AbstractID: 9489 Title: The Dose Sensitivity to Lung Motion in Optimized Plan for
IMPT, VHEET and IMXT.
The Dose Sensitivity to Lung Motion in Optimized Plan for IMPT,
VHEET and IMXT.
Tae Kyu Lee and George A. Sandison
School of Health Sciences, Purdue University, 550 Stadium Mall Drive, West Lafayette, IN 47907, USA
Abstract: A mathematical homogeneous phantom was defined to simulate the motion of a target as lung
size changes during the breathing cycle from full inspiration to full expiration. The dependence of dose
sensitivity for the target and lung was studied for intensity modulated proton therapy (IMPT), intensity
modulated very high-energy electron therapy (VHEET) and intensity modulated x-ray therapy (IMXT)
during lung motion. Other parameters studied were beam number and beam direction. It was assumed that
the plan was optimized for the lung size and target position at full inspiration. Of the three radiation types
studied the results show that IMPT is the most sensitive to the lung motion. For importance factors of
Itarget=500 and Ilung=10, we calculated the relative dose error due to breathing as the mean doses at full
inspiration to that at full expiration. Relative dose errors were 42 % (target) and 160 % (OAR) for IMPT,
23 % (target) and 47 % (OAR) for VHEET and 21 % (target) and 36 % (OAR) for IMXT. VHEET was
found to be more dose sensitive than IMXT. Sensitivity to the organ motion depends upon the physical
ability to localize the radiation on the assumed static position of the target.