WO2015010913A1 - Détermination de propriétés de focalisation - Google Patents

Détermination de propriétés de focalisation Download PDF

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Publication number
WO2015010913A1
WO2015010913A1 PCT/EP2014/064786 EP2014064786W WO2015010913A1 WO 2015010913 A1 WO2015010913 A1 WO 2015010913A1 EP 2014064786 W EP2014064786 W EP 2014064786W WO 2015010913 A1 WO2015010913 A1 WO 2015010913A1
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WO
WIPO (PCT)
Prior art keywords
detection
sub
ray
radiation
ray detector
Prior art date
Application number
PCT/EP2014/064786
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German (de)
English (en)
Inventor
Daniel NIEDERLÖHNER
Bodo Reitz
Stefan Wirth
Original Assignee
Siemens Aktiengesellschaft
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Publication of WO2015010913A1 publication Critical patent/WO2015010913A1/fr

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Classifications

    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
    • G21K1/00—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating
    • G21K1/02—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating using diaphragms, collimators
    • G21K1/025—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating using diaphragms, collimators using multiple collimators, e.g. Bucky screens; other devices for eliminating undesired or dispersed radiation
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
    • A61B6/02—Devices for diagnosis sequentially in different planes; Stereoscopic radiation diagnosis
    • A61B6/03—Computerised tomographs
    • A61B6/032—Transmission computed tomography [CT]
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
    • A61B6/40—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment with arrangements for generating radiation specially adapted for radiation diagnosis
    • A61B6/4021—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment with arrangements for generating radiation specially adapted for radiation diagnosis involving movement of the focal spot
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
    • A61B6/42—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment with arrangements for detecting radiation specially adapted for radiation diagnosis
    • A61B6/4291—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment with arrangements for detecting radiation specially adapted for radiation diagnosis the detector being combined with a grid or grating

Definitions

  • the present invention relates to a scattered radiation grid for an X-ray detector, a method for producing a scattered radiation grid, an X-ray detector system, a method for detecting X-ray radiation and a method for controlling and / or regulating the focus characteristics of an X-ray source.
  • X-ray imaging system such as the aforementioned service interventions occur, but also inadvertently, for example, dynamically, during operation of the X-ray imaging system.
  • the X-ray source In the operation of the X-ray source, there is usually a heating of components, in particular the X-ray source.
  • the geometrical arrangement of the anode of the X-ray source to the cathode can thereby change, so that focal properties such as the position / position and possibly also the shape or extent of the focal point of the X-ray source are changed by heating of components.
  • a dynamic change may also be caused by moving components of the x-ray imaging system, such as the rotation of the cathode of the radiation source. This dynamic change of focus characteristics also leads to the mentioned artifacts in imaging.
  • the object of the present invention is to provide a means of detecting this change in focus characteristics, and in particular to provide the ability to minimize the effect of changing focus characteristics on X-ray imaging.
  • the invention is based on the realization that insbeson ⁇ particular, the timely accurate knowledge of focus characteristics can be used to improve X-ray imaging, and it already can therefore be sufficient to detect a change of focus characteristics in order to obtain the desired precise knowledge and to effectively minimize artifacts in the imaging.
  • a scattered radiation grid for an X-ray detector with a number of grid cells is proposed.
  • Such a scattered radiation grid is also referred to as so-called “anti-scattergrid" or "ASG" for short.
  • the grid cells comprise boundary surfaces, with surface sections which delimit a respective passageway for X-radiation substantially parallel to a passage direction for X-ray radiation through the passageway.
  • substantially parallel to a direction of passage is to be interpreted to mean that at least two Begren ⁇ -cutting edge of the boundary surfaces lie in a plane which is parallel to the passage direction;.
  • Preferable han ⁇ it punched thereby to planar boundary surfaces the direction of passage is In this case, X-ray radiation in straight propagation can penetrate the scattered radiation grid without attenuation caused by the grid, that is to say by the propagation direction of an X-ray quantum which, without interaction with the grid, encompasses the grid within one through an edge line of the grid
  • Area in particular through the passageway, can happen.
  • the ASG according to the invention additionally comprises a shading device, which is arranged between and / or over the boundary surfaces.
