ION ACCELERATION COMPLEX FOR THE TREATMENT OF ATRIAL FIBRILLATIONS

Abstract

A system (12) is proposed for the acceleration of ions to treat Atrial Fibrillation (AF), arteriovenous malformations (AVMS) and focal epileptic lesions; this system (12) includes a pulsed ion source (1), a pre-accelerator (3) and one or more linear accelerators or linacs (5, 6, 7) operating at frequencies above 1 GHz with a repetition rate between 1 Hz and 500 Hz. The particle beam coming out of the complex (12) can vary (i) in intensity, (ii) in deposition depth and (iii) transversally with respect to the central beam direction. The possibility of adjusting in a few milliseconds and in three orthogonal directions, the location of each energy deposition in the body of the patient makes that system of accelerators (12) perfectly suited to irradiation of a beating heart.

Claims

1-11. (canceled)

12. A method of using a linear ion accelerator for the treatment of Atrial Fibrillation (AF) in the heart of a patient in need thereof comprising: producing beam pulses of accelerated ions with an atomic number between 1 (protons) and 10 (neon ions); delivering a dose of the beam pulses of accelerated ions to the heart using spot scanning and multi-painting, wherein a three-dimensional feedback system is used to deliver the dose to treat the AF in the heart without unwanted irradiation of tissues that have to be spared.

13. The method of claim 12 wherein the feedback system is used to compensate for movements of the irradiated heart.

14. The method of claim 13 further comprising varying two transverse positions and a depth of each spot before delivering each spot to compensate for movements due to the respiration cycle or to the patient's heartbeat.

15. The method of claim 14 wherein the variation of the depth corresponds to a variation of energy of the accelerated ions.

16. A method of using a linear ion accelerator for the treatment of an arteriovenous malformation (AVM) in a patient in need thereof comprising: producing beam pulses of accelerated ions with an atomic number between 1 (protons) and 10 (neon ions); delivering a dose of the beam pulses of accelerated ions to the AVM using spot scanning and multi-painting, wherein a three-dimensional feedback system is used to deliver the dose to the AVM without unwanted irradiation of tissues that have to be spared.

17. The method of claim 16 wherein the feedback system is used to compensate for movements of the irradiated AVM.

18. The method of claim 17 further comprising varying two transverse positions and a depth of each spot before delivering each spot to compensate for movements of the AVM.

19. The method of claim 17 wherein the variation of the depth by the three-dimensional feedback system corresponds to a variation of energy of the accelerated ions.

20. A method of using a linear ion accelerator for the treatment of an epileptic lesion in a patient in need thereof comprising: producing beam pulses of accelerated ions with an atomic number between 1 (protons) and 10 (neon ions); delivering a dose of the beam pulses of accelerated ions to the epileptic lesion using spot scanning and multi-painting, wherein a three-dimensional feedback system is used to deliver the dose to the epileptic lesion without unwanted irradiation of tissues that have to be spared.

21. The method of claim 20 wherein the feedback system is used to compensate for movements of the irradiated epileptic lesion.

22. The method of claim 21 further comprising varying two transverse positions and a depth of each spot before delivering each spot to compensate for movements of the epileptic lesion.

23. The method of claim 22 wherein the variation of the depth by the three-dimensional feedback system corresponds to a variation of energy of the accelerated ions.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0044] Further advantages, details and characteristics of the use of linear ion accelerations for the treatment of Atrial Fibrillation and the corresponding ion accelerator system according to the invention result from the following description of the proposed application and of a from of implementation of an appropriate ion accelerator system schematically illustrated as an example in the annexed drawing.

