EP0022295A1 - Procédé de commande de la puissance électrique appliquée à un tube à rayons X à anode tournante - Google Patents

Procédé de commande de la puissance électrique appliquée à un tube à rayons X à anode tournante Download PDF

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Publication number
EP0022295A1
EP0022295A1 EP80200625A EP80200625A EP0022295A1 EP 0022295 A1 EP0022295 A1 EP 0022295A1 EP 80200625 A EP80200625 A EP 80200625A EP 80200625 A EP80200625 A EP 80200625A EP 0022295 A1 EP0022295 A1 EP 0022295A1
Authority
EP
European Patent Office
Prior art keywords
temperature
limit value
power
anode
ray tube
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.)
Granted
Application number
EP80200625A
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German (de)
English (en)
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EP0022295B1 (fr
Inventor
Rudolf Ochmann
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.)
Philips Intellectual Property and Standards GmbH
Koninklijke Philips NV
Original Assignee
Philips Patentverwaltung GmbH
Philips Gloeilampenfabrieken NV
Koninklijke Philips Electronics NV
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Philips Patentverwaltung GmbH, Philips Gloeilampenfabrieken NV, Koninklijke Philips Electronics NV filed Critical Philips Patentverwaltung GmbH
Publication of EP0022295A1 publication Critical patent/EP0022295A1/fr
Application granted granted Critical
Publication of EP0022295B1 publication Critical patent/EP0022295B1/fr
Expired legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05G—X-RAY TECHNIQUE
    • H05G1/00—X-ray apparatus involving X-ray tubes; Circuits therefor
    • H05G1/08—Electrical details
    • H05G1/26—Measuring, controlling or protecting
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05G—X-RAY TECHNIQUE
    • H05G1/00—X-ray apparatus involving X-ray tubes; Circuits therefor
    • H05G1/08—Electrical details
    • H05G1/26—Measuring, controlling or protecting
    • H05G1/30—Controlling
    • H05G1/36—Temperature of anode; Brightness of image power

