Source of Support: None, Conflict of Interest: None
The air kerma measurements for brachytherapy sources are generally recommended to be done at one meter using large volume chambers. These measurements pose problems due to low signal from brachytherapy sources. Non-availability of calibrated large volume chambers at a hospital adds to the problem of air kerma measurements. Therefore, the use of commonly available secondary standard dosimeter having 0.6 cc chamber has been examined. Correction factors to be applied at small source to chamber distances have been determined. Measurements from Cs-137 source of nominal activity as low as 1 .11 GBq (30 mCi) could be carried ' out using an integration time of about 20 minutes at minimum distance of 1.5 cm. For source to chamber distance beyond 5 cm, the correction factor approaches unity.