JP2853065B2 - X-ray imaging method - Google Patents
X-ray imaging methodInfo
- Publication number
- JP2853065B2 JP2853065B2 JP3222535A JP22253591A JP2853065B2 JP 2853065 B2 JP2853065 B2 JP 2853065B2 JP 3222535 A JP3222535 A JP 3222535A JP 22253591 A JP22253591 A JP 22253591A JP 2853065 B2 JP2853065 B2 JP 2853065B2
- Authority
- JP
- Japan
- Prior art keywords
- ray
- rays
- energy
- effective energy
- filter
- 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
- 238000003384 imaging method Methods 0.000 title claims description 61
- 238000009826 distribution Methods 0.000 claims description 13
- 238000000034 method Methods 0.000 claims description 4
- 238000012545 processing Methods 0.000 claims description 4
- 230000000052 comparative effect Effects 0.000 description 18
- 230000005855 radiation Effects 0.000 description 10
- 238000002083 X-ray spectrum Methods 0.000 description 6
- 230000006378 damage Effects 0.000 description 6
- 238000003745 diagnosis Methods 0.000 description 5
- 238000010586 diagram Methods 0.000 description 5
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical group [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 230000005540 biological transmission Effects 0.000 description 3
- 210000000988 bone and bone Anatomy 0.000 description 3
- 229910052732 germanium Inorganic materials 0.000 description 3
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 3
- 239000004065 semiconductor Substances 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 208000005718 Stomach Neoplasms Diseases 0.000 description 1
- 208000027418 Wounds and injury Diseases 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 238000002591 computed tomography Methods 0.000 description 1
- 238000002247 constant time method Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 230000008030 elimination Effects 0.000 description 1
- 238000003379 elimination reaction Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 206010017758 gastric cancer Diseases 0.000 description 1
- 208000014674 injury Diseases 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 201000011549 stomach cancer Diseases 0.000 description 1
Landscapes
- Radiography Using Non-Light Waves (AREA)
- Apparatus For Radiation Diagnosis (AREA)
Description
【０００１】[0001]
【産業上の利用分野】本発明はＸ線撮像方法、特に被曝
線量を大巾に低減でき、且つ高分解能を得る透過型のＸ
線撮像方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray imaging method, and more particularly, to a transmission type X-ray system capable of greatly reducing exposure dose and obtaining high resolution.
The present invention relates to a line imaging method.
【０００２】この種のＸ線撮像方法は医療診断分野に採
用さて、体内患部を早期に診断し得、有用である。[0002] This type of X-ray imaging method is useful in the field of medical diagnosis and can diagnose an affected part in the body at an early stage, and is useful.
【０００３】[0003]
【従来の技術】一般に体内患部の医療診断においては透
過型のＸ線撮像方法が多用されている。即ちＸ線管球か
らＸ線を放射せしめ、対象体に透過させた後、イメージ
・インテンシフアイア（以下“Ｉ．Ｉ．”という）カメ
ラにより直接的に撮像するか、あるいはＸ線フイルムに
より撮影する構成がとられる。2. Description of the Related Art In general, a transmission type X-ray imaging method is frequently used in medical diagnosis of a diseased part in a body. That is, X-rays are emitted from an X-ray tube and transmitted through an object, and then directly imaged by an image intensifier (hereinafter, referred to as "II") camera or photographed by an X-ray film The following configuration is adopted.
【０００４】この場合概して適切なＸ線画像を得ようと
すればＸ線の照射線量が増大する上、多様の角度からの
多数のＸ線画像を撮像する必要があつて、医療現場で従
事する医師等が多量の被曝線量を余儀なくされる問題が
ある。１９８９年１２月の米国科学アカデミーの発表に
よれば被曝線量と放射線障害との関係は比例的であり、
特に低レベル放射線を相対的に短時間、何回も照射され
ると放射線障害（例えば胃ガン等）の罹病率が３〜４倍
に及ぶことが明らかにされている。Ｘ線ＣＴ法などは患
部のリアルタイムな診断に大きな効果を挙げているが、
Ｘ線の照射線量は撮像時間に応じて増大する。[0004] In this case, in general, to obtain an appropriate X-ray image, the irradiation dose of the X-ray is increased, and it is necessary to capture a large number of X-ray images from various angles. There is a problem that doctors and the like are forced to receive large doses. According to the announcement of the National Academy of Sciences in December 1989, the relationship between radiation dose and radiation damage was proportional,
In particular, it has been shown that the morbidity of radiation damage (for example, stomach cancer, etc.) can be increased three to four times when a low level radiation is irradiated for a relatively short time and many times. X-ray CT and other methods have a great effect on real-time diagnosis of affected areas,
The X-ray irradiation dose increases according to the imaging time.
【０００５】[0005]
【発明が解決しようとする課題】一方Ｘ線撮像方法にお
いては例えば骨の撮像時に骨の厚さとＸ線フイルム上の
骨像の黒化度とが比例しない、いわゆるビームハードニ
ング現象を来す問題もある。換言すればＸ線は連続した
エネルギスペクトル分布を示すが、この分布パターンが
一方に傾斜するため正確な撮像を行うには問題がある。
上記のＸ線ＣＴ法ではこのビームハードニング現象を、
コンピユータによつて複雑な補正を一時的に行い解決し
ているが、設備が大巾にコスト高になる問題がある。更
にＸ線が発見されて１００年有余を経過した現在、Ｘ線
の専門書の一部にビームハードニング現象の排除（回
避）の記述はあるものの、いかなる従来技術によつても
ビームハードニング現象を、完全に排除（回避）するも
のはない。このような技術思想を基礎として、当業者が
Ｘ線の実効エネルギーの変動を、フイルターにおいてど
の程度コントロールすればビームハードニング現象が完
全に排除できるかの技術思想に想倒することは極めて困
難であるものと考えられる。即ちＸ線の実効エネルギー
の変動を、フイルターにおいて±０％領域にもたらす技
術事項を全く知得せずに、従来用いられた例えばＡｌ
２．５ｍｍ以下の薄いフイルターを付加してビームハー
ドニング現象の回避を試みても満足できる結果は得られ
ないものと考えられる。On the other hand, in the X-ray imaging method, for example, when imaging a bone, there is a problem that a so-called beam hardening phenomenon occurs in which the thickness of the bone is not proportional to the degree of blackening of the bone image on the X-ray film. There is also. In other words, X-rays show a continuous energy spectrum distribution, but there is a problem in performing accurate imaging because this distribution pattern is inclined to one side.
