WO2004098373A2 - Procede pour reduire des perturbations causees par des artefacts - Google Patents

Procede pour reduire des perturbations causees par des artefacts Download PDF

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Publication number
WO2004098373A2
WO2004098373A2 PCT/EP2004/004650 EP2004004650W WO2004098373A2 WO 2004098373 A2 WO2004098373 A2 WO 2004098373A2 EP 2004004650 W EP2004004650 W EP 2004004650W WO 2004098373 A2 WO2004098373 A2 WO 2004098373A2
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WO
WIPO (PCT)
Prior art keywords
projection
image
artifact
artifacts
sectional image
Prior art date
Application number
PCT/EP2004/004650
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German (de)
English (en)
Other versions
WO2004098373A3 (fr
Inventor
Erwin Keeve
Lutz Ritter
Marc Lievin
Original Assignee
Stiftung Caesar
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 Stiftung Caesar filed Critical Stiftung Caesar
Publication of WO2004098373A2 publication Critical patent/WO2004098373A2/fr
Publication of WO2004098373A3 publication Critical patent/WO2004098373A3/fr

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Classifications

    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T11/00—2D [Two Dimensional] image generation
    • G06T11/003—Reconstruction from projections, e.g. tomography
    • G06T11/005—Specific pre-processing for tomographic reconstruction, e.g. calibration, source positioning, rebinning, scatter correction, retrospective gating

