WO2014192935A1 - Dispositif et procédé de tomographie assistée par ordinateur à rayons x à comptage de photons - Google Patents

Dispositif et procédé de tomographie assistée par ordinateur à rayons x à comptage de photons Download PDF

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WO2014192935A1
WO2014192935A1 PCT/JP2014/064490 JP2014064490W WO2014192935A1 WO 2014192935 A1 WO2014192935 A1 WO 2014192935A1 JP 2014064490 W JP2014064490 W JP 2014064490W WO 2014192935 A1 WO2014192935 A1 WO 2014192935A1
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energy
ray
combined
bins
computed tomography
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PCT/JP2014/064490
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English (en)
Japanese (ja)
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ユー ジョウ，
シャオラン ワン，
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株式会社 東芝
東芝メディカルシステムズ株式会社
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Priority claimed from US13/906,110 external-priority patent/US8965095B2/en
Application filed by 株式会社 東芝, 東芝メディカルシステムズ株式会社 filed Critical 株式会社 東芝
Priority to CN201480026386.1A priority Critical patent/CN105246410B/zh
Publication of WO2014192935A1 publication Critical patent/WO2014192935A1/fr

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    • 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
    • A61B6/48—Diagnostic techniques
    • A61B6/482—Diagnostic techniques involving multiple energy imaging
    • 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
    • A61B6/42—Arrangements for detecting radiation specially adapted for radiation diagnosis
    • A61B6/4208—Arrangements for detecting radiation specially adapted for radiation diagnosis characterised by using a particular type of detector
    • A61B6/4241—Arrangements for detecting radiation specially adapted for radiation diagnosis characterised by using a particular type of detector using energy resolving detectors, e.g. photon counting
    • 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
    • A61B6/52—Devices using data or image processing specially adapted for radiation diagnosis
    • A61B6/5205—Devices using data or image processing specially adapted for radiation diagnosis involving processing of raw data to produce diagnostic data
    • 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
    • A61B6/52—Devices using data or image processing specially adapted for radiation diagnosis
    • A61B6/5258—Devices using data or image processing specially adapted for radiation diagnosis involving detection or reduction of artifacts or noise
    • 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
    • A61B6/4035—Arrangements for generating radiation specially adapted for radiation diagnosis the source being combined with a filter or grating

Definitions

  • Embodiments of the present invention generally relate to spectral computed tomography (CT) and relate to a particular technique of weighting to improve noise in data acquired prior to image reconstruction.
  • CT spectral computed tomography
  • the present embodiment relates to a photon counting X-ray computed tomography apparatus and a photon counting X-ray computed tomography method.
  • Dual energy X-ray CT scan data is obtained at two energy levels.
  • the X-ray tube is set to an energy level of low tube voltage and high tube voltage of 80 kilovolts and 120 kilovolts.
  • a dual X-ray source CT scanner is equipped with two X-ray sources, each operating at a different energy level to generate two data sets.
  • the sandwich detector the upper layer records low energy data while the lower layer records high energy data.
  • the projection data undergoes a preconstruction decomposition.
  • spectral information is acquired at two or more energy levels for a particular X-ray CT scanner.
  • a predetermined number N of energy thresholds is determined according to an average of the thickness of the material, or a scan for air, and the thickness of the base material is directly calculated based on the N sets associated with the measurement data.
  • all detector units and projection views share the same threshold setting. In practice, it is desirable to change the threshold level between certain views as the spectrum changes.
  • the energy band of the energy bin subject to photon counting needs to change according to the situation in order to maintain the low noise level of the obtained data.
  • it is theoretically possible to change the threshold dynamically between multiple views but it is technically challenging because the CT scan is very short. Due to the limitations of current photon counting detector technology, thresholds are not applied correctly in the short time between multiple views as used at one typical rate of 1800 views in 0.5 seconds. It may be. In general, readout electronics, like detectors, have a finite response time and dead time, so considering the currently available technology, the threshold for changing the implementation under the above requirements is limited. .
  • a universally constant threshold value is a threshold value that can result in undesirable noise balance (noise amount balance) in a huge data set. Unbalanced noise in the resulting data set can cause serious artifacts in the spectral image.
  • the number of photons in a low energy bin or a high energy bin is more balanced.
  • the prior art described above remains desirable in that it substantially improves the noise balance in images reconstructed from the obtained data with spectral information.
