WO2009050626A1 - Système d'imagerie à sources et détecteurs répartis - Google Patents

Système d'imagerie à sources et détecteurs répartis Download PDF

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Publication number
WO2009050626A1
WO2009050626A1 PCT/IB2008/054187 IB2008054187W WO2009050626A1 WO 2009050626 A1 WO2009050626 A1 WO 2009050626A1 IB 2008054187 W IB2008054187 W IB 2008054187W WO 2009050626 A1 WO2009050626 A1 WO 2009050626A1
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Prior art keywords
radiation
detector
source
sources
trajectory
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PCT/IB2008/054187
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English (en)
Inventor
Hermann Schomberg
Randall Peter Luhta
Rainer Pietig
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Koninklijke Philips Electronics N.V.
Philips Intellectual Property & Standards Gmbh
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Publication of WO2009050626A1 publication Critical patent/WO2009050626A1/fr

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
    • G01N23/02—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material
    • G01N23/04—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and forming images of the material
    • G01N23/046—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by transmitting the radiation through the material and forming images of the material using tomography, e.g. computed tomography [CT]
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/02—Arrangements for diagnosis sequentially in different planes; Stereoscopic radiation diagnosis
    • A61B6/03—Computed tomography [CT]
    • A61B6/032—Transmission computed tomography [CT]
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/40—Arrangements for generating radiation specially adapted for radiation diagnosis
    • A61B6/4007—Arrangements for generating radiation specially adapted for radiation diagnosis characterised by using a plurality of source units
    • A61B6/4014—Arrangements for generating radiation specially adapted for radiation diagnosis characterised by using a plurality of source units arranged in multiple source-detector units
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/40—Arrangements for generating radiation specially adapted for radiation diagnosis
    • A61B6/4021—Arrangements for generating radiation specially adapted for radiation diagnosis involving movement of the focal spot
    • A61B6/4028—Arrangements for generating radiation specially adapted for radiation diagnosis involving movement of the focal spot resulting in acquisition of views from substantially different positions, e.g. EBCT
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/02—Arrangements for diagnosis sequentially in different planes; Stereoscopic radiation diagnosis
    • A61B6/027—Arrangements for diagnosis sequentially in different planes; Stereoscopic radiation diagnosis characterised by the use of a particular data acquisition trajectory, e.g. helical or spiral
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus or devices for radiation diagnosis; Apparatus or devices for radiation diagnosis combined with radiation therapy equipment
    • A61B6/44—Constructional features of apparatus for radiation diagnosis
    • A61B6/4488—Means for cooling
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2223/00—Investigating materials by wave or particle radiation
    • G01N2223/40—Imaging
    • G01N2223/419—Imaging computed tomograph
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2223/00—Investigating materials by wave or particle radiation
    • G01N2223/60—Specific applications or type of materials
    • G01N2223/612—Specific applications or type of materials biological material