Definitions

  • the invention relates to a method for controlling the electrical power supplied to a rotating anode x-ray tube in an x-ray generator as a function of the anode temperature of the x-ray tube, the respective anode disc temperature being continuously determined and compared with a first limit value, the electrical power supplied to the x-ray tube is automatically lowered when the anode disc temperature exceeds the first limit value.
  • Such a method is essentially known from DE-OS 22 08 871. However, it is not the anode disk temperature that is determined (this is the temperature that the anode disk assumes when the heat supplied in the focal spot has been distributed at least approximately evenly over the entire disk), but the temperature in the focal spot.
  • An analog computing circuit is provided to determine the temperature. A digital calculator could just as well be used for this; the temperature could also be determined by measurement.
  • the tube power is regulated so that the focal spot temperature just corresponds to the limit.
  • the recording times for the same object are constantly changing in this limit range of the load, and it is not possible to achieve reproducibility with regard to the motion blur of the object.
  • this method does not take into account that, even if the focal spot temperature is constantly checked, the rotating anode bearing, which is connected to the anode disk via a shaft with a comparatively high thermal resistance, can assume temperatures that lead to bearing damage and thus to a shortened lifespan of the x-ray tube. Despite monitoring the focal spot temperature, the X-ray tube is therefore not always protected against overload.
  • DE-OS 20 31 590 it is known from DE-OS 20 31 590 to control a display device as a function of the anode temperature reached with a radiation measuring probe so that the remaining fraction of the permissible load on the cold X-ray tube is displayed.
  • the user is forced to convert the recording parameters of his next recording into percentages for comparison and to reset his parameters taking into account the specified limits, which is too complex and time-consuming for routine operation.
  • this object is achieved according to the invention in that the power is automatically reduced to a predetermined constant fraction of the respective permissible power, in that the power is reduced in the recording pauses, in that the anode disk temperature has a second limit value above the first is compared and that the tube power is reduced to a second predetermined constant fraction, preferably the value zero, when the anode disk temperature exceeds the second limit value during a recording pause, that the temperature of the rotating anode bearings is continuously determined and compared with a third limit value and that the triggering of the recording is blocked as long as the determined storage temperature exceeds the third limit value.
  • the electrical power supplied to the X-ray tube is automatically reduced to a fixed fraction of the permissible power by automatic control of the actuators for the tube current and possibly for the tube voltage.
  • the allowable power is the power with which the X-ray tube can just be operated at the temperature corresponding to the first limit value, without the X-ray tube being overloaded by melting processes in the focal spot path.
  • the permissible output with a recording time of 0.1 s or less is 50 kW; if the recording time increases, then the permissible power becomes correspondingly lower - and likewise of course the fraction of this permissible power that is supplied to the X-ray tube when the anode disk temperature has exceeded the first limit value.
  • the reduction in output does not take place during an admission, but in the admission breaks. If the next recording only begins after the anode disk temperature has fallen below the first limit value again, the power supplied to the X-ray tube is automatically increased to the respectively permissible value - as with the known methods.
  • the introduction of a second limit value for the anode disk temperature ensures that the X-ray tube cannot be overloaded even by the reduced power.
  • the second limit value and the fraction to which the power is reduced must therefore be coordinated with one another so that at the second limit value the X-ray tube can be loaded with the aforementioned fraction of the permissible power without damage occurring.
  • the temperature of the rotating anode bearings is also continuously determined and compared with a permissible storage temperature ensures that when the electrical power supplied per exposure is relatively low, the mean time value supplied to the X-ray tube during the individual exposures and fluoroscopy Power but is relatively high - in this case the second limit is the Anode disk temperature mostly not reached - the X-ray tube cannot be destroyed. In some cases, however, it can also happen that - before the bearing temperature reaches the third limit - the connection point (eg a soldering point) of the rotor with the shaft on which the anode disk is seated - exceeds a critical value. Then the temperature at this connection point must be monitored instead of the storage temperature. In both cases, this boils down to the fact that the electrical power supplied - averaged over a period of a few minutes - must not exceed a limit value.
  • the connection point eg a soldering point
  • the first limit value corresponds to the temperature, which the anode disk temperature approaches with an average exposure power of approximately 250 W during continuous exposure.
  • the load capacity of a tube - e.g. 50 kW (in 0.1 s or less) with a 50 kW tube - is not the maximum permissible output with a cold anode disc - a higher load would be possible with a cold anode disc - , but the power that is just permissible after a long period of fluoroscopy, after which the anode disk can have reached a temperature of a few 100 ° C., without damaging the anode disk.
  • the first limit value of the anode plate temperature is 500 0 C or higher, depending on whether the anode plate is roughened or blackened - in this case, a greater power is emitted, so that the anode plate remains cooler - or not.
  • the output is reduced by only lowering the tube current, the images taken with the power reduced in this way retain their character, but the exposure time is extended if the same blackening or the same mAs product is to be achieved.
  • An extension of the exposure Duration is, however, not permitted in many cases, for example in the case of slice shots in which a certain recording time is fixed.
