B) of the monitor 33. 8 (b-1)), the displacement (FIG. 8 (b-2)), and the ECG (FIG. 8 (b-3)) indicating the phase are displayed, and the phase (Tx) of the image displayed in the left area is displayed. ) Are displayed on the change curves of the various physical parameters (step S7 in FIG. 10).
[0062]
According to the above-described embodiment, when measuring physical parameters such as movement displacement of a designated observation point by cross-correlation processing, cross-correlation processing can be performed using a template having an optimal size. Therefore, it is possible to measure a physical parameter at an arbitrary measurement point with high accuracy.
[0063]
In setting the template size, if this size exceeds the preset template size, the measurement of the physical parameters is interrupted, and the fact that measurement is impossible is displayed on the input unit 9 or the monitor 33 of the display unit 7. I do. That is, by notifying the operator that setting of the template at the desired measurement point is difficult, the operator can reset the second measurement point near the measurement point, so that the optimum measurement is always performed. It is possible to measure physical parameters with high accuracy using a template.
[0064]
(Modification)
In the above-described embodiment, measurement and display of various physical parameters at the measurement point ax specified by the operator have been described. However, the entire area of the image data or the operator uses an input device such as a mouse of the input unit 9. Alternatively, a grid may be arranged in an area manually set as described above, or in an image area based on an automatic image contour as described in JP-A-08-254604, and a plurality of grid points may be set as measurement points. .
[0065]
FIG. 9 shows an example of a method of displaying physical parameters in this modification. FIG. 9A shows, for example, each of the grid points (measurement points) set in the ultrasonic image data Ax. FIG. 9B shows the Y direction component of the moving speed obtained at the same measurement point. The magnitudes of these moving speed components are color-coded and displayed in color by being superimposed on a B-mode image displayed in unicolor. Alternatively, the magnitude of the X-direction component of the moving speed may be converted into lightness, and the magnitude of the Y-direction component may be converted into a color, and the color may be superimposed on one B-mode image for color display. Further, image data obtained by superimposing physical parameters such as moving speed on the B-mode image data and a tissue Doppler mode image generated by the Doppler mode processing unit 5 of the transmission / reception / image data generation unit 50 shown in FIG. By displaying the data or the blood flow Doppler mode image data side by side on the monitor 33 of the display unit 7, more cardiac function information can be obtained.
[0066]
When the movement of the myocardium is evaluated, it is also effective to display the traveling direction of the myocardium at each measurement point and the traveling speed component in the direction perpendicular to the traveling direction instead of the X direction and the Y direction. It is.
[0067]
(Second embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 13 is a flowchart showing a procedure of image data collection and physical parameter measurement in the present embodiment.
[0068]
The feature of the second embodiment resides in that the template size is optimized based on the size of a diagnosis target site such as a myocardium displayed on an ultrasonic image. Generally, the size of an organ greatly varies depending on the physique or medical condition of a subject. For this reason, for example, if the cross-correlation processing is performed by applying a template size optimized for a hypertrophied heart to normal-sized heart image data, the image data of the portions having different motion directions may be the same template. The probability of being included in the inside increases, leading to a decrease in measurement accuracy.
[0069]
The configuration of the ultrasonic diagnostic apparatus 100 according to the second embodiment and the generation and storage of the ultrasonic image data are the same as those of the first embodiment (step S11 in FIG. 13), and thus detailed description will be made. The description will be omitted, and the measurement of physical parameters for the collected ultrasonic image data will be described below.
[0070]
According to the same procedure as in the first embodiment, the displacement and the displacement at the diagnosis site of the myocardium are determined by using the M pieces of B-mode image data corresponding to one heartbeat stored in the image data storage circuit 21 of the image calculation storage unit 6. Measure physical parameters such as speed. The operator selects image data A1 to image data AM for one heartbeat from the B-mode image data stored in the image data storage circuit 21 in the input unit 9, and then selects the displacement of the myocardium as a physical parameter. (Step S12 in FIG. 13). These instruction signals input to the input unit 9 are supplied to the image operation circuit 22 via the system control unit 8, and the image operation circuit 22 reads out the image data A1 and the image data A2 from the image data storage circuit 21. Then, the image data A1 is displayed on the monitor 33 according to the instruction signal of the system control unit 8.
