Long term response stability of a well-type ionization chamber used in calibration of high dose rate brachytherapy sources

• Main Authors: Vandana S, Sharma S
• Format: Article
• Language: English
• Published: Wolters Kluwer Medknow Publications 2010-01-01
• Series: Journal of Medical Physics
• Subjects: Brachytherapy; response stability; source calibration; well chamber
• Online Access: http://www.jmp.org.in/article.asp?issn=0971-6203;year=2010;volume=35;issue=2;spage=100;epage=103;aulast=Vandana

Well-type ionization chamber is often used to measure strength of brachytherapy sources. This study aims to check long term response stability of High Dose Rate (HDR) -1000 Plus well-type ionization chamber in terms of reference air kerma rate (RAKR) of a reference ¹³⁷ Cs brachytherapy source and recommend an optimum frequency of recalibration. An HDR-1000 Plus well-type ionization chamber, a reference ¹³⁷ Cs brachytherapy source (CDCSJ5), and a MAX-4000 electrometer were used in this study. The HDR-1000 Plus well-type chamber was calibrated in terms of reference air kerma rate by the Standards Laboratory of the International Atomic Energy Agency (IAEA), Vienna. The response of the chamber was verified at regular intervals over a period of eight years using the reference ¹³⁷ Cs source. All required correction factors were applied in the calculation of the RAKR of the ¹³⁷ Cs source. This study reveals that the response of the HDR-1000 Plus well-type chamber was well within ±0.5% for about three years after calibration/recalibration. However, it shows deviations larger than ±0.5% after three years of calibration/recalibration and the maximum variation in response of the chamber during an eight year period was 1.71%. The optimum frequency of recalibration of a high dose rate well-type chamber should be three years.