Dosimetry for the pelvis, head and neck of radiotherapied patients with TLD

Objective: To explore the measurement method of the treatment dose of the patient with TLD chip for photon beam in radiotherapy, and validate the treatment dose by comparing with the treatment plan system (TPS), in order to decide if the relative deviation is within ±5% between two methods. Methods: The experiment of the dispersion, the reproducibility, the fading and non-linearity dose response with TLD in 60Co γ and 6 MV beams were carried out. According to need of clinic treatment different conditions were choose to observe the dose changes with the field size, distance of source to skin, angle of incidence, energy response, wedge angle, block and tray using ionization chamber and water phantom. The TLDs were placed on the surface of solid phantom and the correction factors were obtained. Doses of the pelvis, head and neck were verified with the Alderson phantom and TLD. TLD doses of the pelvis, head and neck on 356 points of the patients that performed radiotherapy were measured. Results: If the TLDs were irradiated on the points on the Alderson phantom, such as AP, RL and LL of the pelvis, with and without wedges, RL and LL junction of the neck and chin, with and without a mask, the relative deviation of doses is within ±3.7% between TLD and TPS. Conclusions: The TLD method is reliable for measuring the exposure doses of the patient performed radiotherapy. It is also accuracy and economical, and it is approved by IAEA as a method for quality assurance, so that it is deserve to use the TLD measurement for patient performed radiotherapy. (authors)