Conformal particle beam therapy system

Abstract

A particle therapy system adapted to irradiate a target volume 1 with charged particles in accordance with a desired 3D dose distribution. Such desired 3D dose distribution is achieved while delivering multiple particle energy distributions at the output of an energy shaping device 10 that intersects with an incident monoenergetic charged particle beam 6. The energy shaping device comprises multiple groups 12, 22 of energy shaping elements 11, 21, each of which comprises an individual layer of fluid or solid material 13, the layer thicknesses of which are individually adapted by a control unit 14. The use of configurable layers of fluid or solid material allows the energy shaping device to be reused for treating different patients.

Description

Technical Field

[0001] The present invention relates to a charged particle therapy system.

[0002] More particularly, the present invention relates to a therapy system for irradiating a target volume within a patient with a charged particle beam, the therapy system comprising a charged particle beam generator, a beam transport system for transporting the charged particle beam, an irradiation device for delivering the charged particle beam to the target volume, and an energy shaping device installed so as to cross the path of the charged particle beam.

[0003] The energy shaping device comprises a plurality of energy shaping elements each designed to change the energy of the incident particles of a mono-energetic particle beam so that a mixture of different particle energies is delivered at their output to form a Spread-Out Bragg Peak (SOBP) in the corresponding region of the target volume, with the aim that the irradiation of the target volume more or less matches the 3D shape of the target volume.

Background Art

[0004] Charged particle therapy systems are well known in the art. Their function is to destroy unhealthy cells within a specific 3D region (hereinafter "target volume") of a living being (hereinafter "patient") by irradiating the target volume with a charged particle beam such as a proton beam, an ion beam. Currently, there are several irradiation techniques for irradiating a target with a particle beam. These techniques can be broadly classified into a scattering technique and a scanning technique. In the first classification, a wide scattered beam irradiates the entire target volume, and in the second classification, a narrow beam irradiates the target volume while scanning the target volume.

[0005] Regardless of the irradiation technique, the aim is always to reduce the unwanted irradiation of the patient's cells outside the target volume in both the lateral (X, Y) and depth (Z) directions. This aim is often referred to as "improvement of conformal irradiation".

[0006] Particularly for the purpose of improving conformal irradiation in the depth direction, several solutions have been proposed, such as arranging an energy shaping device (which may also be called an energy modulator) (e.g., a ridge filter, a range compensator, an energy selection system) in the path of the particle beam.

[0007] An example of a treatment system including such an energy modulator is disclosed in U.S. Patent Application No. 2018068753 (A1). According to such a known system, an energy modulator (referred to as a "ridge filter" in U.S. Patent Application No. 2018068753 (A1)) is installed to cross the beam path between the charged particle beam generator and the patient. A beam scattering device (sometimes called a "scatterer") upstream of the energy modulator scatters the particle beam on the surface of the energy modulator. The energy modulator is composed of a plurality of attenuation elements, and each attenuation element has a cross-sectional area that changes stepwise along the irradiation direction. When charged particles pass through such an attenuation element, a specific distribution of particle energy is generated at the output of the attenuation element, and this specific energy distribution produces a corresponding specific spread Bragg peak profile (SOBP) in the intersection region of the target volume when the target volume is irradiated by the particle beam through the attenuation element. As is well known, the distribution of particle energy at the output of the attenuation element depends on the material and shape of the attenuation element, more specifically, the various widths and heights of the staircase steps. The height of the staircase step determines the average particle energy at its output, while the width of the staircase step determines the particle ratio.

[0008] Such known energy modulators are custom-made for a given patient and a specific irradiation field, and thus cannot be reused for another patient or another beam orientation.

[0009] Another example of a known treatment system including such an energy modulator is disclosed in Korean Patent No. 101546656. According to such a known system, the energy modulator (referred to as a "variable compensator" in Korean Patent No. 101546656) is composed of a plurality of attenuation elements, and each attenuation element includes a column of fluid of a certain height extending in the irradiation direction. When charged particles pass through such an attenuation element, their energy decreases, thereby reducing the depth of the corresponding Bragg peak within the target volume in relation to the height of the fluid column. Further, the height of the fluid column of each attenuation element is individually controlled by a control unit, enabling the penetration depth of the charged particles of the irradiation beam to be adapted to the distal end of the target volume. However, such a known particle treatment system is not adapted to achieve a SOBP within the target volume.

[0010] Another example of a known treatment system including such an energy modulator is disclosed in U.S. Patent Application Publication No. 2008 / 0260098. Such a known energy modulator is similar to the modulator of Korean Patent No. 101546656 and is thus also intended to modulate the depth of the Bragg peak to match only the distal end of the target volume. When the beam irradiates the target along a single main beam direction, it is impossible or at least not configured to deliver a patient-specific planned SOBP to each 3D region of the target volume. Ultimately, an SOBP can be generated by irradiating the target along various main beam directions while varying the attenuation forces of various attenuation elements at multiple irradiation angles using such a system, but it is not clear from this document exactly how this can be achieved. In any case, the need to change the main beam direction and the attenuation forces of various attenuation elements during treatment increases the treatment time, which is undesirable. Further, with such an approach, due to the interdependence of the doses delivered at various irradiation angles, it is not possible to deliver a 3D conformal dose to the target with sufficient freedom.