  • a development of the invention therefore provides that the power is reduced by increasing the voltage at the x-ray tube by a predeterminable fraction and at the same time reducing the tube current by three to five times this fraction.
  • the electrical power supplied to the X-ray tube is reduced, but not the dose rate generated by the X-ray tube.
  • the dose rate changes linearly with the tube current, but with the third to fifth power of the voltage, so that the tube current drop in relation to the dose rate is compensated for again by increasing the voltage on the X-ray tube. Since the dose rate thus remains approximately constant, it is possible in this case to work with the same exposure time even when there is a change in power; however, the recording character changes due to the change in the voltage on the X-ray tube.
  • Fig. 1 shows the time course of the different temperatures.
  • Tg 1 denotes the first limit value of the anode disk temperature.
  • This limit value of the anode plate temperature is the value which the anode plate temperature approaches asymptotically when it is subjected to an average fluoroscopic power, for example 250 W.
  • the usual X-ray tubes are designed so that they have the power for which they are intended for (ie for a 30 kW tube for 0.1 s or less 30 kW), can still be processed without overloading.
  • the second limit is designated Tg 2 .
  • the X-ray tube is not overloaded if the anode disk temperature corresponds to this limit value and approximately 80% of the electrical power permissible at the first limit value of the anode disk temperature is supplied to the X-ray tube.
  • T a2 denotes the profile of the anode disk temperature, which results when the X-ray tube is continuously supplied with the electrical power which is still permissible without leading to the destruction of the tube bearings. It strives for a limit value Tg l that lies between the first limit value Tg 1 and the second limit value Tg 2 . In a typical X-ray tube without roughening or blackening of the anode disk or rotor surfaces, the latter two limit values are 780 ° or 1050 ° C. T 1 indicates the course of the temperature which arises in the bearing when the mentioned power is applied to the X-ray tube. In this case, the storage temperature strives asymptotically to a limit value T l g.
  • the X-ray recording is carried out with the full power permissible for this temperature. If the anode disc temperature lies between the limit values Tg 1 and Tg 2 during a recording pause, the power is reduced, ie the actuators for the tube voltage and the tube current are controlled so that the electrical power that can be set with them is just 80% of that below the limit value Tg 1 permissible electrical power. If the determined anode disc temperature falls below the first limit value during the recording pause, the electrical power that can be supplied is increased again to the full value. - The anode disc temperature is above during a recording pause of the second limit value, the recording is blocked until at least the temperature Tg 2 falls below again.
  • the block diagram in FIG. 2 represents an X-ray generator for executing the method according to the invention
  • Rotating anode x-ray tube 1 is connected to a high voltage generator 2. This is connected to a low-voltage actuator 60 via a time switch 30.
  • the electronically controlled heating circuit 5 receives its setpoint via line 8 from a function transmitter 20 for the tube nomograms, which in turn receives the setting signals from the transmitters 14, 15, 16 arranged on the control panel 10 for entering the recording parameters (tube voltage, tube current, recording time).
  • the function generator is used in a known manner (DE-OS 21 58 865) to generate the tube loading nomograms for the different X-ray tubes and possibly for different focal spots within the individual X-ray tubes, but only for one image.
  • this can be a signal that falls continuously after an initial time (0.1 s), corresponding to an X-ray image with continuously decreasing power, or a constant value, for example when a recording with constant current is set on the control panel 10.
  • the actual values of the tube current required for the tube current control are supplied by a sensor I, which is contained in the high-voltage generator.
  • the reference variable or the desired value is fed to line 8 via an amplifier 21 contained in the function generator 20 with a gain which can be set in stages. The gain of this amplifier remains constant during a recording.
  • the function provider determines from this and from the tube power the tube current required for this power, which decreases over time ("falling load") and this value is given via the amplifier 21 to the line 8 for the reference variable of the tube current control circuit.
  • the size of the guide values also depends on the amplification of the amplifier 21 that is set in each case.
  • the gain of the amplifier 21 is controlled depending on the temperature of the anode disk, the anode bearing and the X-ray tube housing.
  • the computing circuit 110 can consist of a network, of resistors and capacitors, which simulates the course of the anode temperature.
  • a signal is fed to the computing circuit 110 at its input 111 via a line 71, which signal corresponds to the instantaneous value of the electrical power supplied to the X-ray tube and which has the value zero during a pause in imaging and fluoroscopy.
  • the signal is generated by a multiplier 70 which forms the product of tube voltage (U) and tube current during the recording or the fluoroscopy.
  • the components used in the computing circuit 110 correspond to the thermal parameters of the Dimension the anode disk of the X-ray tube; when using multiple X-ray tubes or an X-ray tube with multiple focal spots, these components can be switched accordingly.
  • the voltage that can be attacked at output 112 is an approximate representation of the respective anode disk temperature. It is given on the one hand at the input of a second computing circuit 120 to simulate the rotating anode storage temperature, the elements of which can also be adjusted to the thermal parameters of the X-ray tube, and on the other hand at the inputs of two comparison stages 40 and 41, which respond when the one supplied by computing circuit 110 Value corresponds to the first limit value (T a1 ) or the second limit value (Tg2).
