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Experimental Study for the Absorbed-Dose to Water of Heavy Ion Beam by An Ionization Method

S Jin, K Wang*, J Zhang, z wang, National Institute of Metrology, Beijing, Beijing,CN,

Presentations

(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: absorbed-dose to water of heavy ion beam is a fundamental quantity for heavy ion therapy. The uncertainty of the absorbed-dose to water of heavy ion beam is larger than 3%, in which the beam quality correction(kQ) is the main contributor. The absolute measurement experiments are promising in reducing the uncertainty budget. It is necessary to perform the relevant work with in-direct method, with the purpose of optimizing the experimental arrangement followed by the absolute measurement study for the absorbed-dose to water of heavy ion beam.


Methods: absorbed-dose to water of a carbon ion beam, with the incident energy of 400 MeV/u and spread-out Bragg peak of 6 cm, was studied via the conventional ionization method. The correction factors of polarity and ion recombination for the ionization chambers were evaluated with the incident heavy ion beam.


Results: uncertainty components for the measurement of the absorbed-dose to water of heavy ion beam are significantly larger than that of the 6°Co ? radiation, in terms of the corrections for the polarity and ion recombination of the ionization chambers. The absorbed-dose to water of heavy ion beam from different ionization chambers are eventually deduced, which are consistent within the acceptance of uncertainty.


Conclusion: on the measurement with ionization chambers, it is crucial to conduct more intensive research activities of radiation dosimetry including the absolute measurement with calorimetric facility, aiming to further optimize the uncertainty in the measurement for the absorbed-dose to water of heavy ion beam.

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Funding Support, Disclosures, and Conflict of Interest: Supported by the National Key Technologies R&D Program of China (Grant No. 2016YFF0200804 and 2017YFF0205405)

Keywords

Calibration, Polarity Effects, Ion Recombination

Taxonomy

TH- External Beam- Particle/high LET therapy: Carbon ion therapy - calibration protocols and primary standards (including detector response simulation)

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