  • An object of the present invention is to provide a photon counting X-ray computed tomography apparatus and a photon counting X-ray computed tomography method capable of balancing noise in energy bins related to image reconstruction.
  • the photon counting X-ray computed tomography apparatus detects an X-ray tube that generates X-rays and X-ray photons generated from the X-ray tube, and according to the detected number of X-ray photons Based on an X-ray detector that generates an output signal for each of at least three energy bins, a support mechanism that rotatably supports the X-ray tube about a rotation axis, and the number of X-ray photons in each of the energy bins, A synthesis that obtains a synthesized output signal in a synthesized energy bin obtained by synthesizing the selected energy bins by selecting at least two energy bins to be synthesized and synthesizing the number of X-ray photons of the selected energy bins. And a reconstruction unit that reconstructs an image using the combined output signal.
  • FIG. 1 is a diagram showing an embodiment of a multi-slice X-ray CT device or scanner according to this embodiment having a gantry 100 and other devices or units.
  • FIG. 2A is a diagram illustrating an embodiment of a noise balancing device for improving noise balancing according to this embodiment.
  • FIG. 2B is an exemplary set of weight values used in the noise balancing process or device embodiment according to this embodiment.
  • FIG. 3 is a flowchart showing steps or operations having a noise balance improvement process in a computed tomography of a spectrum using a photon counting detector according to the present embodiment.
  • FIG. 4A is a monochrome image reconstructed from noise balance data according to an embodiment of the processing and device according to this embodiment.
  • FIG. 4B is a monochrome image reconstructed from non-noise balanced data according to the present embodiment and processing and device embodiments.
  • FIG. 4C is a diagram showing the image shown in FIG. 4A with lines.
  • FIG. 4D is a diagram showing the image shown in FIG. 4B with lines.
  • FIG. 1 illustrates one embodiment of a multi-slice X-ray CT device, or scanner, according to the current embodiment that includes a gantry 100 and other devices and units.
  • the gantry 100 is illustrated from the front, and includes an X-ray tube 101, an annular frame (support mechanism) 102, and an X-ray detector 103 of a multi-row or two-dimensional array type.
  • the X-ray tube 101 and the X-ray detector 103 are mounted on the annular frame 102 rotating around the axis RA across the subject S in the opposite direction.
  • the rotation unit 107 rotates the annular frame 102 at a high speed, such as 0.4 seconds per rotation, while the subject S moves along the axis RA toward or away from the illustrated page.
  • the support mechanism 102 supports the X-ray tube 101 so as to be rotatable around the rotation axis RA.
  • the multi-slice X-ray CT device further includes a high voltage generator 109 that supplies a tube voltage to the X-ray tube 101 so that the X-ray tube 101 generates X-rays.
  • the high voltage generator 109 is mounted on the annular frame 102.
  • the current regulator 118 adjusts the current supplied to the high voltage generator 109 under the control of the system controller 110.
  • X-rays are emitted toward the subject S, and the cross-sectional area of the subject S is indicated by a circle.
  • the X-ray detector 103 is disposed on the opposite side of the X-ray tube 101 across the subject in order to detect the emitted X-rays transmitted through the subject S.
  • the X-ray CT device or scanner further comprises a data acquisition device 111 that detects the emitted X-rays and processes the detected signals.
  • the X-ray detector 103 is implemented using a plurality of photon counting detectors for counting photons in each of a predetermined number of energy bins.
  • the X-ray detector 103 detects X-ray photons generated from the X-ray tube 101 and generates an output signal corresponding to the detected number of X-ray photons for each of at least three energy bins.
  • Each of the plurality of energy bins defines a predetermined range regarding the energy of transmitted X-rays in the X-ray detector 103.
  • the data acquisition circuit 104 After detecting the emitted X-rays with the X-ray detector 103, the data acquisition circuit 104 converts the signal output from the X-ray detector 103 into a voltage signal for each channel, amplifies it, and further converts it to digital. Convert to signal.
  • the X-ray detector 103 and the data acquisition circuit 104 are configured to process a predetermined total number of projections per rotation (Total number of projections per rotation: TPPR).
  • the data described above is sent to the preprocessing device 106 housed in the console outside the gantry 100 through the non-contact data transmitter 105.
  • the preprocessing device 106 performs specific correction such as sensitivity correction on the raw data.
  • the storage device 112 then stores result data, also called projection data, immediately before the reconstruction process.
