Source of Support: None, Conflict of Interest: None
This paper presents the suitability study of two thermo luminescence (TL) dosemeter systems for the measurement of central axis depth dose of Cobalt-60 and Mega voltage photon beams. The two TL systems used are IdF (TLD-100) chips and CaSO4 : Dy phosphor embedded PTFE discs. As the CaSO4 : Dy PTFE discs are locally made; the effect of energy dependence of these discs to high energy photons was also studied. The results obtained by these two systems viz TLD-100 and Caso4 : Dy were found to be reproducible and within + 1.5% and 1.3% respectively for Cobalt 60 energy and for 10 NV X-ray. The results were found to be within 4% when compared with BJR (supplement 11) values. This paper also includes the study of repeated use of CaSO4 : Dy PTFE disc for 10 cycles of reuse when exposed to the doses of the order of 200 R as is usually the case for such measurements. Table 1 presents the relative values of two TL systems compared to BJR values at a few depths in the phantom. Table - 1 C. A. D. D. values for 10x10 cm2 field size and 60 cm SSD for photon beams These results will be further discussed in detail during the presentation.