Definitions

  • the invention relates to an x-ray computed tomography (CT) system. Moreover, the invention relates to a method of operating a CT system and to a computer program product.
  • CT computed tomography
  • Imaging systems and in particular x-ray imaging systems, are utilized for various applications in both medical and non-medical fields.
  • Medical x-ray imaging systems such as computed tomography (CT) systems are capable of producing exact cross- sectional or volumetric image data that express certain physical properties related to the human or animal body. Reconstruction of three-dimensional (3D) images representing a volume of interest has been applied in the medical field for some time.
  • CT computed tomography
  • Cardiac volume imaging is an important application of CT. Cardiac volume imaging is typically done with helical CT and retrospective gating. Even though this approach works reasonably well, it is hampered by limited temporal resolution and high radiation dose.
  • the patient table is translated during the scan while the gantry of the CT scanner rotates.
  • multi-row detectors become available that are, for instance, 15 cm "high”
  • the need for translating the patient table disappears.
  • the rotation speed of the gantry becomes a limiting factor.
  • the time window for collecting the data for a 3D snapshot image of the beating heart during diastole is only approximately 100 ms long, which means that the gantry has to complete one rotation in about 180 ms. Such a gantry would be very costly.
  • Electron Beam CT Electron Beam CT
  • An EBCT scanner has a stationary detector and a stationary, huge, scanning electron beam x-ray tube.
  • the scanning electron beam x-ray tube remains a drawback of EBCT; it is bulky and costly, and its x-ray power is limited.
  • a system is disclosed which seeks to reduce challenges associated with movement of a source and/or a detector.
  • an x-ray imaging system which includes a distributed x-ray source configured to emit x-rays from a plurality of emission points and a detector.
  • Embodiments of the geometric arrangements of the emission points and the detector are provided. However, with the disclosed geometric arrangements, when they are used without mechanical movement, it is not possible to collect a set of cone beam projections from which one can reconstruct a high-quality CT image.
  • the invention preferably seeks to mitigate, alleviate or eliminate one or more of the above mentioned disadvantages singly or in any combination.
  • a plurality of distributed radiation sources arranged to emit radiation beams from a plurality of emission locations, the plurality of emission locations being arranged substantially along a source trajectory, the radiation penetrating a volume of interest around an isocenter;
  • the isocenter is a distinguished spatial point conceptually attached to the system.
  • the invention has the insight that in order to provide a system that is not hampered from self- blocking, a special arrangement of both the distributed radiation sources and of the distributed detector modules is needed.
  • a self-blocking system suffers from a blocking of the emitted radiation by intervening portions of the detector. It is an advantage of the present invention that an imaging system may be provided which is not self-blocking, where the plurality of distributed radiation sources may be configured to remain stationary with respect to the volume of interest, and where the plurality of distributed radiation detector modules may be configured to remain stationary with respect to the volume of interest.
  • a CT scanner without moving parts may thereby be provided.
  • the source trajectory is complete with respect to a sizeable volume of interest around the isocenter.
  • a source trajectory is said to be complete with respect to a volume V, if every plane that intersects V also intersects the source trajectory. This condition is also known as Tuy's completeness condition.
  • a planar source trajectory cannot be complete with respect to a true volume. If a source trajectory is complete with respect to V, then an accurate, three-dimensional image of the content of V may be reconstructed from the cone beam projections of V taken along the source trajectory, provided these cone beam projections are not truncated.
  • the plurality of distributed radiation sources ranges from 500 to 1000 radiation sources. It may be advantageous to use a number of sources in this range in order to achieve a sufficient resolution of the reconstructed image.
  • the radiation sources are carbon-nanotube-based x-ray sources. It is an advantage to use such a source type, since such sources may be fabricated suitably small so that a large number of sources may be placed along the source trajectory.
  • the total detector area resembles a non-planar, specially curved strip, or sheet.
  • the detector is built from identical detector modules, the odd and even numbered detector modules may be arranged alternately with a first and second distance from the isocenter of the volume of interest. A closer packing of the detector modules is thereby achieved.
  • the plurality of distributed radiation sources and the plurality of distributed detector modules are individually addressable. Advantageous scan protocols which avoid overheating of the sources are thereby rendered possible.
  • a method of operating a cone beam CT imaging system is provided.
  • the method of operation may operate a imaging system in accordance with the first aspect of the invention, where the at least first radiation source and the at least first radiation detector module are operated such that radiation emitted from an at least first radiation source passes through the volume of interest and is detected by an at least first radiation detector module.