Prior Art Documents

Patent Documents

[0011] [Patent Document 1] US Patent Application No. 2018068753(A1) [Patent Document 2] US Patent Application Publication No. 2008 / 0260098 [Patent Document 3] Korean Patent No. 101546656 [Summary of the Invention] [Problems to be Solved by the Invention]

[0012] Accordingly, an object of the present invention is to be adapted to irradiate a target volume in better conformity with a desired 3D dose distribution within the target volume and to be able to reuse or reconfigure an energy modulator for different patients and / or different irradiation fields, and to provide a treatment system. [Means for Solving the Problems]

[0013] For this purpose, the present invention is a treatment system for irradiating a target volume in a patient with a charged particle beam, - a charged particle beam generator, - a beam transport system for transporting the charged particle beam, - an irradiation device for delivering the charged particle beam to the target volume, - An energy shaping device installed to cross the path of a charged particle beam, wherein the energy shaping device is adapted to deliver a first desired particle energy distribution at the output of a first predefined group of energy shaping elements when crossing the particles of the charged particle beam, the first predefined group of adjacent energy shaping elements, and at least when crossing the particles of the charged particle beam, adapted to deliver a second desired particle energy distribution at the output of a second predefined group of energy shaping elements, the second predefined group of adjacent energy shaping elements, wherein the second desired particle energy distribution is different from the first desired particle energy distribution, an energy shaping device To provide a treatment system comprising.

[0014] Each energy shaping element of the first and second predefined groups of energy shaping elements comprises an individual layer of a fluid or solid material.

[0015] The treatment system is - When the irradiation device is oriented to deliver the particle beam to the target volume along a first main beam direction, adjusting the thickness of each fluid or solid material of each individual layer of the fluid or solid material of the energy shaping elements of the first predefined group of adjacent energy shaping elements to obtain the first desired particle energy distribution, - When the irradiation device is oriented to deliver the particle beam to the target volume along a first main beam direction, adjusting the thickness of each fluid or solid material of each individual layer of the fluid or solid material of the energy shaping elements of the second predefined group of adjacent energy shaping elements to obtain the second desired particle energy distribution Further comprising a control unit configured as such, wherein the thickness of each fluid or solid material is the thickness in the propagation direction of the charged particles of the charged particle beam.

[0016] In the context of the present invention, the "particle energy distribution in the output of a group of energy shaping elements" should generally be understood as a probability density function of particle energy, which gives, for each particle energy value, the ratio of the number of particles having said particle energy value in the output of the group of energy shaping elements to the total number of particles in the output of the group of energy shaping elements.

[0017] In the context of the present invention, a predefined group of adjacent energy shaping elements does not mean that such a group should be regarded as "any group of energy shaping elements", but rather a group of adjacent energy shaping elements that is clearly defined and known in advance to the control unit. A predefined group of adjacent energy shaping elements generally corresponds to a specific predefined region of the target volume, within which, when the target's predefined region is irradiated with a charged particle beam after the particles of the charged particle beam have intersected the energy shaping elements of the predefined group, a desired or planned dose distribution, and thus a desired or planned SOBP, is achieved. The desired or planned dose distribution may be obtained, for example, from a treatment planning system.

[0018] Unlike the system disclosed in U.S. Patent Application No. 2018068753 (A1), the treatment system according to the present invention can be reused for different target volumes by adjusting the thickness of the fluid or solid material according to the specific target volume to be treated.

[0019] Unlike the invention disclosed in Korean Patent No. 101546656, the treatment system according to the present invention is adapted to generate a specially planned SOBP in various 3D regions of the target volume, enabling better conformal irradiation using a single configurable device.

[0020] Unlike the system disclosed in U.S. Patent Application Publication No. 2008 / 0260098, the treatment system according to the present invention is adapted to generate a specially planned SOBP in various 3D regions of the target volume while the beam is directed towards the target volume along a single main beam direction, and is thus faster and more accurate.

[0021] Preferably, the control unit - The first desired particle energy distribution includes a first particle ratio (PRmin1) at a first minimum energy (Emin1) and a second particle ratio (PRmax1) at a first maximum energy (Emax1), - The second desired particle energy distribution includes a third particle ratio (PRmin2) at a second minimum energy (Emin2) and a fourth particle ratio (PRmax2) at a second maximum energy (Emax2) such that, and such that Emax1 is different from Emax2 configured. By using such a preferred treatment system, better irradiation conformity to the distal edge of the target volume can be achieved.

[0022] More preferably, the control unit is configured such that PRmax1 is different from PRmax2. By using such a preferred treatment system, even better irradiation conformity to the target volume can be achieved.

[0023] Preferably, the control unit is configured such that Emin1 is different from Emin2. By using such a preferred treatment system, better irradiation conformity to the proximal end of the target volume can be achieved.

[0024] Even more preferably, the control unit is configured such that PRmin1 is different from PRmin2. By using such a preferred treatment system, even better irradiation conformity to the target volume can be achieved.

