JPH06105296B2 - Scattered ray correction method of ECT device - Google Patents
Scattered ray correction method of ECT deviceInfo
- Publication number
- JPH06105296B2 JPH06105296B2 JP61232452A JP23245286A JPH06105296B2 JP H06105296 B2 JPH06105296 B2 JP H06105296B2 JP 61232452 A JP61232452 A JP 61232452A JP 23245286 A JP23245286 A JP 23245286A JP H06105296 B2 JPH06105296 B2 JP H06105296B2
- Authority
- JP
- Japan
- Prior art keywords
- data
- scattered
- radiation
- correction
- filter function
- 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 title claims description 21
- 238000000034 method Methods 0.000 title claims description 10
- 230000005855 radiation Effects 0.000 claims description 27
- 238000001914 filtration Methods 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 2
- NMFHJNAPXOMSRX-PUPDPRJKSA-N [(1r)-3-(3,4-dimethoxyphenyl)-1-[3-(2-morpholin-4-ylethoxy)phenyl]propyl] (2s)-1-[(2s)-2-(3,4,5-trimethoxyphenyl)butanoyl]piperidine-2-carboxylate Chemical compound C([C@@H](OC(=O)[C@@H]1CCCCN1C(=O)[C@@H](CC)C=1C=C(OC)C(OC)=C(OC)C=1)C=1C=C(OCCN2CCOCC2)C=CC=1)CC1=CC=C(OC)C(OC)=C1 NMFHJNAPXOMSRX-PUPDPRJKSA-N 0.000 description 1
- NIXOWILDQLNWCW-UHFFFAOYSA-N acrylic acid group Chemical group C(C=C)(=O)O NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
- 238000002591 computed tomography Methods 0.000 description 1
- 238000013480 data collection Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Description
この発明は、放射線同位体（RI）で標識された化合物を
患者に投与して、その２次元的な分布を断層像として得
るECT装置（エミッション型コンピュータ断層撮影装
置）に関し、とくにその散乱線によって誤差を生じたデ
ータを補正する方法に関する。The present invention relates to an ECT device (emission-type computer tomography device) which obtains a two-dimensional distribution of a compound labeled with a radioisotope (RI) into a patient, and particularly by its scattered rays. The present invention relates to a method of correcting data having an error.
患者に投与された標識化合物から放出される放射線は、
患者身体内を通過して外部に出るため、身体内で吸収さ
れて減衰したり、散乱されて誤った情報を提供したりす
ることにもなる。これらを補正するための方法が種々模
索されているが、なかでも散乱線の補正法は確立されて
いず、いろいろと試みられている。 たとえば、PET（ポジトロンECT）の場合、リング状検出
器配列の中に、RIを含む部分と含まない部分とを有する
ファントムを配置し、１つのプロファイルデータをとっ
てみると、本来RIが存在しない部分にも散乱線のために
誤って得られたデータが存在していることが分る。そこ
で、従来では、RI不存在部分のデータが散乱線による誤
ったデータのみであるとして、この部分のデータの平均
値を求め、この平均値をプロファイルデータの全体から
一律に差し引き演算して散乱線補正することなどが行な
われている。The radiation emitted from the labeled compound administered to the patient is
As it passes through the patient's body to the outside, it may be absorbed and attenuated in the body, or scattered to provide erroneous information. Various methods for correcting these have been sought, but among them, a method for correcting scattered rays has not been established, and various methods have been tried. For example, in the case of PET (positron ECT), when a phantom having a portion containing RI and a portion not containing RI is arranged in the ring-shaped detector array and one profile data is taken, RI does not originally exist. It can be seen that there is data that was obtained erroneously due to scattered rays in the part as well. Therefore, in the past, assuming that the RI-free portion of the data is only erroneous data due to scattered rays, the average value of the data for this portion is calculated, and this average value is uniformly subtracted from the entire profile data to calculate scattered rays. Corrections are being made.
しかしながら、上記の従来の一例として示した補正法で
は、単に一定値を一律に差し引くというだけであるから
精度が悪いという問題がある。 また、スライス面（データ収集面）外にRIが分布する場
合、それに起因する散乱線成分によって誤差が生じ、こ
れが実際上大きな問題となっているが、この問題につい
ては全く無力である。 この発明は、スライス面内のRIによる散乱線成分だけで
なくスライス面外に分布するRIに起因する散乱線成分を
もあわせて見積もり、これらを補正することのできる、
ECT装置の散乱線補正法を提供することを目的とする。However, the correction method shown as the above-mentioned conventional example has a problem in that the accuracy is poor because the constant value is simply subtracted uniformly. Further, when RI is distributed outside the slice plane (data collection plane), an error occurs due to the scattered ray component caused by it, and this is actually a big problem, but this problem is completely powerless. This invention, not only the scattered ray component due to RI in the slice plane, but also the scattered ray component due to RI distributed outside the slice plane can be estimated together, and these can be corrected.
