Speaker
Description
The interaction of biomolecules with positron is of special interest apropos to positron emission tomography (PET) scans [1,2]. Using positron emitters in PET scans has aided the early detection of cancer and brain disorders. Furthermore, this technique has also been considered an alternative to ion beam cancer treatments for dosimetry purposes. The cross-section resulting from the interaction of positrons with biologically relevant media is used to model single positron tracks in such media [3]. The particle-tracking codes such as PENELOPE, GEANT, and LEPTS are used to model the radiation damage at the cellular level, which require cross-sections as their basic input [4]. Positron impact cross-section calculation/measurements are in a nascent stage even though having such important applications. In the literature, the elastic and total cross sections are fairly reported; however, for the inelastic processes (ionisation, excitation, annihilation) not much data is available [5]. In the present work, we review the status of the positron impact ionisation cross-section calculation. Recently, the binary encounter bethe (BEB) method, a well-known method for electron ionisation cross section calculation has been applied for positron scattering systems showing encouraging results [6,7]. This fills the void for the total ionisation cross-section data. The input parameters required for BEB are very simple and straightforward, and hence we focus on this method. The next step will be to obtain the partial ionisation cross-section which is dependent on the accurate branching ratio determination. The progress on this problem will be presented and discussed during the events.
REFERENCES
[1] Phelps, M.E., 2000. Positron emission tomography provides molecular imaging of biological processes. Proceedings of the National Academy of Sciences, 97(16), pp.9226-9233.
[2] Jan, S., Santin, G., Strul, D., Staelens, S., Assié, K., Autret, D., Avner, S., Barbier, R., Bardies, M., Bloomfield, P.M. and Brasse, D., 2004. GATE: a simulation toolkit for PET and SPECT. Physics in Medicine & Biology, 49(19), p.4543.
[3] Blanco F, Munoz A, Almeida D, Ferreira da Silva F, Limao-Vieira P, Fuss MC, Sanz AG, García G. Modelling low energy electron and positron tracks in biologically relevant media. The European Physical Journal D. 2013 Sep;67(9):1-8.
[4] Arce, P., Muñoz, A., Moraleda, M., Gomez Ros, J.M., Blanco, F., Perez, J.M. and García, G., 2015. Integration of the low-energy particle track simulation code in Geant4. The European Physical Journal D, 69(8), pp.1-5.
[5] Brunger, M.J., Buckman, S.J. and Ratnavelu, K., 2017. Positron scattering from molecules: An experimental cross section compilation for positron transport studies and benchmarking theory. Journal of Physical and Chemical Reference Data, 46(2), p.023102.
[6] Fedus, K. and Karwasz, G.P., 2019. Binary-encounter dipole model for positron-impact direct ionization. Physical Review A, 100(6), p.062702.
[7] Franz, M., Wiciak-Pawłowska, K. and Franz, J., 2021. Binary-Encounter Model for Direct Ionization of Molecules by Positron-Impact. Atoms, 9(4), p.99.