Durante, M.

Krämer, M.

Scifoni, E.

Wälzlein, C.

GSI Repository

Auger electrons emitted from metallic nanoparticles under proton irradiation∗C. Wa¨lzlein†1,2, M. Kra¨mer1, E. Scifoni1, and M. Durante1,21GSI, Darmstadt, Germany; 2FIAS, Frankfurt, GermanyThe goal of radiation therapy is to deliver the maximumpossible effective dose to the tumour while sparing the sur-rounding healthy tissue. Metallic nanoparticles (NPs) areof recent scientific interest as they might help to enhancethe effective dose ration between tumour tissue and healthytissue. Metallic NPs accumulate preferably in tumour tis-sue and high Z (Z: atomic number) materials provide apromising source for many low-energy electrons. For highZ materials, the emission of Auger electron cascades is apossible decay channel after irradiation. For one primaryionization event it is therefore likely that a large amount ofelectrons is emitted. Electrons with energies below 100 eVhave short ranges and can lead to high localized damage,thus enhancing the effectiveness of the dose.The GSI track structure Monte Carlo (MC) code TRAX [1,2, 3, 4], whose main purpose is to properly describe cre-ation and transport of low-energy electrons, has been fur-ther extended to allow the description of Auger electroncascades. Furthermore, cross sections have been assessedto properly describe electron creation and transport inmetallic materials like gold, silver, platinum, gadoliniumand iron. With these cross sections, including electron en-ergies down to a few electron Volts, it is possible to cal-culate the paths of electrons on the nanometer scale. Elec-trons inside and outside metallic nanoparticles can be ana-lyzed.Calculations have been performed for 80 MeV proton pro-jectiles and nanoparticles with a radius of 22 nm. It hasbeen observed, that for NPs consisting of atomic Pt andAu, the number of emitted Auger electrons and cascades ismuch higher than for Gd. Spectra of emitted Auger elec-trons show, that a large number of Auger electrons withenergies below 100 eV are emitted for Pt and Au. For Ptand Au, the absolute Auger electron yields are higher thanfor Gd and Auger electrons from different transitions canbe observed. For Gd, almost all emitted Auger electronshave an energy of around 150 eV.More details on these calculations and the resulting localdose in the surrounding tissue can be found in [4].References[1] M. Kra¨mer and M. Durante, Eur. Phys. J. D, 60 (2010) 195.[2] C. Wa¨lzlein et al., Appl. Radiat. Isotopes 83, (2013) 171.[3] C. Wa¨lzlein et al., Nucl. Instrum. Meth. B, 320, (2014) 75.[4] C. Wa¨lzlein et al., Phys. Med. Biol., accepted, (2014).∗Work supported by Beilstein Institute (NanoBiC project).Work is part of HGS-HIRe.† c.waelzlein@gsi.deFigure 1: Comparison of Auger electron cascade distribu-tions for Pt, Au and Gd (top panel) for 80 MeV protonsincident on NPs with a radius of 22 nm. Below: spectra ofAuger electrons created inside NPs made out of Pt, Au orGd (from second to bottom panel).GSI SCIENTIFIC REPORT 2013 BIOPHYSICS-27doi:10.15120/GR-2014-1-BIOPHYSICS-27 229

Auger electrons emitted from metallic nanoparticles under proton irradiation

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Auger electrons emitted from metallic nanoparticles under proton irradiation

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