JP2939281B2 - X-ray CT system - Google Patents
X-ray CT systemInfo
- Publication number
- JP2939281B2 JP2939281B2 JP2004584A JP458490A JP2939281B2 JP 2939281 B2 JP2939281 B2 JP 2939281B2 JP 2004584 A JP2004584 A JP 2004584A JP 458490 A JP458490 A JP 458490A JP 2939281 B2 JP2939281 B2 JP 2939281B2
- Authority
- JP
- Japan
- Prior art keywords
- correction value
- ray
- attenuation
- subject
- value
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 238000012937 correction Methods 0.000 claims description 41
- 238000005259 measurement Methods 0.000 claims description 14
- 230000000007 visual effect Effects 0.000 claims description 8
- 230000001419 dependent effect Effects 0.000 claims description 2
- 230000035945 sensitivity Effects 0.000 description 15
- 238000010586 diagram Methods 0.000 description 13
- 238000012545 processing Methods 0.000 description 5
- 238000001514 detection method Methods 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 230000005855 radiation Effects 0.000 description 2
- 101100112083 Arabidopsis thaliana CRT1 gene Proteins 0.000 description 1
- 101100238301 Arabidopsis thaliana MORC1 gene Proteins 0.000 description 1
- 101100519629 Saccharomyces cerevisiae (strain ATCC 204508 / S288c) PEX2 gene Proteins 0.000 description 1
- 101100468521 Saccharomyces cerevisiae (strain ATCC 204508 / S288c) RFX1 gene Proteins 0.000 description 1
- 210000001015 abdomen Anatomy 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
Landscapes
- Apparatus For Radiation Diagnosis (AREA)
Description
【発明の詳細な説明】 〔産業上の利用分野〕 本発明は、有効視野に応じた感度補正値で補正するＸ
線CT装置に関する。DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an X field for correcting with a sensitivity correction value corresponding to an effective field of view.
Related to X-ray CT apparatus.
従来、Ｘ線CT装置は、計測空間上の散乱Ｘ線の存在や
測定系の検出精度のばらつき等のため、感度補正値で実
測値を補正させていた。感度補正値を選択するに際し、
有効視野の大きさによつて選択する例が多い。Conventionally, an X-ray CT apparatus has corrected an actual measurement value with a sensitivity correction value due to the presence of scattered X-rays in a measurement space and variations in detection accuracy of a measurement system. When selecting the sensitivity correction value,
In many cases, selection is made according to the size of the effective field of view.
有効視野とは、頭部とか腹部とかの撮影視野のことで
あり、フアンビームの広がりの大きさで規定できる。有
効視野が大になると、大きい減弱量に対応する感度補正
値を選択し、有効視野が小になると小さい減弱量に対応
する感度補正値を選択する。The effective field of view is the field of view of the head or abdomen, and can be defined by the extent of the fan beam. When the effective visual field becomes large, a sensitivity correction value corresponding to a large attenuation is selected, and when the effective visual field becomes small, a sensitivity correction value corresponding to a small attenuation is selected.
上記従来技術では、有効視野と実際の被検体の減弱量
とが対応しない場合に問題が生ずる。例えば、大きい有
効視野を選んだにもかかわらず、実際の被検体の減弱量
が小さいと、選択した感度補正値が大きすぎることにな
る。この結果、線質の変化，散乱線を影響が生じ感度補
正が不正確なものとなる。これにより、リング状のパタ
ーン（アーチフアクト）が発生する。また、小さい有効
視野で最適な感度補正を行つた画像とCT値が異なつたり
する問題があつた。In the above conventional technique, a problem occurs when the effective visual field does not correspond to the actual amount of attenuation of the subject. For example, even if a large effective field of view is selected, if the actual amount of attenuation of the subject is small, the selected sensitivity correction value will be too large. As a result, a change in radiation quality and scattered radiation are caused, resulting in inaccurate sensitivity correction. Thereby, a ring-shaped pattern (artifact) is generated. In addition, there is a problem that the CT value differs from an image subjected to optimal sensitivity correction in a small effective visual field.
一方、小さな有効視野で大きい減弱の被検体を計測し
た場合にも、同様の問題がある。On the other hand, a similar problem occurs when a subject with a large attenuation is measured with a small effective visual field.
本発明の目的は、有効視野の大きさで感度補正値を選
択するのではなく、実際の被検体の減弱量から感度補正
値を選択可能とするＸ線CT装置を提供するものである。SUMMARY OF THE INVENTION An object of the present invention is to provide an X-ray CT apparatus capable of selecting a sensitivity correction value from an actual attenuation amount of a subject, instead of selecting a sensitivity correction value based on the size of an effective visual field.
