JP2998362B2 - Measurement data correction method - Google Patents
Measurement data correction methodInfo
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- JP2998362B2 JP2998362B2 JP31208091A JP31208091A JP2998362B2 JP 2998362 B2 JP2998362 B2 JP 2998362B2 JP 31208091 A JP31208091 A JP 31208091A JP 31208091 A JP31208091 A JP 31208091A JP 2998362 B2 JP2998362 B2 JP 2998362B2
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- measurement
- correction
- detector
- radiation
- data
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Description
【０００１】[0001]
【産業上の利用分野】本発明は、医療用Ｘ線診断装置、
骨塩定量装置、非破壊検査装置、Ｘ線分析装置等に使用
される測定データの補正法に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a medical X-ray diagnostic apparatus,
The present invention relates to a method for correcting measurement data used in a bone mineral quantifying device, a nondestructive testing device, an X-ray analyzer, and the like.
【０００２】[0002]
【従来の技術】近年、放射線計測機器、特にγ線やＸ線
の２次元受像装置には、複数の検出素子で構成された放
射線検出器が用いられるようになった。2. Description of the Related Art In recent years, radiation detectors composed of a plurality of detection elements have been used for radiation measuring instruments, particularly two-dimensional image receiving apparatuses for γ-rays and X-rays.
【０００３】複数の放射線検出素子を用いた放射線計測
機器、特に複数の放射線検出素子を走査してＸ線やγ線
の２次元画像を受像する装置においては、検出器の感度
の素子間のばらつきや時間変化にともなう画像の不均一
性が問題となる。また、測定結果をもとに物質の定量を
行う装置においては、測定面内の精度にばらつきが生じ
る。[0003] In a radiation measuring device using a plurality of radiation detecting elements, in particular, in an apparatus for scanning a plurality of radiation detecting elements to receive a two-dimensional image of X-rays or γ-rays, variations in the sensitivity of the detector among the elements. And non-uniformity of the image due to a change with time. Further, in an apparatus for quantifying a substance based on a measurement result, the accuracy in a measurement plane varies.
【０００４】このため、一般に計測開始前に、素子間の
感度ばらつきを知るために、一度、実際の測定対象にち
かい校正用ファントムの計測を行い、その各検出素子素
子の放射線強度を示す値から、演算装置により素子間の
補正係数を得る。これにより、素子間における検出素子
の感度ばらつきは補正され、素子間のばらつきによる画
像の不均一性は解消される。Therefore, in general, before starting the measurement, in order to know the sensitivity variation between the elements, a calibration phantom is once measured close to the actual measurement object, and the value indicating the radiation intensity of each detection element is obtained. , A correction coefficient between the elements is obtained by the arithmetic unit. Thereby, the sensitivity variation of the detection element between the elements is corrected, and the non-uniformity of the image due to the variation between the elements is eliminated.
【０００５】[0005]
【発明が解決しようとする課題】しかしながら上記の従
来の方法では、放射線の２次元画像を短時間に計測する
場合、検出素子を駆動する電圧の過渡変化などにより、
検出素子の感度が変動する。ＳｉやＣｄＴｅなどの半導
体検出器の場合、半導体表面に設けた電極に電圧を印加
して電界を発生させ、放射線より半導体内部に生じた電
荷を取り出し、放射線を検出する。電圧印加直後は、電
界が安定しないため、検出される誘導電流の大きさが変
化する。これにより、同じ強度の放射線を測定しても時
間的に測定値が変わる。このため、検出器の各素子の走
査方向に画像のむらが生じるという問題点を有してい
た。However, according to the above-mentioned conventional method, when a two-dimensional image of radiation is measured in a short time, a transient change in a voltage for driving a detection element causes a change.
The sensitivity of the detection element fluctuates. In the case of a semiconductor detector such as Si or CdTe, a voltage is applied to an electrode provided on a semiconductor surface to generate an electric field, and charges generated inside the semiconductor are extracted from radiation to detect radiation. Immediately after the voltage is applied, the magnitude of the detected induced current changes because the electric field is not stable. As a result, even if radiation of the same intensity is measured, the measured value changes over time. For this reason, there is a problem that image unevenness occurs in the scanning direction of each element of the detector.
