Room: Osceola Ballroom C
Purpose: Hemorrhagic blood can appear hyperdense on CT images, complicating the differentiation of blood and contrast extravasation following a stroke. This study evaluates the limits of material differentiation in virtual non-contrast (VNC) images and iodine maps of a dual energy CT (DECT) system, with focus on differing types of blood and mixtures of blood and iodine.
Methods: Limitations on detectability of iodine (2 mg/mL, 4 mg/mL), and blood (40 HU and 70 HU) will be assessed using a tissue equivalent multi-energy CT (MECT) phantom (Gammex Model 1472). Reproducibility was tested by scanning at 80 and 135 kV three times daily for 6 non-consecutive days thus far. Using the vendor generated head protocol, iodine maps and VNCs were reconstructed in the raw data domain. Circular regions of interest at the central axial slice of the phantom were generated using the Gammex Rod Evaluate Software (v1.7). The mean pixel intensity [HU] and the standard deviation (SD) between the daily means of the ROI measurements was generated. These measurements quantified statistical limitations in iodine maps and VNCs while simulating clinical findings such as residual iodine contrast and hemorrhagic lesions.
Results: The coefficients of variation were calculated for the differing materials for the iodine map (0-24%) and VNC image (2-18%).In the VNC images, the mixture of iodine (4 mg/mL) and 40-HU blood was not significantly different from a 70-HU blood material (76 Â± 4 HU and 68 Â± 6 HU, respectively). The iodine map differentiated the blood material from the heterogeneous blood and iodine material (6 Â± 4 HU and 109 Â± 8 HU, respectively).
Conclusion: A limitation in the differentiation between blood and mixtures of iodine and blood was found in the VNC, but was resolved in the iodine map. The use of both image sets is recommended for proper material differentiation.
Funding Support, Disclosures, and Conflict of Interest: Has any company or organization whose products/services are the subject matter of your presentation provided you with any financial support for your research? Yes, we have a Canon contract pending. We will receive funding to characterize Canon's DECT systems. Canon has also lent the Gammex MECT phantom for this purpose.