Dual-energy computed tomography image-based volumetric-modulated arc therapy planning for reducing the effect of contrast-enhanced agent on dose distributions.

Abstract To compare the effect of a contrast-enhanced (CE) agent on volumetric-modulated arc therapy plans based on four types of images—virtual monochromatic images (VMIs) captured at 70 and 140 keV (namely VMI70 and VMI140, respectively), water density image (WDI), and virtual non-contrast image (VNC) generated using a dual-energy computed tomography (DECT) system. A tissue characterization phantom and a multi-energy phantom were scanned, and VMI70, VMI140, WDI, and VNC were retrospectively reconstructed. For each image, a lookup table (LUT) was created. For 13 patients with nasopharyngeal cancer, non-CE and CE scans were performed, and volumetric-modulated arc therapy plans were generated on the basis of non-CE VMI70. Subsequently, the doses were re-calculated using the four types of DECT images and their corresponding LUTs. The maximum differences in the physical density estimation were 21.3, 5.2, −3.9, and 0.5% for VMI70, VMI140, WDI, and VNC, respectively. Compared with VMI70, the WDI approach significantly reduced (p