  • the computing circuit 120 is designed in such a way that - if a signal is continuously supplied via the line 71 which corresponds to the continuous output which is still permissible with regard to the heating of the bearings - the output signal of the computing circuit 120 strives for a limit value which corresponds to the limit value Tlg.
  • This signal present on line 122 is fed to the input of a further comparison device 42, which responds as soon as the mentioned limit value is reached.
  • the computing circuit 120 can contain an input 121, into which a current is fed each time the rotating anode is started or braked, which comprises the proportion of the starting or braking power that is inductively transmitted to the rotor.
  • a signal is supplied to the input of a third arithmetic circuit 130, which simulates the housing temperature, and corresponds to the thermal output resulting from the existing heat transfer resistances.
  • the arithmetic circuit 130 is connected to the arithmetic circuit 110 via the line 115 and receives from it a signal which corresponds to the heat output radiated from the anode disk.
  • the exit of the arithmetic circuit 130 for the housing temperature is connected to the input of a fourth comparison stage 43.
  • the ambient temperature can be simulated by an optionally adjustable voltage source, which in the simplest case can be realized by a suitable tens diode.
  • the output of the computing circuit 130 is connected to a fourth comparison stage 43, which responds when the voltage at the output corresponds to a predefinable limit value of the housing temperature.
  • the computing circuit 130 can be replaced by a suitable temperature sensor, which measures the housing temperature.
  • the computing circuits 110 and 120 could also be replaced by temperature sensors which measure the anode disk temperature or the bearing temperature, but such a measurement is considerably more difficult than the simulation or the calculation of the corresponding temperatures.
  • the outputs 45, 46, 47 and 48 of the comparison stages 40, 41, 42 and 43 are connected to control inputs of the function generator 20 and control the gain of the amplifier 21 with adjustable gain via a suitable linking network.
  • This control which is only effective during the recording pauses, is carried out in such a way that the amplification is set to zero when at least one of the comparison stages 41, 42 or 43 has responded, ie when the anode disk temperature has exceeded the second limit value Tg 2 when the Storage temperature has exceeded its limit value and / or if the limit temperature of the housing has been exceeded.
  • the gain of the adjustable amplifier 21 set to 80%.
  • the reference variable for the tube current is reduced to 80% of the value which would still be permissible below the first limit value given the setting on the control panel 10 and the given load capacity of the X-ray tube.
  • a fast simulation in time-lapse operation is started with the aid of a second simulation network.
  • the second network 200 also has three computing circuits 210, 220, 230, the structure of which is identical to that of the computing circuits 110, 120 and 130, but whose time constant differs from that of the computing circuits 110, 120 and 130 by a constant factor , which is significantly larger than 1. If one of the comparison stages corresponds to 40 to 43, a fast simulation cycle begins, in which the computing circuits are set via the voltage sequence 112, 122, 132 to the (real time) temperatures determined by the computing circuits 110, 120 and 130 and then simulate the cooling process.
  • Circuit 50 controls a gate through which a generator with a frequency matched to the time-lapse factor counts up a waiting time counter with display 17 on the control panel.
  • the waiting time counter contains the waiting time which is required in order to be able to carry out a recording again with 100% of the power.
  • the waiting time counter is counted down again in real time so that the current waiting time is displayed at every moment.
  • the simulation network 100, the fast simulation network 200, the comparison stages 40 ... 43 and the function generator 20 are advantageously implemented with the aid of a microprocessor.
  • the calculation of the different temperatures in real-time and time-lapse operation is particularly simple, because for time-lapse operation, the calculation steps only have to be carried out in faster succession than corresponds to the time increment used for real-time calculation of the temperatures; the time increment can also be chosen larger for the time-lapse simulation.
  • FIG. 3 shows the time course of the temperature T a on the anode disk and the temperature (T l ) on the bearing of a rotating anode X-ray tube during a typical X-ray examination.
  • the temperature T a of the anode disk rises almost abruptly (in reality the temperature increase per unit of time is proportional to the instantaneous value of the power supplied to the X-ray tube), the height of the jump depending on the energy supplied during an exposure. It can be seen that the temperature of the anode disk decreases approximately exponentially during the recording pauses, but much more slowly than it increases during a recording.
  • the temperature of the anode disk exceeds both the first and the second limit values Tg 1 and Tg 2 .
  • the comparison therefore speak stage 40 and 41, and a fast simulation cycle is triggered, and the user is shown on the control panel on the display 17 how long he has to wait until he can take up again at full power.
  • the comparison stage 41 After the anode disk temperature has fallen below the second limit value T g2 , the comparison stage 41 returns to the idle state, that is to say the recording lock is released and only the comparison stage 40 is effective, so that from then on a recording can be carried out - even if with 80% reduced performance.
  • the bearing temperature T i changes relatively slowly compared to the anode plate temperature due to the existing heat transfer resistance between the anode plate and the bearings. It exceeds the storage temperature limit value T l g after the end of the sixth exposure (comparison stage 42 also responds) and its temperature then rises to a maximum without electrical power being supplied to the X-ray tube during this time. Therefore, the limit value T l g of the storage temperature must be selected somewhat below the maximum permissible storage temperature. After the anode disk temperature T a has fallen below the second limit value again, the comparison stage 41 returns to its original state, but the comparison stage 42 then remains in the response state.