In the above X-ray CT method, this beam hardening phenomenon
Although complicated correction is temporarily performed by a computer to solve the problem, there is a problem that the cost of the equipment is greatly increased. At present, more than 100 years have passed since the discovery of X-rays, although there is a description of elimination (avoidance) of the beam hardening phenomenon in a part of the technical book on X-rays, the beam hardening phenomenon cannot be achieved by any conventional technology. There is nothing to completely eliminate (avoid). Based on such a technical idea, it is extremely difficult for a person skilled in the art to think back to the technical idea of how much the variation of the effective energy of X-rays can be controlled by a filter to completely eliminate the beam hardening phenomenon. Probably. That is, without knowing any technical matter which brings about the fluctuation of the effective energy of X-rays in the ± 0% region in the filter, for example, the conventional method of using Al
It is considered that satisfactory results cannot be obtained even if an attempt is made to avoid the beam hardening phenomenon by adding a thin filter of 2.5 mm or less.
【０００６】Ｘ線のビームハードニング現象を克服する
構成としては本件発明者による米国特許第４，７２７，
５６１号並びに米国特願第２９９，５３８号が提案され
る。これらの場合同一Ｘ線管からのＸ線を一方のセンサ
において測定対象を通過させることなく受光し、他方の
センサにおいて測定対象の厚さに伴う線吸収係数の変化
のないフイルタ並びに測定対象を通過したＸ線を受光し
た後、両者の強度の比を求めることによりビームハード
ニング現象の影響を有効に回避して測定対象の高精度の
解析を実現する構成がとられている。A configuration for overcoming the X-ray beam hardening phenomenon is disclosed in US Pat.
No. 561 and US Patent Application No. 299,538 are proposed. In these cases, X-rays from the same X-ray tube are received by one sensor without passing through the object to be measured, and the other sensor passes through a filter having no change in the linear absorption coefficient due to the thickness of the object to be measured and the object to be measured. After receiving the X-rays obtained, the ratio of the intensities of the two is obtained, thereby effectively avoiding the effect of the beam hardening phenomenon and realizing highly accurate analysis of the measurement object.
【０００７】本発明は上述の先行発明におけるビームハ
ードニング現象の回避構成を基礎とし、効果的なＸ線撮
像方法を創作することを企図する。The present invention intends to create an effective X-ray imaging method based on the configuration for avoiding the beam hardening phenomenon in the above-mentioned prior invention.
【０００８】しかして本発明の目的はＸ線の照射線量が
大巾に減じられて患者、医師あるいは操作者等への被曝
線量を低減し放射線障害を最小限に制えると共に、ビー
ムハードニング現象を有効に回避し、高分解能の撮像を
可能にしたＸ線撮像方法を提供するにある。SUMMARY OF THE INVENTION It is an object of the present invention to significantly reduce the radiation dose of X-rays, reduce the radiation dose to patients, doctors or operators, minimize radiation damage, and reduce the beam hardening phenomenon. The present invention is to provide an X-ray imaging method capable of effectively avoiding the problem and enabling high-resolution imaging.
【０００９】[0009]
【問題点を解決するための手段】本発明によればこの目
的はＸ線管からＸ線を放射し、Ｘ線管から放射されたＸ
線をフイルタに通過させ、フイルタを通過したＸ線を撮
像対象に通過させた後撮像装置によつて撮像させてなる
Ｘ線撮像方法において、Ｘ線管から放射されたＸ線の実
効エネルギの変動をフイルタにおいて±１０％以内に収
めることを特徴とすることにより、達成される。SUMMARY OF THE INVENTION According to the present invention, an object of the present invention is to emit X-rays from an X-ray tube and to emit X-rays from the X-ray tube.
In an X-ray imaging method in which X-rays are passed through a filter, X-rays passing through the filter are passed through an imaging target, and then imaged by an imaging device, fluctuations in the effective energy of X-rays emitted from an X-ray tube Is achieved within ± 10% in the filter.
【００１０】[0010]
【作用】上述のように構成された本発明においてはＸ線
の実効エネルギの変動を±１０％以内に抑制して撮像対
象に照射するから、ビームハードニング現象を効果的に
回避して良好な解像度を得る上、特に照射線量を顕著に
低減する作用が実現される。しかして本発明において
は、Ｘ線の実効エネルギーの変動をフイルターにおいて
±０％に抑えた構成をとるから、ビームハードニング現
象が完全に排除され、特に同一被検体の厚さが変わつて
も、線吸収係数（μ）はほゞ一定値を示しグラフ上ほゞ
直線になる。従つて、Ｘ線の線質（直線性）補正を不要
にし得る。According to the present invention constructed as described above, since the variation in the effective energy of X-rays is suppressed to within ± 10% to irradiate the object to be imaged, the beam hardening phenomenon can be effectively avoided to achieve a good result. In addition to obtaining the resolution, the effect of remarkably reducing the irradiation dose is realized. Therefore, in the present invention, since the variation of the effective energy of the X-rays is suppressed to ± 0% in the filter, the beam hardening phenomenon is completely eliminated, and even if the thickness of the same subject changes, particularly, The linear absorption coefficient (μ) shows a substantially constant value and becomes a substantially straight line on the graph. Therefore, it may not be necessary to correct the X-ray quality (linearity).