It is an object of the present invention to provide a scattered radiation correction method for an ECT device.
この発明によるECT装置の散乱線補正法では、断層像を
得ようとする面内で１点を占めるように線源を配置し、
この線源のデータを、周囲に散乱体がない状態と、周囲
に散乱体があり且つスライス面外にも線源が分布してい
る状態とについて収集し、これらのデータの間の関係か
ら散乱線補正用フィルタ関数を求め、実際の被写体につ
いて得られたデータに対してこのフィルタ関数を作用さ
せて散乱線の補正を行なうことを特徴とする。In the scattered radiation correction method of the ECT device according to the present invention, the radiation source is arranged so as to occupy one point in the plane to obtain a tomographic image,
The data of this radiation source was collected for the case where there were no scatterers in the surroundings and for the situation where there were scatterers in the surroundings and the radiation sources were distributed outside the slice plane, and the scattering between them was used to scatter. A feature is that a line-correction filter function is obtained, and this filter function is applied to data obtained for an actual subject to correct scattered rays.
点線源のデータを、周囲に散乱体がない状態と、周囲に
散乱体があり且つスライス面外にも線源が分布している
状態とについて収集すると、後者の場合はスライス面の
内外の線源に起因する散乱線によってぼけた像が得られ
るため、プロファイルデータも散乱線がない場合に比べ
てなまったものとなる。これらの両データの比をとって
みると、それを散乱線によってぼけたデータを本来のデ
ータに戻すためのデータとして使えることが分る。 そこで、この両データの比に基づき散乱線補正用フィル
タ関数を作成して、このフィルタ関数を実際の被写体の
データに作用させれば、スライス面内外の線源に起因す
る散乱線の補正をすることができる。When the data of the point source is collected for a state in which there are no scatterers in the surroundings and a state in which there are scatterers in the surroundings and the source is also distributed outside the slice plane, in the latter case the lines inside and outside the slice plane are Since a blurred image is obtained due to scattered rays originating from the source, the profile data is also blunt compared to the case without scattered rays. If you take the ratio of these two data, you can see that it can be used as data to restore the original data to the data blurred by scattered radiation. Therefore, if a scattered radiation correction filter function is created based on the ratio of these two data and this filter function is applied to the actual subject data, the scattered radiation caused by the radiation source inside and outside the slice plane is corrected. be able to.
PETに適用した一実施例について説明する。まず、第１
図のようにリング型のスライスシールド２の中に、この
スライスシールド２によって規定される断層面に垂直に
ライン状線源１を配置する。こうして断層面に点状線源
を置いたのと実質的に同じにする。リング型検出器配列
はスライスシールド２の外側に位置するがこの図では省
略している。ライン状線源１はGe-68により作製してあ
る。そしてこの状態で矢印で示した断層面につきデータ
収集を行ない、得られたサイノグラムをフーリエ変換し
て第２図に示すデータを得た。 つぎに、第３図に示すような、ライン状線源３の周囲に
散乱体４を有し、且つ背面側にRI部５を持つファントム
６を同様に配置する。このファントム６は全体の形状が
円柱状になるように形成されており、散乱体４は人体に
似た散乱特性を有する水やアルカリにより構成すればよ
いが、ここではアクリル製とした。また、ライン状線源
３とRI部５にはGe-68を用いた。RI部５のRI濃度はPET装
置で分解できる大きさに換算した場合のライン状線源３
と同程度の濃度としてある。このファントム６の矢印で
示す断層面に関するデータ収集を行なうと、線源３より
放出された放出線の一部が散乱体４で散乱するためデー
タにほけが加わり、さらに断層面外のRI部５からの放射
線もこの散乱体４で散乱してデータにぼけを生じさせる
ので、得られたサイノグラムのフーリエ変換後のデータ
は第５図のように低周波成分が増加したものとなる。 これら第２図および第５図に示したフーリエ変換後のデ
ータを、第５図のデータが散乱体４における吸収の影響
を受けていることを考慮して適当なスケーリングを行な
った後重ね合せれば第６図のようにほとんど重なり、低
周波部分で散乱線成分による差異が表われているに過ぎ
ない。そこで、これらフーリエ変化後のデータの比をと
ってみると、第７図のようなデータが得られる。 この第７図のデータは、散乱線によって誤差を含むよう
になったデータを元の誤差のない状態に戻すための補正
データとして考えることができる。そこで、第７図のデ
ータの近似曲線を求めて第８図のような散乱線補正用フ
ィルタ関数を作成する。 このようにして散乱線補正用フィルタ関数が得られた
ら、実際の被写体に関して収集されたプロファイルデー
タにこの関数を作用させてフィルタリングすれば、断層
面の内外に存在するRIに起因する散乱線の補正ができる
ことになる。この場合、画像再構成は、通常、プロファ
イルデータに対してフィルタリングした後このプロファ
イルデータを逆投影するというアルゴリズムで行なわれ
るので、そのフィルタリングに際して同時に上記の散乱
線補正用フィルタ関数を作用させればよく、こうするこ
とによって補正のために必要なデータ処理に要する時間
を短縮することができる。 なお、第３図、第４図に示したファントム６のRI部５の
形状やRI強度とオフエリア（実際にはRIの存在しない領
域）のカウント等を対応づけて、第８図の散乱線補正用
フィルタ関数を修正しておくことも望ましい。すなわ
ち、たとえばオフエリアのカウントが減算されるように
修正しておくことにより、より正確な補正が可能とな
る。An example applied to PET will be described. First, the first
