Feasibility Study of a Small Field Detector Based on a Microfluidic Calorimeter
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The widespread proliferation of modern external beam radiotherapy devices employing small or non-standard fields has created a number of challenges for accurate reference dosimetry measurements based on ionization chambers, as they require an ever increasing number of corrections. A miniature water-based calorimeter, on the other hand, would allow for direct measurement of absorbed dose to water that can be traced to standards entirely independent of radiation. In this study, a microfluidic calorimeter prototype developed at the Korea Advanced Institute of Science and Technology was assessed for its feasibility as a detector for measurement of absolute dose to water in small and composite fields. Using the GEANT4 Monte Carlo simulation toolkit, the detector design was examined for the water equivalence and the angular dependence of the absorbed dose to the active calorimeter volume inside three different radiation fields. The initial design exhibited poor water equivalence but this was remedied through a simple modification to the detector geometry. The modified design was subsequently re-tested and it showed a maximum water equivalence deviation of 1.15% while angular fluctuations remained within 1.1%, thus indicating that the modified microfluidic calorimeter is a promising concept for the construction of a calorimeter-based absorbed dose to water detector for absolute dosimetry.
KeywordsMicrofluidic calorimeter Small field dosimetry Absorbed dose Absolute measurement High-precision radiotherapy Monte Carlo simulation
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This work was financially supported by the Korea Agency for Technology and Standards (grant no. 10069168) and the Ministry of Science and ICT (grant No. NRF-2016M2A2A6A03946564). The authors are particularly grateful to Jong Hyun Kim and Won Hee Lee from the Korea Advanced Institute of Science and Technology for designing the original calorimeter model. Furthermore, the authors kindly acknowledge Elekta AB for providing proprietary geometry data on the structure of the GK model Perfexion.
- International Atomic Energy Agency, Absorbed Dose Determination in External Beam Radiotherapy: An International Code of Practice for Dosimetry Based on Standards of Absorbed Dose to Water, Technical Report Series No. 398, Vienna, 2000.Google Scholar
- Institute of Physics and Engineering in Medicine, Small field MV photon dosimetry, IPEM Report No. 103, York, 2010.Google Scholar
- International Atomic Energy Agency, Dosimetry of Small Static Fields Used in External Beam Radiotherapy: An IAEA-AAPM International Code of Practice for Reference and Relative Dose Determination, Technical Report Series No. 483, Vienna 2017.Google Scholar
- S. Incerti, M. Asai and D. Wright, GEANT4 Tutorial at KIRAMS, Seoul, Korea (2017), https://doi.org/geant4.in2p3.fr/IMG/pdf_PhysicsLists.pdf. Google Scholar
- F. Romano et al., NSS’07.IEEE, 2581 (2007)Google Scholar
- T. H. Kim et al., Development of IAEA Phase-Space Database for Leksell Gamma Knife® Perfexion™ Using Multi-threaded GEANT4 Simulation, Phys. Med. Biol. (2018), under review.Google Scholar
- T. H. Kim et al., Presentation at the Spring Meeting of the Korean Nuclear Society (Jeju Island, Korea, 2016).Google Scholar
- F. M. Khan, The Physics of Radiation Therapy, 3rd ed. (Lippincott Williams & Wilkins, Philadelphia, 2003).Google Scholar