JP2004007340A - Radiation image reading device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiation image reading device which can detect an exact position of a stimulable phospher plate at a low cost. <P>SOLUTION: The reading device can read regions including the all stimulable phospher plate and comprises a plate region determining means 205 which detects an end part of the stimulable phospher plate from an image signal read by a reading means and determines a position of the stimulable phospher plate, and a plate region extracting means 207 which cuts out an image recorded in the stimulable phospher plate from the image signal read by the reading means based on the position of the stimulable phospher plate determined by a plate region determining means 201. <P>COPYRIGHT: (C)2004,JPO

Description

【００９２】
ここでＰｘ，ｙは、水平座標ｘ，垂直座標ｙである画素の画素信号値を表す。また、ｋの値は、プレート内領域からプレート外領域への移行部分での信号変化を正確に捉えられるよう、上記各式の右辺第１項がプレート内領域の信号和、右辺第２項がプレート外領域の信号和となることが可能で、かつできるだけ小さな値であることが望ましく、実距離にして０．２ｍｍから０．５ｍｍ程度であることが望ましい。
【００９３】
さらに、差分信号値を求める際、ノイズ等の影響で誤った画素を検出しないよう、４画素乃至１６画素程度の信号値の和同士で差分信号値を求めることが望ましい。
【００９４】
次に、もとめた垂直方向、水平方向の差分信号値毎に、所定の閾値Ｔｈｄ１との比較を行う。そして所定の閾値以上の差分信号値を有する画素を検出する。所定の閾値Ｔｈｄ１の値は、１画素当たりの差分信号値が、信号強度の対数比で０．１〜０．２程度とすることが望ましい。０．１より小さな値では、誤ったプレート端部情報を検出してしまう可能性が高くなり、逆に０．２より大きな値では、プレート端部の信号変化を捉えられないおそれが高くなる。
【００９５】
検出結果は、２次元配列Ｃ［ｘ］［ｙ］を用いて表す。検出された画素の水平座標をｍ、垂直座標をｎとすると、２次元配列Ｃ［ｘ］［ｙ］の要素Ｃ［ｍ］［ｎ］の値を’１’とし、それ以外の要素の値を’０’とする。
【００９６】
次に、検出された画素の数を垂直方向、水平方向の各座標値毎に集計する。集計結果は、Ｓｔ，Ｓｂ，Ｓｌ，Ｓｒ毎に、それぞれＤｔ［ｙ］，Ｄｂ［ｙ］，Ｄｌ［ｘ］，Ｄｒ［ｘ］に記憶する。
ここでｘ，ｙはそれぞれ水平座標値、垂直座標値を表す変数である。
【００９７】
Ｄｔ［ｙ］，Ｄｂ［ｙ］，Ｄｌ［ｘ］，Ｄｒ［ｘ］の集計値を座標値毎に調べていくと、プレート端が存在する付近でその集計値は、大きな値になると考えられる。
そこでＤｔ［ｙ］，Ｄｂ［ｙ］，Ｄｌ［ｘ］，Ｄｒ［ｘ］毎に集計値が最も大きい座標値Ｙｔ１，Ｙｂ１，Ｘｌ１，Ｘｒ１を求める。
【００９８】
これらがプレート端の上下左右の各端位置の第１候補となる。
次に、上記第１の候補を除き、それぞれの集計結果毎に次に集計値の大きな座標を第２の候補Ｙｔ２，Ｙｂ２，Ｘｌ２，Ｘｒ２とする。ただし、上記第１の候補と、第２の候補との距離が近すぎる場合、第１の候補から第２の候補までの間の座標値において、上記集計値が単調減少する場合は、候補としない。
【００９９】
これは、プレートが理想的な配置に対して斜めに傾いて配置され、読み取りが行われた場合、特定の座標だけでなく、その周辺も集計値が大きくなるため、実質的に同一の候補を異なる候補として検出することを避けるためである。
【０１００】
同様に、第３以降の候補も求める。候補の数は、真のプレート端を必ず候補の中に含めることができ、かつ照射野端等の偽の候補をできるだけ含めないよう、上下左右のプレート端毎に３〜５個程度が望ましい。
【０１０１】
また、座標値Ｙｔ１，Ｙｂ１，Ｘｌ１，Ｘｒ１等を求める際の集計値計算において、、誤差を吸収するため、連続する３〜５の座標値についての集計値を合計し、その最大値を持って比較することが望ましい。
【０１０２】
こうして得られたプレート端部候補Ｙｔｉ，Ｙｂｉ，Ｘｌｉ，Ｘｒｉ（ｉ＝１，２，．．，ｎ）、及びＣ［ｘ］［ｙ］が、プレート端部情報として、プレート位置決定手段２０３へ送信される。
（２）プレート位置決定手段
プレート位置決定手段２０３では、プレート端部情報及びプレートの形状等を利用して、真のプレート位置を決定する。また、プレート位置の決定方法には、幾つかの方法がある。
（２−１）プレート位置決定方法１
プレートの長さＬ、幅Ｗは、読み取り時点で予め判っている。
【０１０３】
そこで上記プレート端部候補のうち、真のプレート端は以下の条件を満たすはずである。
Ｙｂｊ　−　Ｙｔｋ　＝　Ｌ　（１≦ｊ≦ｎ，　１≦ｋ≦ｎ）　（５）
Ｘｒｖ　−　Ｘｌｕ　＝　Ｗ　（１≦ｖ≦ｎ，　１≦ｕ≦ｎ）　（６）
従って、プレート端部決定手段では、［Ｙｔｉ，Ｙｂｊ］の任意の組み合わせ、及び［Ｘｌｉ，Ｘｒｊ］の任意の組み合わせについて上記関係を満たすか否か調べ、上記関係を満たす組み合わせを検出する。
【０１０４】
なお、プレート端部候補取得時に誤差を含むこともあり得る。そこで、輝尽性蛍光体プレート１２の実際の大きさと、最終的に画像として出力する大きさとの関係から若干の余裕を見込むことが望ましい。例えば、輝尽性蛍光体プレート１２の長さが、最終的に出力する画像の実サイズより１ｍｍ長いなら、上記（５）（６）式の左辺と右辺の絶対値の差が、実距離の０．５ｍｍ未満となるときは、上記式を満たしているとことにする。
【０１０５】
検出された［Ｘｌｉ，Ｘｒｊ］、［Ｙｔｉ，Ｙｂｊ］で囲まれる領域として、プレート位置を決定することが出来る。
（２−２）プレート端部決定方法２
また、輝尽性蛍光体プレート１２の作成上の都合等により、プレートの角が厳密に直角ではなく、若干の丸みを帯びたり、プレートの角の一部が斜めに切り落とされたような形状になることがある。
【０１０６】
このようにプレートの一部に特有の形状が有れば、その形状に沿って、プレート端部を表すエッジ、即ちＣ［ｘ］［ｙ］　＝１となる画素が多数存在するか否かについて調べることにより、輝尽性蛍光体プレート１２の角を正確に認識し、そのプレート角の情報からプレート位置の決定を行うことができる。
【０１０７】
以下、輝尽性蛍光体プレート１２の角が円弧の形状になっている場合について説明する。
その場合、当該円弧に沿ってプレート端を表すエッジ、即ちＣ［ｘ］［ｙ］　＝１となる画素が存在するはずである。
【０１０８】
そこで、プレート端部候補の組み合わせに基づいて、プレート角の形状に合わせた円弧の形状を計算し、その円弧上にＣ［ｘ］［ｙ］　＝１となる画素が多数存在すれば、そのプレート端部候補の組み合わせは、真のプレート端を表していると考えられる。
【０１０９】
今、図２において左上端の角について考える。
例えば、輝尽性蛍光体プレート１２の角の丸みが、半径３ｍｍであり、読み取られた画像の画素サイズが０．１ｍｍとする。このとき左上端の角での円弧を表す形状の候補は、（Ｘｌｉ，Ｙｔｊ）の組み合わせより、以下の式で与えられる。
【０１１０】
（ｘ　−　Ｘｌｉ　−　３０）^２　＋　（ｙ　−　Ｙｔｊ　−　３０）^２＝　３０^２　（７）
ある組み合わせ（Ｘｌｕ，Ｙｔｋ）について、Ｘｌｕ≦　ｘ≦　Ｘｌｕ＋３０，　Ｙｔｋ≦　ｙ≦　Ｙｔｋ＋３０を満たす範囲で、上記方程式を満たす（ｘ，ｙ）の組み合わせについて、Ｃ［ｘ］［ｙ］　＝１を満たす画素が所定の閾値以上存在すれば、（Ｘｌｕ，Ｙｔｋ）が正しくプレートの左上端を表していると考えられる。このとき（Ｘｌｕ，Ｙｔｋ）の組み合わせをプレートの角を表す位置情報として抽出する。
【０１１１】
逆に、Ｃ［ｘ］［ｙ］　＝１満たす画素が所定の閾値まで達しなければ、別の（Ｘｌｉ，Ｙｔｊ）の組み合わせについて、同様のことを行う。
なお、上記所定の閾値は、円弧の半分の長さに相当する画素数から、３／４の長さに相当する画素数であることが望ましい。この範囲より閾値を低くすると、誤った組み合わせをプレート端部を表す情報として抽出する可能性が増大し、逆にこの範囲より閾値を高くすると、正しい組み合わせでも棄却してしまうおそれがある。
【０１１２】
また、Ｃ［ｘ］［ｙ］　＝１を満たす（ｘ，ｙ）について、任意の上式の左辺と右辺の差が、２画素未満に相当するときは、誤差を考慮して（７）式を満たすこととする。
上記と同様、輝尽性蛍光体プレート１２の他の角についても、それぞれ（Ｘｒｉ，Ｙｔｊ）、（Ｘｌｉ，Ｙｂｊ）、（Ｘｒｉ，Ｙｂｊ）の組み合わせについて調べることにより、輝尽性蛍光体プレート１２の４つの角の位置を決定することができる。
【０１１３】
また、輝尽性蛍光体プレート１２の大きさは予め判っているため、上記４つの角のうち、２点もとめることができれば、正しくプレート位置を決定することができる。
【０１１４】
さらに、メカニカルな精度等の条件により、読み取り時の輝尽性蛍光体プレート１２の配置において、輝尽性蛍光体プレート１２の傾きが無視してもよい程度にしか発生しないことが判っていれば、上記４つの角のうち、１点だけを求めることができれば、正しく輝尽性蛍光体プレート１２の位置を決定することができる。
【０１１５】
場合によっては、１乃至複数の輝尽性蛍光体プレート１２の角を誤検出したために、求めた輝尽性蛍光体プレート１２の４つの角が、輝尽性蛍光体プレート１２の形状、大きさを考慮すると整合性がとれないこともあり得る。
【０１１６】
そこでプレート位置決定手段２０３は、以下のような処理を行う。
求めることができた輝尽性蛍光体プレート１２の角同士を組み合わせ、整合性がとれるもの同士をまとめてグループを作り、各グループ毎に含まれる角を比較して、角の数が最も多いグループの情報だけを利用してプレート位置を決定する。
【０１１７】
もし、角の数が同数の場合は、読み取り時に輝尽性蛍光体プレート１２が理想的に配置された場合の読取画像上のプレート位置（左上端を（ｄ，ａ）とし、右下端を（Ｗ＋ｄ，Ｌ＋ａ）とする位置）に最も近いグループの情報を採用する。
【０１１８】
最終的に採用されたプレート角の情報だけを用いて、プレート位置を決定する。
具体的には、以下のように行う。
【０１１９】
▲１▼まず、左上の角と右下の角の水平座標、垂直座標について、上記（５）（６）式を満たすかどうか調査する。（５）（６）式を満たす場合、両角は整合性がとれており、この場合はこの両角だけで輝尽性蛍光体プレート１２の外縁を完全に特定できるため、処理を終了する。
【０１２０】
▲２▼左上または右下の角のどちらかが検出できない場合、及び左上の角と右下の角の水平座標、垂直座標が（５）（６）式を満たさない場合、右上の角と左下の角の水平座標、垂直座標について、上記（５）（６）式を満たすかどうか調査する。（５）（６）式を満たす場合、両角は整合性がとれており、この場合はこの両角だけでプレートの外縁を完全に特定できるため、処理を終了する。
【０１２１】
▲３▼▲１▼，▲２▼で処理が終了しない場合、左上および左下の角の垂直座標から、（５）式を満たすか否か調べる。また水平座標の差が、メカニカルな精度から発生する可能性があると見込まれるズレ量以下であるかどうか確認する。（５）式を満たし、かつ水平座標のズレ量が所定の条件を満たす場合、左上および左下の角をグループ化する。
【０１２２】
▲４▼▲３▼と同様に、右上および右下の角の垂直座標から、（５）式を満たすか否か調べる。また水平座標の差が、メカニカルな精度から発生する可能性があると見込まれるズレ量以下であるかどうか確認する。（５）式を満たし、かつ水平座標のズレ量が所定の条件を満たす場合、右上および右下の角をグループ化する。
【０１２３】
▲５▼▲３▼，▲４▼でグループ化を試みた結果を比較する。
左側、右側どちらかのグループ化ができなかった時は、グループ化できた方の角の情報だけを用いて、プレート位置を決定する。
【０１２４】
両方グループ化できた場合、輝尽性蛍光体プレート１２が理想的に配置された場合の読取画像上の位置と、各グループの位置との平均距離を求め、その絶対値について比較する。
【０１２５】
そして、絶対値が小さい方のグループの情報を用いて、プレート位置を決定する。
なお、上記平均距離は、輝尽性蛍光体プレート１２が理想的に配置された場合の読取画像上の位置における各角と、実際検出された角との対応する位置関係にあるもの同士で距離を求め、平均化することで求める。
【０１２６】
▲６▼左側、右側ともにグループ化できない場合、左上の角および右上の角でグループ化を試みる。この場合、左上の角と右上の角の水平座標が、（６）式を満たすか否か、および垂直座標の差が、メカニカルな精度から発生する可能性があると見込まれるズレ量以下であるかどうか確認する。（６）式を満たし、かつ垂直座標のズレ量が所定の条件を満たす場合、左上の角および右上の角をグループ化する。
