EP0456322B1 - Installation de production de radiographies - Google Patents

Installation de production de radiographies Download PDF

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Publication number
EP0456322B1
EP0456322B1 EP91201075A EP91201075A EP0456322B1 EP 0456322 B1 EP0456322 B1 EP 0456322B1 EP 91201075 A EP91201075 A EP 91201075A EP 91201075 A EP91201075 A EP 91201075A EP 0456322 B1 EP0456322 B1 EP 0456322B1
Authority
EP
European Patent Office
Prior art keywords
image
photoconductor
ray
carrier
axis
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
EP91201075A
Other languages
German (de)
English (en)
Other versions
EP0456322A2 (fr
EP0456322A3 (fr
Inventor
Ingo Dr. Schäfer
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
Koninklijke Philips Electronics NV
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, Koninklijke Philips Electronics NV, Philips Electronics NV filed Critical Philips Patentverwaltung GmbH
Publication of EP0456322A2 publication Critical patent/EP0456322A2/fr
Publication of EP0456322A3 publication Critical patent/EP0456322A3/fr
Application granted granted Critical
Publication of EP0456322B1 publication Critical patent/EP0456322B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/054—Apparatus for electrographic processes using a charge pattern using X-rays, e.g. electroradiography

Definitions

  • the invention relates to an arrangement for generating x-ray images with an x-ray emitter for generating an x-ray beam, a photoconductor for converting x-radiation into a charge pattern, which is applied to a carrier that is rotationally symmetrical with respect to an axis of rotation, a drive unit for driving the carrier about the axis of rotation, and a Readout unit, which converts the charge pattern on the surface of the rotating photoconductor into electrical image values after an X-ray exposure.
  • the charge pattern generated in this way is read out immediately after the X-ray exposure.
  • the carrier rotates at a much higher speed than during the X-ray exposure, and the readout device reads the charge with one or more probes on a practically circular track on the surface of the photoconductor out.
  • the reading unit is moved parallel to the axis of rotation at a comparatively low average speed.
  • the reading can take place much faster, more precisely and more precisely than is possible with a flat photoconductor plate, as is known from US Pat. No. 4,134,137.
  • the fast readout is absolutely necessary because the photoconductor is not only discharged by the X-ray exposure, but also by dark currents. This is offset by the disadvantage that the total exposure time is comparatively long and that the power of the X-ray tube is poorly used because only a thin fan of rays is used to expose the photoconductor.
  • this object is achieved according to the invention in that the drive unit is controlled in such a way that the photoconductor does not rotate during an X-ray exposure.
  • the carrier rotates both during the X-ray exposure and during the readout process, this is only the case with the invention during the readout.
  • the support with the photoconductor does not rotate, and therefore the area of the photoconductor intended for the X-ray exposure can be exposed in all areas at the same time, so that there is a short total exposure time and good utilization of the performance of the X-ray tube.
  • the diameter of the carrier may be substantially larger than in an arrangement of the type mentioned. While in the latter only the circumference of the carrier must be larger than the recording format, the diameter of the Carrier can be larger than the recording format.
  • EP-A-94 843 in particular FIG. 8, already discloses an arrangement for generating X-ray images in which a storage phosphor is applied to a cylindrical support which is stationary during an X-ray image. Such storage phosphors lose their image information much more slowly than photoconductors, so that fast reading is not necessary.
  • the carrier is rotated once around the axis of rotation in three steps, the X-ray exposure being read out with a two-dimensionally guided laser beam in the first step and the storage phosphor being erased in the next step. An additional recording can be made at each step.
  • the carrier stands both during the X-ray exposure and during the readout process; reading out cannot be faster than with a flat record carrier.
  • a preferred further development provides that means for geometrical image transformation are provided which compensate for the image distortions caused by the curvature of the surface of the photoconductor. This avoids distortions that are unavoidable due to the curvature of the rotationally symmetrical, preferably cylindrical, carrier, unless the recording format is small in comparison to the drum diameter.
  • the pixels on the drum surface Assigned to virtual pixels in an image plane located in the X-ray beam in such a way that the connecting straight lines intersect through assigned pixels in the starting point of the X-ray beam.
  • the image plane can be tangential to the surface of the photoconductor and perpendicular to the plane defined by the focus of the x-ray emitter for generating the x-ray beam and the axis of rotation. However, a different position within the X-ray beam is also possible.
  • the drive unit of the carrier is controlled in such a way that, prior to reading out an X-ray image, the carrier is rotated to such an extent that an area of the photoconductor which was not exposed during the previous X-ray image enters the beam path.
  • This makes it possible to take two pictures - in smaller formats even more than two - in close succession without having to read out the photoconductor in between.
  • this embodiment assumes that the image memory has enough capacity to store two or more X-ray images at the same time.