【００１１】[0011]
【実施例】図１を参照するに本発明によるＸ線撮像方法
に採用されるシステム１０が示されており、システム１
０にはＸ線管球のようなＸ線源１１が含まれる。Ｘ線源
１１からは例えば１Å以下の硬Ｘ線ビームが照射可能に
設けられ、Ｘ線源の下方には回転フイルタデイスク１２
が配設される。回転フイルタデイスク１２には円周方向
に相互に離間させて多数のフイルタ部材１３、１３ａ、
１３ｂ、……１３ｎが配列され、回転駆動装置１４によ
り適宜の角度回転されたとき、多数のフイルタ部材１
３、１３ａ、１３ｂ、……１３ｎの一がＸ線源１１の直
下に配置される。またフイルタ部材１３、１３ａ、１３
ｂ、……１３ｎ相互はＸ線源１１への各種の印加電圧、
換言すればＸ線源１１からの各種のＸ線スペクトル分布
に相応するに異ならしめられており、放射されるＸ線の
実効エネルギの変動を±１０％以内に収めるように設定
される。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, there is shown a system 10 employed in an X-ray imaging method according to the present invention.
0 includes an X-ray source 11 such as an X-ray tube. For example, a hard X-ray beam of 1 ° or less is provided from the X-ray source 11, and a rotating filter disk 12 is provided below the X-ray source.
Is arranged. A number of filter members 13, 13a are spaced apart from each other in the circumferential direction on the rotary filter disk 12.
.. 13n are arranged, and when rotated by an appropriate angle by the rotation driving device 14, a large number of filter members 1 are formed.
One of 3, 13a, 13b,... 13n is disposed immediately below the X-ray source 11. Also, the filter members 13, 13a, 13
b,... 13n are various applied voltages to the X-ray source 11,
In other words, the X-ray source is varied so as to correspond to the various X-ray spectrum distributions from the X-ray source 11, and is set so that the fluctuation of the effective energy of the emitted X-ray is within ± 10%.
【００１２】Ｘ線源１１並びに回転フイルタデイスク１
２の回転駆動装置１４は夫々Ｘ線制御装置１５並びにフ
イルタ制御装置１６の各々により制御可能に設けられ、
フイルタ制御装置１６はＸ線制御装置１５と連係されて
いて、Ｘ線の実効エネルギに相応したフイルタ部材が割
出され得る。回転フイルタデイスク１２を通過したＸ線
は撮像用のテーブル１７に乗せられた撮像対象ＯＪに照
射され、このときフイルムカセツト１８内のＸ線フイル
ムに撮像対象ＯＪが撮影される。X-ray source 11 and rotary filter disk 1
The two rotation driving devices 14 are provided so as to be controllable by the X-ray control device 15 and the filter control device 16, respectively.
The filter control device 16 is linked to the X-ray control device 15 so that a filter member corresponding to the effective energy of the X-ray can be indexed. The X-rays that have passed through the rotary filter disk 12 are irradiated on the imaging target OJ placed on the imaging table 17, and at this time, the imaging target OJ is captured on the X-ray film in the film cassette 18.
【００１３】一方必要ならばフイルムカセツト１８を除
去して撮像対象ＯＪを通過したＸ線をＩ．Ｉ．カメラ１
９に付与することもでき、この場合Ｉ．Ｉ．カメラ１９
にはカメラ制御装置２０が連係されていて好適な制御を
受けると共に、Ｉ．Ｉ．カメラ１９において撮像したＸ
線画像を、カメラ制御装置２０を介し画像処理装置２１
に送り、更にこの画像処理装置２１と連係するＣＲＴ２
２にて透視画像として出力する。On the other hand, if necessary, the film cassette 18 is removed, and the X-rays that have passed through the object to be imaged O.I. I. Camera 1
9 in this case, in which case I.I. I. Camera 19
Is connected to a camera control device 20 to receive suitable control. I. X taken by camera 19
A line image is converted into an image processing device 21 via a camera control device 20.
To the CRT 2 linked to the image processing apparatus 21.
In step 2, the image is output as a perspective image.
【００１４】しかして上述のシステム１０においてはＸ
線制御装置１５によりＸ線の照射エネルギを調整しつゝ
Ｘ線源１１からＸ線を照射する。次に照射されたＸ線を
回転フイルタデイスク１２を作動して割出したフイルタ
部材１３、１３ａ、１３ｂ、……１３ｎの一に通過さ
せ、Ｘ線の実効エネルギの変動を±１０％以内に収め
る。このとき回転フイルタデイスク１２の作動はＸ線制
御装置１５からＸ線源１１への出力に相応させてフイル
タ制御装置１６により回転駆動装置１４を駆動せしめ遂
行する。フイルタ部材を通過したＸ線は撮像対象に照射
させ、フイルムカセツト１８内のＸ線フイルムにおいて
いわゆる直接撮影法による撮像を得るか、あるいはＩ．
Ｉ．カメラ１９、カメラ制御装置２０並びに画像処理装
置２１を経、ＣＲＴ２２において透視画像を得る。Thus, in the system 10 described above, X
The irradiation energy of X-rays is adjusted by the X-ray controller 15 and X-rays are emitted from the X-ray source 11. Then, the irradiated X-rays are passed through one of the indexed filter members 13, 13a, 13b,..., 13n by operating the rotary filter disk 12 so that the fluctuation of the effective energy of the X-rays is kept within ± 10%. . At this time, the operation of the rotary filter disk 12 is performed by driving the rotary drive unit 14 by the filter control unit 16 in accordance with the output from the X-ray control unit 15 to the X-ray source 11. The X-rays that have passed through the filter member are irradiated to the object to be imaged, and an image is obtained by the so-called direct imaging method on the X-ray film in the film cassette 18 or I.