[0071]
Next, the operator measures the ultrasonic image of the heart displayed on the monitor 33 using, for example, an input device such as a mouse of the input unit 9 such as an annulus interval or an apex long axis length. FIG. 11 shows a method of measuring the annulus interval and the apical long axis length in the ultrasonic image of the heart. In the measurement of the annulus interval, the annulus portion which is the starting portion of the mitral valve on the image is shown. By designating b1 and b2 using a mouse, the position information of the annulus parts b1 and b2 is supplied to the image calculation circuit 22 via the system control unit 8, and the annulus distance L1 is measured. Further, by specifying the apical inner wall b3, the distance from the line segment connecting the valve annulus b1 and the valve annulus b2 to the apical inner wall b3, that is, the apical long axis length L2 is measured. In addition, the area and volume of the heart cavity, the thickness of the myocardial wall, and the like are measured by the same procedure (step S13 in FIG. 13).
[0072]
By measuring one or more of the above measurement parameters, the size of the subject's heart, the state of local hypertrophy, and the like can be grasped, and based on information related to the measured size of the organ. The image operation circuit 22 optimizes the size of the template used for the cross-correlation processing between images.
[0073]
The storage circuit of the image calculation circuit 22 has a table in which the optimum template size for the standard value of the measurement parameter is stored for each measurement site. FIG. 12A schematically shows a table in which the optimal values of the template size set for each measurement parameter and each measurement site are stored. FIG. 12B shows the measurement site. However, the template size values stored in this table are obtained from the results of past diagnostic experiences. The setting of the measurement area shown in FIG. 12B conforms to the wall motion evaluation standard of the American Society of Echocardiography (ASE), but is not limited to this setting method and is further subdivided. May be set.
[0074]
Then, the image calculation circuit 22 compares the measured values of the measurement parameters with the standard values stored in this table, and calculates the optimum template size for each measurement site by proportional calculation. For example, the template size S1 at the measurement site R1 of the heart with the annulus spacing L1 is determined by S1 = S0 · L1 / L0. However, S0 is the optimal template size at the measurement site R1 when the annulus interval is the standard value L0 (step S14 in FIG. 13).
[0075]
When the optimum template size for each measurement site is calculated in this manner, the image data A1, the image data A2, the image data A2, the image data A3,... Are obtained in the same manner as in the first embodiment. Cross-correlation processing is performed on the image data A (M-1) and the image data M using the above-described optimum template size, and measurement and display of desired physical parameters (step S15 in FIG. 13) (FIG. 13). Step S16) is performed. Note that these image processing methods are the same as those in the first embodiment, and a description thereof will be omitted.
[0076]
According to the second embodiment described above, since the template size is optimized by utilizing the past experience, the extraction of the feature points in the first embodiment becomes unnecessary, and the time required for the image calculation is reduced. It is possible to do.
[0077]
(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIG.
[0078]
In the first embodiment and the second embodiment, the optimal template size is set based on the image data, and the physical parameters of the predetermined part are measured using the optimal template. If the noise included in the image data is large, the measurement accuracy may not be stable. The third embodiment is made to solve such a problem, and the feature of the third embodiment is that physical parameters are measured a plurality of times using a plurality of templates having different sizes. An object is to extract data with good reproducibility from a plurality of measured values and determine values of physical parameters.
[0079]
The configuration of the ultrasonic diagnostic apparatus 100 according to the third embodiment and the generation and storage of the ultrasonic image data are the same as those of the first embodiment, and thus detailed description is omitted, and the collected ultrasonic data is omitted. A method of measuring physical parameters for image data will be described.
[0080]
According to the same procedure as in the first embodiment, the displacement and the displacement at the myocardium diagnosis site are determined using the M B-mode image data corresponding to one heartbeat stored in the image data storage circuit 21 of the image calculation storage unit 6. Measure physical parameters such as moving speed. The operator selects the image data A1 to image data AM for one heartbeat from the B-mode image data stored in the image data storage circuit 21 in the input unit 9, and then selects physical parameters to be measured (for example, myocardium). By selecting the measurement point ax and the measurement point ax, the system control unit 8 uses the image data A1 and the image data A2 to switch to the measurement mode of the physical parameter at the measurement point ax of the image data A1.
[0081]
Then, the image calculation circuit 22 of the image calculation storage unit 6 in FIG. 1 sets an optimal template size for the measurement point ax by, for example, a method similar to the first embodiment or the second embodiment, Further, Nx types of template sizes (template sizes TR-1 to TR-Nx) having different sizes centering on the optimum template size are set. After Nx types of template sizes are set in this way, the above Nx types of template sizes are applied to the image data A1 and the image data A2, and the cross-correlation processing is performed in the same procedure as in the first embodiment. Are sequentially performed, and the displacements Q-1 to Q-Nx of the myocardium are obtained from the result of the cross-correlation processing.
