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Interplay effect
•
Total dose distribution relies on different areas of the target being
selectively exposed at different times
•
Intrafraction motion would lead to the dose accumulating in a different
distribution than planned
In reality, the interplay effect is rarely a problem:
•
Over many fractions the dose
05/04/2016
Court et al. MedPhys 2010
averages out
•
SABR: few fractions but longer
delivery times (e.g. more breathing
cycles)
•
Very heavily modulated plans,
single-arc VMAT
•
Avoid by limiting modulation