The effect of intravenous contrast on intensity-modulated radiation therapy dose calculations for head and neck cancer.
OBJECTIVE
The objective of this study was to determine if the use of intravenous contrast results in clinically important errors in intensity-modulated radiation therapy (IMRT) dose calculations for head and neck radiotherapy treatment planning.


METHODS
Nonionic, iodinated intravenous contrast (Iohexol) was administered during the treatment planning computed tomography (CT) scan of 5 patients with head and neck cancer of varying disease sites. The potential effect of intravenous contrast was studied by changing the density of the contrast-enhanced vessels. An inverse IMRT plan was generated from an unmanipulated "normal contrast" planning scan. We then applied the same planning parameters 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 situation, this comparison was repeated by assigning the vessels the maximum density in our planning system ("maximum contrast" density plan).


RESULTS
Dose differences between a planning set of images using intravenous contrast and a set of images without contrast were less than 0.2% for all relevant target volumes and critical structures. A worst-case scenario in which normal contrast was overridden with "maximum contrast" led to small dose differences, generally less than 0.5%.


CONCLUSIONS
Planning head and neck IMRT from CT scans that contain intravenous contrast does not result in clinically important errors in dose delivery.
Liauw
Stanley L
SL
Department of Radiation Oncology, University of Florida College of Medicine, Gainesville, Florida 32610-0385, USA.
Amdur
Robert J
RJ
Mendenhall
William M
WM
Palta
Jatinder
J
Kim
Siyong
S
D003287:Contrast Media / Q000008:administration & dosage*; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D006801:Humans; D007262:Infusions, Intravenous; D011879:Radiotherapy Dosage; D014057:Tomography, X-Ray Computed
D003287:Contrast Media