  • the shading device serves for partial shading of the passage channel with respect to X-radiation, which is irradiated in the direction of passage on the scattered radiation grid. That is to say, the term "over the boundary surfaces” is to be understood below as meaning that the shading device is at least partially upstream of the boundary surfaces in the path of the x-ray radiation determined by the passage direction (ie so that the boundary surfaces later in time in the continuation of the path of the x-radiation in the direction of passage from an X-ray quantum of X-ray radiation would be passed as the shading device).
  • the invention also relates to a method for producing a scattered radiation grid according to the invention, wherein the grid ⁇ ter with a so-called “selective laser melting” method, preferably in one piece.
  • the shading device can be used to determine the focal properties mentioned at the outset, such as the shape, extent and position or position of a focal point in an X-ray source. If these properties are known, these can be taken into account in particular in the reconstruction of image data, so that the effects of a change of focus properties on the X-ray imaging are minimized. In addition, there is also the possibility to actively suppress the change of focus properties.
  • An X-ray detector of the X-ray detector system comprises a number, in particular a plurality, of detection units for generating a detection signal for X-radiation incident on the detection unit.
  • a detection unit is also abbreviated as "pixel" of the detector be ⁇ distinguishes this case, at least one of the Detektionseinhei ⁇ th includes several sub-detection units to generate a sub-detection signal for a sub-detection surface of each ⁇ vantage sub-detection unit incident X-rays.
  • the sub-detection units are also referred to below as sub-pixels, in which case several or all of the sub-detection signals may belong to the mentioned, in particular common
  • Detection signal are generated, which is generated by the pixel.
  • the X-ray detector according to the invention also has a shading device associated with the detection unit equipped with a plurality of sub-pixels, which is arranged in particular at a distance from the sub-detection surface and provides one or more of the sub-detection surfaces, in particular perpendicular, in the direction of the sub-detection surfaces irradiated X-radiation at least partially shields.
  • shielding means that one or more of the sub-detection surfaces are at least partially shadowed from the x-ray radiation (i.e., irradiated with reduced intensity against a same pixel without the shading device).
  • the x-ray detector may preferably also have the shading device in the form of the scattered radiation grid according to the invention.
  • the extension of the sub-detection areas is preferably less than the smallest cross-section of the passage of the scattered radiation grid, so meh ⁇ eral sub-pixels encompassed by a common grid cell of the scattering ⁇ radiation grid or be enclosed by a border line of Git ⁇ terzelle.
  • An inventive X-ray imaging system in particular computed tomography system comprising such a door system Röntgendetek-, which also includes an X-ray source on ⁇ .
  • the shading device With the aid of the shading device according to the invention, it is possible to generate a shading or shielding of sub-pixels of the X-ray detector, which makes possible a retroactive calculation to the mentioned focus characteristics of the X-ray radiation source, in particular using, ie on the basis of, several of the sub-detection signals.
  • the shading device in particular the scattered radiation grid
  • the shading device can be firmly connected to the X-ray detector or these components can be integrated in the X-ray detector.
  • the structure of the stray radiation grid ⁇ and / or the X-ray detector can be enhanced, which in turn for reducing mechanical vibration tions of the X-ray detector in operation and thus can lead to a further improvement of the X-ray imaging.
  • the shading device or the scattered radiation grating is preferably always in the beam path between the X-ray source and the X-ray detector.
  • the evaluation of using the shading device modified distributions of X-rays or the sub-detection signals is always possible. In particular, this also applies during the acquisition of X-ray projection data for
  • the invention thus also relates to a method for the detection of X-ray radiation using such an X-ray detector system, so that, in particular, the sub-detection signals offer the possibility of determining the mentioned focal properties.
  • the effects of the dynamic change of focus characteristics can be minimized with a method according to the invention for controlling and / or regulating the focus characteristics of an X-ray source.
  • the control and / or regulation of the above-mentioned focus characteristics of an X-ray source is performed using an X-ray detector system according to the invention on the basis of the sub-detection signal and / or the detection signal.
  • deflection magnetic fields can be used to control the position of the
  • X-ray focus ie the focus point controlled and / or gere ⁇ gel.
  • control and / or regulation can take place using geometry data of the x-ray focus, which are generated on the basis of the sub-detection signal and / or the detection signal.
  • the X-ray imaging system therefore preferably also comprises a correction data determination unit, which is designed for determining correction data for one X-ray source for the correction of focus characteristics, and a control device which controls the focal point of an X-ray source on the basis of the correction data determined by the determination unit Cor ⁇ rektur schemes.