I. Through the camera 19, the camera control device 20 and the image processing device 21, a fluoroscopic image is obtained on the CRT 22.
【００１５】実験例１ 本発明によるＸ線撮像方法を採用し、撮像対象としてＡ
ｌ板を用いて、Ａｌ板の積層厚を徐々に０ｍｍ〜１０．
０ｍｍまで５段階に変化させ、純ゲルマニウム半導体検
出器及び波高分析器によりＸ線スペクトル分布を計測し
た。この結果図２に示す如く実効エネルギ分布に傾斜を
生ぜず、エネルギ分布の中心値を結ぶ破線Ｐ１が実質的
に垂直になつた。従つて本Ｘ線撮像方法によればビーム
ハードニング現象の影響を実質的に回避でき、分解能を
向上し得ることが判明した。尚本実験例においてＸ線源
１１の管電圧を１２０ｋＶ、管電流を５０μＡにして実
施した。Experimental Example 1 The X-ray imaging method according to the present invention was adopted,
The thickness of the Al plate is gradually reduced from 0 mm to 10.
The X-ray spectrum distribution was measured using a pure germanium semiconductor detector and a pulse height analyzer while changing the distance to 0 mm in five steps. As a result, as shown in FIG. 2, the effective energy distribution did not have a slope, and the broken line P1 connecting the center values of the energy distribution became substantially vertical. Therefore, it has been found that according to the X-ray imaging method, the influence of the beam hardening phenomenon can be substantially avoided and the resolution can be improved. In this experiment, the tube voltage of the X-ray source 11 was set to 120 kV and the tube current was set to 50 μA.
【００１６】比較例１ 回転フイルタデイスクを割愛した点を除き実験例１と同
一の撮像方法を採用し、撮像対象としてＡｌ板を用い、
Ａｌ積層板厚を徐々に０ｍｍ〜２．０ｍｍまで４段階に
変化させて純ゲルマニウム半導体検出器及び波高分析器
によりＸ線スペクトル分布を計測した。この結果図３ａ
に示す如く実効エネルギ分布に傾斜を生じた。即ち実効
エネルギの中心値を結ぶ破線直線Ｐ２がビームハードニ
ング現象の影響を受けて傾斜し、実効エネルギの変動巾
が±２２％程度に達して、分解能が低下した。Comparative Example 1 The same imaging method as in Experimental Example 1 was adopted except that the rotary filter disk was omitted, and an Al plate was used as an imaging target.
The thickness of the Al laminated plate was gradually changed in four steps from 0 mm to 2.0 mm, and the X-ray spectrum distribution was measured by a pure germanium semiconductor detector and a pulse height analyzer. As a result, FIG.
As shown in the figure, the effective energy distribution was inclined. That is, the dashed straight line P2 connecting the center values of the effective energies was inclined under the influence of the beam hardening phenomenon, the fluctuation range of the effective energy reached about ± 22%, and the resolution was reduced.
【００１７】比較例２ 回転フイルタデイスクを割愛した点を除き実験例１と同
一の撮像方法を採用し、且つ撮像対象としてＡｇ板を用
いると共に、Ａｇ板の積層厚を徐々に０ｍｍ〜０．２ｍ
ｍまで５段階に変化させ、純ゲルマニウム半導体検出器
及び波高分析器によりＸ線スペクトル分布を計測した。
この結果図３ｂに示す如くビームハードニング現象の影
響を強く受けて図３ａに示すＡｌの場合より実効エネル
ギの中心値を結ぶ破線直線Ｐ３が大きく傾斜し、実効エ
ネルギの変動巾が±３１％程度に達して、分解能が更に
低下することが判明した。Comparative Example 2 The same imaging method as in Experimental Example 1 was adopted except that the rotary filter disk was omitted, and an Ag plate was used as an object to be imaged, and the thickness of the Ag plate was gradually reduced from 0 mm to 0.2 m.
m, and the X-ray spectrum distribution was measured with a pure germanium semiconductor detector and a pulse height analyzer.
As a result, as shown in FIG. 3B, the dashed straight line P3 connecting the center values of the effective energy is more greatly affected by the beam hardening phenomenon than in the case of Al shown in FIG. 3A, and the fluctuation range of the effective energy is about ± 31%. And it was found that the resolution was further reduced.
【００１８】上述の比較例１、２から明らかなように撮
像対象の原子番号が大きい程、ビームハードニング現象
を受けるものと考えられる。従つて撮像対象の持つ原子
番号の一をもパラメータとして勘案し、ビームハードニ
ング現象を回避する、即ちＸ線の実効エネルギ分布にお
いて実効エネルギの中心値を結ぶ直線に傾斜を生じない
よう回転フイルタデイスク上のフイルタ部材を選定して
割出回転させれば、撮像対象を問わず良好な画像を得る
ことができる。これにより比較例１、２の場合図７に示
す如く撮像対象ないしは原子番号によつて実効エネルギ
は変動したが、本発明による実験例１によれば図６に示
すように撮像対象ないしは原子番号にかかわらず、実効
エネルギの変動は実質的に抑制され、定性定量の判別が
可能になつた。As apparent from Comparative Examples 1 and 2, it is considered that the larger the atomic number of the object to be imaged, the more the beam hardening phenomenon occurs. Therefore, taking into account one of the atomic numbers of the object to be imaged as a parameter, the beam hardening phenomenon is avoided, that is, a rotating filter disk is used so that a straight line connecting the central values of the effective energy in the effective energy distribution of the X-ray does not have an inclination. If the upper filter member is selected and indexed and rotated, a good image can be obtained regardless of the imaging target. Thus, in Comparative Examples 1 and 2, the effective energy fluctuated depending on the imaging target or the atomic number as shown in FIG. 7, but according to Experimental Example 1 of the present invention, as shown in FIG. Regardless, fluctuations in the effective energy were substantially suppressed, and qualitative and quantitative discrimination became possible.
