EP0489060B1 - Röntgenaufnahmegerät mit schlitzblenden - Google Patents

Röntgenaufnahmegerät mit schlitzblenden Download PDF

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Publication number
EP0489060B1
EP0489060B1 EP90912526A EP90912526A EP0489060B1 EP 0489060 B1 EP0489060 B1 EP 0489060B1 EP 90912526 A EP90912526 A EP 90912526A EP 90912526 A EP90912526 A EP 90912526A EP 0489060 B1 EP0489060 B1 EP 0489060B1
Authority
EP
European Patent Office
Prior art keywords
tongue
tongues
bridge
piezoelectric
measuring circuit
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 - Lifetime
Application number
EP90912526A
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English (en)
French (fr)
Other versions
EP0489060A1 (de
Inventor
Ronald Jan Geluk
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.)
Optische Industrie de Oude Delft NV
Original Assignee
Optische Industrie de Oude Delft NV
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Filing date
Publication date
Application filed by Optische Industrie de Oude Delft NV filed Critical Optische Industrie de Oude Delft NV
Publication of EP0489060A1 publication Critical patent/EP0489060A1/de
Application granted granted Critical
Publication of EP0489060B1 publication Critical patent/EP0489060B1/de
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Classifications

    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
    • G21K1/00—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating
    • G21K1/02—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating using diaphragms, collimators
    • G21K1/04—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating using diaphragms, collimators using variable diaphragms, shutters, choppers
    • 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