  • the knowledge of focus characteristics can also be used in a method for generating image data from the interior of an examination subject.
  • the invention includes such a method wherein emitted gendetektors with a Röntgenstrahlungsquel ⁇ le X-rays toward the X-ray according to the invention and etechnischsquel of the X-ray detector X-ray data, in particular, usually also as raw data call ⁇ te Röntgenproj, one arranged between the X-ray source and the X-ray detector examination object are detected, it Geo ⁇ metrie schemes to shape and / or position of the focus of the X-ray source are then determined based, and a reconstruction of image data based on the X-ray data taking into account the geometry data.
  • X-ray data and geometry data can be stored in a common data set that is used for image reconstruction.
  • the X-ray image comprises dozensssystem, also perform an image reconstruction means which is adapted to using the aforementioned Geo ⁇ metriechal and the X-ray data, image reconstruction of an image from the interior of an object under examination fürzu ⁇ .
  • the shading device is particularly preferably a flat shading device, which can also be slightly bent. That is, the shading device is a flat side and a transverse side to narrow ⁇ can be assigned. In particular, the shading device can have a height in the direction of the narrow side, between the flat sides of 1 mm or less. The greater flat side of the shading device than the narrow side, in which the detector system is arranged and aligned substantially parallel to a sub-detection surface.
  • the shading device may in particular be a pinhole or an elongate web or webs, the hole or webs having a diameter or a width (transverse to a longitudinal direction of the elongated webs) of 100 ⁇ m or less.
  • the detection surface formed of a combination of sub-detection areas of a pixel may preferably be formed from egg ⁇ nem directly absorbing semiconductor material, such that a cost-effective production of the detection unit connected to a high spatial resolution in the detection of X-rays is possible. For the purpose of determining focus characteristics, this is a very easy to produce combination. However, according to the invention, it is not impossible to use, for example, a detection unit which has a scintillator and a photodiode associated with the scintillator.
  • the shading device is arranged such that upon irradiation of X-ray radiation in the direction of the detection surface by the shading device, processing means an X-ray shadow is generated on a plurality of, in particular adjacent sub-detection areas of a pixel.
  • a passage direction of the passage channel can be oriented perpendicular to a sub-detection surface.
  • the abovementioned shading of a plurality of sub-detection surfaces, preferably with perpendicular irradiation of X-radiation in the direction of the sub-detection surface occur.
  • the present invention can be particularly used against ⁇ geous for the detection of dynamic changes of focus characteristics.
  • the shading device initially causes an X-ray shadow only on a first of the sub-detection surfaces of the detection unit and, after a dynamic change of focus, at least partially shadows other, in particular several, preferably adjacent, sub-detection surfaces from the X-ray radiation are.
  • This change in the shadowing of the sub-detection areas can then be detected in a simple manner by analyzing the sub-pixel detection signals of the shadowed pixel, so that it is recognized that focus properties have changed.
  • an analysis for the image of the X-ray focus on the detection surface can be carried out in a similar manner.
  • ⁇ occur in the situation that the focus produces an X-ray image is initially set to a first sub-detection surface of the Detekti ⁇ onsaku and after a dynamic change in the focus others, in particular a plurality of sub-detection areas at least partially with the image of the focus, so X-rays are illuminated.
  • this change can be detected and detected by analyzing the subpixel detection signals.
  • at least two of the detection units of the x-ray detector are each assigned a separa ⁇ te shading device.
  • at least two of the grid cells of the ASG can each be assigned a separate shading device for this purpose.
  • the at least two shading devices which are at least present in these cases are preferably designed differently from one another.
  • one of the two shading devices may be a pinhole and the other may be a bar or another modification.
  • the accuracy of the detection of changes in focus properties can be drastically improved. For example, stereotactic information about the focus image or an X-ray shadow can be obtained with a plurality of shading devices.
  • the detector system has a detection signal analysis device for generating geometry data.
  • the geometry data can be used to determine the focus characteristics of an X-ray source which emits the X-radiation incident on the detector and in particular on the shadowed detection unit with a plurality of sub-pixels.
  • the detection signal analysis device can work by using the detection signal and / or using the sub-detection signals to determine the geometry data.
  • the geometry data comprise the data on the mentioned focal properties, that is, for example, shape, position or extent of the focal point of the X-ray source and / or data that allow a retroactive calculation of the said focal properties.
  • the geometry data may include such things as “elliptical,””circular,””asymmetric,” or “symmetrical.”