  • the storage device 112 is connected to the system controller 110 via the data / control bus together with the reconstruction device (reconstruction unit) 114, the display device 116, the input device 115, and the scan plan support device 200.
  • the scan plan support device 200 has a function of assisting the image technician in order to create a scan plan.
  • One embodiment of the reconstruction device 114 is based on a filtered back projection (FBP) technique using noise weights, and an image from projection data stored in the storage device 112. Reconfigure.
  • the reconstruction device 114 projects based on a filtered backprojection (FBP) technique using features that emulate a specific iteration result at a predetermined number of iterations according to a predetermined sequential reconstruction algorithm. Reconstruct an image from data.
  • the reconstruction device 114 is implemented by a combination of software and hardware, and is not limited to a specific implementation.
  • the term “unit” or “device” includes hardware and / or software.
  • the concept of the reconstruction device 114 can be applied to other modalities including nuclear medicine and magnetic resonance imaging (MRI).
  • the noise balancing device (synthesizer) 117 in one embodiment, balances (balances) noise in the data obtained by making the number of photon counts substantially uniform among a given number of energy bins. Therefore, it is implemented as software, hardware, or a combination of both.
  • the noise balance device 117 assumes a predetermined number M and a predetermined number of base materials N (N is the number of base materials) in a subject to be image-displayed. Is at least 3 (M> 2) energy bins in each of the plurality of photon counting detectors in the X-ray detector 103 in the CT system, and the number M of energy bins is greater than the number N of base materials (M> N). .
  • the base material is, for example, water, bone, contrast medium or the like.
  • a coordinated pursuit also referred to as Basis pursuit
  • the noise balancing device 117 repeats the above calculation for each of the plurality of detection elements and each of the plurality of views. Finally, an image such as a monochrome image is reconstructed by the reconstruction device 114 according to the material thickness L (i) determined by the noise balancing device 117.
  • the noise balancing device 117 selects at least two energy bins to be combined based on the number of X-ray photons in each of the M energy bins.
  • the noise balancing device 117 obtains a composite output signal in N synthetic energy bins obtained by synthesizing the selected energy bins by synthesizing the number of X-ray photons of the selected energy bins.
  • the reconstruction device 114 reconstructs an image using the combined output signal.
  • the noise balancing device 117 has a small number of X-ray photons when selecting one of the two energy bins adjacent to the predetermined energy bin as the energy bin to be combined with the predetermined energy bin. One energy bin may be selected as a synthesis target.
  • the noise balancing device 117 may acquire two combined output signals respectively corresponding to the two combined energy bins by combining the numbers of X-ray photons belonging to different energy bins. At this time, the reconstruction device 114 reconstructs an image using the two combined output signals.
  • the noise balancing device 117 may select the energy bin to be synthesized in order to minimize the difference between the two X-ray photon numbers respectively corresponding to the two synthesized energy bins. Further, the noise balance device 117 synthesizes a plurality of weights corresponding to the M energy bins and the N combined energy bins by multiplying the number of X-ray photons of the selected energy bin, thereby combining the N energy bins. A combined output signal in each of the combined energy bins may be acquired.
  • the noise balancing device 117 may determine the thickness of each of a plurality of base materials equal to the number of composite energy bins (N) using the composite output signal. At this time, the reconstruction device 114 reconstructs an image using the composite output signal corresponding to the determined thickness. Note that the noise balancing device 117 may determine the thickness of each of the plurality of base materials using a predetermined conditional algorithm and the synthesized output signal. In addition, the noise balancing device 117 may determine the thickness of each of the plurality of base materials using a predetermined no-condition algorithm and the synthesized output signal.
  • the energy bin to be synthesized into the synthesized energy bin may be selected depending on the target substance that the operator pays attention to and the desired scanning condition.
  • the scan conditions are, for example, a tube voltage, a thickness of the subject, and the like.
  • the scan condition is input by the operator via the scan plan support device 200, the input device 115, and the like.
  • the scan conditions may be input by a radiology information management system (RIS) or the like via a network (not shown).
  • RIS radiology information management system
  • the input scan condition is stored in the storage device 112.
  • An attention substance is a substance which an operator pays attention among a plurality of base substances.
  • the noise balance device synthesizes the energy bins so that when the noise amounts of the combined energy bins are compared, the noise amounts of the two approach each other (so that both noise amounts approach the noise balance state).
  • the decomposition into the base material is performed based on the Latham pair.
  • the pair is spatially and temporally identical in photon counting.