【０１２７】
▲７▼同様に、左下の角および右下の角でグループ化を試みる。
▲８▼▲５▼と同様に、▲６▼，▲７▼でグループ化を試みた結果を比較する。
▲９▼▲８▼でもプレート位置を決定できない場合、検出できた各角毎に、プレートが理想的に配置された場合の読取画像上の位置と、各角の位置との平均距離を求め、その絶対値について比較する。そして最も平均距離の小さい角によりプレート位置を決定する。
【０１２８】
この場合、プレートは理想位置からの傾きは無いものとしてプレートの外縁を決定する。
（２−３）プレート位置決定方法３
実際の放射線撮影では、人体への不要な被曝を避けるため、また人体等を透過した際に、直進せず、散乱される放射線による画像への悪影響を避けるため、鉛板等でプレートの一部を遮って撮影されることがある。
【０１２９】
そのため、輝尽性蛍光体プレート１２の一部には放射線が届かず、一部のプレート端については、プレート端を示すエッジ画素が見つけられないこともある。そこで上記プレート位置決定方法１，２を組み合わせて使用することが望ましい。
【０１３０】
例えば、以下のような手順でプレートの位置を決定する。
まずプレート位置決定方法２により、輝尽性蛍光体プレート１２の４つの角の検出を試みる。
【０１３１】
そして、輝尽性蛍光体プレート１２の４角のうち、幾つかを検出することにより、プレート位置を決定できれば、そのまま処理を終了する。
もし、プレート位置を決定できないときは、プレート位置決定方法１によるプレートの位置決定を試みる。
【０１３２】
この方法により、プレートの位置を決定できれば、やはり処理を終了する。
プレート位置決定方法１によっても決定できないときは、プレート端部全体が鉛板等で遮蔽され、放射線がほとんど届かない場合と考えられるので、読取画像からプレート領域を切り出した位置が本来のプレート位置と若干ずれていても、実質何の問題も無いと考えられるため、理想的にプレートが配置された場合の画像上のプレート位置（左上端を（ｄ，ａ）とし、右下端を（Ｗ＋ｄ，Ｌ＋ａ）とする位置）をプレート位置とする。
【０１３３】
（３）プレート領域抽出手段
プレート領域抽出手段２０７では、読取画像から、プレート位置決定手段２０３により決定されたプレート位置に基づいてプレート領域を切り出し、最終的に得られる画像とする。
【０１３４】
出力画像の大きさは、輝尽性蛍光体プレート１２のサイズに関連して予め定められる。できる限り無駄な領域をなくすと共に、出力画像中にプレート外領域が含まれることを防ぐために、輝尽性蛍光体プレート１２に収まるぎりぎりのサイズである。例えば、輝尽性蛍光体プレート１２に対し、出力画像は垂直方向、水平方向とも１〜３ｍｍ程度だけ小さいサイズである。
【０１３５】
輝尽性蛍光体プレート１２のいくつかの角が検出できたことにより、プレート領域を特定できる場合は、プレート領域を特定する角を出力画像の該当する角になるように、読み取り画像から切り出す。例えば、輝尽性蛍光体プレート１２の左上の角からプレート領域を特定できる場合、出力画像はこの角を出力画像の左上端とするように切り出す。この時、輝尽性蛍光体プレート１２のサイズと、出力画像のサイズとの差から発生する余有分を考慮し、出力画像ができるだけプレート領域内に収めるように、出力画像の切り出し位置を微調整する。例えば、上記余裕が水平方向、垂直方向とも２ｍｍの場合には、上下左右均等に余裕ができるよう、検出された輝尽性蛍光体プレート１２の左上の角から、１ｍｍ下方及び１ｍｍ右方へ移動した点を出力画像の左上端とする。
【０１３６】
このように余有分を考慮して切り出し位置を微調整することにより、読み取り画像に対してプレートが傾いた場合にも、出力画像中にプレート外領域の部分が含まれる可能性を減少させることができる。
【０１３７】
又、輝尽性蛍光体プレート１２の垂直方向及び水平方向のプレート端からプレート領域が特定できる場合には、プレート領域の上端を出力画像の上端とし、かつプレート領域の左端を出力画像の左端として、出力画像の切り出しを行なう。上記余裕分の考慮についても同様に行い、例えば、余裕が水平方向、垂直方向とも２ｍｍの場合には、検出されたプレート領域の上端から１ｍｍ下方に移動したところを出力画像の上端とし、プレート領域の左端から１ｍｍ右方に移動したところを出力画像の左端とする。
【０１３８】
（４）プレート領域外処理手段
プレート搬送時のバラツキ等により、読取画像に対してプレートが傾く場合がある。このような場合に、プレート領域以外の部分が含まれないように、出力画像もプレート領域の傾きにあわせて切り出すと、最終的な出力画像が矩形となるように整形するために、切り出した画像からアフィン変換を行なうことが必要となる。しかし、アフィン変換の実行には多くの計算資源又は処理時間を必要とするために、画像処理部６９全体にかかる負荷が大きくなりすぎ、現実的ではない。更に、アフィン変換を行なうことによりアーティファクトの発生も懸念される。従って、出力画像をプレート領域にあわせて傾けて切り出すことは現実的でない。
【０１３９】
そのため、傾きが大きい場合、図２３に示すように、読み取り画像中のプレート領域Ｐを正しく認識したとしても、最終的な出力画像Ｆの一部に、プレート外領域Ｏが含まれてしまう場合がある。
【０１４０】
一方、プレート外領域Ｏの部分に相当する画素では、輝尽発光を生じないため、当然低信号値となる。
ところで、放射線画像の読影の際には、放射線が強く当たったところほど、フィルム出力では高濃度、モニタ出力では低輝度になるような画像が通常用いられている。
【０１４１】
そうすると、上記プレート外領域Ｏは、フィルム出力では非常に低濃度、モニタ出力では高輝度となる。このような低濃度又は高輝度領域からは、多くの光が目に入るため、非常に眩しく、読影の支障になる。
【０１４２】
特に、高輝度のシャーカステンに、フィルムをかざして読影を行なうマンモグラフィー撮影では、悪影響が大きい。
そこで、万が一、最終的な出力画像Ｆの一部に、プレート外領域Ｏが含まれる場合には、そのプレート外領域Ｏの画素信号値を高濃度または低輝度化して、読影に支障がでないようにすることが望ましい。本実施の形態例では、画像処理部６９にプレート領域外処理手段２０９を設けている。
【０１４３】
このプレート領域外処理手段２０９は、前述したプレート端部決定方法２によりプレート角の認識を行なう。プレートの角を２点以上認識することができ、かつそれら認識されたプレート角の位置関係から、整合性が取れると判断されたプレート角が２点以上ある場合、プレートの形状が予め判っていることにより、読み取り画像に対する傾きも含めて、正確にプレート領域Ｐを決定できる。そこで、決定されたプレート領域以外の部分に含まれる画素の信号値を高濃度化又は低輝度化する。
【０１４４】
又、プレート外領域Ｏのすべてを高濃度化せず、一部だけ高濃度化することも可能である。例えば、マンモグラフィーでは、胸壁側プレートの上側にくるように撮影されているとすると、プレート上端より上側のプレート外領域のみ高濃度化するだけで、読影の支障をなくすという所定の目的を達成できるため、この部分の高濃度化のみを行なう、とういう選択もある。
【０１４５】
上記構成によれば、以下のような効果を得ることができる。
（１）読取手段は前記輝尽性蛍光体プレート１２全体を含む領域を読み取リ可能とし、読取手段で読み取った画像信号から輝尽性蛍光体プレート１２の端部を検出して、輝尽性蛍光体プレート１２の位置を決定するプレート領域決定手段２０５と、プレート領域決定手段２０５で決定された輝尽性蛍光体プレート１２の位置に基づいて、読取手段で読み取った画像信号から輝尽性蛍光体プレート１２に記録された画像を切り出すプレート領域抽出手段２０７とで構成することにより、プレート位置を検出する特別な機構が不要となり、低コストで輝尽性蛍光体プレートの正確な位置を検出することができる。
【０１４６】
（２）プレート端部情報取得手段２０１は、輝尽性蛍光体プレート１２の端部が含まれる可能性のある領域から、輝尽性蛍光体プレート１２の端部の複数候補を取得することにより、誤認識を減らすことができる。
【０１４７】
プレート位置決定手段２０３は、プレート端部情報取得手段２０１で取得した輝尽性蛍光体プレート１２の端部の複数候補、及び、予め判っている輝尽性蛍光体プレート１２の形状情報から、もっとも確からしい候補を輝尽性蛍光体プレート１２の端部とし、輝尽性蛍光体プレート１２の位置を決定することにより、精度よく輝尽性蛍光体プレートの位置を検出することができる。
【０１４８】
（３）プレート端部情報取得手段２０１は、近傍の画素間の信号変化から輝尽性蛍光体プレート１２の端部の複数候補を取得することにより、精度良く輝尽性蛍光体プレート１２の端部を検出することができる。
【０１４９】
（４）プレート領域外処理手段２０９は、読取手段で読み取った画像信号のうちで、プレート領域抽出手段２０７で切り出された出力画像に含まれる、プレート外領域の画素の信号値をあらかじめ指定した信号値に変換することで、読影に必要な情報のない画素を高濃度化又は低輝度化して読影者の眩惑を防止し、診断能の低下を防ぐことができる。
【０１５０】
尚、本発明は、上記実施の形態例に限定するものではない。上記実施の形態例では、装置に搭載された画像読み取り部が副走査方向に移動して読み取りを実行しているが、画像読み取り部自体は固定で、輝尽性蛍光体プレート１２が、画像読み取り部に対して移動しつつ、読み取りを行う場合でも、同様に実施することができる。
【０１５１】
この場合、輝尽性蛍光体プレート１２が所定位置まで搬送された時点を起点とし、その後一定時間経過後に読み取りを開始すればよい。起点位置は、例えば輝尽性蛍光体プレート１２をカセッテから引き出す動作を開始した瞬間や、輝尽性蛍光体プレートが画像読み取り部近傍の所定点に到達したとき等に設定することができる。
【０１５２】
また、プレート領域取得は、専用ハードウェアだけでなく、ソフトウェアでも実現可能である。
【０１５３】
【発明の効果】
以上述べたように請求項１記載の発明によれば、前記読取手段は前記輝尽性蛍光体プレート全体を含む領域を読み取リ可能とし、該読取手段で読み取った画像信号から前記輝尽性蛍光体プレートの端部を検出して、前記輝尽性蛍光体プレートの位置を決定するプレート領域決定手段と、該プレート領域決定手段で決定された前記輝尽性蛍光体プレートの位置に基づいて、前記読取手段で読み取った画像信号から前記輝尽性蛍光体プレートに記録された画像を切り出すプレート領域抽出手段とで構成することにより、プレート位置を検出する特別な機構が不要となり、低コストで輝尽性蛍光体プレートの正確な位置を検出することができる。
【０１５４】
請求項２記載の発明によれば、プレート端部情報取得手段は、前記輝尽性蛍光体プレートの端部が含まれる可能性のある領域から、前記輝尽性蛍光体プレートの端部の複数候補を取得することにより、誤認識を減らすことができる。
【０１５５】
プレート位置決定手段は、該プレート端部情報取得手段で取得した前記輝尽性蛍光体プレートの端部の複数候補、及び、予め判っている前記輝尽性蛍光体プレートの形状情報から、もっとも確からしい候補を前記輝尽性蛍光体プレートの端部とし、前記輝尽性蛍光体プレートの位置を決定することにより、精度よく輝尽性蛍光体プレートの位置を検出することができる。
【０１５６】
請求項３記載の発明によれば、プレート端部情報取得手段は、近傍の画素間の信号変化から前記輝尽性蛍光体プレートの端部の複数候補を取得することにより、精度良く輝尽性蛍光体プレートの端部を検出することができる。
【０１５７】
請求項４記載の発明によれば、前記読取手段で読み取った画像信号のうちで、前記プレート領域抽出手段で切り出された出力画像に含まれる、プレート外領域の画素の信号値をあらかじめ指定した信号値に変換することで、読影に必要な情報のない画素を高濃度化又は低輝度化して読影者の眩惑を防止し、診断能の低下を防ぐことができる。
【図面の簡単な説明】
【図１】画像処理部のブロック図である。
【図２】輝尽性蛍光体プレートを説明する図である。
【図３】放射線画像記録読取装置の斜視図でカセッテがセットされていない状態を示す図である。
【図４】カセッテがセットされた状態の放射線画像記録読取装置の正面図である。
【図５】図４における左側面図である。
【図６】図４における放射線画像記録読取装置の右側面図である。
【図７】放射線画像記録読取装置の概略構成を示す図である。
【図８】放射線画像記録読取装置の制御ブロック図である。
【図９】カセッテに放射線画像変換プレートを収納した状態を示す斜視図である。
【図１０】カセッテから放射線画像変換プレートを引き出した状態を示す斜視図である。
【図１１】カセッテの平面図である。
【図１２】カセッテに放射線画像変換プレートを収納した状態を示す平面図である。
【図１３】カセッテの側面図である。
【図１４】図１１の切断線Ｃ−Ｃにおける断面図である。
【図１５】図１１の切断線Ｄ−Ｄにおける断面図である。
【図１６】図１１の切断線Ｅ−Ｅにおける断面図である。
【図１７】プレート搬送部の構成を示す正面図である。
【図１８】図１７におけるカセッテクリンチの側面図である。
【図１９】カセッテクリンチの平面図である。
【図２０】副走査部の側面図である。
【図２１】画像読取部の光学系を示す図である。
【図２２】放射線画像読取装置の主要部の構成図である。
