The Effect of Contrast Agents on Dose Calculations of Volumetric Modulated Arc Radiotherapy Plans for Critical Structures

Radiotherapy dose calculation requires accurate Computed Tomography (CT) imaging while tissue delineation may necessitate the use of contrast agents (CA). Acquiring these two sets is a common practice in radiotherapy. This study aims to evaluate effect CA on calculations. Two hundred and twenty-six volumetric modulated arc therapy (VMAT) patients that had planning CT with (CCT) non-contrast (NCCT) different cancer sites (e.g., brain, head, neck (H&N), chest, abdomen, pelvis) were evaluated. Treatment plans recalculated using CCT, then compared NCCT. The variation Hounsfield units (HU) distributions for critical structures target volumes analyzed mean HU, maximum relative values, D2%, D98%, 3D gamma analysis. HU variations statistically significant most structures. However, this was not clinically as difference values within 30 soft 50 lungs. Variation volumes’ D2% D98% insignificant all except brain nasopharynx. Dose differences 2% majority volumes. analysis results revealed satisfied 2 mm criteria. CCT be acquired VMAT radiotherapy purposes instead NCCT, since there no calculations based either image set.