EP0021442B1 - Elektronenbeschleuniger - Google Patents

Elektronenbeschleuniger Download PDF

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Publication number
EP0021442B1
EP0021442B1 EP80103662A EP80103662A EP0021442B1 EP 0021442 B1 EP0021442 B1 EP 0021442B1 EP 80103662 A EP80103662 A EP 80103662A EP 80103662 A EP80103662 A EP 80103662A EP 0021442 B1 EP0021442 B1 EP 0021442B1
Authority
EP
European Patent Office
Prior art keywords
target
collimator
electron accelerator
electron
section
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
EP80103662A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0021442A1 (de
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
Original Assignee
Siemens AG
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 Siemens AG filed Critical Siemens AG
Publication of EP0021442A1 publication Critical patent/EP0021442A1/de
Application granted granted Critical
Publication of EP0021442B1 publication Critical patent/EP0021442B1/de
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.
  • US-A-4121109 discloses an electron accelerator intended for use in radiation therapy.
  • a target is exposed to the electron beam emerging from the acceleration tube in this electron accelerator.
  • an electron absorber in which the remaining electrons are filtered out of the X-rays and a collimator with a passage opening for the suppression of the maximum, usually conical, X-ray field that is used.
  • a compensation body is installed in the passage opening of the collimator, by means of which the dose rate of the emerging X-radiation is compensated for over its entire cross-section.
  • neutrons are also generated which increase the patient's radiation exposure in a highly undesirable manner.
  • the object of the invention is 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 provided with a recess which is symmetrical to the axis of the collimator's blanking opening and which, in order to reduce neutron generation, has an element which fills the recess and is made of a material with a small cross section for (y, n) processes.
  • This solution is based on the surprising finding that only a very small part of the neutrons in the parts built into the useful beam cone, i. H. 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 element can have an extent radially to the target that corresponds approximately to the half-value 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. H. after passing through the half-value 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 much influence on the neutron production from a heavy metal which shields the X-ray quanta well, such as, for. B. tungsten or lead.
  • a further optimization of the collimator can be achieved in that the element extends transversely to the direction of the axis of symmetry of the blanking opening to a distance from the target which is approximately 1.5 times the distance between the target and the edge of the blanking opening of the collimator closest to the target .
  • the zones further away from the target of the primary collimator are subjected to a lower x-ray quantum density anyway because of the quadratic distance law, so that fewer neutrons are generated by (y, n) processes in this area as well. Lining them with a material with a smaller cross section for (y, 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.
  • a lead foil is arranged as a target 6 in the beam direction behind the window 5.
  • 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 an approximately 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 cylindrically to accommodate a further electron absorber 13 made of aluminum.
  • a compensating body 14 is attached to the collimator 10, projecting 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 removed volume element is replaced by an annular body 15 which is adapted in terms of its outer dimensions and is made of a material with a small effective cross section for (y, n) processes.
  • 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 as large as the distance of the target 6 from the edge section of the blanking opening 11 of the collimator nearest to it 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 (y, n) processes. This cannot be avoided because those elements of a higher atomic number that 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 (y, n) processes. Nevertheless, the total number of neutrons generated in the target 6 is negligible due to the relatively small volume of the target, in the present case an approximately 0.3 mm thick lead foil.
  • the other elements located in the useful beam cone 12, such as electron absorber 9, 13 and compensating body 14, are made of copper, iron or aluminum and therefore already have a significantly lower cross section for (y, 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 (y, n) processes. Because an additional slight reduction in - neutron production would be bought through a more significant reduction in the shielding of the X-rays.
  • Carbon, aluminum, beryllium, calcium, iron and at most copper are to be mentioned as materials with a small cross section for (y, n) processes. While carbon and aluminum have particularly smaller cross sections for (y, n) processes, a smaller range of X-ray quanta is to be expected for iron and copper, which has the disadvantage of a somewhat larger cross section for (y, n) processes 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 Elektronenbeschleuniger Expired EP0021442B1 (de)

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 EP0021442A1 (de) 1981-01-07
EP0021442B1 true EP0021442B1 (de) 1982-12-29

Family

ID=6074813

Family Applications (1)

Application Number Title Priority Date Filing Date
EP80103662A Expired EP0021442B1 (de) 1979-07-03 1980-06-27 Elektronenbeschleuniger

Country Status (5)

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

Families Citing this family (11)

* 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
FR2630515B1 (fr) * 1988-04-21 1991-09-27 Hutchinson Courroie doublement striee et son procede de fabrication
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
US8374310B2 (en) * 2007-06-21 2013-02-12 Tsinghua University Method and system for contraband detection using photoneutrons and X-rays
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
GB201414393D0 (en) 2014-08-13 2014-09-24 Nikon Metrology Nv Z-ray beam collimator
EP3389055B1 (de) * 2017-04-11 2025-09-24 Siemens Healthineers AG Röntgeneinrichtung zur erzeugung von hochenergetischer röntgenstrahlung

Family Cites Families (2)

* 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
CA1099034A (en) * 1977-10-21 1981-04-07 Leonhard Taumann Electron accelerator comprising a target exposed to the electron beam

Also Published As

Publication number Publication date
DE3061500D1 (en) 1983-02-03
JPS6327679B2 (esLanguage) 1988-06-03
CA1145863A (en) 1983-05-03
JPS5614198A (en) 1981-02-10
EP0021442A1 (de) 1981-01-07
DE2926841A1 (de) 1981-01-22
US4327293A (en) 1982-04-27

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