JPS62127657A - Primary filter for x-ray ct device - Google Patents

Primary filter for x-ray ct device

Info

Publication number
JPS62127657A
JPS62127657A JP60269015A JP26901585A JPS62127657A JP S62127657 A JPS62127657 A JP S62127657A JP 60269015 A JP60269015 A JP 60269015A JP 26901585 A JP26901585 A JP 26901585A JP S62127657 A JPS62127657 A JP S62127657A
Authority
JP
Japan
Prior art keywords
calcium
ray
rays
primary filter
water
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.)
Pending
Application number
JP60269015A
Other languages
Japanese (ja)
Inventor
Shigeru Matsumura
松村 滋
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
GE Healthcare Japan Corp
Original Assignee
Yokogawa Medical Systems Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Yokogawa Medical Systems Ltd filed Critical Yokogawa Medical Systems Ltd
Priority to JP60269015A priority Critical patent/JPS62127657A/en
Publication of JPS62127657A publication Critical patent/JPS62127657A/en
Pending legal-status Critical Current

Links

Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
    • G01N23/02Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material
    • G01N23/04Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and forming images of the material
    • G01N23/046Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and forming images of the material using tomography, e.g. computed tomography [CT]
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2223/00Investigating materials by wave or particle radiation
    • G01N2223/40Imaging
    • G01N2223/419Imaging computed tomograph

Landscapes

  • Health & Medical Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
  • Pulmonology (AREA)
  • Radiology & Medical Imaging (AREA)
  • Theoretical Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Analysing Materials By The Use Of Radiation (AREA)
  • Apparatus For Radiation Diagnosis (AREA)

Abstract

PURPOSE:To correct the sensitivity irregularity of an X-ray detector and to reduce a ring artifact by forming a primary filter by using calcium or material whose atomic number is close to that of calcium. CONSTITUTION:The primary filter 2 is used to reduce the low energy of X rays and improve the ratio of image information to the exposure of an object body. The most principal material which generates a difference between an X-ray spectrum obtained by passing the X rays through water in components of the human body and an X-ray spectrum obtained by passing the X rays through other organism is calcium. for the purpose, the primary filter made of calcium is used to reduce the difference between the sensitivity irregularity of water and the sensitivity irregularity of data obtained by passing the X ray through the human body, thereby obtaining an image of excellent quality by the both. Further, the material is not limited to calcium, but may use another material as long as its atomic number is close to that of calcium, thereby obtaining substantially the same effect by using a filter formed of potassium, scandium, or titanium.

Description

【発明の詳細な説明】 (産業上の利用分野) 本発明は、X線CT装置、特に第3世代のX線CT装置
(CTはComputer T omographyの
略)に生じやすいリングアーティファクトを軽減するた
めに付加しているX線フィルタの改良に関する。
Detailed Description of the Invention (Industrial Application Field) The present invention is directed to reducing ring artifacts that tend to occur in X-ray CT devices, especially third-generation X-ray CT devices (CT stands for Computer Tomography). This article relates to improvements to the X-ray filter added to the.

(従来の技術) 第1図はX粍1cT装置(第3世代の装置)のガン1−
り部の要部構成図である。ガントリ内には360°回転
する回転枠(図示仕ず)の一端にX線管1.1次フィル
タ2とウェッジフィルタ3が取付(′jられ、他端にX
線検出器4とデータ収集装置(DASと略称される)5
が取付けられている。
(Prior art) Figure 1 shows gun 1 of the X-1cT device (third generation device).
FIG. Inside the gantry, an X-ray tube 1, a primary filter 2, and a wedge filter 3 are attached to one end of a rotating frame (not shown) that rotates 360 degrees, and an X-ray tube is attached to the other end.
line detector 4 and data acquisition device (abbreviated as DAS) 5
is installed.