[0025] Preferably, the control unit is configured such that (Emax1 - Emin1) is different from (Emax2 - Emin2). By using such a preferred treatment system, better irradiation conformity to the target volume can be achieved.

[0026] Preferably, each energy shaping element has a cylindrical surface. By using such a preferred treatment system, the energy shaping elements can be aligned close to each other, thus saving space and improving compactness.

[0027] More preferably, all the energy shaping elements have the same hexagonal cross-section, which enables the most compact energy shaping device.

[0028] Preferably, each energy shaping element is a tube that contains a fluid or a solid substance. By using such a preferred treatment system, the thickness of each layer of the fluid or solid substance can be easily adjusted by the control unit. Also, different energy shaping elements can hold different fluids or solid substances having different stopping powers.

[0029] Preferably, the fluid is a liquid. Exemplary liquids are furan (C4H4O) and a solution of glucose (C6H 12 O6). Preferably, the solid substance is a granular solid substance.

[0030] Preferably, the energy shaping elements are aligned in the propagation direction of the particles of the charged particle beam that intersects the energy shaping elements.

[0031] More preferably, each group of energy shaping elements is aligned with respect to the propagation direction of the particles of the incident charged particle beam.

[0032] Preferably, the treatment system comprises a beam scanner for scanning a charged particle beam over a target volume, and the spot size of the charged particle beam in front of the energy shaping device is substantially equal to the cross-section of adjacent energy shaping elements of a first predefined group and substantially equal to the cross-section of the energy shaping device of a second predefined group.

[0033] Alternatively, the energy shaping elements are arranged transversely to the propagation direction of the particles of the charged particle beam, preferably perpendicular to the propagation direction of the particles of the charged particle beam. By using such an alternative means, the energy shaping elements can be stacked so as to cross the propagation direction of the particles, and the number of stacked layers of the energy shaping elements, the respective orientation of each of those layers, the respective height and cross-section of each of those layers, and the fluid or solid material contained in those layers can be adapted to achieve a desired SOBP in the target volume.

[0034] Preferably, the charged particle beam generator is a cyclotron or a synchrotron. Preferably, the nominal beam energy at the output of the charged particle beam generator is in the range from 70 MeV to 250 MeV.

[0035] These and further aspects of the invention will be described in more detail by way of example with reference to the accompanying drawings.

Brief Description of the Drawings

[0036]

Figure 1

Figure 2a

Figure 2b

Figure 2c

Figure 3a

Figure 3b

Figure 3c

Figure 4

Figure 5a

Figure 5b

Figure 6

MODE FOR CARRYING OUT THE INVENTION

[0037] Unless otherwise indicated, the figures are not drawn to scale. Generally, the same components are indicated by the same reference numerals in the drawings.

[0038] Figure 1 shows a schematic view of an exemplary treatment system (100) according to the present invention. The system comprises a charged particle beam generator (3) (such as a cyclotron or a synchrotron, for example) for generating a typically mono-energetic beam of charged particles such as protons or carbon ions or any other type of ions. A typical beam energy delivered by the charged particle beam generator (3) is in the range, for example, from 70 MeV to 250 MeV. The system also comprises a beam transport system (4) for transporting the charged particle beam from the particle beam generator (3) to an irradiation device (5) (which may also be called a nozzle). The irradiation device (5) has a main beam axis (Z) (also called the main beam direction) and is adapted to deliver the charged particle beam (6) in a suitable form to a target volume (1) within a patient (not shown here). The system also comprises an energy shaping device (10) installed in the beam path between the generator (3) and the target volume (1). In this example, the energy shaping device (10) is installed in the beam path between the irradiation device (5) and the patient, but it may not be integrated with the irradiation device (5).

[0039] Such a treatment system may apply various target irradiation techniques such as beam scattering, beam wobbling, beam scanning, or other methods. The energy shaping device (10) is installed downstream of the device that performs the beam scattering, beam wobbling, or beam scanning. The irradiation device (5) may be attached to a gantry for rotation of the device about an isocenter, or it may be of a fixed beam line type or any other type. Such systems are well known in the art and will not be described in further detail accordingly.

[0040] Of particular interest here is the energy shaping device (10), which, when intersecting the particles of the charged particle beam (6), is adapted to deliver a first desired particle energy distribution at the output of a first predefined group (12) of energy shaping elements, the first predefined group (12) of adjacent energy shaping elements (11), and at least when intersecting the particles of the charged particle beam, a second desired particle energy distribution at the output of a second predefined group (22) of energy shaping elements, the second predefined group (22) of adjacent energy shaping elements (21), and the second desired particle energy distribution is different from the first desired particle energy distribution.

[0041] In this example, each energy shaping element includes an individual layer of a fluid (13) or solid material having a thickness. Preferably, the fluid is a liquid. Exemplary liquids are furan (C4H4O), and a solution of glucose (C6H 12 O6). Preferably, the solid material is a particulate or powdered material. Exemplary particulate solid materials are grains of polymethyl methacrylate (PMMA), grains of polystyrene, grains of Lexan, and grains of high density polyethylene.

