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Figure 2 :(a) Beam and phantom geometries for calculations of %DD data for 2x2 cm2 beamlets of Co-60, 6 MV and 15 MV for conditions A, B, C and D (the external dimensions of the water phantom are truncated and the distances are not to scale). Figures (b), (c) and (d) show the %DD data along the central axis (CAX) of the beamlet for all four conditions. The locations of the CAX, in relation to the air-water interfaces, are represented by the vertical dashed lines.

Figure 2 :(a) Beam and phantom geometries for calculations of %DD data for 2x2 cm2 beamlets of Co-60, 6 MV and 15 MV for conditions A, B, C and D (the external dimensions of the water phantom are truncated and the distances are not to scale). Figures (b), (c) and (d) show the %DD data along the central axis (CAX) of the beamlet for all four conditions. The locations of the CAX, in relation to the air-water interfaces, are represented by the vertical dashed lines.