  • groups of radiation detector modules are associated with the radiation sources so that for a first radiation source in the plurality of the radiation sources, and for at least a second radiation source in the plurality of radiation sources, the associated first and the at least second group of radiation detectors do not overlap. This is advantageous, since radiation source activation sequences and detector readout sequences may be provided, which provide fast scanning without suffering form overheating of the source.
  • the sequence in which the radiation sources are turned on is correlated to an input signal.
  • a scan protocol which allows for long scan sequences of dynamic organs, such as the heart, may thereby be provided.
  • a computer program product having a set of instructions, when in use on a computer, to cause the computer to perform the method of the second aspect.
  • Such computer program product may be implemented in accordance with a system of the first aspect of the invention.
  • FIG 1 shows a cross- sectional view of a schematic exemplary embodiment of a cone beam computed tomography apparatus
  • FIG. 2 shows a simplified perspective view of a schematic exemplary embodiment of the radiation source arrangement and detector arrangement
  • FIG. 3 illustrates graphs of the functions a( ⁇ ), ⁇ ( ⁇ );
  • FIG. 4 illustrates an exemplary embodiment of a source module
  • FIG. 5 illustrates exemplary embodiments of detector modules and the arrangement of a source
  • FIG. 6 schematically illustrates a front view of the source/detector arrangement of an example scanner
  • FIG. 7 illustrates a flow diagram of operating an imaging system in accordance with embodiments of the present invention.
  • Embodiments of the present invention are disclosed in connection with an x-ray cone beam computed tomography (CT) scanner or imaging system. Specific numerical values are provided below in connection with example embodiments, these numerical values are provided in connection with an example scanner. It is however clear to the skilled person that numerical values provided in connection with the example scanner, are only provided as example values, and do not limit the scope of the invention.
  • CT computed tomography
  • FIG 1 shows a cross- sectional view of a schematic exemplary embodiment of a cone beam computed tomography apparatus.
  • the apparatus comprises a radiation source 1 capable of emitting x-ray radiation in the form a cone beam 2.
  • the apparatus is associated with a center point called the isocenter 3.
  • the apparatus comprises a radiation detector arrangement 4 which is opposite to the radiation source.
  • the apparatus is intended to acquire transversely non-truncated cone beam projections of a certain volume of interest 5 around the isocenter 3.
  • the volume of interest is large enough to contain a human heart, for example.
  • the sensitive area 6 of the detector faces the radiation source.
  • a straight line 8 starting at the center point of the sensitive area and passing through the isocenter meets the center of the emission location 7 of the radiation source.
  • FIG. 2 shows a simplified perspective view of a schematic exemplary embodiment of the radiation source arrangement and detector arrangement, as well as the arrangement of a collimator slit.
  • the detector modules are indicated by brick-shaped cuboids arranged along a detector trajectory 21, whereas locations of the radiation sources are arranged along a source trajectory 20, depicted by a dotted line, and the center line of the collimator slit 22 is depicted by straight lines.
  • the trajectories defined by the source arrangement, the detector arrangement and the collimator arrangement each extend on the surfaces of isocentric spheres with different radii and each resembles a portion of the boundary curve of a saddle.
  • a plurality of distributed radiation sources are arranged to emit radiation beams from a plurality of emission locations being arranged substantially along the source trajectory 20, and a plurality of distributed radiation detector modules are arranged substantially along a detector trajectory 21.
  • the plurality of distributed radiation sources and the plurality of distributed radiation detector modules are configured to remain stationary with respect to the volume of interest.
  • the source and detector trajectories are such that a straight line that starts at a point on the source trajectory and passes through the isocenter intersects the detector trajectory.
  • An important aspect of this geometry is that the radiation beam that is emitted from an emission location on the source trajectory is not significantly blocked by a portion of a radiation detector between the emission location and the volume of interest.
  • the collimator 22 represents a slit whose center line extends essentially parallel to the source trajectory.
  • the center line of the collimator slit is essentially a scaled image of the source trajectory.
  • the plurality of radiation sources may be in the form of small x-ray sources that are aligned along the source trajectory.
  • the number of sources will lie in the range of 500 and 1000, such as in the range of 600 to 800.
  • the sources may be grouped into identically built modules, e.g. with 9 orlO adjacent sources per module, an example embodiment of source modules is disclosed below in connection with FIG. 4.