[0082]
FIG. 14 is a distribution (histogram) of the Nx displacement amounts Q-1 to Q-Nx obtained in this manner, and the horizontal axis indicates the value of the quantized physical parameter, that is, the magnitude of the displacement. The vertical axis indicates the frequency at which the quantized displacement amount occurs. The image calculation circuit 22 of the image calculation storage unit 6 creates such a histogram, further removes unique data Ca and Cb from the histogram, obtains a center value Qx of the histogram, and calculates a physical parameter (at the measurement point ax) at the measurement point ax. Displacement). Similarly, with respect to the image data A2 and the image data A3,..., The image data A (M-1) and the image data M, Nx displacement values are obtained using Nx types of template sizes, and the histograms thereof are obtained. The final displacement is set from the center value of.
[0083]
Next, the image operation circuit 22 performs a cross-correlation process using the set optimal template. Even when a plurality of measurement points are set on the image data, the physical parameters at the measurement points can be obtained with high accuracy by repeating the above procedure for each measurement point.
[0084]
According to the present embodiment described above, by setting the center value of the histogram to the value of the physical parameter, the physical parameter is measured with an equivalently optimal template size. Since such a method is introduced, it is possible to measure physical parameters with high accuracy even for image data having deteriorated S / N.
[0085]
The measurement of the physical parameters in the present invention can be configured separately from the transmission / reception / image data generation unit 50 and the ultrasonic probe 1 of the ultrasonic diagnostic apparatus 100. That is, as shown in FIG. 15, the medical image processing apparatus 51 including the input unit 9, the image operation storage unit 6, the system control unit 8, and the display unit 7 can be configured independently. In this case, the plurality of pieces of ultrasonic image data stored in the image data storage circuit 21 of the image calculation storage unit 6 are stored from an image diagnostic apparatus such as an separately configured ultrasonic diagnostic apparatus, X-ray CT apparatus, or MRI apparatus. Supplied via a medium or a communication cable, the image operation circuit 22 can measure the same physical parameters for image data obtained by these image diagnostic apparatuses.
[0086]
As described above, the embodiments of the present invention have been described, but the present invention is not limited to the above embodiments, and can be modified and implemented. For example, although the cross-correlation processing has been described as a putter matching method in the measurement of physical parameters, another method may be used. Although the measurement of the physical parameters in the ultrasonic image data of the heart has been described, the present invention can be applied to other medical image data.
[0087]
Further, the measurement parameters include the annulus spacing, apical long axis length, area, volume, and heart wall thickness, and the physical parameters include myocardial displacement, moving speed, moving acceleration, and strain, but are not limited thereto. Although the heart has been described as an organ to be diagnosed, it goes without saying that the present invention is also effective for other organs.
[0088]
【The invention's effect】
According to the present invention, the size of the template in the correlation processing between the image data can be optimized based on the image data, so that the diagnosis can be always performed with high accuracy in a short time.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an entire ultrasonic diagnostic apparatus according to a first embodiment of the present invention.
FIG. 2 is a diagram showing a configuration of a transmission / reception / image data generation unit in the embodiment.
FIG. 3 is a diagram showing grids and measurement points on an image according to the embodiment;
FIG. 4 is a diagram showing the template size and the accuracy of the correlation processing in the embodiment.
FIG. 5 is a diagram schematically showing a corner detection method in the embodiment.
FIG. 6 is a diagram showing characteristic points on an image according to the embodiment;
FIG. 7 is an exemplary view showing cross-correlation processing between images according to the embodiment;
FIG. 8 is a view showing a method for displaying an ultrasonic image and various physical parameters in the embodiment.
FIG. 9 is a view showing another display method of the ultrasonic image and various physical parameters in the embodiment.
FIG. 10 is an exemplary flowchart showing the procedure of image data collection and physical parameter measurement in the embodiment.
FIG. 11 is a diagram showing a method for measuring the annulus spacing and apical long axis length of the myocardium according to the second embodiment of the present invention.
FIG. 12 is a schematic diagram of a table in which the optimum value of the template size according to the embodiment is stored.
FIG. 13 is a flowchart showing a procedure of image data collection and physical parameter measurement in the embodiment.
FIG. 14 is a histogram of measured physical parameter values according to the third embodiment of the present invention.
