The experimental beam profile data from a 256 channel prototype cone beam computed tomography scanner were used to corroborate the theory for beam widths ranging from 28 mm up to 138 mm. The scatter component of the beam profile is based on a scatter LSF kernel derived from a Monte Carlo simulation, which, due to its simple form, can likewise be modeled analytically. A beam profile resulting from asymmetric collimation can be generated using the scatter LSF, and used to simulate helical protocols which asymmetrically reduce the aperture over the last ½ revolution or so to trim over-scanning. Even dose calculations involving shift-variant phantoms can be handled once the dependence of the scatter LSF on phantom diameter has been established.