  • the plurality of detector modules may be arranged in a detector strip, which is assembled from identically built detector modules, where the sensitive area of each module is a rectangular, possibly tiled, array of small detector elements. Embodiments of the detector modules are disclosed below in connection with FIG. 5.
  • the collimator slit confines the raw cone beams of x-rays that emanate from the sources such that the surviving x-rays hit the desired opposite portion of the detector strip.
  • the source trajectory, the detector trajectory and the center line of the collimator slit are specified formally in terms of parametric representations.
  • Cartesian x-y-z coordinate system 23 is attached to the isocenter of the scanner such that the y- axis points horizontally towards the foot end of the patient table, the z-axis points vertically upwards, and the x-axis points horizontally to the right.
  • the origin of the coordinate system 23 has been displaced from the isocenter for clarity reasons.
  • the coordinate system 23 thus merely indicates the x-y-z directions.
  • the source trajectory is given by
  • r s 900 mm.
  • the sensitive area of the odd and even numbered detector modules are arranged alternately with a first and second distance from the isocenter, where the center points of the sensitive areas of the odd-numbered modules lie on a first detector trajectory, and the center points of the sensitive areas of the even-numbered modules lie on a second detector trajectory that is similar to the first curve, but has a slightly larger radius.
  • the two detector curves lie on isocentric spheres, too.
  • the long axis of each detector module is perpendicular to the module's detector trajectory and tangential to its detector sphere. Adjacent detector modules are tightly packed side by side. As a result of this arrangement, an observer looking from anywhere on the source curve towards the opposite portion of the detector strip would see virtually no gap between the sensitive areas of adjacent detector modules.
  • the detector trajectory for the odd and even numbered detector modules are given by
  • E 1 ( ⁇ ) r dl (cos a( ⁇ ) cos ⁇ ( ⁇ ), sin ⁇ ( ⁇ ) - sin a( ⁇ ) cos ⁇ ( ⁇ )) (2)
  • b 2 ( ⁇ ) r d2 (cos a( ⁇ ) cos ⁇ ( ⁇ ), sin ⁇ ( ⁇ ) - sin a( ⁇ ) cos ⁇ ( ⁇ )) (3)
  • the collimator trajectory is given by
  • the radius r s of the source sphere is greater than the radii ra ⁇ and rai of the detector spheres. It is also possible to make the radius r s smaller than the radii ra ⁇ and rai.
  • FIG. 3 illustrates a( ⁇ ), ⁇ ( ⁇ ), in the form of (180/ ⁇ ) ⁇ (/l) and (180/ ⁇ )y?(/t) in order to convert radians to degrees.
  • FIG. 3A shows a( ⁇ ) (denoted with reference numeral 30), whereas FIG.
  • 3B shows ⁇ ( ⁇ ) (denoted with reference numeral 31).
  • the function a( ⁇ ) is in the form of a straight line, whereas the function ⁇ ( ⁇ ) can not be expressed by a simple closed formula.
  • the geometry of the source trajectory, the detector trajectory, and the collimator trajectory, and more specifically, the functions a( ⁇ ) and ⁇ ( ⁇ ) are further disclosed in the published international patent application WO 2005/104952, especially in connection with FIGS. 3-6 and 8-13. This disclosure is hereby incorporated by reference.
  • FIG. 4 illustrates an exemplary embodiment of a source module, wherein the radiation sources are carbon-nanotube-based x-ray sources, e.g. by using carbon nanotubes as cold electron emitters
  • the long and curvilinear arrangement of sources may be assembled from short, identically built modules 49 with a rectilinear arrangement of sources.
  • Each module may contain a small number of sources, for example 9 or 10.
  • Suitable modules can be built, for example, by modifying the source modules as described in by J. Zhang et al., in the article: "Stationary scanning x-ray source based on carbon nanotube field emitters," Applied Physics Letters 86, 184104, 2005. This article is hereby incorporated by reference.
  • FIG. 4A illustrates a schematically view of a source module in a cross- sectional front-view.
  • FIG. 4B illustrates the source module in cross- sectional side-view.
  • a number (here 9) of cold electron emitters 40 based on carbon nanotubes are placed on the cathode 41.
  • the electron beams 48 are emitted towards the anode 42.
  • the beam is shaped and focused by electrode gates 43.
  • the electron beam is focused on the tilted anode surface 44, resulting in the emission of x-rays 45.
  • the x-rays leave the source module through an x-ray window 46 which limits the transversal cone angle of the raw cone beam.
  • the axial shaping of the cone beams is done by the collimator slit 22 shown in FIG. 2.
  • the anodes of the x-ray sources may actively be cooled by using water or alternative cooling means 47.
  • the cooling agent may, e.g. pass through a hollow anode 400.
  • the source modules may be mounted onto a properly curved rail, such that their focal spots are aligned essentially along the desired source trajectory.
  • the precise locations of the focal spots can be measured and is favorably used for the reconstruction.
  • the modules may be tightly packed side by side. Since the source curve is bent, there will be small wedge-shaped gaps between adjacent source modules. These gaps cause no harm.
  • FIG. 5 illustrates exemplary embodiments of detector modules and the arrangement of the source 50, the isocenter 51 and the detector 54, 55.
  • the detector strip is assembled from smaller, flat, identically built detector modules 56, 57.
  • Each detector module may in an exemplary embodiment in itself be a rectangular, planar detector that is organized as a 2D array of small detector elements or tiles.
  • the example modules 54, 56 as shown FIG. 5A are brick-shaped and have a sensitive area of 40 mm by 280 mm.