【図２３】出力画像に含まれるプレート外領域の説明図である。
【符号の説明】
６９　画像処理手段
２０１　プレート端部情報取得手段
２０３　プレート位置決定手段
２０５　プレート領域決定手段
２０７　プレート領域抽出手段
２０９　プレート領域外処理手段[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a radiation image reading apparatus that reads a radiation image by using stimulating light emitted from a stimulable phosphor plate provided on a substrate using a reading unit.
[0002]
[Prior art]
2. Description of the Related Art In recent years, devices capable of directly capturing a radiation image as a digital image have been developed. For example, in an apparatus that detects the amount of radiation applied to a subject and obtains a radiation image formed in accordance with the detected amount as an electric signal, a method using a detector using a stimulable phosphor is disclosed in -12429, JP-A-63-189853, JP-A-11-142997 and the like.
[0003]
In such an apparatus, the stimulable phosphor plate fixed to the stimulable phosphor plate by coating or vapor deposition on the sheet-like substrate is irradiated with radiation that has passed through the subject once, and the stimulable phosphor is irradiated with the radiation. Absorb. Thereafter, the stimulable phosphor is excited by light or heat energy, thereby radiating radiation energy-accumulated by the stimulable phosphor by the absorption, as fluorescence, and the fluorescence is photoelectrically converted to an image. Get the signal.
[0004]
As a specific method of reading an image signal from a plate coated with the stimulable phosphor or the like, there is a radiation image reading apparatus as shown in FIG. 22, for example.
The stimulable phosphor plate P is transported in the direction of arrow I. On the other hand, the excitation light emitted from the laser light source L is scanned through the polygon mirror PM and the reflection mirror M in a direction orthogonal to the transport direction (the direction of the arrow I) of the stimulable phosphor plate P.
[0005]
The stimulated emission generated from the portion irradiated with the excitation light is condensed by the condensing member GF, and is sequentially photoelectrically converted by the light receiving element ZS such as a photomultiplier to obtain an image signal.
[0006]
[Problems to be solved by the invention]
In the radiation image reading apparatus having the above configuration, in order to correctly read the image information recorded on the stimulable phosphor plate P, it is necessary to scan the entire stimulable phosphor plate P with the excitation light. It is.
[0007]
On the other hand, the timing of the stimulable phosphor plate P reaching the reading unit from the start of the conveyance, the stimulable fluorescent light to the reading unit (light collecting member GF, light receiving element ZS) depends on the transport accuracy of the stimulable phosphor plate P and the like. The position of the body plate P is not always constant. Further, when the stimulable phosphor plate P is fixed to the substrate, it is difficult to always fix the stimulable phosphor plate P at the same position due to a problem of manufacturing accuracy. May vary.
[0008]
Therefore, for example, JP-A-11-84551 and JP-A-2001-66719 disclose that a change in the excitation light is sensed using an optical sensor to detect the tip position of the stimulable phosphor plate being conveyed. The method described above makes it possible to accurately scan the stimulable phosphor plate using the detection result of the tip position.
[0009]
However, in this method, a special mechanism such as an optical sensor must be prepared in the reading unit to detect the position of the plate, which complicates the structure and increases the size and cost of the apparatus. In addition, in order to correctly detect the position of the stimulable phosphor plate in the direction perpendicular to the transport direction, a means for separately detecting the position in that direction may be prepared, or a position shift in such a direction may not occur. Therefore, it is necessary to improve the transfer accuracy of the apparatus.
[0010]
The present invention has been made in view of the above problems, and an object of the present invention is to provide a radiation image reading apparatus capable of detecting an accurate position of a stimulable phosphor plate at low cost.
[0011]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a radiation image reading apparatus for reading a radiation image using a stimulating light emitted from a stimulable phosphor plate provided on a substrate by using a reading means, wherein the reading means comprises: The area including the entire stimulable phosphor plate can be read, and the end of the stimulable phosphor plate is detected from the image signal read by the reading unit, and the position of the stimulable phosphor plate is detected. Plate area determining means for determining the position of the stimulable phosphor plate determined by the plate area determining means, the image signal read by the reading means is recorded on the stimulable phosphor plate And a plate area extracting means for cutting out the image.
[0012]
The reading means is capable of reading an area including the entire stimulable phosphor plate, detects an end of the stimulable phosphor plate from an image signal read by the reading means, and detects the end of the stimulable phosphor plate. Plate area determining means for determining the position of the body plate; and the stimulable phosphor based on the image signal read by the reading means based on the position of the stimulable phosphor plate determined by the plate area determining means. By using the plate area extracting means for cutting out the image recorded on the plate, a special mechanism for detecting the plate position becomes unnecessary, and the accurate position of the stimulable phosphor plate can be detected at low cost. .