【００１９】一方本発明による撮像方法においても電源
電圧、電流、室温、湿度などの条件の変化により実効エ
ネルギが変動するものの、実効エネルギが１００ｋｅＶ
以下のときは±１０ｋｅＶ以内の変動に収め、且つ１０
０ｋｅＶを越えるときはその±１０％以内の変動に収め
れば実効エネルギの定常化を図ることができる。換言す
れば図２に破線Ｐ１で示すような実効エネルギの中心値
を結ぶ直線の傾斜が有効に抑えられ、実効エネルギの変
動が±１０％以内、更に好適には±０％に近付くように
Ｘ線照射直後のＸ線をフイルタリングすることになる。In the imaging method according to the present invention, on the other hand, although the effective energy fluctuates due to changes in conditions such as power supply voltage, current, room temperature, and humidity, the effective energy is 100 keV.
In the following cases, the fluctuation is kept within ± 10 keV, and
When the voltage exceeds 0 keV, the steady state of the effective energy can be achieved by keeping the fluctuation within ± 10% of the fluctuation. In other words, the slope of the straight line connecting the center values of the effective energy as shown by the broken line P1 in FIG. 2 is effectively suppressed, and the variation of the effective energy is within ± 10%, more preferably, close to ± 0%. X-rays immediately after the irradiation are filtered.
【００２０】実験例２ 本発明によるＸ線撮像方法を採用し、撮像対象としてＡ
ｌ板を用い、これを徐々に積層して最上層のＡｌ板の周
辺縁の像が残ると共に中央部の像が見えなくなるまでの
黒化度をＩ．Ｉ．カメラを通し、ＣＲＴでモニタした。
これにより撮像対象としてのＡｌ板の見える最小厚を測
定した。且つまた撮像対象としてのＡｌ板の上面に径が
０．６ｍｍの銅線リングを置き、徐々にＡｌ板を積層し
ていき、頂部に位置させた銅線リングの像が見えなくな
るまでの黒化度をＩ．Ｉ．カメラを通しＣＲＴでモニタ
した。これにより撮像対象としてのＡｌ板の見える最大
厚を測定した。尚本実施例においてはＸ線源の管電圧を
８０ｋＶ、管電流を１ｍＡにして実施した。Experimental Example 2 The X-ray imaging method according to the present invention was adopted,
These plates are gradually laminated, and the degree of blackening until the image of the peripheral edge of the Al plate of the uppermost layer remains and the image of the central portion becomes invisible becomes I. I. It was monitored on a CRT through a camera.
Thus, the minimum visible thickness of the Al plate as an imaging target was measured. In addition, a copper wire ring having a diameter of 0.6 mm is placed on the upper surface of the Al plate as an imaging target, and the Al plate is gradually laminated, and blackening is performed until the image of the copper wire ring positioned at the top becomes invisible. Degree I. I. It was monitored on a CRT through a camera. Thus, the maximum visible thickness of the Al plate as an imaging target was measured. In this embodiment, the tube voltage of the X-ray source was set to 80 kV and the tube current was set to 1 mA.
【００２１】比較例３ 回転フイルタデイスクの使用を割愛した点を除き実験例
２と同一の撮像方法を採用し、且つ実験例２と同様にし
てＡｌ板の最小厚並びに最大厚を測定した。Comparative Example 3 The same imaging method as in Experimental Example 2 was adopted except that the use of the rotating filter disk was omitted, and the minimum thickness and the maximum thickness of the Al plate were measured in the same manner as in Experimental Example 2.
【００２２】これらの実験例２並びに比較例３における
Ａｌ板の厚さと黒化度との関係を図４に示した。また図
４に基づいてＡｌ板の見える範囲（焦点深度）とＡｌ板
の厚さ勾配を図５に示した。これらの結果本発明による
実験例２での照射線量Ｒ１は５４ｍＲ／分になり、比較
例における照射線量Ｒ２の２，０２０ｍＲ／分に比べ
て、２．７％｛（Ｒ１／Ｒ２）ｘ１００｝に激減した。
且つまた実験例２において最上層のＡｌ板中央が見えな
くなるまでのＡｌ板の最小厚Ｔ１は２．４ｃｍであり、
比較例３における最上層のＡｌ板の中央が見えなくなる
までのＡｌ板の最小厚Ｔ２は４．０ｃｍとなつて本発明
による場合照射線量が１／３７に激減したにもかゝわら
ず６０％｛（Ｔ１／Ｔ２）ｘ１００｝程度にとどまつ
た。一方実験例において頂部に位置する銅線リングの像
が見えなくなるまでのＡｌ板の最大厚Ｔ３は７．４ｃｍ
であり、比較例３において頂部に位置する銅線リングの
像が見えなくなるまでのＡｌ板の最大厚Ｔ４は８．６ｃ
ｍとなつて本発明による場合８６％｛（Ｔ３／Ｔ４）ｘ
１００｝程度にとどまつた。従つて本実験例２による場
合Ｘ線透過に際しＡｌ板の見える範囲Ｚ１は５．０ｃｍ
（Ｔ３−Ｔ１）となるが、比較例３による場合その見え
る範囲Ｚ２は４．６ｃｍ（Ｔ４−Ｔ２）となつて、本実
験例２によれば比較例３に比べ１０９％｛（Ｚ１／Ｚ
２）ｘ１００｝、見える範囲が広がることが判明した。FIG. 4 shows the relationship between the thickness of the Al plate and the degree of blackening in Experimental Example 2 and Comparative Example 3. FIG. 5 shows the visible range (depth of focus) of the Al plate and the thickness gradient of the Al plate based on FIG. As a result, the irradiation dose R1 in the experimental example 2 according to the present invention was 54 mR / min, which was 2.7% {(R1 / R2) × 100} compared to the irradiation dose R2 of 2,020 mR / min in the comparative example. It has dropped dramatically.