[0045] With reference in the first place to the only FIGURE, the main components of the complex of hadron accelerators for the application of the invention are: [0046] 1. An ion source, producing ion pulses about 5 microsecond long at repetition rates in the range between 1 Hz and 500 Hz; [0047] 2. A Low Energy Beam Transport magnetic channel (LEBT—Low Energy Beam Transport); [0048] 3. A pre-accelerator, which can be either a Radiofrequency Quadrupole (RFQ) or a cyclotron or a synchrocyclotron or a special type of linac capable of accelerating very slow hadrons; [0049] 4. A Medium Energy Beam Transport channel (MEBT); [0050] 5. A first linac section, at a radiofrequency greater than 1 GHz; [0051] 6. A second linac section working at a radiofrequency that can be a multiple of the one of the first linac section; [0052] 7. A third linac section at a frequency that can be a multiple of the one of the second linac section; [0053] 8. A High Energy Beam Transport channel (HEBT) that brings the accelerated beam to the patient treatment rooms; [0054] 9. A fan-out magnet that, in its preferred implementation, sends the beam pulses, of variable energy and intensity, to the treatment rooms; [0055] 10. A system of beam transport lines to wards the treatment rooms, each containing the two scanning magnets (that define the dimensions of the irradiated field by moving vertically and horizontally the ion beam) and the monitoring system; [0056] 11. Robotic chairs where the seated patients receive in the heart the dose prescribed by the Treatment Planning System (TPS). [0057] 12. The facility or complex of hadron accelerators according to the invention; [0058] 13. A complex of subsystems or sections of linac (5; 6; 7); [0059] 14. A system of transport lines of the pulses of ions to the points where patients are irradiated.

[0060] It is worth underlining that the subsystems or sections 5,6 and 7 of the FIGURE are not necessarily all present at the same time in each implementation.

[0061] More precisely, referring to FIG. 1, according to the invention the hadron accelerator complex 12 includes various kinds of accelerators serially connected, namely a pre-accelerator 3 and a number of linac sections 5, 6, 7; their oscillatory frequencies can gradually increase so as to have in the last linac a higher gradient and thus reduce the overall length of the system. To simplify the overall scheme some of the three linac sections 5,6, 7 may be absent.

[0062] The pre-accelerator 3 is fed by the ion source 1. Its output beam can be continuous or, better, modulated at the 1-500 Hz repetition rate in pulses that are few microseconds long, so that the number of ions sent through MEBT 4 to the first section of the linac 5 is minimal and does not produce unnecessary radioactivity in the elements which follow.

[0063] Each linac section 5,6,7 is made of ‘accelerating units’, which can be either Travelling Wave linacs or Standing Wave linacs and have structures of the types Drift Tube Linac (DTL), IH Drift Tube Linac, CH Drift Tube Linac, Coupled-cavity LinacUSing Transverse Electric Radial fields (CLUSTER), Side Coupled Drift Tube Linac (SCDTL), Cell Coupled Linac (CCL) or others according to the speed of the accelerated hadrons. Accelerating structures of these types are well known, others are described in the documents U.S. Pat. No. 6,888,326 B2, U.S. Pat. No. 7,423,278 B2 and U.S. Pat. No. 7,554,275 B2 in the name of the Applicant and are quoted and incorporated in the present application as examples, referring to the quoted documents for further details.

[0064] It can be remarked that to reach, with an average gradient equal to 30 MV/m, the total voltage required for AV treatments—protons: about 160 MV; helium ions: about 320 MV; carbon ions: about 600 MV—the total lengths of the linacs are about 5 m for protons, 10 in for helium ions and 20 in for carbon ions.

[0065] In general the linac section producing the largest acceleration gradient is the one indicated as 7 in FIG. 1. As described above, it is this last section that is usually subdivided in units that are independently powered so that the energy of the output particles can be adjusted pulse by pulse.

[0066] The accelerated ion be amis transported to the treatment rooms through the HEBT channel 8. In some forms of implementation this is obtained with the fan-out magnet 9, whereas in other implementations the standard beam transport design—as used in cancer therapy centres featuring rotating gantries—will be chosen.

[0067] Patients can be treated either on a robotic chair 11, as indicated in the preferred implementation of the picture, or lying on a computer controlled moving couch. [0068] MACROBUTTON In the application for the treatment of Atrial HTMLDirect Fibrillation according to the invention the particle beam coining out of complex 12, 8 can vary in [0069] (i) intensity (acting on the ion source (1)), (ii) in deposition depth (by adjusting independently the radiofrequency power sources feeding the accelerating units of the linacs), and (iii) transversally with respect to the central beam direction (by varying the currents in the coils of two orthogonal scanning magnets placed upstream of each patient). [0070] The possibility to adjust, in a few milliseconds and in three orthogonal directions, the location of each energy deposition in the body of the patient makes the accelerator system 12 perfectly suited to irradiation of a beating heart.