[0013]
In the invention according to claim 2, the plate region determining means obtains a plurality of candidates for the end portion of the stimulable phosphor plate from a region that may include the end portion of the stimulable phosphor plate. Plate edge information acquisition means to be performed, a plurality of candidates for the edge of the stimulable phosphor plate acquired by the plate edge information acquisition means, and shape information of the stimulable phosphor plate known in advance. 2. The radiation image reading apparatus according to claim 1, wherein the most probable candidate is an end of said stimulable phosphor plate, and said plate position determining means determines a position of said stimulable phosphor plate. Device.
[0014]
The plate edge information obtaining means obtains a plurality of candidates for the edge of the stimulable phosphor plate from a region that may include the edge of the stimulable phosphor plate, thereby performing misrecognition. Can be reduced.
[0015]
The plate position determining means is the most reliable from a plurality of candidates for the end of the stimulable phosphor plate obtained by the plate end information obtaining means and the shape information of the stimulable phosphor plate known in advance. By determining a likely candidate as an end of the stimulable phosphor plate and determining the position of the stimulable phosphor plate, the position of the stimulable phosphor plate can be accurately detected.
[0016]
The invention according to claim 3 is characterized in that the plate edge information acquiring means acquires a plurality of candidates for the edge of the stimulable phosphor plate from a signal change between neighboring pixels. Is a radiation image reading apparatus.
[0017]
The plate edge information acquiring means detects the edge of the stimulable phosphor plate accurately by acquiring a plurality of candidates for the edge of the stimulable phosphor plate from a signal change between neighboring pixels. Can be.
[0018]
According to a fourth aspect of the present invention, in the image signal read by the reading unit, the signal value of a pixel in a region outside the plate included in the output image cut out by the plate region extracting unit is changed to a signal value designated in advance. The radiation image reading apparatus according to any one of claims 1 to 3, further comprising a processing unit outside the plate area for conversion.
[0019]
Of the image signals read by the reading means, the signal values of the pixels outside the plate area included in the output image cut out by the plate area extracting means are converted to signal values specified in advance, which are necessary for image reading. By increasing the density or lowering the luminance of pixels having no significant information, it is possible to prevent dazzling of the reader and prevent a decrease in diagnostic ability.
[0020]
Note that the "output image" refers to a final image cut out by the plate area extracting means.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, a radiation image reading apparatus according to an embodiment of the present invention will be described with reference to the drawings.
(Schematic configuration of radiation image recording and reading device)
(1) Overall flow
FIG. 7 is a diagram showing a schematic configuration of the radiation image recording and reading apparatus.
[0022]
The apparatus main body 2 of the radiation image recording and reading apparatus 1 includes a cassette stacker unit 3, a plate transport unit 4, an image reading unit 5, a system control unit 6, a display / operation unit 7, and a power supply unit 8.
[0023]
A cassette 9 containing a stimulable phosphor plate as a plurality of types of media can be set in the cassette stacker unit 3, and a cassette 9 containing a stimulable phosphor plate is loaded into the cassette stacker unit 3. I do. When a predetermined operation is performed from the display / operation unit 7, the stimulable phosphor plate 12 is pulled out of the cassette 9 by the plate transport unit 4.
[0024]
The drawn stimulable phosphor plate 12 is transported by the plate transport unit 4 toward the image reading unit 5. In the image reading section 5, the stimulable phosphor plate 12 is fixed, and reading by laser scanning is started. The stimulable phosphor plate 12 that has been read by the image reading unit 5 follows the same path and is stored in the original cassette 9. The erasing operation of the image on the stimulable phosphor plate 12 is performed by the erasing unit 13 when the image is stored in the cassette 9. That is, the image of the stimulable phosphor plate 12 is stored in the cassette 9 of the cassette stacker unit 3 while erasing the image.
[0025]
(2) Transfer of the stimulable phosphor plate to the reading unit
FIG. 8 is a control block diagram of the radiation image recording and reading apparatus.
The cassette stacker section 3 provided in the apparatus main body 2 of the radiation image recording and reading apparatus 1 includes a cassette stacker section mechanism / drive section 30 and a cassette stacker section control section 31 for accommodating a plurality of types of stimulable phosphor plates. The cassette 9 can be set.
[0026]
The cassette stacker unit mechanism / drive unit 30 is driven under the control of the cassette stacker unit control unit 31, and when the cassette 9 containing the stimulable phosphor plate is inserted, the cassette 9 is set to a predetermined state.
[0027]
The plate transport unit 4 includes a plate transport unit mechanism / drive unit 40 and a plate transport unit control unit 41. Based on a command from the cassette stacker unit control unit 31, the plate transport unit control unit 41 Controls the drive unit 40. The plate transport unit mechanism / drive unit 40 pulls out the stimulable phosphor plate 12 from the cassette 9 and transports the extracted stimulable phosphor plate 12 toward the image reading unit 5.
[0028]
(3) Plate reading and image acquisition
The image reading unit 5 includes a sub-scanning unit mechanism / drive unit 50 and a main scanning unit 51. The main scanning unit 51 is transported in the sub-scanning direction by the sub-scanning unit mechanism / drive unit 50. Image reading by laser scanning is performed.
[0029]
The system control unit 6 includes a main CPU 60 and a reading / image input control unit 61. The main CPU 60 is connected with a system disk 62 storing a system program, image disks 63 and 64 storing image information, and is connected via a board 65 to a host computer 66, a diagnostic device 67 and a patient registration terminal 68. You. The main CPU 60 performs overall control, image processing, output control, and image management. The reading / image input control unit 61 controls the cassette stacker unit control unit 31, the sub-scanning unit mechanism / drive unit 50, and the main scanning unit 51 to read an image of the stimulable phosphor plate 12, and reads this image information. The image is sent to the image processing unit 69.
[0030]
The display / operation unit 7 includes a CRT 70 as a display unit that displays an image read by the image reading unit 5, and a touch panel 71 as an operation unit provided on a display screen of the CRT 70. Is transmitted to the main CPU 60, and the main CPU 60 performs control based on the input command.
[0031]
4) Plate area acquisition
The image processing section 69 detects the position of the plate from the read image, and cuts out only an area corresponding to the plate area to obtain a final output image. Subsequent image processing, image output, and image storage are performed on the finally acquired image.
[0032]
The means for cutting out the plate area includes a plate edge information obtaining means, a plate position determining means, and a plate area extracting means. The plate edge information acquiring means acquires a plurality of pieces of position information on the read image in which the plate edge is considered to exist as plate edge information, limited to an area rationally considered to include the plate edge. I do. Then, based on the plate edge information, the plate position determining means determines the plate position on the read image, and according to the position, the plate area is cut out by the plate area extracting means in accordance with the outer edge shape of the plate, and the final output Get image information.
(Detailed description of each part of the radiation image recording and reading device)
(1) Appearance shape
The external shape of the radiation image recording and reading apparatus will be described. 3 is a perspective view of the radiation image recording / reading apparatus, showing a state where a cassette is not set, FIG. 4 is a front view of the radiation image recording / reading apparatus with a cassette set, and FIG. 5 is a left side view in FIG. FIG. 6 and FIG. 6 are right side views of the radiation image recording and reading apparatus in FIG.
[0033]
The cassette stacker unit 3 and the display / operation unit 7 are arranged substantially horizontally in the upper part of the radiation image recording and reading apparatus. That is, the cassette stacker unit 3 is disposed on the upper right side of the radiation image recording and reading apparatus 1, and the display / operation unit 7 is disposed on the upper left side of the radiation image recording and reading apparatus.
[0034]
The cassette stacker unit 3 has a loading unit 300 provided for every five slots. The display / operation unit 7 includes a CRT 70 as a display unit, and a touch panel 71 as an operation unit provided on the display surface of the CRT 70. Operations such as examination reservation, patient registration, etc. The status display / setting and the display of the read image are performed.
[0035]
As the CRT 70, for example, a 15-inch CRT (24-bit color, monochrome 256 gradations, resolution 1024 × 768) is used, and operation input is performed by the touch panel 71 on the CRT 70.
[0036]
The touch panel 71 of the present embodiment is of an optical type that reacts by blocking light, for example, infrared rays. The input section 300 includes an input guide section 301 and a storage section 302. The introduction guide portion 301 extends in a groove shape toward the storage portion 302, and is formed so as to guide the cassette 9 to the storage portion 302 in a vertical state. The cassette 9 is stored and held in the storage section 302 with a predetermined gap.
[0037]
The cassette 9 is a vertically inserted state in which the cassette long side direction is horizontal and the front side of the apparatus is used as a reference. At the same time as the cassette 9 is inserted, the light-shielding shutter 303 provided in the opening of the storage section 302 is provided for each slot. Close and prevent light leakage from openings.
[0038]
The cassette 9 can be pulled out for each slot, and an LED lamp 304 indicating reading is provided so that the cassette 9 is not accidentally pulled out.
(2) Cassette
Hereinafter, the cassette 9 used in the radiation image recording and reading apparatus 1 will be described in detail.
[0039]
The cassette housing the stimulable phosphor plate is configured as shown in FIGS. 9 is a perspective view showing a state in which a stimulable phosphor plate is housed in a cassette, FIG. 10 is a perspective view showing a state in which a stimulable phosphor plate is pulled out of the cassette, FIG. 11 is a plan view of the cassette, and FIG. 11 is a plan view showing a state in which the stimulable phosphor plate is housed in the cassette, FIG. 11 is a side view of the cassette, FIG. 14 is a cross-sectional view taken along section line CC of FIG. 11, and FIG. 15 is a section line D of FIG. FIG. 16 is a sectional view taken along section line EE in FIG. 11.
[0040]
The cassette 9 is integrated by fastening the case halves 900 and 901 together and fastening the periphery with screws 902. An opening 903 is formed on one side of the cassette 9, and the stimulable phosphor plate 12 can be pulled out from the opening 903.
[0041]
The radiation image conversion plate 12 has a stimulable phosphor layer, and the stimulable phosphor layer accumulates energy according to the radiation transmittance distribution of the subject with respect to the amount of irradiation radiation from the radiation source to form a latent image. To form The radiation image conversion plate 12 is provided with a stimulable phosphor layer by vapor deposition or coating. The stimulable phosphor layer is shielded or covered with a protective member in order to prevent adverse effects and damage due to the environment. As a material of the radiation image conversion plate, for example, M ^I X ・ aM ^II X ' ₂ ・ BM ^III X " ₃ : Alkaline hydride phosphor represented by cA (provided that M ^I Represents at least one kind of alkali metal of Li, Na, K, Rb and Cs; ^II Represents at least one divalent metal of Be, Mg, Ca, Sr, Ba, Zn, Cd, Cu and Ni; ^III Represents at least one trivalent metal of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Al, Ga, and In. X, X ′, X ″ represent at least one halogen of F, Cl, Br, I, and X, X ′, X ″ represent Eu, Tb, Ce, Tm, Dy, Pr, Ho. , Nd, Yb, Er, Gd, Lu, Sm, Y, Tl, Na, Ag, Cu, and Mg, wherein a, b, and c are 0 ≦ a <0.5, 0 ≦ It represents a number that satisfies b <0.5 and 0 <c ≦ 0.2. Also, for example, (Ba) _1-xy Mg _x Ca _y ) FX: eEu ²⁺ (Where X is at least one of Br and Cl, x, y and e are respectively 0 <x + y <0.6, xy ≠ 0, 10 ^-6 ≦ e ≦ 5 × 10 ^-2 It is a number that satisfies the following condition. ) Or BaFX: xCe, yA (where X is at least one of ClBr and I, and A is In, Tl, Gd, Sm And Zn, and x and y are each 0 <x ≦ 2 × 10 ^-1 And 0 <y <5 × 10 ^-2 It is. The phosphor BaBr: Eu represented by) ²⁺ And the like indicated by.
