Iodine quantification accuracy kVp-switching dual-energy CT
Author Block: S. Blazis1, T. Ruytenberg2, N. De Jong2, J. Heemskerk2; 1Goes/NL, 2Leiden/NL
Purpose: The purpose of this study was to determine (1) whether quantification of iodinated contrast medium of a kVp-switching dual-energy CT is accurate, and (2) what the limit of this quantification is.
Methods or Background: Dual-energy CT has been proposed as a tool for semi-quantitative perfusion imaging, using iodine concentration maps. We have investigated the accuracy and limitations of iodine quantification of a fast kVp-switching DECT. Two phantoms were scanned: a Gammex multi-energy phantom, and a 180mm diameter cylindrical water-filled (‘linearity’) phantom containing twelve 16mm diameter tubes with iodinated contrast medium with concentrations ranging from 0 to 30 mgI/ml.
Results or Findings: In line with what has been documented elsewhere, measurements with the ‘linearity’ phantom indicate that lower iodine concentrations (<2mgI/ml) are underestimated with 60-20%. For higher concentrations, the accuracy of iodine quantification is in the order of a few percent. Nevertheless, depicted iodine concentrations increase monotonously with actual concentrations, indicating potential for scoring purposes or thresholding for clinical applications. Gammex phantom images show that distinction between iodine and calcium is challenging for the kVp-switching DECT. This is also apparent from VNC images, where iodine concentrations >3mgI/ml are no longer fully suppressed, and HU values for calcium inserts are reduced.
Conclusion: Dual-energy CT is increasingly proving itself as a useful expansion of CT imaging. Discrimination and quantification of iodinated contrast medium is a promising additional functionality for, for example, detection of intra-cranial hemorrhage or myocardial defect. Fast kVp-switching DECT switching facilitates this iodine quantification, but within limits, and allows creation of virtual non-contrast maps at no extra dose cost. Quantitative iodine imaging with CT remains challenging for clinically relevant concentrations <3mgI/ml, and further investigation of accuracy of iodine quantification and VNC-maps is warranted.
Limitations: This project included phantoms scans only.
Funding for this study: No funding was received for this study.
Has your study been approved by an ethics committee? Not applicable
Ethics committee - additional information: This project only included phantom scans.