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Luo W , Fourkal E , Li J , Ma CM
Particle selection and beam collimation system for laser-accelerated proton beam therapy
Medical Physics. 2005 ;32(3) :794-806
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Abstract
In a laser-accelerated proton therapy system, the initial protons have broad energy and angular distributions, which are not suitable for direct therapeutic applications. A compact particle selection and collimation device is needed to deliver small pencil beams of protons with desired energy spectra. In this work, we characterize a superconducting magnet system that produces a desired magnetic field configuration to spread the protons with different energies and emitting angles for particle selection. Four magnets are set side by side along the beam axis; each is made of NbTi wires which carry a current density of ?105 A/cm2 at 4.2 K, and produces a magnetic field of ?4.4 T in the corresponding region. Collimation is applied to both the entrance and the exit of the particle selection system to generate a desired proton pencil beam. In the middle of the magnet system, where the magnetic field is close to zero, a particle selection collimator allows only the protons with desired energies to pass through for therapy. Simulations of proton transport in the presence of the magnetic field show that the selected protons have successfully refocused on the beam axis after passing through the magnetic field with the optimal magnet system. The energy spread for any given characteristic proton energy has been obtained. It is shown that the energy spread is a function of the magnetic field strength and collimator size and reaches the full width at half maximum of 25 MeV for 230 MeV protons. Dose distributions have also been calculated with the GEANT3 Monte Carlo code to study the dosimetric properties of the laser-accelerated proton beams for radiation therapy applications. © 2005 American Association of Physicists in Medicine.
Notes
00942405 (ISSN) Cited By: 1; Export Date: 25 May 2006; Source: Scopus CODEN: MPHYA; DOI: 10.1118/1.1861772 Language of Original Document: English Correspondence Address: Luo, W.; Department of Radiation Oncology; Fox Chase Cancer Center Philadelphia, PA 19111, United States; email: wei.luo@fcc.edu Chemicals/CAS: niobium, 7440-03-1; titanium, 7440-32-6, Protons References: Bortfield, T., An analytical approximation of the Bragg curve for therapeutic proton beams (1997) Med. Phys., 24, pp. 2024-2033; Fuss, M., Hug, E.B., Schaefer, R.A., Nevinny-Stickel, M., Miller, D.W., Slater, J.M., Slater, J.D., Proton radiation therapy (PRT) for pediatric optic pathway gliomas; Comparison with 3D planned conventional photons and a standard photon technique (1999) Int. J. Radiat. 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