DE19933537B4 - X-ray computed tomography apparatus with means for modulating the x-ray power of an x-ray source - Google Patents

X-ray computed tomography apparatus with means for modulating the x-ray power of an x-ray source

Info

Publication number
DE19933537B4
DE19933537B4 DE19933537A DE19933537A DE19933537B4 DE 19933537 B4 DE19933537 B4 DE 19933537B4 DE 19933537 A DE19933537 A DE 19933537A DE 19933537 A DE19933537 A DE 19933537A DE 19933537 B4 DE19933537 B4 DE 19933537B4
Authority
DE
Germany
Prior art keywords
ray
ray source
radiation
ct apparatus
apparatus according
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
Application number
DE19933537A
Other languages
German (de)
Other versions
DE19933537A1 (en
Inventor
Matthias Dipl.-Ing. Berger (FH)
Herbert Dipl.-Ing. Bittl (Fh)
Ernst Dipl.-Ing. Neumeier (Fh)
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Siemens AG
Original Assignee
Siemens AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to DE19837443 priority Critical
Priority to DE19837443.7 priority
Priority to DE19850493 priority
Priority to DE19850493.4 priority
Application filed by Siemens AG filed Critical Siemens AG
Priority to DE19933537A priority patent/DE19933537B4/en
Publication of DE19933537A1 publication Critical patent/DE19933537A1/en
Application granted granted Critical
Publication of DE19933537B4 publication Critical patent/DE19933537B4/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

Links

Classifications

    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
    • A61B6/54Control of devices for radiation diagnosis
    • A61B6/542Control of devices for radiation diagnosis involving control of exposure
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
    • A61B6/02Devices for diagnosis sequentially in different planes; Stereoscopic radiation diagnosis
    • A61B6/03Computerised tomographs
    • A61B6/032Transmission computed tomography [CT]
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N23/00Investigating 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
    • G01N23/02Investigating 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
    • G01N23/04Investigating 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
    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05GX-RAY TECHNIQUE
    • H05G1/00X-ray apparatus involving X-ray tubes; Circuits therefor
    • H05G1/08Electrical details
    • H05G1/26Measuring, controlling, protecting
    • H05G1/30Controlling
    • H05G1/34Anode current, heater current, heater voltage of X-ray tube
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61BDIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
    • A61B6/40Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment with arrangements for generating radiation specially adapted for radiation diagnosis
    • A61B6/4021Apparatus 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

Abstract

X-ray CT device with means (11 to 16, 21, 29) for modulating the x-ray power of a relative to an X-ray source (1, 22, 32) and with a detector system for the X-ray source (1, 22, 32) outgoing X-radiation, the X-ray CT device in different Positions of the X-ray source (1, 22, 32) receives projections, wherein the x-ray source (1, 22, 32) the X-radiation while recording a projection in one or more pulses, and wherein by means (11 to 16, 21, 29) for modulation the x-ray power the duration of the pulses in dependence from a weakening profile of the examination object (5) for the individual projections is adjustable so that the im Funds for the respective projection applied mAs product the course of At least weakening profiles corresponds qualitatively, wherein the radiation intensity of the the X-ray source (1, 22, 32) outgoing X-ray radiation unchanged remains.

