EP0063083B1 - Détecteur de rayons X - Google Patents

Détecteur de rayons X Download PDF

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Publication number
EP0063083B1
EP0063083B1 EP82400629A EP82400629A EP0063083B1 EP 0063083 B1 EP0063083 B1 EP 0063083B1 EP 82400629 A EP82400629 A EP 82400629A EP 82400629 A EP82400629 A EP 82400629A EP 0063083 B1 EP0063083 B1 EP 0063083B1
Authority
EP
European Patent Office
Prior art keywords
chamber
electrodes
rays
ionization
auxiliary
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
Application number
EP82400629A
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German (de)
English (en)
French (fr)
Other versions
EP0063083A1 (fr
Inventor
Robert Allemand
Jean-Jacques Gagelin
Edmond Tournier
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.)
Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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Commissariat a lEnergie Atomique CEA
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Publication of EP0063083A1 publication Critical patent/EP0063083A1/fr
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J47/00—Tubes for determining the presence, intensity, density or energy of radiation or particles
    • H01J47/02—Ionisation chambers

Definitions

  • the present invention relates to an X-ray detector, in particular of X-rays which have passed through an object or an organ and which are supplied by a source emitting, towards the object or the organ, a plane beam of incident X-rays. with a wide angular opening and a small thickness.
  • This invention applies more particularly to the tomography of organs, but also to industrial control, such as baggage control for example.
  • X-ray detectors make it possible to measure the absorption of an X-ray beam passing through an object or an organ, this absorption being linked to the density of the tissues of the organ examined or the density of the materials constituting the object studied. Examples of detectors of this type are described, in particular, in patent application FR-A-2 314 699.
  • ionization X-ray detectors used in tomography are of the multicell type and include cells delimited by conductive plates perpendicular to the plane of the X-ray beam and brought alternately to positive and negative potentials. These cells are located in a sealed enclosure containing an ionizable gas.
  • the advantages of this type of multicellular detector are as follows: they provide good collimation of X-rays when the plates used in the detection cells are made of a very absorbent material; the collection time of the charges resulting from the ionization of the gas by X-rays is very short because of the small spacing of the conductive plates and the good separation between the detection cells.
  • this type of detector has significant drawbacks: it is possible to reduce the thickness of the plates in order to increase the quantity of X-rays detected, but to the detriment of collimation due to the small thickness of the plates; this small thickness of the plates also causes a very large microphone.
  • detectors of this type have a great complexity of production which leads to a high manufacturing cost and they require mounting in soil. dusted, because any dust on one of the plates can cause ignition or deterioration of the leakage current between two consecutive plates. It is added to these drawbacks that the numerous plates used require very numerous electrical connections, inside the sealed chamber, which poses difficult problems of reliability of the welds of the connections on the plates.
  • This other type of detector comprises a sealed chamber containing a gas ionizable by rays from the organ or object and, in this chamber, a plate for collecting the electrons resulting from the ionization of the gas; this plate is parallel to the plane of the beam of incident rays and it is brought to a positive high voltage.
  • a series of electrodes for collecting the ions resulting from the ionization of the gas by the X-rays coming from the object is arranged in parallel and facing the preceding plate; these ion collection electrodes are brought to a potential close to zero and are directed towards the source which emits the X-rays, in the direction of the object.
  • Each ion collection electrode defines an elementary cell of the detector. These electrodes are located in a plane parallel to the plane of the beam of the incident rays and respectively provide a current which is the sum, on the one hand of a measurement current proportional to the quantity of ions obtained by the ionization of the gas in sight of each electrode, under the effect of the rays coming from the object or the organ, in a direction corresponding to that of the incident rays and, on the other hand, of a diffusion current coming from the rays diffused by l 'object or by the organ, or in general by all the obstacles encountered by the incident rays, in directions other than that of the incident rays.
  • This type of detector has certain advantages: there are no longer, as in the detector mentioned above, separation plates; this eliminates any annoying phenomenon of microphony. Due to the removal of these separation plates, the quantity of X-rays detected is maximum; the realization of this type of detector is very simple and it is very little sensitive to dust.
  • this type of detector has a serious drawback which results from the fact that the current collected on each of the electrodes brought to a potential close to zero includes a parasitic current, which falsifies the measurements; this current is a diffusion current coming from rays scattered in other directions than that of the incident rays.
  • the object of the present invention is to remedy this drawback and in particular to produce an X-ray detector which makes it possible to eliminate, in the current collected on each of the electrodes which are brought to a potential close to zero, the parasitic current resulting from the rays scattered, in particular by the object or by the organ, in other directions than that of the incident rays.