  • the detector modules may be mounted onto a properly curved rail. The precise locations of the active detector areas can be measured and is favorably used during the reconstruction.
  • the desired detector strip is not cylindrical, there would remain small wedge-shaped gaps between adjacent detector modules, when the modules would be tightly packed side by side along one of the detector curves.
  • tight packing is combined with alternating radial distances, as indicated by the radii 52 and 53, as shown in FIG. 5A it can be arranged that an observer positioned on a source location and looking towards the opposite portion of the detector strip sees virtually no gaps between the sensitive areas of adjacent modules.
  • the modules can be packed even tighter when they are given a T-shaped cross-section 55, 57, as illustrated in FIG. 5B.
  • a T-shaped cross-section may therefore in embodiments be preferred over a rectangular cross-section.
  • a source-focused anti-scatter grid cannot be used, as with all CT scanners that vary the source position relative to the detector during a scan.
  • FIG. 6 schematically illustrates a front view of the source/detector arrangement of the example scanner. Again for clarity reasons, only the detector modules 60 are shown as cuboids, whereas the sources modules 61 are shown as dots. The collimator slit is shown as a solid line. Scan protocols are disclosed in connection with FIG. 6.
  • the sources 61 are numbered consecutively from 1 (marked by reference numeral 62) through N s (marked by reference numeral 63).
  • the detector modules 60 are numbered consecutively from 1 (marked by reference numeral 64) through N d (marked by reference numeral 65).
  • the plurality of distributed radiation sources and the plurality of distributed detector modules are individually addressable and may be individually operated in the sense that they may be turned on, turned off, read out, have specific operation parameters set, etc.
  • the detector modules are build from detector elements. In such embodiments, the elements may be individually addressable, however at least for some applications, all elements of a module may be individually addressable as a group.
  • a group of radiation detectors may be associated to the radiation source so as to detect at least a part of the emitted radiation beam.
  • the zth source fires, i.e. is turned on (as an example, the zth source may be taken as the source marked by reference numeral 66), it emits a "raw" cone beam 66' of x-rays towards the opposite portion of the detector strip.
  • a group of detector modules 67 opposite to the source is activated and read out. For brevity, this group of detector modules will be called the zth detector group 67.
  • the x-rays that start at the zth source and hit the zth detector group define the zth cone beam proper (as opposed to the raw cone beam that leaves the zth source), or simply the zth cone beam.
  • Ji 0 (Z) and Jh 1 (Z) such that the detector modules of the zth detector group are numbered, Ji 0 (O, JIo(O + I, •••, Jn(O- As i increases, the numbers J 0 (O and Jh 1 (O remain constant for a small range of z's, and then increase by one, etc.
  • the number of detector modules of each detector group is chosen sufficiently large so that the transversal cone angle of the associated cone beam is about 50°; as a result, the cone beam projections of a non-obese patient will normally not be transversely truncated.
  • FIG. 6 illustrates the cone beams proper of the sources 1 (marked by reference numeral 68), i (marked by reference numeral 67), and i + NJ2 n, for i close to NJA (marked by reference numeral 69).
  • Cone beams that start near one end of the source curve are a little asymmetric and have a slightly narrower transverse cone angle.
  • the intersection of the proper cone beams of all x-ray sources of the scanner forms the "volume of full projection;" which is the volume that is “seen” by all proper cone beams.
  • the fully projected volume is large enough to contain a human heart and a good deal of its surroundings.
  • a sphere with a diameter of 20 cm is contained in the volume of full projection.
  • the fully projected volume is a subvolume of the convex hull of the source trajectory. This means that Tuy's completeness condition is satisfied in the volume of full projection. It is a clear advantage that Tuy's completeness condition is satisfied, since then this volume can be reconstructed without the "cone beam” artifacts that are typical of, and unavoidable with, circular and other planar source trajectories.
  • a number of scan parameters need to be properly chosen. Such parameters include the tube voltage E and the tube current /. Also important is the sequence in which the sources are fired, the number N 0n of how often a source is switched on during a scan, and the duration T 0n of each on-time of each source. (The on- time of a source, as this term is used here, is not related with the pulsed working mode of carbon-nanotube-based x-ray sources).
  • the parameters E, I, N 0n , and T 0n may all be set independently of the source number i. From the mentioned and other "primary" scan parameters, a number of "secondary" scan parameters can be derived.
  • the total scan time r scan which is another secondary parameter, is related to the total radiation time, but may differ from the latter when there are idle times during the scan with no sources on, or when several sources are on simultaneously.
  • a typical tube voltage is 120 kV
  • a typical tube current is 300 rriA
  • a typical total radiation time is 500 ms, which is also the rotation time of the gantry.