Description

  • The The invention relates to an X-ray computed tomography (CT) device with means for the modulation of the x-ray power an X-ray source displaceable relative to an examination object and with a detector system for that from the X-ray source outgoing X-radiation.
  • Such an X-ray CT apparatus is for example in the US 5,379,333 , of the DE 195 27 518 A1 , of the DE 195 32 535 A1 and the DE 28 15 347 A1 described.
  • In the earlier, but not pre-published priority DE 198 07 639 An x-ray CT apparatus is described with means for modulating the x-ray power of an x-ray source displaceable relative to an examination subject and a detector system for x-ray radiation emanating from the x-ray source, the x-ray CT apparatus recording projections in different positions of the x-ray source, and wherein the means for modulating the x-ray power adjust the x-ray power as a function of a weakening profile of the examination object for the individual projections such that the mAs product applied on average for the respective projection corresponds at least qualitatively to the profile of the attenuation profile.
  • in the In general, an X-ray CT apparatus has an X-ray source on which a collimated, fan-shaped x-ray beam through the examination object, e.g. a patient, on a row-shaped bench directed by detectors of the detector system. The source, and depending on Type of X-ray CT device also the Detector system are mounted on a gantry, which surround the object under investigation rotates. A storage table for the examination object can be moved within the gantry or to be moved. The position from which the X-ray beam the object under examination penetrates, and the angle under which the x-ray the subject of the examination penetrates as a result of the rotation the gantry constantly changed. Each detector of the detector system produces a signal that a Measure of Total transparency of the body of the examination object for that from the X-ray source outgoing X-rays on its way to the detector. The set of output signals the detectors of the detector system, for a particular position of the X-ray source is won, is called projection. A so-called scan comprises a set of projections in different positions of the Gantry and / or different positions of the storage table won were. The X-ray CT device is taking while one full revolution of the gantry 360 ° around the examination subject extensive scans a variety of projections on to a two-dimensional Sectional view of a layer of the body of the examination object. Take newer CT devices many layers at the same time by using detector systems use multiple rows of detectors. For each projection measures one as Monitor or reference detector, the unattenuated intensity of the X-radiation.
  • It There are two systematically different ways of generating that required by CT images of three-dimensional areas of an examination subject To record data.
  • at the conventional one Sampling will be the data during a complete one Taken up rotation of the gantry and thus scanned a layer, while the object to be examined is in a fixed position. Between the scanning of successive layers becomes the object under investigation each moved to a new position in which the next shift can be sampled. This process continues until all scanned before the examination.
  • at The spiral scan rotates the gantry with the x-ray source around it Object of investigation while the storage table and the gantry are continuously in the direction of longitudinal axis the storage table are moved relative to each other. The x-ray tube describes so based on the object under investigation a spiral path, until the was scanned volume before the examination. From the Spiral data obtained in this way are then used to calculate images of individual layers.
  • at Each of the two types of scanning will improve the picture quality by the quantum noise impaired. Therefore, the radiation intensity that from the X-ray source emitted X-rays for every Projection high enough to ensure that the minimum radiation intensity the one out of the body emerging from an object under investigation and reaching a detector X-rays even higher than the noise level is.
  • In the known x-ray CT X-ray modulating apparatus, the radiation intensity, ie, the photon flux, is appropriately changed as a function of angular position of the gantry during scanning of the examination subject to contain the areas of the examination object of high radiation attenuation when taking projections to work with the required high radiation intensity and on the other hand, in the recording of projections, the areas of Un low radiation attenuation object to work with correspondingly lower radiation intensity and thus lower radiation exposure of the examination subject to work.
  • Such X-ray CT devices, for example, require two orthogonal tomograms ( US 4,174,481 ) or "Scout Views" ( US 5,379,333 ) in order to be able to obtain the information necessary for the modulation of the x-ray power with respect to the profile of the maximum beam attenuation value of the individual projections as a function of the angular position of the gantry, ie with respect to the so-called angle attenuation profile of the examination subject.
  • To can for example from the attenuation information every line of the topograms or from the "Scout Views" to the actual circumstances approximated Angle attenuation profile be determined.
  • The appropriate modulation of the x-ray power is done by one of the respective desired x-ray power Adjustment of the radiation intensity of the X-ray radiation via the change of the tube current the X-ray source, by influencing the heating current of the hot cathode. Since then, however, such a setting of the tube current because of the limited Heating and cooling speed the hot cathode relatively sluggish is capable of modulating X-ray power Angle attenuation profiles with quick changes the radiation attenuation only insufficient to follow. It therefore occurs due to an insufficient adaptation of the modulation the x-ray power to the angle weakening profile additional, also inhomogeneous image noise.
  • Of the Invention is based on the object, an X-ray CT apparatus of the beginning so-called type in such a way that the modulation of the X-ray power also strong changes the attenuation profile to follow.
  • To According to the invention, this object is achieved by means of an X-ray CT apparatus with means for the modulation of the x-ray power an X-ray source displaceable relative to an examination subject and with a detector system for that from the X-ray source outgoing X-radiation, the X-ray CT device in different Positions of X-ray source projections receives, with the X-ray source the x-ray radiation while recording a projection in one or more pulses, and wherein the means for modulating the X-ray power is the duration of the Pulse depending from a weakening profile of the examination object for adjust the individual projections in such a way that on average for each Projection applied mAs product the course of the attenuation profile at least qualitatively.
