In this paper, we report the dosimetry methodology used in the IAEA/WHO Thermoluminescent Dosimeter (TLD) Postal Dose Quality Audit Service and the results of 22 Malaysian radiotherapy centres participated in the audit from 2011 to 2015. Each participating centre was provided with a few sets of TLD capsule (two unit of TLD capsules to be irradiated and a control TLD in one set) as requested by the centres. The participating centres were asked to irradiate each TLD capsule at 2 Gy absorbed a dose to water under reference conditions i.e the TLD capsule is positioned at 10 cm depths in water, at central axis with 10 cm x 10 cm field size at 100 cm Source-Surface Distance or 100 cm Source-Axis Distance. In this period, a total of 70 photon beams consist of 43 beams and 27 beams produced by 6 MV and 10 MV photon beams, respectively have been audited. The results demonstrated that all participating centres comply with the acceptance limits of ± 5% as recommended by the International Commission on Radiation Units and Measurements (ICRU) Report 24, except eight photon beams from six centres. However, these centres presented better compliance results after being followed up with a second round of TLD irradiation.
The assessment of surface dose is essential in radiotherapy to avoid deterministic effect or to
reduce the severity of side effects from radiation treatment. In this study, the surface dose for breast
cancer radiotherapy was measured using two types of dosimeter; Thermoluminescent Dosimeter
(TLD) and Optically Stimulated Luminescent Dosimeter (OSLD). The study was performed on the
left breast of female Alderson Radiation Therapy (ART) phantom. The treatment planning was
carried out on the ART phantom to determine the homogeneity of dose distribution within the target
organ is complied with the tolerance limits of 95% to 107% as recommended by the International
Commission on Radiation Units and Measurements (ICRU)’s Report No. 50. From the treatment
planning result, the phantom then was irradiated with 267 cGy dose per fraction for two beam
fields; medial tangential and lateral tangential fields using a 6 MV photon beam produced from
three-dimensional (3D) conformal radiotherapy. Result shows that the OSLD provides 25.7% and
23.5% higher surface dose compared to TLD for medial tangential and lateral tangential fields,
respectively. This condition may be due to higher effective point of measurement and angular
dependence of the OSLD compared to TLD. As a conclusion, suitable dosimeter should be selected
to ensure accurate estimation of surface dose could be made thus reduction of skin reaction to
patient could be achieved.
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 6MV and10MV photon beams. The International Atomic Energy Agency (IAEA)’s Technical Report Series No. 398 is used as a reference standard for TLD irradiation. Atotal of 22photon beamsfrom ten radiotherapy centres comprising onegovernment hospital and nineprivate 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 inall radiotherapy centres in Malaysia.