Further, in Experimental Example 2, the minimum thickness T1 of the Al plate until the center of the uppermost Al plate became invisible was 2.4 cm,
In Comparative Example 3, the minimum thickness T2 of the Al plate until the center of the Al plate of the uppermost layer became invisible was 4.0 cm, and in the case of the present invention, 60% although the irradiation dose was drastically reduced to 1/37. {(T1 / T2) × 100}. On the other hand, in the experimental example, the maximum thickness T3 of the Al plate until the image of the copper wire ring located at the top becomes invisible is 7.4 cm.
In Comparative Example 3, the maximum thickness T4 of the Al plate until the image of the copper wire ring located at the top became invisible was 8.6c.
86% ｛(T3 / T4) x
It stayed at about 100｝. Therefore, in the case of Experimental Example 2, the visible range Z1 of the Al plate during X-ray transmission is 5.0 cm.
(T3-T1), but in the case of the comparative example 3, the visible range Z2 is 4.6 cm (T4-T2), and according to the experimental example 2, it is 109% ｛(Z1 / Z) as compared with the comparative example 3.
2) x100 °, it was found that the visible range was widened.
【００２３】実験例３〜７ 更に表１の如く撮像対象並びに管電圧を変化させ実験例
２と同様にして照射線量並びに撮像対象の像の見える範
囲を測定した。この場合Ｘ線源の管電圧に応じてフイル
タ部材も表１のように適宜変えた。Experimental Examples 3 to 7 Further, as shown in Table 1, the imaging object and the tube voltage were changed, and the irradiation dose and the visible range of the image of the imaging object were measured in the same manner as in Experimental Example 2. In this case, the filter members were appropriately changed as shown in Table 1 according to the tube voltage of the X-ray source.
【００２４】[0024]
【表１】 [Table 1]
【００２５】比較例４〜８ 更に表１の如く撮像対象並びに管電圧を変化させて比較
例３と同様にして照射線量並びに撮像対象の像の見える
範囲を測定した。Comparative Examples 4 to 8 Further, as shown in Table 1, the irradiation object and the visible range of the image of the object were measured in the same manner as in Comparative Example 3 by changing the imaging object and the tube voltage.
【００２６】これらの実験例３〜７並びに比較例４〜８
の結果から明らかな如く、本発明によるＸ線撮像方法に
よる場合照射線量を１／８〜１／２５にまで激減し得、
延いては操作者の被曝線量を最小限にできる上、満足で
きる解像力が維持され得、医療診断分野に採用して極め
て有用であり、且つ撮像対象に対する分解能が顕著に向
上され、見える範囲も広くし得ると共に、高品質のＸ線
画像を提供できることが判明した。Experimental Examples 3 to 7 and Comparative Examples 4 to 8
As is clear from the results, the irradiation dose can be drastically reduced to 1/8 to 1/25 by the X-ray imaging method according to the present invention,
As a result, the exposure dose to the operator can be minimized, and satisfactory resolution can be maintained. This is extremely useful in the field of medical diagnosis, and the resolution of the imaging target is significantly improved, and the visible range is wide. It has been found that high quality X-ray images can be provided.
【００２７】更に本発明によるＸ線撮像方法でＸ線撮影
を行う場合、通常の撮像条件での管電圧を１０〜２０％
増大させても、照射線量の大巾な低減を図りつゝ、市販
のＸ線フイルムによつて極めて高品質のＸ線画像を得る
ことができる。Further, when X-ray imaging is performed by the X-ray imaging method according to the present invention, the tube voltage under normal imaging conditions is increased by 10 to 20%.
Even if it is increased, it is possible to greatly reduce the irradiation dose, and it is possible to obtain an extremely high-quality X-ray image using a commercially available X-ray film.
【００２８】実験例８、９ 表２の如く通常の撮影条件での管電圧を各々２０％増加
して、市販のＸ線フイルムによりＸ線画像を得た。同表
２に夫々の実験例の照射線量を通常の撮影条件での照射
線量と対比して示してある。Experimental Examples 8 and 9 As shown in Table 2, X-ray images were obtained with commercially available X-ray films while increasing the tube voltage under normal imaging conditions by 20%. Table 2 shows the irradiation dose of each experimental example in comparison with the irradiation dose under normal imaging conditions.
