WO2007093965A1 - A neutron therapy target and installation, and a method of producing neutrons - Google Patents

A neutron therapy target and installation, and a method of producing neutrons Download PDF

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Publication number
WO2007093965A1
WO2007093965A1 PCT/IB2007/050487 IB2007050487W WO2007093965A1 WO 2007093965 A1 WO2007093965 A1 WO 2007093965A1 IB 2007050487 W IB2007050487 W IB 2007050487W WO 2007093965 A1 WO2007093965 A1 WO 2007093965A1
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WIPO (PCT)
Prior art keywords
target
neutron
intensity
incident beam
target volume
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Application number
PCT/IB2007/050487
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French (fr)
Inventor
Pierre Mandrillon
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Accelerators For Industrial & Medical Applications. Engineering Promotions Society. Aima.Eps
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Application filed by Accelerators For Industrial & Medical Applications. Engineering Promotions Society. Aima.Eps filed Critical Accelerators For Industrial & Medical Applications. Engineering Promotions Society. Aima.Eps
Publication of WO2007093965A1 publication Critical patent/WO2007093965A1/en

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N5/00—Radiation therapy
    • A61N5/10—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
    • A61N5/1042—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy with spatial modulation of the radiation beam within the treatment head
    • 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
    • G21K5/00—Irradiation devices
    • G21K5/04—Irradiation devices with beam-forming means
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H3/00—Production or acceleration of neutral particle beams, e.g. molecular or atomic beams
    • H05H3/06—Generating neutron beams
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H6/00—Targets for producing nuclear reactions
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N5/00—Radiation therapy
    • A61N5/10—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
    • A61N2005/1085—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy characterised by the type of particles applied to the patient
    • A61N2005/109—Neutrons

Definitions

  • the present invention relates to a target for producing an emerging beam of neutrons from an incident beam of charged particles, in particular protons, it relates to an installation for producing neutrons in particular for the purpose of treating tumors of neutron therapy, and it also relates to a method of producing neutrons for directing towards a target volume.
  • IMRT intensity modulated radiation therapy
  • Neutrons present radiobiological properties that are advantageous, but they are used relatively little at present because of the lack of suitable installations available for treating a wide variety of tumors.
  • the invention provides a target for producing an emerging beam of neutrons from an incident beam of charged particles, the target comprising:
  • a neutron-generator material • a neutron-generator material; and • an actuator system for responding to receiving a control signal by varying the thickness of neutron- generator material opposed to the incident beam.
  • the energy and the intensity of the neutrons flux of the emerging beam which are a function in particular of the thickness of the neutron-generator material through which the incident beam passes and the energy and the intensity of the incident beam, can be modulated more easily so as to be adapted to the target volume to be treated and to its location in the body.
  • the thickness of the neutron-generator material quickly to the intensity and to the energy of the incident beam so as to optimize production of neutrons having energy adapted to destroying cancer cells at a given depth.
  • the invention makes it possible to vary the energy of the neutrons as a function of their angle of incidence relative to the target volume and to perform angular scanning around the target volume with energy adapted to each angle of incidence.
  • the charged particles of the incident beam may be protons or other particles.
  • the actuator system may comprise a remotely-controlled hydraulic, pneumatic, electromechanical, or other system.
  • the block (s) is/are secured to actuators enabling them to be placed selectively on the path of the incident beam, and where appropriate with a desired orientation.
  • the target may have at least two blocks of neutron- generator material, e.g. placed selectively on the path of the incident beam by the actuator system, or else a single block of neutron-generator material presenting a shape that, when moved relative to the incident beam, e.g. in rotation and/or in translation, makes it possible to vary the thickness of the neutron-generator material opposing the incident beam.
  • the shape may be prismatic, a helical ramp, or steps of a staircase .
  • the blocks of neutron-generator material may optionally be touching.
  • the presence of a plurality of non-touching blocks can make them easier to cool, by causing a fluid to flow between them, e.g. a fluid such as helium.
  • the number of blocks may be greater than or equal to five, so as to enable the thickness of the neutron- generator material opposing the incident beam to be modulated sufficiently finely, and better it is greater than or equal to ten.
  • the blocks may be of the same thickness or they may have thicknesses that vary in a non-linear relationship so as to make it possible to vary the thickness opposing the incident beam in a manner that does not depend linearly on the number of blocks interposed. Where appropriate, each block may itself present thickness that is not constant, in particular it may present thickness that varies linearly or in steps. This can make it possible to vary the thickness of the neutron-generator material opposing the beam, e.g. by pushing such a block to a greater or lesser extent onto the path of the beam.
