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Table 1 Impact of flattening filter and arm backscatter corrections: percentage difference between PV-GLAaS measurements and Eclipse calculations relative doses at the 80% of the field size, for square and rectangular fields larger than 5 × 5 cm2; values are the average ± SD, and range; data for 6MV beam at dmax.

From: Testing the portal imager GLAaS algorithm for machine quality assurance

 

No correction [%]

Flattening filter correction [%]

Flatt.Filter + arm Backscatt. correction [%]

-x dir.

-1.9 ± 1.3 [-3.3, -0.1]

-0.2 ± 0.4 [-0.8, +0.3]

-0.2 ± 0.4 [-0.9, +0.3]

+x dir.

-1.9 ± 1.4 [-3.5, +0.1]

-0.2 ± 0.3 [-0.8, +0.1]

-0.2 ± 0.3 [-0.8, +0.0]

-y dir.

-1.7 ± 0.7 [-3.2, -0.5]

+0.6 ± 0.7 [-0.6, +1.8]

+0.5 ± 0.7 [-0.6, +1.7]

+y dir.

-4.2 ± 1.6 [-5.3, -0.3]

-1.8 ± 0.7 [-2.4, -0.3]

-0.2 ± 0.8 [-1.4, +1.2]