FIG. 15 is a diagram showing a specific example of a medical image processing apparatus according to the present invention.
[Explanation of symbols]
1. Ultrasonic probe
2 ... Transmission unit
3 ... Receiver
4: B-mode processing unit
5. Doppler mode processing unit
6. Image operation storage unit
7 Display unit
8. System control unit
9 Input unit
10 biological signal measurement unit
21 ... Image data storage circuit
22 ... Image operation circuit
31 ... Display image memory
32 ... Conversion circuit
50: Transmission / reception / image data generation unit
100 ... ultrasonic diagnostic equipment

Claims (18)

An ultrasonic probe having an ultrasonic transducer for transmitting and receiving ultrasonic waves to and from the subject,
Transmitting and receiving means for transmitting and receiving to and from the ultrasonic transducer,
Image data generating means for generating ultrasonic image data from a reception signal obtained by the transmitting / receiving means,
Image data storage means for storing a plurality of ultrasonic image data generated by the image data generation means,
Image data selecting means for selecting at least two screens of ultrasonic image data from a plurality of ultrasonic image data stored in the image data storage means;
Feature point extracting means for extracting a feature point from first image data of the selected image data of at least two screens;
Template size setting means for setting a template size at one or more measurement points of the first image data based on the feature points extracted by the feature point extracting means;
Image calculation means for performing an image-to-image calculation with the second image data selected by the image data selection means, using a template having the size set by the template size setting means;
Physical parameter measurement means for measuring physical parameters at the measurement points based on the result of this inter-image calculation,
Display means for displaying a measurement result of the physical parameter. An ultrasonic probe having an ultrasonic transducer for transmitting and receiving ultrasonic waves to and from the subject,
Transmitting and receiving means for transmitting and receiving to and from the ultrasonic transducer,
Image data generating means for generating ultrasonic image data from a reception signal obtained by the transmitting / receiving means,
Image data storage means for storing ultrasound image data for a plurality of screens generated by the image data generation means;
Image data selecting means for selecting at least two screens of ultrasonic image data from a plurality of screens of ultrasonic image data stored in the image data storage means;
Measurement parameter measurement means for measuring measurement parameters in the first image data of the selected image data of at least two screens,
Template size setting means for setting a template size at a predetermined portion of the first image data based on a measurement value of the measurement parameter measurement means;
Image calculation means for performing an image-to-image calculation with the second image data selected by the image data selection means, using a template having the size set by the template size setting means;
Physical parameter measurement means for measuring physical parameters at the predetermined site based on the result of the inter-image calculation;
Display means for displaying a measurement result of the physical parameter. An ultrasonic probe having an ultrasonic transducer for transmitting and receiving ultrasonic waves to and from the subject,
Transmitting and receiving means for transmitting and receiving to and from the ultrasonic transducer,
Image data generating means for generating ultrasonic image data from a reception signal obtained by the transmitting / receiving means,
Image data storage means for storing ultrasound image data for a plurality of screens generated by the image data generation means;
Image data selecting means for selecting at least two screens of ultrasonic image data from a plurality of screens of ultrasonic image data stored in the image data storage means;
Template setting means for setting a plurality of templates having different sizes in a predetermined portion of the first image data of the selected image data of at least two screens;
An image calculating unit that performs an inter-image operation a plurality of times with the second image data selected by the image data selecting unit, using a plurality of templates set by the template setting unit;
Calculation value setting means for setting a desired calculation value based on a plurality of calculation results obtained in the inter-image calculation;
Physical parameter measurement means for measuring physical parameters in the predetermined portion based on the calculation value set by the calculation value setting means,
Display means for displaying a measurement result of the physical parameter. The image data selection means selects the first image data and the second image data from image data for a plurality of screens obtained in time series for the same part of the subject. The ultrasonic diagnostic apparatus according to any one of claims 1 to 3, wherein 2. The ultrasonic diagnostic apparatus according to claim 1, wherein the feature point extracting unit extracts a feature point by applying a corner detection method to the first image data. 3. The ultrasonic wave according to claim 2, wherein the measurement parameter measuring means measures at least one of a heart annulus interval, apical long axis length, heart chamber area, heart chamber volume, and heart wall thickness. Diagnostic device. 