As shown in the drawing, the line-shaped radiation source 1 is arranged in the ring-shaped slice shield 2 perpendicularly to the slice plane defined by the slice shield 2. In this way, it becomes substantially the same as placing a point source on the fault plane. The ring detector array is located outside the slice shield 2 but is omitted in this figure. The linear source 1 is made of Ge-68. Then, in this state, data was collected on the cross section indicated by the arrow, and the obtained sinogram was Fourier transformed to obtain the data shown in FIG. Next, as shown in FIG. 3, a phantom 6 having a scatterer 4 around the linear radiation source 3 and an RI portion 5 on the back side is similarly arranged. The phantom 6 is formed so as to have a cylindrical shape as a whole, and the scatterer 4 may be made of water or alkali having a scattering characteristic similar to that of a human body, but is made of acrylic here. Further, Ge-68 was used for the linear radiation source 3 and the RI part 5. The line source 3 when the RI concentration in the RI part 5 is converted to a size that can be decomposed by a PET device
The same concentration as When the data on the fault plane indicated by the arrow of the phantom 6 is collected, a part of the emission line emitted from the radiation source 3 is scattered by the scatterer 4, and the data is ghosted. Since the radiation from is also scattered by the scatterer 4 and blurs the data, the data after Fourier transform of the obtained sinogram has an increased low frequency component as shown in FIG. The Fourier-transformed data shown in FIGS. 2 and 5 are subjected to appropriate scaling in consideration of the fact that the data shown in FIG. For example, as shown in FIG. 6, they are almost overlapped with each other, and only the difference due to the scattered ray component is shown in the low frequency part. Then, when the ratio of the data after the Fourier change is taken, the data as shown in FIG. 7 is obtained. The data shown in FIG. 7 can be considered as correction data for returning the data including an error due to scattered radiation to the original error-free state. Therefore, an approximate curve of the data shown in FIG. 7 is obtained and a scattered radiation correction filter function as shown in FIG. 8 is created. Once the scattered ray correction filter function is obtained in this way, this function is applied to the profile data collected for the actual subject to perform filtering to correct the scattered rays caused by RI existing inside and outside the tomographic plane. You will be able to In this case, image reconstruction is usually performed by an algorithm of back-projecting the profile data after filtering the profile data, so that the above-mentioned scattered radiation correction filter function may be applied at the same time when performing the filtering. By doing so, the time required for data processing necessary for correction can be shortened. The shape and the RI intensity of the RI part 5 of the phantom 6 shown in FIGS. 3 and 4 are associated with the counts of off-areas (regions where RI does not actually exist), and the scattered radiation of FIG. It is also desirable to modify the correction filter function. That is, for example, by correcting the off-area count so as to be subtracted, more accurate correction becomes possible.
この発明にかかるECT装置の散乱線補正法によれば、ス
ライス面内だけでなくスライス面外に分布するRIから放
出される放射線の散乱による誤差を補正することができ
る。また、補正用データは１度だけ収集しておけばよ
く、各被写体毎に、その都度補正用データ収集するとい
う時間や手間がかかることがない。しかも、そのために
特別な装置を必要とすることもなく安価で、簡便に補正
用データを得ることができる。さらに、補正用データを
用いて実際の被写体のデータを補正するデータ処理を短
時間で行なうことができる。According to the scattered radiation correction method of the ECT apparatus according to the present invention, it is possible to correct an error due to scattering of radiation emitted from RI distributed not only inside the slice plane but also outside the slice plane. Further, the correction data only needs to be collected once, and the time and labor for collecting the correction data for each subject is not required. Moreover, no special device is required for that purpose, and the correction data can be obtained easily at low cost. Further, the data processing for correcting the actual object data using the correction data can be performed in a short time.
