A., Whitehurst, P., Cooper, P., Hounsell, A. J., Air kerma calibration factors and chamber correction values for PTW soft x-ray, NACP and Roos ionisation chambers at very low x-ray energies, Phys. Seuntjens (Eds.), Proceedings, Medical Physics Publishing, Madison, 1999. Phys., 28:868–893, 2001.Īllen Li, X., Ma, C-M., Salhani, D., Relative dosimetry measurement for kilovoltage x-ray units, in Kilovoltage x-ray beam dosimetry for radiotherapy and radiobiology C-M Ma and J.P. 398, International Atomic Energy Agency, Vienna, 2000.ĪAPM TG 61, AAPM protocol for 40–300 kV x-ray beam dosimetry in radiotherapy and radiobiology, Med. IAEA TRS 398, Absorbed Dose Determination in External Beam Radiotherapy Technical Report Series no. IPEMB 1996, The IPEMB code of practice for the determination of absorbed dose for x-rays below 300 kV generating potential (0.035 m Al - 4 mm Cu HVL 10 –300 kV generating potential), Phys. Measurements indicated that the Markus chamber had an energy dependent response in the kilovoltage range, which could account for the discrepancy in output factor measurement. A PTW Markus chamber was found to compare well with a NE 2532/3 low energy chamber in percentage depth dose measurement, but discrepancies arose between the chambers in output factor measurements, up to 5% for small field sizes. Larger measurement discrepancies were found for Plastic Water and Perspex. Solid water proved a useful water-equivalent phantom material with discrepancies between measurements in water and solid water less than 2.3% for percentage depth dose and less than 0.6% for output factors. A variety of phantom materials and two ionisation chambers were tested for their suitability in output factor and percentage depth dose measurement. Output factors at the surface for treatment cones and lead cut-outs have been measured for a Pantak Therapax SXT 150 superficial therapy unit with x-ray beam qualities from 1 to 13 mm Al HVL.
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