PURPOSE: To test whether unified vendor specified beam conformance for matched machines implies volumetric modulated arc radiotherapy(VMAT) delivery consistency. METHODS: Twenty-two identical @entity1 QA plans, eleven 6MV and eleven 15MV, were delivered to the Delta   (Scandidos, Uppsala, Sweden) on two Varian TrueBEAM matched machines. Sixteen @entity1 QA plans, nine 6 MV and seven 10 MV, were delivered to Delta    on two Elekta Agility matched machines. The percent dose deviation(%DDev), distance-to-agreement( @entity11510 ), and the gamma analysis(y) were collected for all plans and the differences in measurements were tabulated between matched machines. A paired t-test analysis of the data with an alpha of 0.05 determines statistical significance. Power(P) was calculated to detect a difference of 5%; all data except Elekta %DDev sets were strong with above a 0.85 power. RESULTS: The average differences for Varian machines (%DDev, @entity11510 , and y) are 6.4%, 1.6% and 2.7% for 6MV, respectively, and 8.0%, 0.6%, and 2.5% for 15MV. The average differences for matched Elekta machines (%DDev, @entity11510 , and y) are 10.2%, 0.6% and 0.9% for 6 MV, respectively, and 7.0%, 1.9%, and 2.8% for 10MV.A paired t-test shows for Varian the %DDev difference is significant for 6MV and 15MV(p-value6MV=0.019, P6MV=0.96; p-value15MV=0.0003, P15MV=0.86). Differences in @entity11510 are insignificant for both 6MV and 15MV(p-value6MV=0.063, P6MV=1; p-value15MV=0.907, P15MV=1). Varian differences in gamma are significant for both energies(p-value6MV=0.025, P6MV=0.99; p-value15MV=0.013, P15MV=1). A paired t-test shows for Elekta the difference in %DDev is significant for 6MV but not 10MV(p-value6MV=0.00065, P6MV=0.68; p-value10MV=0.262, P10MV=0.39). Differences in @entity11510 are statistically insignificant(p-value6MV=0.803, P6MV = 1; p-value10MV=0.269, P10MV=1). Elekta differences in gamma are significant for 10MV only(p-value6MV=0.094, P6MV=1; p-value10MV=0.011, P10MV=1). CONCLUSION: These results show vendor specified beam conformance across machines does not ensure equivalent @entity1 specific QA pass rates. Gamma differences are statistically significant in three of the four comparisons for two pairs of vendor matched machines.

SU-E-T-116: Analysis of XXXX Specific VMAT QA Passing Rates with Delta4 for Matched Machines.

@entity1 :: ('9606', 'Species') :: ['patient'] @entity11510 :: ('MESH:C042899', 'Chemical') :: ['DTA']
@entity1 :: (9606,Species) :: ['Patient']