[0042] The system is - adjusting the thickness of each fluid or solid material of each individual layer of the fluid or solid material (13) of the energy shaping elements (11) of the first predefined group (12) to obtain the first desired particle energy distribution when the irradiation device is oriented to deliver the particle beam to the target volume along a first main beam direction (the Z direction in FIG. 1), - adjusting the thickness of each fluid or solid material of each individual layer of the fluid or solid material (13) of the energy shaping elements (21) of the second predefined group (22) to obtain the second desired particle energy distribution when the irradiation device is oriented to deliver the particle beam to the target volume along the first main beam direction (the same Z direction in FIG. 1) further comprises a control unit (14) configured as such.

[0043] In the context of the present invention, the thickness of each fluid or solid substance is the thickness of the fluid or solid substance in the propagation direction of the charged particles.

[0044] The thickness of each fluid or solid substance of each individual layer of the fluid or solid substances of the first predefined group of the energy shaping element is adjusted by the control unit according to a first desired spatial dose distribution in a first region of the target volume (1) irradiated by the charged particles outputting the first predefined group of the energy shaping element. The desired first spatial dose distribution is, for example, the dose distribution defined by a treatment plan for the first region of the target volume (1).

[0045] The thickness of each fluid or solid substance of each individual layer of the fluid or solid substances of the second predefined group of the energy shaping element is adjusted by the control unit according to a second desired spatial dose distribution in a second region of the target volume (1) irradiated by the charged particles outputting the second predefined group of the energy shaping element. The desired second spatial dose distribution is, for example, the dose distribution defined by a treatment plan for the second region of the target volume (1).

[0046] Preferably, the control unit (14) adjusts the thickness of each fluid or solid substance of each individual layer of the fluid or solid substances of the first and second predefined groups of the energy shaping element before the particle beam (6) is turned on.

[0047] In the example of FIG. 1, the energy shaping elements (11, 21) of the first and second predetermined groups (12, 22) are cylindrical tubes oriented in the Z direction and are at least partially filled with a solid substance such as a liquid or a granular solid substance.

[0048] However, while the irradiation device is oriented to deliver a particle beam to the target volume along a first main beam direction (the Z direction in FIG. 1), as long as the thickness of such a layer of fluid or solid material (in the direction of propagation of the charged particles) is adjusted by the control unit (14) for the purpose of achieving a desired particle energy distribution at the output of a first predefined group (12) of adjacent energy shaping elements (11) and at the output of a second predefined group (22) of adjacent energy shaping elements (21), any other embodiment in which a layer of fluid or solid material is arranged to cross the path of the charged particles also conforms.

[0049] By using such a cylindrical tube oriented in the Z direction (or along the propagation direction of the charged particles intersecting the tube) as an energy shaping element, for example, by using a piston installed in the tube to separate a liquid from a gas such as air, the thickness of the liquid in a specific tube can be adjusted. In this example, the first piston moves inside the tube according to the pressures of the liquid and gas on both sides of the first piston until the equilibrium of their respective pressures is achieved. The liquid and gas can be held in dedicated tanks respectively, each tank is fluid-connected to both ends of the tube respectively, and their respective pressures are adjusted by a control unit (14), for example, by moving a second piston in the liquid tank. For example, a stepper motor acting on the second piston via a shaft can be used to move the piston in the liquid tank back and forth, and each step of the motor ultimately leads to a change in the thickness of the liquid in the tube. The liquid tank can be, for example, a syringe, and the stepper motor is connected to the piston of the syringe. The connection between the end of the tube and the tank is adapted such that the tank is outside the path of the particle beam. The connection can be shaped, for example, as an elbow with a 90° bend and can have a length sufficient to place the tank outside the path of the particle beam. In this example, all tubes are equipped in the same way, and the lengths of various connections are adapted to correspond to the number of tubes, and their stepper motors are individually controlled by the control unit (14) respectively. A similar system can be used to adjust the thickness of the granular solid material in the tube instead of the liquid.

[0050] Figure 2a shows a 3D view of the energy shaping device (10) of FIG. 1, and FIG. 2b shows a cross-sectional view of the energy shaping device (10) of FIG. 1 in a plane (XY) perpendicular to the main beam axis (Z). These figures illustrate a first predefined group (12) of adjacent energy shaping elements (11) and a second predefined group (22) of adjacent energy shaping elements (21). In these figures, the energy shaping elements (11, 21) are tubes aligned with the Z-axis having various cross-sections. The number of such tubes and their respective cross-sections in each group (12, 22) of adjacent energy shaping elements are selected according to the particle energy distribution to be achieved at the output of that group of adjacent energy shaping elements.

[0051] The number of tubes belonging to a given group (12, 22) of adjacent energy shaping elements, and their respective cross-sections, must be selected so as to achieve a desired SOBP between the front end and the distal end of the target volume (1) along the path of the charged particles output by that given group of adjacent energy forming elements.