[0042]
The stimulable phosphor plate 12 is fixed to a rigid tray (substrate) 904 inside the cassette 9, and a pair of locking pins 905 are provided on the tray 904 corresponding to portions other than an area where an image is recorded. The pair of locking pins 905 pass through the tray 904 of the stimulable phosphor plate 12. A guide hole 906a of a guide plate 906 is slidably provided on the pair of locking pins 905, and a cap 907 that covers an opening of the guide plate 906 is attached.
[0043]
A lock mechanism 908 is built in the cap 907, and the lock of the lock mechanism 908 can be released from the lock hole 909. The cap 907 is provided with a pair of levers 910, and the cap 907 is opened and closed by the pair of levers 910, and the stimulable phosphor plate 12 together with the tray 904 is pulled out from the cassette 9 or stored.
[0044]
An identification label 911 is affixed to the cassette 9, identification information in white and black is recorded on the identification label 911, and the type and size of the cassette 9 can be detected by detecting the identification information of the identification label 911. Erroneous insertion into the cassette stacker unit 3 is detected.
[0045]
Also, the identification direction of the cassette 9 and the front and back sides are determined by the identification seal 911. The instruction in the vertical grid direction of the cassette 9 is indicated by the instruction mark 912 in the vertical direction. However, the vertical direction may be designated by inserting the cassette 9 into the cassette stacker unit 3 with the cap 907 on the lower side. .
[0046]
In the cassette 9, a medical record clip 913 is provided on the case half 900, and a concave portion 900 a is formed in the case half 900 around the medical record clip 913, and the medical record clip 913 is formed by the concave portion 900 a and the medical record clip 913. Medical records are kept.
[0047]
(3) Plate transport unit
17 is a front view showing the configuration of the plate transport unit, FIG. 18 is a side view of the cassette clinch in FIG. 17, and FIG. 19 is a plan view of the cassette clinch.
[0048]
The plate transport section 4 is the apparatus main body 2 of the radiation image recording and reading apparatus 1 and is disposed below the cassette stacker section 3, and the stimulable phosphor between the sub-scanning section 50 and the cassette position of the cassette stacker section 3. The plate 12 is transported.
[0049]
The rate transport section mechanism / drive section 40 provided in the plate transport section 4 is configured as shown in FIG. 4, FIG. 17 to FIG. That is, in the plate transport mechanism / drive unit 40, the support frame 400 is supported by guide rails 401 and 402 arranged vertically. The guide rails 401 and 402 are arranged in a direction orthogonal to the cassette 9 stored in the cassette stacker unit 3. The lower end of the support frame 400 is fixed to a transport belt 403 disposed below. The transport belt 403 is driven by a transport motor 404, whereby the support frame 400 moves along the guide rails 401 and 402.
[0050]
The erasing unit 13 is attached to the upper part of the support frame 400. As the erasing light source of the erasing section 13, for example, two 300 W halogen lamps (driving voltage 90 V) are used, and the moving speed of the stimulable phosphor plate 12 at the time of erasing is 10.5 mm / sec. It can be changed according to the image recording of the phosphor plate 12. The halogen lamp is an erasing light source, and turns on and irradiates the stimulable phosphor plate 12 with erasing light to erase an afterimage. The elimination of the afterimage is to irradiate the radiation image exchange plate 12 with erasing light, thereby releasing the residual radiation energy in the stimulable phosphor plate 12 after scanning and reading by the laser beam. Is provided with a guide shaft 410 in a vertical direction, and a cassette clinch 411 is attached to the guide shaft 410 so as to be movable in the vertical direction. The cassette linch 411 is attached to a transport belt 405 arranged vertically, and the transport belt 405 is driven by a transport motor 406 arranged below the support frame 400, whereby the cassette linch 411 moves along the guide shaft 410. Move up and down. The support frame 400 is provided with a holding roller 407 for preventing the stimulable phosphor plate 12 from falling down, and holds an end of the stimulable phosphor plate 12 outside the image recording area.
[0051]
As shown in FIG. 18, a pair of arms 413 are provided on the cassette lynch 411 in a support 412 so as to be rotatable about a support pin 414 as a fulcrum. Claws 413a provided at the tips of the pair of arms 413 can be engaged with a pair of levers 910 provided on the cap 907 of the cassette 9, and the bases 413b of the pair of arms 413 are always fixed by the springs 417. The cam 415 is urged to contact the pin 415a.
[0052]
The cam 415 is rotated by a drive motor 416. The pin 415a pushes the base 413b by the rotation of the cam 415, and the pair of arms 413 is opened and closed. The rotating shaft 420 of the driving motor 416 is provided with a rotating disk 421, and the notch 421 a formed in the rotating disk 421 detects the rotation angle of the driving motor 416 at the timing of crossing the photocoupler 422 to operate the pair of arms 413. Control.
[0053]
The support 412 of the cassette lynch 411 is provided with a pair of unlocking rods 430 for unlocking the lock mechanism 908 of the cap 907. The pair of unlocking rods 430 are slidably supported by a support 412 by a plate 431, and a solenoid 432 is connected to one of the unlocking rods 430, and the other unlocking rod 430 is unlocked by a connecting lever 433. It is connected to the rod 430 and operates in conjunction therewith.
[0054]
The pair of unlocking rods 430 is always urged to the initial position by the spring 434, and when the cassette 411 is moved upward, the support 412 is applied to the cap 907 of the cassette 9 to operate the solenoid 432. A pair of lock release rods 430 project and enter the lock holes 909 of the cap 907 to release the lock of the lock mechanism 908.
[0055]
When the lock mechanism 908 is unlocked, the pair of arms 413 is closed, and the claws 413a engage with the pair of levers 910 of the cap 907. In this state, the cassette lynch 411 is moved downward, and the stimulable fluorescent light is emitted from the cassette 9. The body plate 12 is pulled out, and the support frame 400 is moved and transported to the sub-scanning unit 50 while holding the stimulable phosphor plate 12 drawn out by the cassette lynch 411.
[0056]
When the image reading of the stimulable phosphor plate 12 is completed, the support frame 400 is moved in the opposite direction to return to a predetermined position, and the cassette lynch 411 is moved upward to store the stimulable phosphor plate 12 in the cassette 9. Let it. At this time, when the stimulable phosphor plate 12 is stored in the cassette 9 and the cap 907 is closed without operating the pair of unlocking rods 430, the lock mechanism 908 automatically locks the cap 907.
[0057]
(4) Image reading unit
FIG. 20 is a side view of the sub-scanning unit, and FIG. 21 is a diagram illustrating an optical system of the image reading unit.
(1) Sub-scanning mechanism / drive
The image reading section 5 is built in the apparatus main body 2 of the radiation image recording and reading apparatus 1 and is arranged below the display / operation section 7. The sub-scanning mechanism / drive unit 50 provided in the image reading unit 5 conveys the main scanning unit 51 in the sub-scanning direction.
[0058]
As shown in FIG. 4, FIG. 5, FIG. 20 and FIG. 21, the sub-scanning mechanism / drive unit 50 has a guide shaft 500 in a direction facing the stimulable phosphor plate 12 and a ball screw 501 arranged in parallel. ing. The guide shaft 500 is located above, and the ball screw 501 is located below. The main scanning unit 51 is held vertically by the guide shaft 500 and the ball screw 501, and can be moved horizontally.
[0059]
The ball screw 501 is provided with a direct drive motor 502, and the driving of the direct drive motor 502 rotates the ball screw 501 to move the main scanning unit 51 in the sub scanning direction.
[0060]
(2) Main scanning
As shown in FIGS. 20 and 21, the main scanning unit 51 integrally forms a laser beam generating unit 510, a polygon mirror 511, an fθ lens forming a condenser 512, a reflecting mirror 513, a light receiving unit 514, and the like. It is. The laser beam generator 510 includes a gas laser as a light source. It has a solid-state laser, a semiconductor laser, and the like. The laser beam generator 510 generates a laser beam whose emission intensity is controlled as excitation light.
[0061]
The laser beam reaches the polygon mirror 511 via the optical system, is deflected there, is condensed by the fθ lens constituting the condensing body 512, and is deflected in the optical path by the reflecting mirror 513 to exchange radiation images. The light is guided to the plate 12 as scanning light for stimulating excitation. An image is read by receiving photostimulated light emitted from the photostimulable phosphor plate 12 scanned by the laser beam by the light receiving unit 514. The light receiving unit 514 is configured by using a long photomultiplier 514a and a flat light collector 514b.
[0062]
The light enters the long photomultiplier 514a and is photoelectrically converted into an electric signal corresponding to the incident light. That is, the stimulated emission enters the long photomultiplier 514a through the flat light condensing body 514b and is photoelectrically converted, so that an output current corresponding to a radiation image is obtained. The output current from the long photomultiplier 514a is converted to a voltage signal by a current / voltage exchanger (not shown), amplified by an amplifier (not shown), and then converted to a digital image signal by an A / D converter. Then, the digital image signal is input to an image processing unit to be described later, where a plate area is obtained, and is stored as it is on an image disk or visualized by a CRT 70.
[0063]
Various kinds of synchronization signals from the polygon mirror 511 are input to the reading / image input control unit 61. The main scanning unit 51 is moved in the sub-scanning direction from the start position while being synchronized with the main scanning by the polygon mirror 511. Move at a predetermined speed.
[0064]
In this embodiment, a substantially perpendicular incidence method of irradiating the stimulable phosphor plate 12 with 5 ° with respect to the plate surface of the stimulable phosphor plate 12 is employed.
[0065]
The reading is started by the reading / image input control unit 61 at a point in time at which the main scanning unit 51 starts to convey, and then automatically started when a predetermined time has elapsed.
In addition, the scanning width of the laser beam is given some margin from the maximum width of the plate on which reading is performed in consideration of variations in the plate position, so that the entire plate can be reliably scanned even if the plate position varies. ing.
[0066]
5) System control unit
As shown in FIG. 8, the system control unit 6 includes a main CPU 60 and a reading / image input control unit 61, and is configured as follows.
[0067]
(1) System control unit The system control unit performs moiré removal and various corrections. It is used for image transfer with an image control board (ICU). XGA-24-bit color image display is possible.
[0068]
As a hard disk, a system disk 62 storing a system program and image disks 63 and 64 storing image information are connected. Image data output can be switched between host computer output priority and hard copy priority by user setting.
