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Figure 5. Planar dose distribution from an irregular block aperture computed using the small-field beam model (broken lines) compared with film measurement (solid lines). The large grid squares represent 2 cm. Both distributions are normalized on the central axis at the measurement depth (5 cm in water-equivalent material). The block shape has been digitized from the 50% isodose contour on the film in order to remove the uncertainties due to block production and light/radiation field disagreement.
