JP3630812B2 - X-ray diagnostic imaging equipment - Google Patents

Description

このときのＭを幾何学的拡大率と呼ぶ。
従って、投影像の長さ１’をＭで割るという補正により、実際の長さ１を求めることができる。
【０００４】
一方、より的確に疾患程度を診断するため、複数の撮影角度から被験体を同時にＸ線撮影する手法がある。一般に用いられているのは、２対のＸ線管と検出器によるバイプレーン構成の撮影システムである。このシステムで得られる２種類のＸ線画像を各々正面像、側面像と呼ぶ。一般に、正面像と側面像それぞれについて、定量解析手法を実施すると、計測精度は向上する。例えば、血管狭窄率計測における血管断面積の算出では、図１４に示すように、１枚のＸ線画像の場合、その部位で算出した血管径を用いて円形近似して求めるが、バイプレーン画像の場合は、血管径が２種類算出されるので、楕円近似して求められ、より実際の断面積に近い値が得られる。
【０００５】
【発明が解決しようとする課題】
上述のＸ線画像診断装置で得られるＸ線画像は、投影像である。このため、対象物体が撮影方向と垂直な平面内に存在する場合は、問題ないが、対象物体が撮影方向と同方向に変動して存在する場合、すなわち奥行き方向に変動を持つ場合は、この奥行き方向の変動により、奥行き分の誤差を含んだ計測値を得ることになる。例えば、図１５に示すように、同じ長さ１を持つ物体Ａ，Ｂの位置が奥行き方向で異なる場合、幾何学的拡大率が異なるため、Ｉ．Ｉ．前面上に投影される長さは各々１’、１”と異なる。ここで、物体Ａ、Ｂとともに撮影方向と垂直な平面内に存在しているとみなすと、同じ幾何学的拡大率で補正されるため、実際の長さとして算出される値は、物体Ａ，Ｂでは異なってしまう。このような誤差を補正するための情報を１枚の投影像（シングルプレーン像）から得ることは難しい。
【０００６】
また，バイプレーン画像を用いても、直接的には奥行き方向の変動を検出することは容易ではなく、シングルプレーン画像の場合と同様に奥行き分の誤差を含んだ計測値を得ることになる。
【０００７】
本発明の目的は、例えば血管や心機能の定量解析において、対象となる物体の奥行き分の変動を考慮した精度の高い計測値を得ることができるＸ線画像診断装置を提供することにある。
【０００８】
【課題を解決するための手段】
上記目的を達成するため、請求項１記載の本発明は、Ｘ線管とＸ線検出器との間に存在する被検体に対して、複数方向からＸ線画像を撮影する撮影手段と、この撮影手段により撮影したＸ線画像から被検体の診断部位の血管定量解析を行う定量解析手段と、前記複数方向から撮影したＸ線画像において対応する位置を指定する対応点指定手段と、この対応点指定手段により指定した対応点における前記Ｘ線管と被検体との間の距離と、前記被検体と前記検出器との間の距離との比で計算される幾何学的拡大率を算出する算出手段と、この算出手段により算出した幾何学的拡大率を用いて前記定量解析手段による定量解析の結果を補正する補正手段とを備える。
【０００９】
上記本発明により、複数方向から撮影したＸ線画像を利用して、対象物体の各位置において局所的な幾何学的拡大率を算出し、これを利用して定量解析結果を補正することができ、奥行き分の変動を考慮した精度の高い計測値が得られる。
【００１０】
【発明の実施の形態】
図１に、本発明のＸ線画像診断装置の実施例に関わる装置構成を示す。
図１のＸ線画像診断装置は、バイプレーン構成のシステムであり、Ｘ線管１、テーブル２、Ｉ．Ｉ．（イメージインテンシファイア）３、ＴＶカメラ４、Ａ／Ｄ変換器５、フレームメモリ６、画像処理メモリ７、グラフィック描画メモリ８、ＣＰＵ（中央処理装置）９、入力器１０、画像合成器１１、Ｄ／Ａ変換器１２、モニタ１３、および撮影支持器駆動制御部１４から構成されている。本システムにて、撮影した正面像（Ｆ像）と側面像（Ｌ像）の画像は、それぞれＡ／Ｄ変換器５を介して、フレームメモリ６に格納され、さらに画像合成器１１、Ｄ／Ａ変換器１２を介して、モニタ１３に表示される。定量解析処理は、ＣＰＵ９が行う画像処理メモリ７に格納された画像に対する画像処理によって実現される。解析結果は、グラフィック描画メモリ８に描画され、画像合成器１１、Ｄ／Ａ変換器１２を介して、モニタ１３に表示される。
