Atomic and Nuclear Data for Auger emitters Roger

Atomic and Nuclear Data for Auger emitters Roger W. Howell Department of Radiology Division of Radiation Research Rutgers New Jersey Medical School Member, MIRD Committee and ICRU

Introduction l l l Properties of Auger electron emitters Number of electrons per decay Sources of Auger electron spectrum – isolated atom versus molecular structure Suggestions for atomic/nuclear data Production of Pt-193 m

Decay Schemes - Auger Electron Emitters

Number Auger electrons Emitted Depends on number of EC and IC events, Z, and… l 125 I (EC and IC) l Emits ~5 -40 Auger electrons per decay l Average of about 24 per decay l 193 m. Pt, 195 m. Pt l Average l (three IC) of > 30 per decay Number depends on assumptions

Monte Carlo Simulation of Auger Electron Cascades and Ionizations around Decay Sites Wright et al. Radiat. Prot. Dosim. 31, 59 -62 (1990).

Does every Auger electron cause DNA damage?

Calculated Number of Auger electrons Depends on Computational Approach Pomplun Int J Radiat Biol 88, 108 -114, 2012.

MIRD and ENSDF Decay Data ENSDF MIRD Even more detail in CD

MIRD – Detailed Auger Spectra l l l l l Output File Out. PutI-125. ACK for I-125 724 Auger/Coster-Kronig Spectrum for I-125 Number of electrons: 724 START RADIATION RECORDS Y(/nt) E(e. V) transition 2. 00936 E-03 8. 20000 E-01 N 2 N 3 O 2 9. 01809 E-03 1. 53000 E+00 M 2 M 3 N 4 3. 18357 E-03 1. 74000 E+00 N 2 N 3 O 3 2. 83403 E-03 1. 77000 E+00 M 4 M 5 O 2 1. 65051 E-02 1. 90000 E+00 M 1 M 3 N 1 9. 61848 E-03 2. 69000 E+00 M 4 M 5 O 3 2. 24245 E-01 2. 70000 E+00 N 1 N 3 N 4 2. 15685 E-02 3. 06000 E+00 M 2 M 3 N 5 1. 94770 E-02 3. 07000 E+00 M 1 M 2 N 3 3. 15383 E-01 4. 23000 E+00 N 1 N 3 N 5 1. 35180 E+00 1. 22800 E+01 N 5 O 1 …………

Computer Simulation of DNA strand breaks caused by 125 I-CAP l l DNA duplex + catabolite gene activator protein (CAP) 43 mer oligo. DNA PARTRAC radiation track structure code Direct effects l l l Charge neutralization Electron irradiation Indirect effects Charge neutralization dominates DNA damage within 5 -7 base pairs of decay site Improved agreement between theory and experimental DNA fragment data Li et al. Radiat Environ Biophys 43, 23 -33 (2004) Li. Radiat Prot Dosimetry 122, 89 -94 (2006)

Auger Electron Spectra for Ionized Water Clusters l Auger electron spectrum for ionized water clusters is broadened relative to that for a single molecule l Should this be part of our simulations? Ohrwall et al. J Chem Phys 123, 054310 (2005).

Inter-Coulombic Decay vs Auger Decay l Auger processes l l Inner core shell vacancy ICD processes l l l Inner valence shell vacancy Leads to vacancy in neighboring atom in molecule Substantial change in emitted electron spectrum Pernpointner et al. J Chem Phys 125, 34309 (2006)

Experimental DSB Data are Complex: Theoretical Modeling Plays a Key Role in Interpreting these Data l l l l Stochastics of decays Cross sections for low energy electrons in water and DNA Stochastics of Auger spectra Direct effects (electron) Indirect effects (radicals) Charge transfer Charge neutralization Effect of molecular structure on all of the above l Models have evolved since 1987 l Further evolution of DNA-damage models will come from new developments in basic physics and chemistry

Suggested Options for ENSDF l l l l Increased detail for Auger/CK el KLL, KLX, KXY, ………. . , NXY Increased detail for X-rays and CE Average or binned-spectrum β yield/energy l avg dose calculations for cells, etc Units: Me. V (Bq s)-1 or Gy kg (Bq s)-1 Internal bremsstrahlung spectra Intercoulombic decay Output formats: Excel, ASCII

Data Needed to Select and Optimize Radionuclide Production l 193 m. Pt l 192 Pt (example) (n, γ) 193 m. Pt (σ = 2 b) l Low l 192 Os specific activity due to cold Pt (α, 3 n) 193 m. Pt (next slide) l Alpha particle energy important for yield and to minimize contaminants l High specific activity needed to maximize radiation absorbed dose and reduce chemotoxicity of cisplatin