【０００６】また、測定データを用いて計算処理を行い
物質の定量等を行う場合においても、測定面内での精度
にばらつきが生じるという問題を有していた。[0006] In addition, in the case of performing a calculation process using measurement data to quantify a substance or the like, there is a problem that the accuracy in the measurement plane varies.
【０００７】本発明は上記従来の問題点を解決するもの
で、放射線計測に感度ばらつきのない、すなわち画像に
むらのない計測方法を提供することを目的とする。An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a measurement method in which radiation measurement has no sensitivity variation, that is, an image is not uneven.
【０００８】[0008]
【課題を解決するための手段】この目的を達成するため
に本発明のデータ校正法では、検出素子間の感度ばらつ
きを補正するための補正測定をする際、同時に検出器の
時間変化を補正する補正係数を、補正測定により求めた
全データの平均値をある時間におけるすべての検出素子
の測定結果の平均値で除算して求める。この補正係数を
測定した放射線強度に乗算する。In order to achieve this object, in the data calibration method of the present invention, the time change of the detector is corrected at the same time as the correction measurement for correcting the sensitivity variation between the detection elements. The correction coefficient is obtained by dividing the average value of all data obtained by the correction measurement by the average value of the measurement results of all the detection elements at a certain time. The measured radiation intensity is multiplied by this correction coefficient.
【０００９】[0009]
【作用】これにより、測定対象を測定する前に一度、校
正用ファントムを測定することにより、検出素子間の感
度ばらつきと、検出素子の時間変化を補正する補正係数
を得ることができる。この補正係数を用いることによ
り、素子間および各素子の経時変化による測定画像の不
均一性を校正することができ、精度の高い画像計測を行
なうことができる。また、測定データを用いて計算処理
を行い物質の定量等を行う場合においても、測定面内で
の精度が向上する。Thus, by measuring the calibration phantom once before measuring the object to be measured, it is possible to obtain a correction coefficient for correcting variations in sensitivity between the detection elements and time changes of the detection elements. By using this correction coefficient, it is possible to calibrate the non-uniformity of the measured image due to the change over time between the elements and each element, and it is possible to perform highly accurate image measurement. In addition, in the case of performing a quantitative process or the like by performing a calculation process using the measurement data, the accuracy in the measurement plane is improved.
【００１０】[0010]
【実施例】以下本発明の一実施例について図面を参照し
ながら説明する。図１にＣｄＴｅ半導体検出器を用いた
Ｘ線受像装置の構成を示す。このＸ線受像装置は、Ｘ線
発生器２１、ＣｄＴｅ半導体検出器２２、測定データを
演算する演算装置２３と、データを記憶する記憶装置２
４と画像を表示する表示装置２５により構成される。Ｃ
ｄＴｅ半導体検出器２２は図２に示すように、１２８個
の検出素子が直線上に配列されて構成されている。Ｃｄ
Ｔｅ半導体検出器２２は、Ｘ線発生器２１と同期して走
査され、被写体２６のＸ線の２次元透過画像を撮影する
ことができる。走査の期間に１５０ラインのデータのサ
ンプリングが行なわれ、１２８ｘ１５０画素の２次元透
過画像が得られる。An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration of an X-ray image receiving apparatus using a CdTe semiconductor detector. The X-ray receiving apparatus includes an X-ray generator 21, a CdTe semiconductor detector 22, an arithmetic unit 23 for calculating measurement data, and a storage device 2 for storing data.
4 and a display device 25 for displaying an image. C
As shown in FIG. 2, the dTe semiconductor detector 22 includes 128 detection elements arranged in a straight line. Cd
The Te semiconductor detector 22 is scanned in synchronization with the X-ray generator 21 and can take a two-dimensional transmission image of the subject 26 with X-rays. During the scanning period, data of 150 lines is sampled, and a two-dimensional transmission image of 128 × 150 pixels is obtained.