Definitions

  • the invention relates to a slit radiography apparatus, provided with an absorption device which operates in conjunction with a slit diaphragm and which comprises electrically controllable piezo-electric tongues, and also with a control device which provides electrical control signals for the tongues.
  • the known apparatus comprises an X-ray source which is capable of scanning a patient or object to be examined with a flat fan-shaped X-ray beam via a slit-type diaphragm.
  • an absorption device which comprises a number of adjacently situated absorption elements which can be inserted to a greater or lesser degree in the X-ray beam under the control of electrical control signals.
  • Each absorption element is capable of affecting a sector of the fan-shaped X-ray beam.
  • the control signals are obtained by means of a detector which is provided behind the patient or the object and which measures the amount of radiation transmitted per sector of the X-ray beam and provides appropriate electrical control signals.
  • tongues of piezoelectric material which are clamped at one end and whose other end can be swivelled into the X-ray beam under the control of the above-mentioned electrical control signals.
  • Such tongues already absorb X-ray radiation to a certain degree themselves, but they can be provided at the free ends with special elements which absorb X-ray radiation.
  • the tongues may be simple tongues of piezoelectric material which can be brought to a curved configuration by means of an electrical control voltage applied between the top and bottom face.
  • the tongues may also be so-called bimorphous elements which are composed of two strips of piezoelectric material laid on top of each other. The electrical control voltage is then between the outside faces (top and bottom face) which are connected to each other and the common central face.
  • the tongues react rapidly and accurately to the electrical control signals. It has been found that the tongues may commence resonance vibration, as a result of which the tongues become uncontrollable and may even break. Although such uncontrolled vibrations can be prevented by filtering the control signals concerned, the use of a filter suitable for this purpose also results in a relatively sluggish control of the tongues.
  • an apparatus of the type described is characterized by a damping device which receives the control signals for the tongues and which comprises for each tongue an E.M.F. (Electro Motive Force) measuring circuit which interacts with it and which provides, during operation, an output signal which represents the counter-E.M.F. generated by a tongue, which output signal is combined with the control signal for the tongue concerned.
  • E.M.F. Electro Motive Force
  • EP-A-0155065 describes various methods for damping tongue-type absorption elements or tongue-type carriers of absorption elements with the aid of mechanical means or with the aid of eddy currents generated in metal vanes attached to the tongues.
  • these known techniques are less suitable for tongues of piezoelectric material, which is relatively brittle, and require, in addition, an appreciable amount of extra space in the absorption device.
  • Fig. 1 shows diagrammatically in side elevation an example of a (known) slit radiography apparatus provided with an absorption device.
  • the apparatus shown comprises an X-ray source 1 which is capable of scanning a patient 4 or an object to be examined in the direction, indicated by arrows 5, transversely to the plane of the fan-shaped beam 3 via a slit-type diaphragm 2.
  • An X-ray detector 6, which may comprise, for example, an X-ray film cassette or a concomitantly moving oblong X-ray image intensifier tube, picks up the radiation transmitted through the patient and effects the formation of the desired X-ray shadow image.
  • the scanning in accordance with the arrows 5 takes place because, during operation, the X-ray source swivels about an axis, as indicated by an arrow 7, extending transversely to the plane of the drawing, preferably through the X-ray focus of the X-ray source.
  • an absorption device 8 which is capable of modulating the X-ray beam per sector.
  • the absorption device comprises adjacently situated piezoelectric tongues, also known as piezoceramic tongues because the tongues are manufactured from ceramic material having piezoelectric properties.
  • An example of such a tongue is shown in Fig. 2.
  • Each tongue is capable of affecting a particular sector of the X-ray beam 3.
  • the necessary control signals are provided by a detector 9 which is situated, in this example, between the patient and the X-ray detector and which picks up the radiation transmitted through the patient at every instant and provides per sector of the X-ray beam electrical signals which are supplied via a processing circuit 10 to the corresponding tongues.
  • the detector may be an oblong radiation detector which moves synchronously with the scanning movement of the X-ray beam but it can also be a two-dimensional stationary detector.
  • Fig. 2 shows diagrammatically in side elevation a piezoceramic tongue 11 of the bimorphous type composed of two strips 12, 13 of piezoelectric material mounted on each other.
  • the strip shown is clamped in a carrier 14 near an end and, in this example, is provided with an absorption element 15 at the free end.
  • Broken lines indicate a possible working position.
  • the tongue is controlled by a control voltage Ve which is applied during operation between two terminals 16, 17, of which one is connected to the central face 18 between the two strips 12, 13 and the other to the two outside faces 19, 20 of the strips.
  • Fig. 3 shows, by way of example, a block diagram of a control circuit for the piezoceramic tongues.
  • the invention is based on the insight that a piezoelectric tongue generates, during operation, a counter-E.M.F. which is dependent on the curvature of the tongue. It should be possible to derive from this counter-E.M.F. a damping signal for the tongue concerned which is capable of preventing tongue resonance phenomena.
  • the counter-E.M.F. of each tongue is continuously measured and an electrical signal derived from the instantaneous counter-E.M.F. is subtracted from the control signal provided for the tongue concerned by the detector 9 after a possible preprocessing. All this is shown diagrammatically in Fig. 3.
  • the control signal provided by the detector 9, optionally after a preprocessing is present at the input 31 of the control circuit 30 shown. Said signal is fed via a feedback point 32 to an amplifier 33 whose output is fed to a E.M.F. measuring circuit 34 still to be described in more detail.
  • the E.M.F. measuring circuit 34 is coupled to a piezoelectric tongue which is diagrammatically indicated by the block 35.
  • the E.M.F. measuring circuit forms, in a way still to be described in detail, a signal which is dependent on the instantaneous counter-E.M.F. of the tongue concerned and which is fed with a negative sign to the feedback point 32 via a feedback amplifier 36.
  • the counter-E.M.F is dependent on the movement of the tongue, with the result that the control circuit 30 forms a so-called motional feedback system.
  • a feedback signal representing the counter-E.M.F. of a tongue during operation can be obtained with the aid of a circuit of the type shown, for example, in Fig. 4.
  • Fig. 4 shows a bridge circuit having four branches 40 to 43 inclusive.
  • Branch 41 comprises two connecting points 44, 45 which are connected during operation to the tongue 46 to be controlled.
  • the branches 42 and 43 both comprise a resistor R which may be, for example, 10 k ⁇ in a practical situation.
  • the bridge can be used to measure the counter-E.M.F. of the tongue 46.
  • the output signal provided by the amplifier 33 is fed between the vertices 47 (junction point of the branches 40 and 41) and 48 (junction point of the branches 42 and 43). Said signal also controls the tongue 46.
  • a feedback signal which is a measure of the counter-E.M.F. of the tongue 46 is produced between the other vertices 49 and 50 of the bridge circuit. Said signal is fed to a difference amplifier which corresponds to the feedback amplifier 36 of Fig. 3 or can be conceived as incorporated therein.
  • the component Q may be a capacitor because piezo-ceramic tongues are capacitive to a first approximation. -
  • a piezoceramic tongue similar to the tongue to be controlled is used as component Q.
  • the tongue used as component Q is, however, fully clamped, with the result that it cannot yield a counter-E.M.F. generated by movement.
  • the signal present between the vertices 49 and 50 is then due entirely to the counter-E.M.F. of the tongue 46.
  • the tongues are capacitive and the other branches 42, 43 of the bridge in the example shown contain resistors R, the output signal of the bridge is proportional to the differentiated input signal of the bridge.
  • the feedback signal is therefore proportional to the velocity of movement of the tongue 46.
  • the movement of a tongue can be controlled very well with such a feedback signal, while a rapid response of the tongue to control signals is nevertheless guaranteed.
  • the resistors R in the bridge circuit can be replaced by capacitors.
  • the output signal of the bridge is not proportional to the velocity of movement but to the time integral thereof, namely deviation of the free tongue end.