【００１１】
図２に、本発明の実施例に関わる処理の流れを示す。
まず、「バイプレーン画像の収集」（ＳＴＥＰ１）では、被験体をＦ／Ｌ両側からＸ線撮影して、このとき得たＦ像とＬ像を各々フレームメモリ６に格納する。次に、「Ｆ／Ｌ像の選定」（ＳＴＥＰ２）では、定量解析を行うための対象となる画像一組（Ｆ像とＬ像）を操作者に選定させる。さらに、「定量解析処理」（ＳＴＥＰ３）にて、所望の定量解析を行う。このとき得た解析結果を「補正処理」（ＳＴＥＰ４）にて補正し、「解析結果表示」（ＳＴＥＰ５）にてこの補正結果をモニタ１３を用いて操作者に呈示する。
【００１２】
以下、本発明のポイントである補正処理について詳しく説明する。
補正処理は、「対応点の指定」、「幾何学的拡大率の算出」および「解析結果の補正」の３つの処理に分けられる。以下に、２つの補正処理の実施例を説明する。
【００１３】
本発明の一例のＸ線画像診断装置における補正処理例を説明する。図３に、「定量解析処理」（ＳＴＥＰ２）にて実行された血
管狭窄率計測結果の例を示す。（ａ）は血管の長さ方向各位置における血管径を示し、（ｂ）は血管の長さ方向各位置における血管狭窄率を示している。すなわち、対象血管の血管径および血管狭窄率の変化の様子を示す曲線である。ここで血管狭窄率とは、血管の長さ方向各位置における血管径の値と、正常血管径の値の比率で与えられる血管の狭窄度合いを示すものであり、次の通りである。
【００１４】
狭窄率＝１−（狭窄血管径／正常血管径）
つまり、血管狭窄率の低い部位が病変部として特定でき、これにより血管の疾患状態を把握できる。
【００１５】
図４に、定量解析の対象となったＦ／Ｌ両側の血管造影像を示す。この一組の画像に対して、「対応点の指定」を行う。ここでは、対応点はマニュアルで指定することとし、対象血管の両端と最も狭窄している点の計３点を指定することとする。なお、本指定操作は、操作者による入力器１０による入力操作に連動するグラフィック描画メモリ７上のカーソルを、画像合成器１１、Ｄ／Ａ変換器１２、およびモニタ１３を用いて、血管造影像と合成して表示することで実現する。図５に、Ｆ／Ｌ両側の血管造影像上に指定したそれぞれの対応点ｐＦ１、ｐＦ２、ｐＦ３、ｐＬ１、ｐＬ２、ｐＬ３を示す。
【００１６】
図６に、「幾何学的拡大率の算出」における処理の手順を示す。「セグメント分割」では、３組の対応点に基づいて、対象血管を３つに分割する。隣合う対応点の中間点で、分割を行い、分割されたセグメントをそれぞれＡ，Ｂ，Ｃと呼ぶ。このセグメント毎に、「セグメント毎の局所的幾何学的拡大率の算出」を行う。すなわち、セグメントＡでは対応点の組（ｐＦ１、ｐＬ１）、セグメントＢでは対応点の組（ｐＦ２、ｐＬ２）、セグメントＣでは対応点の組（ｐＦ３、ｐＬ３）を用いて算出する。ここで、一組の対応点に基づく、Ｆ／Ｌ像上の対応点各々の幾何学的拡大率の算出は、後述する公知の手法を用いて行う。
【００１７】
次に行う「解析結果の補正」では、血管径または血管狭窄率を、それらの属するセグメントで算出した局所的幾何学的拡大率を用いて補正する。
上述の本発明のＸ線画像診断装置の処理により、セグメント毎の局所的幾何学的拡大率を用いて定量解析結果の補正を行うため、精度の高い計測値が得られる。
【００１８】
次に、本発明の他の例のＸ線画像診断装置における補正処理例を説明する。
「定量解析処理」（ＳＴＥＰ３）にて行われる心機能解析では、拡張末期と収縮末期の左心室造影像の心容積計測結果に基づいて、心駆出率計測や心内壁の収縮度合いを求める局所壁運動解析を行う。
【００１９】
図７にシンプソン法に基づく心容積計測の概略を示す。シンプソン法では、大動脈弁ｐＶ１、ｐＶ２の中点と心尖部ｐＡ を結ぶ線（以下、長軸と呼ぶ）と直交する直線と、心輪郭とが交わる２点を結ぶ線分１ｉを用いて、下式のように心容積Ｖを求める。すなわち、数２により局所心容積△Ｖｉを算出し、この局所心容積△Ｖｉを数３のように足し合わせてＶ０ を求める。これを数４を用いて、心外形などから補正をすることにより心容積Ｖを算出する。
【００２０】
【数２】

