IAEA/WHO TLD Postal Dose Audit Service and High Precision Measurements for Radiotherapy Level Dosimetry

Abstract

Since 1969 the International Atomic Energy Agency (IAEA), together with the World Health Organization (WHO), has performed postal TLD audits to verify calibration of radiotherapy beams in developing countries. The TLD programme also monitors activities of Secondary Standard Dosimetry Laboratories (SSDLs). The programme has checked approximately 4000 clinical beams in over 1100 hospitals. and in many instances significant errors have been detected in the beam calibration. Subsequent follow-up actions help to resolve the discrepancies, thus preventing further mistreatment of patients. The audits for SSDLs check the implementation of the dosimetry protocol in order to assure proper dissemination of dosimetry standards to the end-users. The TLD audit results for SSDLs show good consistency in the basic dosimetry worldwide. New TLD procedures and equipment have recently been introduced by the IAEA that include a modified TLD calibration methodology and computerised tools for automation of dose calculation from TLD readings.

Advantages and disadvantages of luminescence dosimetry

“…In the frame of IAEA-WHO postal dose comparison service for cobalt-60 and MV X-rays beams, LiF TL dosemeters are irradiated under specified conditions in a simplified water phantom at the participating radiotherapy centre and returned to the IAEA's Dosimetry Laboratory for evaluation. The TL dosemeters are black polyethylene capsules of 20 mm inner length, 3 mm inner diameter, filled with approximately 155 mg of TLD powder (Izewska et al, 2002). Several corrections for dose dependence, energy dependence (for MV X-rays) and fading are applied to increase accuracy.…”

“…The stability of the reader is controlled using uniformly irradiated TLD powder from a large amount of powder stored for several years to minimize the influence of fading. The accuracy of the a measurement can be better that 1% but the overall extended uncertainty of the method, including calibration is at the level of 2% (Izewska et al, 2002). Such results can be achieved only in laboratories which use strict operational procedures and have access to highly skilled staff, since many operations are performed manually and require good working experience.…”

Verification of the pure alanine in PMMA tube dosimeter applicability for dosimetry of radiotherapy photon beams: a feasibility study

“…Currently, the dosimeter size is comparable to that of the thermoluminescence dosimeter (TLD) of LiF powder in polyethylene tube. This type of TLD has been long used for audits to verify radiotherapy beams through a service operated by the International Atomic Energy Agency (IAEA)/World Health Organization (WHO) TLD postal dose audit program [20].…”

A system for remote dosimetry audit of 3D-CRT, IMRT and VMAT based on lithium formate dosimetry

“…The two largest audit networks are currently operated by the IAEA [1,2] and the Imaging and Radiation Oncology Core Huston (IROC Huston) [3].…”