  • the neutron-generator material may comprise beryllium, for example.
  • the target may include means for producing a magnetic field, e.g. at least one permanent magnet, arranged to produce a magnetic field on the path of the beam after passing through the neutron-generator material, so as to deflect the charged particles that have passed through the neutron-generator material without reacting.
  • a magnetic field e.g. at least one permanent magnet
  • the invention also provides an installation for producing neutrons, the installation comprising:
  • the neutron flux of the emerging beam can be modulated in intensity and/or energy by varying the thickness of the neutron-generator material opposing the incident beam.
  • the installation may also advantageously include a system for controlling the intensity of the incident beam so as to make it possible to modulate the intensity and/or the energy thereof. This can make it possible to modulate the intensity and/or the energy of the incident beam so as to optimize the production of neutrons with a predefined energy, for a given thickness of neutron- generator material.
  • the intensity and/or the energy of the incident beam may be modulated as a function of the angle of incidence of the emerging beam of neutrons relative to the target volume.
  • the target may be arranged to receive the above- mentioned control signal from the system for controlling the intensity of the incident beam.
  • the thickness of neutron-generator material opposing the incident beam can be servo-controlled to the intensity and/or the energy thereof.
  • the system for controlling the intensity of the incident beam may, for example, comprise at least:
  • a programmable control device suitable for acting on the actuator as a function of the information delivered by the sensor and as a function of a programmed control relationship for the intensity of the beam of accelerated particles as a function of time so that the intensity of the incident beam delivered by the accelerator complies with the programmed control relationship .
  • system for controlling intensity may be as described in international application WO 03/092340, the content of which is incorporated in the present application by reference.
  • the installation may include a support for receiving a patient for treatment and a system for steering the emerging beam of neutrons relative to the patient.
  • the installation may include an isocentric head carrying the target.
  • the isocentric head may be configured to steer the emerging beam towards the patient at various angles of incidence relative to the target volume to be treated.
  • the installation may include a collimator, e.g. configured to adapt the section of the emerging beam of neutrons to the target volume it encounters.
  • the collimator may be a leaf collimator, in conventional manner.
  • the collimator may be arranged to enable the interception aperture of the neutrons to be modified in a manner that is programmable and variable as a function of the angle of incidence relative to the target volume.
  • the collimator may thus include means for individually driving each of the leaves.
  • An example of a leaf collimator is given in WO 00/13189.
  • the installation may include a computer system serving to determine the intensity and/or the energy of the neutrons to be produced as a function firstly of information relating to the target volume, in particular its location in the body, and secondly of the angle of incidence at the target volume and/or the depth of the target volume in the incident direction of the neutron beam.
  • the computer system may generate data that is useful for controlling the target and/or the accelerator and/or the collimator as a function at least of the angle of incidence relative to the target volume and/or the depth of the target volume.
  • the computer system may generate the above-mentioned control relationship for the intensity of the beam of charged particles delivered by the accelerator and/or it may generate the control signal for the target.
  • the computer system may comprise a computer such as a microcomputer which may constitute all or part of the above-mentioned programmable control device.
  • the control system may be arranged to receive information from the isocentric head relating to its position relative to the patient, in particular for the purpose of determining the angle of incidence at the target volume and/or the depth of the target volume.
  • the displacement of the isocentric head may be controlled by the control system.
  • the installation may include a system for acquiring 3D data of the target volume for treatment.
  • the 3D data may come from 3D imaging of the patient by nuclear magnetic resonance (NMR) or X-ray tomography or any other imaging technique, and by way of example it may be stored on a computer medium readable by the computer system or accessible thereby.
  • NMR nuclear magnetic resonance
  • X-ray tomography any other imaging technique, and by way of example it may be stored on a computer medium readable by the computer system or accessible thereby.
  • the particle accelerator may comprise a cyclotron, e.g. an optionally superconductive compact isochronous cyclotron .
  • the installation may include a system for detecting movements of the patient during a treatment session, in particular movements due to breathing and that might possibly affect the location of the target volume.
  • the intensity control system may be configured to modulate the intensity of the beam of charged particles and/or the thickness of the neutron-generator material in real time as a function of the movements detected.
  • the installation may include an electron stripper exposed to the beam of particles in the accelerator so as to extract the particles and form the incident beam.