[0069]
(2) Image Data Storage The hard disks of the image disks 63 and 64 can be stored.
(3) Patient Registration As the input method of the patient, it is possible to input by the Japanese syllabary table displayed on the CRT 70, and usable character types are, for example, katakana and alphanumeric characters. In addition, it is also possible to automatically input an ID number. Furthermore, kanji can be input from the patient registration terminal.
[0070]
The unit of patient registration is performed in examination units. For example, up to 24 imagings per inspection are possible. Further, the number of reserved inspections can be, for example, up to 100 inspections.
(Plate area acquisition by image processing unit 69 of system control unit 6)
Next, plate area acquisition performed by the image processing unit 69 of the system control unit 6 will be described.
[0071]
The image processing unit 69 detects the position of the stimulable phosphor plate 12 from the read image, and cuts out only a region corresponding to the stimulable phosphor plate region to obtain a final output image.
[0072]
If the read image is used as it is, the size of the image becomes unnecessarily large, so that the processing speed such as image processing per image decreases, and the storage area required for storing the image increases. Because there is.
[0073]
Further, if the position of the stimulable phosphor plate 12 is not accurately detected, a part of the region where the subject is photographed is removed as the region outside the plate when cutting out the stimulable phosphor plate region. This is because there is a danger that they will be lost.
[0074]
Therefore, it is necessary to accurately recognize the position of the stimulable phosphor plate in the read image, and then to accurately cut out the plate region.
As shown in FIG. 1, the image processing unit 69 includes a plate area determining unit 205 including a plate edge information obtaining unit 201 and a plate position determining unit 203, a plate region extracting unit 207, and a plate area outside processing unit 209. .
[0075]
The image extraction of the stimulable phosphor plate 12 is performed as follows.
First, the plate edge information acquisition unit 201 detects some plate edge candidate information only in a limited area near the image edge where the plate edge of the stimulable phosphor plate 12 is considered to be included. The plate edge candidate information is obtained as coordinate values on the read image of the four corners of the plate or each side of the plate.
[0076]
Then, the plate position determining means 203 selects the most probable candidate information from the detected candidate information by using the shape of the stimulable phosphor plate 12, for example, the size of the plate, the shape of the corner, and the like. Is determined as the coordinates of the outer edge of the plate.
[0077]
Then, a region surrounded by the determined plate outer edge is set as a plate region, and cut out as an output image finally acquired by the plate region extracting unit 207.
The cut-out image is subjected to image processing such as gradation processing, and is stored as it is on an image disk, or is visualized by a CRT 70.
[0078]
Hereinafter, the operation of the image processing unit 69 will be described in detail.
(1) Edge information acquisition means 201
The information on the plate edge is obtained by the plate edge information acquisition means 201 as a parameter representing the position of each of the upper, lower, left, and right ends of the stimulable phosphor plate 12.
(1-1) Limited area
First, only an area reasonably considered to include the plate edge is transmitted to the edge information obtaining means 201.
[0079]
By limiting the area, it is possible to reduce erroneous recognition due to the structure of the subject shown in the image or the irradiation field edge. Further, since the area for performing the processing can be small, the time required for the processing can be reduced.
[0080]
The area that is reasonably considered to include the plate edge is considered in consideration of the distance between the position where the reading starts and the case where the plate is placed according to the design value, and the variations when transporting and fixing the plate. Is determined.
[0081]
Here, for convenience, as shown in FIG. 2, the transport direction of the main scanning unit 51 is the vertical direction of the image, the reading start point is the upper end of the image, and the reading end point is the lower end of the image. The vertical coordinate value at the upper end is set to 0, and the coordinate value increases as going downward.
[0082]
The direction in which scanning by the laser beam is performed is the horizontal direction of the image, the scanning start point is the left end of the image, and the scanning end point is the right end of the image. The horizontal coordinate at the left end is set to 0, and the coordinate value increases as going to the right.
[0083]
These coordinate values are expressed in units of pixels on the read image. When the coordinate values are displayed as (x, y) in two dimensions, x is a horizontal coordinate value and y is a vertical coordinate value.
Further, the size of the stimulable phosphor plate 12 on the read image is L in the unit of pixel in the transport direction of the main scanning unit 51, and is W in the unit of pixel in the scanning direction of the laser beam.
[0084]
Hereinafter, description will be made in accordance with the same rule.
i) Conveying direction (vertical direction) of main scanning unit 51
In the case where the stimulable phosphor plate 12 is arranged on the tray 904 according to the design value, the distance between the plate position and the reading start position is a, and a vertical position shift that may occur as a variation in the plate position. It is assumed that the quantity is b and the area width required for examining a signal change between neighboring pixels is c. The values of a, b, and c are set so as to satisfy the relationship a> b + c. For the sake of simplicity, the distance between the reading end position and the plate end when the stimulable phosphor plate 12 is arranged according to the design value is also set to a.
[0085]
In addition, c is a width necessary for calculating a difference signal value described below, and a maximum of about 20 pixels is sufficient even if a margin is taken into consideration.
At this time, the area where the edge information is obtained on the reading start side is limited to an area whose vertical coordinate value satisfies the condition of a− (b + c) to a + (b + c).
[0086]
Similarly, the area where the edge information is acquired on the reading end side is limited to an area where the vertical coordinate value satisfies the condition of a + L− (b + c) to a + L + (b + c).
ii) Laser beam scanning direction (horizontal direction)
When the stimulable phosphor plate 12 is arranged on the tray 904 according to the design value, the distance between the scanning start side plate edge and the scanning start point is d, and there is a possibility that the plate position varies. It is assumed that a certain amount of displacement in the horizontal direction is e. For simplicity, the distance between the scan end side plate edge and the scan end point when the plates are arranged as designed values is also d. Note that the values of d, e, and c are set so that the relationship of d> e + c holds in the same manner as described above.
[0087]
At this time, the area where the edge information is acquired on the scanning start side is limited to an area where the horizontal coordinate value satisfies the condition of d− (e + c) to d + (e + c).
Similarly, the area where the edge information is obtained on the scanning end side is limited to an area whose horizontal coordinate value satisfies the condition of d + W- (e + c) to d + W + (e + c).
(1-2) Acquisition of plate edge information
In a region outside the plate where no stimulable phosphor is present, no stimulable luminescence is generated ideally.
[0088]
Therefore, on the acquired read image, the signal value in the region outside the plate is low, and the signal value in the region inside the plate where the plate exists is high. Therefore, it is considered that pixels having a large difference signal value are concentrated near the plate edge.
[0089]
Therefore, the plate edge information acquisition means 201 calculates, for each pixel, a difference signal value obtained by subtracting the signal value of the pixel closer to the image edge from the pixel closer to the image center for each of the vertical and horizontal directions. Then, the coordinates at which pixels having large difference signal values are concentrated in the vertical direction and the horizontal direction are checked.
[0090]
First, the equation for calculating the difference signal value is given by the following equation.
[0091]
(Equation 1)

[0092]
Here, Px, y represents a pixel signal value of a pixel having a horizontal coordinate x and a vertical coordinate y. Further, the value of k is such that the first term on the right side of each of the above equations is the signal sum of the area within the plate, and the second term on the right side is that the signal change at the transition from the in-plate area to the out-of-plate area can be accurately captured. It is desirable that the sum of the signals in the area outside the plate can be obtained and that the value be as small as possible, and that the actual distance be about 0.2 mm to 0.5 mm.
[0093]
Further, when calculating the difference signal value, it is desirable to calculate the difference signal value from the sum of the signal values of about 4 to 16 pixels so as not to detect an erroneous pixel due to the influence of noise or the like.
[0094]
Next, a comparison with a predetermined threshold value Thd1 is performed for each of the determined difference signal values in the vertical and horizontal directions. Then, a pixel having a difference signal value equal to or larger than a predetermined threshold value is detected. It is desirable that the value of the predetermined threshold value Thd1 be such that the difference signal value per pixel is about 0.1 to 0.2 in logarithmic ratio of the signal intensity. If the value is smaller than 0.1, there is a high possibility that erroneous plate edge information will be detected. On the other hand, if the value is larger than 0.2, there is a high possibility that a signal change at the plate edge cannot be detected.
[0095]
The detection result is represented using a two-dimensional array C [x] [y]. Assuming that the horizontal coordinate of the detected pixel is m and the vertical coordinate is n, the value of the element C [m] [n] of the two-dimensional array C [x] [y] is “1”, and the values of the other elements are “1”. Is set to '0'.
[0096]
Next, the number of detected pixels is totaled for each coordinate value in the vertical and horizontal directions. The aggregation result is stored in Dt [y], Db [y], Dl [x], and Dr [x] for St, Sb, Sl, and Sr, respectively.
Here, x and y are variables representing a horizontal coordinate value and a vertical coordinate value, respectively.
[0097]
When the total value of Dt [y], Db [y], Dl [x], and Dr [x] is checked for each coordinate value, it is considered that the total value becomes large near the plate edge. .
Therefore, coordinate values Yt1, Yb1, X11, and Xr1 having the largest total value are obtained for each of Dt [y], Db [y], Dl [x], and Dr [x].
[0098]
These are the first candidates for the upper, lower, left, and right end positions of the plate end.
Next, except for the first candidate, the coordinates having the next largest tally value for each tally result are set as second candidates Yt2, Yb2, Xl2, and Xr2. However, if the distance between the first candidate and the second candidate is too short, and the coordinate value between the first candidate and the second candidate monotonically decreases in the coordinate value, the candidate is do not do.
[0099]
This is because when the plate is placed obliquely with respect to the ideal arrangement and the reading is performed, not only the specific coordinates but also the surrounding area becomes larger, so that substantially the same candidate is selected. This is to avoid detection as a different candidate.
[0100]
Similarly, third and subsequent candidates are obtained. The number of candidates is desirably about 3 to 5 for each of the upper, lower, left, and right plate edges so that a true plate edge can always be included in the candidates and a false candidate such as an irradiation field edge is not included as much as possible.
[0101]
In addition, in the calculation of the total value when calculating the coordinate values Yt1, Yb1, X11, Xr1, etc., in order to absorb an error, the total values of the continuous 3 to 5 coordinate values are summed, and the maximum value is obtained. It is desirable to compare.
[0102]
The thus obtained plate edge candidates Yti, Ybi, Xli, Xri (i = 1, 2,..., N) and C [x] [y] are sent to the plate position determining means 203 as plate edge information. Sent.
(2) Plate position determining means
The plate position determining means 203 determines the true plate position using the plate edge information, the shape of the plate, and the like. There are several methods for determining the plate position.
(2-1) Plate position determination method 1
The length L and width W of the plate are known at the time of reading.
[0103]
Therefore, of the above plate edge candidates, the true plate edge should satisfy the following conditions.
Ybj−Ytk = L (1 ≦ j ≦ n, 1 ≦ k ≦ n) (5)
Xrv−Xlu = W (1 ≦ v ≦ n, 1 ≦ u ≦ n) (6)
Therefore, the plate edge determining means checks whether or not any combination of [Yti, Ybj] and any combination of [Xli, Xrj] satisfy the above relation, and detects a combination satisfying the above relation.
