A post-mastectomy chest wall plan uses a 6 MV beam with a physical wedge, a cerrobend block mounted on the tray, and daily bolus over the scar. The open-field output factor was measured in water for the same field size, and the tray/block and bolus effects are accounted for separately. Which correction accounts for adding the wedge when determining the wedged-field central-axis output?

An open-field output factor does not include the attenuation caused by a physical wedge. The wedge transmission factor is the ratio of dose with the wedge in place to dose without it at the same field size and measurement conditions; applying it accounts for the wedge’s effect on central-axis output. The tray transmission factor addresses attenuation by the block and tray, which the question says is accounted for separately. Bolus affects the dose distribution near the surface, while a lung inhomogeneity factor addresses dose changes due to patient tissue density; neither accounts for adding the wedge. Wedge factors depend on measurement conditions, so use the appropriate value for the field and wedge orientation.