In order to find the difference between the calibration curves, the calibration curve measured at depth 20 cm and field size of 33 cm2 was used for comparison. Table5.1.2 shows the result of calibration curve’s comparison in dose range from 20 to 120 cGy.They are almost the same except calibration curve obtained from depth of 1.5 cm and field size of 11 cm2. The maximum difference is 8% .Therefore the ranges of both depths and field sizes in this study are independent to the calibration curve or to the EDR2 film response.