【００２９】[0029]
【表２】 [Table 2]
【００３０】実験例１０ 管電圧を通常の撮影条件での管電圧に対し１０％並びに
２０％増加して、実験例８、９と同様にＸ線画像を得
た。表２にその照射線量を通常の撮影条件での照射線量
と対比して示してある。実際上現在汎用しているものと
して、実験例８のフイルタ部材はＡｌ０．４１５ｍｍ、
Ｃｕ０．３１ｍｍで構成し、実験例９のフイルタ部材は
Ａｌ０．３０ｍｍ、Ｃｕ０．７０ｍｍで構成し、実験例
１０のフイルタ部材はＣｕ０．４０ｍｍ、Ａｇ０．２０
ｍｍで構成したものを各々用いて上述の結果を得た。無
論ここに用いたフイルタ構成要素自体は周知のものであ
る。Experimental Example 10 X-ray images were obtained in the same manner as in Experimental Examples 8 and 9, except that the tube voltage was increased by 10% and 20% with respect to the tube voltage under normal photographing conditions. Table 2 shows the irradiation dose in comparison with the irradiation dose under normal imaging conditions. Actually, the filter member of Experimental Example 8 is Al0.415 mm,
The filter member of Experimental Example 9 was composed of 0.30 mm of Al and 0.70 mm of Cu, and the filter member of Experimental Example 10 was composed of 0.40 mm of Cu and Ag 0.20 mm.
The results described above were obtained by using each of the components constituted by mm. Of course, the filter components used herein are well known.
【００３１】比較例９、１０並びに１１ 回転フイルタデイスクの使用を割愛した点を除き、上記
実験例８、９並びに１０と同様にＸ線画像を得た。表２
にそれらの照射線量を示してある。Comparative Examples 9, 10, and 11 X-ray images were obtained in the same manner as in Experimental Examples 8, 9, and 10, except that the use of a rotating filter disk was omitted. Table 2
Shows the irradiation doses.
【００３２】尚実験例８〜１０並びに比較例９〜１１に
おいて管電流は須らく１００ｍＡであつた。また表２に
おいて実験例８〜１０の照射線量比を、各比較例を１０
０として表してある。In Experimental Examples 8 to 10 and Comparative Examples 9 to 11, the tube current was about 100 mA. Table 2 shows the irradiation dose ratios of Experimental Examples 8 to 10, and Comparative Example 10
It is represented as 0.
【００３３】これらの実験例８〜１０並びに比較例９〜
１１の結果から明らかなように、管電圧を１０％あるい
は２０％に増大したにも拘わらず、照射線量は１／４〜
１／１１に激減した。These Experimental Examples 8 to 10 and Comparative Examples 9 to
As is clear from the results of FIG. 11, the irradiation dose was reduced to １ ／ to わ ら ず despite the increase in the tube voltage to 10% or 20%.
It dropped sharply to 1/11.
【００３４】総じて本発明においては特に実効エネルギ
の中心値を結ぶ線が垂直線に近付けば近付く程、概して
低エネルギ側、即ち図２で５０ｋｅＶ以下がカツトさ
れ、周知構成に比べ低エネルギレベルの照射線量をカツ
トでき、低エネルギのＸ線照射によつて引起こされると
考えられている放射線障害の罹病率を低減でき、人体障
害を効果的に抑止できることが理解されよう。In general, in the present invention, in particular, the closer the line connecting the center values of the effective energy to the vertical line, the lower the energy side, that is, 50 keV or less in FIG. It will be appreciated that the dose can be cut, the morbidity of radiation damage believed to be caused by low energy X-ray irradiation can be reduced, and human injury can be effectively suppressed.
【００３５】[0035]
【発明の効果】上述の本発明によるＸ線撮像方法によれ
ば高分解能をもつて撮像を実現し、正確な医療診断等に
充分に寄与し得る上、特に照射線量を顕著に低減するこ
とにより、患者、医師あるいは操作者等への被曝線量を
大巾に低下させて放射線障害の発生を有効に抑止できる
等々の効果を達成する。According to the above-mentioned X-ray imaging method of the present invention, it is possible to realize imaging with high resolution and sufficiently contribute to accurate medical diagnosis and the like, and particularly, to significantly reduce the irradiation dose. Therefore, the radiation dose to the patient, the doctor, the operator, or the like is greatly reduced, and the effects such as the occurrence of radiation damage can be effectively suppressed.
【図１】本発明によるＸ線撮像方法の全体構成を示す説
明図である。FIG. 1 is an explanatory diagram showing an overall configuration of an X-ray imaging method according to the present invention.
【図２】図１に表した撮像方法による場合のＸ線スペク
トル分布図である。FIG. 2 is an X-ray spectrum distribution diagram in the case of using the imaging method shown in FIG.
【図３】ａおよびｂは夫々図２に対照して示す本発明に
よらない撮像方法でのＸ線スペクトル分布図である。3A and 3B are X-ray spectrum distribution diagrams in an imaging method not according to the present invention, respectively, shown in contrast to FIG.
【図４】本発明による場合とよらない場合とを対照して
Ｘ線の焦点深度と撮像対象の厚さとの関係を示す模式図
である。FIG. 4 is a schematic diagram showing the relationship between the depth of focus of X-rays and the thickness of the imaging target, in contrast to the case according to the present invention.
【図５】本発明による場合とよらない場合とを対照して
Ｘ線の焦点深度と撮像対象の勾配との関係を示す模式図
である。FIG. 5 is a schematic diagram showing the relationship between the depth of focus of X-rays and the gradient of an imaging target in comparison with the case according to the present invention.
【図６】本発明のＸ線撮像方法における撮像対象の厚さ
と実効エネルギとの関係を示すグラフである。FIG. 6 is a graph showing the relationship between the thickness of the imaging target and the effective energy in the X-ray imaging method of the present invention.
【図７】本発明によらないＸ線撮像方法における撮像対
象の厚さと実効エネルギの関係を示すグラフである。FIG. 7 is a graph showing the relationship between the thickness of the imaging target and the effective energy in the X-ray imaging method not according to the present invention.