  • the stripper may be in solid form, and for example it may comprise a thin sheet of carbon.
  • the invention also provides a method of producing neutrons for directing towards a target volume, the method comprising the steps consisting in:
  • the method may also include the step consisting in causing the intensity of the incident beam to vary as a function of the angle of incidence of the emerging beam at the target volume and/or as a function of the depth of the target volume.
  • the method may also include the step consisting in causing the interception aperture of the emerging beam to vary by means of a collimator as a function of the angle of incidence at the target volume.
  • at least two neutron beams are generated with angles of incidence that are spaced apart by at least 10°, better by at least 60°.
  • At least three, better five, better still ten emerging neutron beams can be generated in succession at different angles of incidence.
  • the thicknesses of the neutron-generator material passed through may be different so as to take account in particular of the different distances to be traveled through tissue before reaching the target volume.
  • the beam When changing the angle of incidence, the beam may be stopped, e.g. by using the intensity control system.
  • Figure 1 is a diagrammatic and fragmentary view of a neutron therapy installation of the invention
  • Figure 2 is a diagrammatic view of a detail of Figure 1 relating to the target;
  • Figure 3 is a diagram showing neutron production by the neutron-generator material
  • Figure 4 is a diagram showing the target volume for various angles of incidence of the emerging beam at the target volume
  • Figures 5 and 6 are diagrams showing examples of shapes for a block of neutron-generator material; and • Figure 7 is a diagram showing the operation of the various elements of the installation in Figure 1.
  • Figures 1, 2, and 7 show a neutron therapy installation 1 comprising an accelerator 2 and an isocentric head 3 shaped to steer a beam of accelerated particles towards a target volume T within a patient P, at various desired angles of incidence ⁇ relative to the target volume.
  • the installation comprises devices 4 for deflecting and/or guiding the incident beam of charged particles coming from the accelerator 2 towards the isocentric head 3.
  • the accelerator 2 is a cyclotron of the compact isochronous type, which may optionally be superconductive. Any other type of accelerator, e.g. a linear cyclotron or a synchrocyclontron, could be used.
  • the accelerator 2 may be suitable for supplying an incident beam of charged particles, e.g. protons, at an energy greater than 65 MeV.
  • the isocentric head 3 carries a target 5 and a collimator 6.
  • the collimator 6 may have a plurality of leaves individually actuated in response to a control signal w.
  • Figure 4 shows three different angles of incidence G 1 , ⁇ 2 , and ⁇ 3 for the neutron beam.
  • the target 5 may comprise one or more blocks 11 of neutron-generator material that can be superposed.
  • the number of blocks 11 lies in the range 1 to 10.
  • the charged particles are protons H + and the neutron-generator material may be beryllium.
  • the target 5 also comprises an actuator system 12 for actuating the blocks 11 so as to move them and vary the number of blocks 11 that are placed on the path of the incident beam, and thus vary the thickness of the neutron-generator material through which the beam passes, in response to receiving a control signal s.
  • the actuator system 12 may comprise actuators that are pneumatic, hydraulic, or electrical, and that are not shown in detail in order to clarify the drawing.
  • Each of the blocks 11 may present the shape of a disk or some other shape, e.g. the shape of a plate having an outline that is not circular.
  • Each block 11 may present thickness that is constant or not constant, and its thickness may vary in a manner that is linear or not linear.
  • each block 11 may be in the form of a prism, as shown in Figure 5, or it may comprise steps, as shown in Figure 6.
  • a block 11 When a block 11 presents thickness that is not constant, it may be put into place on the path of the incident beam of particles by being moved in translation, for example, with the thickness opposed to the beam varying depending on the extent to which it is pushed in.
  • the target 5 can be made up of a plurality of blocks 11 of neutron-generator material which can optionally be placed on the path of the incident beam of particles by being moved in translation, and it is also possible to cause at least one of the blocks 11 to pivot so as to further modify the thickness of the neutron-generator material that intercepts the incident beam.
  • the target 5 has means 15 for producing a magnetic field that comprise, in the example shown, a permanent magnet disposed downstream from the neutron-generator material on the path of the emerging beam. This makes it possible to eliminate the charged particles that have not reacted with the neutron- generator material, e.g. by directing them towards a carbon collector.
  • the installation 1 in the example described includes a source 40 for generating the ions to be accelerated, e.g. a source of H + ions.
