Establishing general correction strategies for photon detectors in magnetic fields based on convolution analysis

• Applicant: Dr. Hui Khee Looe
• Subject Area: Medical Physics, Biomedical Technology
• Term: from 2015 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 286652001

• Final Report Year: 2024

Final Report Abstract

The outcomes of the project represent multiple important milestones in the development of dosimetry protocol for MRgRT. Firstly, the demonstration on the applicability of the established mathematical convolution model in a magnetic field has pathed the way for the development of generic correction strategies. This has been achieved by combining comprehensive Monte Carlo simulations and a physics model-based deep learning framework. Furthermore, besides the derivation of correction factors, detailed study on the detector behaviors in magnetic field, especially in small field conditions, has allowed for deep understanding on the underlying physical mechanisms contributing to the observed detector response. These insights are invaluable to the community regarding the establishment of good clinical practice, dosimetry protocol, as well as the future development of suitable detectors for measurements in a magnetic field. The results produced in this project have been wellreceived by the medical physics community. This is reflected in the resulted 9 full research papers, published exclusively in two prestigious journals in the field of Medical Physics (Physics in Medicine and Biology and Medical Physics).

Publications

• Magnetic field influences on the lateral dose response functions of photon-beam detectors: MC study of wall-less water-filled detectors with various densities. Physics in Medicine and Biology, 62(12), 5131-5148.
  Looe, Hui Khee; Delfs, Björn; Poppinga, Daniela; Harder, Dietrich & Poppe, Björn
  
• 2D convolution kernels of ionization chambers used for photon-beam dosimetry in magnetic fields: the advantage of small over large chamber dimensions. Physics in Medicine & Biology, 63(7), 075013.
  Looe, Hui Khee; Delfs, Björn; Poppinga, Daniela; Harder, Dietrich & Poppe, Björn
  
• Magnetic fields are causing small, but significant changes of the radiochromic EBT3 film response to 6 MV photons. Physics in Medicine & Biology, 63(3), 035028.
  Delfs, Björn; Schoenfeld, Andreas A.; Poppinga, Daniela; Kapsch, Ralf-Peter; Jiang, Ping; Harder, Dietrich; Poppe, Björn & Looe, Hui Khee
  
• The 1D lateral dose response functions of photon-dosimetry detectors in magnetic fields—measurement and Monte-Carlo simulation. Physics in Medicine & Biology, 63(19), 195002.
  Delfs, Björn; Poppinga, Daniela; Ulrichs, Ann-Britt; Kapsch, Ralf-Peter; Harder, Dietrich; Poppe, Björn & Looe, Hui Khee
  
• The dose response of high‐resolution diode‐type detectors and the role of their structural components in strong magnetic field. Medical Physics, 47(12), 6509-6518.
  Tekin, Tuba; Blum, Isabel; Delfs, Björn; Schönfeld, Ann‐Britt; Kapsch, Ralf‐Peter; Poppe, Björn & Looe, Hui Khee
  
• The dose response of PTW microDiamond and microSilicon in transverse magnetic field under small field conditions. Physics in Medicine & Biology, 66(15), 155003.
  Blum, Isabel; Tekin, Tuba; Delfs, Björn; Schönfeld, Ann-Britt; Kapsch, Ralf-Peter; Poppe, Björn & Looe, Hui Khee
  
• The role of the construction and sensitive volume of compact ionization chambers on the magnetic field‐dependent dose response. Medical Physics, 48(8), 4572-4585.
  Delfs, Björn; Blum, Isabel; Tekin, Tuba; Schönfeld, Ann‐Britt; Kranzer, Rafael; Poppinga, Daniela; Giesen, Ulrich; Langner, Frank; Kapsch, Ralf‐Peter; Poppe, Björn & Looe, Hui Khee
  
• Erratum: The magnetic field dependent displacement effect and its correction in reference and relative dosimetry (2022 Phys. Med. Biol. 67 045004). Physics in Medicine & Biology, 67(8), 089501.
  Tekin, Tuba; Blum, Isabel; Delfs, Björn; Schönfeld, Ann-Britt; Poppe, Björn & Looe, Hui Khee
  
• Model-based machine learning for the recovery of lateral dose profiles of small photon fields in magnetic field. Physics in Medicine & Biology, 67(8), 085006.
  Looe, Hui Khee; Blum, Isabel; Schönfeld, Ann-Britt; Tekin, Tuba; Delfs, Björn & Poppe, Björn
  
• The magnetic field dependent displacement effect and its correction in reference and relative dosimetry. Physics in Medicine & Biology, 67(4), 045004.
  Tekin, Tuba; Blum, Isabel; Delfs, Björn; Schönfeld, Ann-Britt; Poppe, Björn & Looe, Hui Khee