  • the applied power becomes 36 kW and the time-current product becomes 150 mAs.
  • These parameters are also appropriate for the related "circular" version of cone beam CT which results from the above fan beam version when the single detector row is replaced by a multi-row detector with a large number of rows.
  • the anode of the x-ray tube would quickly melt if it were static, the anode is made to rotate in order to dissipate the heat. It is a drawback of conventional CT gantries that they do not rotate quickly enough for a heart scan to be completed within 100 ms, and making them that fast would be very costly, if possible at all. With the cone beam CT scanner in accordance with embodiments of the present invention, it is desirable to achieve a similar time-current product, using a similar tube voltage. Again, the anodes of the x-ray sources would heat up very quickly, but now it is not possible to rotate the anodes to dissipate the heat. On the other hand, since the sources are individually addressable they may be switched on and off very rapidly, and in any order.
  • FIG. 7 illustrates a flow diagram of operating an imaging system in accordance with embodiments of the present invention.
  • Radiation is provided 70 from at least a first radiation source from the plurality of distributed radiation sources.
  • the radiation is detected 71 with at least a first radiation detector from the plurality of distributed radiation detectors, i.e. the associated detector group.
  • the at least first radiation source and the at least first radiation detector are operated 72 such that at least part of the radiation emitted from the at least first radiation source is detected by the at least first radiation detector.
  • the sources and detectors may be operated so that the radiation sources are turned on sequentially, and the group of radiation detectors associated with the radiation sources are read out sequentially.
  • example embodiments of sequences or scan protocols are provided.
  • a read sequence is set such that the detector is readout and reset during the delays.
  • source and detector sequence may be set so that the reading of detector group i and the firing of source i+ NJ2 may overlap in time with the firing of source i and the reading of detector group i+ NJ2.
  • the idle time Jl d i e is thereby reduced.
  • some idle time Ji d i e should be introduced for reading the detector. Nevertheless, the total scan time of such a
  • T- SCan ⁇ 0n /2+ 0v s /2-i)r ldle _
  • a relatively long on-time JO n may be chosen.
  • the originally planned single (sequential, interleaved, sequential double, or still other) scan sequence may be replaced by a faster scan sequence with a reduced on-time.
  • a waiting time may be added between these faster scans.
  • the measured results of the faster scans would be averaged to obtain the effect of the originally planned single scan.
  • Splitting up a single "slow" scan into multiple faster scans in this way may reduce the temperature rise of the anodes by introducing an extra cool-down time for the anodes.
  • the original time current product remains unchanged.
  • the scanned part of the body must remain essentially static during the whole scan.
  • the allowed maximum scan time is an ample plenty of seconds.
  • the heart rests only about 100 ms during a single heart beat.
  • the sequence of the radiation sources being turned on may be correlated to an input signal, so that the sequence may be stopped upon receipt of a stop signal, and resumed upon a resume signal.
  • Such an input signal may e.g. be provided by the patient's ECG signal, which may be used to start the scan precisely at the beginning of the resting period.
  • the time-current product that can be obtained within the available 100 ms even with the best possible scan sequence is deemed to be too small, one may repeat this scan sequence during the resting periods of several subsequent heart beats and average the measured results.
  • the patient's ECG signal may be used to re- start the scan sequence during each heart beat. This scan mode requires the patient not only to lie still, but also to hold his or her breath for the required number of heart beats.
  • retrospective gating is not required, and the applied radiation dose is not increased compared to the dose that is required for the desired signal-to-noise ratio.
  • the acquired raw data may be pre-processed as usual in CT, e.g. by turning them into line integrals of the linear x-ray attenuation coefficient. Adverse effects of scattered x-rays may also be corrected or reduced using a suitable correction method.
  • the reconstruction itself may be achieved using available reconstruction algorithms. If the reconstruction algorithm assumes a flat detector that is subdivided into rectangular array of detector elements, the measured cone beam projections may be re-sampled onto a virtual detector of the required type.
  • Various pre-processing techniques and reconstruction algorithms are available to the skilled person.
  • the invention can be implemented in any suitable form including hardware, software, firmware or any combination of these.
  • the invention or some features of the invention can be implemented as computer software running on one or more data processors and/or digital signal processors.
  • the elements and components of an embodiment of the invention may be physically, functionally and logically implemented in any suitable way. Indeed, the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units. As such, the invention may be implemented in a single unit, or may be physically and functionally distributed between different units and processors.

