BEAM TRANSPORT LINE FOR RADIOTHERAPY SYSTEMS AND RADIOTHERAPY SYSTEM THEREOF

Abstract

Disclosed is a knuckle boom crane for offshore application, wherein the crane includes a knuckle boom, carried by a support structure and equipped with an operating unit. The knuckle boom includes a main boom and a terminal boom. The operating unit of the knuckle boom include at least one downstream linear actuator, arranged between the main boom and the terminal boom, for the rotational operation of the terminal boom about a downstream articulation axis. And the at least one downstream linear actuator is fastened to one of the lateral faces of the main boom and to one of the lateral faces of the terminal boom, in order to provide an improved lever arm between the main boom and the terminal boom.

Claims

1. A beam transport line for a proton accelerator, arranged to guide the proton beam from the accelerator to a dose delivery system, wherein the accelerator, the proton beam transport line and the dose delivery system are arranged to be controllable by a control system, and wherein the beam transport line comprises a plurality of electromagnetic elements, wherein at least one of these electromagnetic elements is connected to either a 2-quadrant or a 4-quadrant power supply unit arranged to produce a current that can be varied by the control system in less than 50 milliseconds so that, when the beam energy is varied to move the beam spot along the beam direction, the beam is kept focused on a target with losses along the beam transport line and the dose delivery system not larger than 10% and variations of the transverse Full Widths at Half Maximum of the beam spot not larger than 10%.

2. (canceled)

3. The beam transport line according to claim 1, wherein the accelerator is an ion linac.

4. The beam transport line according to claim 1, wherein the accelerator is an ion synchrotron, either superconducting or at room temperature.

5. The beam transport line according to claim 1, wherein the accelerator is either a cyclotron or a synchrocyclotron.

6. A radiotherapy system comprising the beam transport line of claim 1.

7. A radiation therapy system, comprising a particle accelerator adapted to emit a particle beam, said particle beam being a beam of protons or a beam of ions with an electric charge between 2 and 10 and a mass number between 4 and 20, a beam transport line comprising a plurality of electromagnetic elements to guide the particles beam from the accelerator, a control system operatively connected to the accelerator to vary the energy of the particle beam, wherein at least one of the electromagnetic elements is connected to either a 2-quadrant or a 4-quadrant power supply unit arranged to produce a current that can be varied by the control system in less than 50 milliseconds so that, when the beam energy is varied to move the beam spot along the beam direction, the beam is kept focused on a target with losses along the beam transport line and the dose delivery system not larger than 10% and variations of the transverse Full Widths at Half Maximum of the beam spot not larger than 10%.

8. The system according to claim 7, further comprising a dose distribution system, wherein the beam transport line is adapted to guide the particles beam from the accelerator to the dose distribution system.

9. The radiotherapy system according to claim 7, wherein the control system is adapted to vary the accelerator energy every 2-10 milliseconds and to control the beam transport line and the dose distribution system with a frequency of 100-500 Hz.

10. The radiotherapy system according to claim 7, wherein the accelerator is a linac for ions.

11. The radiotherapy system according to claim 8, wherein the control system is adapted to vary the accelerator energy every 2-10 milliseconds and to control the beam transport line and the dose distribution system with a frequency of 100-500 Hz.

12. The radiotherapy system according to claim 8, wherein the accelerator is a linac for ions.

13. The radiotherapy system according to claim 9, wherein the accelerator is a linac for ions.

14. A beam transport line for an accelerator of ions, having electric charge Z between 2 and 10 and mass number A between 4 and 20, arranged to guide the ion beam from the accelerator to a dose delivery system, wherein the accelerator, the beam transport line and the dose delivery system are arranged to be controllable by a control system, and wherein the beam transport line comprises a plurality of electromagnetic elements, wherein at least one of these electromagnetic elements is connected to either a 2-quadrant or a 4-quadrant power supply unit arranged to produce a current that can be varied by the control system in less than 50 milliseconds so that, when the beam energy is varied to move the beam spot along the beam direction, the beam is kept focused on a target with losses along the beam transport line and the dose delivery system not larger than 10% and variations of the transverse Full Widths at Half Maximum of the beam spot not larger than 10%.