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  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Apparatus For Radiation Diagnosis (AREA)

Claims (6)

  1. Schlitzradiographiegerät versehen mit einer Absorptionsvorrichtung, die in Verbindung mit einer Schlitzblende (2) arbeitet und die elektrisch steuerbare Piezo-Zungen (8, 11, 35) umfaßt, und ferner mit einer Steuerungsvorrichtung (10) welche elektrische Steuersignale für die Zungen liefert, dadurch gekennzeichnet, daß eine Dämpfungsvorrichtung, welche die Steuersignale für die Zungen empfängt und für jede Zunge (35) einen Meß-Kreis (34) für elektromotorische Kraft (E.M.K.) enthält, der mit ihr in Wechselwirkung steht und während des Betriebes ein Ausgangssignal liefert, welches die elektromotorische Gegenkraft darstellt, die von einer Zunge (35) erzeugt wurde, welches Ausgangssignal mit dem Steuersignal für die betreffende Zunge kombiniert wird.
  2. Gerät nach Anspruch 1, dadurch gekennzeichnet, daß die Dämpfungsvorrichtung für jede Zunge (35) einen Regelkreis aufweist mit einem Eingang (31) für das Steuersignal für die betreffende Zunge und mit einem Rückkopplungspunkt (32), in welchen das Ausgangssignal des E.M.K.-Meß-Kreises (34) eingespeist wird mit negativem Vorzeichen über einen rückgekoppelten Verstärker (36), mit einem Verstärker (33), der das Ausgangssignal vom Rückkopplungspunkt in den Eingang des E.M.K.-Meß-Kreises (34) einspeist, und daß der Meß-Kreis (34) auch das gedämpfte Steuersignal für die Zunge (35) liefert.
  3. Gerät nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß der E.M.K.-Meß-Kreis (34) eine Brückenschaltung mit zwei parallelen Sets aufweist, die zwischen zwei Eingangsanschlüssen (47, 48) angeschlossen sind, von denen jeder der zwei Brückenzweige über einen Verbindungspunkt (49, 50) in Reihe geschaltet ist, wobei ein erstes Set von Brückenzweigen einen ersten Brückenzweig (Q), der eine Baugruppe besitzt, die das elektrische Verhalten einer piezoelektrischen Zunge darstellt, und einen zweiten Brückenzweig, der einen Widerstand (R) enthält, und ein zweites Set von Brückenzweigen einen dritten Brückenzweig, der die anzusteuernde Zunge (46) enthält, und einen vierten Zweig, der einen Widerstand (R) enthält, aufweist.
  4. Gerät nach Anspruch 3, dadurch gekennzeichnet, daß die Baugruppe (Q), die das elektrische Verhalten einer piezoelektrischen Zunge darstellt, ein Kondensator ist.
  5. Gerät nach Anspruch 3, dadurch gekennzeichnet, daß die Baugruppe (Q), die das elektrische Verhalten einer piezoelektrischen Zunge darstellt, eine stationär eingespannte piezoelektrische Zunge ist.
  6. Gerät nach einem der Ansprüche 3 bis 5, dadurch gekennzeichnet, daß die zweiten und vierten Brückenzweige einen Kondensator an Stelle eines Widerstands aufweisen.
EP90912526A 1989-08-22 1990-08-10 Röntgenaufnahmegerät mit schlitzblenden Expired - Lifetime EP0489060B1 (de)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
NL8902117 1989-08-22
NL8902117A NL8902117A (nl) 1989-08-22 1989-08-22 Inrichting voor spleetradiografie.
PCT/EP1990/001329 WO1991003056A1 (en) 1989-08-22 1990-08-10 Slit radiography apparatus

Publications (2)

Publication Number Publication Date
EP0489060A1 EP0489060A1 (de) 1992-06-10
EP0489060B1 true EP0489060B1 (de) 1994-11-30

Family

ID=19855200

Family Applications (1)

Application Number Title Priority Date Filing Date
EP90912526A Expired - Lifetime EP0489060B1 (de) 1989-08-22 1990-08-10 Röntgenaufnahmegerät mit schlitzblenden

Country Status (6)

Country Link
EP (1) EP0489060B1 (de)
JP (1) JPH04507362A (de)
DE (1) DE69014638T2 (de)
IL (1) IL95401A (de)
NL (1) NL8902117A (de)
WO (1) WO1991003056A1 (de)

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3275831A (en) * 1963-05-16 1966-09-27 Industrial Nucleonics Corp Radiation beam shutter collimator
US4071771A (en) * 1976-06-28 1978-01-31 Ohio-Nuclear, Inc. Shutters for X-ray scanners
NL8400845A (nl) * 1984-03-16 1985-10-16 Optische Ind De Oude Delft Nv Inrichting voor spleetradiografie.
NL8700781A (nl) * 1987-04-02 1988-11-01 Optische Ind De Oude Delft Nv Werkwijze en inrichting voor contrastharmonisatie van een roentgenbeeld.
NL8702113A (nl) * 1987-09-07 1989-04-03 Optische Ind De Oude Delft Nv Inrichting voor spleetradiografie.

Also Published As

Publication number Publication date
IL95401A (en) 1994-10-07
WO1991003056A1 (en) 1991-03-07
JPH04507362A (ja) 1992-12-24
EP0489060A1 (de) 1992-06-10
DE69014638T2 (de) 1995-05-04
IL95401A0 (en) 1991-06-30
DE69014638D1 (de) 1995-01-12
NL8902117A (nl) 1991-03-18

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