  • the subject of the invention is an X-ray detector capable of detecting, for example, rays having passed through an object or an organ and being supplied by a source emitting, towards the object or the organ, a plane beam of rays. X incidents, this beam having a wide angular opening and a small thickness, this detector comprising at least one sealed main chamber containing at least one gas ionizable by X-rays and, in this chamber, a plate for collecting the charges resulting from the ionization of the gas, this plate being parallel to the plane of the beam of incident rays and being brought to a first potential, and a series of planar electrodes for collecting the charges resulting from the ionization of the gas, these electrodes being situated opposite the charge collection plate, in a plane parallel to the plane of the beam of incident rays on the side opposite to that on which the charge collection plate is located, each of them having its largest d dimension directed towards the source, defining an elementary detection cell and supplying a current which is the sum of a measurement
  • the electrodes for collecting the charges from the main ionization chamber are carried by one of the faces of an electrically insulating plate, the plate for collecting the charges from said main ionization chamber. being brought to a second determined potential, the auxiliary ionization chamber containing the same ionizable gas as the main ionization chamber and comprising a series of charge collection electrodes carried by the other face of the electrically insulating plate, these electrodes being respectively connected to the electrodes of the main ionization chamber and being brought to the same second potential close to zero, the charge collection plate of the auxiliary ionization chamber being parallel to the electrically insulating plate, located opposite the electrodes of electron collection and brought to a third potential of sign opposite to the first potential.
  • the charge collection plate of the main chamber and the charge collection plate of the auxiliary chamber are identical, the charge collection electrodes of the main chamber being respectively identical to the charge collection electrodes of the auxiliary chamber.
  • the electrically insulating plate supporting the series of electrodes of the main and auxiliary chambers is located midway between the charge collection plate of the main chamber and the charge collection plate of the auxiliary chamber.
  • the charge collection electrodes of the main chamber are respectively located opposite the charge collection electrodes of the auxiliary chamber.
  • the first and third potentials have the same absolute value.
  • the ionizable gas is xenon.
  • the electrodes for collecting ions and electrons from the main and auxiliary chambers consist of a deposit of copper on an insulating support.
  • FIG. 1 shows schematically and in perspective, a detector of known type comprising a plate 1 brought to a positive high voltage + HT and, opposite, a series of electrodes 2 brought to a potential close to zero volts.
  • This plate and these electrodes are located in a sealed main chamber 3, shown diagrammatically and which contains at least one ionizable gas, such as xenon for example.
  • This detector makes it possible to detect the X-rays which have passed through an object or an organ 0, these rays being supplied by a point source S which emits towards the object or the organ, a plane beam F of incident X-rays; this beam has a wide angular opening and a small thickness.
  • the plate 1 is parallel to the plane of the beam of incident rays, while the plane electrodes 2 are situated in a plane parallel to the plane of the beam of incident rays, opposite the plate 1.
  • the pressure of the xenon inside the sealed chamber has a value between 10 and 20 bars; this gas can also be added to other electropositive gases intended to improve detection.
  • the electrodes 2 form converging bands in the direction of the source S.
  • Figure 2 shows schematically a front view of the previous detector.
  • This figure shows the plate 1 brought to a positive potential + HT as well as the electrodes 2 brought to a potential close to zero volts; these electrodes are supported by an electrically insulating plate 4 and each of them is connected to an amplifier 5 which makes it possible to draw the current flowing in each of the electrodes; these currents are applied to a processing (not shown) and visualization system, which makes it possible to visualize the body or the object O crossed by the X-rays emitted by the source S.
  • dotted lines vertical, the field lines and, by horizontal dotted lines, the equipotentials of the electric field created by the potential difference between the positive plate 1 and the electrodes 2 brought to a potential close to zero.
  • Xe + represents the positive xenon ions which go towards the electrodes 2 and by e- the electrons which go to the plate 1, these ions and these electrons resulting from the xenon ionization by X-rays from the object or organ O.
  • FIG. 3 shows schematically and in perspective, a detector according to the invention.
  • This detector comprises a sealed chamber 6 containing at least one ionizable gas such as xenon for example; this chamber is subdivided into two ionization chambers: a main ionization chamber 3 and an auxiliary ionization chamber 7.
  • the main ionization chamber 3 contains, like the detector of the type known in FIG.
  • the electrodes 2 converge in the direction of the source S.
  • Each of the electrodes 2 of the main ionization chamber 3 is connected to an amplifier 5 which makes it possible to take samples, for processing; the current flowing in each of these electrodes.
  • the auxiliary ionization chamber 7 located outside the X-ray beam is attached to the main chamber to compensate for the diffusion current coming from the X-rays diffused by the organ O.