  • the X-ray beam 10 emanating from the focus of an X-ray emitter 1 passes through a patient 2 lying on a table top 3 and an anti-scatter grid 8 before it hits a cylindrical carrier (drum) 4, the cylinder axis 7 of which is perpendicular to the plane of FIG. 1 is simultaneously its axis of rotation .
  • the carrier 4 can be driven about the axis of rotation 7 by means of a motor drive 9.
  • the carrier 4 is coated on its lateral surfaces with a photoconductor, preferably a 0.5 mm thick selenium layer 41.
  • a charging device 6 which charges the rotating carrier before an X-ray exposure, so that a voltage of, for example, between the surface of the electrically conductive carrier and the outer surface of the selenium layer 1,500 volts is present.
  • a readout device 5 which reads out the charge density on one or more tracks after an X-ray exposure with one or more probes.
  • the reading device 5 is displaced relative to the carrier 4 by means of a further drive unit 11 parallel to the axis of rotation 7 at an average speed which is low in comparison to the peripheral speed of the carrier.
  • the structure and function of the readout device 5 and the charging unit 6 are described in more detail in DE-A-35 34 768, to which express reference is made.
  • the drive 9 for the carrier 4 is switched off, so that the photoconductor does not rotate. Therefore, the outer radius r of the photoconductor layer 41 on the carrier 4 must be large enough so that the part of the patient 2 to be photographed can be completely imaged on the surface of the photoconductor 41.
  • B 2 r * (1 + 2r / L) -1/2 L is the distance of focus 1 from the image plane.
  • the recording format should be smaller than this limit and preferably 0.95 B - or less.
  • a radius r of at least 23.7 cm is required.
  • FIG. 2a shows the carrier 4 in a perspective representation
  • FIG. 2b shows it in the same representation as FIG. 1, ie with the axis of rotation 7 perpendicular to the plane of the drawing.
  • the coordinates on the surface of the photoconductor are denoted by x, y, the y axis being identical to the apex line already mentioned, in which the image plane 12 touches the photoconductor.
  • the x coordinate of a point is the length of the arc, that connects this point on the surface of the photoconductor to the y-axis.
  • the coordinates of the assigned image point in the image plane are denoted by x v and y v .
  • the origin of the x v , y v coordinate system is identical to the origin of the xy coordinate system and the y v axis coincides with the y axis.
  • the auxiliary variable z denotes the distance of a pixel from the image plane 12.
  • a pixel x v , y v in the image plane 12 can be assigned to each pixel x, y on the surface of the photoconductor hit by X-radiation.
  • equations 3 and 4 must weight x v and y v with a constant factor.
  • the image plane can also run at an angle different from 90 ° to the plane formed by the axis of rotation 7 and the focus 1.
  • the transformation equations then become more complicated.
  • Such an oblique image plane can arise, for example, in the case of oblique images in which the patient 2 or the tabletop 3 is irradiated obliquely and in which an X-ray image is nevertheless made in a plane 3 relative to the tabletop parallel plane should take place.
  • it can also be expedient to have the image plane perpendicular to the plane (inclined in the case of an inclined image), which is defined by the axis of rotation 7 and the focus 1. In this case, the image plane would run obliquely to the table top 3 and one could avoid the distortions that occur with conventional oblique photographs.
  • the pixels in both the image generated on the photo surface and in the image derived therefrom each have the same dimensions, e.g. 0.2 mm x 0.2 mm, then it follows from the geometric relationships that the image value of a pixel at the edge of the image plane 12 is wholly or partly composed of the image values of several pixels on the surface of the photoconductor.
  • the weighted sum of the image values mentioned must therefore be formed, the weighting factors being between 0 and 1.
  • the X-rays are not completely absorbed within the photoconductor layer (eg 0.5 mm selenium).
  • the photoconductor layer eg 0.5 mm selenium.
  • an X-ray beam striking obliquely (at the edge) changes the charge density more than an X-ray beam striking perpendicularly (in the middle).
  • a homogeneous object would therefore lead to an X-ray exposure exposed to different locations.
  • This can be compensated for by multiplying the image values I (x, y) assigned to the individual pixels on the surface of the photoconductor - preferably in connection with the equalization transformation - by a correction factor k so that the relationship applies dI v (x v , y v ) k * I (x, y) dI v is the contribution of the image value I (x, y) to the image value I v for the pixel x v , y v in the image plane.
  • k is the correction factor, which decreases with increasing amount of x and which takes into account the weighting mentioned.
  • the change in the factor k as a function of x is more pronounced the harder the x-ray radiation, ie the greater the voltage on the x-ray tube during the exposure. With very soft radiation, this dependency practically disappears.
  • FIG. 3 schematically shows the processing of the values supplied by the read-out unit 5. They are first fed to an analog-digital converter 20 and stored in a memory 22 by an image processing unit 21.
  • the image processing unit 21 calculates the image values I v (x v , y v ) of the image transformed into the image plane from the image values contained in the memory 22 according to equations 2 to 5 and stores them in a further image memory 23 corrected image can be displayed on a monitor 24.