  • An actuator 30 is installed upstream from the accelerator 2 to act on the intensity of the beam for acceleration, in response to a control signal v.
  • the intensity of the beam of particles accelerated in the accelerator 2 can be measured using the electron stripper 7.
  • the installation includes a system for controlling its operation.
  • the control system may be made up of a plurality of apparatuses or by a single apparatus, and it may be present entirely on site or it may be located remotely, at least in part. It may include a computer system comprising one or more computers, e.g. a microcomputer.
  • control system includes a programmable control device 35 arranged to send the control signal v to the actuator 30 in such a manner that the intensity of the incident beam delivered by the accelerator satisfies a predefined control relationship.
  • the installation 1 may include a system for acquiring 3D data relating to the target volume T, making it possible for each angle of incidence ⁇ to calculate the depth h of the target volume T in the direction of incidence of the beam, the intensity of the incident beam, the thickness of the neutron-generator material, and the shape to be given to the beam of neutrons.
  • the control device 35 may receive information relating to the target volume T, in particular the 3D shape thereof and its location within the body of the patient .
  • the control device 35 may generate the control signals s and w sent respectively to the target 5 and to the collimator 6 for a given angle of incidence ⁇ as a function of the 3D data relating to the target volume.
  • Displacement of the isocentric head 3 may be controlled by the control device 35, which may be programmed for example so that the installation delivers a plurality of neutron beams at different angles of incidence ⁇ .
  • the programmable control device 35 may vary the intensity of the incident beam and the thickness of the neutron-generator material through which the incident beam passes in corresponding manner, the neutron flux of the emerging beam being a function both of the intensity of the incident beam and of the thickness of the neutron- generator material passed through, so as to obtain a distribution of dose as a function of depth that is optimized for a given angle of incidence ⁇ .
  • the installation may also include a detector system (not shown) for detecting movements of the patient.
  • the control device 35 may also be configured to modulate intensity and/or energy as a function of the movements of the target volume or to trigger beam emission only when the positioning of the target volume is correct.
  • the invention is not limited to the embodiments described above. The invention thus has applications that are nonmedical, e.g. in materials testing, for example.
  • the accelerator 2 may be replaced by a set of at least two accelerators, one serving to accelerate particles that have been pre-accelerated by the other.

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Abstract

The present invention relates to a target for producing an emerging beam of neutrons from an incident beam of charged particles, the target comprising: a neutron-generator material; and an actuator system for responding to receiving a control signal by varying the thickness of neutron-generator material opposed to the incident beam.

Description

A NEUTRON THERAPY TARGET AND INSTALLATION, AND A METHOD
OF PRODUCING NEUTRONS
The present invention relates to a target for producing an emerging beam of neutrons from an incident beam of charged particles, in particular protons, it relates to an installation for producing neutrons in particular for the purpose of treating tumors of neutron therapy, and it also relates to a method of producing neutrons for directing towards a target volume. The article concerning radiotherapy entitled "Du radium aux accelerateurs lineaires et ions lourds dans Ie traitement du cancer: apport de l'UCL" [From radium to linear accelerators and heavy ions in treating cancer: the contribution of UCL] by Andre Wambersie in May 2001 gives a view of neutron therapy and proton therapy.
In the field of radiotherapy, it is known to adapt the dose of radiation to the three-dimensional shape of the tumor by modulating the intensity of the incident beam as a function of the angle of incidence, in order to direct the largest dose of radiation towards the tumor, while minimizing the exposure to radiation of nearby healthy tissue. This is known as intensity modulated radiation therapy (IMRT).
Neutrons present radiobiological properties that are advantageous, but they are used relatively little at present because of the lack of suitable installations available for treating a wide variety of tumors.
Existing neutron therapy installations produce the neutron flux from a beam of H+ protons directed to a beryllium target of constant thickness. A collimator placed behind the target serves to give the desired section to the beam of neutrons.
The article "MEDICYC: a 60 MeV proton cyclotron associated with a new target design for neutron therapy" by Pierre Mandrillon et al . , discloses the use of lithium deuteride as the neutron-generator material instead of beryllium. A series of lithium deuteride disks are disposed on the path of the proton beam, being cooled by a forced flow of helium. The protons that have not reacted are deflected by a magnet and directed towards a carbon collector. There exists a need to further improve neutron therapy installations in order to deliver an appropriate dose to the target volume while sparing nearby healthy tissue as much as possible, and to do this in a length of time that is relatively comfortable for the patient. According to one of its aspects, the invention provides a target for producing an emerging beam of neutrons from an incident beam of charged particles, the target comprising:
• a neutron-generator material; and • an actuator system for responding to receiving a control signal by varying the thickness of neutron- generator material opposed to the incident beam.
