Off axis ratio from Beam Profiles can be matched by fine adjustments of PDD. Data from 10 different Varian LINACs were compared. Output factors and Wedge factors were within 1% if measured the same way. Data was also compared to Varian's Golden Beam Data.

AAPM 2009 poster presentation. Summary: Varian's Golden Beam Data is actually quite good, contrary to comments by many physicists. Data from 10 different Varian's high energy series linacs installed over 10 years were compared. Differences in LINAC profiles is correlated to minor PDD differences. Output factors and Wedge factors were within 1% if measured the same way. Many physicists do not CLEARLY document their method of measurement. The author has seen differences of up to 5% in wedge factors when measured under different set up conditions.