[0071] As an example a possible scheme of said complex 12, summarized in the following Table 1, is composed of:

(A) a computer controlled helium source 1—which can be either of the Electron Cyclotron Resonance (ECR) type (properly modified to obtain a beam pulsed at repetition rates in the range 1-500 Hz), or of the Electron Beam Ion Source type (EBIS) or other;
(B) a60 MeV/u cyclotron or synchrocyclotron 3, with coils which are either at room temperature or superconducting;
(C) a Cell Coupled Linac of the LIBO 7 type miming at 3 GHz and made of 10 separately powered units.

[0072] The firms Thales, France and CPI, US produce—among other companies—the 3 GHz klystrons needed for the form of implementation mentioned.

[0073] In the form of the preferred implementation of the linac in table 1, the pre-accelerator is superconducting. Its magnetic field configuration and dimensions are similar to the ones of the superconducting cyclotron commercialized by Varian Medical Systems, Inc. (Palo Alto, USA) for cancer proton beam therapy. The magnet, requiring only about 40 kW for cryogenics, has a diameter of 3.2 in and a height of 1.6 m. The overall consumption is below 200 kW. The source 1 injects axially the pulses of helium ions.

TABLE-US-00001 TABLE 1 Example of a 3 GHz linac to accelerate 4He2 + ions Frequency [MHz] 2998 Q (ion charge) 2 A (ion mass number) 4 Input energy [MeV/u] 60 Total input energy [MeV] 240 Maximum output energy [MeV/u] 160 Total maximum output energy [MeV] 640 Number of accelerating cells per 18-16 accelerating structure (tank) Diameter of the iris [mm] 7 Number of units 10 Lengths of the units [m] 0.75-1.05 Total length of the Linac [m] 9.5 Average transit time factor T 0.85 Effective Shunt Impedance ZT2 [MΩ/m] 53-77 Average electric field on the axis E0 [MV/m] 33 Maximum surface electric field [MV/m] 140 Normalized transverse acceptance at 2.4 2 rms [π mm mrad] Peak power per unit [MW] 10 Duration of RF pulse [μs] 4 Repetition rate [Hz] 120 Fraction of time with beam (‘duty cycle’)[%] 0.048 Average power to feed the 10 klystrons[kW] 150

[0074] From the structural and functional description of the various forms of implementations of ion acceleration plants or complexes for application, according to the invention, in the treatment of atrial fibrillation, it can be noticed that the proposed invention efficiently achieves the stated aim and obtains the mentioned advantages.

[0075] The experts in the field may introduce modifications and variations of the single components and their combination, both in structure and/or dimensions, of the systems proposed for the use following the invention by adapting it to specific cases without departing from the scope of the present invention as described in the following claims.

LITERATURE

[0076] List of some publications in the field of high-frequency linacs for hadrontherapy: [0077] R. W. Hamm, K. R. Crandall, and J. M. Potter, Preliminary design of a dedicated proton therapy linac, in Proc. PAC90, Vol 4 (San Francisco, 1991) 2583. [0078] U. Amaldi, M. Grandolfo and L. Picardi (Eds), The RITA Network and the Design of Compact Proton Accelerators, INFN, Frascati, 1996, ISBN 88-86409-08-7. The “Green Book”, Chapter 9. [0079] L. Picardi, C. Ronsivalle and B. Spataro, Design development of the SCDTL structure for the TOP Linac, Nuclear Instruments and Methods A, 425 (1999) 8. [0080] U. Amaldi et al., A Linac-booster for Protontherapy: Construction and Tests of a Prototype, Nuclear Instruments and Methods A 521 (2004) 512. [0081] U. Amaldi, S. Braccini, and P. Puggioni, High frequency linacs for hadrontherapy, Rev. Acc. Sci. Tech. 2 (2009) 111. [0082] U. Amaldi et al., Accelerators for hadrontherapy: from Lawrence cyclotrons to linacs, Nuclear Instruments and Methods A 620 (2010) 563.