JP2008086762A - Particle-beam radiation therapy system and scanning method for particle-beam radiation therapy - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve irradiation of a moving target on particle-beam radiation therapy by the raster scanning method. <P>SOLUTION: The particle-beam radiation therapy system for particle-beam radiation therapy of a target volume subjected to motion of a patient includes a particle accelerator for furnishing high-energy particles, a setting device that sets a size of an irradiation volume interacting for therapy between the particles and tissue, a control system configured for controlling the setting device to output a control signal for setting a three-dimensional size of the irradiation volume to a setting device so that the motion is stopped or slowed down to scan the entire target volume in order to control the setting device, and a scanner controllable so that the entire target volume can be scanned by the irradiation volume within the time period. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a particle beam therapy apparatus for irradiating a patient and a method for irradiating a patient.

  Particle beam therapy devices typically have an accelerator unit and a high energy beam guidance system. The acceleration of the particles, for example protons, pions, helium ions, carbon ions or oxygen ions, is carried out by means of a synchrotron, for example, which is supplied with particles which have been previously accelerated by a linear accelerator. The particles are accelerated to the desired energy with a linear accelerator and accumulated for irradiation. As an alternative, acceleration can also take place via a cyclotron, in which case it is possible to set different energies, for example via suitable energy absorbers, starting from the maximum energy.

  A high energy beam transport system guides particles from the accelerator unit to one or more treatment rooms. A distinction is made between fixed beam treatment rooms where the particles hit the treatment site from a fixed direction and so-called gantry treatment rooms. In the latter case, the particle beam can be directed to the patient from various directions.

  The particle beam is moved over the scanning range by the raster scanning device. For this purpose, the particle beam is adjusted, for example, by two deflecting magnets and is shifted laterally. Irradiation is particularly directed at volume elements. That is, at the time of treatment planning, the dose distribution to be applied is synthesized from small doses oriented to the volume element. The volume element generally has a size of 2 to 3 mm (beam diameter and equal energy layer thickness), so that the area to be irradiated, for example, the shape of the tumor can be traced well. In this case, the lateral size is adjusted by the ion beam optical system, and the size determined by the energy distribution of the beam, that is, the depth of the volume element is adjusted by a corresponding degrader, for example, a ripple filter. As a result, a normal raster interval of 2 to 3 mm occurs both in the lateral direction and in the penetration depth direction.

  Furthermore, the treatment plan divides the irradiation process into multiple units. The division may be geometric on the one hand, i.e. a division into adjacent fields having a size given by the maximum scanable field of the raster scanning device. On the other hand, for example, in order to obtain a corresponding effect by allocating to a large number of irradiation treatments, it is preferable to divide into irradiation units that are temporally continuous.

  The control and safety system of the particle beam therapy device ensures that the particle beam characterized by the required parameters is guided to the corresponding treatment room each time. The parameters are determined in a so-called treatment plan. The treatment plan specifies how much energy the particles have and from what direction and how much the patient or each volume element should be applied to. The energy of the particles determines the depth of penetration into the patient, i.e. the position of the volume element. A dose peak is achieved at this position. Therefore, the energy distribution of the particle beam determines the dose distribution in the incident direction. The energy distribution of the particle beam determines the size of the irradiation volume correspondingly with the beam parameters as well as the beam shape.

  In general, there is a beam monitoring element in front of the patient, for example monitoring the position and / or intensity of the particle beam. The position of the particle beam and the beam shape of the particle beam are generally measured in transmission by an appropriate detector, such as an ionization chamber or multichannel chamber, present in the beam path near the patient during irradiation.

  Positioning the patient within the scanning range of the particle beam therapy device is generally performed by a patient positioning device in the treatment room. In particular, for the verification of the position of the irradiation position of a fixed patient, the fluoroscopic image is generally compared with CT data from the treatment plan before the start of irradiation, and in some cases, the patient is supplementally adjusted. Furthermore, patient movement can enlarge the scannable area.

  For example, in the case of irradiation by the raster scanning method, the movement of the target volume or irradiated volume affects the uniformity of the applied particle beam (see, for example, Non-Patent Document 1). Due to interference between beam application and object movement, the applied dose distribution no longer matches the planned dose distribution. The applied dose distribution is non-uniform due to motion. That is, dose deficiency and / or line excess occurs.