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  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • X-Ray Techniques (AREA)
EP80200625A 1979-07-05 1980-07-01 Procédé de commande de la puissance électrique appliquée à un tube à rayons X à anode tournante Expired EP0022295B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE2927207 1979-07-05
DE19792927207 DE2927207A1 (de) 1979-07-05 1979-07-05 Verfahren zum steuern der einer drehanoden-roentgenroehre zugefuehrten elektrischen leistung

Publications (2)

Publication Number Publication Date
EP0022295A1 true EP0022295A1 (fr) 1981-01-14
EP0022295B1 EP0022295B1 (fr) 1983-12-28

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EP80200625A Expired EP0022295B1 (fr) 1979-07-05 1980-07-01 Procédé de commande de la puissance électrique appliquée à un tube à rayons X à anode tournante

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US (1) US4363971A (fr)
EP (1) EP0022295B1 (fr)
CA (1) CA1165008A (fr)
DE (2) DE2927207A1 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2530019A1 (fr) * 1982-07-09 1984-01-13 Thomson Csf Procede de determination du niveau calorifique d'une anode tournante et ensemble electronique permettant la mise en oeuvre de ce procede
FR2585917A1 (fr) * 1985-08-02 1987-02-06 Thomson Cgr Procede de reglage d'un dispositif de radiologie
FR2635633A1 (fr) * 1988-08-19 1990-02-23 Varian Associates Dispositif de controle d'un appareil a rayons x
EP0624052A1 (fr) * 1993-05-07 1994-11-09 Kabushiki Kaisha Toshiba Système générateur de rayons X

Families Citing this family (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3021048A1 (de) * 1980-06-03 1981-12-10 Siemens AG, 1000 Berlin und 8000 München Antrieb fuer drehanoden von roentgenroehren
WO1986003363A1 (fr) * 1984-11-21 1986-06-05 Medicor Dispositif de reglage des parametres d'exposition d'un equipement radiologique
US5077772A (en) * 1990-07-05 1991-12-31 Picker International, Inc. Rapid warm-up x-ray tube filament power supply
DE4401066A1 (de) * 1994-01-15 1995-07-20 Philips Patentverwaltung Röntgenstrahler mit einem Temperaturfühler
JP2885398B2 (ja) * 1997-04-01 1999-04-19 株式会社東芝 Ｘ線装置
CN102772220B (zh) * 2012-06-20 2014-03-12 孙维俊 一种便携式牙科x光机
DE102013219633A1 (de) * 2013-09-27 2014-10-02 Siemens Aktiengesellschaft Vorrichtung und Verfahren zur Temperaturüberwachung eines Röntgenstrahlers eines medizinischen bildgebenden Gerätes und medizinisches bildgebendes System mit Temperaturüberwachung eines Röntgenstrahlers
JP2019110014A (ja) * 2017-12-18 2019-07-04 株式会社アキュセラ Ｘ線装置およびｘ線装置の制御方法
CN108093549B (zh) * 2017-12-26 2019-08-06 南宁一举医疗电子设备股份有限公司 X射线管透视灯丝电流上下限值自校准方法
DE102022116528A1 (de) 2022-07-01 2024-01-04 Aesculap Ag Intelligentes Temperaturmodell