【００２１】
【数３】

【００２２】
【数４】

【００２３】
図８に、定量解析の対象となるＦ／Ｌ両側の左心室造影像を示す。この一組の画像に対して、「対応点の指定」を行う。ここでは、対応点はマニュアルで指定することとし、長軸の両端点の計２点を指定することとする。図９に、Ｆ／Ｌ両側の左心室造影像上に指定したそれぞれの対応点ｐＦ１、ｐＦ２、ｐＬ１、ｐＬ２を示す。
図１０に、「幾何学的拡大率の算出」における処理の手順を示す。
【００２４】
「対応点の局所的幾何学的拡大率の算出」では、対応点毎に局所的幾何学的拡大率を算出する。ここで、一組の対応点に基づく、Ｆ／Ｌ像上の対応点各々の幾何学的拡大率の算出は、後述する公知の手法を用いて行う。「対応点以外の局所的幾何学的拡大率の算出」では、先に求めた２つの対応点での局所的幾何学的拡大率Ｍ１、Ｍ２を用いて、その間に存在する長軸上の点の局所的幾何学的拡大率Ｍｉを、数５によって求める。この数５は、長軸上の点をＮ等分したときの位置ｉにおける局所的幾何学的拡大率Ｍｉを、線形補間により算出するということを示している。
【００２５】
【数５】

【００２６】
次に行う「解析結果の補正」では、線分１ｉを数５で算出した局所的幾何学的拡大率Ｍｉを用いて補正する。
上述の本発明のＸ線画像診断装置の処理により、指定した対応点間の局所的幾何学的拡大率を線形補間により算出し、これを用いて定量解析結果の補正を行うため、精度の高い計測値が得られる。
【００２７】
以下、幾何学的拡大率の算出方法について説明する。
図１１に、バイプレーン撮影システムにおける本算出方法を説明する模式図を示す。直交するＦ／Ｌ両側のＸ線軸の交点（以下、アイソセンターと呼ぶ）Ｏを空間座標の原点（０，０，０）とする。ただし、被検体１５の背から腹の方向をＸ方向、左右方向をＹ方向、足頭方向をＺ方向とする。
【００２８】
Ｆ側のＸ線管球焦点ＦｘとアイソセンターＯとの距離を１ｘとし、この焦点座標を（−１ｘ，０，０）とする。同様に、Ｌ側のＸ線管球焦点ＦｙとアイソセンターＯとの距離を１ｙとし、この焦点座標を（０，−１ｙ，０）とする。
【００２９】
アイソセンターＯよりｐｘ、ｑｙ離れたＩ．Ｉ．３ａ，ｂ前面の中心座標は各々（ｐｘ，０，０）（０，ｑｙ，０）となる。また、空間のある一点のＩ．Ｉ．３ａ，ｂ入力面上の対応点の座標は、各々Ｐ（ｐｘ，ｐｙ，ｐｚ）、Ｑ（ｑｘ，ｑｙ，ｑｚ）となる。
【００３０】
これから先、ベクトルａを［ａ］と記述することにする。
Ｆｘ、ＦｙからそれぞれＰ、Ｑへのベクトルを方向ベクトル［１ｘ］＝（ｐｘ，ｐｙ，ｐｚ）、［１ｙ］＝（ｑｘ，ｑｙ，ｑｚ）とする。
【００３１】
点Ｆｘ（−１ｘ，０，０）を通り、方向ベクトル［１ｘ］＝（ｐｘ，ｐｙ，ｐｚ）を持つ直線の方程式はＬｘ＝（ｐｘ＋１ｘ，ｐｙ，ｐｚ）である。このとき、点Ｆｘを通り、ベクトル［１ｘ］の動点をｍ１とし、ｓを任意の実数とするとき、ｍ１の座標は以下の通り。
【００３２】
ｘ＝−１ｘ＋ｓ×（ｐｘ＋１ｘ）
ｙ＝ｓ×ｐｙ
ｚ＝ｓ×ｐｚ （ただし、−∞＜ｓ＜∞）
点Ｆｙ（０，−１ｙ，０）を通り、方向ベクトル［１ｙ］＝（ｑｘ，ｑｙ，ｑｚ）を持つ直線の方程式は［１ｙ］＝（ｑｘ，ｑｙ＋１ｙ，ｑｚ）である。
【００３３】
このとき、点Ｆｙを通り、ベクトル［１ｙ］の動点をｍ２とし、ｔを任意の実数とするとき、ｍ２の座標は以下の通り。
ｘ＝ｔ×ｑｘ
ｙ＝−１ｙ＋ｔ×（ｑｙ＋１ｙ）
ｚ＝ｔ×ｑｚ （ただし、−∞＜ｔ＜∞）
図１２に示すように、計測点に誤差を生じた場合を考える。
【００３４】
このとき、ベクトル［１ｘ］上の動点ｍ１とベクトル［１ｙ］上の動点ｍ２の間にベクトル［ｍ］が存在する。このベクトル［ｍ］の座標は以下の通り。
ｘ＝−１ｘ＋ｓ×（ｐｘ＋１ｘ）−ｔ×ｑｘ
ｙ＝ｓ×ｐｙ＋１ｙ−ｔ×（ｑｙ＋１ｙ）
ｚ＝ｓ×ｐｚ−ｔ×ｑｚ
ベクトル［１ｘ］とベクトル［１ｙ］に交点が存在しない場合、動点ｍ１と動点ｍ２が最も近づく点は、ベクトル［ｍ］がベクトル［１ｘ］とベクトル［１ｙ］の共通垂線となるときである。対象物体の位置をこの点に近似する。一般に、２つのベクトル［ａ］，［ｂ］があるとき、
【００３５】
【数６】