192 Os (α, 3 n) 193 m. Pt Cross Section vs E Uddin et al. Appl Radiat Isotop 68: 2001– 2006, 2010

International Auger Symposia l l l l l 1975 Jülich, Germany (Founding) 1987 Charney Basset, UK (1 st) 1991 Amherst, USA (2 nd) 1995 Lund, Sweden (3 rd) 1999 Lund, Sweden (4 th) 2003 Melbourne, Australia (5 th) 2007 Boston, USA (6 th) 2011 Jülich, Germany (7 th) 2015 Kyoto, Japan (8 th) 2019 Oxford, UK (9 th) l August 22 -24, 2019

Auger Processes in the 21 st Century Physics & Chemistry

Stopping Powers for Low Energy Electrons 0. 01 to 10 ke. V in DNA Peudon et al. Radiat Prot Dosimetry 122, 128 -135 (2006).

Revised Stopping Powers for Low Energy Electrons 0. 1 -10 ke. V in Liquid Water Emfietzoglou and Nikjoo, Radiation Research 167, 110 -120 (2007).

Deterministic Atomic Rearrangement Model for Individual Auger Electron Spectra l l Auger spectrum for a given decay varies widely For each of 265 probable atomic rearrangements, tabulated l l l absorbed doses single-strand break (SSB) probabilities Deterministic approach used to simulate Lobachevsky & Martin (2000) data Carles & Malonda. Int J Radiat Biol 82, 211 -220 (2006)

Auger Transition Rates in H 2 O Molecules l Auger transition rates take account of l l l Normal Auger decay Resonant Auger decay Ultrafast dissociation of H 20 l Auger decay in OH and O fragments Takahashi et al. J Chem Phys 124, 64307 (2006).

Auger Spectrum is Altered in Hydrated Atoms l Auger spectrum of K+ is affected by l l l Cl. H 2 O Number of H 2 O Pokapanich et al. J. AM. CHEM. SOC. 2009, 131, 7264– 7271

Atomic Transient Recorder l Measurement capabilities in the attosecond realm may shed light on Auger relaxation dynamics Kienberger et al. (2004). "Atomic transient recorder, " Nature 427, 817 -21.

Attosecond real-time observation of electron tunnelling in atoms l l Observation of atomic relaxation dynamics in the attosecond realm May offer insight into l l l N and O shell transition rates and energies Effect of molecular interactions on Auger transition rates and energies Real time observation of Coulomb explosion? Uiberacker et al. Nature 446, 627 -632 (2007).

I know what you are thinking! l ……………. enough already! l Show me something I can use

MIRD – Decay Schemes

MIRD – Average Auger Spectra

Auger Electron Emitters for Therapy Uusijärvi et al. Medical Physics 33, 3260 -3269 (2006).

Emphasize that Auger effects are a combination of local and adjacent DNA effects l l Molecular studies largely study local effect Need cell study to examine local and distant l l Need to tie all of this together l l Radioprotector studies suggest distant very important and scavengeable Charge neutralization Electron irradiation Indirect action of radicals Which is most important when? l l Naked DNA In the cell

Auger Electron Emitters for Molecular Probes and Gene Therapy “Softer” (EC to ground state) Auger Emitters Ar-37 35 d l V-49 330 d l Fe-55 2. 6 y l Ge-71 11. 4 d l Cs-131 9. 7 d l

Origins of Bremsstrahlung photons l 90 Y b- b- 99. 99% 0. 011% b-/b+ 0. 0032 90 Zr b- Bremsstrahl photon electron Nucle us Dewaraja et al. SNM 2018

Experimental validation: detected bremsstrahlung spectrum compared with MC simulation with and without theoretical IB l 90 Y vial on HPGe detector Energy (ke. V)

Experimental Validation of SIMIND 90 Y SPECT including IB Gamma-camera Detected Spectrum 5000 Sphere in air Line profile across center of source Measured 0 60 ke. V 5000 10 120 Sphere in water Measured 0 60 (ke. V) 10 120 Dewaraja et al. SNM 2018

Dose Profile when Different Percentages of Cells are Labeled with 125 I

What are Auger electrons? X-ray versus Auger electron

Why should you care? l Auger electron emitters are widely used in diagnostic nuclear medicine l l 99 m. Tc, 111 In, 123 I, 201 Tl ………. . Auger electron emitters have yet untapped therapeutic potential