Brachytherapy is the clinical use of small encapsulated radioactive sources at a short distance from the target volume for irradiation of malignant/benign tumours. In the past few decades high dose rate (HDR) brachytherapy has been developed as an alternative to low dose rate (LDR) brachytherapy. AAPM TG 43 has recommended a new protocol for dosimetry of brachytherapy sources. As per the recommended formalism, the dose to a point can be calculated from the numerical values of measurable parameters, dose rate constant, A, radial dose function, g(r), and anisotropy function, F(r,0). It has also been recommended that for the specification of the dose rate constant as well as relative dose distribution parameters liquid water be accepted as reference medium. So far, measurements of recommended dosimetry parameters of HDR192Ir sources have been reported in solid phantom materials only. We have carried out the experimental measurements of dose rate constant and radial dose function for microselectron HDR 192Ir source (dia. 1.1 mm and length 5.0 mm) in a specially designed and locally fabricated water phantom using single sensitive layer radiochromic film (Gafchromic HS). The relative depth dose (RDD) for the microselectron HDR 192Ir source was also measured using radiochromic film in water phantom to verify the RDD calculated using the brachytherapy treatment planning system (TPS). The experimentally measured values of A and g(r) for microselectron HDR192ir source are found to be in good agreement to the experimental and Monte Carlo calculated values reported in the literature for the same source within the uncertainty of measurement. The measured and TPS calculated values of RDD are also in excellent agreement to each other. This experimental study, therefore, demonstrates the suitability of radiochromic film for dosimetry of HDR 1921r source is in liquid water.
Dosimetry Along Transverse Axis of HDR Ir-192 Source in Liquid Water using High Sensivity Radiochromic Film
PERNA, LUCIA ALESSIA;SAMPIETRO, CHIARA;NOVARIO, RAFFAELE;CONTE, LEOPOLDO
2003-01-01
Abstract
Brachytherapy is the clinical use of small encapsulated radioactive sources at a short distance from the target volume for irradiation of malignant/benign tumours. In the past few decades high dose rate (HDR) brachytherapy has been developed as an alternative to low dose rate (LDR) brachytherapy. AAPM TG 43 has recommended a new protocol for dosimetry of brachytherapy sources. As per the recommended formalism, the dose to a point can be calculated from the numerical values of measurable parameters, dose rate constant, A, radial dose function, g(r), and anisotropy function, F(r,0). It has also been recommended that for the specification of the dose rate constant as well as relative dose distribution parameters liquid water be accepted as reference medium. So far, measurements of recommended dosimetry parameters of HDR192Ir sources have been reported in solid phantom materials only. We have carried out the experimental measurements of dose rate constant and radial dose function for microselectron HDR 192Ir source (dia. 1.1 mm and length 5.0 mm) in a specially designed and locally fabricated water phantom using single sensitive layer radiochromic film (Gafchromic HS). The relative depth dose (RDD) for the microselectron HDR 192Ir source was also measured using radiochromic film in water phantom to verify the RDD calculated using the brachytherapy treatment planning system (TPS). The experimentally measured values of A and g(r) for microselectron HDR192ir source are found to be in good agreement to the experimental and Monte Carlo calculated values reported in the literature for the same source within the uncertainty of measurement. The measured and TPS calculated values of RDD are also in excellent agreement to each other. This experimental study, therefore, demonstrates the suitability of radiochromic film for dosimetry of HDR 1921r source is in liquid water.
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