A simulation study of irregular respiratory motion and its dosimetric impact on XXXX .

@entity1 @entity2
This study is aimed at providing a dosimetric evaluation of the irregular motion of @entity2 due to variations in @entity1 ' respiration. Twenty-three @entity2 @entity1 are retrospectively enrolled in this study. The motion of the @entity1 clinical target volume is simulated and two types of irregularities are defined: characteristic and uncharacteristic motions. Characteristic irregularities are representative of random fluctuations in the observed target motion. Uncharacteristic irregular motion is classified as systematic errors in determination of the target motion during the planning session. Respiratory traces from measurement of @entity1 abdominal motion are also used for the target motion simulations. Characteristic irregular motion was observed to cause minimal changes in target dosimetry with the largest effect of 2.5%    0.9% (1  ) reduction in the minimum target dose (D(min)) observed for targets that move 2 cm on average and exhibiting 50% amplitude variations within a session. However, uncharacteristic irregular motion introduced more drastic changes in the clinical target volume (CTV) dose; 4.1%    1.7% reduction for 1 cm motion and 9.6%    1.7% drop for 2 cm. In simulations with @entity1 ' abdominal motion, corresponding changes in target dosimetry were observed to be negligible (<0.1%). Only uncharacteristic irregular motion was identified as a clinically significant source of dosimetric uncertainty.