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Abstract

L'invention concerne un système d'imagerie tomographique informatisé à faisceau conique comprenant une pluralité de sources de rayonnement (20) réparties disposées de façon à émettre des faisceaux de rayonnement depuis une pluralité de sites d'émission et une pluralité de modules détecteurs de rayonnement (21) répartis. Les pluralités de sources et de modules détecteurs sont disposées sur des trajectoires de sources et des trajectoires de détecteurs, respectivement, de sorte qu'une ligne droite qui commence en un point sur la trajectoire d'une source et passe par l'isocentre du système coupe la trajectoire d'un détecteur. Un faisceau de rayonnement n'est pas significativement bloqué par une partie d'un module détecteur de rayonnement entre le site d'émission et le volume d'intérêt. Le système n'est pas entravé par une auto-obstruction.
PCT/IB2008/054187 2007-10-19 2008-10-13 Système d'imagerie à sources et détecteurs répartis WO2009050626A1 (fr)

Applications Claiming Priority (2)

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US98111907P 2007-10-19 2007-10-19
US60/981,119 2007-10-19

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WO2009050626A1 true WO2009050626A1 (fr) 2009-04-23

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Cited By (4)

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WO2012177867A3 (fr) * 2011-06-22 2013-05-02 Medtronic Navigation, Inc. Imagerie interventionnelle
GB2509399A (en) * 2012-12-27 2014-07-02 Nuctech Co Ltd CT apparatus comprising a scanning passage, a stationary x-ray source with a plurality of focal spots, and a plurality of detector modules.
GB2510973A (en) * 2012-12-27 2014-08-20 Nuctech Co Ltd CT apparatus without gantry
EP3066983A4 (fr) * 2013-11-06 2017-08-30 Rayence Co., Ltd. Dispositif d'imagerie à rayons x comprenant une pluralité de sources de rayons x

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WO2005104952A1 (fr) * 2004-04-28 2005-11-10 Philips Intellectual Property & Standards Gmbh Tomographie par ordinateur tridimensionnelle par faisceau d'electrons
US20070009081A1 (en) * 2000-10-06 2007-01-11 The University Of North Carolina At Chapel Hill Computed tomography system for imaging of human and small animal
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US20070009081A1 (en) * 2000-10-06 2007-01-11 The University Of North Carolina At Chapel Hill Computed tomography system for imaging of human and small animal
WO2005104952A1 (fr) * 2004-04-28 2005-11-10 Philips Intellectual Property & Standards Gmbh Tomographie par ordinateur tridimensionnelle par faisceau d'electrons
US20070009088A1 (en) * 2005-07-06 2007-01-11 Edic Peter M System and method for imaging using distributed X-ray sources

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2012177867A3 (fr) * 2011-06-22 2013-05-02 Medtronic Navigation, Inc. Imagerie interventionnelle
CN103781423A (zh) * 2011-06-22 2014-05-07 美敦力导航股份有限公司 介入性成像
US10849574B2 (en) 2011-06-22 2020-12-01 Medtronic Navigation, Inc. Interventional imaging
GB2509399A (en) * 2012-12-27 2014-07-02 Nuctech Co Ltd CT apparatus comprising a scanning passage, a stationary x-ray source with a plurality of focal spots, and a plurality of detector modules.
GB2510973A (en) * 2012-12-27 2014-08-20 Nuctech Co Ltd CT apparatus without gantry
GB2510973B (en) * 2012-12-27 2015-10-07 Nuctech Co Ltd CT apparatus without gantry
GB2509399B (en) * 2012-12-27 2016-01-06 Nuctech Co Ltd Stationary CT apparatus
US9551808B2 (en) 2012-12-27 2017-01-24 Nutech Company Limited CT apparatus without gantry
EP3066983A4 (fr) * 2013-11-06 2017-08-30 Rayence Co., Ltd. Dispositif d'imagerie à rayons x comprenant une pluralité de sources de rayons x

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