By means of the invention, the energy and the intensity of the neutrons flux of the emerging beam, which are a function in particular of the thickness of the neutron-generator material through which the incident beam passes and the energy and the intensity of the incident beam, can be modulated more easily so as to be adapted to the target volume to be treated and to its location in the body.
For example, it becomes possible with the invention to adapt the thickness of the neutron-generator material quickly to the intensity and to the energy of the incident beam so as to optimize production of neutrons having energy adapted to destroying cancer cells at a given depth.
The invention makes it possible to vary the energy of the neutrons as a function of their angle of incidence relative to the target volume and to perform angular scanning around the target volume with energy adapted to each angle of incidence. By way of example, the charged particles of the incident beam may be protons or other particles.
By way of example, the actuator system may comprise a remotely-controlled hydraulic, pneumatic, electromechanical, or other system.
By way of example, the block (s) is/are secured to actuators enabling them to be placed selectively on the path of the incident beam, and where appropriate with a desired orientation. The target may have at least two blocks of neutron- generator material, e.g. placed selectively on the path of the incident beam by the actuator system, or else a single block of neutron-generator material presenting a shape that, when moved relative to the incident beam, e.g. in rotation and/or in translation, makes it possible to vary the thickness of the neutron-generator material opposing the incident beam. By way of example, the shape may be prismatic, a helical ramp, or steps of a staircase . The blocks of neutron-generator material may optionally be touching. The presence of a plurality of non-touching blocks can make them easier to cool, by causing a fluid to flow between them, e.g. a fluid such as helium. The number of blocks may be greater than or equal to five, so as to enable the thickness of the neutron- generator material opposing the incident beam to be modulated sufficiently finely, and better it is greater than or equal to ten. The blocks may be of the same thickness or they may have thicknesses that vary in a non-linear relationship so as to make it possible to vary the thickness opposing the incident beam in a manner that does not depend linearly on the number of blocks interposed. Where appropriate, each block may itself present thickness that is not constant, in particular it may present thickness that varies linearly or in steps. This can make it possible to vary the thickness of the neutron-generator material opposing the beam, e.g. by pushing such a block to a greater or lesser extent onto the path of the beam.
The neutron-generator material may comprise beryllium, for example.
The target may include means for producing a magnetic field, e.g. at least one permanent magnet, arranged to produce a magnetic field on the path of the beam after passing through the neutron-generator material, so as to deflect the charged particles that have passed through the neutron-generator material without reacting.
In another of its aspects, the invention also provides an installation for producing neutrons, the installation comprising:
• a target as defined above; and
• a particle accelerator arranged to produce the incident beam of charged particles.
By means of such an installation, the neutron flux of the emerging beam can be modulated in intensity and/or energy by varying the thickness of the neutron-generator material opposing the incident beam.
The installation may also advantageously include a system for controlling the intensity of the incident beam so as to make it possible to modulate the intensity and/or the energy thereof. This can make it possible to modulate the intensity and/or the energy of the incident beam so as to optimize the production of neutrons with a predefined energy, for a given thickness of neutron- generator material.
By way of example, the intensity and/or the energy of the incident beam may be modulated as a function of the angle of incidence of the emerging beam of neutrons relative to the target volume. The target may be arranged to receive the above- mentioned control signal from the system for controlling the intensity of the incident beam. Thus, the thickness of neutron-generator material opposing the incident beam can be servo-controlled to the intensity and/or the energy thereof.
The system for controlling the intensity of the incident beam may, for example, comprise at least:
• an actuator for acting on the particles before they are accelerated in the accelerator;
• at least one sensor arranged to deliver information representative of the intensity of the beam of particles accelerated by the accelerator; and
• a programmable control device suitable for acting on the actuator as a function of the information delivered by the sensor and as a function of a programmed control relationship for the intensity of the beam of accelerated particles as a function of time so that the intensity of the incident beam delivered by the accelerator complies with the programmed control relationship .
By way of example, the system for controlling intensity may be as described in international application WO 03/092340, the content of which is incorporated in the present application by reference.
The installation may include a support for receiving a patient for treatment and a system for steering the emerging beam of neutrons relative to the patient.
