Evaluation of some dosimetric properties of a dedicated plane parallel ionization chamber for radiotherapy electron beams

Jonas Oliveira da Silva, Fernanda Beatrice Conceição Nonato, Francisco Glaildo Almeida Sampaio, Linda V. Ehlin Caldas

Abstract


Ionization chambers are the reference detectors for electron beam dosimetry. In this paper a dedicated radiotherapy plane parallel ionization chamber manufactured with low cost materials is presented for dosimetry in electron beams. The ionization chamber tested has a sensitive volume of 0.4 cm³, and the collecting electrode and the guard ring were painted with a homogeneous mixture of nail polish and graphite. The dedicated ionization chamber presented linearity of the response with the absorbed dose in the range of 0.5 Gy to 8.0 Gy, an increase of the response with the field size increasing, an angular dependence within ±5°, as recommended by international standards, and a polarity effect of 0.78% with the field size. From the results obtained, it is possible to conclude that the plane parallel ionization chamber tested in this work presents potential use for electron beam dosimetry in clinical routine.


Keywords


ionization chambers; electron beams; radiation dosimetry; radiotherapy

References


d’ERRICO, F. Dosimetric issues in radiation protection of radiotherapy patients. Radiat Prot Dosim, v. 118, p. 205-212, 2006.

MUIR, B. R.; McEWEN, M. R. Technical note: On the use of cylindrical ionization chambers for electron beam reference dosimetry. Med Phys, v. 44, n. 12, p. 6641-6646, 2017.

ALMOND, P. R.; BIGGS, P. J.; COURSEY, B. M.; HANSON, W. F.; HUQ, M. S.; NATH, R. AAPM's TG-51 protocol for clinical reference dosimetry of high-energy photon and electron beams. Med Phys, v. 26, n. 9, p. 1847-1870, 1999.

IAEA – International Atomic Energy Agency. The use of plane-parallel ionization chambers in high-energy electron and photon beams: An international Code of Practice for dosimetry. IAEA TRS 381, Vienna: IAEA, 1995.

IAEA – 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. IAEA TRS 398, Vienna: IAEA, 2000.

PEARCE, J.; THOMAS, R.; DuSAUTOY, A. The characterization of the Advanced Markus ionization chamber for use in reference electron dosimetry in the UK. Phys Med Biol, v. 51, n 3, p. 473-483, 2006.

GERBI, B. J.; KHAN, F. M. The polarity effect for commercially available plane-parallel ionization chambers. Med Phys, v. 14, n. 2, p. 210-215, 1987.

HAVERCROFT, J. M.; KLEVENHAGEN, S. C. Ion recombination corrections for plane-parallel and thimble chambers in electron and photon radiation. Phys Med Biol, v. 38, n. 1, p. 25-38, 1993.

NONATO, F. B. C.; SAKURABA, R. K.; da CRUZ, J. C.; CHIARA, A. C. M.; VERNUCIO, S. L.; MENEGUSSI, G; CALDAS, L. V. E. Development and characterization tests of a homemade ionization chamber with silver collecting electrode for use in electron beams. Biomed Phys Eng Express, v. 2, n. 1, p. 015011, 2016.

NONATO, F. B. C.; SAKURABA, R. K.; da CRUZ, J. C.; CALDAS, L. V. E. Characterization tests of a new parallel plate ionization chamber for use in electron beams. Radiat Phys Chem, v. 104, p. 244-247, 2014.

SILVA, J. O.; NONATO, F. B. C.; CALDAS, L. V. E. Characterization tests of a homemade ionization chamber in mammography standard radiation beams. Radiat Phys Chem, v. 95, p. 151-153, 2014.

PERINI, A. P.; NEVES, L. P.; FERNADEZ-VAREA, J. M.; CASSOLA, V. F.; KRAMER, R.; KHOURY, H. J.; CALDAS, L. V. E. A new parallel-plate graphite ionization chamber as a 60Co gamma radiation reference instrument. Radiat Phys Chem, v. 95, p. 106-108, 2014.

NEVES, L. P.; PERINI, A. P.; CALDAS, L. V. E. Development and characterization of a new cylindrical ionization chamber for dosimetry of 60Co beams. IEEE Trans Nucl Sci, v. 60, p. 712-715, 2013.

IEC – International Electrotechnical Commission. Medical electrical equipment - Dosimeters with ionization chambers as used in radiotherapy. IEC 60731, Brussels: IEC, 2011.

YOSHIZUMI, M.; CALDAS, L. V. E. A new ring-shaped graphite monitor ionization chamber. Nucl Instrum Meth Phys Res A, v. 219, n. 1, p. 207-210, 2010.

NONATO, F. B. C. Design, construction and characterization of reference systems for electron beams of clinical accelerators. PhD thesis. Universidade de São Paulo, 2014. (In Portuguese)

JCGM - Joint Committee for Guides in Metrology. Evaluation of measurement data — Guide to the expression of uncertainty in measurement. JCGM 100:2008, Paris: JCGM, 2008.

RAMSEY, C. R.; SPENCER, K. M.; OLIVER, A. L. Ionization chamber, electrometer, linear accelerator, field size, and energy dependence of the polarity effect in electron dosimetry. Med Phys, v. 26, n. 2, p. 214-219, 1999.

WILLIAMS, J. A.; AGARWAL, S. K. Energy-dependent polarity correction factors for four commercial ionization chambers used in electron dosimetry. Med Phys, v. 24, n. 5, p. 785-790, 1997.


Full Text: PDF

DOI: 10.15392/bjrs.v6i3.547

Refbacks

  • There are currently no refbacks.


Creative Commons License
This work is licensed under a Creative Commons Attribution 3.0 License.