[0104]
In addition, an error may be included at the time of obtaining a plate edge candidate. Therefore, it is desirable to allow some allowance from the relationship between the actual size of the stimulable phosphor plate 12 and the size finally output as an image. For example, if the length of the stimulable phosphor plate 12 is 1 mm longer than the actual size of the finally output image, the difference between the absolute values of the left and right sides of the above equations (5) and (6) is the actual distance. When it is less than 0.5 mm, it is determined that the above expression is satisfied.
[0105]
The plate position can be determined as an area surrounded by the detected [Xli, Xrj] and [Yti, Ybj].
(2-2) Plate edge determining method 2
Also, due to the convenience of the preparation of the stimulable phosphor plate 12, the corners of the plate are not strictly right angles, but are slightly rounded or have a shape in which some of the plate corners are cut off obliquely. It can be.
[0106]
If a part of the plate has a peculiar shape as described above, it is determined whether or not there are many edges along the shape, which represent the edge of the plate, that is, a pixel where C [x] [y] = 1. By checking, the corner of the stimulable phosphor plate 12 can be accurately recognized, and the plate position can be determined from the information of the plate angle.
[0107]
Hereinafter, a case where the corners of the stimulable phosphor plate 12 have an arc shape will be described.
In that case, there should be an edge representing the plate edge along the arc, that is, a pixel where C [x] [y] = 1.
[0108]
Therefore, based on the combination of the plate edge candidates, the shape of the arc matching the shape of the plate angle is calculated, and if a large number of pixels satisfying C [x] [y] = 1 exist on the arc, the plate is rejected. The combination of edge candidates is considered to represent a true plate edge.
[0109]
Now, consider the upper left corner in FIG.
For example, the corner of the stimulable phosphor plate 12 has a radius of 3 mm, and the pixel size of the read image is 0.1 mm. At this time, a shape candidate representing an arc at the upper left corner is given by the following equation based on the combination of (Xli, Ytj).
[0110]
(X-Xli-30) ² + (Y-Ytj-30) ² = 30 ² (7)
For a certain combination (Xlu, Ytk), a pixel satisfying C [x] [y] = 1 for a combination of (x, y) satisfying the above equation within a range satisfying Xlu ≦ x ≦ Xlu + 30, Ytk ≦ y ≦ Ytk + 30. Is present above a predetermined threshold, it is considered that (Xlu, Ytk) correctly represents the upper left corner of the plate. At this time, the combination of (Xlu, Ytk) is extracted as position information representing the corner of the plate.
[0111]
Conversely, if the number of pixels satisfying C [x] [y] = 1 does not reach the predetermined threshold value, the same operation is performed for another (Xli, Ytj) combination.
It is desirable that the predetermined threshold is a number of pixels corresponding to a length of 3/4 from a number of pixels corresponding to a half length of the arc. If the threshold is set lower than this range, the possibility of extracting an erroneous combination as information indicating a plate edge increases, and if the threshold is set higher than this range, a correct combination may be rejected.
[0112]
Further, for (x, y) satisfying C [x] [y] = 1, when the difference between the left side and the right side of any of the above equations corresponds to less than 2 pixels, the error is taken into account in equation (7). Shall be satisfied.
In the same manner as described above, the other corners of the stimulable phosphor plate 12 are also examined for combinations of (Xri, Ytj), (Xli, Ybj), and (Xri, Ybj), thereby obtaining the stimulable phosphor plate 12. Can be determined.
[0113]
In addition, since the size of the stimulable phosphor plate 12 is known in advance, if two points among the four corners can be determined, the plate position can be correctly determined.
[0114]
Further, if it is known that the inclination of the stimulable phosphor plate 12 occurs only to a negligible degree in the arrangement of the stimulable phosphor plate 12 at the time of reading due to conditions such as mechanical accuracy. If only one point among the four corners can be obtained, the position of the stimulable phosphor plate 12 can be correctly determined.
[0115]
In some cases, since the corners of one or more stimulable phosphor plates 12 are erroneously detected, the four corners of the stimulable phosphor plate 12 are determined by the shape and size of the stimulable phosphor plate 12. In consideration of the above, consistency may not be obtained.
[0116]
Therefore, the plate position determining means 203 performs the following processing.
Combine the corners of the stimulable phosphor plate 12 that were able to be obtained, combine the corners that are compatible with each other to form a group, compare the included corners of each group, and find the group with the largest number of corners. The position of the plate is determined using only the information of.
[0117]
If the number of corners is the same, the plate position on the read image when the stimulable phosphor plate 12 is ideally arranged at the time of reading (the upper left end is (d, a), and the lower right end is ( The information of the group closest to the position W + d, L + a) is adopted.
[0118]
The plate position is determined using only the finally adopted information on the plate angle.
Specifically, it is performed as follows.
[0119]
{Circle around (1)} First, it is checked whether the horizontal coordinates and the vertical coordinates of the upper left corner and the lower right corner satisfy the above equations (5) and (6). When the expressions (5) and (6) are satisfied, the two corners are consistent, and in this case, the outer edge of the stimulable phosphor plate 12 can be completely specified only by the two angles, and thus the processing is terminated.
[0120]
(2) If either the upper left corner or the lower right corner cannot be detected, or if the horizontal and vertical coordinates of the upper left corner and the lower right corner do not satisfy the equations (5) and (6), the upper right corner and the lower left corner It is checked whether the horizontal and vertical coordinates of the corner satisfy the expressions (5) and (6). When the expressions (5) and (6) are satisfied, the two corners are consistent. In this case, the outer edge of the plate can be completely specified only by the two angles, and thus the processing is terminated.
[0121]
If the processing is not completed in (3), (1) and (2), it is checked from the vertical coordinates of the upper left and lower left corners whether or not Expression (5) is satisfied. Also, it is checked whether or not the difference between the horizontal coordinates is equal to or less than a shift amount expected to possibly occur due to mechanical accuracy. If the expression (5) is satisfied and the amount of deviation of the horizontal coordinates satisfies a predetermined condition, the upper left and lower left corners are grouped.
[0122]
Similarly to (4) and (3), it is checked from the vertical coordinates of the upper right and lower right corners whether or not Expression (5) is satisfied. Also, it is checked whether or not the difference between the horizontal coordinates is equal to or less than a shift amount expected to possibly occur due to mechanical accuracy. When the expression (5) is satisfied and the amount of deviation of the horizontal coordinates satisfies a predetermined condition, the upper right and lower right corners are grouped.
[0123]
Compare the results of grouping attempts in (5), (3) and (4).
If either the left side or the right side cannot be grouped, the plate position is determined by using only the information of the corner that has been grouped.
[0124]
If both groups can be formed, the average distance between the position on the read image when the stimulable phosphor plate 12 is ideally arranged and the position of each group is determined, and the absolute values are compared.
[0125]
Then, the plate position is determined using the information of the group having the smaller absolute value.
Note that the average distance is a distance between each corner at a position on the read image when the stimulable phosphor plate 12 is ideally arranged, and those corresponding to the actually detected corners. Is calculated and averaged.
[0126]
{Circle around (6)} When the left and right sides cannot be grouped, the grouping is attempted at the upper left corner and the upper right corner. In this case, whether the horizontal coordinates of the upper left corner and the upper right corner satisfy Expression (6), and the difference between the vertical coordinates is equal to or less than a shift amount that is likely to occur due to mechanical accuracy. Check if it is. When the expression (6) is satisfied and the deviation amount of the vertical coordinate satisfies a predetermined condition, the upper left corner and the upper right corner are grouped.
[0127]
{Circle around (7)} Similarly, grouping is attempted at the lower left corner and the lower right corner.
As in (8) and (5), the results of the grouping attempts in (6) and (7) are compared.
If the plate position cannot be determined even in (9) and (8), the average distance between the position on the read image when the plate is ideally arranged and the position of each corner is determined for each detected corner, The absolute value is compared. Then, the plate position is determined by the corner having the smallest average distance.
[0128]
In this case, the outer edge of the plate is determined assuming that the plate does not tilt from the ideal position.
(2-3) Plate position determination method 3
In actual radiation imaging, to avoid unnecessary exposure to the human body, and when passing through the human body, etc., do not go straight and avoid adverse effects on the image due to scattered radiation. May be taken out of the way.
[0129]
Therefore, radiation does not reach a part of the stimulable phosphor plate 12, and an edge pixel indicating the plate edge may not be found for some of the plate edges. Therefore, it is desirable to use the plate position determining methods 1 and 2 in combination.
[0130]
For example, the position of the plate is determined by the following procedure.
First, detection of four corners of the stimulable phosphor plate 12 is attempted by the plate position determination method 2.
[0131]
Then, if the plate position can be determined by detecting some of the four corners of the stimulable phosphor plate 12, the process ends.
If the plate position cannot be determined, the position of the plate is determined by the plate position determination method 1.
[0132]
If the position of the plate can be determined by this method, the process is also terminated.
When it cannot be determined even by the plate position determination method 1, it is considered that the entire plate edge is shielded by a lead plate or the like and almost no radiation reaches the position. Therefore, the position where the plate area is cut out from the read image is the original plate position. Even if there is a slight deviation, it is considered that there is substantially no problem. Therefore, the plate position on the image when the plate is ideally arranged (the upper left end is (d, a), and the lower right end is (W + d, L + a ) Is the plate position.
[0133]
(3) Plate area extraction means
In the plate area extracting means 207, a plate area is cut out from the read image based on the plate position determined by the plate position determining means 203, and the image is finally obtained.
[0134]
The size of the output image is predetermined in relation to the size of the stimulable phosphor plate 12. The size is as small as possible to fit in the stimulable phosphor plate 12 in order to eliminate useless areas as much as possible and to prevent an out-of-plate area from being included in the output image. For example, the output image is smaller than the stimulable phosphor plate 12 by about 1 to 3 mm in both the vertical and horizontal directions.
[0135]
If the plate area can be specified by detecting some corners of the stimulable phosphor plate 12, the corner specifying the plate area is cut out from the read image so as to be the corresponding corner of the output image. For example, when the plate area can be specified from the upper left corner of the stimulable phosphor plate 12, the output image is cut out so that this corner is the upper left corner of the output image. At this time, in consideration of a margin generated from a difference between the size of the stimulable phosphor plate 12 and the size of the output image, the cutout position of the output image is finely adjusted so that the output image is included in the plate area as much as possible. adjust. For example, when the margin is 2 mm in both the horizontal direction and the vertical direction, the detected stimulable phosphor plate 12 is moved 1 mm downward and 1 mm rightward from the upper left corner of the detected stimulable phosphor plate 12 so that the margin is evenly distributed in the vertical and horizontal directions. This point is set as the upper left corner of the output image.
