The effects of intravenous contrast agent on two different 3D
conformal radiotherapy treatment planning systems with different
algorithms were studied.
METHODS
Contrast-enhanced and non-contrast computed tomography
(CT) data sets belonging to a lung cancer patients were studied
with XiO (CMS) and Eclipse™ (Varian). The convolution,
Clarkson, fast superposition and standard superposition
algorithms of XiO and modified Batho, Batho power law and
equivalent TAR algorithms of Eclipse were studied with different
field sizes and angles. The correlations between the
changes of monitor units (MU) with both field sizes and total
Hounsfield unit (HU) changes were investigated.
RESULTS
The mean MU change was +1.3% (-1% to +3.2%). There was
a strong linear correlation between HU and MU changes of
XiO algorithms (r2=0.79) and no correlation in Eclipse.
CONCLUSION
Although 3D planning of the lung could be done with contrasted
CT dataset, according to our findings, it should ideally
be planned with non-contrast CT fusing with created volumes
in contrasted ones.
Keywords: Lung cancer; contrast agent, treatment planning system; 3D radiotherapy