[0052] In an exemplary case where each tube of a given group of energy shaping elements is filled with the same liquid or the same solid material of different thicknesses by a control unit, each tube of that given group of adjacent energy shaping elements outputs charged particles of different energies, and each energy is at the origin of a specific Bragg curve (and Bragg peak) of the desired SOBP within the target volume. The proportion of charged particles of a specific energy output by the first predefined group (12) of adjacent energy shaping elements is approximately proportional to the cross-section of the tubes belonging to that given group (12) of adjacent energy shaping elements, the thickness of the fluid or solid material of which has been adjusted by the control unit (14) to output charged particles of that specific energy.

[0053] The control unit (14) converts the desired / planned particle energy distribution at the output of a given group of adjacent energy shaping elements into the thicknesses of the individual liquids or solid materials, and accordingly fills the various energy shaping elements of that group.

[0054] The number of tubes within the first or second predefined group of energy shaping elements and their respective cross-sections must conform to the diameter of the corresponding cylindrical sub-volume to be irradiated within the target volume, as defined, for example, by said treatment plan (spatial dose distribution). In fact, the overall cross-section of the first predefined group (12) of energy shaping elements must conform as closely as possible to the cross-section of said corresponding cylindrical sub-volume within the target volume. Naturally, the same applies to the second predefined group (22) of adjacent energy shaping elements.

[0055] In the case of pencil beam scanning (PBS), the overall cross-section of the first predefined group (11) of adjacent energy shaping elements, as well as the size and shape of the PBS spots at the input of said first predefined group (11) of adjacent energy shaping elements, must conform as closely as possible. Naturally, the same applies to the second predefined group (22) of adjacent energy shaping elements.

[0056] In these examples, each tube (11, 21) has a diameter, for example, between 2 mm and 10 mm, the first predefined group of tubes includes, for example, 5 to 15 tubes (11), and the second predefined group of tubes includes, for example, 5 to 15 tubes (21).

[0057] Figure 2c shows a cross-sectional view in the XY plane of a preferred energy shaping device of a treatment system according to the invention. In such a preferred embodiment, all the energy shaping elements (11, 21) are tubes of the same hexagonal cross-section arranged in a honeycomb pattern.

[0058] Such an energy shaping device (10) is specifically designed to reduce the energy of the incident charged particles, so that a desired particle energy distribution exists at the output of the predefined group of adjacent energy shaping elements.

[0059] When charged particles that output a given group of adjacent energy-forming elements enter the target volume (1), several Bragg peaks are generated in the corresponding region of the target volume (1), and their combination results in a so-called "spread-out Bragg peak" (SOBP). The functions and basic operations of such energy shaping devices themselves are well known in the art and will not be described further herein.

[0060] Figure 3a shows a view during the operation of the treatment system (100) of FIG. 1, i.e., after the control unit (14) adjusts the thickness of each fluid or solid material of each individual layer of the energy shaping elements of the first predetermined group (12) of energy shaping elements to obtain the first desired particle energy distribution, adjusts the thickness of each fluid or solid material of each individual layer of the energy shaping elements of the second predefined group (22) of energy shaping elements to obtain the second desired particle energy distribution, and while the charged particle beam irradiates the target volume (1) along the first direction (the Z direction in FIG. 3a).

[0061] Figure 3a shows in more detail a cross-section in the XZ plane of a specific target volume (1) and a corresponding cross-section in the same XZ plane of an energy shaping device (10). In this XZ plane, the charged particles of the particle beam (6) can proceed in a first beam direction (Z1x) that cuts through a first region of the target volume (1) delimited by depths, for example, by two first points (A1x, B1x). These charged particles intersect a first predefined group (12) of adjacent energy shaping elements (11), creating a first SOBP (SOBP-Z1x) within the target volume (1) as these charged particles proceed in the first beam direction (Z1x), and the profile of this first SOBP (SOBP-Z1x) (essentially the position of the width, height, and depth) substantially corresponds to the desired dose distribution in the first region. The graph of Figure 3b shows the desired dose profile and the desired first SOBP (SOBP-Z1x) along the first beam direction (Z1x), where the horizontal axis Zix represents a beam direction such as Z1x or Z2x. The same applies to the charged particles proceeding in a second beam direction (Z2x).

[0062] Figure 3c shows the corresponding desired first distribution of particle energies created at the output of a first predefined group (12) of adjacent energy shaping elements (11), where the horizontal axis shows the particle energy (E) represented by the average value within the range on a scale (scale) marked with graduations in a straight line, and the vertical axis shows the ratio of the number of particles having the average particle energy at the output of the first predefined group (12) of adjacent energy shaping elements (11) to the total number of particles intersecting the first predefined group (12) of adjacent energy shaping elements (11).

[0063] As shown in Figure 3c, the first energy distribution includes a first particle ratio (PRmin1) at a first minimum energy (Emin1) and a second particle ratio (PRmax1) at a first maximum energy (Emax1). The first minimum energy (Emin1) and the first maximum energy (Emax1) respectively correspond to the depth of the first point (A1x) and the depth of the second point (B1x) in the target volume (1).

[0064] From this desired first distribution of particle energy, a specific thickness of the layer of fluid or solid material of the first predefined group (12) of adjacent energy shaping elements (11) is calculated according to known methods and can then be set by the control unit before the irradiation of the target volume is started.

