INTERCOMPARISON PROGRAMME OF ABSORBED DOSE FOR MEGAVOLTAGE X-RAY TELETHERAPY UNITS IN MALAYSIA
The objective of this study is to perform a thermoluminescent dosimetry (TLD) postal dose quality audit for megavoltage X-ray teletherapy units in Malaysia. This audit is essential to be carried out to ensure adequate precision in the dosimetry of clinical beams before being delivered to the patients. Through this work, participating centres were requested to irradiate three capsules of TLD-100 powder with an absorbed dose to water of 2 Gy for 6 MV and 10 MV photon beams. The International Atomic Energy Agency (IAEA)’s Technical Report Series No. 398 is used as a reference standard for TLD irradiation. A total of 22 photon beams from ten radiotherapy centres comprising one government hospital and nine private medical centres were evaluated. The percentage deviation of user’s measured absorbed dose relative to Secondary Standard Dosimetry Laboratory (SSDL) mean absorbed dose was calculated. The results showed that all photon beams are within the IAEA’s acceptance limit of ± 5% except six photon beams. These centres were followed up with a second round of TLD irradiation which resulted in a better compliance. As a conclusion, regular audits should be performed to ensure consistency of radiotherapy treatment unit performances thus maintaining the accuracy of dose delivered to patients in all radiotherapy centres in Malaysia.