であるから、
【００３６】
【数７】

【００３７】
上式より、内積の和が０となる点がｓ＝ｓ０、ｔ＝ｔ０とすると、ベクトル ［ｍ１０］、［ｍ２０］は、
［ｍ１０］＝（−１ｘ＋ｓ０×（ｐｘ＋１ｘ）、ｓ０×ｐｙ、ｓ０×ｐｚ）［ｍ２０］＝（ｔ０×ｑｘ、−１ｙ＋ｔ０×（ｑｘ＋１ｙ）、ｔ０×ｑｚ）となり、ベクトル［ｍ］の中点の座標は、
ｘ＝｛−１ｘ＋ｓ０×（ｐｘ＋１ｘ）＋ｔ０×ｑｘ｝／２
ｙ＝｛ｓ０×ｐｙ−１ｙ＋ｔ０×（ｑｙ＋１ｙ）｝／２
ｚ＝（ｓ０×ｐｚ＋ｔ０×ｑｚ）／２
となる。
従って、ＰからＦｘまでのＸ座標での距離をＳＩＤ、Ｐから［ｍ］の中点までのＸ座標での距離をＰＩＤとおくと、Ｆ側像の幾何学的拡大率は、
【００３８】
【数８】

同様に、Ｌ側像の幾何学的拡大率は、
【００３９】
【数９】

となる。
なお、以上の計算はＣＰＵ９にて行い、Ｘ線管やＩ．Ｉ．等の位置情報は撮影支持器駆動制御装置１４より得る。
【００４０】
【発明の効果】
本発明のＸ線画像診断装置により、Ｘ線画像による定量解析において、対象となる物体の奥行き分の変動を考慮した精度の高い計測値を得ることができる。
【図面の簡単な説明】
【図１】本発明のＸ線画像診断装置の構成例
【図２】本発明のＸ線画像診断装置の処理の流れ
【図３】血管狭窄率の計測結果
【図４】Ｆ／Ｌ両側の血管造影像
【図５】Ｆ／Ｌ両側の血管造影像上に指定した対応点
【図６】幾何学的拡大率の算出処理の流れ
【図７】シンプソン法に基づく心容積計測
【図８】Ｆ／Ｌ両側の左心室造影像
【図９】Ｆ／Ｌ両側の左心室造影像上に指定した対応点
【図１０】幾何学的拡大率の算出処理の流れ
【図１１】バイプレーン撮影システム
【図１２】Ｆ／Ｌ両側の方向ベクトル
【図１３】幾何学的拡大率による補正方法
【図１４】血管狭窄率の計測における血管断面積の算出方法
【図１５】奥行き方向に変動して存在する物体の例
【符号の説明】
１ Ｘ線管
２ テーブル
３ Ｉ．Ｉ．
４ ＴＶカメラ
５ Ａ／Ｄ変換器
６ フレームメモリ
７ 画像処理メモリ
８ グラフィックメモリ描画メモリ
９ ＣＰＵ
１０ 入力器
１１ 画像合成器
１２ Ｄ／Ａ変換器
１３ モニタ
１４ 撮影支持器駆動制御部
１５ 被検体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an X-ray image diagnostic apparatus, and more particularly to a technique for performing quantitative analysis of a diagnostic part of a subject.
[0002]
[Prior art]
Diagnosis of a circulatory system disease includes a method of using an X-ray image when a contrast medium is injected into a target site with a catheter inserted into a subject. Some X-ray image diagnostic apparatuses used in this method include not only morphological diagnosis but also a quantitative analysis method for quantitatively grasping the degree of disease. This quantitative analysis method includes, for example, blood vessel quantitative analysis such as blood vessel diameter measurement and blood vessel stenosis rate measurement in order to grasp the degree of vascular stenosis disease. Further, heart volume measurement, cardiac ejection fraction measurement, and the like are known as cardiac function quantitative analysis. In these quantitative analyses, measurement values are corrected based on information such as the geometric magnification. FIG. 13 shows a correction method based on the geometric enlargement ratio. Consider a case where an object A existing between an X-ray tube 1 and an image intensifier (II) 3 serving as a detector is photographed. The length of this object A is set to 1, I.I. I. 3 of the projected image A ′ of the object A projected onto the front surface is 1 ′, and the X-ray tube 1 and the I.D. I. Of the object A and I. I. 1 ′ is obtained by the following equation.
[0003]
[Expression 1]

