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Gantry vs couch angle plots for treatment to the head, lung, abdomen, and prostate. The infeasible, standard STD beams are represented as red crosses and blue hollow circles, respectively. Extended STD beams are shown in black, separated into four categories: 100 < STD ⩽ 110, 110 < STD ⩽ 120, 120 < STD ⩽ 130, and STD > 130, represented as squares, triangles, diamonds, and plus signs.