By way of example, the installation may include an isocentric head carrying the target. The isocentric head may be configured to steer the emerging beam towards the patient at various angles of incidence relative to the target volume to be treated.
The installation may include a collimator, e.g. configured to adapt the section of the emerging beam of neutrons to the target volume it encounters. By way of example, the collimator may be a leaf collimator, in conventional manner.
The collimator may be arranged to enable the interception aperture of the neutrons to be modified in a manner that is programmable and variable as a function of the angle of incidence relative to the target volume. The collimator may thus include means for individually driving each of the leaves. An example of a leaf collimator is given in WO 00/13189.
The installation may include a computer system serving to determine the intensity and/or the energy of the neutrons to be produced as a function firstly of information relating to the target volume, in particular its location in the body, and secondly of the angle of incidence at the target volume and/or the depth of the target volume in the incident direction of the neutron beam.
By way of example, the computer system may generate data that is useful for controlling the target and/or the accelerator and/or the collimator as a function at least of the angle of incidence relative to the target volume and/or the depth of the target volume.
By way of example, the computer system may generate the above-mentioned control relationship for the intensity of the beam of charged particles delivered by the accelerator and/or it may generate the control signal for the target.
The computer system may comprise a computer such as a microcomputer which may constitute all or part of the above-mentioned programmable control device.
The control system may be arranged to receive information from the isocentric head relating to its position relative to the patient, in particular for the purpose of determining the angle of incidence at the target volume and/or the depth of the target volume.
The displacement of the isocentric head may be controlled by the control system.
The installation may include a system for acquiring 3D data of the target volume for treatment. By way of example, the 3D data may come from 3D imaging of the patient by nuclear magnetic resonance (NMR) or X-ray tomography or any other imaging technique, and by way of example it may be stored on a computer medium readable by the computer system or accessible thereby.
The particle accelerator may comprise a cyclotron, e.g. an optionally superconductive compact isochronous cyclotron .
The installation may include a system for detecting movements of the patient during a treatment session, in particular movements due to breathing and that might possibly affect the location of the target volume.
The intensity control system may be configured to modulate the intensity of the beam of charged particles and/or the thickness of the neutron-generator material in real time as a function of the movements detected. The installation may include an electron stripper exposed to the beam of particles in the accelerator so as to extract the particles and form the incident beam. The stripper may be in solid form, and for example it may comprise a thin sheet of carbon. In another of its aspects, the invention also provides a method of producing neutrons for directing towards a target volume, the method comprising the steps consisting in:
• generating an incident beam of accelerated charged particles and directing it towards a target including a neutron-generator material so as to generate an emerging beam of neutrons; and
• causing the thickness of the neutron-generator material through which the incident beam passes to vary as a function at least of an angle of incidence of the emerging beam at the target volume and/or the depth of the target volume, i.e. the thickness of material to be passed through before reaching the target volume.
This enables the distribution of the dose to be adapted to the depth of the cells to be destroyed in the body. The method may also include the step consisting in causing the intensity of the incident beam to vary as a function of the angle of incidence of the emerging beam at the target volume and/or as a function of the depth of the target volume.
The method may also include the step consisting in causing the interception aperture of the emerging beam to vary by means of a collimator as a function of the angle of incidence at the target volume. In an embodiment of the invention, at least two neutron beams are generated with angles of incidence that are spaced apart by at least 10°, better by at least 60°. At least three, better five, better still ten emerging neutron beams can be generated in succession at different angles of incidence.
For at least two of these beams, the thicknesses of the neutron-generator material passed through may be different so as to take account in particular of the different distances to be traveled through tissue before reaching the target volume.
When changing the angle of incidence, the beam may be stopped, e.g. by using the intensity control system.
The invention can be better understood on reading the following detailed description of non-limiting embodiments thereof, and on examining the accompanying drawings, in which:
• Figure 1 is a diagrammatic and fragmentary view of a neutron therapy installation of the invention;
• Figure 2 is a diagrammatic view of a detail of Figure 1 relating to the target;
• Figure 3 is a diagram showing neutron production by the neutron-generator material;
• Figure 4 is a diagram showing the target volume for various angles of incidence of the emerging beam at the target volume;
• Figures 5 and 6 are diagrams showing examples of shapes for a block of neutron-generator material; and • Figure 7 is a diagram showing the operation of the various elements of the installation in Figure 1.