  This type of non-uniformity is reduced by repeated scanning of the energy layer with a reduced dose. This is because the non-uniformity is small and exists at various locations in the scanning range. Of course, in this case, a safety region should be placed around the tissue to be irradiated, taking into account the amplitude of movement and thereby ensuring that the tissue to be irradiated is sufficiently irradiated. Furthermore, since the energy layers in contact with each other are given different motions, there is an additional problem that non-uniformity occurs in the Z direction, that is, the incident beam direction.

For example, irradiating a subject that moves based on respiration by narrowing (gating) the treatment beam in synchronism with the motion avoids the effects of motion by limiting the irradiation to a quasi-stationary motion state. Therefore, the lateral safety area is reduced. This type of particle beam therapy apparatus is known (for example, see Non-Patent Document 2). Breathing stops also produce a quasi-static state. In this case, of course, as in the case of gating, non-uniformity still occurs in the dose distribution, particularly in the transition range of the energy layer in contact.
M.M. H. Phillips et all. , “Effects of respiratory motion on dose uniformity with a charged particle scanning method”, Phys. Med Biol. 1992, Vol. 32, no. 1,223-234 S. Minohara et al. "Respiratory Gate Irradiation System for Heavy-ion Radiotherapy", Int. J. et al. Radiation Oncology Biol. Phys. , Vol. 47, no. 4, pp. 1097-1103, 2000

  An object of the present invention is to provide a particle beam therapy apparatus and a scanning method for particle beam therapy that improve irradiation of a moving object during particle beam therapy by a raster scanning method.

  A problem related to a particle beam therapy system is that according to the present invention, in a particle beam therapy system for particle beam therapy for a target volume exposed to motion in a patient, a particle accelerator for supplying high-energy particles, and a particle therapy A setting device for setting the size of the irradiation volume that interacts with the tissue for the purpose, and the entire target volume can be irradiated during the time interval to stop or slow the movement to control the setting device A control system configured to output a control signal for setting the three-dimensional size of the irradiation volume to the setting device, and control so that the entire target volume can be scanned within the time interval by the irradiation volume It is solved by having a scanning device that is possible.

The embodiment of the present invention relating to the particle beam therapy system is as follows.
The setting device has an adjusting device for adjusting the energy distribution of the particle beam that determines the size of the irradiation volume in the distal direction.
The setting device has high energy beam guiding means for adjusting the lateral size of the particle beam by the beam guiding optical system.
The setting device is configured to set the size ratio of the distal and lateral directions of the illumination volume equal to or greater than 2: 1.
The setting device is configured to set the irradiation volume to a beam incident direction size having at least 10% of a distal direction size of the target volume.
The setting device is configured to set the irradiation volume to a beam incident direction size within a range of 3 mm to 25 mm.
The setting device is configured to set the irradiation volume to a lateral size within a range of 5 mm to 10 mm.
The adjusting device is a grader, in particular a ripple filter.
The scanning device is a raster scanning device or a rocking device.
The particle accelerator is configured to set energy for irradiating a plurality of energy layers within one time interval.
Furthermore, energy setting means for irradiating a plurality of energy layers is provided.

  A problem relating to a scanning method for particle beam therapy is that, according to the present invention, the particle interacts with tissue for treatment in order to particle beam treat the target volume exposed to motion in the patient using the particle beam. In a scanning method for particle beam therapy in which a working irradiation volume is irradiated across a target volume, the movement of the target volume is stopped or delayed for one time interval to create a quasi-stationary target volume, the time interval It is solved by setting the irradiation volume to a three-dimensional size that allows the entire volume to be irradiated during the period of time, and scanning the entire target volume to be irradiated by the irradiation volume within that time interval .

An embodiment of the present invention relating to a scanning method for particle beam therapy is as follows.
The size ratio between the distal direction and the lateral direction of the irradiation volume is set equal to or greater than 2: 1.
The distal size of the irradiation volume is at least one third of the distal size of the target volume.
The distal direction size of the irradiation volume is in the range of 5 mm to 25 mm.
The lateral size of the irradiation volume is in the range of 3 mm to 10 mm.
At least one energy layer having an irradiation volume is scanned to scan the entire target volume to be irradiated.
The scanning method is a raster scanning method or a rocking method.