M at this time is called a geometric magnification.
Therefore, the actual length 1 can be obtained by correcting that the length 1 ′ of the projected image is divided by M.
[0004]
On the other hand, in order to more accurately diagnose the degree of disease, there is a method of simultaneously X-raying a subject from a plurality of imaging angles. In general, an imaging system having a biplane configuration using two pairs of X-ray tubes and detectors is used. Two types of X-ray images obtained by this system are called a front image and a side image, respectively. In general, when a quantitative analysis method is performed on each of the front image and the side image, the measurement accuracy is improved. For example, in the calculation of the blood vessel cross-sectional area in the blood vessel stenosis rate measurement, as shown in FIG. 14, in the case of a single X-ray image, it is obtained by circular approximation using the blood vessel diameter calculated at that part. In the case of (2), since two types of blood vessel diameters are calculated, they are obtained by ellipse approximation, and a value closer to the actual cross-sectional area is obtained.
[0005]
[Problems to be solved by the invention]
The X-ray image obtained by the above-described X-ray image diagnostic apparatus is a projection image. For this reason, there is no problem if the target object exists in a plane perpendicular to the shooting direction, but if the target object fluctuates in the same direction as the shooting direction, that is, if there is a change in the depth direction, this A measurement value including an error corresponding to the depth is obtained due to the variation in the depth direction. For example, as shown in FIG. 15, when the positions of the objects A and B having the same length 1 are different in the depth direction, the geometric magnification is different. I. The length projected on the front surface is different from 1 ′ and 1 ″, respectively. Here, assuming that the objects A and B exist in a plane perpendicular to the shooting direction, correction is performed with the same geometric magnification. Therefore, the value calculated as the actual length differs between the objects A and B. It is difficult to obtain information for correcting such an error from one projection image (single plane image). .
[0006]
Even if a biplane image is used, it is not easy to detect a variation in the depth direction directly, and a measurement value including an error corresponding to the depth is obtained as in the case of a single plane image.
[0007]
An object of the present invention is to provide an X-ray diagnostic imaging apparatus capable of obtaining a highly accurate measurement value in consideration of variation in depth of a target object in, for example, quantitative analysis of blood vessels and cardiac functions.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention according to claim 1 includes an imaging means for imaging X-ray images from a plurality of directions with respect to a subject existing between an X-ray tube and an X-ray detector , Quantitative analysis means for performing blood vessel quantitative analysis of the diagnostic site of the subject from the X-ray image taken by the imaging means, corresponding point designating means for designating corresponding positions in the X-ray images taken from the plurality of directions, and the corresponding points Calculation for calculating a geometric enlargement ratio calculated by a ratio between the distance between the X-ray tube and the subject at the corresponding point designated by the designation means and the distance between the subject and the detector Means, and correction means for correcting the result of the quantitative analysis by the quantitative analysis means using the geometric enlargement ratio calculated by the calculation means.
[0009]
According to the present invention, it is possible to calculate a local geometric magnification at each position of a target object using X-ray images taken from a plurality of directions, and use this to correct the quantitative analysis result. A highly accurate measurement value that takes into account variations in depth can be obtained.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an apparatus configuration relating to an embodiment of the X-ray image diagnostic apparatus of the present invention.
The X-ray diagnostic imaging apparatus of FIG. 1 is a system having a biplane configuration. I. (Image intensifier) 3, TV camera 4, A / D converter 5, frame memory 6, image processing memory 7, graphic drawing memory 8, CPU (central processing unit) 9, input device 10, image synthesizer 11, It comprises a D / A converter 12, a monitor 13, and a photographing supporter drive controller 14. In this system, the captured front image (F image) and side image (L image) are respectively stored in the frame memory 6 via the A / D converter 5, and further, the image synthesizer 11, D / D The data is displayed on the monitor 13 via the A converter 12. The quantitative analysis process is realized by image processing performed on the image stored in the image processing memory 7 by the CPU 9. The analysis result is drawn in the graphic drawing memory 8 and displayed on the monitor 13 via the image synthesizer 11 and the D / A converter 12.
[0011]
FIG. 2 shows a flow of processing according to the embodiment of the present invention.