  • the electrodes 2 of the main ionization chamber 3 respectively supply a current which is the sum of a part, of a measurement current proportional to the quantity of ions obtained by the ionization of the gas next to each electrode of the main ionization chamber, under the effect rays coming from the object, in directions corresponding to that of the incident rays 9, and a diffusion current resulting from the ionization of the gas by the rays scattered 8 by the object, in directions other than that incident rays.
  • the auxiliary ionization chamber 7 contains, like the main ionization chamber, a plate 10 parallel to the plane of the incident X-ray beam, which is brought to a negative high voltage - HT, as well as a series of electrodes 11 planes, parallel to the plane of the incident X-ray beam, situated on another face of the insulating plate 4 which carries the electrodes 2 of the main ionization chamber 3.
  • These electrodes 11 are worn, like the electrodes 2 of the chamber d main ionization, at a potential close to zero. They are respectively connected by connections 12, to the corresponding electrodes of the main ionization chamber 3.
  • the electrodes 11 of the auxiliary ionization chamber and the electrodes 2 of the main ionization chamber are preferably identical and located next to each other.
  • the auxiliary ionization chamber 7 makes it possible, as will be seen below in detail, to compensate, for the subsequent treatment of the currents originating from the amplifiers 5, the parasitic currents which circulate in each electrode of the main ionization chamber and which originate X-rays scattered by the object or organ 0.
  • the electrodes 11 of the auxiliary ionization chamber 7 are electrodes for collecting electrons e-, while plate 10 is a plate for collecting Xe + ions from of the xenon ionization contained in the auxiliary chamber 7, by the X-rays scattered by the object or the organ O.
  • the electrodes of the auxiliary ionization chamber are located opposite the electrodes of the chamber main ionization and positive and negative high voltages have the same absolute value.
  • FIG. 4 schematically represents a side view of the detector of the invention.
  • this view there is a point source S, the object or the organ 0, one of the rays 9 emitted by the source S and, at the output of the object 0, the direct ray 13 coming from the object 0, in the same direction as the incident ray 9; one also distinguishes in this figure one of the scattered rays 8, coming from the object 0, in a direction different from the direction of the incident ray 9.
  • one shows one of the electrodes 2 of the chamber d main ionization which is connected to an amplifier 5 and which is brought to a potential close to zero and, one of the electrodes 11 of the auxiliary ionization chamber 7, which is located opposite the electrode 2 and which is separated from this electrode by the insulating plate 4.
  • the connection 12 between the electrodes of the main and auxiliary ionization chambers has also been shown.
  • the plates 1 and 10 of the main and auxiliary ionization chambers brought respectively to positive and negative potentials + HT and - HT.
  • the sealed chamber 6 which contains the ionizable gas has not been shown in detail; the insulating plates 15, 14 support the conductive plates 1, 10 of the main and auxiliary ionization chambers.
  • the ionizable gas is for example xenon
  • This ionization is represented schematically in the figure, by Xe + ions which are attracted by the electrodes 2, and by e- electrons which are attracted by the positive plate 1.
  • An ionization thus occurs opposite each of the electrodes of the main ionization chamber using X-rays from the object, in the direction of the incident rays.
  • These ion movements produce respectively in each electrode, a current 1 which is the sum of a current I M , resulting from the ionization of the gas opposite each of the electrodes, under the effect of X-rays from the object (rays represented at 13 in the figure), in a direction corresponding to that of the incident rays, and of a so-called diffusion current I D , which results from the ionization of the gas, opposite each of the electrodes from the rays scattered by the object (represented at 8 in the figure) or by all the material obstacles encountered by the incident X-rays, in directions which do not correspond to those of the incident X-rays.
  • the ionization chamber 7 makes it possible to compensate for this "diffusion current", thanks to the ionization produced in this chamber by the scattered X-rays 8; this ionization causes the circulation, in the electrodes 11 of the auxiliary chamber, of a current 1 D which is cut off, thanks to the connection 12, from the “parasitic diffusion current taken into account by the electrodes of the ionization chamber main.
  • the study demonstrated that the current collected in the auxiliary ionization chamber was representative of the diffusion current collected in the main ionization chamber.
  • the amplifiers 5 connected to each of the electrodes of the main and auxiliary ionization chambers receive a current l m which is effectively the measurement current corresponding to the ionization of the gas, caused opposite each of the electrodes of the chamber d main ionization by the rays 13 coming from the object or the organ in the directions which correspond to those of the incident rays 9.
  • the plates and electrodes of the main and auxiliary ionization chambers are preferably produced in the form of a copper deposit on an insulating support.
  • the number of cells in each chamber can be greater than 500, for an opening angle of the X-ray beam greater than 40 °; in this case, the pitch between each of the electrodes of each chamber is approximately 1 mm.
  • the insulating plate 4 which supports the electrodes of the main and auxiliary chambers is located halfway between these plates 1 and 10, respectively brought to the positive and negative potential. The distance between these plates 1 and 10 is approximately 14 mm and the ion collection time is close to 10 ms.