  • Becomes a conventional one Sampling at which the X-ray source rotated around the subject, or a spiral scan, at at the same time a displacement of the X-ray source and the Detector system on the one hand and the object under investigation on the other made in the direction of the axis of rotation, made the attenuation profile in the form of an angle weakening profile in front. If, however, a scan is made, in which the rotation the X-ray source is blocked and only a shift of the X-ray source and the detector system on the one hand and the examination object on the other hand, in the direction of the axis of rotation relative to each other takes place, is the attenuation profile in the form of an axial weakening profile before, i.e., there is the course of the radiation attenuation of the examination subject in the direction of the axis of rotation again.
  • It So it becomes clear that the invention for conventional Sampling, sprial sampling and the determination of so-called topograms suitable.
  • in the In the case of the invention, therefore, the modulation of the x-ray power takes place not in the way that over the Heating current of the hot cathode the radiation intensity the X-ray radiation changed but by the fact that the X-ray source the x-ray radiation while the recording of a projection in several pulses, their duration for influencing the applied for receiving the respective projection average x-ray power changed becomes. In contrast to the influence of the x-ray power over the Heating current of the hot cathode is a change the average x-ray power by pulsing the X-radiation virtually inertia-free possible, So that the Modulation of X-ray power also strong changes the attenuation profile to follow.
  • It is advantageous that the radiation intensity during a scan does not have to be changed, but the same radiation intensity can be present for all pulses of a scan, which is preferably the case, since not the currently present X-ray power has to be changed, but only during the scan Recording a projection of effective mean X-ray power is changed by appropriately adjusting the duration of the pulses. This also offers the advantage that it is always possible to work with a radiation intensity which is sufficiently high for a good signal-to-noise ratio, possibly even the maximum radiation intensity of the X-ray source, this being the case due to the attenuation profile correspondingly selected duration of the pulses, which is relevant for a given number of pulses and given tube current for mAs product, yet can not lead to the subject under investigation experiences an unnecessarily high radiation exposure.
  • There the X-ray source due to the pulsation of the X-radiation not while of the total required to capture a projection Time is in operation, an improved image resolution is also achieved, because of the reduced total time during which the X-ray source to take a projection is generally active, a reduction the azimuthal slurring of the measured values in conventional Scans as well as spiral scans is achieved, which in particular for greater distances from the axis of rotation applies.
  • Regarding the weakening profile can be provided that this in a known manner based on topograms or scout Views is determined before the actual examination; but it can also be provided that the attenuation profile while the investigation on the basis of suitable algorithms from the past projections are calculated in advance.
  • According to one particularly preferred embodiment According to the invention, the X-ray CT apparatus according to the invention has an X-ray source with a vacuum housing in which an anode and an electron emitter for generating a Electron beam are recorded, wherein the electron beam to Generation of X-rays meets the anode, and with an associated with the electron emitter Control electrode, e.g. a Wehnelt cylinder or a grid, which by the means for modulating the x-ray power to a blocking potential can be connected to interrupt the electron beam. The X-ray source is thus constructed analogously to a triode and allows a non-inertial Pulsation of X-rays.
  • A Variant of the invention provides that the means for modulation the x-ray power Have switching means for applying the blocking potential, with the X-ray source combined into one unit are. In this way, the connection between the switching means and the control electrode short, so that adverse influences the blocking behavior and thus the pulsation of the X-radiation due to high capacity and inductance values located between the switching means and the control electrode Lines are excluded. Preferably, the unit is the Switching means and the X-ray source made by either the switching means at the X-ray source attached or housed inside the vacuum housing of the X-ray source.
  • A another embodiment the invention provides that the Means for modulating the x-ray power the duration of the pulses for adjust each projection so that for each projection that to comply with a desired Signal / noise ratio required mAs product is achieved. This ensures that the existence certain signal / noise ratio is achieved without the object to be examined unnecessary X-ray dose is administered.
  • A other embodiment the invention provides that the Inventive X-ray CT apparatus a Monitor detector, on which the outgoing from the X-ray source X-ray unimpaired impinges, wherein the weakening profile using the output signals of the detector system and the Monitor detector is detected.
  • A particularly preferred embodiment the invention provides that the to determine the attenuation profile provided with the X-ray source and the detector system be displaced relative to the object to be examined. In this case it is not required to determine the attenuation profile, data supplied by the detector system between a moving and to transfer a fixed part back and forth. Besides, we one Relief of the image computer, which in principle also the determination of the attenuation profile could be achieved.
  • embodiments The invention are in the attached schematic drawings shown. Show it:
  • 1 an x-ray CT device, as used to generate cross-sectional images of an examination subject,
  • 2 the typical angle attenuation profile for a complete rotation of the X-ray source of an X-ray CT apparatus according to 1 around a human patient in the area of his shoulder,
  • 3 and 4 for two projections with different maximum beam attenuation, the pulsed X-radiation emitted to record the respective projection,
  • 5 and 6 in to the 3 and 4 analogous representation of the conditions for a Betriebszu stood in which only a single pulse of X-radiation is emitted per projection,
  • 7 the CT device according to 1 in partially block diagram representation,
  • 8th and 9 a variant of the X-ray source of the X-ray CT apparatus according to the 1 and 5 , and
  • 10 in to the 7 analogous representation of another inventive CT device.
  • This in 1 The third generation X-ray CT apparatus shown has an X-ray source 1 which is a collimated, fan-shaped x-ray beam 2 towards a detector bank 3 radiating detector system radiates. The X-ray source 1 and the detector bank 3 are on a partially shown rotatable gantry 4 arranged continuously in the φ-direction about a rotation axis Z around a patient 5 can rotate as examination object. A monitor detector 6 (please refer 7 ) serves to from the X-ray source 1 to receive incoming X-rays unattenuated.
