Physics Bucharest 2017

IMRT: What are the Potential Weak Links?

 Many (small) field segments are made by the MLC for building a dose distribution  Leaf positioning and travelling becomes important  Dose calculations are more complex due to leaf rounding effects, tongue and groove effects, leaf transmission …  Small-field dosimetry (output factor and beam profiles) becomes important  Beam stability (segmented IMRT)  Low MU fields lead to short beam-on times  Check output, flatness, and symmetry stability at start up and steady state of the dose delivery  For > 2 MU dose output and beam profile stability should be within ± 2% (1 SD)

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