Helium radiography with a digital tracking calorimeter—a Monte Carlo study for secondary track rejection

Helge Egil Seime Pettersen*, Lennart Volz, Jarle Rambo Sølie, Johan Alme, Gergely Gábor Barnaföldi, Rene Barthel, Anthony van den Brink, Vyacheslav Borshchov, Mamdouh Chaar, Viljar Eikeland, Georgi Genov, Ola Grøttvik, Håvard Helstrup, Ralf Keidel, Chinorat Kobdaj, Naomi van der Kolk, Shruti Mehendale, Ilker Meric, Odd Harald Odland, Gábor PappThomas Peitzmann, Pierluigi Piersimoni, Maksym Protsenko, Attiq Ur Rehman, Matthias Richter, Andreas Tefre Samnøy, Joao Seco, Hesam Shafiee, Arnon Songmoolnak, Ganesh Tambave, Ihor Tymchuk, Kjetil Ullaland, Monika Varga-Kofarago, Boris Wagner, Ren Zheng Xiao, Shiming Yang, Hiroki Yokoyama, Dieter Röhrich

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Radiation therapy using protons and heavier ions is a fast-growing therapeutic option for cancer patients. A clinical system for particle imaging in particle therapy would enable online patient position verification, estimation of the dose deposition through range monitoring and a reduction of uncertainties in the calculation of the relative stopping power of the patient. Several prototype imaging modalities offer radiography and computed tomography using protons and heavy ions. A Digital Tracking Calorimeter (DTC), currently under development, has been proposed as one such detector. In the DTC 43 longitudinal layers of laterally stacked ALPIDE CMOS monolithic active pixel sensor chips are able to reconstruct a large number of simultaneously recorded proton tracks. In this study, we explored the capability of the DTC for helium imaging which offers favorable spatial resolution over proton imaging. Helium ions exhibit a larger cross section for inelastic nuclear interactions, increasing the number of produced secondaries in the imaged object and in the detector itself. To that end, a filtering process able to remove a large fraction of the secondaries was identified, and the track reconstruction process was adapted for helium ions. By filtering on the energy loss along the tracks, on the incoming angle and on the particle ranges, 97.5% of the secondaries were removed. After passing through 16 cm water, 50.0% of the primary helium ions survived; after the proposed filtering 42.4% of the primaries remained; finally after subsequent image reconstruction 31% of the primaries remained. Helium track reconstruction leads to more track matching errors compared to protons due to the increased available focus strength of the helium beam. In a head phantom radiograph, the Water Equivalent Path Length error envelope was 1.0 mm for helium and 1.1 mm for protons. This accuracy is expected to be sufficient for helium imaging for pre-treatment verification purposes.

Original languageEnglish
Article number035004
Pages (from-to)1-19
Number of pages19
JournalPhysics in Medicine and Biology
Volume66
Issue number3
DOIs
Publication statusPublished - 7 Feb 2021

Bibliographical note

Funding Information:
This work has been funded by the Trond Mohn Foundation (Grant Nos. BFS2015PAR03 and BFS2017TMT07) and by the Research Council of Norway (Grant No. 250858). GGB, PG, VKM are partially supported by the Hungarian Research Fund NKFIH under Contract Nos. K120660, 2019-2.1.11-TÉT-2019-00050 and 2019-2.1.6-NEMZ_KI-2019-00011.

Publisher Copyright:
© 2021 Institute of Physics and Engineering in Medicine

Copyright:
Copyright 2021 Elsevier B.V., All rights reserved.

Funding

This work has been funded by the Trond Mohn Foundation (Grant Nos. BFS2015PAR03 and BFS2017TMT07) and by the Research Council of Norway (Grant No. 250858). GGB, PG, VKM are partially supported by the Hungarian Research Fund NKFIH under Contract Nos. K120660, 2019-2.1.11-TÉT-2019-00050 and 2019-2.1.6-NEMZ_KI-2019-00011.

Keywords

  • Digital tracking calorimeter
  • Helium imaging
  • Helium radiography
  • List mode imaging
  • Nuclear interactions

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