[0065] Figures 3a, 3b, and 3c also show a second predefined group (22) of adjacent energy shaping elements (21), the corresponding desired dose profile and SOBP (SOBP-Z2x)) when the particles of the particle beam (6) travel in a second beam direction (Z2x) in the XZ plane, and the desired second desired particle energy distribution. As can be seen from Figure 3c, the second desired particle energy distribution includes a third particle ratio (PRmin2) at a second minimum energy (Emin2) and a fourth particle ratio (PRmax2) at a second maximum energy (Emax2). The second minimum energy (Emin2) and the second maximum energy (Emax2) respectively correspond to the depth of another first point (A2x) and the depth of another second point (B2x) in the target volume (1).

[0066] Similarly, from this desired second distribution of particle energy, a specific thickness of the layer of fluid or solid material of the second predefined group (22) of adjacent energy shaping elements is calculated according to known methods and can then be set by the control unit before the irradiation of the target volume is started.

[0067] Furthermore, as is further understood, the filtering effect of several adjacent energy shaping elements filled with the same fluid or solid material of the same height is more or less equivalent to the filtering effect of a single energy shaping element of a larger cross-section (i.e., the cross-section multiplied by the number of tubes) filled with the same fluid or solid material of the same height.

[0068] As can be seen from FIG. 3c, the control unit is preferably configured to adjust the thickness of each fluid or solid material layer of the fluid or solid material of the energy shaping element of the first predefined group (12) such that Emax1 is different from Emax2, preferably such that PRmax1 is different from PRmax2 in a similar manner, preferably such that Emin1 is different from Emin2 in a similar manner, preferably such that PRmin1 is different from PRmin2 in a similar manner, and preferably such that (Emax1 - Emin1) is different from (Emax2 - Emin2), and to adjust the thickness of each fluid or solid material layer of the fluid or solid material of the energy shaping element of the second predefined group (22). By using such an ability, good conformal irradiation of the target volume can be obtained.

[0069] Such a desired particle energy distribution can be achieved, for example, while the particle beam (6) is being scanned on the energy shaping device (10) after the control unit (14) has adjusted the thickness of each fluid or solid material layer of the fluid or solid material of the energy shaping element to achieve the desired particle energy distribution.

[0070] In such a case, the treatment system preferably comprises a beam scanner for scanning a charged particle beam on the energy shaping device. Such a beam scanner is well known in the art and can comprise, for example, electromagnets installed around the beam line for deflecting the particle beam (6) in the X and Y directions. Thus, when scanning a particle beam (6) having a fixed energy, for example, on the energy shaping device (10), preferably in a single scan, i.e., with the particle beam passing through each predefined group of energy shaping elements only once, good depth conformal irradiation of the target volume can be achieved.

[0071] For example, in cases where the treatment system scans the beam, such as when using the known pencil beam scanning (PBS) technique, the energy shaping elements are sized such that the spot size of the charged particle beam (6) in front of the energy shaping device (10) is substantially equal to the cross-section of a first predefined group (12) and substantially equal to the cross-section of a second predefined group (22) of adjacent energy shaping elements (21).

[0072] Such a desired particle energy distribution can also be achieved by scattering the charged particle beam one or two times before the charged particle beam reaches the energy shaping device. In such an embodiment, the beam is scattered such that substantially all predefined groups of energy shaping elements intersect the scattered charged particles. Optionally, a final collimator may be used to ensure that the scattered beam coincides with the lateral boundaries of the target volume (1).

[0073] FIG. 4 shows three predefined groups (12, 22, 32) of adjacent energy shaping elements (11, 21, 31) according to an exemplary embodiment of the present invention, and each predefined group (12, 22, 32) of energy shaping elements is aligned with the propagation direction (Z1x, Z2x, Z3x) of the particles of the incident particle beam (6). Preferably, all energy shaping elements of a given predefined group (12, 22, 32) are aligned with the propagation direction (Z1x, Z2x, Z3x) of the incident particle beam (6). In such a preferred embodiment, the incident charged particles intersect only a single energy shaping element. For example, such an embodiment can be used in combination with a scanned incident method, in which case each predefined group (12, 22, 32) of adjacent energy shaping elements is arranged and aligned in the propagation direction (Z1x, Z2x, Z3x) of the incident scanned beam, respectively.

[0074] In the case of pencil beam scanning (PBS), as shown in Figure 4, the overall cross-section of each predefined group of adjacent energy shaping elements (12) should preferably match as closely as possible the size of the PBS spot (60) at the input of each of said predefined groups of adjacent energy shaping elements.

[0075] Figure 4 shows an energy shaping element that is a tube with a hexagonal cross-section. However, the cross-section of the tube can be of any shape and each cross-section of the tube can be changed.

[0076] Figure 5a shows an alternative embodiment of a treatment system (100) according to the present invention. This is similar to the treatment system described above, but the difference is that, as shown in Figure 5a using an XYZ reference axis with Z as the main beam direction, here the energy shaping element (11) is arranged transversely, preferably perpendicular, to the propagation direction of the particles of the charged particle beam.