First, in “collection of biplane images” (STEP 1), the subject is X-rayed from both sides of the F / L, and the F image and L image obtained at this time are stored in the frame memory 6, respectively. Next, in “selection of F / L image” (STEP 2), the operator selects a set of images (F image and L image) to be subjected to quantitative analysis. Furthermore, a desired quantitative analysis is performed in “quantitative analysis processing” (STEP 3). The analysis result obtained at this time is corrected by “correction processing” (STEP 4), and this correction result is presented to the operator using the monitor 13 at “analysis result display” (STEP 5).
[0012]
Hereinafter, the correction process which is the point of the present invention will be described in detail.
The correction process is divided into three processes: “designation of corresponding points”, “calculation of geometric magnification ratio”, and “correction of analysis result”. Hereinafter, examples of two correction processes will be described.
[0013]
An example of correction processing in the X-ray image diagnostic apparatus according to an example of the present invention will be described. FIG. 3 shows an example of the blood vessel stenosis rate measurement result executed in the “quantitative analysis process” (STEP 2). (A) shows the blood vessel diameter at each position in the length direction of the blood vessel, and (b) shows the blood vessel stenosis rate at each position in the length direction of the blood vessel. That is, it is a curve showing a change in the blood vessel diameter and the stenosis rate of the target blood vessel. Here, the vascular stenosis rate indicates the degree of stenosis of the blood vessel given by the ratio of the value of the blood vessel diameter at each position in the length direction of the blood vessel and the value of the normal blood vessel diameter, and is as follows.
[0014]
Stenosis rate = 1- (stenosis vessel diameter / normal vessel diameter)
In other words, a site with a low vascular stenosis rate can be identified as a lesion, thereby grasping the disease state of the blood vessel.
[0015]
FIG. 4 shows angiographic images on both sides of the F / L that have been subjected to quantitative analysis. “Specify corresponding points” is performed on this set of images. Here, the corresponding points are designated manually, and a total of three points are designated, that is, both ends of the target blood vessel and the most narrowed point. In this specification operation, an angiographic image is displayed by using the image synthesizer 11, the D / A converter 12, and the monitor 13 with the cursor on the graphic drawing memory 7 linked to the input operation by the input device 10 by the operator. This is realized by combining and displaying. FIG. 5 shows the corresponding points pF1, pF2, pF3, pL1, pL2, and pL3 designated on the angiographic images on both sides of the F / L.
[0016]
FIG. 6 shows a processing procedure in the “calculation of geometric enlargement ratio”. In “segment division”, the target blood vessel is divided into three based on three sets of corresponding points. A division is performed at an intermediate point between adjacent corresponding points, and the divided segments are referred to as A, B, and C, respectively. For each segment, “calculation of local geometric magnification for each segment” is performed. That is, the segment A is calculated using the corresponding point pair (pF1, pL1), the segment B using the corresponding point pair (pF2, pL2), and the segment C using the corresponding point pair (pF3, pL3). Here, the calculation of the geometric enlargement ratio of each corresponding point on the F / L image based on a set of corresponding points is performed using a known method described later.
[0017]
In the next “correction of analysis result”, the blood vessel diameter or the blood vessel stenosis rate is corrected using the local geometric enlargement rate calculated for the segment to which the blood vessel belongs.
Since the quantitative analysis result is corrected using the local geometric magnification for each segment by the processing of the above-described X-ray diagnostic imaging apparatus of the present invention, a highly accurate measurement value is obtained.
[0018]
Next, an example of correction processing in the X-ray image diagnostic apparatus of another example of the present invention will be described.
In the cardiac function analysis performed in the “quantitative analysis process” (STEP 3), the local ejection ratio measurement and the degree of contraction of the endocardial wall are determined based on the cardiac volume measurement results of left ventricular angiograms at the end diastole and end systole. Perform wall motion analysis.
[0019]
FIG. 7 shows an outline of cardiac volume measurement based on the Simpson method. In the Simpson method, a line segment 1i connecting two points where a straight line perpendicular to a line connecting the midpoints of the aortic valves pV1 and pV2 and the apex pA (hereinafter referred to as a major axis) and a heart outline intersect is used. The heart volume V is obtained as in the equation. That is, the local heart volume ΔVi is calculated according to Equation 2, and the local heart volume ΔVi is added as shown in Equation 3 to obtain V0. The cardiac volume V is calculated by correcting this from the outer shape of the heart using Equation 4.
[0020]
[Expression 2]

