A radiation treatment bra is disclosed. In the illustrative embodiment, the bra includes adjustable elements and a medial window. During radiation treatment planning, the elements are adjusted to establish a reference breast geometry. The reference breast geometry is reproduced prior to an actual treatment session by repeating the original adjustment of the elements, as necessary. The medial window enables a light field to be projected onto the patient's chest, and read therefrom, thereby establishing proper alignment of the patient to the radiation treatment machine.