  • the location of the focal point can in particular as one or more coor dinates ⁇ be expressed in a suitable coordinate system, and as geometry data, which indicate the extent of the focus point, and relative or absolute distance and / or area dimensions may be used.
  • a Rotati ⁇ onswinkel an example elliptical focal point may be included in the geometry data.
  • the geometry data may include data on a geometric centroid of an x-ray intensity and / or an x-ray shadow (i.e., the distribution of x-ray intensity or x-ray shadow) that is determined similar to a gamma camera based on a plurality of sub-detection signals.
  • the geometry data may include data about the length and location of the major axes of the ellipse.
  • the geometry data also includes information about asymmetries of the focus point.
  • the geometrical data may also include information as to whether the detection signals or sub-detection signals have a deviation from a predetermined desired value, a desired shape, position and extent of the focal point repre ⁇ sentieren.
  • the detection signals or sub-Detek ⁇ tion signals itself be construed as geometry data. This is the case in particular if there is the possibility of analyzing a deviation from a predefined setpoint value, ie setpoint values are predetermined.
  • the geometry data are determined on the basis of reference data.
  • the reference data may in particular comprise one or more of the setpoint values for a detection signal or sub-detection. tion signal include.
  • the reference data preferably also contain information about a tolerable deviation from the setpoint values, that is to say in particular with respect to the setpoint values which are predetermined for the detection signal or the subdetection signal (s) of the shadowed pixel.
  • the change of the detection signal from the reference value may be included, for example, in correction data used to control X-ray focussing properties.
  • the determination of the geometry data and in particular the associated determination of a detection signal or sub-detection signal is preferably carried out repeatedly in order to perform, as mentioned, in particular a control or regulation of focus properties and / or, for example, a reconstruction of image data of the examination object on the basis of the X-ray data and the geometry data.
  • the repeated determination of geometric data can be repeated in a time interval of lOOys and more, preferably up to 1000ys.
  • This interval is shorter than ty ⁇ european time intervals for dynamic changes of Detek ⁇ toreigenschaften.
  • a lower limit may be determined by the duration of rotation of a plate serving as the cathode of the X-ray source, which is usually in the range of 5 ms. Thermal changes are usually detectable or effective over an even longer period of time.
  • a development of the invention also relates to the online detection of focus characteristics, in particular during the detection of X-ray projection data, which are used for the reconstruction of image data of an examination subject.
  • the detection of focus ⁇ properties then takes place regularly in the mentioned time interval, preferably synchronized with the acquisition of X-ray projection data.
  • FIG. 1 is a schematic plan view of a combination of FIG. 1
  • Exemplary embodiments A, B, C of a scattered radiation grid with shading devices
  • FIG. 2 shows a schematic sectional view of an X-ray detector system with a scattered radiation grid, which has a shading device in the form of an apertured diaphragm,
  • FIG. 3 shows a schematic sectional view of an X-ray detector system with a scattered radiation grid, which has a shading device in the form of an elongate web,
  • FIG. 4 shows a schematic representation of an exemplary embodiment of a method for determining geometric data
  • FIG. 5 shows a flowchart for a further exemplary embodiment of a method for determining geometry data
  • FIG. 6 shows a computer tomography system with a detector system according to the invention
  • FIG. 7 shows a flow chart for a method for producing a scattered radiation grid with the "selective laser melting" method.
  • the present invention is directed to determine focus ⁇ own properties, which can then be used to improve an image of the inside of an examination subject.
  • the focal properties as mentioned in particular shape, spatial location and extent of a focus ⁇ point of an X-ray source concern, said starting X-ray radiation is emitted gendetektors in the direction of an X-ray from the focal point, preferably in the form of a fan or cone beam.
  • the invention can be used in a computed tomography system, as shown for example in FIG.
  • FIG. 1 shows a scattered radiation grid 200 according to the invention with a plurality of grid cells, which are separated by a first grid
  • a plurality of mutually parallel septa 210 and a further plurality of transversely to the first septa 210 extending further septa 210 are formed.
  • the boundary surfaces 210 formed by the first and second septa 210 form a
  • the passageway 270 includes all illustrated lattice cell at least one passage direction D, so that, in particular parallel with the boundary surfaces 210 turned ⁇ radiated X-rays can pass through the through-channel 270 (See also FIG. 2).
  • Each of the grid cells and in particular each of the passageways 270 has transversely to the
  • Passage direction D has a square cross section and the septa 210 have a height in the direction of passage of about 20 mm.
