Kilo-Voltage X-Ray Correction Factors for In-Water Measurements Based on TG-61

For x-ray tube potentials 100 kV, the AAPM TG-61 protocol for 40-300 kV x-ray beam dosimetry in radiotherapy recommends an in-water measurement which is based on ionization chambers calibrated in air in terms of air kerma. The variation of the overall correction factor (PQ;cham) and its components (known as corrections for the change in the chamber response due to the change in the spectrum distribution in phantom compared to that used for the calibration free in-air (PE;), displacement of water by the ionization chamber (Pdis) and correction due to the stem for in-water measurement relative to the free in-air calibration (Pstem;w)) were studied with depth and field size for 6 different beam qualities in the orthovoltage x-ray range (100 kV tube potential 300 kV). The NE2571 ion chamber, Exradin A16 ion chamber, and Exradin W1 plastic scintillator were considered in this thesis. The last two detectors are not included in the TG-61 protocol.