【００１１】Ｘ線透過強度は、光子計数法により計測さ
れる。各々の検出素子において、Ｘ線との相互作用によ
り発生した電流パルスは、増幅器２７により増幅され、
カウンタ２８により計数される。この計数値を濃淡とし
て表示装置２５に表示することにより、２次元Ｘ線透過
画像が得られる。The X-ray transmission intensity is measured by a photon counting method. In each detection element, the current pulse generated by the interaction with the X-ray is amplified by the amplifier 27,
It is counted by the counter 28. By displaying the count value as light and shade on the display device 25, a two-dimensional X-ray transmission image can be obtained.
【００１２】被写体を測定する前に、まず図３に示すよ
うな補正用のファントムを測定する。この構成用ファン
トムは、測定対象とほぼ同じＸ線透過強度が得られるよ
うな材料で構成するのが望ましい。本実施例では、被写
体を人体である場合を想定し、減弱係数が人体の軟組織
に近い厚さ１５ｃｍのアクリルにより構成した。Before measuring a subject, a phantom for correction as shown in FIG. 3 is first measured. It is desirable that the phantom for configuration is made of a material that can obtain almost the same X-ray transmission intensity as the object to be measured. In the present embodiment, it is assumed that the subject is a human body, and the attenuation coefficient is made of acrylic having a thickness of 15 cm close to the soft tissue of the human body.
【００１３】２０番目の検出素子の測定結果を図４に示
す。図４より、一定の厚さのアクリルファントムを測定
したにもかかわらず、このカウント数は増加しており、
この検出素子の感度が変化していることがわかる。FIG. 4 shows the measurement results of the twentieth detection element. From FIG. 4, the count number has increased despite the measurement of the acrylic phantom having a constant thickness.
It can be seen that the sensitivity of the detection element has changed.
【００１４】この補正用ファントムの全測定データの平
均値ＡＶを演算装置により求めた。平均値ＡＶは１０６
３０カウントであった。An average value AV of all measured data of the correction phantom was obtained by an arithmetic unit. The average AV is 106
It was 30 counts.
【００１５】次に従来行なっていた素子間の感度ばらつ
きを補正するための補正係数を求める。各検出素子の補
正係数Ｃn（ｎ＝１〜１２８）は（数１）で求められ
る。Next, a correction coefficient for correcting sensitivity variation between elements, which has been conventionally performed, is obtained. The correction coefficient C n (n = 1 to 128) of each detection element is obtained by (Equation 1).
【００１６】[0016]
【数１】 (Equation 1)
【００１７】ただし、ＣＡＶnは各検出素子の１から１
５０サンプリングの１５０個のデータの平均値である。[0017] However, CAV n is from 1 of each detector element 1
It is an average value of 150 data of 50 samplings.
【００１８】さらに、各検出素子固有の感度の経時変化
を補正するための係数Ｌm（ｍ＝１〜１５０）を求め
る。Ｌmは、全データＡＶを各ラインにおける１２８個
の検出素子の平均ＬＡＶmで割った値とし（数２）で表
わされる。Further, a coefficient L m (m = 1 to 150) for correcting a change over time in the sensitivity unique to each detection element is obtained. L m is represented by all the data AV and divided by the average LAV m 128 detector elements in each line (the number 2).
【００１９】[0019]
【数２】 (Equation 2)
【００２０】図５に各ラインにおける１２８個の検出素
子の平均ＬＡＶmを、図６に（数２）にもとづき求めた
補正係数Ｌmを示す。[0020] The average LAV m 128 detector elements in each line in FIG. 5, showing a correction coefficient L m obtained based on the equation (2) in FIG.
【００２１】これらの補正係数Ｃn、Ｌmは演算装置で求
められ、記憶装置に記憶される。こののちに、被写体の
測定を行なった。測定した結果のｎ番目の検出素子のｍ
ラインのＸ線強度をＩmnとする。この測定結果にｎ補正
係数Ｃn、Ｌmを乗算して、経時変化と検出素子間のばら
つきを補正したデータＩ’mnを得る。各画素のデータは
（数３）のようになる。These correction coefficients C n and L m are obtained by an arithmetic unit and stored in a storage unit. After this, the subject was measured. M of the n-th detection element of the measurement result
Let the X-ray intensity of the line be I mn . This measurement result is multiplied by the n correction coefficients C n and L m to obtain data I ′ mn in which the change with time and the variation between the detection elements are corrected. The data of each pixel is as shown in (Equation 3).