  • Latham is the sum of attenuation coefficients along a ray defined by the point of the X-ray source and the detector element.
  • a Latham pair is two Lathams obtained with two different spectra (eg, high energy and low energy) along the same Latham.
  • Latham pairs are applicable to dual energy sources in one embodiment.
  • dual energy for example, a dual energy source that generates X-rays having two energies by switching between high and low tube voltages, and two X-ray tubes by applying two different tube voltages to each of the two X-ray tubes.
  • the number M of energy bins coincides with the number of laysums generated with the actual spectrum M along the same ray path.
  • a ray path represents a straight line along the passage of an X-ray beam.
  • the noise is synthesized by combining the M energy bins to N It is balanced by making it an energy bin.
  • the noise balance device 117 is configured so that the number of energy bins M is close to the noise balance state. Requires greater than the number N of base materials (M> N). That is, the processing of the noise balancing method or the embodiment of the noise balancing device 117 does not go into noise balancing in dual energy CT data because at least one extra measurement is required in one ray path.
  • FIG. 2A is a diagram illustrating that one embodiment of the present noise balancing device 117 approaches a noise balancing state.
  • FIG. 2A has a simple overview in which a set of photon counts are collected across four energy bins from 1 to 4. In other words, at least three collected energy bins are defined according to a fixed threshold for collecting photon counts for a predetermined number of views each having a population of Lathams.
  • a group of laysomes corresponds to, for example, a plurality of laysums included in a cone beam. Spectral data including photon counting sets in the four energy collected energy bins is acquired.
  • the photon counts are another predetermined two or more processed composites according to a set of weights associated with the base material and energy bins in the subject. Combined (combined) or redistributed among energy bins.
  • photon counts are combined (synthesized) into collected low energy bins and high energy bins (composite energy bins) from the collected energy bins.
  • FIG. 2B is a diagram illustrating a typical set of a plurality of weight values according to the present embodiment as an embodiment of the noise balancing process.
  • the left side of FIG. 2B lists four typical sets of weight values, each of which is the basis material and energy of the subject. Associated with a specific combination of bins (synthetic energy bins).
  • the superscript L indicates a low energy bin as a processed composite energy bin, and the subscript number indicates one of the collected energy bins.
  • the processed composite energy bin corresponds to a high energy bin.
  • the superscript H indicates a high energy bin as a processed composite energy bin, and the subscript number indicates one of the collected energy bins.
  • the multiple weight values are merely exemplary.
  • a weight value of 1 does not change the normal photon count in a specific energy bin.
  • values less than 1 change the photon count in the associated energy bin.
  • FIG. 3 is a flowchart showing an operation or stage having a process for approaching a noise equilibrium state in a computed tomography of a spectrum using the photon counting detector according to the present embodiment.
  • the process to approximate the noise balance is performed by various methods including software, hardware, and a combination of both.
  • the following steps or actions are optionally performed by the units and devices of the present embodiment, as described above with reference to FIG. 1, but for approaching noise balance in spectral computed tomography using a photon counting detector. Processing is not limited to the performance of this particular embodiment.
  • photons are detected or counted for each of a plurality of energy bins at a predetermined photon counting detector or X-ray detector 103 in step S100.
  • the photon counting detector has a predetermined number of detector elements, each detector element having a predetermined number of energy bins (M energy bins) separated by a corresponding number with respect to a fixed threshold at the energy level. .
  • the energy threshold level is predetermined and stored in the readout electronic device.
  • a first set of photon counts is obtained with at least three energy bins for each of a predetermined number of views having a collection of lathams.
  • the photon count is the photons contained in the processed composite energy bin in step S110 according to this embodiment.
  • the number N of synthetic energy bins is two or more and is equal to the number of base substances in the subject.
  • the number N of composite energy bins is smaller than a predetermined number M of energy bins (N ⁇ M) in order to bring the noise in the spectral data closer to equilibrium between the composite energy bins.
  • a predetermined set of weights is used, each of the predetermined weights uniquely being one of the corresponding principal components (or composite energy bins) and corresponding Is associated with one of the energy bins.
  • the photon count in the composite energy bin is related to the material thickness for each of the base materials in step S120.
  • the photon counts in each of the combined energy bins are now more balanced in noise than before step S110.
  • the more noise balanced photon count in each of the combined energy bins is now associated with the material thickness L (i) where i is 1 to M.
  • Non-zero L (i) is determined using a predetermined coordinated perchue technique.