  A particle beam therapy system according to the present invention includes a particle accelerator for supplying high-energy particles, a setting device for setting the size of an irradiation volume, a control system for controlling the setting device, and a scanning device. Have. The setting device represents, for example, an optical system in particle beam guidance as well as an adjustment device for adjusting the energy distribution of the particles, for example by a control system for a time interval in which the respiratory movement is stopped (or delayed). In the meantime, the size of the irradiation volume that allows the entire target volume to be scanned is set. In this scanning process, at least one energy layer is irradiated by the irradiation volume as the target volume progresses.

  This configuration of the particle beam therapy device certainly allows a good spatial resolution for the normal irradiation volume in the scanning method, however, it requires a correspondingly long irradiation time in which motion can adversely affect the uniformity of the dose distribution. Is based on the recognition that Therefore, according to the present invention, the irradiation volume is adjusted so that the entire target volume is irradiated within a short time so that no boundary progress occurs between successive irradiation processes during irradiation. In particular, it is advantageous if a so-called needle beam (pencil beam) having a slight cross section is expanded in depth by a suitable absorber. That is, the energy distribution is broadened through, for example, a so-called ripple filter so that a Bragg peak region expanded in the incident direction of the beam is generated. Thus, only a few energy layers are irradiated, which is possible within the above time interval. The spatial resolution in the lateral direction remains substantially unchanged and the beam scans quickly in the lateral direction. In this case, the scanning speed is chosen for the patient to be treated, for example so that the entire target volume is illuminated during the sole phase of stopped breathing. This process is repeated many times until the necessary dose is accumulated in the target area each time breathing is stopped. For example, irradiation of multiple required energy layers is possible by a passive energy change occurring during one irradiation process within one time interval. As an alternative or addition to passive energy changes, the acceleration in the synchrotron can be changed.

  This type of particle beam therapy can cause under-dose or over-dose despite the fact that a motion state that is not exactly equal is applied in a quasi-static time interval, such as when the breath is synchronized or stopped. unforgivable. This is because neither the energy layer nor the lateral region is placed side by side in successive time intervals to achieve the desired dose distribution. Thus, this type of particle beam therapy device avoids the disadvantage that the individual irradiation points, irradiation range and energy layer are not aligned as desired. This is because the scanning process is performed in the same patient state over the entire volume each time, and deviations from the planned dose can only occur at the edge of the field. There is no significant dose variation within the target volume. Thus, additional enlargement, i.e. expansion and / or deepening (deepening) of the illumination volume allows for fast application of the entire area based on the reduced number of raster points and / or isoenergetic layers.

  A particularly preferred setting for the illumination volume is when the size ratio of the distal and lateral directions of the illumination volume is equal to or greater than 2: 1.

  Furthermore, it is particularly advantageous to set the irradiation volume to a beam incident direction size that has at least 10% of the distal size of the target volume. This makes it possible to scan a target volume with 10 or preferably 5 to 3 isoenergetic layers. For example, the distal dimension is in the range of 5 mm to 10 mm.

  For example, a raster device for a pencil beam or a swing device may be used as the scanning device.

  Furthermore, the present invention provides a scanning method in which a target volume exposed to (breathing) motion in a patient is to be irradiated with a particle beam, wherein the irradiation volume over which the particles interact with tissue for treatment extends over the target volume. It is solved by the scanning method that is irradiated. In this method, the movement of the target volume is stopped (or delayed) for one time interval to create a quasi-static target volume. Within this time interval, according to the conventional irradiation volume, only a part of the target volume could be irradiated. Therefore, according to the present invention, the irradiation volume is set to a size that enables irradiation of the entire volume to be irradiated within this time interval. Within such a time interval, the entire target volume to be irradiated is scanned with a correspondingly set irradiation volume and this process is repeated many times until the required dose is applied. This method has the further advantage that non-uniformities in the applied dose distribution are avoided.