15. The beam transport line according to claim 14, wherein the accelerator is an ion linac.

16. The beam transport line according to claim 14, wherein the accelerator is an ion synchrotron, either superconducting or at room temperature.

17. The beam transport line according to claim 14, wherein the accelerator is either a cyclotron or a synchrocyclotron.

18. A radiotherapy system comprising the beam transport line of claim 14.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0058] Further features and advantages of the present invention will be clearer from the following detailed description of some preferred embodiments, which is made with reference to the annexed drawings.

[0059] The different characteristics described with reference to the individual embodiments can be combined as desired, if one would like to make use of advantages resulting specifically from a particular combination.

[0060] In these drawings,

[0061] FIG. 1 illustrates a beam transport line according to an embodiment of the present invention;

[0062] FIG. 2 illustrates a variant of the beam transport line of FIG. 1;

[0063] FIG. 3 schematically illustrates a target in water and a known method of controlling a beam of protons and other light ions for depositing a dose of protons on the target.

DETAILED DESCRIPTION OF THE INVENTION

[0064] In the following description, identical reference numbers or symbols are used to illustrate the figures to indicate components with the same function. In addition, for clarity of illustration, some references may not be repeated in all figures.

[0065] While the invention is susceptible of various modifications and alternative constructions, some preferred embodiments are shown in the drawings and will be described in details herein below. It should be understood, however, that there is no intention to limit the invention to the specific disclosed embodiment but, on the contrary, the invention intends to cover all the modifications, alternative constructions and equivalents that fall within the scope of the invention as defined in the claims.

[0066] The use of “for example”, “etc.”, “or” denotes non-exclusive alternatives without limitation, unless otherwise noted. The use of “includes” means “includes, but not limited to”, unless otherwise noted.

[0067] In the following beam transport lines (also called “beamlines” and “magnetic channels”) are disclosed which comprise electric and magnetic elements as bending magnets and quadrupoles, which connect an accelerator of protons and other ions to a Dose Delivery System (DDS) for therapeutic and palliative purposes for treating tumours, and other pathologies which benefit from radiotherapy, for example arteriovenous and other localized arterial malformations, cardiac arrhythmias, renal denervation etc. The magnetic elements are typically electromagnets.

[0068] The beam transport line may be part of a gantry or may be a fixed beam transport line.

[0069] Some of the beam transport line magnetic elements, for example dipoles or quadrupoles, are connected to rapidly varying power supplies, in particular rapidly varying 2-quadrant and/or 4-quadrant power supplies, so that the proton beam is transported and kept focused when, in less than 50 ms, in particular in the range between 0.1 ms and 50 ms, the energy of the beam is decreased or increased. The current change may be within a fractional interval that goes from about ±1% to about ±10% of their values, but this interval may also increase. The rapid variation of the energy implies that the beam spot can be moved, in less than 50 milliseconds, back and forth by many millimetres, and even centimetres.

[0070] This feature is particularly important when a monitoring device detects in real time the 3-dimensional movements of the target in the patient body (due to respiration, heart beating and other body movements) and the Control System of the accelerator-beamline-DDS Complex applies a 3-dimensional feedback system to follow the target, without interrupting the irradiation, thus performing what can be called a “Fast Adaptive Spot Scanning Therapy”—FASST. The invention here disclosed is relevant for the more advanced technique of irradiating moving targets called “tumour tracking”. It can also be used to correct the beam spot position in case of a sudden movement of the patient.

[0071] In the following, therefore, will be described beamlines—which guide the particles from a proton-beam or other ions-beam therapy accelerator to a DDS—in which at least one magnetic element is connected to either a 2-quadrant or a 4-quadrant power supply producing in the element a current, i.e. a magnetic field, that can be varied by the control system in less than about 50 milliseconds. For achieving such short times, the inductances of the powered coils are matched to the needs.

[0072] These beam transport lines have preferred application to accelerators that can rapidly vary the energy of the beam spot—i.e. rapidly vary the position of the Bragg peak inside the target—and is of particular advantage when a target position-measuring device detects, during an irradiation, the necessity of a longitudinal adjustment of the range (i.e. of the energy) of the beam. A longitudinal feedback system, known per se and therefore not described, is preferably combined with a transverse 2-dimensional feedback system and transforms it into a fully “3-dimensional feedback system”.

