Evaluation of a plane-parallel ionization chamber for low-energy radiotherapy beams
DOI:
https://doi.org/10.15392/bjrs.v3i1A.62Abstract
A plane-parallel ionization chamber, with a sensitive volume of 6.3 cm3, developed at the Calibration Laboratory of IPEN (LCI), was utilized to verify the possibility of its application in low-energy X-ray beam qualities for radiotherapy (T-qualities). This homemade ion chamber was manufactured using polymethyl methacrylate (PMMA) coated with graphite, and co-axial cables. In order to evaluate the performance of this ionization chamber, some characterization tests were performed: short- and medium-term stability, leakage current, saturation, ion collection efficiency, polarity effect and linearity of response. The maximum value obtained in the short-term stability test was 0.2%, in accordance with the limit value of 0.3% provided by the IEC 60731 standard. The saturation curve was obtained varying the applied voltage from -400 V to +400 V, in steps of 50 V, using the charge collecting time of 20 s. From the saturation curve two other characteristics were analyzed: the polarity effect and the ion collection efficiency, with results within the international recommendations. The leakage current of the ionization chamber was measured in time intervals of 20 minutes, before and after its irradiations, and all the results obtained were in agreement with the IEC 60731 standard. The linearity of response was verified utilizing the T-50(b) radiation quality, and the ionization chamber was exposed to different air kerma rates. The response of the ionization chamber presented a linear behavior. Therefore, all results were considered satisfactory, within international recommendations, indicating that this homemade ionization chamber presents potential routine use in dosimetry of low-energy radiotherapy beams.
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References
HORTON, J. L. Handbook of radiation therapy physics, Englewood Cliffs, N. J: Prentice-Hall, 1987.
MA, C.M.; COFFEY, C. W.; DEWERD, L. A.; LIU, C.; NATH, R.; SELTZER, S. M.; SEUNTJENS, J. P. AAPM protocol for 40–300 kV X-ray beam dosimetry in radiotherapy and radiobiology. Med Phys, v. 28(6), p. 868–892, 2001.
MALINVERNI, G.; STASI, M.; BAIOTTO, B.; GIORDANA, C.; SCIELZO, G.; GABRIELE, P. Clinical application and dosimetric calibration procedure of the superficial and orthovoltage therapy unit Therapax DXT300. Tumori, v. 88(4), p. 331–337, 2002.
DOBELBOWER, R. R.; MITSUYUKI, A. Intraoperative Radiation Therapy, Boca Raton, FL: CRC Press, 1989.
KRAUS-TIEFENBACHER, U.; SCHEDA, A.; STEIL, V.; HERMANN, B.; KEHRER, T.; BAUER, L.; MELCHERT, F.; WENZ, F. Intraoperative radiotherapy (IORT) for breast cancer using the Intrabeam system. Tumori, v. 91(4), p. 339– 345, 2005.
WENZ, F.; BLANK, E.; WELZEL, G.; HOFMANN, F.; ASTOR, D. ; NEUMAIER, C.; HERSKIND, C.; GERHARDT, A.; SUETTERLIN, M.; KRAUS-TIEFENBACHER, U. In-traoperative radiotherapy during breast-conserving surgery using a miniature Xray generator (Intrabeam): theoretical and experimental background and clinical experience. Women’s Health, v. 8(1), p. 39–47, 2012.
LEUNG, M. K. K.; CHOW, J. C. L.; CHITHRANI, B. D.; LEE, M. J. G.; OMS, B.; JAFFRAY, D. A. Irradiation of gold nanoparticles by X-rays: Monte Carlo simulation of dose enhancements and the spatial properties of the secondary electrons production Med Phys, v. 38(2), p. 624–631, 2011.
MA, C.-M. X-ray therapy equipment, low and medium energy, in Encyclopedia of Medical Devices and Instrumentation, 2nd ed. New Jersey: John Wiley & Sons, p. 580–590, 2006.
KHAN, F. M. The Physics of Radiation Therapy. 1st ed. Baltimore: Willians & Wilkins, 1984.
PODGORSAK, E. B. Radiation Oncology Physics: A Handbook for Teachers and Stu-dents. Vienna: International Atomic Energy Agency, 2005.
PERINI, A.P.; NEVES, L.P.; VIVOLO, V.; XAVIER, M.; KHOURY, H.J. ; CALDAS, L.V.E. Characterization of a CT ionization chamber for radiation field mapping. Appl Radiat Isot, v. 70, p. 1300-1303, 2012.
PERINI, A.P.; NEVES, L.P.; FERNÁNDEZ-VAREA, J. M.; CASSOLA, V.; 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, pp. 106-108, 2014.
BIPM - Bureau International des Poides at Mesures.
Measuring conditions used for the calibration of ionization chambers at the BIPM. BIPM Rapport BIPM-04/17, Sèvres: BIPM, 2004.
IEC - International Electrotechnical Commission. Medical electrical equipment - Dosime-ters with ionization chamber as used in radiotherapy. IEC Standard 60731, Genève: IEC, 2011.
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, 2001.
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