第１図乃至第８図はこの発明の一実施例を説明するため
のもので、第１図はライン状線源の散乱体のない状態で
のデータを収集することを示す模式図、第２図は第１図
で得られたサイノグラムのフーリエ変換後のデータを示
すグラフ、第３図はライン状線源の周囲に散乱体があり
且つスライス面外にRIが分布している状態でのデータを
収集することを示す模式図、第４図はファントムの正面
図、第５図は第３図で得られたサイノグラムのフーリエ
変換後のデータを示すグラフ、第６図は第２図と第５図
のデータを重ね合せたグラフ、第７図は第２図および第
５図のデータの比を示すグラフ、第８図は散乱線補正用
フィルタ関数を表わすグラフである。 １……リング型スライスシールド １、３……ライン状線源、４……散乱体 ５……RI部、６……ファントムFIGS. 1 to 8 are for explaining one embodiment of the present invention, and FIG. 1 is a schematic view showing collecting data of a linear radiation source in a scatter-free state, and FIG. The figure is a graph showing the data after Fourier transform of the sinogram obtained in Fig. 1, and Fig. 3 is the data in the state where there are scatterers around the line source and RI is distributed outside the slice plane. FIG. 4 is a front view of the phantom, FIG. 5 is a graph showing data after Fourier transform of the sinogram obtained in FIG. 3, and FIG. 6 is FIG. 2 and FIG. FIG. 7 is a graph showing the ratio of the data shown in FIGS. 2 and 5, and FIG. 8 is a graph showing the scattered radiation correction filter function. 1 ... Ring type slice shield 1, 3 ... Line source, 4 ... Scatterer 5 ... RI part, 6 ... Phantom
Claims (1)
ように線源を配置し、この線源のデータを、周囲に散乱
体がない状態と、周囲に散乱体があり且つスライス面外
にも線源が分布している状態とについて収集し、これら
のデータの間の関係から散乱線補正用フィルタ関数を求
め、実際の被写体について得られたデータに対してこの
フィルタ関数を作用させて散乱線の補正を行なうことを
特徴とするECT装置の散乱線補正法。1. A radiation source is arranged so as to occupy one point in a plane where a tomographic image is to be obtained, and data of this radiation source is used in a state where there is no scatterer in the surroundings and when there is a scatterer in the surroundings. The state where the radiation source is distributed outside the slice plane is also collected, the filter function for scattered radiation correction is obtained from the relationship between these data, and this filter function is applied to the data obtained for the actual subject. A method for correcting scattered rays in an ECT device, which is characterized by causing it to correct scattered rays.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61232452A JPH06105296B2 (en) | 1986-09-30 | 1986-09-30 | Scattered ray correction method of ECT device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP61232452A JPH06105296B2 (en) | 1986-09-30 | 1986-09-30 | Scattered ray correction method of ECT device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS6385482A JPS6385482A (en) | 1988-04-15 |
| JPH06105296B2 true JPH06105296B2 (en) | 1994-12-21 |
Family
ID=16939504
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP61232452A Expired - Lifetime JPH06105296B2 (en) | 1986-09-30 | 1986-09-30 | Scattered ray correction method of ECT device |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH06105296B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8971405B2 (en) | 2001-09-18 | 2015-03-03 | Microsoft Technology Licensing, Llc | Block transform and quantization for image and video coding |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5140810B2 (en) * | 2005-09-28 | 2013-02-13 | 財団法人ヒューマンサイエンス振興財団 | Tomographic image overlay display method and computer program for displaying tomographic images superimposed |
| JP2007218769A (en) * | 2006-02-17 | 2007-08-30 | Shimadzu Corp | Nuclear medicine imaging device |
| JP6281640B2 (en) * | 2014-07-03 | 2018-02-21 | 株式会社ニコン | X-ray apparatus, image forming method, structure manufacturing method, and structure manufacturing system |
-
1986
- 1986-09-30 JP JP61232452A patent/JPH06105296B2/en not_active Expired - Lifetime
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8971405B2 (en) | 2001-09-18 | 2015-03-03 | Microsoft Technology Licensing, Llc | Block transform and quantization for image and video coding |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6385482A (en) | 1988-04-15 |
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