[0073] With reference to FIG. 1, a beam transport line 100 is illustrated that can connect a proton accelerator, in particular a linac (not shown in the figure) capable of emitting a beam with energy up to 230 MeV, to a dose distribution system 10.

[0074] The beam transport line 100 comprises a horizontal beam transport line 1 and a rotating beam transport line 3. The horizontal beam transport line 1 and the rotating beam transport line 3 are connected at a “coupling point” C.P., indicated by reference number 2.

[0075] At the coupling point, a fixed vacuum chamber of the horizontal beam transport line 1 is connected, by means of a gas-tight connection, to a rotating vacuum chamber of the rotating beam transport line 3.

[0076] In the example in FIG. 1, the horizontal beam transport line 1 comprises four quadrupoles QA, QB, QC and QD, designated by reference number 4, while the rotating beam transport line 3 comprises six quadrupoles Q1-Q6, designated by reference number 6, and four bending magnets BM1-BM4, designated by reference number 7.

[0077] In this example, quadrupoles 4 and 6 and bending magnets 7 of the beam transport line 100 are connected to 2-quadrant switch-mode power supply units (not shown) that can vary their currents by about ±10% in short times, i.e. about 2 milliseconds.

[0078] In other embodiments and for some magnets (in particular the quadrupoles) it may be convenient to use 4-quadrant switch-mode power supply units. The reason is that the magnetic fields of the bending magnets never reverse sign so that for them 2-quadrant switch mode power supply units are sufficient. Instead it could happen that, when varying the beam energy, the fields' direction in some quadrupoles have to be inverted; in such instances 4-quadrant switch mode power supply units are needed. This is not the case for the quadrupoles of the embodiment of FIG. 1.

[0079] According to a preferred embodiment, therefore, the main components of the system of FIG. 1, which transports protons with E(max)=230 MeV, are:

[0080] 1. an “horizontal beam transport line”, which is preferably, but not necessarily, 4 m long and guides the beam from the end of the proton linac to the coupling point C.P.;

[0081] 2. the “coupling point” C.P. between the fixed vacuum chamber and the rotating vacuum chamber;

[0082] 3. the “rotating beam transport line” (usually called “gantry”) which is about 8 m long, and its magnetic elements;

[0083] 4. the “standard quadrupoles” QA, QB, QC and QD forming the last part of the beamline;

[0084] 5. the “beam dump”;

[0085] 6. the “standard quadrupoles” Q1, Q2 . . . Q5 mounted on the rotating gantry;

[0086] 7. the “30-degree bending magnets” BM1 and BM2 with a maximum magnetic field B(max)=1.6 tesla;

[0087] 8. the “75-degree bending magnets” BM3 and BM4 with a maximum magnetic field B(max)=1.6 tesla;

[0088] 9. the “large-aperture quadrupole” Q6;

[0089] 10. the “Dose Distribution System” DDS;

[0090] 11. the “scanning magnet SMx” that bends the beam in the x-direction;

[0091] 12. the “scanning magnet SMy” that bends the beam in the y-direction;

[0092] 13. the “beam monitors”.

[0093] A simpler embodiment is shown in FIG. 2, where reference number 14 indicates an horizontal beam transport line and reference number 15 indicates an horizontal DDS. In the example of FIG. 2 the horizontal beam transport line comprises six quadrupoles QA, QB, QC, QD, QE and QF, while the DDS 15 comprises the two scanning magnets SMx and SMy, indicated with the references 11 and 12, and the beam monitors 13.

[0094] The embodiment of FIG. 1 provides small emittances of the proton beam emitted and therefore the magnets have small iron-to-iron gaps: 40 mm for the standard quadrupoles and 30 mm for the bending magnets. The magnets are much lighter than in other existing gantries. Moreover, they form an integral part of the supporting structure such that the overall weight of the gantry (with all its elements) is only about 25 tons. The whole system can be attached to the wall of the shielded treatment room.