Figures 1, 2, and 7 show a neutron therapy installation 1 comprising an accelerator 2 and an isocentric head 3 shaped to steer a beam of accelerated particles towards a target volume T within a patient P, at various desired angles of incidence θ relative to the target volume.
The installation comprises devices 4 for deflecting and/or guiding the incident beam of charged particles coming from the accelerator 2 towards the isocentric head 3.
In the example shown, the accelerator 2 is a cyclotron of the compact isochronous type, which may optionally be superconductive. Any other type of accelerator, e.g. a linear cyclotron or a synchrocyclontron, could be used.
The accelerator 2 may be suitable for supplying an incident beam of charged particles, e.g. protons, at an energy greater than 65 MeV.
The isocentric head 3 carries a target 5 and a collimator 6. The collimator 6 may have a plurality of leaves individually actuated in response to a control signal w. By means of the isocentric head 3, it is possible to modify the angle of incidence θ of the emerging beam of neutrons at the target volume T, relative to the vertical X or to any other reference direction. The angle θ is measured around the longitudinal axis of the patient, for example.
By way of example, Figure 4 shows three different angles of incidence G1, θ2, and θ3 for the neutron beam.
The target 5 may comprise one or more blocks 11 of neutron-generator material that can be superposed. By way of example, the number of blocks 11 lies in the range 1 to 10. By way of example, the charged particles are protons H+ and the neutron-generator material may be beryllium.
As shown in Figure 7, the target 5 also comprises an actuator system 12 for actuating the blocks 11 so as to move them and vary the number of blocks 11 that are placed on the path of the incident beam, and thus vary the thickness of the neutron-generator material through which the beam passes, in response to receiving a control signal s. The actuator system 12 may comprise actuators that are pneumatic, hydraulic, or electrical, and that are not shown in detail in order to clarify the drawing.
Each of the blocks 11 may present the shape of a disk or some other shape, e.g. the shape of a plate having an outline that is not circular.
Each block 11 may present thickness that is constant or not constant, and its thickness may vary in a manner that is linear or not linear.
By way of example, each block 11 may be in the form of a prism, as shown in Figure 5, or it may comprise steps, as shown in Figure 6.
When a block 11 presents thickness that is not constant, it may be put into place on the path of the incident beam of particles by being moved in translation, for example, with the thickness opposed to the beam varying depending on the extent to which it is pushed in.
It is also possible to vary the thickness of the neutron-generator material through which the beam passes by using a single block 11 of constant thickness and by pivoting the block.
Where appropriate, the target 5 can be made up of a plurality of blocks 11 of neutron-generator material which can optionally be placed on the path of the incident beam of particles by being moved in translation, and it is also possible to cause at least one of the blocks 11 to pivot so as to further modify the thickness of the neutron-generator material that intercepts the incident beam.
In the example shown, the target 5 has means 15 for producing a magnetic field that comprise, in the example shown, a permanent magnet disposed downstream from the neutron-generator material on the path of the emerging beam. This makes it possible to eliminate the charged particles that have not reacted with the neutron- generator material, e.g. by directing them towards a carbon collector.
The installation 1 in the example described includes a source 40 for generating the ions to be accelerated, e.g. a source of H+ ions.
An actuator 30 is installed upstream from the accelerator 2 to act on the intensity of the beam for acceleration, in response to a control signal v.
An electron stripper 7, e.g. comprising a thin sheet of carbon, is placed on the path of the beam of particles accelerated inside the accelerator 2, in order to enable it to be extracted.
The intensity of the beam of particles accelerated in the accelerator 2 can be measured using the electron stripper 7.
The installation includes a system for controlling its operation. The control system may be made up of a plurality of apparatuses or by a single apparatus, and it may be present entirely on site or it may be located remotely, at least in part. It may include a computer system comprising one or more computers, e.g. a microcomputer.
In the example shown, the control system includes a programmable control device 35 arranged to send the control signal v to the actuator 30 in such a manner that the intensity of the incident beam delivered by the accelerator satisfies a predefined control relationship.
The installation 1 may include a system for acquiring 3D data relating to the target volume T, making it possible for each angle of incidence θ to calculate the depth h of the target volume T in the direction of incidence of the beam, the intensity of the incident beam, the thickness of the neutron-generator material, and the shape to be given to the beam of neutrons. The control device 35 may receive information relating to the target volume T, in particular the 3D shape thereof and its location within the body of the patient . The control device 35 may generate the control signals s and w sent respectively to the target 5 and to the collimator 6 for a given angle of incidence θ as a function of the 3D data relating to the target volume. Displacement of the isocentric head 3 may be controlled by the control device 35, which may be programmed for example so that the installation delivers a plurality of neutron beams at different angles of incidence θ.
