The effect of movement on optimized IMRT dose distributions

Patient motion can result in dose distributions not being delivered as intended. This is particularly important for IMRT treatments which have sharp gradients at the edge of the target volumes and often use reduced margins. In this study the authors have considered the effect on the resulting dose distribution of random motion applied to the beam positions after optimisation. These dose distributions show a loss in dose delivered to the tumour and an increase in dose delivered to the critical structures even when the random motion is averaged over a series of treatments as would occur clinically