  • To record a projection penetrates the X-ray beam 2 a layer of the patient 5 and the resulting output signals of the individual detectors of the detector bank 3 be from the channels of an in 1 not shown data acquisition and measurement system detected. For example, at angular intervals of 1 ° each projection, during one complete revolution, the gantry 4 taken and instructs the detector bank 3 For example, 512 detectors are turned on during one complete revolution of the gantry 4 360 projections were recorded, each projection comprising 512 data, which are the output signals of the detectors occurring in the respective projection.
  • If you take the gantry in one full turn 4 the shoulder area of the patient 5 For each of the projections, the output signal of the detector having the smallest output signal can be determined from the output signal of the monitor detector associated with the respective projection 6 determine the maximum beam attenuation values A proj_max of the individual projections.
  • The 2 shows for the shoulder region of a patient the maximum radiation attenuation values A proj_max of the individual projections of a complete rotation of the gantry 4 as a function of the angular position π of the gantry 4 , the so-called angle weakening profile. Accordingly, it becomes clear that the maximum beam attenuation value A proj_max as a function of the angular position π of the gantry 4 varies greatly.
  • If a constant intensity of the X-ray radiation is used, which ensures a good image quality even for the projection with the greatest maximum radiation attenuation value A proj_max , then the patient will have a lower radiation attenuation value A proj_max when taking the remaining radiation Projections a radiation dose supplied, which is much higher than is the case in X-ray CT equipment in which a dose modulation is provided according to the angle attenuation profile of the area to be examined of each patient. In the case of the X-ray CT apparatus according to the invention, the dose modulation now takes place in such a way that, on the one hand, the X-ray radiation is emitted in such a pulsed manner that one pulse or several pulses occur during the recording of a projection and, on the other hand, the duration of the pulses for the individual projections corresponds to the angle attenuation profile is set differently, in such a way that in the case of projections with high radiation attenuation value A proj_max the duration of the pulses is longer than in the case of projections with low beam attenuation value A proj_max .
  • This is in the 3 and 4 illustrates for the case that are used to receive two different projections each several, for example five, pulses, wherein in the case of 3 , which illustrates the ratios for a larger beam attenuation value, the duration of the pulses about twice as long as in the case of 4 which shows the ratios for a lower radiation attenuation value. In the 3 and 4 the intensity of the X-radiation I R is plotted against the time t. The total area of the pulses therefore corresponds to the mAs product applied in each case for receiving the respective projection, which thus in the case of the 3 about twice as high as in the case of 4 is.
  • The 5 and 6 illustrate the inclusion of the same projections as in the case of 3 and 4 in the event that only one pulse is used to record each of the two projections, in the case of 5 the ratios are illustrated for a greater beam attenuation value and the duration of the pulse is about twice as long as in the case of 6 where the ratios are shown for a lower radiation attenuation value.
  • Due to the pulsation of the X-ray radiation, the radiation intensity does not have to be changed in order to modulate the X-ray power. Rather, all pulses in the recording of a projection the same, a the respective sub search case of adequate image quality ensuring radiation intensity. In addition, it is preferable to work with the same radiation intensity during the recording of all the projections of a scan. As the 3 to 6 By way of example, all the projections can be taken with the maximum intensity of the X-radiation, which offers the advantage that the maximum possible signal-to-noise ratio is always achieved without the patient 5 is loaded with an unnecessarily high radiation dose.
  • The X-ray CT device according to 1 is in 7 illustrated in more detail. Accordingly, the X-ray source 1 a vacuum housing 7 in which an anode 8th and a cathode 9 , which is a hot cathode, are included. The X-ray source 1 is with an electric generator circuit 10 connected, which provides the required for the operation of the X-ray source voltages, namely on the one between the anode 8th and cathode applied tube voltage U R = U + + U- and the other at the cathode 9 applied heating voltage U H. From the cathode 9 goes in the operation of the X-ray source 1 a in 7 dotted lines indicated electron beam, which on the anode 8th from the then in turn the X-ray beam 2 emanates. Between the cathode 9 and the anode 8th a control electrode is arranged, which in the case of the embodiment according to the 1 and 7 as a grid 11 is trained.
  • To the grid 11 can by means of a switching stage 12 one of blocking potential can be applied. Depending on the at a control input of the switching stage 12 applied signal is the grid 11 separated from the blocking potential, with the result that the electron beam to the anode 8th can reach, or connected to the blocking potential, which is so dimensioned that at the grid 11 adjacent blocking potential prevents electrons from the cathode 9 to the anode 8th can reach. So it's possible, by means of the grid 11 and the switching stage 12 to pulse the X-radiation.
  • The switching stage 12 and the pulse width modulator 15 are to form a unit with the X-ray source 1 as well as these directly on the gantry 4 attached so that the connection of the switching stage 12 with the grid 11 short and thus low in capacitance and inductance.
  • The switching stage 12 has a control input connected to the output of a pulse width modulator 15 connected is. The pulse width modulator 15 is of a stationary in the case of the described embodiment, not on the gantry 4 attached, electronic computing device 16 , which serves both as a control unit of the X-ray CT apparatus and as an image computer, on the one hand a clock signal and on the other hand supplied a signal which serves the pulse duration of synchronous to the clock signal at the output of the pulse width modulator 15 occurring and thus the control input of the switching stage 12 supplied pulses and thus to adjust the duration of the pulses of the X-radiation.
  • To the electronic computing device 16 are a keyboard 17 and a display unit 18 , eg a monitor, connected. The keyboard 17 allows an operator to operate the X-ray CT device. The display unit 18 is used to display images created by the X-ray CT device.
  • To the electronic computing device 16 is also a data acquisition and measurement system 19 connected, with its input channels, the detectors of the detector bank 3 connected to the gantry 4 the X-ray source 1 opposite is attached. The already mentioned monitor detector 6 is connected to a special monitor channel of the data acquisition and measurement systems 19 Connected to the gantry 4 is attached and thus together with the detector bank 3 rotates.