Definitions

  • the invention relates to a method for reducing interference caused by artifacts.
  • the invention relates to the use of this method in jaw and tooth examinations.
  • sectional images of an object can be generated.
  • a number of X-ray examinations are carried out from different angles.
  • an X-ray source is rotated around a human head.
  • a cross section i.e. a computed tomography image of a plane is generated by the so-called back projection of the data obtained.
  • Rear projection methods are described, for example, in F. Natterer, "The Mathematics of Computerized Tomography", New York: Wiley, 1986 and in W.208 et al., "Reduction of CT Artifacts Caused by Metallic Implants", Radiology, vol. 164, No. 2, Aug. 1987, pp. 576-577.
  • the area to be recorded by a computed tomography image is an area with a comparatively high density compared to conventional tissue, bones or teeth
  • the X-rays or other suitable examination beams in these areas are attenuated more than in the surrounding areas comparatively soft areas, the bones, the teeth etc.
  • the denser areas are, for example, tooth fillings made of metal. Because of the strong Attenuation of the radiation caused by such artifacts creates gaps in the image projection. This artifact creates stripes in the image projection. A lot of information is lost within these strips. The image quality in the area of the artifacts and in particular the stripes produced is so bad that reliable medical conclusions can no longer be drawn.
  • filtered back projection Another method of improving the image data is the filtered back projection, which is implemented in conventional computed tomography scanners. With the help of an algorithm, the raw data are filtered in a suitable filter and the filtered data is then projected back from the frequency range into the 2D image area.
  • this method is limited by the number of projection angles. Such a method is described, for example, in F. Natterer, "The Mathematics of Computerized Tomography", New York: Wiley, 1986.
  • the object of the invention is to provide a method for reducing artifact-induced interference in medical-technical sectional images, in particular computer tomography sectional images, by means of which the quality of the sectional images is improved.
  • a sectional image projection of a sectional image is generated using known methods, in particular computer tomography, the sectional image projection being, for example, the corresponding sinogram or the raw data.
  • the artifacts such as the metal fillings in teeth, are detected. The detection is preferably carried out automatically.
  • An artifact projection, ie in particular the raw data of the artifacts, is generated on the basis of the detected artifacts.
  • the sectional image projection is linked to the artifact projection. This creates a reduced projection, which is essentially reduced by the artifacts.
  • a particularly filtered projection of the reduced projection into a reduced sectional image In the reduced sectional image, the artifacts and the disruptive strips caused by them, which result in loss of information, are at least reduced. The interfering strips are preferably completely eliminated. As a result, the quality of the sectional image generated is considerably improved.
  • the slice image projection is preferably linked to the artifact projection by a subtraction method.
  • the individual pixels of the two projections corresponding to one another are subtracted from one another, in particular the artifact projection being subtracted from the sectional image projection.
  • a reduced projection is obtained which has at least significantly less interference in the form of stripes.
  • a complete removal of the disturbances caused by the artifacts can be achieved.
  • This is preferably possible by, for example, multiplying the individual pixels of the artifact projection by a factor before subtracting them from the individual pixels of the sectional image projection.
  • This factor can be determined empirically in particular. This factor is preferably 0.05 to 0.2 and particularly preferably approximately 0.1 in the case of sectional images of jaws in which the disturbances are caused by metal deposits in the teeth.
  • the artifact projection is generated in that the artifacts are detected in the original sectional image and then an artifact image is generated.
  • the artifact image is, for example, an image of the tooth fillings.
  • the artifact image is then projected to obtain the artifact projection.
  • the detection is preferably carried out using an automatic detection method. This can be done, for example, using image recognition methods.
  • the automatic detection is particularly preferably carried out by the fact that at each individual pixel or a group of pixels Intensity is determined. Since metal artifacts in particular strongly attenuate the radiation, the values in the area of the artifacts are minimal. All pixels or groups of pixels with minimal values are therefore highly likely to be part of an artifact.
  • the generated artifact image is preferably inserted into the reduced sectional image in order to generate a corrected sectional image.
  • the artifact projection is linked to the sectional image projection in order to generate a twice corrected projection.
  • the previously generated corrected sectional image is preferably also integrated into the linkage in order to further improve the result.
  • the double-corrected projection produced by the link is then reprojected to produce a double-corrected sectional image.
  • the method can also be used in particular with joint prostheses, such as hip prostheses and the like.
  • Other areas of application include the examination of spinal scoliosis and bone treatments using metal implants.
  • 1 is a sectional view A and a sectional image projection A ', 2 shows an artifact image B and an artifact projection B ',
  • a two-dimensional sectional image A (FIG. 1) is generated, for example, by computer tomography.
  • an X-ray source is rotated around a human head so that a sectional image A is generated.
  • the sectional image A is generated by a filtered back-projection of the sectional image projection A 'obtained in computer tomography.
  • Such a rear projection method is described, for example, in F. Natterer, "The Mathematics of Computerized Tomography", New York: Wiley, 1986.
  • the sectional image projection A ' is therefore a projection of the two-dimensional original image A of a computer tomography, a corresponding sinogram or the corresponding raw data.
  • the basically identical sectional images A can be generated by a parallel, a conical or a fanned beam path of the X-rays. Of course, it can also be other images that are not generated with the aid of computer tomography, but, for example, other imaging devices, in particular three-dimensional dental imaging devices.
  • metal fillings 10, ie artifacts, present in the patient's dentition cause strips 12 in the sectional view A.
  • the artifacts 10 are detected in the sectional image A. This can be done manually.
  • the distribution assessment is based, for example, on the fact that the metal fillings attenuate the X-rays more than those of meat, bones or teeth.
  • the metal areas cause black or dark areas in the sinograms and white or light areas in the images.
  • the distribution of all values of the raw data is recorded. This is done, for example, as can be seen from the diagram shown in FIG. 6, by entering the intensity of the individual values on the abscissa and their frequency on the ordinate.
  • the lowest value indicated by arrow 16 is the value caused by the metal artifacts.
  • the artifacts 10 can be localized automatically by this method. This creates the artifact image B (FIG. 2).
  • the artifact image B is converted into the associated artifact projection B '.
  • lines 14 caused by the individual artifacts 10 can be seen, which produce the stripes 12 in the sectional image A (FIG. 1).
  • Radon transformation means a set of polar projections of an image.
  • the Radon transformation is an algorithm technique that projects the reconstructed image back to the original raw data generated by the scanner.
  • the sectional image projection A '(FIG. 1) is linked to the artifact projection B' (FIG. 2). It is particularly preferred here to subtract the data. In this case, for example, a pixel-by-pixel value of the artifact projection B 'becomes the corresponding value of the sectional image projection A' subtracted. It is particularly preferred here to multiply the value of the artifact projection B 1 by a factor in order to improve the result. This factor is an empirically determined value, which is preferably in the range of 0.1.
  • the linkage produces a reduced projection C (FIG. 3).
  • the reduced sectional image C is generated from the reduced projection C by a suitable filtered rear projection.
  • a suitable method for filtered rear projection is, for example, also in W.
  • the artifact image B (FIG. 2) is preferably inserted into the reduced sectional image C (FIG. 3).
  • the insertion takes place in particular by adding the corresponding data.
  • a corrected sectional image D (FIG. 4) is generated.
  • the insertion of the artifact image B essentially has the advantage that the intensity level of the reconstructed image is retained.
  • the corrected sectional image D into a corrected projection D '(FIG. 4) using the Radon transformation in a further optional method step.
  • the corrected projection D 'generated in this way is linked to the sectional image projection A' (FIG. 1) in order to produce a twice corrected projection E '(FIG. 5).
  • the image projections D 'and A' are linked, for example, by a suitable algorithm.
  • the function f can be any interpretation function, the following function being preferred according to the invention:
  • x is an element of the sonogram
  • ⁇ is an overlap of the boundary between the original sonogram and the metal sonogram
  • G is an interpolation function, for example according to the Gaussian Kernel.
  • the resulting sinogram or the twice corrected projection E ' is an interpolation between the original and the corrected sinogram. Therefore, the projection E 'contains all relevant information, the negative effect of the metal fillings or the like being eliminated. Without interpolation, boundaries between the original and the corrected sinogram would not correspond to one another. This can lead to the creation of new artifacts during the filtered back projection.
  • the twice corrected projection E ' is then converted into the twice corrected sectional image E by a filtered back projection.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Theoretical Computer Science (AREA)
  • Apparatus For Radiation Diagnosis (AREA)
  • Magnetic Resonance Imaging Apparatus (AREA)

