The purpose of study is to investigate whether glass rod detector (GRD) would be suitable for dosimeter of radiotherapy units. A GRD is used for the measurement of the output factors and x-axis beam profiles from Gamma Knife. The output factors measured with GRD from the 14, 8 and 4 mm collimators relative to the 18 mm collimator are 0.980+/-0.013, 0.949+/-0.013 and 0.872+/-0.012, respectively. The output factors obtained with a GRD are within 1.0% in good agreement with the values recommended by the manufacture. The full width at half maximum (FWHM) of x-axis beam profiles measured with GRD are 5.9 mm at a 4 mm collimator.
Glass* ; Radiotherapy

PURPOSE: To analyze the long-term stability of Farmer-type cylindrical ionization chambers by calibration factor provided from the KFDA (Korea Food Drug Administration) MATERIALS AND METHODS: The cylindrical ionization chambers used in this study were the PTW 30001 (30006), 30013, 30002, 30004, 23333, the Capintec PR06C, the NE 2571, the Exradin A12 and the Wellhofer FC65G (IC70). We were analyzed that the N(k) and N(D,W) calibration factor for the cylindrical chambers and compared between the measured N(D,W) and calculated N(D,W) calibration factor. RESULTS: We have observed that the long-term stability of the PTW 30013 (30006), the Wellhofer FC65G (IC70) and the NE 2571 has varied within 0.2%. The measured N(D,W) calibration factor was about 1.0% higher than the calculated N(D,W) that determined by the N(k) calibration factor. CONCLUSION: The study has evaluated that the long-term stability of the cylindrical chambers through analysis for the Nk and N(D,W) calibration factor. It has contributed to the improvement of clinical electron dosimetry in radiotherapy centers.
Calibration ; Radiotherapy