VALIDATION OF A BEAMNRC MONTE CARLO SIMULATION OF A BROAD BEAM DIAGNOSTIC X-RAY UNIT.

A BEAMnrc Monte Carlo simulation of a diagnostic X-ray unit in a broad beam geometry intended for the derivation of effective linear attenuation coefficients was validated against measurements made on the X-ray unit on which the simulation was based. The validation process assessed the size of the beam, the first and second half value layer, the variation in kerma with anode-heel effect and the accuracy of values of effective linear attenuation coefficient for water and solid water attenuators. The agreement between the simulated and measured results for all tests was consistently within the experimental uncertainty for the measurements. The average deviation between values of effective linear attenuation coefficient for simulated and measured results is 3.8%, with the highest individual deviation 7.1%. The simulation can be used to produce values of effective linear attenuation coefficient for a range of kVp, field size and attenuator thickness that are close to those measured.