Abstract

L'invention concerne un procédé pour réduire des perturbations (12) causées par des artéfacts (10) dans des images en coupe médico-techniques produites notamment par tomodensitométrie, une projection d'image en coupe (A') étant réalisée dans une première étape de ce procédé. Ledit procédé consiste ensuite à détecter les artéfacts (10) pour réaliser une projection d'artéfacts (B'), à réaliser une projection réduite (C') en combinant la projection d'image en coupe (A') et la projection d'artéfacts (B') puis à produire une image en coupe réduite (C), dans laquelle les perturbations (12) sont sensiblement réduites, par rétroprojection de la projection réduite (C').
PCT/EP2004/004650 2003-05-07 2004-05-03 Procede pour reduire des perturbations causees par des artefacts WO2004098373A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE10320233.1 2003-05-07
DE2003120233 DE10320233B4 (de) 2003-05-07 2003-05-07 Verfahren zur Reduzierung von durch Artefakte hervorgerufene Störungen

Publications (2)

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WO2004098373A2 true WO2004098373A2 (fr) 2004-11-18
WO2004098373A3 WO2004098373A3 (fr) 2005-03-31

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DE (1) DE10320233B4 (fr)
WO (1) WO2004098373A2 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
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WO2010052615A2 (fr) * 2008-11-07 2010-05-14 Koninklijke Philips Electronics N.V. Extraction d'informations de mouvement

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DE102005028225A1 (de) * 2005-06-17 2007-05-24 Siemens Ag Vorrichtung und Verfahren für die Computertomographie
DE102005044407A1 (de) * 2005-09-16 2007-03-22 Siemens Ag Verfahren zur artefaktreduzierten radiologischen 3D-Bildgebung, Medizinische Bildgebungsvorrichtung und Verfahren zur Erstellung eines Therapieplans
DE102008038357B3 (de) * 2008-08-19 2010-01-14 Siemens Aktiengesellschaft Verfahren zur Erzeugung von 2D-Schnittbildern aus 3D-Projektionsdaten, die mittels eines CT-Systems von einem metallische Anteile enthaltenden Untersuchungsobjekt erfasst wurden
DE102008045449B4 (de) * 2008-09-02 2016-03-31 Siemens Aktiengesellschaft Verfahren zur Erstellung von computertomographischen Aufnahmen eines Patienten mit metallischen Anteilen und Computersystem zur Durchführung des Verfahrens
DE102012219269A1 (de) 2012-10-22 2014-05-08 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Verfahren und Vorrichtung zum Erzeugen einer dreidimensionalen Abbildung eines Objekts

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US5243664A (en) * 1991-09-16 1993-09-07 Picker International, Inc. Post-processing technique for reducing metallic clip artifacts in CT images

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US4897788A (en) * 1988-04-18 1990-01-30 General Electric Company Image correction for computed tomography to remove crosstalk artifacts
EP0857337B1 (fr) * 1996-07-30 2002-12-11 Koninklijke Philips Electronics N.V. Correction des artefacts annulaires dans une image
DE19823597A1 (de) * 1998-05-27 1999-12-02 Deutsches Krebsforsch Verfahren zur Rausch- und Artefaktreduktion bei digitalen Subtraktionsbildverfahren

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US5243664A (en) * 1991-09-16 1993-09-07 Picker International, Inc. Post-processing technique for reducing metallic clip artifacts in CT images

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Title
LAIGAO CHEN ET AL: "A Novel method for reducing high-attenuation object artifacts in CT reconstructions" PROCEEDINGS OF THE SPIE, SPIE, BELLINGHAM, VA, US, Bd. 4684, 2002, Seiten 841-850, XP002298823 ISSN: 0277-786X *
PATH M; ZOLLIKOFER C P E; STUCKI P: "New approaches in CT artifact suppression-a case study in maxillofacial surgery" PROCEEDING OF 12TH INTERNATIONAL SYMPOSIUM ON COMPUTER ASSISTED RADIOLOGY AND SURGERY - 24-27 JUNE 1998 - TOKYO, JAPAN, 27. Juni 1998 (1998-06-27), Seiten 830-835, XP008041624 NETHERLANDS *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2010052615A2 (fr) * 2008-11-07 2010-05-14 Koninklijke Philips Electronics N.V. Extraction d'informations de mouvement
WO2010052615A3 (fr) * 2008-11-07 2011-05-12 Koninklijke Philips Electronics N.V. Extraction d'informations de mouvement

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Publication number Publication date
WO2004098373A3 (fr) 2005-03-31
DE10320233A1 (de) 2004-12-02
DE10320233B4 (de) 2012-11-08

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