本発明は、Ｘ線源と、該Ｘ線源と対向して回転すると
共に、被検体を透過した透過Ｘ線を検出する多チャンネ
ルＸ線検出器と、ファントームの計測データを用いて前
記被検体の計測データを補正する補正値を格納する補正
値メモリと、該補正値メモリに記憶してある補正値で前
記被検体よりのＸ線検出器で得られる実測値を補正する
手段とを有し、該補正後の実測値で画像再構成を行うＸ
線CT装置において、前記補正値メモリに格納する補正値
は、有効視野の大きさに応じた複数のファントームのＸ
線減弱量総和に依存した値であって、前記実測値を補正
する手段は、前記多チャンネルＸ線検出器で検出した値
から前記被検体のＸ線減弱量の総和を求め、該被検体の
Ｘ線減弱量総和に対応した前記補正値メモリに格納して
ある補正値を選択し、この選択した補正値を用いて実測
値を補正する手段である、ことを特徴とする。The present invention provides an X-ray source, a multi-channel X-ray detector that rotates in opposition to the X-ray source, and detects transmitted X-rays that have passed through a subject, and the phantom measurement data. A correction value memory for storing a correction value for correcting measurement data of the sample; and a means for correcting an actual measurement value obtained from the subject by an X-ray detector with the correction value stored in the correction value memory. X for performing image reconstruction with the actually measured values after the correction
In the X-ray CT apparatus, the correction values stored in the correction value memory are X-rays of a plurality of phantoms corresponding to the size of the effective visual field.
The means for correcting the actual measurement value, which is a value dependent on the total amount of X-ray attenuation, obtains the total amount of X-ray attenuation of the subject from the value detected by the multi-channel X-ray detector, It is a means for selecting a correction value stored in the correction value memory corresponding to the total amount of X-ray attenuation, and correcting an actually measured value using the selected correction value.
本発明によれば、被検体のＸ線減弱量総和を得て、こ
の総和から対応するファントームのＸ線減弱量総和に依
存した値の補正値を選択する。これにより、被検体のＸ
線減弱量に合った補正値を選びうる。According to the present invention, the total X-ray attenuation of the subject is obtained, and a correction value depending on the total X-ray attenuation of the corresponding phantom is selected from the total. As a result, the X
A correction value that matches the amount of linear attenuation can be selected.
第２図は１つのチヤンネルから減弱量を求める例を示
す図、第３図は全チヤンネル減弱量を求める例を示す図
である。第２図で、被検体１と２とは同一被検体例があ
り、（ａ）図は横長の状態でのあるチヤンネルでの減弱
量３を示す図、（ｂ）図は縦長の状態での同一チヤンネ
ルでの減弱量４を示す図である。この第２図（ａ），
（ｂ）からわかるように、１つのチヤンネルでの減弱量
を求めて、これを、被検体の減弱量とする考え方は、被
検体が状態１と状態とで減弱量３と４とに異なるため、
減弱量としての信頼度はない。FIG. 2 is a diagram showing an example of obtaining an attenuation amount from one channel, and FIG. 3 is a diagram showing an example of obtaining an entire channel attenuation amount. In FIG. 2, there is an example of the same subject as subjects 1 and 2. FIG. 2 (a) is a diagram showing the attenuation 3 in a channel in a horizontally long state, and FIG. 2 (b) is a diagram in a vertically long state. It is a figure which shows attenuation 4 in the same channel. In FIG. 2 (a),
As can be seen from (b), the concept of determining the amount of attenuation in one channel and using it as the amount of attenuation of the subject is different between the state 1 and the state where the amount of attenuation is 3 and 4, respectively. ,
There is no reliability as attenuation.
本実施例では第３図の考え方を採用する。第３図
（ａ）は、状態１での全チヤンネルを通しての減弱量の
総和を斜線で示した図である。一方、第３図（ｂ）は状
態２での全チヤンネルを通しての減弱量の総和を斜線で
示した図である。In this embodiment, the concept of FIG. 3 is adopted. FIG. 3A is a diagram in which the sum of the attenuation amounts through all the channels in the state 1 is indicated by oblique lines. On the other hand, FIG. 3 (b) is a diagram in which the sum of the attenuation amounts through all the channels in the state 2 is indicated by oblique lines.
