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OFF-AXIS RATIOS
•
Multiply orthogonal factors
•
Interpolate
–
Between depths
–
Between field sizes
•
Radial non-flatness is over-accentuated
–
Non-flatness due to
•
Scatter
•
Deliberate effect to compensate for beam softening at
depth
•
Apply radial correction
y
x
OAR
OAR
OAR
ESTRO physics course,
June 2017