EP0021442A1 - Accélérateur d'électrons - Google Patents

Accélérateur d'électrons Download PDF

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Publication number
EP0021442A1
EP0021442A1 EP80103662A EP80103662A EP0021442A1 EP 0021442 A1 EP0021442 A1 EP 0021442A1 EP 80103662 A EP80103662 A EP 80103662A EP 80103662 A EP80103662 A EP 80103662A EP 0021442 A1 EP0021442 A1 EP 0021442A1
Authority
EP
European Patent Office
Prior art keywords
target
collimator
electron
section
processes
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
EP80103662A
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German (de)
English (en)
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EP0021442B1 (fr
Inventor
Leonhard Dipl.-Phys. Taumann
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
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Siemens AG
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Filing date
Publication date
Application filed by Siemens AG filed Critical Siemens AG
Publication of EP0021442A1 publication Critical patent/EP0021442A1/fr
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Publication of EP0021442B1 publication Critical patent/EP0021442B1/fr
Expired legal-status Critical Current

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    • 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

Definitions

  • the invention relates to an electron accelerator with a target exposed to the electron beam emerging from the acceleration tube, with an electron absorber downstream of the target in the beam direction, with a collimator for masking an X-ray cone and with a compensating body centered for the masking aperture of the collimator.
  • the invention has for its object to limit the radiation exposure of the patient as a whole to what is therapeutically necessary and in particular to reduce the radiation exposure to neutrons.
  • the edge zone of the collimator facing the target is therefore made of a material with a small cross section for ( ⁇ , n) processes in order to reduce neutron generation.
  • This solution is based on the surprising finding that the neutrons are only generated to a very small extent in the parts built into the useful beam cone, ie the target, the electron absorber or the compensating body. The majority of the neutrons are generated on the side of the collimator facing the radiation source. The neutrons generated there penetrate the collimator and lead to the observed diffuse radiation of the surroundings.
  • the edge zone made of material with a small cross section for ( ⁇ , n) processes can have an extent radially to the target that corresponds approximately to the half-depth of the X-rays in this material.
  • This relation gives a good guide for the optimization of the collimator. Because in the deeper layers of the collimator, i.e. after passing through the half-depth for the X-rays, only a comparatively low X-ray quantum density and therefore a lower generation rate for the neutrons can be expected both because of the absorption of the X-rays and because of the quadratic distance law. Those parts can therefore be made without too large Influence on neutron production from a heavy metal, such as tungsten or lead, which shields the X-ray quanta well.
  • a further optimization of the collimator can be achieved in that the edge zone made of material with a small cross section for ( ⁇ , n) processes extends transversely to the direction of the axis of symmetry of the blanking opening up to a distance from the target that is approximately 1.5 times the Distance between the target and the edge of the collimator blanking opening closest to the target is.
  • the zones of the primary collimator that are further away from the target are anyway exposed to a lower X-ray quantum density due to the quadratic distance law, so that less in this area too Neutrons are generated by ( ⁇ , n) processes. Lining them with a material with a smaller cross section for (yv, n) processes would therefore not result in such a great reduction in neutron production that a deterioration in X-ray absorption should be accepted.
  • the figure shows a schematic representation of an electron accelerator with a target for generating X-ray brake radiation and with a collimator according to the invention for masking an X-ray cone.
  • the end of the acceleration tube 3 of an electron accelerator which is cut open in the plane of the axis of symmetry 1 of the last cavity resonator 2, can be seen.
  • the target 6 is mounted in a bore 7 of a carrier plate 8.
  • a first electron absorber 9 in the bore 7 of the carrier plate 8. It consists of a 20 mm thick copper disc.
  • a collimator 10 for the X-rays is arranged behind this electron absorber in the beam direction.
  • the collimator 10 is provided with a conical blanking opening 11 for the passage of the maximum useful beam cone 12.
  • the front section of this conical blanking opening 11 facing the target is drilled out cylindrically for receiving a further electron absorber 13 made of aluminum.
  • a compensating body 14 is attached to the collimator 10, protruding into its conical blanking opening 11:
  • the edge zone of the conical blanking opening 11 of the collimator 10 facing the target 6 is cylindrical.
  • the volume element removed is with an annular body 15 which is adapted in terms of its external dimensions and is made of a material with a small cross section for (C, n) processes replaced.
  • the strength of this ring-shaped body is expediently chosen to be approximately as large in the beam direction as the half-value depth for X-ray quanta in this material.
  • the extension of this annular body 15 transversely to the axis of symmetry 1 of the conical blanking opening 11 of the collimator 10 extends up to a distance from the target 6 that is 1.5 times the distance of the target 6 from the edge portion of the blanking opening 11 closest to it Collimator 10 including the annular body 15.
  • the accelerated electrons which have penetrated the window 5 of the acceleration tube 3 strike the target 6 and generate X-ray brake radiation there.
  • the x-ray quanta generated in this way also generate neutrons in the target 6 on the basis of ( ⁇ , n) processes. This cannot be avoided because those elements of a higher atomic number which have a good efficiency in the generation of X-ray quanta also have a low energy threshold and at the same time a relatively high cross section for ( ⁇ , n) processes. Nevertheless, the total number of neutrons generated in the target 6 is negligible because of the relatively small volume of the target, in the present case an approximately 0.3 mm thick lead foil.
  • the other elements in the useful beam cone 12, such as electron absorbers 9, 13 and compensating bodies 14, are made of copper, iron or aluminum and therefore already have a significantly lower cross section for ( ⁇ , n) processes. They therefore hardly contribute to the generation of neutrons.
  • the situation is different with the collimator 10 delimiting the x-ray cone. Because of the required high absorption coefficient for X-rays, it consists of a material with a high atomic number, preferably tungsten, tantalum or lead. Its radiated volume is also relatively large. In general, 80% of all neutrons generated in such systems are generated in it. In particular, the areas of the collimator in which the x-ray dose rate is particularly high contribute to neutron generation. These are, in particular, the areas of the collimator 10 closest to the target 6. The production rate of neutrons decreases in direct proportion to the X-ray quantum density in the material of the collimator.
  • the neutron production is reduced relatively strongly with minimal material exchange.
  • the density of the X-ray quanta has dropped so far behind this annular body 15 in the beam direction that a replacement of this area with a material with a small cross section does not seem to make much sense for ( ⁇ , n) processes. Because an additional slight reduction in neutron production would be bought by a more significant reduction in the shielding of the X-rays.
  • the wall thickness of the collimator would have to be increased.
  • the lateral extent of the annular body transverse to the axis of symmetry of the conical blanking opening 11 of the collimator 10 is to be limited to a distance from the target which corresponds approximately to 1.5 times the distance of the target from the closest edge section of the blanking opening of the collimator.
  • Carbon, aluminum, beryllium, calcium, iron and possibly copper are to be mentioned as materials with a small cross section for ( ⁇ , n) processes. While carbon and aluminum have particularly smaller cross sections for ( ⁇ , n) processes, a smaller range of X-ray quanta can be expected for iron and copper, which has the disadvantage of a somewhat larger cross section for ( ⁇ , n) processes, based on the dimension of the selected shield, again compensate something.