Landscapes

  • Measurement Of Radiation (AREA)
  • Electron Tubes For Measurement (AREA)
  • Apparatus For Radiation Diagnosis (AREA)
  • Analysing Materials By The Use Of Radiation (AREA)
EP82400629A 1981-04-15 1982-04-06 Détecteur de rayons X Expired EP0063083B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8107568A FR2504278B1 (fr) 1981-04-15 1981-04-15 Detecteur de rayons x
FR8107568 1981-04-15

Publications (2)

Publication Number Publication Date
EP0063083A1 EP0063083A1 (fr) 1982-10-20
EP0063083B1 true EP0063083B1 (fr) 1985-08-28

Family

ID=9257430

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Application Number Title Priority Date Filing Date
EP82400629A Expired EP0063083B1 (fr) 1981-04-15 1982-04-06 Détecteur de rayons X

Country Status (5)

Country Link
US (1) US4469947A (enrdf_load_stackoverflow)
EP (1) EP0063083B1 (enrdf_load_stackoverflow)
JP (1) JPS57179776A (enrdf_load_stackoverflow)
DE (1) DE3265745D1 (enrdf_load_stackoverflow)
FR (1) FR2504278B1 (enrdf_load_stackoverflow)

Families Citing this family (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2570908B1 (fr) * 1984-09-24 1986-11-14 Commissariat Energie Atomique Systeme de traitement des signaux electriques issus d'un detecteur de rayons x
FR2629215B1 (fr) * 1988-03-23 1990-11-16 Commissariat Energie Atomique Ensemble de detection pour tomographie a rayonnements ionisants
DE3901837A1 (de) * 1989-01-23 1990-07-26 H J Dr Besch Bildgebender strahlendetektor mit pulsintegration
US5072123A (en) * 1990-05-03 1991-12-10 Varian Associates, Inc. Method of measuring total ionization current in a segmented ionization chamber
SE513161C2 (sv) * 1997-11-03 2000-07-17 Digiray Ab En metod och en anordning för radiografi med plant strålknippe och en strålningsdetektor
SE514443C2 (sv) * 1999-04-14 2001-02-26 Xcounter Ab Strålningsdetektor och en anordning för användning vid radiografi med plant strålknippe
SE514475C2 (sv) * 1999-04-14 2001-02-26 Xcounter Ab Strålningsdetektor, en anordning för användning vid radiografi med plant strålknippe och ett förfarande för detektering av joniserande strålning
SE514460C2 (sv) * 1999-04-14 2001-02-26 Xcounter Ab Förfarande för detektering av joniserande strålning, strålningsdetektor och anordning för användning vid radiografi med plant strålknippe
SE514472C2 (sv) * 1999-04-14 2001-02-26 Xcounter Ab Strålningsdetektor och en anordning för användning vid radiografi
SE0000793L (sv) * 2000-03-07 2001-09-08 Xcounter Ab Tomografianordning och -förfarande
US20130100135A1 (en) * 2010-07-01 2013-04-25 Thomson Licensing Method of estimating diffusion of light

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2314699A1 (fr) * 1975-06-19 1977-01-14 Commissariat Energie Atomique Dispositif d'analyse pour tomographie a rayons x par transmission

Family Cites Families (9)

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Publication number Priority date Publication date Assignee Title
US3812362A (en) * 1973-07-02 1974-05-21 Honeywell Inc Smoke detector circuit
FR2249517B1 (enrdf_load_stackoverflow) * 1973-10-30 1976-10-01 Thomson Csf
US4031396A (en) * 1975-02-28 1977-06-21 General Electric Company X-ray detector
US4047041A (en) * 1976-04-19 1977-09-06 General Electric Company X-ray detector array
DE2642846A1 (de) * 1976-09-23 1978-03-30 Siemens Ag Roentgenschichtgeraet zur herstellung von transversalschichtbildern
DE2707409C2 (de) * 1977-02-21 1985-02-21 Hartwig Dipl.-Ing. 2409 Scharbeutz Beyersdorf Ionisationsbrandmelder
JPS54131881U (enrdf_load_stackoverflow) * 1978-03-06 1979-09-12
GB1598962A (en) * 1978-03-21 1981-09-30 Siemens Ag Arrangement for detecting radiation
FR2469797A1 (fr) * 1979-11-14 1981-05-22 Radiologie Cie Gle Detecteur a ionisation gazeuse et tomodensitometre utilisant un tel detecteur

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2314699A1 (fr) * 1975-06-19 1977-01-14 Commissariat Energie Atomique Dispositif d'analyse pour tomographie a rayons x par transmission

Also Published As

Publication number Publication date
FR2504278A1 (fr) 1982-10-22
JPH0335634B2 (enrdf_load_stackoverflow) 1991-05-28
DE3265745D1 (en) 1985-10-03
EP0063083A1 (fr) 1982-10-20
US4469947A (en) 1984-09-04
FR2504278B1 (fr) 1985-11-08
JPS57179776A (en) 1982-11-05

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