Measurement of the strength of high dose rate brachytherapy sources using two different techniques

OBJECTIVES

The isotope ¹⁹²Ir is frequently used in high dose rate
brachytherapy sources. The short half-life of ¹⁹²Ir source compels
the user to change the source at every interval of four to
five months. A large uncertainty (±5%) in the source strength
quoted by the supplier requires an independent calibration by
the users. In this study, we compared the manufacturer's certificate
source strength and the source strength as measured
using two different techniques.

METHODS

We performed our measurements on Gammamed 12-i
brachytherapy unit for 10 sources in our clinic. The calibration jig
and cylindrical phantom were used to determine source strength.
Measurements were compared with the certificated values.

RESULTS

The difference between the calibration jig and cylindrical
phantom measurement methods for source strength was
between 0.1-4.2%. The results for the 10 sources showed a
difference in source strength between the certificates and our
measure of 0.6-3.9%.

CONCLUSION

According to our results, there was accordance between all
measurements.

Keywords: Source strength; HDR brachytherapy; quality control