１０ システム １１ Ｘ線源 １２ 回転フイルタデイスク １３ａ…１３ｎ フイルタ部材 １４ 回転駆動部材 １５ Ｘ線制御装置 １６ フイルタ制御装置 １７ テーブル DESCRIPTION OF SYMBOLS 10 System 11 X-ray source 12 Rotary filter disk 13a ... 13n Filter member 14 Rotation drive member 15 X-ray controller 16 Filter controller 17 Table
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 昭62−103552（ＪＰ，Ａ) 実開 昭62−36704（ＪＰ，Ｕ) 実公 昭54−36625（ＪＰ，Ｙ２) 木村博一監修「最近の医用画像診断装 置」（株）朝倉書店 1988．６．25 ｐ 127〜ｐ128 岩井喜典編「ＣＴスキャナ−Ｘ線コン ピュータ断層撮影装置−」（株）コロナ 社 Ｓ54．２．20 ｐ35〜ｐ37 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-103552 (JP, A) JP-A 62-36704 (JP, U) JP-A 54-36625 (JP, Y2) supervised by Hirokazu Kimura Recent medical image diagnostic equipment ”Asakura Shoten Co., Ltd. 1988.6.25 p127-p128 Yoshinori Iwai“ CT Scanner-X-ray Computer Tomography Apparatus-”Corona Corporation S54.2.20 p35- p37
Claims (3)
フイルタと、対象物の高分解能Ｘ線撮像を実現する撮像
手段とよりなる医療用Ｘ線撮像システムにおけるビーム
ハードニング現象を低減する方法であつて、 ａ）０値から所定の最大値まで次第に増加する厚さで均
質の基準対象物と複数のフイルタ部材とを用意し、 ｂ）放射Ｘ線のエネルギ分布の低エネルギ側の部分をカ
ツトするように選択したフイルタ部材の一にＸ線を通過
せしめ、 ｃ）基準対象物に対してフイルタ部材と基準対象物を通
過したＸ線のエネルギ部分の実効エネルギの中心を決定
し、 ｄ）対象物の多様な厚さに対応する各実効エネルギ中心
間の差を決定するために基準対象物の異なる厚さ部分に
ついて得られたエネルギ部分の実効エネルギ中心を比較
し、 ｅ）基準対象物の異なる厚さの全範囲における実効エネ
ルギ中心間の差が基準対象物の最小厚さについての実効
エネルギ中心値の１０％以内である特定のフイルタ部材
を複数のフイルタ部材から選択するために前記工程ｂ）
〜ｄ）を繰り返し、 ｆ）前記の特定のフイルタ部材を使用して前記のＸ線撮
像を実現する工程よりなる方法。1. Beam hardening in a medical X-ray imaging system comprising an X-ray source, a filter disposed on the X-ray of the X-ray source, and imaging means for realizing high-resolution X-ray imaging of an object. A method for reducing the phenomenon, comprising: a) providing a uniform reference object and a plurality of filter members having a thickness gradually increasing from a zero value to a predetermined maximum value; and b) providing a low energy distribution of radiated X-rays. X-rays are passed through one of the filter members selected to cut the energy-side portion; c) the center of the effective energy of the energy portion of the X-rays passing through the filter member and the reference object relative to the reference object; D) comparing the effective energy centers of the energy portions obtained for different thickness portions of the reference object to determine a difference between each effective energy center corresponding to various thicknesses of the object; e. ) Standard target Selecting a particular filter member from the plurality of filter members in which the difference between the effective energy centers in the entire range of different thicknesses is within 10% of the effective energy center value for the minimum thickness of the reference object. b)
F) repeating the X-ray imaging using the specific filter member.
段と、陰極線管とを備える請求項１の方法。2. The method of claim 1, wherein the imaging means comprises a multiplier tube camera, an image processing means, and a cathode ray tube.
求項１の方法。3. The method of claim 1, wherein the imaging means comprises a film cassette.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3222535A JP2853065B2 (en) | 1990-05-25 | 1991-05-23 | X-ray imaging method |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13629890 | 1990-05-25 | ||
| JP2-136298 | 1990-05-25 | ||
| JP3222535A JP2853065B2 (en) | 1990-05-25 | 1991-05-23 | X-ray imaging method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0515519A JPH0515519A (en) | 1993-01-26 |
| JP2853065B2 true JP2853065B2 (en) | 1999-02-03 |
Family
ID=26469930
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3222535A Expired - Lifetime JP2853065B2 (en) | 1990-05-25 | 1991-05-23 | X-ray imaging method |
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| Country | Link |
|---|---|
| JP (1) | JP2853065B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4499593B2 (en) * | 2005-03-28 | 2010-07-07 | アロカ株式会社 | X-ray bone density measuring device |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS4999290A (en) * | 1973-01-27 | 1974-09-19 | ||
| DE2347178B2 (en) * | 1973-09-19 | 1975-09-18 | Siemens Ag, 1000 Berlin Und 8000 Muenchen | X-ray diagnostic apparatus |
| JPS5631535Y2 (en) * | 1977-08-15 | 1981-07-28 | ||
| JPH01126600A (en) * | 1987-11-12 | 1989-05-18 | Mitsubishi Electric Corp | Flattening filter apparatus for radiation |
-
1991
- 1991-05-23 JP JP3222535A patent/JP2853065B2/en not_active Expired - Lifetime
Non-Patent Citations (2)
| Title |
|---|
| 岩井喜典編「ＣＴスキャナ−Ｘ線コンピュータ断層撮影装置−」（株）コロナ社 Ｓ５４．２．２０ ｐ３５〜ｐ３７ |
| 木村博一監修「最近の医用画像診断装置」（株）朝倉書店 １９８８．６．２５ ｐ１２７〜ｐ１２８ |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0515519A (en) | 1993-01-26 |
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