2. The method according to claim 1, wherein the template size setting unit sets a size of the template area formed at a measurement point of the first image data such that the feature point includes a predetermined number or more. An ultrasonic diagnostic apparatus as described in the above. The template size setting means, when the size of the template set at the measurement point exceeds a predetermined size, generates an instruction signal for not performing measurement of physical parameters at the measurement point. The ultrasonic diagnostic apparatus according to claim 7, wherein: 2. The image processing unit according to claim 1, wherein the first image data and the second image data are subjected to a cross-correlation calculation using a template set by the template size setting unit. An ultrasonic diagnostic apparatus according to claim 3. The physical parameter measuring unit measures at least one of displacement, moving speed, moving acceleration, strain, and strain speed at the predetermined portion of the myocardium based on a result of an inter-image calculation performed by the image calculating unit. The ultrasonic diagnostic apparatus according to any one of claims 1 to 3, wherein: 4. The calculation value setting unit according to claim 3, wherein the calculation value setting means sets the desired calculation value by performing a statistical process on a plurality of inter-image calculation results obtained using templates having different sizes. Ultrasound diagnostic equipment. 4. The display device according to claim 1, wherein the display unit displays the measurement result of the physical parameter measured by the physical parameter measurement unit in a manner superimposed on the ultrasound image data. 5. Ultrasound diagnostic equipment. Image data storage means for storing a plurality of screens of medical image data generated by the medical image diagnostic apparatus;
Image data selection means for selecting at least two screens of medical image data from a plurality of screens of medical image data stored in the image data storage means;
Feature point extracting means for extracting a feature point from first image data of the selected image data of at least two screens;
Template size setting means for setting a template size at one or more measurement points of the first image data based on the feature points extracted by the feature point extracting means;
Image calculation means for performing an image-to-image calculation with the second image data selected by the image data selection means, using a template having the size set by the template size setting means;
Physical parameter measurement means for measuring physical parameters at the measurement points based on the result of this inter-image calculation,
Display means for displaying the measurement result of the physical parameter. Image data storage means for storing a plurality of screens of medical image data generated by the medical image diagnostic apparatus;
Image data selection means for selecting at least two screens of medical image data from a plurality of screens of medical image data stored in the image data storage means;
Measurement parameter measurement means for measuring measurement parameters in the first image data of the selected image data of at least two screens,
Template size setting means for setting a template size at a predetermined portion of the first image data based on a measurement value of the measurement parameter measurement means;
Image calculation means for performing an image-to-image calculation with the second image data selected by the image data selection means, using a template having the size set by the template size setting means;
Physical parameter measurement means for measuring physical parameters at the predetermined site based on the result of the inter-image calculation;
Display means for displaying the measurement result of the physical parameter. Image data storage means for storing a plurality of screens of medical image data generated by the medical image diagnostic apparatus;
Image data selecting means for selecting at least two screens of ultrasonic image data from a plurality of screens of ultrasonic image data stored in the image data storage means;
Template setting means for setting a plurality of templates having different sizes in a predetermined portion of the first image data of the selected image data of at least two screens;
An image calculating unit that performs an inter-image operation a plurality of times with the second image data selected by the image data selecting unit, using a plurality of templates set by the template setting unit;
Calculation value setting means for setting a desired calculation value based on a plurality of calculation results obtained in the inter-image calculation;
Physical parameter measurement means for measuring physical parameters in the predetermined portion based on the calculation value set by the calculation value setting means,
Display means for displaying the measurement result of the physical parameter. Selecting at least two screens of medical image data from the stored plurality of screens of medical image data;
Extracting a feature point from first image data of the selected image data of at least two screens;
Setting a template size at one or more measurement points of the first image data based on the extracted feature points;
Performing an inter-image operation with the second image data using a template of the set size;
Measuring physical parameters at the measurement points based on the result of the inter-image calculation;
Displaying the measurement result of the physical parameter. Selecting at least two screens of medical image data from the stored plurality of screens of medical image data;
Measuring a measurement parameter in the first image data of the selected image data of at least two screens;
Setting a template size at a predetermined portion of the first image data based on the measurement value of the measurement parameter;
Performing an inter-image operation with the second image data using a template of the set size;
Measuring physical parameters at the measurement points based on the result of the inter-image calculation;
Displaying the measurement result of the physical parameter. Selecting at least two screens of medical image data from the stored plurality of screens of medical image data;
Setting a plurality of templates having different sizes in a predetermined portion of the first image data of the selected image data of at least two screens;
Performing a plurality of inter-image operations with the second image data using the plurality of set templates;
Setting a desired operation value based on a plurality of operation results obtained in the inter-image operation;
Measuring physical parameters at the predetermined site based on the set operation value,
Displaying the measurement result of the physical parameter.

Images