【００２２】[0022]
【数３】 (Equation 3)
【００２３】この計算の結果、検出素子間の感度ばらつ
きや各検出素子の経時変化がほぼ一定であれば、各画素
の測定における感度の差はなくなる。As a result of this calculation, if the variation in sensitivity between the detection elements and the change with time of each detection element are substantially constant, there is no difference in sensitivity in the measurement of each pixel.
【００２４】図７に、２０番目の検出素子における補正
結果を示す。図４とくらべて、カウント数のライン方向
での変化が小さくなっており、補正の効果が見られる。FIG. 7 shows the correction result of the twentieth detection element. Compared to FIG. 4, the change in the count number in the line direction is smaller, and the effect of the correction is seen.
【００２５】以上のように、画素間の不均一性は解消さ
れ、均一な被写体を撮影した場合、むらの無い画像が得
られた。As described above, the non-uniformity between the pixels is eliminated, and when a uniform subject is photographed, a uniform image is obtained.
【００２６】なお、パルス波高を識別するディスクリミ
ネータを複数設け、パルス波高により、入射した放射線
のエネルギー帯ごとに計数する場合には、それぞれのエ
ネルギー帯毎に補正計数Ｌmを設けることにより、おの
おののエネルギー帯毎のカウント数の経時変化を補正す
ることができる。この２つのエネルギー帯のカウント数
を用いて、物質の定量を行う場合、測定面内の精度が向
上する。When a plurality of discriminators for discriminating the pulse wave height are provided and counting is performed for each energy band of the incident radiation based on the pulse wave height, a correction count Lm is provided for each energy band. It is possible to correct the change over time of the count number for each energy band. When a substance is quantified using the count numbers of these two energy bands, the accuracy in the measurement plane is improved.
【００２７】また、放射線検出器の走査速度がことなる
場合、すなわち１ラインあたりの測定時間がことなる場
合でも補正測定を行うことにより、容易に補正できる。Further, even when the scanning speed of the radiation detector is different, that is, when the measurement time per line is different, the correction can be easily performed by performing the correction measurement.
【００２８】本実施例では、放射線検出器をＣｄＴｅ半
導体放射線検出器としたが、Ｓｉ、Ｇｅ、ＨｇＩ2、Ｇ
ａＡｓなどを用いた半導体検出器やシンチレータを用い
た検出器や電離箱などの放射線検出器の補正方法として
も同様の効果が実現できるのは言うまでもない。In this embodiment, the radiation detector is a CdTe semiconductor radiation detector. However, Si, Ge, HgI 2 , G
It goes without saying that a similar effect can be realized as a correction method for a semiconductor detector using aAs or the like, a detector using a scintillator, or a radiation detector such as an ionization chamber.
【００２９】[0029]
【発明の効果】以上のように本発明は、補正測定におけ
るデータから、各検出素子の経時変化を補正する補正係
数をもとめ、この係数により測定データを補正すること
により、検出素子間の感度ばらつきを補正するのと同時
に、かつきわめて容易に検出素子の経時変化を補正し画
素間のばらつきのない画像を実現できるものである。As described above, according to the present invention, a correction coefficient for correcting a temporal change of each detection element is obtained from the data in the correction measurement, and the measurement data is corrected by the coefficient to obtain the sensitivity variation between the detection elements. Is corrected, and at the same time, it is possible to very easily correct the change over time of the detection element and realize an image without variation between pixels.
【図１】本発明の実施例におけるＸ線受像装置を示す図FIG. 1 is a diagram showing an X-ray image receiving apparatus according to an embodiment of the present invention.
【図２】本発明の実施例におけるＣｄＴｅ半導体検出器
を示す図FIG. 2 is a diagram showing a CdTe semiconductor detector according to an embodiment of the present invention.