Other advantageous embodiments of the particle beam therapy device and method are also characterized by the features of the dependent claims. In the following, embodiments of the present invention will be described with reference to FIGS.
FIG. 1 shows a schematic particle beam device,
FIG. 2 shows an apparatus for irradiation volume according to the prior art,
Figure 3 shows the dose distribution in the direction of incidence,
FIG. 4 shows how the target volume is divided into irradiation volumes for irradiation within one time interval.
FIG. 5 shows the dose distribution in the incident direction belonging to FIG.
FIG. 6 shows a state in which the target volume is divided into the irradiation volume using the expansion element.

  FIG. 1 shows a particle beam therapy system 1 including a front stage accelerator 3, a synchrotron 5, a scanning device 7, and a setting device 9. The control system 11 sets the energy of particles emitted from the synchrotron 5. The scanning device 7 enables lateral deflection of the particle beam in the X and Y directions. The scanning device 7 is similarly controlled by the control system 11, for example. The setting device 9 is, for example, a set of expansion elements, for example ripple filters, which expand the energy distribution of the beam, for example by 1, 2 times, 4 times and 8 times. Therefore, it is possible to set an irradiation volume that is extended by 2 times, 4 times or 8 times in the Z direction, that is, in the beam direction (distal direction).

  Generally, in particle beam therapy, an irradiation volume having a size of (3 mm, 3 mm, 2 mm) or (5 mm, 5 mm, 3-5 mm) in the X, Y, and Z directions is used. This makes it possible to align the irradiated volume in shape with the target volume 13 to be irradiated. If the target volume is near the lung and is therefore moved during breathing, the position of the target volume 13 and the position of the irradiated tissue in the particle beam incidence path will change. Therefore, the course of the isoenergy layer changes within one respiratory cycle.

  This is schematically shown in FIG. 2 based on three isoenergetic layer pairs 15A, 15B, 15C in different motion states. If these layers are irradiated, for example, at successive time intervals, the dose distribution will be non-uniform based on the partial overlap or lack of closeness (ie, the presence of gaps) of deformed isoenergetic layers in the target volume 13. Arise. Schematically, FIG. 2 depicts a symmetrical illumination volume 17 having a size of, for example, 3 mm in the lateral and Z directions in the isoenergy layer 15A. The size of the target volume 13 in the Z direction is, for example, eight equal energy layer thicknesses. In this case, in order to compensate for the motion shift, a safety region having the entire thickness of one isoenergetic layer is irradiated around the target volume 13 together.

  FIG. 3 is a clear explanation for FIG. 2, for example how an unirradiated region remains between the isoenergy layers 15A and 15B, and how the energy layers 15B and 15C are applied in duplicate. To show partial overlap for the given dose. This type of non-uniformity in the Z direction cannot be avoided by repeated (normal) rescanning.

  FIG. 4 shows how the irradiation volume 19 is divided into the target volume 13 by the expansion element. The expansion element has an irradiation volume 19 having a length that is four times longer in the Z direction than in the lateral direction, and thus has, for example, a length of 12 mm in the Z direction and a spread of 3 mm in the lateral direction. With this size of the irradiation volume 19, it is possible to irradiate the entire target volume with the two equal energy layers 21A, 21B in the time interval when the (breathing) movement is stopped. Therefore, there is no dose change during irradiation. This is because the entire target volume is irradiated at the same time at the same time.

  FIG. 5 shows how the irradiation of the entire target volume within one time interval does not cause non-uniformity due to motion. The boundary of the target volume 13 in which the inside surrounded by the safety region is uniformly irradiated by the equal energy layers 21A and 21B is recognized.

  For example, the feasible time interval for stopping breathing is preferably about 20 seconds, so if the number of isoenergetic layers is reduced to, for example, 1/4, a larger target volume as a whole can also be scanned.

  FIG. 6 shows a plurality of extensions that make it possible to reduce the size of the irradiation volume in the Z direction, for example in the edge range, in order not to create an unnecessarily large safety area around the target volume 13. Clarify the use of the element. For this purpose, an irradiation volume 23 extended twice is used instead of the irradiation volume 19 extended four times in the edge range. For this purpose, different expansion elements depending on the position are introduced into the beam or adjusted according to the acceleration / energy distribution.

