140-141 / 2953
UCLH strategy
Developed a process for CBCT based dosimetric review.
Use CBCT to modify CT – override HU numbers in CT.
Head and Neck IMRT – assess impact of weight loss (or
gain) though modifications to external contour.
Lung - override internal density changes if external shape
and positioning is good.
Limited ability to quantify impact of positional changes or
shifting internal anatomy.
Primary aim – assess need for rescan, replan, or revised
dose, if:
OAR tolerances likely to be exceeded.
PTV coverage not achieved.
Uncertainty is excessive.
7