Room: Karl Dean Ballroom B1
Purpose: To assess and implement dual-energy CT (DECT) techniques in radiotherapy simulation through phantom studies with readily available clinical phantoms.
Methods: Phantom studies were conducted to investigate the expected benefits of DECT for a single-source, dual-energy-capable scanner (Siemens Definition AS) in both artifact reduction and improved low-contrast target delineation. A CIRS multi-density phantom with titanium insert was used to demonstrate artifact reduction as well as the effect on Hounsfield-unit-density tables for use in treatment planning, and a Catphan model 604 was utilized to quantify potential improvement in low-contrast resolution for several DECT protocols compared to conventional scans. Multiple reconstruction kernels and metal artifact reduction (MAR) reconstruction techniques were used for scans of both phantoms.
Results: Dual-energy scanning was shown to improve artifact reduction beyond the capabilities of Siemens MAR techniques, with further improvement achieved when both were used together. However, the choice of MAR technique requires careful consideration due to the different results seen across the available options. DECT scans reconstructed at 120, 140 and 190 keV showed substantial HU-density table variations, especially near the higher density regions. MAR techniques caused some variation as well, especially for the â€˜neuro coilâ€™ and â€˜dental fillingâ€™ settings. Dual-energy scans of the Catphan reconstructed at 40, 50 and 70 keV showed marked improvement in low contrast resolution; conventional scans resulted in 7-8 mm resolution at optimal window/level whereas DECT improved the results to 4-5 mm for the phantomâ€™s 1% contrast targets.
Conclusion: The effects of DECT on artifact reduction, HU-density tables, and low-contrast target delineation were demonstrated for a single-source, dual-energy CT simulator. This investigation provides evidence of the utility of DECT for radiotherapy simulation, and provides radiation oncology physicists with a straightforward strategy for implementing these techniques clinically.