Landscapes

  • Health & Medical Sciences (AREA)
  • Pathology (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Apparatus For Radiation Diagnosis (AREA)
  • Radiography Using Non-Light Waves (AREA)
  • Transforming Light Signals Into Electric Signals (AREA)
  • Analysing Materials By The Use Of Radiation (AREA)

Claims (5)

  1. Dispositif pour la production de radiographies comportant un générateur de rayons X (1) pour produire un faisceau de rayons X, un photoconducteur (41) pour convertir des rayons X en un motif de charge qui est monté sur un support (4) présentant une symétrie de rotation par rapport à un axe de rotation (7), une unité d'entraînement (9) pour entraîner le support autour de l'axe de rotation et une unité de lecture (5) qui, après une prise de vue radiographique, convertit le motif de charge présent à la surface du photoconducteur tournant en des valeurs d'image électriques, caractérisé en ce que l'unité d'entraînement est commandée d'une manière telle que le photoconducteur (41) ne tourne pas pendant une prise de vue radiographique.
  2. Dispositif suivant la revendication 1, caractérisé en ce que sont prévus des moyens (21) pour la transformation d'images géométriques, qui compensent les déformations d'images provoquées par la courbure (r) de la surface du photoconducteur (41).
  3. Dispositif suivant l'une quelconque des revendications précédentes, caractérisé en ce que l'unité d'entraînement (9) du support (4) est commandée d'une manière telle qu'avant la lecture d'un enregistrement radiographique, le support soit tourné au point qu'un domaine non encore exposé lors de l'enregistrement radiographique précédent du photoconducteur parvienne dans le trajet des rayons.
  4. Dispositif suivant l'une quelconque des revendications précédentes, caractérisé en ce que sont prévus des moyens (21) pour la multiplication des valeurs d'image par un facteur de correction (k) qui est plus grand pour des valeurs d'image situées au bord de l'image que pour des valeurs d'image situées au milieu de l'image.
  5. Dispositif suivant l'une quelconque des revendications précédentes, caractérisé en ce qu'une autre unité d'entraînement (11) est prévue pour déplacer l'unité de lecture (5) dans un plan contenant l'axe de rotation (7), le long de la surface du photoconducteur (41).
EP91201075A 1990-05-11 1991-05-06 Installation de production de radiographies Expired - Lifetime EP0456322B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE4015113A DE4015113A1 (de) 1990-05-11 1990-05-11 Anordnung zum erzeugen von roentgenaufnahmen
DE4015113 1990-05-11

