Thermoluminescence dosimetry for quality assurance in radiation therapy

A methodology based on thermoluminescence dosimetry was developed to check the output of teletherapy units and the given doses. It was applied in a hospital as a part of an extemal quality audit programme. Over a 7 year period the mean ratios of the output doses measured by TLDs calibrated free-in-air to the doses measured at the hospital in a 6 MV X ray and in a 60Co unit were 1.000 +/- 0.024 (n = 86) and 0.997 +/- 0.027 (n=61), respectively. TLDs in capsules were attached to the patient's body or to a phantom to assess entrance, exit and midline doses and transmission. Factors were determined experimentally to relate the doses measured with TLDs in capsules and inside the body. The accuracy in given doses with pelvic and tangential breast fields and assessed via 752 in vivo measurements, was considered to be adequately good, taking into account the limitations of the equipment available in the hospital.