  • In the case of the embodiment described, this is the pulse width modulator 15 supplied clock signal with the power stroke of the data acquisition and measurement system 19 synchronized, so that even if only one pulse of X-radiation per projection is used, a proper function is ensured. If several pulses of X-ray radiation per projection are used, said synchronization is not absolutely necessary, but is advantageous for image reconstruction.
  • The electronic computing device 16 contains a memory 21 in which one or more angle attenuation profiles of each patient to be examined 5 stored, which were determined prior to the actual investigation on the basis of topograms or "scout views" in a conventional manner. Based on the scanned area of the patient 5 significant angle attenuation profile changes the electronic computing device 16 that the pulse width modulator 15 supplied control signal such that the mAs product that the patient 5 is applied to receive the respective projection, ensures that the image noise a specific on the keyboard 17 does not exceed the preselectable value.
  • The angle attenuation profile does not necessarily have to be taken from topographies taken before the actual examination or "Scout Views "won and in the store 21 but can also be obtained "on line" during the actual examination in an alternative mode of operation, by the radiation attenuation value of the angle attenuation profile belonging to the next projection to be recorded being taken from the data of a number of immediately recorded projections and the associated data of the monitor detector 6 and another in the field of Rönt genstrahlenquelle mounted monitor detector 20 , this is to the electronic computing device 16 connected by the electronic computing device 16 is extrapolated. This extrapolation can begin as soon as a certain number of projections, eg half a revolution of the gantry 4 corresponding number, of projections with a fixed duration of the pulses, eg the maximum duration of the pulses was recorded
  • In the case of the embodiment according to the 1 and 7 are like the X-ray source 1 , the switching stage 12 and the pulse width modulator 15 together on the gantry 4 attached, so that these components are combined into one unit and thus the connection of the switching stage 12 with the grid 11 short and thus low in capacitance and inductance. In the interest of a more inductively and less capacious structure, however, according to 8th Also be provided that the X-ray source, the switching stage and the pulse width modulator are combined directly into a structural unit.
  • Like from the 8th can be seen has the X-ray source 22 a total with 23 designated vacuum housing, in which a rotary anode 24 by means of two rolling bearings 25 and 26 is rotatably mounted. The vacuum housing 22 has an approach 27 in which a cathode designed as a hot cathode 28 is included.
  • The cathode 28 is different as a control electrode in the case of the X-ray source according to 7 no grid, but a Wehnelt electrode 29 assigned, so that in the operation of the X-ray source 22 from the cathode 28 outgoing electron beam 30 If necessary, can be interrupted by the Wehnelt electrode 29 via the switching stage 12 with the pulse width modulator 15 is connected. Both the switching stage 12 as well as the pulse width modulator 15 are to form a unit in the approach 27 of the vacuum housing 23 taken on, outside the vacuum space, in the case of the embodiment according to 8th through a the cathode 28 and the Wehnelt electrode 29 carrying insulator 31 is limited.
  • In the interest of a further induction and capacity poorer structure, it is also possible to produce the assembly of X-ray source, switching stage and pulse width modulator in that - as in 9 is indicated schematically - the switching stage 12 and the pulse width modulator 15 inside the vacuum housing 23 otherwise with the 8th consistent X-ray source 32 are included. This procedure assumes that the switching stage 12 and the pulse width modulator 15 constructed of vacuum-compatible components or otherwise hermetically sealed.
  • The above describes a mode in which a single layer of the patient 5 is scanned. In another mode, the gantry 4 and the patient 5 shifted relative to each other in the direction of the axis of rotation Z, so that three-dimensional areas of the patient 5 be scanned, whether by successive scanning of planar layers, be it by spiral scanning.
  • In another mode, the rotation of the gantry 4 blocked and the gantry 4 and the patient 5 are moved relative to each other in the direction of the axis of rotation Z in order to record so-called topograms can. Also in this case, a pulsation of the X-rays takes place while adjusting the duration of the pulses to a in this case Axial-attenuation profile, preferably from the electronic computing device 16 is determined by extrapolation, analogous to that previously for the rotating gantry 4 described extrapolation is proceeded.
  • Incidentally, it can also be provided that the storage of the attenuation profiles in the pulse width modulator 15 takes place or the pulse width modulator 15 extrapolation of the attenuation profile. The pulse width modulator 15 is then from the electronic computing device 16 supplied with the necessary data.
  • The embodiment according to 10 differs from the prescribed in that the pulse width modulator 15 is formed such that it also completely determines the attenuation profile to be considered in each case, wherein he does not require the data required for this purpose from the electronic computing device 16 but directly from the data acquisition and measurement system 19 gets what's in 10 is illustrated by a corresponding line. As a result, on the one hand, the transmission of data from the stationary electronic computing device required in the case of the embodiment described above becomes possible 16 to the one on the gantry 4 located pulse width modulator 15 avoided; the other is the electronic computing device 16 relieved, so that they can fulfill their other tasks, such as image reconstruction, accordingly faster.
  • in the Case of the described embodiments the detector has a single row of detector elements. However, the invention can also be used in connection with such X-ray CT devices find that have a detector, the multiple rows of detector elements and thus allows multiple projections simultaneously take.
  • The X-ray source of the X-ray CT apparatus according to the invention can X-ray tubes of various types, such as fixed-anode tubes as in the case of the embodiment according to the 1 and 7 Rotary anode tubes as in the case of the embodiments according to the 8th and 9 or rotary lobe radiators known per se. It is only important that they have means for pulsing the X-radiation. In this case, the pulsation of the X-ray radiation does not have to take place as in the case of the exemplary embodiments described above by means of a control electrode which inhibits the flow of electrons, but can also be carried out differently, for example by pulsing the tube voltage.
  • The The invention is above the example of X-ray CT equipment of third generation described. But it can also be used in X-ray CT devices fourth generation use where instead of using the X-ray source around the object under investigation revolving detector bank an annular stationary detector bank is provided.
  • Even though the invention described using the example of a medical application is, it can also be applied in the non-medical field.

