Influence of the intravenous contrast media on treatment planning dose calculations of lower esophageal and rectal cancers

The impact of intravenous (IV) contrast media (CM) on radiation dose calculations must be taken into account in
treatment planning.
Purpose: The aim of this study is to evaluate the effect of an intravenous contrast media on dose calculations in three‑dimensional
conformal radiation therapy (3D‑CRT) for lower esophageal and rectal cancers.
Materials and Methods: Seventeen patients with lower esophageal tumors and 12 patients with rectal cancers were analyzed. At the
outset, all patients were planned for 3D‑CRT based on the computed tomography (CT) scans with IV contrast media. Subsequently,
all the plans were copied and replaced on the scans without intravenous CM. The radiation doses calculated from the two sets of
CTs were compared.
Results: The dose differences between the planning image set using intravenous contrast and the image set without contrast
showed an average increase in Monitor Units (MUs) in the lower esophageal region that was 1.28 and 0.75% for 6 and 15 MV
photon beams, respectively.
Conclusion: There was no statistical significant difference in the rectal region between the two sets of scans in the 3D‑CRT plans.
The results showed that the dose differences between the plans for the CT scans with and without CM were small and clinically
tolerable. However, the differences in the lower esophageal region were significant in the statistical analysis.