[0136]
By fine-tuning the cutout position in consideration of the surplus as described above, even if the plate is inclined with respect to the read image, it is possible to reduce the possibility that the output image includes a portion outside the plate in the output image. Can be.
[0137]
When the plate area can be specified from the vertical and horizontal plate ends of the stimulable phosphor plate 12, the upper end of the plate area is set as the upper end of the output image, and the left end of the plate area is set as the left end of the output image. Then, the output image is cut out. The above consideration of the margin is similarly performed. For example, when the margin is 2 mm in both the horizontal direction and the vertical direction, the position moved 1 mm below the upper end of the detected plate area is set as the upper end of the output image, and the plate area is determined. Is moved to the right by 1 mm from the left end of the output image.
[0138]
(4) Plate area outside processing means
The plate may be tilted with respect to the read image due to variations at the time of transporting the plate. In such a case, if the output image is also cut out according to the inclination of the plate area so that a portion other than the plate area is not included, the cut out image is formed in order to shape the final output image into a rectangle. It is necessary to perform an affine transformation from However, the execution of the affine transformation requires a lot of computational resources or processing time, so that the load on the entire image processing unit 69 becomes too large, which is not practical. Further, there is a concern that the occurrence of artifacts may be caused by performing the affine transformation. Therefore, it is not realistic to cut out the output image inclining according to the plate area.
[0139]
For this reason, when the inclination is large, as shown in FIG. 23, even if the plate area P in the read image is correctly recognized, a part of the final output image F may include the out-of-plate area O. is there.
[0140]
On the other hand, a pixel corresponding to the area O outside the plate does not emit photostimulated light, and therefore naturally has a low signal value.
By the way, when reading a radiation image, an image is generally used in which the higher the intensity of radiation, the higher the density of the film output and the lower the luminance of the monitor output.
[0141]
Then, the area O outside the plate has a very low density in the film output and a high luminance in the monitor output. From such a low-density or high-brightness region, a large amount of light enters the eyes, so that it is very dazzling and hinders image interpretation.
[0142]
In particular, mammography photography in which a film is held over a high-brightness Schaukasten for image reading has a large adverse effect.
Therefore, in the unlikely event that a part of the final output image F includes the out-of-plate region O, the pixel signal value of the out-of-plate region O is set to high density or low brightness so that the interpretation is not hindered. Is desirable. In the present embodiment, the image processing section 69 is provided with the plate area outside processing means 209.
[0143]
The plate area outside processing means 209 recognizes the plate angle by the above-described plate edge determination method 2. If two or more plate corners can be recognized, and if there are two or more plate angles determined to be consistent from the positional relationship between the recognized plate angles, the shape of the plate is known in advance. Thus, the plate area P can be accurately determined including the inclination with respect to the read image. Therefore, the signal values of the pixels included in the portion other than the determined plate region are increased in density or reduced in luminance.
[0144]
It is also possible to increase the concentration of only a part of the region O outside the plate without increasing the concentration. For example, in mammography, if the image is taken so as to be above the chest wall side plate, only the high density outside the plate above the upper end of the plate can achieve the predetermined purpose of eliminating the obstruction of image interpretation. There is also an option to only increase the density of this portion.
[0145]
According to the above configuration, the following effects can be obtained.
(1) The reading means makes it possible to read an area including the whole of the stimulable phosphor plate 12, detects the end of the stimulable phosphor plate 12 from the image signal read by the reading means, and Plate area determining means 205 for determining the position of the phosphor plate 12, and stimulable fluorescent light from the image signal read by the reading means based on the position of the stimulable phosphor plate 12 determined by the plate area determining means 205. By using the plate area extracting means 207 for cutting out the image recorded on the body plate 12, a special mechanism for detecting the plate position becomes unnecessary, and the accurate position of the stimulable phosphor plate can be detected at low cost. be able to.
[0146]
(2) The plate edge information acquiring means 201 acquires a plurality of candidates for the edge of the stimulable phosphor plate 12 from a region that may include the edge of the stimulable phosphor plate 12. , Can reduce false recognition.
[0147]
The plate position determining means 203 determines the most from the plurality of candidates for the end of the stimulable phosphor plate 12 acquired by the plate end information acquiring means 201 and the shape information of the stimulable phosphor plate 12 known in advance. By determining a probable candidate as the end of the stimulable phosphor plate 12 and determining the position of the stimulable phosphor plate 12, the position of the stimulable phosphor plate can be detected with high accuracy.
[0148]
(3) The plate edge information acquiring means 201 acquires the edge of the stimulable phosphor plate 12 with high accuracy by acquiring a plurality of candidates for the edge of the stimulable phosphor plate 12 from a signal change between neighboring pixels. Part can be detected.
[0149]
(4) The out-of-plate area processing unit 209 is a signal that specifies a signal value of a pixel in an out-of-plate area included in the output image cut out by the plate area extracting unit 207 among the image signals read by the reading unit. By converting the value into a value, pixels without information necessary for image interpretation can be increased in density or reduced in brightness to prevent dazzling of the image interpreter and prevent a decrease in diagnostic ability.
[0150]
Note that the present invention is not limited to the above embodiment. In the above embodiment, the image reading section mounted on the apparatus moves in the sub-scanning direction to execute reading, but the image reading section itself is fixed, and the stimulable phosphor plate 12 The same can be applied to the case where reading is performed while moving with respect to the unit.
[0151]
In this case, reading may be started after the stimulable phosphor plate 12 is conveyed to a predetermined position, and after a certain period of time has elapsed. The starting point position can be set, for example, at the moment when the operation of pulling out the stimulable phosphor plate 12 from the cassette or when the stimulable phosphor plate reaches a predetermined point near the image reading unit.
[0152]
Further, acquisition of the plate area can be realized not only by dedicated hardware but also by software.
[0153]
【The invention's effect】
As described above, according to the first aspect of the present invention, the reading unit can read an area including the entire stimulable phosphor plate, and reads the stimulable phosphor from the image signal read by the reading unit. Detecting the end of the body plate, a plate area determining means for determining the position of the stimulable phosphor plate, based on the position of the stimulable phosphor plate determined by the plate area determining means, A plate area extracting unit that cuts out an image recorded on the stimulable phosphor plate from the image signal read by the reading unit eliminates the need for a special mechanism for detecting the plate position, and reduces the luminance at low cost. The accurate position of the stimulable phosphor plate can be detected.
[0154]
According to the invention as set forth in claim 2, the plate edge information acquiring means is configured to detect a plurality of edges of the stimulable phosphor plate from a region that may include the edge of the stimulable phosphor plate. By obtaining candidates, erroneous recognition can be reduced.
[0155]
The plate position determining means is the most reliable from a plurality of candidates for the end of the stimulable phosphor plate obtained by the plate end information obtaining means and the shape information of the stimulable phosphor plate known in advance. By determining a likely candidate as an end of the stimulable phosphor plate and determining the position of the stimulable phosphor plate, the position of the stimulable phosphor plate can be accurately detected.
[0156]
According to the third aspect of the present invention, the plate edge information obtaining means obtains a plurality of candidates for the edge portion of the stimulable phosphor plate from a signal change between neighboring pixels, so that the stimulable phosphor plate has high stimulability. The end of the phosphor plate can be detected.
[0157]
According to the fourth aspect of the present invention, of the image signals read by the reading means, a signal in which a signal value of a pixel in a region outside the plate included in the output image cut out by the plate region extracting means is specified in advance. By converting the value into a value, pixels without information necessary for image interpretation can be increased in density or reduced in brightness to prevent dazzling of the image interpreter and prevent a decrease in diagnostic ability.
[Brief description of the drawings]
FIG. 1 is a block diagram of an image processing unit.
FIG. 2 is a diagram illustrating a stimulable phosphor plate.
FIG. 3 is a perspective view of the radiation image recording and reading apparatus, showing a state where a cassette is not set.
FIG. 4 is a front view of the radiation image recording and reading apparatus with a cassette set;
FIG. 5 is a left side view in FIG.
FIG. 6 is a right side view of the radiation image recording and reading apparatus in FIG. 4;
FIG. 7 is a diagram illustrating a schematic configuration of a radiation image recording and reading apparatus.
FIG. 8 is a control block diagram of the radiation image recording and reading apparatus.
FIG. 9 is a perspective view showing a state where the radiation image conversion plate is stored in the cassette.
FIG. 10 is a perspective view showing a state in which a radiation image conversion plate is pulled out of the cassette.
FIG. 11 is a plan view of the cassette.
FIG. 12 is a plan view showing a state where the radiation image conversion plate is stored in the cassette.
FIG. 13 is a side view of the cassette.
FIG. 14 is a sectional view taken along section line CC of FIG. 11;
FIG. 15 is a sectional view taken along section line DD in FIG. 11;
FIG. 16 is a sectional view taken along section line EE in FIG. 11;
FIG. 17 is a front view illustrating a configuration of a plate transport unit.
FIG. 18 is a side view of the cassette clinch shown in FIG. 17;
FIG. 19 is a plan view of the cassette lynch.
FIG. 20 is a side view of the sub-scanning unit.
FIG. 21 is a diagram illustrating an optical system of an image reading unit.
FIG. 22 is a configuration diagram of a main part of the radiation image reading apparatus.
FIG. 23 is an explanatory diagram of an out-of-plate area included in an output image.
[Explanation of symbols]
69 Image processing means
201 Plate edge information acquisition means
203 plate position determining means
205 plate area determining means
207 Plate area extraction means
209 Plate area outside processing means

Claims (4)

In a radiation image reading apparatus that reads a radiation image using a stimulating light emitted from a stimulable phosphor plate provided on a substrate using a reading unit,
The reading means is capable of reading a region including the entire stimulable phosphor plate,
Plate area determining means for detecting an end of the stimulable phosphor plate from the image signal read by the reading means and determining a position of the stimulable phosphor plate;
Plate area extracting means for cutting out an image recorded on the stimulable phosphor plate from an image signal read by the reading means based on the position of the stimulable phosphor plate determined by the plate area determining means; ,
A radiation image reading apparatus comprising: The plate area determining means,
Plate edge information acquisition means for acquiring a plurality of candidates for the edge of the stimulable phosphor plate from a region that may include the edge of the stimulable phosphor plate,
From the plurality of candidates for the end of the stimulable phosphor plate obtained by the plate end information obtaining means, and the shape information of the stimulable phosphor plate known in advance, the most probable candidate is the stimulable phosphor. Plate position determining means for determining the position of the stimulable phosphor plate as an end of the stimulable phosphor plate,
The radiation image reading device according to claim 1, wherein the radiation image reading device comprises: The plate edge information acquisition means,
3. The radiation image reading apparatus according to claim 2, wherein a plurality of candidates for an end portion of the stimulable phosphor plate are obtained from a signal change between neighboring pixels. Out of the image signals read by the reading means, included in the output image cut out by the plate area extraction means, a plate area outside processing means for converting the signal values of the pixels in the outside plate area into signal values designated in advance. The radiation image reading apparatus according to claim 1, further comprising:

Images