  • the stray radiation grid 200 shown is arranged or connected to the Detek ⁇ tor for operation in an x-ray imaging system preferably to a (not shown) detection surface of an X-ray detector angenä ⁇ Hert, so that for example the septa 210 in the area of dead zones of the X-ray detector.
  • Such an X-ray detector is usually formed of a plurality of, usually about 50, preferably identical X-ray detector modules that are as a unit Herge ⁇ represents.
  • the septa 210 of the scattered radiation grid 200 are approximately perpendicular to this detection surface.
  • a passage direction D is oriented in this case perpendicular to the detection surface of the detector.
  • a shading device 250 is assigned to some of the grid cells Z, ⁇ , ⁇ ⁇ , ⁇ ⁇ ⁇ .
  • a single grid cell ei ⁇ nes scatter grid 200 which for example is associated with a module of an X-ray detector having such a Abschattungsein- direction 250th
  • Figure 1 shows the Kombina ⁇ tion of several embodiments A, B, C, although as shown may be combined, but preferably a ⁇ individually or in small numbers, for example, up to twenty per stray radiation grid, may be used, preferably one per X-ray detector module.
  • the small number is less than the total number of all grid cells of the scattered radiation grid 200, and the shading devices 250 are arranged in particular regularly, preferably at an equal distance.
  • This offers the advantage that the spatial distance between the grid cells equipped with a shading device 250 is more than a plurality of widths of a grid cell transverse to the direction of passage.
  • the plurality can be more than 15 widths. As will be explained in more detail below, this distance enables a particularly advantageous determination of stereotactic information.
  • the shading device 250 is designed as a pinhole, ie the boundary surfaces 210 of the grid cell Z, which form the passageway 270 are closed in the mounted in the state of the grid of the detector side facing away with a serving as a shading device 250, the centrally Has hole, so that the grid cell Z forms a total of a pinhole camera.
  • the hole has a diameter of about 100 ym and is thus significantly smaller than the mentioned height of the septa of about 20 mm to form the pinhole camera.
  • the flat plate in this case has a thickness in the direction of the passage direction of about 1 mm.
  • the passageway 270 is partially covered by the shading device 250 and thus reduced in relation to passage channels 270 of another "normal" grid cells of the grid. In other words, the passageway 270 is thus additionally shaded from the other, "nor ⁇ paint" grid cells.
  • the shading device 250 is formed by narrow webs which are each arranged between mutually opposite boundary surfaces 210 of the grid cells Z.
  • the exemplary embodiment comprises a plurality of grid lines Z ⁇ ⁇ ⁇ with mutually different shading devices 250 250 ⁇ ⁇ .
  • the longitudinal direction of the narrow ridge extends ⁇ ⁇ in a second direction oriented transversely thereto in a ⁇ ers te direction and in a second grid cell Z.
  • the first and second directions are independent of the orientation of the septa of the ASG, and thus may also be "diagonal", for example, from one corner of a grid cell to an opposite corner, ideally, so that expected changes in focus are as good as possible detek- Tierbar, ie preferably, the longitudinal direction of one of the webs is arranged perpendicular to a main movement direction of the focus.
  • the main movement direction can be determined experimentally, for example in an assigned imaging system or an associated X-ray source, ie before the ASG is constructed.
  • the main direction of motion coincides with the tangent vector of an orbit of the detector in the imaging system into which the detector is to be incorporated.
  • the shading device 250 is formed by the combination of a plurality of narrow webs. These can be, for example, one above the other incorporated into the grid cell Z ⁇ ⁇ ⁇ , or connected, as shown here, such as a cross, which insbeson ⁇ more complete all septa 210 of the grid cell ⁇ connects ⁇ ⁇ ⁇ . This combination of several webs or Operaabschattungsein- directions allow the two-dimensional determination of focus properties.
  • the feature ie the lands or hole in this case, as noted with respect to the pinhole camera, is smaller than the height of the septa 210 and also smaller than the cross section of the passageway across the height of the septa 210 (viewed in the direction of passage D) 270. That is, a relatively small shadow or a relatively small image of the focus can be projected onto a detection surface of the detector so that this shadow or the image moves on the detection surface.
  • the shadow for X-radiation irradiated in the direction of the passage direction of the respective grid cell is none other than the detection area.
