A 2 cm gap width proved optimal and clinically relevant for comparing dose profiles.
Previous studies have shown that dose errors are inversely proportional to gap width; thus larger gaps will lead to a smaller dose discrepancy for the same leaf position error.
A dose error of less than 5% is marginally acceptable clinically and as seen in Fig. 8 of Losasso et al.,a 2 cm gap with an error of 1 mm would foreshadow a 5% dose error