Claims (15)

  1. X-ray CT device with means ( 11 to 16 . 21 . 29 ) for modulating the x-ray power of a relative to an examination subject ( 5 ) displaceable X-ray source ( 1 . 22 . 32 ) and a detector system for the X-ray source ( 1 . 22 . 32 ) X-ray radiation, wherein the X-ray CT apparatus in different positions of the X-ray source ( 1 . 22 . 32 ) Recording projections, wherein the X-ray source ( 1 . 22 . 32 ) emit X-ray radiation during the recording of a projection in one or more pulses, and wherein by means of ( 11 to 16 . 21 . 29 ) for the modulation of the X-ray power, the duration of the pulses as a function of a weakening profile of the examination object ( 5 ) is adjustable for the individual projections in such a way that the mAs product applied on average for the respective projection corresponds at least qualitatively to the profile of the attenuation profile, the radiation intensity of the radiation emitted by the X-ray source ( 1 . 22 . 32 ) outgoing X-radiation remains unchanged.
  2. X-ray CT apparatus according to claim 1, wherein the X-ray source ( 1 . 22 . 32 ) around the examination object ( 5 ) is displaceable and the weakening profile is in the form of an angle weakening profile.
  3. X-ray CT apparatus according to claim 2, wherein the displacement of the X-ray source ( 1 . 22 . 32 ) takes place in the form of a rotation and during the rotation a displacement of the X-ray source ( 1 . 22 . 32 ) and the detector system, on the one hand, and the object to be examined, on the other hand, in the direction of the axis of rotation.
  4. X-ray CT apparatus according to claim 1, wherein the X-ray source is rotatable about an axis about the examination subject and the X-ray source ( 1 . 22 . 32 ) and the detector system on the one hand and the examination subject ( 5 ) on the other hand without rotation of the X-ray source ( 1 . 22 . 32 ) are displaceable relative to each other in the direction of the axis and the weakening profile is in the form of an axial weakening profile.
  5. X-ray CT apparatus according to one of claims 1 to 4, which is an X-ray source ( 1 . 22 . 32 ) with a vacuum housing ( 7 ), in which an anode ( 8th ) and an electron emitter are received for generating an electron beam, wherein the electron beam for generating X-ray radiation to the anode ( 8th ), and with a control electrode associated with the electron emitter, which is controlled by the means ( 11 to 16 . 21 . 29 ) can be connected to the modulation of the x-ray power to a blocking potential for interrupting the electron beam.
  6. X-ray CT apparatus according to claim 5, whose X-ray source ( 22 . 32 ) as a Wehnelt electrode ( 29 ) has executed control electrode.
  7. X-ray CT apparatus according to claim 5, whose X-ray source ( 1 ) one as grid ( 11 ) has executed control electrode.
  8. X-ray CT apparatus according to one of Claims 1 to 7, the means for modulating the X-radiation comprising switching means for applying the blocking potential associated with the X-ray source ( 1 . 22 . 32 ) are combined into one unit.
  9. X-ray CT apparatus according to claim 8, wherein the unit of the switching means and the X-ray source ( 1 . 22 . 32 ) is produced in that the switching means together with the X-ray source ( 1 . 22 . 32 ) around the examination object ( 5 ) are relocatable.
  10. X-ray CT apparatus according to claim 8, wherein the unit of the switching means and the X-ray source ( 22 . 32 ) is produced in that the switching means at the X-ray source ( 22 . 32 ) are mounted.
  11. X-ray CT apparatus according to claim 8, wherein the unit of the switching means and the X-ray source ( 32 ) is produced in that the switching means in the interior of the vacuum housing ( 7 ) of the X-ray source ( 32 ) are included.
  12. X-ray CT apparatus according to claim 8, wherein the unit of the switching means and the X-ray source ( 32 ) is produced by the fact that the switching means in one with the X-ray source ( 32 ) connectable high voltage plugs or cables are integrated.
  13. X-ray CT device after one the claims 1 to 12, whose means for modulating the X-ray power the duration of Pulses for adjust each projection so that for each projection that to comply with a desired Signal / noise ratio required mAs product is achieved.
  14. X-ray CT apparatus according to one of Claims 1 to 13, which has a monitor detector ( 6 ) to which the X-ray source ( 1 . 22 . 32 ) emanates unattenuated X-ray radiation, wherein an electronic computing device ( 16 ) the angle attenuation profile using the output signals of the detector system and the monitor detector ( 6 ).
  15. X-ray CT apparatus according to one of claims 1 to 14, in which means are provided for determining the attenuation profile which together with the X-ray source ( 1 . 22 . 32 ) and the detector system around the examination object ( 5 ) are relocatable.
DE19933537A 1998-08-18 1999-07-16 X-ray computed tomography apparatus with means for modulating the x-ray power of an x-ray source Expired - Fee Related DE19933537B4 (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
DE19837443 1998-08-18
DE19837443.7 1998-08-18
DE19850493 1998-11-02
DE19850493.4 1998-11-02
DE19933537A DE19933537B4 (en) 1998-08-18 1999-07-16 X-ray computed tomography apparatus with means for modulating the x-ray power of an x-ray source

