Room: Room 205
Purpose: To investigate the ability of a single-source dual-energy CT (ssDECT) scanner to perform calcium removal to aid in the delineation of bone lesions for radiation therapy treatment planning.
Methods: The TwinBeam (TB) and Dual Spiral (DS) ssDECT techniques on the Siemens Somatom Definition Edge CT scanner were evaluated for their ability to remove calcium from images to better delineate bone lesions. A phantom containing inserts with varying concentrations of calcium (50-600 mg/ml) was imaged with the TB and DS techniques to determine dual-energy (DE) ratios. These DE ratios were used in the Syngo.via software to generate virtual non-calcium (VNCa) and bone marrow (BM) images. The DECT calcium-removal techniques were used clinically to aid in the delineation of bone lesions. Contrast-to-noise ratios (CNR) between tumor and surrounding marrow was compared between mixed (120kVp-equivalent), VNCa, and BM images.
Results: The DE ratios for calcium removal for the TB and DS techniques were determined to be 1.11 and 1.51, respectively. Using these DE ratios, the concentrations of calcium removed by the TB and DS techniques were in agreement; however, the noise in the VNCa TB images was as much as eight times greater than comparable DS images. Relative to mixed images, preliminary results showed that the CNR between lesions and surrounding tissue increased by as much as a factor of three and five with VNCa and BM techniques, respectively.
Conclusion: The ability of a ssDECT system to perform calcium removal for radiation therapy treatment panning, using commercially available equipment and software, was assessed. Calcium removal was performed with experimentally determined DE ratios for VNCa and BM images acquired with the TB and DS techniques. The DS VNCa and BM techniques showed increased CNR between tumor and surrounding tissue compared to a mixed image for a preliminary set of patients with bone lesions.