Effects of aperture angle of a fluorescence meter on scatter-to-primary ratio. Monte Carlo calculation studies

The effect of the aperture angle of a fluorescence meter on the scatter-to-primary ratio (SPR) was examined. The Monte Carlo program was developed and implemented to simulate an x-ray photon transport. We simulated a situation with divergent beam and x-ray spectra between 40 kV and 150 kV incident on water slabs. The dependence of SPR on tube potential, scatter thickness, and aperture angle was reported as energy-deposition in the phosphor layer. In addition, the average exit angle of scattered photons reaching the phosphor plane was scrutinized. Results indicated that the aperture angle of a fluorescence meter had an effect on SPR. Further, SPR was found to depend on the type of screen phosphor, whereas aperture angle made less difference. (author)