Determination of N(pp)(gas) and N(pp)(D) for a plane-parallel chamber.

The purpose of this work is to investigate the consistency of determining N(pp)(gas) and N(pp)(D) by using three independent calibration methods from the AAPM TG 39 and IAEA TRS 381 protocols: 1) calibration with a high-energy electron beam in a phantom; 2) in-phantom calibration in a (60)Co beam; and 3) in-air calibration in a (60)Co beam. The plane-parallel chamber considered was the PTW-Markus and the comparisons were made against a calibrated PTW cylindrical Farmer-type chamber 30001. The phantom material used for the electron beam and (60)Co in-phantom methods was a solid water phantom (RW3).