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE19933537A DE19933537B4 (en) 1998-08-18 1999-07-16 X-ray computed tomography apparatus with means for modulating the x-ray power of an x-ray source

Publications (2)

Publication Number Publication Date
DE19933537A1 DE19933537A1 (en) 2000-05-04
DE19933537B4 true DE19933537B4 (en) 2005-03-17

Family

ID=26048236

Family Applications (1)

Application Number Title Priority Date Filing Date
DE19933537A Expired - Fee Related DE19933537B4 (en) 1998-08-18 1999-07-16 X-ray computed tomography apparatus with means for modulating the x-ray power of an x-ray source

Country Status (2)

Country Link
JP (1) JP2000060839A (en)
DE (1) DE19933537B4 (en)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3964271B2 (en) * 2001-06-22 2007-08-22 株式会社モリタ製作所 Medical scanning digital X-ray imaging system
US6816567B2 (en) * 2002-07-15 2004-11-09 Ge Medical System Global Technology Company, Llc System and method for acquiring x-ray data
DE10346682B4 (en) * 2003-10-08 2005-11-17 Siemens Ag computed tomography
DE102004003532A1 (en) 2004-01-23 2005-08-18 Siemens Ag Three-dimensional structure determination method for use in determining the position of a structure in a patient, whereby at least two X-ray tube-detector combinations at fixed angles to each other are used simultaneously
US7274771B2 (en) * 2005-05-03 2007-09-25 General Electric Company Methods and systems for controlling exposure for medical imaging devices
DE102009004186A1 (en) * 2009-01-09 2010-01-07 Siemens Aktiengesellschaft X-ray tube, in a computer tomography apparatus, has an interruption in the electron beam between the cathode and anode between successive readings during a tube rotation around the test object
JP5812679B2 (en) * 2011-05-12 2015-11-17 株式会社東芝 X-ray computed tomography system

Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2815347A1 (en) * 1978-04-10 1979-10-18 Philips Patentverwaltung Method for determining the distribution of the absorption of radiation in a plane examination region
US4174481A (en) * 1976-03-31 1979-11-13 Siemens Aktiengesellschaft Tomographic X-ray apparatus for the production of transverse layer images
DE3741666A1 (en) * 1986-12-11 1988-08-04 Radiante Oy Circuit for x-ray tubes
DE2741240C2 (en) * 1976-09-16 1990-10-18 General Electric Co., Schenectady, N.Y., Us
DE4127983A1 (en) * 1991-08-23 1993-02-25 Bork Klaus Peter Method for generating contrasting diagnostic x-ray x-ray images and circuit arrangement therefor
US5379333A (en) * 1993-11-19 1995-01-03 General Electric Company Variable dose application by modulation of x-ray tube current during CT scanning
DE19527518A1 (en) * 1994-08-03 1996-02-08 Gen Electric X-ray tube modulation during computed tomography scanning
DE4430622A1 (en) * 1994-08-29 1996-03-07 Siemens Ag Cathode system for X=ray tube
DE19532535A1 (en) * 1994-09-06 1996-03-07 Gen Electric X=ray computer tomography patient dose reducing during acquisition of attenuation data of slice
DE3855687T2 (en) * 1988-09-13 1997-05-28 Optische Ind De Oude Delft Nv Compensation system for scanning radiography
DE19807639A1 (en) * 1997-04-01 1998-10-15 Siemens Ag Method for modulating the power of an X-ray tube of a computer tomograph (CT)

Patent Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4174481A (en) * 1976-03-31 1979-11-13 Siemens Aktiengesellschaft Tomographic X-ray apparatus for the production of transverse layer images
DE2741240C2 (en) * 1976-09-16 1990-10-18 General Electric Co., Schenectady, N.Y., Us
DE2815347A1 (en) * 1978-04-10 1979-10-18 Philips Patentverwaltung Method for determining the distribution of the absorption of radiation in a plane examination region
DE3741666A1 (en) * 1986-12-11 1988-08-04 Radiante Oy Circuit for x-ray tubes
DE3855687T2 (en) * 1988-09-13 1997-05-28 Optische Ind De Oude Delft Nv Compensation system for scanning radiography
DE4127983A1 (en) * 1991-08-23 1993-02-25 Bork Klaus Peter Method for generating contrasting diagnostic x-ray x-ray images and circuit arrangement therefor
US5379333A (en) * 1993-11-19 1995-01-03 General Electric Company Variable dose application by modulation of x-ray tube current during CT scanning
DE19527518A1 (en) * 1994-08-03 1996-02-08 Gen Electric X-ray tube modulation during computed tomography scanning
DE4430622A1 (en) * 1994-08-29 1996-03-07 Siemens Ag Cathode system for X=ray tube
DE19532535A1 (en) * 1994-09-06 1996-03-07 Gen Electric X=ray computer tomography patient dose reducing during acquisition of attenuation data of slice
DE19807639A1 (en) * 1997-04-01 1998-10-15 Siemens Ag Method for modulating the power of an X-ray tube of a computer tomograph (CT)

Also Published As

Publication number Publication date
JP2000060839A (en) 2000-02-29
DE19933537A1 (en) 2000-05-04

Similar Documents

Publication Publication Date Title
JP6057188B2 (en) Cone beam computed tomography system and subject imaging method
US8199883B2 (en) X-ray flux management device
JP3487599B2 (en) Improved X-ray volumetric CT scanner
JP3197560B2 (en) Method for improving the dynamic range of an imaging device
US8699657B2 (en) X-ray examination apparatus and method
US7684538B2 (en) X-ray scanning system
JP3449561B2 (en) X-ray CT system
US6370217B1 (en) Volumetric computed tomography system for cardiac imaging
US6421411B1 (en) Methods and apparatus for helical image artifact reduction
US5867553A (en) Computed tomography scanner with reduced power x-ray source
US7751528B2 (en) Stationary x-ray digital breast tomosynthesis systems and related methods
US5835561A (en) Scanning beam x-ray imaging system
JP4759255B2 (en) Static computed tomography system and method
DE19807639C2 (en) Method for modulating the power of an X-ray tube of a computer tomograph (CT)
EP1762176B1 (en) X-ray computed tomography apparatus
US8031831B2 (en) Voltage and or current modulation in dual energy computed tomography
US7227923B2 (en) Method and system for CT imaging using a distributed X-ray source and interpolation based reconstruction
US7260252B2 (en) X-ray computed tomographic apparatus, image processing apparatus, and image processing method
EP2271189B1 (en) High speed modulation of switched-focus X-ray tube
EP1848985B1 (en) Multiple mode flat panel x-ray imaging system
EP1374776B1 (en) Methods and apparatus for operating a radiation source
US6980626B2 (en) X-ray arrangement and operating method for compensating scattered radiation
JP4187289B2 (en) Method and system for modulating x-ray tube current and system for dynamically adjusting at least one component of a computed tomography imaging system
US6990175B2 (en) X-ray computed tomography apparatus
US7778383B2 (en) Effective dual-energy x-ray attenuation measurement

Legal Events

Date Code Title Description
8120 Willingness to grant licences paragraph 23
8110 Request for examination paragraph 44
8364 No opposition during term of opposition
8339 Ceased/non-payment of the annual fee
R119 Application deemed withdrawn, or ip right lapsed, due to non-payment of renewal fee

Effective date: 20110201