  • the predetermined coordinate pursuit technique is, for example, basis pursuit, and in the case of this embodiment, the following conditional expression:
  • step S130 it is determined whether steps S100, S110, and S120 are further performed for any remaining elements relating to detector elements or photon counting detectors for every view. If, in step S130, it is determined that steps S100, S110, and S120 have not been completed for each detection element or photon counting detector for every view, the process proceeds with the plurality of steps being either detection elements or photons. Return to step S100 to be performed on the counting detector or the rest in the view. On the other hand, if it is determined in step S130 that steps S100, S110, and S120 are complete for each detector or photon counting detector for every view, the process proceeds with the material thickness of each base material. Proceed to step S140 to reconstruct the image from the noise-balanced photon count in the processed composite energy bin.
  • the number M of energy bins is greater than the number N of synthetic energy bins processed (M> N).
  • the photon counts in the collected energy bins are combined into processed composite energy bins to approximate the noise balance in the energy bins. If the collected energy bin M is equal in number to the processed composite energy bin N, the same number of energy bins will fail to approach the noise equilibrium.
  • the projection data g m measured in the energy bin m is expressed by g m (BH) as a radiation effect term, an average attenuation coefficient with respect to the base material n and the energy spectrum m.
  • the base material is indexed by n to indicate a specific base material between 1 and N.
  • energy bins are indexed by specifying specific energy bins between 1 and M energy bins.
  • the thickness L n of the base material is determined by optimizing or minimizing the following evaluation function (L).
  • ⁇ m represents the noise of the measured projection g m .
  • the noise balancing step is arbitrarily skipped and L n is determined directly by minimizing the evaluation function with additional constraints.
  • the thickness L of the base material is expressed by Equation (1) as follows:
  • the noise balance device 117 calculates the basis material from the sum of the projection data g m measured in the energy bin and the radiation hardening projection data g m (BH) (L) depending on the thickness (L) of the basis material in the energy bin.
  • the weight is determined on condition that the absolute value of the difference obtained by subtracting the sum over the product type n is smaller than the noise ⁇ m related to the projection data (formula (3)).
  • Projection data g m as represented by the formula (4), by using a radiation quality curing section depends on the thickness of the base material g (BH) (L) are updated.
  • Equation (5) the evaluation function ⁇ (L) is expressed by Equation (5) using ⁇ , which is a positive constant that determines the weight of the loss term.
  • the thickness L of the base material is
  • Equation (6) is approximated by Equation (7) as follows.
  • Equation (7) the partial differentiation of g m (BH) (L) by L n is relatively small compared to the other terms in Equation (6) and can be ignored.
  • the thickness of the base material is updated by equation (8).
  • L n in the above formula (8) (0) shows the current value in the repetition.
  • L n in the above formula (8) indicates a value updated in repetition.
  • L (0) is a vector having L n (0) as an element.
  • the second evaluation function ⁇ is defined by Equation (10), with the noise for the energy bin m as ⁇ m 2 for a given measurement projection g m . That is, the noise balancing device 117 uses the evaluation function ⁇ as the projection data g m measured in the energy bin and the line hardening hardening projection data g m (BH) (L) depending on the thickness (L) of the base material in the energy bin.
  • Mean attenuation coefficient defined by the base material thickness L, the base material type n, and the energy bin m
  • the square of the difference obtained by subtracting the sum over the product type n is defined as the sum over the energy bin m of the quotient obtained by dividing the square of the noise ⁇ m 2 for the projection data.
  • the weight value w is defined to perform noise reduction and is determined for each corresponding basis material n and energy bin m and is now normalized to a particular basis material as in equation (12) below. is defined by using the k n is a factor.
  • Normalization factor k n are defined as the following equation (13).
  • the third evaluation function is defined to be used together with the process for approaching the noise balance state in the energy bin according to the present embodiment.
  • equation (18) is assumed:
  • the measured projection data g m is measured by the energy bins m, associated with the estimation of the thickness L n.
  • the base material g m (BH) is a linear hardening term
  • the basis material is indexed by n to define a particular basis material between 1 and N basis materials.
  • energy bins are indexed to define a particular energy bin between 1 and M energy spectra.
  • Equation (14) the weighted version of the measured projection and the base material thickness as represented by equation (14) is the weight as represented by equations (15), (16) and (17). Is applicable to the relationship represented by the equation (18).
  • a variable ⁇ that is the reciprocal of is defined.
