The effect of intravenous contrast on photon radiation therapy dose calculations for lung cancer.

OBJECTIVE

The aim of this study was to evaluate the effect of intravenous contrast-enhanced computed tomography (CT) scans on the photon radiation dose calculations for lung cancer treatment planning.

MATERIALS AND METHODS

Nonionic iodinated intravenous contrast (Iohexol) was administered during the treatment planning CT scan of 9 patients with node-positive non-small-cell lung cancer (NSCLC). The potential effect of intravenous contrast was studied by changing the density of the contrast-enhanced vessels. A total of 9 patients were treated in this study: 5 patients with intensity-modulated radiation therapy (IMRT), and 4 patients with three-dimensional (3D) conformal radiation therapy. A treatment plan was generated from an unmanipulated "normal contrast" planning scan. The same planning parameters were then applied to a "no contrast" planning scan. The effect of intravenous contrast was quantified by calculating the percent change of dose in a variety of target and normal structures. To evaluate a worst-case scenario, the comparison between "normal contrast" and "no contrast" planning scans was repeated, assigning each vessel the artificial high density of 1.3 g/cm.

RESULTS

Dose differences between the planning image set using intravenous contrast and the image set without contrast were less than 2.5% for planning target volumes. A worst-case scenario in which normal contrast was overridden with an artificially high density of 1.3 g/cm led to small dose differences of less than 3%.

CONCLUSIONS

Planning lung radiation therapy treatment using CT scans that contain intravenous contrast does not result in clinically significant errors in dose delivery.