  If the target volume 13 is irradiated as a whole many times by this method, a uniform dose distribution can be obtained over the target volume 13 for the particle beam therapy of the target moving in the scanning process.

Schematic diagram of particle beam device Schematic of irradiation volume arrangement according to the prior art Diagram showing dose distribution in the incident direction Schematic showing how the target volume is divided into the irradiation volume Diagram showing dose distribution in the incident direction belonging to FIG. Schematic showing how the target volume is divided into the irradiation volume using the expansion element

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Particle beam therapy apparatus 3 Previous stage accelerator 5 Synchrotron 7 Scanning apparatus 9 Setting apparatus 11 Control system 13 Target volume 15A, B, C Equal energy layer 17 Irradiation volume 19 Irradiation volume 21A, 21B Equal energy layer 23 Irradiation volume X, Y, Z direction

Claims (18)

In a particle beam therapy apparatus for particle beam therapy of a target volume exposed to motion in a patient,
A particle accelerator for supplying high energy particles;
A setting device for setting the size of the irradiation volume in which the particles interact with the tissue for treatment;
In order to control the setting device, a control signal for setting the three-dimensional size of the irradiation volume is output to the setting device so that the entire target volume can be irradiated during the time interval to stop or slow the movement. A control system configured in
A scanning device that is controllable so that the entire target volume can be scanned by the illumination volume within that time interval;
A particle beam therapy system comprising:   2. The particle beam therapy system according to claim 1, wherein the setting device has an adjustment device for adjusting the energy distribution of the particle beam that determines the size of the irradiation volume in the distal direction.   3. The particle beam therapy system according to claim 1, wherein the setting device has high energy beam guide means for adjusting the size of the particle beam in the lateral direction by the beam guide optical system.   4. The device according to claim 1, wherein the setting device is configured to set the size ratio of the distal and lateral directions of the irradiation volume equal to or greater than 2: 1. The particle beam therapy system described.   5. The setting device according to claim 1, wherein the setting device is configured to set the irradiation volume to a beam incident direction size having at least 10% of the distal size of the target volume. Particle beam therapy equipment.   6. The particle beam therapy system according to claim 1, wherein the setting device is configured to set the irradiation volume to a beam incident direction size within a range of 3 mm to 25 mm.   The particle beam therapy system according to one of claims 1 to 6, wherein the setting device is configured to set the irradiation volume to a lateral size within a range of 5 mm to 10 mm.   8. The particle beam therapy system according to claim 1, wherein the adjustment device is a degrader.   9. The particle beam therapy system according to claim 1, wherein the scanning device is a raster scanning device or a rocking device.   The particle beam therapy system according to claim 1, wherein the particle accelerator is configured to set energy for irradiating a plurality of energy layers within one time interval.   The particle beam therapy system according to any one of claims 1 to 10, further comprising energy setting means for irradiating a plurality of energy layers. Scanning for particle beam therapy where the particle volume interacts with the tissue for treatment to irradiate the target volume that is exposed to motion in the patient using the particle beam. In the method
Stop or delay the movement of the target volume for one time interval to create a quasi-static target volume;
Set the irradiation volume to a three-dimensional size that allows the entire volume to be irradiated during that time interval to be irradiated,
A scanning method for particle beam therapy, wherein the entire target volume to be irradiated is scanned by the irradiation volume within the time interval.   13. The scanning method according to claim 12, wherein a size ratio between the distal direction and the lateral direction of the irradiation volume is set equal to or larger than 2: 1.   The scanning method according to claim 12 or 13, wherein a distal direction size of the irradiation volume is one third or more of a distal direction size of the target volume.   15. The scanning method according to claim 12, wherein a distal direction size of the irradiation volume is in a range of 5 mm to 25 mm.   16. The scanning method according to claim 12, wherein the irradiation volume has a lateral size in a range of 3 mm to 10 mm.   17. A scanning method according to claim 12, wherein at least one energy layer having an irradiation volume is scanned to scan the entire target volume to be irradiated.   18. The scanning method according to claim 12, wherein the scanning method is a raster scanning method or a rocking method.

Images