【図３】本発明の実施例における補正用ファントムを示
す図FIG. 3 is a diagram showing a correction phantom according to the embodiment of the present invention.
【図４】本発明の実施例における補正計測結果を示す図FIG. 4 is a diagram showing a correction measurement result in the embodiment of the present invention.
【図５】本発明の実施例における補正測定結果のライン
方向変化の平均値を示す図FIG. 5 is a diagram illustrating an average value of a change in a line direction of a correction measurement result according to the embodiment of the present invention.
【図６】本発明の実施例において求められた補正係数を
示す図FIG. 6 is a diagram showing a correction coefficient obtained in an embodiment of the present invention.
【図７】本発明の実施例における補正結果を示す図FIG. 7 is a diagram showing a correction result in the embodiment of the present invention.
１ 補正用ファントム ２１ Ｘ線発生器 ２２ ＣｄＴｅ半導体検出器 ２３ 演算装置 ２４ 記憶装置 ２５ 表示装置 ２６ 被写体 ２７ ファンビームＸ線 ２８ 増幅器 ２９ カウンタ ３０ ＣｄＴｅ DESCRIPTION OF SYMBOLS 1 Correction phantom 21 X-ray generator 22 CdTe semiconductor detector 23 Computing device 24 Storage device 25 Display device 26 Subject 27 Fan beam X-ray 28 Amplifier 29 Counter 30 CdTe
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 平５−42130（ＪＰ，Ａ) 特開 平４−203995（ＪＰ，Ａ) 特開 昭62−75365（ＪＰ，Ａ) 特開 昭62−203075（ＪＰ，Ａ) (58)調査した分野(Int.Cl.7，ＤＢ名) G01T 1/24 G01T 1/164 G01T 7/00 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-42130 (JP, A) JP-A-4-203995 (JP, A) JP-A-62-75365 (JP, A) JP-A-62-75365 203075 (JP, A) (58) Fields investigated (Int. Cl. 7 , DB name) G01T 1/24 G01T 1/164 G01T 7/00
Claims (2)
射線検出器を走査して計測した放射線の測定データを補
正する方法であって、補正用ファントムを測定し、前記
校正用ファントムの測定データの全データの平均値をあ
る時間におけるすべての検出素子の測定データの平均値
で除算した値を補正係数とし、前記補正係数を被写体の
測定結果に乗算することにより、検出器の経時変化によ
る測定誤差を補正することを特徴とする測定データ補正
法。1. A method for compensating for radiation measurement data measured by scanning a radiation detector comprising a single or a plurality of detection elements.
A positive methods to measure the correction phantom, the
Oh the average value of all data of the measurement data of the calibration phantom
A value obtained by dividing by a mean value of the measurement data of all the detection elements at a certain time is used as a correction coefficient, and the correction coefficient is multiplied by the measurement result of the subject to correct a measurement error due to a temporal change of the detector. A method for correcting measured data.
であることを特徴とする請求項１記載の測定データ補正
法。2. The method according to claim 1, wherein the radiation detector is a CdTe semiconductor detector.
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|---|---|---|---|
| JP31208091A JP2998362B2 (en) | 1991-11-27 | 1991-11-27 | Measurement data correction method |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP31208091A JP2998362B2 (en) | 1991-11-27 | 1991-11-27 | Measurement data correction method |
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| Publication Number | Publication Date |
|---|---|
| JPH05150050A JPH05150050A (en) | 1993-06-18 |
| JP2998362B2 true JP2998362B2 (en) | 2000-01-11 |
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| JP4649874B2 (en) * | 2004-05-19 | 2011-03-16 | 株式会社島津製作所 | Radiation imaging device |
| JP4701890B2 (en) * | 2005-07-19 | 2011-06-15 | 株式会社島津製作所 | X-ray diagnostic equipment |
| US8941049B2 (en) * | 2010-07-30 | 2015-01-27 | Kla-Tencor Corporation | Readout methodology for multi-channel acquisition of spatially distributed signal |
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1991
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| JPH05150050A (en) | 1993-06-18 |
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