Comparison of dosimeter response of TLD-100 and ionization chamber for high energy photon beams at KIRAN Karachi in Pakistan

This study was conducted by measuring point dose at different depths of water phantom by using two types of dosimeters (PTW N30013 ionization chamber and TLD-100 chips) at Karachi institute of radiotherapy and nuclear medicine (KIRAN), Pakistan. Two different TLD chips were used (circular pallets and square chips). The main aim of this study was to compare the responses of two different types of dosimeter irradiated with 6 MV X-rays using same parameters. Both types of dosimeter were irradiated with different dose value ranging from 25 cGy to 500 cGy. The deviation between different shapes of TLD and ionization chamber remained within 5% limit. Maximum deviations of circular pallets reading from that of ion chamber are 3.56% at 1.5 cm depth and 4.91% at 5 cm depth. For square chips maximum deviation happened to be 4.38% at 1.5 cm depth and 4.23% at 5 cm depth. This measurement shows that TLDs are reliable tool for dosimetry regardless of their shape or manufacturer and they can be used as re-validation tool for ion chamber dosimetry.