この第３図（ａ），（ｂ）から明らかなように、状態
1,2の如くＸ線源とＸ線検出器との対向位置が変つて
も、被検体を通しての全チヤンネルを通しての減弱量の
総和5,6は変化しない。然も、この減弱量総和は、被検
体の減弱量の全体値である。As is apparent from FIGS. 3A and 3B, the state
Even if the opposing position of the X-ray source and the X-ray detector changes as in 1, 2, the total attenuation 5, 6 through all the channels through the subject does not change. Needless to say, this total attenuation amount is the total attenuation amount of the subject.
本実施例では、第３図（ａ）又は（ｂ）のいずれにし
ろ、任意の対向位置での全チヤンネルを通して減弱量総
和を求め、この総和から対応する感度補正値を選択する
こととした。In this embodiment, regardless of FIG. 3 (a) or (b), the total attenuation is obtained through all the channels at an arbitrary opposing position, and the corresponding sensitivity correction value is selected from the total.
第４図は、フアントム（擬似被検体）による検出器チ
ヤンネルと減弱量との関係を示す。これは、実際の被検
体の代りに、フアントムを挿入して、このフアントムか
らの計測を減弱量総和として得ようとするための図であ
る。総和値7,8,9は、図に示すように、大，中，小の関
係にあるフアントムの総和値である。かかるフアントム
によれば、実際の被検体による計測をしなくても減弱量
総和を得ることができる。但し、フアントムである故
に、事前にフアントム毎に減弱量総和を求めておき、こ
れをフアントム対応にメモリに格納しておけば、実際の
計測手段は不要である。FIG. 4 shows the relationship between the detector channel and the amount of attenuation by a phantom (simulated subject). This is a diagram for inserting a phantom in place of an actual subject and trying to obtain a measurement from the phantom as a sum of attenuation amounts. The sums 7, 8, and 9 are sums of the phantoms having a large, medium, and small relationship as shown in FIG. According to such a phantom, the total amount of attenuation can be obtained without actually measuring the subject. However, since it is a phantom, if the sum of attenuation amounts is calculated in advance for each phantom and stored in a memory corresponding to the phantom, actual measurement means is unnecessary.
第１図は、本実施例の処理フローである。この実施例
は、被検体を用いて減弱量総和を計測して補正をする実
施例である。先ず、補助メモリ（図示せず）中の感度補
正値を補正値メモリ（主メモリを兼用させてもよい）に
読出し一時格納する（F2）。次に、被検体に対して、任
意のＸ線源とＸ線検出器との対向位置のもとで、フアン
ビームＸ線を被検体に照射する。この透過Ｘ線をＸ線検
出器で検出する。Ｘ線検出器は多チヤンネル検出器であ
り、計算機はこの多チヤンネルＸ線検出器の全チヤンネ
ルの計測値の総加算を行う。尚、実際には、透過Ｘ線量
ではなく対数変換して減弱量を求め、これを計測値と
し、減弱量総和を求める（F3）。FIG. 1 is a processing flow of the present embodiment. This embodiment is an embodiment in which the total amount of attenuation is measured using a subject and correction is performed. First, a sensitivity correction value in an auxiliary memory (not shown) is read out and temporarily stored in a correction value memory (which may also serve as a main memory) (F2). Next, the subject is irradiated with fan beam X-rays at a position where an arbitrary X-ray source and an X-ray detector face each other. This transmitted X-ray is detected by an X-ray detector. The X-ray detector is a multi-channel detector, and the computer performs the total addition of the measured values of all the channels of the multi-channel X-ray detector. In practice, the amount of attenuation is obtained by logarithmic transformation instead of the transmitted X-ray dose, and this is used as a measured value to obtain the total amount of attenuation (F3).
減弱量総和から補正値メモリをアクセスして対応感度
補正値を読出す（F4,F5）。次に補正演算を行う（例え
ば差分や除算）（F6）。そして、補正結果から再構成演
算を行い（F7）、CRTにその再構成像をビデオ信号によ
り表示する（F8）。表示後、終了する（F9）。The correction value memory is accessed from the total attenuation to read out the corresponding sensitivity correction value (F4, F5). Next, a correction operation is performed (for example, a difference or division) (F6). Then, a reconstruction operation is performed from the correction result (F7), and the reconstructed image is displayed on a CRT by a video signal (F8). After the display, the process ends (F9).