Publications (3)

Publication Number Publication Date
EP0456322A2 EP0456322A2 (fr) 1991-11-13
EP0456322A3 EP0456322A3 (fr) 1992-12-30
EP0456322B1 true EP0456322B1 (fr) 1995-08-09

Family

ID=6406170

Family Applications (1)

Application Number Title Priority Date Filing Date
EP91201075A Expired - Lifetime EP0456322B1 (fr) 1990-05-11 1991-05-06 Installation de production de radiographies

Country Status (6)

Country Link
US (1) US5093851A (fr)
EP (1) EP0456322B1 (fr)
JP (1) JPH0690937A (fr)
DE (2) DE4015113A1 (fr)
ES (1) ES2078427T3 (fr)
FI (1) FI912222A7 (fr)

Families Citing this family (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4118153A1 (de) * 1991-06-03 1992-12-10 Philips Patentverwaltung Anordnung zum erzeugen von roentgenaufnahmen
DE4129469A1 (de) * 1991-09-05 1993-03-11 Philips Patentverwaltung Photoleiteranordnung mit einer ausleseeinheit
DE4330366A1 (de) * 1993-09-08 1995-03-09 Philips Patentverwaltung Verfahren zum Erzeugen von Röntgenaufnahmen und Anordnung zur Durchführung des Verfahrens
DE4333325A1 (de) * 1993-09-30 1995-04-06 Philips Patentverwaltung Röntgenaufnahmegerät mit einem Photoleiter und mit einer Korona-Aufladeeinrichtung
DE4428779A1 (de) * 1994-08-13 1996-02-15 Philips Patentverwaltung Anordnung zur Erzeugung von Röntgenaufnahmen
JPH09509621A (ja) * 1994-11-24 1997-09-30 フィリップス エレクトロニクス ネムローゼ フェンノートシャップ ドラム形状加工物を機械加工する方法、このような方法により製造されたドラム形状担体が設けられるｘ線診断装置及び写真複写機
DE19511286A1 (de) * 1995-03-28 1996-10-02 Philips Patentverwaltung Röntgenaufnahmegerät mit einem Photoleiter und einer Aufladeeinrichtung
IL123006A (en) 1998-01-20 2005-12-18 Edge Medical Devices Ltd X-ray imaging system
IL126018A0 (en) 1998-09-01 1999-05-09 Edge Medical Devices Ltd X-ray imaging system
US6326625B1 (en) 1999-01-20 2001-12-04 Edge Medical Devices Ltd. X-ray imaging system
US6178225B1 (en) 1999-06-04 2001-01-23 Edge Medical Devices Ltd. System and method for management of X-ray imaging facilities

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4019052A (en) * 1975-10-30 1977-04-19 U.S. Philips Corporation Electrophotographic x-ray device
US4134137A (en) * 1976-11-01 1979-01-09 Xerox Corporation Single wire microelectrometer imaging system
JPH0685045B2 (ja) * 1982-05-19 1994-10-26 富士写真フイルム株式会社 放射線画像情報変換方法および装置
DE3534768A1 (de) * 1985-09-30 1987-04-02 Philips Patentverwaltung Anordnung zum erzeugen von roentgenaufnahmen mittels eines fotoleiters
DE3842525A1 (de) * 1988-12-17 1990-06-21 Philips Patentverwaltung Verfahren zur erzeugung einer roentgenaufnahme mittels eines photoleiters und anordnung zur durchfuehrung des verfahrens

Also Published As

Publication number Publication date
EP0456322A2 (fr) 1991-11-13
EP0456322A3 (fr) 1992-12-30
FI912222A0 (fi) 1991-05-08
DE59106180D1 (de) 1995-09-14
FI912222L (fi) 1991-11-12
DE4015113A1 (de) 1991-11-14
JPH0690937A (ja) 1994-04-05
FI912222A7 (fi) 1991-11-12
US5093851A (en) 1992-03-03
ES2078427T3 (es) 1995-12-16

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