Example on how the collimation measurements were calculated. The area of the large yellow box shows the actual collimation as area of the small yellow box shows the optimal collimation. The classifications—small: well-collimated, medium: fairly collimated, and large: poorly collimated—were calculated on the absolute difference in area between these two measurements, i.e., Actual collimation (mm2)—optimal collimation (mm2), using the ranges 0–1,800 mm2, 1,800–2,700 mm2, and 2,700–4,400 mm2, respectively.