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

BACKGROUND

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.