Air density dependence of the response of the PTW SourceCheck 4pi ionization chamber for 125I brachytherapy seeds. (June 2017)

• Record Type: Journal Article
• Authors: Torres del Río, J.; Tornero-López, A.M.; Guirado, D.; Pérez-Calatayud, J.; Lallena, A.M.
• Is Part Of: Physica medica. Volume 38(2017)
• Page Start: 93
• Page End: 97
• Publication Date: 2017-06
• Subjects: Brachytherapy -- Low-energy sources -- Ionization chamber -- Air density dependence -- PTW SourceCheck 4pi; Medical physics -- Periodicals; Biophysics -- Periodicals; Biophysics -- Periodicals; Imagerie médicale -- Périodiques; Radiothérapie -- Périodiques; Rayons X -- Sécurité -- Mesures -- Périodiques; Physique -- Périodiques; Médecine -- Périodiques; 610.153
• DOI: 10.1016/j.ejmp.2017.05.056
• Languages: English
• ISSNs: 1120-1797

Abstract

Highlights: Air density dependence of the response of the SourceCheck 4pi ionization chamber. Comparison with responses of HDR 1000 Plus and old SourceCheck ionization chambers. Verification of the linear dependence of the residual response on air density. Abstract: Purpose: To analyze the air density dependence of the response of the new SourceCheck 4pi ionization chamber, manufactured by PTW. Methods: The air density dependence of three different SourceCheck 4pi chambers was studied by measuring 125 I sources. Measurements were taken by varying the pressure from 746.6 to 986.6 hPa in a pressure chamber. Three different HDR 1000 Plus ionization chambers were also analyzed under similar conditions. A linear and a potential-like function of the air density were fitted to experimental data and their achievement in describing them was analyzed. Results: SourceCheck 4pi chamber response showed a residual dependence on the air density once the standard pressure and temperature factor was applied. The chamber response was overestimated when the air density was below that under normal atmospheric conditions. A similar dependence was found for the HDR 1000 Plus chambers analyzed. A linear function of the air density permitted a very good description of this residual dependence, better than with a potential function. No significant variability between the different specimens of the same chamber model studied was found. Conclusion: The effect of overestimation observed in the chamber responses once they are corrected for the standard pressure and temperature may represent a non-negligible ∼ 4 % overestimation in high altitude cities as ours (700 m AMSL). This overestimation behaves linearly with the air density in all cases analyzed.