  • Expression (19) becomes Expression (21) indicating the thickness of the base material n based on Equations (20) and (15).
  • the evaluation function ⁇ as the weighted noise of the thickness of the base material is expressed by Expression (24). That is, the noise balancing device 117 calculates the evaluation function ⁇ by the inverse of the weighted average attenuation coefficient for the base material.
  • FIGS. 4A and 4B a pair of images shows some effects of noise balance according to embodiments of the present apparatus and processing.
  • FIG. 4A is a monochrome image reconstructed from noise balanced data according to an embodiment of the present apparatus and processing.
  • FIG. 4B is a monochrome image reconstructed from data that has not been brought close to the noise balance according to the apparatus and processing embodiment of the present invention.
  • Unbalanced noise can cause severe artifacts in monochrome images, as shown in FIG. 4B, and that noise will likely reduce diagnostic capabilities. For this reason, the improved noise nature probably increases the diagnostic ability based on the final image quality.
  • FIG. 4C is a diagram showing FIG. 4A as a diagram.
  • FIG. 4D is a diagram showing FIG. 4B as a diagram.
  • an energy bin to be synthesized is selected based on the photon count collected by each of a plurality of energy bins, and the X-rays of the selected energy bins are selected.
  • the number of photons can be synthesized.
  • This energy bin selection can be performed to balance the photon counts belonging to the composite energy bin.
  • the energy bins may be selected such that the dispersion of the base material thickness is small.
  • the present embodiment it is also possible to select the energy bin to be synthesized according to the scanning condition or the target substance that the operator pays attention to. Thereby, according to this embodiment, noise is balanced and the image corresponding to the scanning condition or the target substance can be reconstructed.
  • the noise in the plurality of synthetic energy bins can be balanced by making the photon counts in the plurality of synthetic energy bins substantially uniform.
  • the reconstructed image quality is improved due to noise balance.
  • the functions according to the embodiment can also be realized by installing a program (medical image reconstruction program) for executing the processing in a computer such as a workstation and developing the program on a memory.
  • a program capable of causing the computer to execute the technique is stored in a storage medium such as a magnetic disk (floppy (registered trademark) disk, hard disk, etc.), an optical disk (CD-ROM, DVD, etc.), or a semiconductor memory. It can also be distributed.
  • DESCRIPTION OF SYMBOLS 100 ... Gantry, 101 ... X-ray tube, 102 ... Annular frame (support mechanism), 103 ... X-ray detector, 104 ... Data acquisition circuit, 105 ... Non-contact data transmitter, 106 ... Pre-processing device, 107 ... Rotation unit , 108 ... slip ring, 109 ... high voltage generator, 110 ... system controller, 111 ... data collection device, 112 ... storage device, 114 ... reconstruction device, 115 ... input device, 116 ... display device, 117 ... noise balance device (Combining unit), 118 ... current regulator, 200 ... scan plan support device.
  • Combining unit Combining unit
  • Current regulator 200 ... scan plan support device.

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Abstract

Selon le mode de réalisation de la présente invention, un dispositif de tomographie assistée par ordinateur à rayons X à comptage de photons est pourvu : d'un tube à rayons X (101) qui génère des rayons X ; d'un détecteur de rayons X (103) qui détecte des photons de rayons X générés par le tube à rayons X (101) et qui génère des signaux de sortie correspondant au nombre de photons de rayons X détectés par rapport à chacun d'au moins trois compartiments d'énergie ; d'un mécanisme de support (102) qui soutient le tube à rayons X (101) de façon rotative autour d'un axe de rotation ; d'une unité de combinaison (117) qui sélectionne au moins deux compartiments d'énergie à combiner sur la base des nombres de photons de rayons X dans les compartiments d'énergie respectifs et qui combine les nombres de photons de rayons X dans les compartiments d'énergie sélectionnés pour ainsi acquérir un signal de sortie combiné dans un compartiment d'énergie combiné, obtenu par combinaison des compartiments d'énergie sélectionnés ; d'une unité de reconstruction (114) qui reconstruit une image à l'aide du signal de sortie combiné.
PCT/JP2014/064490 2013-05-30 2014-05-30 Dispositif et procédé de tomographie assistée par ordinateur à rayons x à comptage de photons WO2014192935A1 (fr)

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US13/906,110 US8965095B2 (en) 2013-05-30 2013-05-30 Noise balance pre-reconstruction data decomposition in spectral CT
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