Scatter rejection by air gaps: an empirical model.

Scatter rejection by air gaps was analyzed in the context of a model in which scattered radiation was treated as if it originated from an "effective scatter point source" (ESPS), located between the focal spot of the x-ray tube and the exit surface of the phantom or patient. Excellent agreement was found between the ESPS model and scatter measurements performed on phantoms for a variety of experimental conditions. Values for Xs (distance from phantom exit surface to effective scatter point source) were consistently in the range 15-20 cm. Applications of the model for predictions of scatter rejection by air gaps and comparisons to other scatter rejection methods are presented.