[0077] In this example, the energy shaping element (11) is a tube with a rectangular cross-section arranged adjacent to each other in stacked layers, and each layer is in a plane perpendicular to the main propagation direction (Z) of the particles of the charged particle beam (in Figure 5a, the main propagation direction (Z) of the particle beam is perpendicular or inclined to the plane of the sheet). Each layer of the tube has a different height and also has a different orientation within its plane. Figure 5a shows an embodiment including four layers (35a, 35b, 35c, 35d), but any number of layers is possible. Also, the cross-section of the tube may have a shape other than rectangular. Each tube (11) is individually controlled by a control unit (14) according to the same or similar criteria as described above for a fluid, preferably, for example, furan (C4H4O) or glucose (C6H 12It can be filled with a liquid such as a solution of O6), or with a solid substance such as a granular solid substance, or left empty. Also, the type of fluid or solid substance can be different for each tube. According to such an embodiment, a predefined group of adjacent energy shaping elements includes one or more tubes from a plurality of layers. Figure 5a highlights such an exemplary selection of adjacent energy shaping elements of the first predefined group with their bold boundaries. The layers of tubes are oriented and arranged such that adjacent energy shaping elements define a stack of fluids or solid substances of different cross-sections, as highlighted by the dashed circle (40) in Figure 5a. These cross-sections are shown in Figure 5b, where seven stacks (41 to 47) of fluids or solid substances with different cross-sections and different stopping powers can be seen. When the treatment system includes a scanner for scanning a particle beam over the energy shaping device (10), the area of the dashed circle (40) preferably substantially corresponds to the spot size of the particle beam at this position.

[0078] More generally, the energy shaping elements of a predefined group are individually arranged for the purpose of defining various stacks of layers of fluid or solid substances along the path of the incident charged particles, each fluid or solid substance being characterized in that its stopping power may vary in some cases, and each stack being characterized in that the area intersecting the incident charged particle beam may be different. Thus, each stack of layers of fluid or solid substances outputs particles of a given energy (or an energy within a range of the same width as the range of the incident particle beam), and the proportion of incident charged particles having that given energy (or energies) depends on the intersection area of the stack of layers of fluid or solid substances (i.e., the area intersecting the charged particles of the incident charged particle beam). In the case of the embodiments shown in Figures 5a and 5b, each stack of layers of fluid or solid substances is made of tubes, and the intersection area is the cross-section of the tubes.

[0079] In the case where the energy shaping element is arranged transversely to the particle propagation direction of the charged particle beam, the energy shaping element (11) may alternatively be a simple rod of solid material instead of a tube filled with a fluid or solid material.

[0080] Therefore, what has been described above and shown in FIGS. 5a and 5b also applies when the energy shaping element is a simple rod of solid material. The geometrical considerations remain valid and by appropriately selecting the solid material involved, the stopping power of the laminate of layers of solid material can be adapted. Such solid materials can be, for example, different types of plastics such as polymethyl methacrylate (PMMA), polystyrene, Lexan, high density polyethylene, or metals such as brass or tungsten. Unlike fluids, solid materials offer the possibility of mixing multiple materials in any single energy shaping element. More precisely, as shown in FIG. 6, various solid materials can be included in the energy shaping element (11) adjacent to each other. In FIG. 6, such an energy shaping element (11) is a hollow tube. In the example of FIG. 6, three different solid materials (51, 52, 53) are present, each occupying a part of the hollow tube (11). Specifically, each energy shaping element (11) can include an individual number of solid materials (51, 52, 53), and the position of the boundary between the various solid materials can also be selected individually. Such a configuration increases the degree of freedom for achieving conformal irradiation.

[0081] An energy shaping element made of a simple rod of solid material can be moved by a control unit in a suitable treatment configuration, for example, in a manner similar to a multi-leaf collimator, i.e., by a stepper motor that moves the rod back and forth transversely at each treatment position.

[0082] An energy shaping element made of a tube filled with a solid material can be arranged in a suitable treatment configuration by a control unit, for example, by controlling a stepper motor that pushes a rod of solid material in the tube from one end or the other end of each tube.

[0083] Although the present invention has been described with respect to specific embodiments, these are illustrative of the present invention and should not be construed as limiting. The reference numbers in the claims do not limit the scope of protection. The use of verbs such as "comprising", "including", "consisting of" or any other variations and their respective conjugations does not exclude the presence of elements other than those described. The use of the articles "a", "an" or "the" before an element does not exclude the presence of a plurality of such elements.

[0084] The present invention can also be described as follows: A particle therapy system adapted to irradiate a target volume (1) with charged particles in accordance with a desired 3D dose distribution. Such a desired 3D dose distribution is achieved while delivering a plurality of particle energy distributions at the output of an energy shaping device (10) that intersects an incident mono-energetic charged particle beam (6). The energy shaping device includes a plurality of predefined groups (12, 22) of energy shaping elements (11, 21), each energy shaping element of each group including an individual layer of a fluid or solid material (13), the thickness of the fluid or solid material (13) being individually adapted by a control unit (14) prior to irradiation in order to obtain the desired 3D dose distribution while the target volume is being irradiated along a single main beam direction (Z).