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DE2031590A1 (de) * 1970-06-26 1971-12-30 Siemens Ag Belastungsanzeige für die. Anode einer Röntgenröhre
DE2208871A1 (de) * 1971-02-26 1973-10-25 Koch & Sterzel Kg Roentgenapparat
DE2510984A1 (de) * 1975-03-13 1976-09-30 Hofmann Gmbh Elektr Fritz Roentgendiagnostikapparat mit roentgenroehrenschutzschaltung

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FR1152414A (fr) 1956-06-19 1958-02-17 Radiologie Cie Gle Dispositif de protection pour tubes radiogènes
US3746862A (en) 1970-11-30 1973-07-17 Picker Corp Protective circuit for x-ray tube and method of operation
DE2345947C3 (de) 1973-09-12 1981-12-03 Philips Patentverwaltung Gmbh, 2000 Hamburg Schaltungsanordnung zur Überwachung der Belastung einer Röntgenröhre
DE2721535A1 (de) 1977-05-13 1978-11-16 Philips Patentverwaltung Roentgengenerator
US4158138A (en) * 1977-10-25 1979-06-12 Cgr Medical Corporation Microprocessor controlled X-ray generator

Patent Citations (3)

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Publication number Priority date Publication date Assignee Title
DE2031590A1 (de) * 1970-06-26 1971-12-30 Siemens Ag Belastungsanzeige für die. Anode einer Röntgenröhre
DE2208871A1 (de) * 1971-02-26 1973-10-25 Koch & Sterzel Kg Roentgenapparat
DE2510984A1 (de) * 1975-03-13 1976-09-30 Hofmann Gmbh Elektr Fritz Roentgendiagnostikapparat mit roentgenroehrenschutzschaltung

Non-Patent Citations (1)

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Title
ELECTROMEDICA, Band 46, Nr. 3, 1978, Seiten 84-87 Erlangen, DE. G. APPELT et al.: "Eine oberste Leistungsbegrenzung bei Drehanodenrotgenrohren" * Zusammenfassung * *

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2530019A1 (fr) * 1982-07-09 1984-01-13 Thomson Csf Procede de determination du niveau calorifique d'une anode tournante et ensemble electronique permettant la mise en oeuvre de ce procede
FR2585917A1 (fr) * 1985-08-02 1987-02-06 Thomson Cgr Procede de reglage d'un dispositif de radiologie
EP0214887A1 (fr) * 1985-08-02 1987-03-18 General Electric Cgr S.A. Procédé de réglage d'un dispositif de radiologie
US4774720A (en) * 1985-08-02 1988-09-27 Thomson-Cgr Method for adjusting an x-ray device
FR2635633A1 (fr) * 1988-08-19 1990-02-23 Varian Associates Dispositif de controle d'un appareil a rayons x
EP0624052A1 (fr) * 1993-05-07 1994-11-09 Kabushiki Kaisha Toshiba Système générateur de rayons X

Also Published As

Publication number Publication date
EP0022295B1 (fr) 1983-12-28
US4363971A (en) 1982-12-14
CA1165008A (fr) 1984-04-03
DE3065995D1 (en) 1984-02-02
DE2927207A1 (de) 1981-01-08

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