Quantification of the fluence error in the motion-compensated dynamic MLC (DMLC) technique for delivering intensity-modulated radiotherapy (IMRT).

When a correction for intrafraction organ motion is to be attempted using the dynamic multileaf collimator (DMLC) 'breathing leaves' technique for intensity-modulated radiotherapy (IMRT), there is a finite response time between the measurement of organ motion and the feeding of a corresponding corrective motion to the leaves. Whilst small this is non-zero. This letter presents a computational strategy to assess the error introduced to the delivered fluence by this system latency. The error depends on the functional form of the intended fluence modulation, the variability of the breathing motion and the magnitude of the system latency.