[0095] The accelerator-beam transport line-DDS of FIG. 1 runs at a frequency comprised between 100 Hz and 500 Hz, preferably at 200 Hz, i.e. its energy can be varied every 2-10 milliseconds, preferably every 5 milliseconds. The control of variation of the beam energy is implemented by the control system (not shown in FIG. 1) which acts on the accelerator to vary the beam energy and thus adjust the longitudinal position of the beam-spot.

[0096] The maximum percentage variations of the magnetic fields in the bending magnets BM1, BM2, BM3, and BM4 have been computed from the above equation (eq. 1) by requiring that, at each energy, the depth of the Bragg peak can be moved back and forward by twice its width Wd. With the above approximate equation this means a maximum range variation

ΔR(max)=±24 mm (E/230).

[0097] This is achieved in a few milliseconds by varying the currents circulating in the coils of the deflecting magnets thanks to the 2-quadrant or 4-quadrant switched mode power supply units.

[0098] Table 1 below shows some simulations for the system of FIG. 1. In column C2 of Table 1 the energy corresponding to the ranges of column C1 are listed, according to the first equation quoted above. The needed maximum range variations ΔR(max) are listed in Column 4 of Table 1. The last column gives the maximum variations of the fields in the bending magnets that give the range adjustments ΔR(max) of Column 4.

TABLE-US-00001 TABLE 1 C3 C4 C1 C2 Max range Max energy C5 Range Energy step step Maximum R E ΔR(max) ΔE(max) field variation [mm] [MeV] [mm] [MeV] (ΔB/B) 40 69 ±7.20 ±6.72 ±5.11% 70 95 ±9.91 ±7.32 ±4.20% 100 116 ±12.1 ±7.63 ±3.62% 150 147 ±15.3 ±8.16 ±3.12% 200 172 ±18.0 ±8.38 ±2.76% 250 196 ±20.4 ±8.70 ±2.54% 300 217 ±22.6 ±8.88 ±2.40% 320 225 ±23.5 ±8.93 ±2.32%

[0099] When the proton energy increases from 70 MeV to 230 MeV the percentage variations of the fields in the bending magnets decrease from about ±5% to about ±2% without ever changing direction.

[0100] Bean dynamics calculations show that also in the quadrupoles the directions of the magnetic fields do not change sign, so that for the embodiment of FIG. 1 2-quadrant power supplies are sufficient. The same statement is valid for the embodiment of FIG. 2. However, in other embodiments the dynamics of the beams are different and it may be necessary to use 4 quadrant switch mode power supplies.

[0101] From the above description it can be seen that the teaching of this invention efficiently solves the proposed objects and obtains the advantages indicated.

[0102] People skilled in the art can introduce modifications or variations without leaving the scope of protection of the present invention as described and claimed.

[0103] As an example, the dimensions of the beamlines described above with reference to FIGS. 1 and 2 are preferred but not mandatory.

[0104] In a particularly advantageous embodiment, the rapid longitudinal tracking of the tumour according to the invention can be combined with rescanning or repainting, for example with 5 times repeated scans. This combination offers the best method for accurately irradiating a moving target.

[0105] It is also clear that the beam transport lines, as described and claimed, can also be used whenever the beam energy is changed rapidly and can result in shorter treatment times. This is because by using fast 2- and/or 4-quadrant switch mode power supply units, the magnetic elements in the beam transport line are able to adapt more quickly to energy changes in the beam.

[0106] In order to follow the energy of a proton therapy beam the present invention modifies the focusing and bending properties of a beamline by using rapidly varying 2-quadrant and 4-quadrant power supplies, possibly working in the well-known switch-mode. At present the fractional current variations of such rapid power supplies have soft limits of about ±10% and this determines the limit quoted above. However, this band of variation, which may increase, is more than sufficient for the 3-dimensional tracking of a target.

[0107] The rapid changes of the currents powering the interested magnetic elements are preferably synchronous and cause small proton losses along the beamline, preferably losses less than 10%. Moreover, the transverse FWHMs of the beam spot in the target have to vary by less than ±10%.

[0108] In conclusion, a beam transport line with a large energy acceptance is not required, because when the beamline electromagnets are driven by either a rapid 2-quadrant or a rapid 4-quadrant power supply the beam transport line can efficiently transmit beams of varying energy.