X線管1,1次フィルタ2.ウェッジフィルタ3゜X線
検出器4とは一体になって中心Oを軸に回転し、これら
相互の相対的位置関係は変わらないように形成されてい
る。中央部に被検体が配置されX線管1より照射された
扇状ビームは対向するX線検出器で検出される。検出器
4はX線量に対応した電気信号の得られる多数のX線検
出素子より構成され、各検出素子の出力はデータ収集装
置5により収集され、C丁装置本体側に送られる。
X-ray tube 1, primary filter 2. The wedge filter 3 and the X-ray detector 4 rotate integrally around the center O, and their relative positions remain unchanged. A subject is placed in the center, and a fan-shaped beam irradiated from an X-ray tube 1 is detected by an opposing X-ray detector. The detector 4 is composed of a large number of X-ray detection elements that can obtain electrical signals corresponding to the X-ray dose, and the output of each detection element is collected by a data collection device 5 and sent to the main body of the C-type device.

ウェッジフィルタ3はデータ収集装置5に設けられたア
ナログ・ディジタル変換器のダイナミックレンジの範囲
内に入力を調整でるために使用される補正フィルタで、
被検体への線量を最小にするように作用づる。
The wedge filter 3 is a correction filter used to adjust the input within the dynamic range of the analog-to-digital converter provided in the data acquisition device 5.
It acts to minimize the dose to the subject.

1次フィルタ2はX線の低エネルギーを低減させ、被検
体の被曝に対する画像情報の割合を良くするためのもの
である。X線管1から投q」されるX線は連続X線と線
スベク1ヘルの混在したちのであり、強度分布は第2図
のようになっている。図示のように、この分布は低エネ
ルギーの割合が多い。低エネルギーのX線は物質を透過
Jるにつれて減衰覆る割合が大ぎく、X線検出器4まで
届きにくい。従って低エネルギーを多く含んだX線は、
被検体への被曝が大きい割には、含まねる画像情報は少
ないことになり、このJ、うな低エネルギーのX線を低
減させろために1次フィルタが使用される。この1次フ
ィルタの材質はアルミニウムが用いられている。
The primary filter 2 is for reducing the low energy of X-rays and improving the ratio of image information to radiation exposure of the subject. The X-rays emitted from the X-ray tube 1 are a mixture of continuous X-rays and linear beams, and the intensity distribution is as shown in Figure 2. As shown, this distribution has a high proportion of low energy. Low-energy X-rays are attenuated at a large rate as they pass through substances, making it difficult for them to reach the X-ray detector 4. Therefore, X-rays containing a lot of low energy are
Although the radiation exposure to the subject is large, the amount of image information included is small, and a first-order filter is used to reduce these low-energy X-rays. Aluminum is used as the material for this primary filter.

(弁明が解決しようとする問題点) 一般にX線CTでは、CT値(種々の組織に対応する値
)の定義から水と空気の2つのデータのいずれか一方又
は両方を用いてX線検出器4の特性(主として感度のバ
ラツキ)補正を行うが、水ないし空気を通過したX線ス
ペクトルと、被検体(人体)を通過したX線(特に頭蓋
骨を通過したX線)のスペク1〜ルとの間には大きな差
があるため、検出器のバラツキが完全に補正されない。
(Problem that the defense attempts to solve) Generally, in X-ray CT, from the definition of CT value (value corresponding to various tissues), the X-ray detector uses one or both of two types of data: water and air. 4 characteristics (mainly variations in sensitivity) are corrected, but the X-ray spectrum that has passed through water or air and the spectrum of X-rays that have passed through the subject (human body) (particularly the X-rays that have passed through the skull) are Since there is a large difference between the two, detector variations cannot be completely corrected.

感度のバラツキ(@mムラ)が残っていると逆投影像に
はリングアーティファク1−が生ずる。従って、水や空
気を使って感度ムラを補正しlJとしても頭部の逆投影
像にはリングアーディファク1〜が牛じゃ覆いという問
題があった。
If variations in sensitivity (@m unevenness) remain, a ring artifact 1- will occur in the back projection image. Therefore, even if the sensitivity unevenness is corrected using water or air and lJ is used, there is a problem in that the back-projection image of the head is covered with Ring Ardifac 1~.