  • the shading should preferably not be too large, so that the shaded by means of the shading detection surface can be used simultaneously for the detection of X-ray data, the Reconstruction of an examination object can be used.
  • the size of the shading device in this case is thus a "tradeoff" or compromise between the determination of focus characteristics and the acquisition of information about the object to be examined.
  • the feature i. the shading device, in this case, is integrated in the scattered radiation grid, which is preferably formed with the aid of a so-called "selective laser
  • a metal such as tungsten, tantalum, or copper may be used for the stray radiation grid 200 who ⁇ .
  • MI may be a Pul ⁇ send together of the metal are deposited on a base plate and subsequently melted in a further step M.II the powder layer with a laser in accordance with a desired shape of the Streustrahlungsgit ⁇ ters in the "selective laser melting" process in an initial step be. this should ensure who, ⁇ that results in a coherent structure as possible of the molten areas.
  • the scattered radiation grid 200 together with the shading device 250 can thus be produced in layers as a single coherent, one-piece component D structures can be prepared and so the shading device 250 particularly easy between the boundary surfaces of the scattered radiation grid or partially over the boundary surfaces 210 of the scattered radiation grid 200 can be arranged. Over it from ⁇ can easily a variety of different shading devices 250 into a single stray radiation grid 200 be integrated without, for example, for each under ⁇ different shading 250 a separate punching tool or the like would have to be available.
  • Figure 2 shows the embodiment A of Figure 1 in a sectional view, wherein the scattered radiation grid 200 is connected to an X-ray detector 100, which is installed in an X-ray imaging system. It is so-called egg ⁇ NEN.
  • Subpixel faced detector 100 the units 110 and has a plurality of detection pixel 110.
  • each detection unit 110 is in a plurality of sub-detecting units 120, so-called. Subpixels divided whose sub- Detection signal can be read separately or together. That is, each sub-detection unit 120 generates a sub-detection signal, which is transmitted to an ASIC 140, which can analyze it singly or in combination for all sub-pixels 120 of a pixel 110, and thus as the detection signal of the pixel 110.
  • the detection signal or the sub-detection signal corresponds to the energy and / or to the
  • the X-ray XR is generated by a Röntgenstrahlungsquel ⁇ le 300, which is the detection areas 111 and sub-detection areas arranged 121 opposite each other.
  • a Röntgenstrahlungsquel ⁇ le 300 which is the detection areas 111 and sub-detection areas arranged 121 opposite each other.
  • the x-ray focus 390 is also shown schematically greatly enlarged in relation to the size of a target of the x-ray source 300.
  • the x-ray radiation XR is at the exit of the radiation source 300 by a Blen- end assembly 351 is limited so that the propagating in the direction of X-ray radiation XR gendetektors 100 X ⁇ typically the shape of a fan or cone beam has.
  • the Po ⁇ sition of the focus 390 in the X-ray source 300 may in this case be varied by a plurality of deflection magnet 350 by the electron beam relative to the ring gear 310 is deflected and / or is centered.
  • XR dynamic effects occur as beispielswei ⁇ se heating of the X-ray source 300 and Elect ⁇ Ronen source 320 or the target 310, which affect the shape, extent and location of the focal point 390th This is indicated schematically by the double arrow below the focal point 390 or the X-ray source 300. Ie. the focus 390 or the mentioned focus properties can thus change dynamically during an X-ray exposure.
  • the scattered radiation ⁇ grating 200 in this embodiment a shading means 250, which acts like a pinhole camera in conjunction with the boundary surfaces 210 of the stray radiation grid 200th
  • the origin of the X-ray radiation, ie the focal point 390 is thereby imaged onto a plurality of subpixels 120 of a pixel 110 with the aid of the pinhole camera.
  • the focus point 390 has an elliptical extension deviating from the ideal shape, which can be described by a longitudinal axis and a width axis (long axis of the ellipse and short axis of the ellipse).
  • these properties such as the position of the longitudinal axis, the position of the width axis, as well as their length can be determined exactly by analyzing the sub-detection signals of the illuminated with the help of the pinhole camera subpixel 120.
  • intensity information for incident x-ray radiation XR can to be used.
  • FIG. 1 An alternative to this embodiment, which, as regards. 1, which can also be used in addition, is shown in FIG.
  • the components in construction and arrangement correspond to the components of the detector 100 of FIG. 2.
  • the shading device 250 is an elongate web shown in FIG.
