Abstract
The aim of this project is to do comparative study in calibrating Ir-192 source using well ionization chamber and air measurement using Farmer ionization chamber. To calibrate the Ir-192 using well ionization chamber, the HDR unit was programmed so that the source was at the most sensitive position inside the well-chamber. The charges were measured at 45 second time interval two times using the electrometer operated at +300V and -300V. Sources air kerma strength was determined based on the AAPM task group 43 brachytherapy dosimetry protocol. In the in-air method using the Farmer ionization chamber and calibration jig, the HDR unit was programmed so that the source was at the position that gave the maximum response in the catheter. The source air kerma strength was calculated using a formula proposed by Goestch et al, (1991). The Ir-192 source air kerma strength by the well chamber was 2.7780cGym2/h while in the in-air measurement was 2.609cGym2/h. Both results are less than 3% from the source strength written in the calibration certificate. The well chamber method is quite direct and less time consuming compare to the in-air measurement and this is the method utilised in HUSM.
Highlights
Brachy is from a G reek word for “short”, so brachytherapy means short distance therapy
[1] In clinical work, brachytherapy is the used of sealed radioactive sources which is places close proximity to the treatment target volume. 192Ir is commonly radioactive sources for high dose rate brachytherapy
The strength of a brachytherapy source may be specified in terms of activity, exposure rate at a s pecified distance, equivalent mass of radium, apparent activity, or air kerma strength
Summary
Brachy is from a G reek word for “short”, so brachytherapy means short distance therapy. [1] In clinical work, brachytherapy is the used of sealed radioactive sources which is places close proximity to the treatment target volume. 192Ir is commonly radioactive sources for high dose rate brachytherapy. Brachy is from a G reek word for “short”, so brachytherapy means short distance therapy. [1] In clinical work, brachytherapy is the used of sealed radioactive sources which is places close proximity to the treatment target volume. This is because 192Ir is an economical and safe especially when the patient load is high. The strength of a brachytherapy source may be specified in terms of activity, exposure rate at a s pecified distance, equivalent mass of radium, apparent activity, or air kerma strength
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