Room: Room 202
Purpose: To assess the accuracy of iron quantification using a whole-body PCD-CT and an iron-specific material decomposition technique.
Methods: We synthesized iron mixtures to mimic liver iron deposition and scanned them using a whole-body PCD-CT system (Somatom CounT, Siemens). Three iron-water solutions at concentrations of 1.4, 2.8 and 5.6 mg/mL, and three iron-gelatin mixtures at iron concentrations of 1.3, 2.7 and 5.1 mg/mL were prepared. The CT number of pure gelatin at 120kV is about 6 (Â±5) HU. The iron-water solutions and the iron-gelatin mixtures were placed in cylindrical tubes (2 cm diameter), which were inserted into a multi-energy CT phantom (20cm module, Gammex). PCD-CT scanning was performed using macro mode (32 x 0.5 mm collimation) at 120 kV, 178 mAs, 1s rotation time and [25,63] keV energy thresholds. Multi-energy PCD-CT images were reconstructed using weighted-filtered back projection with a smooth quantitative kernel (D30) at 3 mm slice thickness (FOV = 27.5 cm). An image-domain material decomposition algorithm was used to quantitatively decompose the PCD-CT images into iron, gelatin and water basis materials. Regression analysis was performed to determine the quantitative accuracy of the estimated iron concentrations, and root-mean-squared error (RMSE) values were reported for estimated concentrations relative to the ground truth.
Results: The estimated iron concentrations for iron-water solutions showed good correlation with the ground truth, with a slope of 1.03, RÂ² = 0.99 and an RMSE = 0.2 mg/mL. The estimated iron concentrations for the iron-gelatin mixtures also demonstrated good correlation with the true concentrations (slope = 1.02) with RÂ² = 0.98 and an RMSE = 0.4 mg/mL.
Conclusion: We demonstrated accurate iron quantification in a phantom using PCD-CT in combination with a basis material decomposition technique. Iron concentrations as low as 1.3 mg/mL used in our study were successfully distinguished from the background material (gelatin).
Funding Support, Disclosures, and Conflict of Interest: This research was supported in part by NIH Grant, R01-EB016966 and C06-RR018898. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. The research photon-counting CT system described herein is not commercially available.