Claims

1. A treatment system for irradiating a target volume within a patient, the treatment system comprising: - a charged particle beam generator; - a beam transport system for transporting the charged particle beam; - an irradiation device for delivering the charged particle beam to the target volume; - an energy shaping device disposed to cross the path of the charged particle beam wherein the energy shaping device comprises a first predefined group of energy shaping elements composed of a plurality of adjacent energy shaping elements, the first predefined group of energy shaping elements being adapted to deliver a first desired particle energy distribution at the output of the first predefined group of energy shaping elements when intersecting the particles of the charged particle beam; at least one second predefined group of energy shaping elements composed of a plurality of adjacent energy shaping elements, the second predefined group of energy shaping elements being adapted to deliver a second desired particle energy distribution at the output of the second predefined group of energy shaping elements when intersecting the particles of the charged particle beam wherein the second desired particle energy distribution is different from the first desired particle energy distribution; - each energy shaping element of each of the first and second predefined groups of energy shaping elements comprises an individual layer of fluid or solid material; - the treatment system is configured to - adjust the thickness of each individual layer of fluid or solid material of the energy shaping elements of the first predefined group of energy shaping elements to obtain the first desired particle energy distribution when the irradiation device is oriented to deliver the particle beam to the target volume along a first main beam direction; - adjust the thickness of each individual layer of fluid or solid material of the energy shaping elements of the second predefined group of energy shaping elements to obtain the second desired particle energy distribution when the irradiation device is oriented to deliver the particle beam to the target volume along the first main beam direction further comprising a control unit configured as such, A treatment system, wherein the thickness of each fluid or solid substance is the thickness in the propagation direction of the charged particles of the charged particle beam. **Claim 2** - The first desired particle energy distribution includes a first particle ratio (PRmin1) at a first minimum energy (Emin1) and a second particle ratio (PRmax1) at a first maximum energy (Emax1), - The second desired particle energy distribution includes a third particle ratio (PRmin2) at a second minimum energy (Emin2) and a fourth particle ratio (PRmax2) at a second maximum energy (Emax2), The treatment system according to claim 1, wherein Emax1 is different from Emax2. **Claim 3** The treatment system according to claim 2, wherein PRmax1 is different from PRmax2. **Claim 4** The treatment system according to claim 2, wherein Emin1 is different from Emin2. **Claim 5** The treatment system according to claim 4, wherein PRmin1 is different from PRmin2. **Claim 6** The treatment system according to claim 2, wherein (Emax1 - Emin1) is different from (Emax2 - Emin2). **Claim 7** The treatment system according to claim 1, wherein each energy shaping element has a cylindrical surface. **Claim 8** The treatment system according to claim 7, wherein all energy shaping elements have the same hexagonal cross-section. **Claim 9** The treatment system according to claim 1, wherein each energy shaping element is a tube for containing the fluid or the solid substance. **Claim 10** The treatment system according to claim 1, wherein the energy shaping element is aligned with the propagation direction of the particles of the charged particle beam that intersects the energy shaping element. **Claim 11** The treatment system according to claim 1, wherein each group of energy shaping elements is aligned with the propagation direction (Z1x, Z2x, Z3x) of the particles of the incident particle beam. **Claim 12** The treatment system includes a beam scanner for scanning the charged particle beam over the target volume, and the spot size of the charged particle beam in front of the energy shaping device is substantially equal to the cross-section of the first predefined group of energy shaping elements and substantially equal to the cross-section of the second predefined group of energy shaping elements. The treatment system according to claim 1. **Claim 13** The treatment system according to claim 1, wherein the energy shaping element is arranged transversely to the propagation direction of the particles of the charged particle beam.

14. The treatment system according to claim 1, wherein the charged particle beam generator is a cyclotron or a synchrotron.

15. The treatment system according to claim 14, wherein the nominal beam energy at the output of the charged particle beam generator is in the range from 70 MeV to 250 MeV.

16. The treatment system according to claim 13, wherein the energy shaping element is arranged perpendicular to the propagation direction of the particles of the charged particle beam.

17. The first predefined group of energy shaping elements corresponds to a first predefined region of the target volume, and within the first predefined region, when the particles of the charged particle beam are directed towards the first predefined region of the target volume, a first desired or planned dose distribution and a first desired or planned spread-out Bragg peak (SOBP) are achieved. The treatment system according to claim 1, wherein the second predefined group of energy shaping elements corresponds to a second predefined region of the target volume, and within the second predefined region, when the particles of the charged particle beam are directed towards the second predefined region of the target volume, a second desired or planned dose distribution and a second desired or planned SOBP are achieved.

18. The control unit is configured to obtain a first desired or planned spread-out Bragg peak (SOBP) in the target volume based on adjustment of the thickness of each fluid or solid material layer of the energy shaping elements of the first predefined group of energy shaping elements, and configured to obtain a second desired or planned SOBP in the target volume based on adjustment of the thickness of each fluid or solid material layer of the energy shaping elements of the second predefined group of energy shaping elements. The treatment system according to claim 1.

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