本発明は上記問題〆、(に鑑、7)でなされたもので、
その目的は、人骨どスペク1ヘル特性の類似した1次フ
ィルタを使用することにより、頭部とそれ以外の部分(
水、腹部イの他)での×線スベク1〜ルに差がなくなり
、X線検出器の感度ムラがうまく補止でき、リングアー
ティファク1〜が軽減されるX線CT装置の1次フィル
タを提供覆ることにある。
The present invention was made to solve the above problem (see 7),
The purpose of this is to use a first-order filter with similar characteristics to human bones, and to filter the parts of the head and other parts (
A primary filter for X-ray CT equipment that eliminates the difference in X-ray amplitude (1~1) for water (water, abdomen, etc.), effectively compensates for uneven sensitivity of the X-ray detector, and reduces ring artifacts1~. The offer is to cover.

(問題点を解決するための手段) 上記問題点を解決夛る本発明は、X線CT装置のカント
リ内でX線管と被検体の間に配量される1次ノイルりに
おいて、カルシウム又はカルシウムの原子番り)に近い
物質を用いて形成したことを特徴とづるものである。
(Means for Solving the Problems) The present invention, which solves the above-mentioned problems, uses calcium or It is characterized by being formed using a substance with an atomic number close to that of calcium.

(実施例) 以下、図面を参照し、本発明の実施例を詳細に説−,3
− 明する。例えば、すでに水200111を通過した後の
ようなスベクI〜ルを持つX線を用いて、水、空気をス
キ17ンした1、t、の感度ムラの差は、何も通過しな
いX線(第2図〉ε用いてスギャンした水、空への感欧
1、)の差に比べて小さい。これは、変化し易いX線が
先ず取り除かれる結果による。この斐化し易いX線は物
質により異なる。
(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
− Clarify. For example, the difference in sensitivity unevenness between 1 and t when scanning water and air using X-rays that have already passed through water 200111 and 111 is as low as 17 times after passing through water is the difference in sensitivity unevenness between X-rays that do not pass through anything ( Figure 2〉The difference between the water and the sky that was scanned using ε is small compared to 1). This is due to the fact that the sensitive X-rays are removed first. The X-rays that are easily converted to oxidation vary depending on the substance.

異なるX線吸収係数μ分イ[をもった物質間の感;11
ムフの差を少なくするには、X線のスベン1−ルを差が
出にくいようGものに変え4しばよいこと2′)()I
I8¥される。
Sensitivity between substances with different X-ray absorption coefficients
In order to reduce the difference in muff, all you need to do is change the X-ray Sven 1-l to a G-type so that the difference is less likely to appear.2')()I
I will be charged 8 yen.

人体の成分中の水を通したX線スペクトルと仙1ハ組織
を通し・たX線スペクトルとに差を与えている最大の原
因物質IJカルシウム(Ca > −<、・ある、。
Calcium (Ca >-<, ・There is) is the biggest causative substance that causes a difference between the X-ray spectrum that passes through water in the human body and the X-ray spectrum that passes through the tissues of the human body.

i、′1つ−(、カルシウムで形成した1次フィルタを
l)1いれば水の感度ム−・と人体を通したデータの感
度ムラとの差は小さくなり、両方で良質な画像が得られ
ることにイ(る4、尚、カルシウムに限定づる。−二と
なくこれに原子番号の近いもの【パあれけ仙の物質Cも
よい。
If there is one primary filter made of calcium, the difference between the sensitivity of water and the sensitivity unevenness of data transmitted through the human body will be small, and high-quality images can be obtained with both. However, it is limited to calcium. - Substance C that has an atomic number close to this is also good.

÷ 1− 勾ルシウムに隣接する(原子番号で)物質は次のとおり
である。
÷ 1- The substances adjacent to calcium (by atomic number) are:

原子番号:19 20 21 22 物    質 :   K   Ca   Sc   
T!カリウムに、スカンジウムSC,チタンli  の
いずれかで形成したフィルタであれば、カルシウムCa
と実質上同じ効果が得られる。
Atomic number: 19 20 21 22 Substance: K Ca Sc
T! If the filter is made of potassium, scandium SC or titanium li, calcium
Substantially the same effect can be obtained.