第５図は処理システム図である。検出器10とは、多チ
ヤンネル検出器及び積分器、AD変換器を含む入力装置で
ある。CPU11と主メモリ12とは計算機であり、第１図の
処理全体を行う。補助メモリ15は補助値を格納するメモ
リであり、その他に各種の画像データを格納する。CRT1
4は、再構成画像の表示を行う。13は共通バスである。FIG. 5 is a processing system diagram. The detector 10 is an input device including a multi-channel detector, an integrator, and an AD converter. The CPU 11 and the main memory 12 are computers, and perform the entire processing of FIG. The auxiliary memory 15 is a memory for storing auxiliary values, and also stores various image data. CRT1
4 displays a reconstructed image. 13 is a common bus.
このシステム構成により、第１図の処理を実現でき
る。With this system configuration, the processing of FIG. 1 can be realized.
本発明によれば、被検体の実際の減弱量に応じて感度
補正値を選択でき、適正な感度補正を達成することがで
きる。According to the present invention, a sensitivity correction value can be selected according to the actual attenuation amount of a subject, and appropriate sensitivity correction can be achieved.
第１図は本発明の処理の実施例図、第２図はチヤンネル
対応の減弱量を示す図、第３図は被検体の減弱量総和を
求めるための図、第４図はフアントムの例図、第５図は
本発明の処理システム図である。 10……検出系、11……CPU、12……主メモリ、13……共
通バス、14……CRT、15……補助メモリ。FIG. 1 is a diagram showing an embodiment of the process of the present invention, FIG. 2 is a diagram showing an attenuation amount corresponding to a channel, FIG. 3 is a diagram for obtaining a total attenuation amount of a subject, and FIG. 4 is an example diagram of a phantom. FIG. 5 is a diagram of the processing system of the present invention. 10 detection system, 11 CPU, 12 main memory, 13 common bus, 14 CRT, 15 auxiliary memory.
Claims (1)
共に、被検体を透過した透過Ｘ線を検出する多チャンネ
ルＸ線検出器と、ファントームの計測データを用いて前
記被検体の計測データを補正する補正値を格納する補正
値メモリと、該補正値メモリに記憶してある補正値で前
記被検体よりのＸ線検出器で得られる実測値を補正する
手段とを有し、該補正後の実測値で画像再構成を行うＸ
線CT装置において、前記補正値メモリに格納する補正値
は、有効視野の大きさに応じた複数のファントームのＸ
線減弱量総和に依存した値であって、前記実測値を補正
する手段は、前記多チャンネルＸ線検出器で検出した値
から前記被検体のＸ線減弱量の総和を求め、該被検体の
Ｘ線減弱量総和に対応した前記補正値メモリに格納して
ある補正値を選択し、この選択した補正値を用いて実測
値を補正する手段である、ことを特徴とするＸ線CT装
置。1. An X-ray source, a multi-channel X-ray detector which rotates in opposition to the X-ray source and detects transmitted X-rays transmitted through a subject, and measurement data of a phantom. A correction value memory for storing a correction value for correcting measurement data of the subject; and a means for correcting an actual measurement value obtained by the X-ray detector from the subject with the correction value stored in the correction value memory. X for performing image reconstruction with the corrected measured values
In the X-ray CT apparatus, the correction values stored in the correction value memory are X-rays of a plurality of phantoms corresponding to the size of the effective visual field.
The means for correcting the actual measurement value, which is a value dependent on the total amount of X-ray attenuation, obtains the total amount of X-ray attenuation of the subject from the value detected by the multi-channel X-ray detector, An X-ray CT apparatus, which is means for selecting a correction value stored in the correction value memory corresponding to the total amount of X-ray attenuation and correcting an actual measurement value using the selected correction value.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2004584A JP2939281B2 (en) | 1990-01-16 | 1990-01-16 | X-ray CT system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2004584A JP2939281B2 (en) | 1990-01-16 | 1990-01-16 | X-ray CT system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH03210243A JPH03210243A (en) | 1991-09-13 |
| JP2939281B2 true JP2939281B2 (en) | 1999-08-25 |
Family
ID=11588090
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2004584A Expired - Lifetime JP2939281B2 (en) | 1990-01-16 | 1990-01-16 | X-ray CT system |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2939281B2 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4497644B2 (en) * | 2000-04-07 | 2010-07-07 | キヤノン株式会社 | Radiation imaging apparatus, radiation image correction method, and storage medium |
| US20070116183A1 (en) * | 2003-07-30 | 2007-05-24 | Hironori Ueki | Tomograph |
| JP5677751B2 (en) * | 2010-02-24 | 2015-02-25 | 株式会社東芝 | X-ray CT apparatus and image processing program |
-
1990
- 1990-01-16 JP JP2004584A patent/JP2939281B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH03210243A (en) | 1991-09-13 |
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