[0021]
[Equation 3]

[0022]
[Expression 4]

[0023]
FIG. 8 shows left ventricular contrast images on both sides of the F / L that are the targets of quantitative analysis. “Specify corresponding points” is performed on this set of images. Here, the corresponding points are designated manually, and a total of two points on both ends of the major axis are designated. FIG. 9 shows the corresponding points pF1, pF2, pL1, and pL2 designated on the left ventricular contrast image on both sides of the F / L.
FIG. 10 shows a processing procedure in the “calculation of geometric magnification”.
[0024]
In “calculation of local geometric enlargement ratio of corresponding points”, a local geometric enlargement ratio is calculated for each corresponding point. Here, the calculation of the geometric enlargement ratio of each corresponding point on the F / L image based on a set of corresponding points is performed using a known method described later. In “calculation of local geometric magnification other than corresponding points”, a point on the long axis existing between the two corresponding geometric points of magnification M1 and M2 obtained previously is used. The local geometric enlargement ratio Mi is determined by Equation 5. Equation 5 indicates that the local geometric magnification Mi at the position i when the point on the long axis is equally divided into N is calculated by linear interpolation.
[0025]
[Equation 5]

[0026]
In the “correction of analysis result” to be performed next, the line segment 1i is corrected using the local geometric enlargement ratio Mi calculated by Expression 5.
With the above-described processing of the X-ray image diagnostic apparatus of the present invention, the local geometric enlargement ratio between designated corresponding points is calculated by linear interpolation, and the quantitative analysis result is corrected using this, so that the accuracy is high. A measured value is obtained.
[0027]
Hereinafter, a method for calculating the geometric magnification will be described.
FIG. 11 is a schematic diagram illustrating this calculation method in the biplane imaging system. The intersection (hereinafter referred to as isocenter) O of the X-ray axes on both sides of the orthogonal F / L is defined as the origin (0, 0, 0) of the spatial coordinates. However, the direction from the back to the abdomen of the subject 15 is the X direction, the left-right direction is the Y direction, and the ankle direction is the Z direction.
[0028]
The distance between the X-ray tube focal point Fx on the F side and the isocenter O is 1x, and this focal point coordinate is (-1x, 0, 0). Similarly, the distance between the X-ray tube focal point Fy on the L side and the isocenter O is 1y, and this focal point coordinate is (0, -1y, 0).
[0029]
I.I. is separated from the isocenter O by px and qy. I. The center coordinates of the front surfaces of 3a and b are (px, 0, 0) (0, qy, 0), respectively. In addition, an I.D. I. The coordinates of the corresponding points on the 3a and b input surfaces are P (px, py, pz) and Q (qx, qy, qz), respectively.
[0030]
From now on, the vector a will be described as [a].
The vectors from Fx and Fy to P and Q, respectively, are set as direction vectors [1x] = (px, py, pz) and [1y] = (qx, qy, qz).
[0031]
The equation of a straight line passing through the point Fx (−1x, 0, 0) and having the direction vector [1x] = (px, py, pz) is Lx = (px + 1x, py, pz). At this time, when passing through the point Fx, the moving point of the vector [1x] is m1, and s is an arbitrary real number, the coordinates of m1 are as follows.
[0032]
x = −1x + s × (px + 1x)
y = s × py
z = s × pz (where −∞ <s <∞)
A straight line equation passing through the point Fy (0, −1y, 0) and having a direction vector [1y] = (qx, qy, qz) is [1y] = (qx, qy + 1y, qz).
[0033]
At this time, when passing through the point Fy, the moving point of the vector [1y] is m2, and t is an arbitrary real number, the coordinates of m2 are as follows.
x = t × qx
y = −1y + t × (qy + 1y)
z = t × qz (where −∞ <t <∞)
Consider a case where an error occurs at a measurement point as shown in FIG.
[0034]
At this time, the vector [m] exists between the moving point m1 on the vector [1x] and the moving point m2 on the vector [1y]. The coordinates of this vector [m] are as follows.
x = -1x + s * (px + 1x) -t * qx
y = s * py + 1y-t * (qy + 1y)
z = s * pz-t * qz
When there is no intersection between the vector [1x] and the vector [1y], the moving point m1 and the moving point m2 are closest to each other when the vector [m] is a common perpendicular to the vector [1x] and the vector [1y]. is there. The position of the target object is approximated to this point. In general, when there are two vectors [a] and [b],
[0035]
[Formula 6]

Because
[0036]
[Expression 7]

[0037]
From the above equation, if the point where the sum of the inner products is 0 is s = s0 and t = t0, the vectors [m10] and [m20] are
[M10] = (− 1x + s0 × (px + 1x), s0 × py, s0 × pz) [m20] = (t0 × qx, −1y + t0 × (qx + 1y), t0 × qz), and the middle point of the vector [m] Coordinates are
x = {− 1x + s0 × (px + 1x) + t0 × qx} / 2
y = {s0 * py-1y + t0 * (qy + 1y)} / 2
z = (s0 × pz + t0 × qz) / 2
It becomes.
Accordingly, if the distance in the X coordinate from P to Fx is SID, and the distance in the X coordinate from P to the midpoint of [m] is PID, the geometric magnification of the F side image is
[0038]
[Equation 8]

Similarly, the geometric magnification of the L side image is
[0039]
[Equation 9]