The programmable control device 35 may vary the intensity of the incident beam and the thickness of the neutron-generator material through which the incident beam passes in corresponding manner, the neutron flux of the emerging beam being a function both of the intensity of the incident beam and of the thickness of the neutron- generator material passed through, so as to obtain a distribution of dose as a function of depth that is optimized for a given angle of incidence θ.
The installation may also include a detector system (not shown) for detecting movements of the patient. Under such circumstances, the control device 35 may also be configured to modulate intensity and/or energy as a function of the movements of the target volume or to trigger beam emission only when the positioning of the target volume is correct. Naturally, the invention is not limited to the embodiments described above. The invention thus has applications that are nonmedical, e.g. in materials testing, for example.
The accelerator 2 may be replaced by a set of at least two accelerators, one serving to accelerate particles that have been pre-accelerated by the other.
The term "comprising a" should be understood as being synonymous with "comprising at least one", unless specified to the contrary.

Claims

WHAT IS CLAIMED IS:
1. A target for producing an emerging beam of neutrons from an incident beam of charged particles, the target comprising: • a neutron-generator material; and
• an actuator system for responding to receiving a control signal by varying the thickness of neutron- generator material opposed to the incident beam.
2. A target according to claim 1, having at least two blocks of neutron-generator material.
3. A target according to claim 1, having a single block of neutron-generator material.
4. A target according to claim 1, in which the neutron- generator material comprises beryllium.
5. A target according to claim 1, including magnetic field production means arranged to produce a magnetic field on the path of the emerging beam after passing the neutron-generator material, and in particular at least one permanent magnet.
6. An installation for producing neutrons, the installation comprising:
• a target as defined in claim 1; and
• an accelerator arranged to produce the incident beam of charged particles.
7. An installation according to claim 6, including a system for controlling the intensity of the incident beam.
8. An installation according to claim 6, including a support for receiving a patient for treatment and a system for steering the emerging beam of neutrons relative to the patient.
9. An installation according to claim 6, including an isocentric head carrying the target.
10. An installation according to claim 6, including a collimator, in particular a leaf collimator.
11. An installation according to claim 6, including a system for calculating the intensity of the incident beam as a function at least of the angle of incidence at the target volume, and/or of the depth of the target volume.
12. An installation according to claim 6, including a 3D data acquisition system relating to a target volume for treatment in the patient.
13. An installation according to claim 6, in which the accelerator comprises a cyclotron.
14. An installation according to claim 7, in which the intensity control system comprises:
• an actuator for acting on the particles before they are accelerated in the accelerator;
• at least one sensor arranged to deliver information representative of the intensity of the beam of particles accelerated by the accelerator; and
• a programmable control device suitable for acting on the actuator as a function of the information delivered by the sensor and as a function of a programmed control relationship for the intensity of the beam of accelerated particles as a function of time so that the intensity of the incident beam delivered by the accelerator complies with the programmed control relationship .
15. An installation according to claim 6, including a system for detecting movements of the patient, the system for controlling intensity being configured to modify the intensity as a function of movements of the patient that affect the positioning of the target volume.
16. A system for producing neutrons for directing towards a target volume, the method comprising the steps consisting in: • generating an incident beam of accelerated charged particles and directing it towards a target including a neutron-generator material so as to generate an emerging beam of neutrons; and
• causing the thickness of the neutron-generator material through which the incident beam passes to vary as a function at least of the angle of incidence of the emerging beam at the target volume and/or as a function of the depth of the target volume.
17. A method according to claim 16, including the step consisting in causing the intensity of the incident beam to vary as a function of the angle of incidence of the emerging beam at the target volume and/or as a function of the depth of the target volume.
PCT/IB2007/050487 2006-02-14 2007-02-14 A neutron therapy target and installation, and a method of producing neutrons WO2007093965A1 (en)

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FR0650539A FR2897502B1 (en) 2006-02-14 2006-02-14 TARGET, NEUTRONTHERAPY PLANT AND METHOD FOR PRODUCING NEUTRONS.

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CN108934120B (en) * 2017-05-26 2024-04-12 南京中硼联康医疗科技有限公司 Target for neutron ray generating device and neutron capturing treatment system

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