  • the pixels of an image of the focal point 390 on the sub-generated 120, 250 causes the elongate web from the shading ⁇ more subpixel 120.
  • This shadow is shown in Figure 3 in the area of the detection area 111 and the sub-Detek- tion surfaces 121 shown as an ellipse.
  • this can be done with the aid of a detection signal analysis device 150, which may also be present in the embodiment of FIG.
  • the detection signal analyzer 150 generates geometry data necessary for controlling a deflection magnet 350 of FIG X-ray source 300 are used, so that a control loop is formed.
  • the control loop allows a direct feedback of the control effect, ie the control of the deflection magnet 350, by analyzing the geometry data after a successful control or correction of X-ray focus properties.
  • Geometry data can be determined, for example, as shown in FIG.
  • the geometric data can implicitly describe the spatial position of the focal point by determining the spatial center of gravity of an X-ray beam shadow or the spatial center of gravity of the image of the focus.
  • a method is shown for this purpose, as can be used in a so-called "gamma camera.”
  • the subdetection signal of a plurality of subpixels 120a, 120b, 120c, 120d, in particular of a pixel 110 is used in each case 4, a plurality of subpixels 120a, 120b, 120c and 120d are differently exposed to X-rays, and the subdetection signals a, b, c and d are X-ray intensities measured in the subpixels 120a, 120b, 120c and 120d the origin U of a coordinate system at the lower left edge of the pixel 110, the x and y coordinates of absorbed X-ray quanta, which together form the measured X
  • the location of the center of gravity S can in this case be determined with higher Ortsauflö ⁇ solution, than the specified by the Subpixel réelle spatial resolution dictates. Indicates the x-ray detector a plurality of spaced-apart shading devices can easily by determining multiple
  • each of the sub-detection ⁇ signals a, b, c, d of adjacent subpixels 120a, 120b, 120c, 120d are compared with each other, wherein in particular one of a respective sub-pixels 120a, 120b, 120c, 120d ermit- Telte intensity information or an intensity value can be used.
  • Geometry data can be determined or vorlie ⁇ gene in some other way is also provided in another manner. Another method for the determination of geometric data is shown for example in Figure 5.
  • a first step I A the shape, position and extent of the x-ray focus in the form of reference values R are detected or predetermined at a certain point in time.
  • the reference data thus specified in the form of reference values R comprise reference values for detection signals in this exemplary embodiment or sub-detection signals of a pixel at least partially shaded by the shading device.
  • a configuration of detection signals and / or sub-detection signals may already be given which represent a desired position of the position and a desired extension of an x-ray focus.
  • This is done with the aid of the detection signal analysis device 150 in a first step I of the method for the analysis or generation of geometric data.
  • a tolerance range or "tolerance window" for the detection signal and the sub-detection signals is given, in which a modifier ⁇ alteration of focus characteristics is classified as critical.
  • a deviation of the detection signal or the sub-detection signals from the respective reference values R it is checked whether there is a deviation of the detection signal or the sub-detection signals from the respective reference values R.
  • a deviation is fixed, which is outside the respective likewise predetermined by refe rence values ⁇ R tolerance range, the Be ⁇ calculation of a correction signal or a correction data is required for driving the X-ray source.
  • the Kor ⁇ rektursignal is based on the deviation of the measured detection signal and the sub-detection signals with respect to the respective target value.
  • step III correction signals and correction data if requested, in step II, calculates K which drive the X-ray source so that the Detek ⁇ tion signal and / or the sub-detection signals should be within the tolerance range of the desired values. That is, as is indicated by dashed lines, the method can be ⁇ beginning with step I be repeated until the focus again set-off ⁇ corresponding to a target position, target position and expansion, so that the respective focal properties again within their through the reference values R predetermined tolerance range lie.
  • the correction data K can be converted into geometry data GD which correspond to a deviation of the focus from a desired position.
  • the geometry data GD can also directly describe the shape, position and extent of the focus or be formed by the correction data K.
  • the geometry data GD can z. B. together and preferably at the same time to Röntgenproj ekomschal PD are stored in a common record.
  • the geometry data GD in particular in the form of the deviation data from a desired position, can be used in order to carry out a more precise retroactive calculation of the attenuation of the X-radiation by the examination object, so that overall
  • the improved re ⁇ construction or recalculation can for example be such that using the geometry data GD folding or unfolding the Röntgenproj etechnischschal PD is performed with a function that a change in the X-ray proj etechnischschal PD due to the change of focus characteristics (eg Magnification of the focus) in the X-ray projection data PD corrected again.