尚、カリウム、カルシウム、スカンジウムは化学的にあ
まり安定でイ1い故、化合物か合金にしてフィルタを形
成するのが望j、しい。
Note that since potassium, calcium, and scandium are chemically not very stable, it is desirable to form a filter into a compound or an alloy.

(′ft明の効果) 以−L)小べたように、本発明の1次フィルタによg′
)ば、頭部をスキN7ンしたどきに画像上のリングアー
チ−jノア771〜が軽減される。
(Effect of 'ft brightness) As mentioned above, the first-order filter of the present invention allows g'
) For example, when the head is skinned, the ring arch -j Noah 771~ on the image is reduced.

y、低ニー各ルi’ −X線が♀く減負してし・;];
うたぬ(−起◇カツビ゛ンーノアーティノア/) l〜
(cuppinすartlfacts)ムこの1次フィ
ルタに」、り効果的に低減上!」tろことり(できる1
゜ 、I M面q)百γ11h説明 ′!151NはX線(C■装置のガン1−り部の要部構
成図、第2図はX線スペクトルの強度分布を説明する図
である。
y, each low knee i' - X-ray is reduced by ♀;];
Utanu (-Katsubino Artinoa/) l~
(cuppin arts) This first-order filter effectively reduces the amount! ”Trokotori (can do 1
゜, IM side q) 100γ11h explanation'! 151N is a diagram illustrating the main part of the gun 1-port of the X-ray (C) apparatus, and FIG. 2 is a diagram illustrating the intensity distribution of the X-ray spectrum.

1・・・X線管      2・・・1次ノイルク3・
・・ウェッジフィルタ 4・・・X線検出器5・・・ア
ータ収集装同 特許出願人 横河メディカルシス−jム株式会社7一
1...X-ray tube 2...1st-order noise 3.
... Wedge filter 4 ... X-ray detector 5 ... Atta collection system Patent applicant Yokogawa Medical Systems Co., Ltd. 71

Claims (1)

【特許請求の範囲】[Claims] X線CT装置のガントリ内でX線管と被検体の間に配置
される1次フィルタにおいて、カルシウム又はカルシウ
ムの原子番号に近い物質を用いて形成したことを特徴と
するX線CT装置の1次フィルタ。
1 of the X-ray CT apparatus, characterized in that the primary filter disposed between the X-ray tube and the subject in the gantry of the X-ray CT apparatus is formed using calcium or a substance with an atomic number close to calcium; Next filter.
JP60269015A 1985-11-29 1985-11-29 Primary filter for x-ray ct device Pending JPS62127657A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP60269015A JPS62127657A (en) 1985-11-29 1985-11-29 Primary filter for x-ray ct device

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP60269015A JPS62127657A (en) 1985-11-29 1985-11-29 Primary filter for x-ray ct device

Publications (1)

Publication Number Publication Date
JPS62127657A true JPS62127657A (en) 1987-06-09

Family

ID=17466484

Family Applications (1)

Application Number Title Priority Date Filing Date
JP60269015A Pending JPS62127657A (en) 1985-11-29 1985-11-29 Primary filter for x-ray ct device

Country Status (1)

Country Link
JP (1) JPS62127657A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2664708A1 (en) * 1990-07-10 1992-01-17 Gen Electric Cgr Method for correcting the hardening of an X-ray beam in a scanner

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5832200A (en) * 1981-08-20 1983-02-25 ワコー電子株式会社 Intensifying method for monochromatism of characteristic x rays

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5832200A (en) * 1981-08-20 1983-02-25 ワコー電子株式会社 Intensifying method for monochromatism of characteristic x rays

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2664708A1 (en) * 1990-07-10 1992-01-17 Gen Electric Cgr Method for correcting the hardening of an X-ray beam in a scanner

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