It becomes.
The above calculation is performed by the CPU 9, and the X-ray tube or I.D. I. Such positional information is obtained from the imaging support drive control device 14.
[0040]
【The invention's effect】
With the X-ray image diagnostic apparatus of the present invention, it is possible to obtain a highly accurate measurement value in consideration of the variation of the depth of the target object in quantitative analysis using an X-ray image.
[Brief description of the drawings]
1 is a configuration example of an X-ray diagnostic imaging apparatus according to the present invention. FIG. 2 is a processing flow of the X-ray diagnostic imaging apparatus according to the present invention. FIG. 3 is a measurement result of a vascular stenosis rate. Angiographic image [Fig. 5] Corresponding points specified on the angiographic images on both sides of F / L [Fig. 6] Flow of processing for calculating geometric magnification [Fig. 7] Cardiac volume measurement based on Simpson method [Fig. 8] Left and right ventricular contrast images on both sides of F / L [FIG. 9] Corresponding points designated on left ventricular contrast images on both sides of F / L [FIG. 10] Flow of processing for calculating geometric magnification [FIG. 11] Biplane imaging system [Fig. 12] Direction vector on both sides of F / L. [Fig. 13] Correction method using geometric enlargement ratio. [Fig. 14] Calculation method of blood vessel cross-sectional area in measurement of vascular stenosis rate. [Fig. Example of the object to be used
1 X-ray tube 2 Table 3 I.
4 TV camera 5 A / D converter 6 Frame memory 7 Image processing memory 8 Graphic memory drawing memory 9 CPU
DESCRIPTION OF SYMBOLS 10 Input device 11 Image synthesizer 12 D / A converter 13 Monitor 14 Imaging | photography support device drive control part 15 Subject

Claims (11)

Imaging means for imaging X-ray images from a plurality of directions with respect to a subject existing between the X-ray tube and the X-ray detector ;
Quantitative analysis means for performing blood vessel quantitative analysis of a diagnostic site of a subject from an X-ray image taken by the imaging means;
Corresponding point designating means for designating corresponding positions in the X-ray images taken from a plurality of directions, a distance between the X-ray tube and the subject at the corresponding points designated by the corresponding point designating means, and the subject Calculating means for calculating a geometric magnification calculated by a ratio of a distance between the detector and the detector ;
Correction means for correcting the result of quantitative analysis by the quantitative analysis means using the geometric magnification calculated by the calculation means;
An X-ray diagnostic imaging apparatus comprising: The X-ray image diagnosis apparatus according to claim 1, wherein the quantitative analysis unit measures a blood vessel diameter of the subject. The X-ray image diagnostic apparatus according to claim 1, wherein the quantitative analysis unit measures a stenosis rate of the subject. Imaging means for imaging X-ray images from a plurality of directions with respect to a subject existing between the X-ray tube and the X-ray detector ;
Quantitative analysis means for performing cardiac function quantitative analysis of a diagnostic site of a subject from an X-ray image taken by the imaging means;
Corresponding point designating means for designating corresponding positions in the X-ray images taken from a plurality of directions, a distance between the X-ray tube and the subject at the corresponding points designated by the corresponding point designating means, and the subject Calculating means for calculating a geometric magnification calculated by a ratio of a distance between the detector and the detector ;
Correction means for correcting the result of quantitative analysis by the quantitative analysis means using the geometric magnification calculated by the calculation means;
An X-ray diagnostic imaging apparatus comprising: The X-ray image diagnostic apparatus according to claim 4, wherein the quantitative analysis unit performs cardiac volume measurement of the subject. The X-ray diagnostic imaging apparatus according to claim 4, wherein the quantitative analysis unit measures a cardiac ejection fraction of the subject. The X-ray image diagnosis apparatus according to claim 1, wherein the imaging unit is provided so that X-ray images can be simultaneously acquired from two directions. The X-ray diagnostic imaging apparatus according to any one of claims 1 to 6, wherein the quantitative analysis means performs quantitative analysis of a diagnostic region of a subject from at least two images taken from directions perpendicular to each other. . 7. The X-ray diagnostic imaging apparatus according to claim 1, wherein the corresponding point designating unit designates corresponding points on at least two images taken from directions perpendicular to each other. The corresponding point specifying means specifies at least two corresponding points;
7. The correction unit according to claim 1, wherein the correction unit performs correction using a calculation result obtained by calculating a geometric enlargement factor other than the corresponding point specified by the corresponding point specifying unit by linear interpolation. X-ray diagnostic imaging apparatus according to claim 1 7. The calculation means according to claim 1, wherein the calculating means calculates a geometric enlargement ratio for each segment obtained by dividing the target object according to the corresponding points specified by the corresponding point specifying means. X-ray image diagnostic apparatus.

Images