  • focus characteristics eg Magnification of the focus
  • FIG. 6 schematically shows a computer tomography system 10.
  • the CT system 10 consists essentially of a conventional scanner in which a gantry 130, a detector system with a detector 100 and the detector 100 opposite X-ray source 300th revolves around a measuring space MF.
  • the scanner (not shown) is a patient support device or a patient table whose upper part can be moved with an examination object located thereon relative to the scanner to move the patient relative to the detector 100 through the measuring space MF therethrough.
  • the scanner and the patient table are controlled by a control device 11, from which control data is obtained via an interface 13 in order to control the CT system 10 in accordance with predetermined measurement protocols in the conventional manner (symbolically represented here only by an arrow to the gantry 130).
  • the patient can be moved along the z-direction which ent ⁇ speaks the system axis IZ longitudinally through the measuring space MF.
  • the X-ray source 300 rotates to capture Röntgenproj ekomschal, ie raw data PD to shown the system axis IZ, ie the so-called "isocenter”.
  • the invention can also be used on other CT systems, for example with a detector forming a complete ring
  • the detector system comprises, as has already been described in particular with reference to Figures 1 to 3, a scattered radiation grid according to the invention , and a
  • the raw data PD acquired by the detector 100 and the geometry data GD are transferred as a common data record to a measurement data interface 12 of the control device 11. These raw data PD and geometry data GD are then further processed in an image reconstruction device 15 implemented in the control device 1. In this case, as mentioned with regard to FIG. 5, the geometry data GD is dependent on the image reconstruction. designed to perform an improved reconstruction of the raw data RD.
  • the finished computed tomographic volume image data reconstructed with the aid of the image reconstruction device 15 are then transferred to an image data interface which stores the generated volume image data, for example in a memory of the control device 11 or outputs it in the usual way to the screen of the control device 11 or via an interface (not shown)
  • Image data interface which stores the generated volume image data, for example in a memory of the control device 11 or outputs it in the usual way to the screen of the control device 11 or via an interface (not shown)
  • RIS radiological information system
  • the data can also be processed in any way and then stored or output.
  • the geometry data GD are moreover is Siert ⁇ a correction tur schemes strengthensaku 20, which also reali in the control means 11 in the form of software on a processor, transmitted.
  • the correction data determination unit 20 based on the geometry data, determines correction data K in order to maintain the focus properties in a range specified by reference data, as has also been described with respect to FIG. 5, for example.
  • the correction data determination unit 20 operates in particular in, for example, a measurement protocol, predetermined, preferably periodic intervals so that the correction data K are determined "online", in particular several times during the acquisition of the raw data PD of an examination object, and the correction of focus properties on the basis of the correction data
  • the control results are then fed back by subsequently determined geometry data GD, so that a control loop is formed in which the correction data determination unit 20, the detector 100 and the X-ray source 300 are included via an interface 13 of the scanner, and in particular the X-ray source 300 is driven by the control device 11.

Abstract

L'invention concerne un système de détecteur de rayons X présentant un détecteur de rayons X (100) comportant un certain nombre d'unités de détection (110) générant un signal de détection pour un rayonnement X (XR) incident sur une surface de détection de l'unité de détection (110). L'une des unités de détection (110) présente plusieurs sous-unités de détection (120) générant un sous-signal de détection pour un rayonnement X (XR) incident sur une sous-surface de détection (121) de la sous-unité de détection concernée (120). Le détecteur de rayons X (100) comprend également un dispositif d'écran (250) associé à l'unité de détection (110) et protégeant une ou plusieurs des sous-surfaces de détection (121) du rayonnement X (XR) émis en direction de la sous-surface de détection (121). L'invention concerne par ailleurs une grille antidiffusante munie d'un dispositif d'écran correspondant (250), un système de radiographie muni dudit détecteur de rayons X, un procédé de commande et/ou de régulation des propriétés de focalisation des rayons X au moyen dudit détecteur de rayons X et un procédé de détection de rayonnement X au moyen dudit détecteur. L'invention concerne également un procédé de fusion sélective par laser (selective laser melting) pour la production d'une grille antidiffusante pour ledit détecteur.
PCT/EP2014/064786 2013-07-26 2014-07-10 Détermination de propriétés de focalisation WO2015010913A1 (fr)

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