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  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Particle Accelerators (AREA)
  • Radiation-Therapy Devices (AREA)
EP80103662A 1979-07-03 1980-06-27 Accélérateur d'électrons Expired EP0021442B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE2926841 1979-07-03
DE2926841A DE2926841A1 (de) 1979-07-03 1979-07-03 Elektronenbeschleuniger

Publications (2)

Publication Number Publication Date
EP0021442A1 true EP0021442A1 (fr) 1981-01-07
EP0021442B1 EP0021442B1 (fr) 1982-12-29

Family

ID=6074813

Family Applications (1)

Application Number Title Priority Date Filing Date
EP80103662A Expired EP0021442B1 (fr) 1979-07-03 1980-06-27 Accélérateur d'électrons

Country Status (5)

Country Link
US (1) US4327293A (fr)
EP (1) EP0021442B1 (fr)
JP (1) JPS5614198A (fr)
CA (1) CA1145863A (fr)
DE (2) DE2926841A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2630515A1 (fr) * 1988-04-21 1989-10-27 Hutchinson Courroie doublement striee et son procede de fabrication
WO2016023950A1 (fr) * 2014-08-13 2016-02-18 Nikon Metrology Nv Collimateur de faisceau de rayons x

Families Citing this family (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4827491A (en) * 1986-10-30 1989-05-02 New York University Radiosurgical collimator knife
US5033074A (en) * 1989-12-04 1991-07-16 Gte Laboratories Incorporated X-ray colllimator for eliminating the secondary radiation and shadow anomaly from microfocus projection radiographs
GB2367993B (en) * 2000-10-11 2005-04-20 Elekta Ab Radiotherapy apparatus
US8306184B2 (en) * 2005-05-31 2012-11-06 The University Of North Carolina At Chapel Hill X-ray pixel beam array systems and methods for electronically shaping radiation fields and modulation radiation field intensity patterns for radiotherapy
CN101340771B (zh) * 2007-06-21 2011-03-30 清华大学 一种光中子转换靶
DE102008030590A1 (de) 2007-06-29 2009-01-08 Carl Zeiss Surgical Gmbh Applikator zur Verwendung in einer Strahlentherapievorrichtung sowie Strahlentherapievorrichtung
US7692154B1 (en) 2008-11-17 2010-04-06 The United States Of America As Represented By The Secretary Of The Army Lightweight quartic-shaped collimator for collecting high energy gamma rays
DE102009058581A1 (de) * 2009-12-17 2011-06-22 Carl Zeiss Surgical GmbH, 73447 Applikatoreinrichtung für die Strahlentherapie, Befestigungseinrichtung sowie Strahlentherapievorrichtung
EP3389055A1 (fr) * 2017-04-11 2018-10-17 Siemens Healthcare GmbH Équipement à rayons x destiné à la production de rayons x à haute énergie

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2406889A1 (fr) * 1977-10-21 1979-05-18 Siemens Ag Accelerateur d'electrons

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4121109A (en) * 1977-04-13 1978-10-17 Applied Radiation Corporation Electron accelerator with a target exposed to the electron beam

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2406889A1 (fr) * 1977-10-21 1979-05-18 Siemens Ag Accelerateur d'electrons

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2630515A1 (fr) * 1988-04-21 1989-10-27 Hutchinson Courroie doublement striee et son procede de fabrication
WO2016023950A1 (fr) * 2014-08-13 2016-02-18 Nikon Metrology Nv Collimateur de faisceau de rayons x
US10283228B2 (en) 2014-08-13 2019-05-07 Nikon Metrology Nv X-ray beam collimator

Also Published As

Publication number Publication date
DE2926841A1 (de) 1981-01-22
JPS6327679B2 (fr) 1988-06-03
DE3061500D1 (en) 1983-02-03
US4327293A (en) 1982-04-27
JPS5614198A (en) 1981-02-10
EP0021442B1 (fr) 1982-12-29
CA1145863A (fr) 1983-05-03

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