Daniel Tobias Boll MD, Presenter: Research support, Siemens AG Research support, Koninklijke Philips Electronics NV Research support, Bracco Group Consultant, Toshiba Corporation

Tobias Heye MD, Abstract Co-Author: Nothing to Disclose

Sebastian Feuerlein MD, Abstract Co-Author: Nothing to Disclose

To assess accuracy of iodine quantification based on spectral dual-energy CT (DECT) extraction with additional noise reduction using iterative reconstruction in simulated normal and obese patient environments.

Two custom-designed DECT phantoms containing 10 vials with iodine concentrations representing arterial/parenchymal enhancement ranging from water-isodensity to ~150 HU and 40 vials simulating enhancement seen in non-diluted thoracic inlet vasculature, and urinary bladder/renal collecting systems of up to ~2000 HU. DECT acquisition was performed using a dual-source scanner at 140kVp / 90mAs and 80kVp / 495mAs. Backprojection-based soft tissue kernels and corresponding iteratively reconstructed kernels generated dual-energy series used for iodine extraction. Fractional variations between known and spectrally determined iodine concentration were calculated for each concentration step; paired t-tests evaluated variations between backprojected and iteratively reconstructed datasets for normal and obese phantoms. Bland Altman plots with regression analyses assessed concentration differences observed in backprojected and iteratively reconstructed data.

For backprojected data, mean concentration variations of 8.7% ± 8.4 and 12.2% ± 6.3 were detected in normal/obese phantoms, respectively, compared to significantly less variation observed in iteratively reconstructed data with 6.1% ± 6.2 and 11.0% ± 6.5. Dual-energy quantification systematically overestimated concentrations in lower concentration ranges and underestimated concentrations in higher concentration ranges. Regression analyses showed cubic distribution of concentration differences for backprojected, R2=0.697, and linear distribution for iteratively reconstructed data, R2=0.701.

Spectral DECT-based iodine quantification is able to accurately quantify iodine in phantoms simulating normal and large patients; iterative reconstruction improves the accuracy of iodine detection. Systematic deviations of the spectrally determined iodine concentrations could potentially be corrected with weighting curves.

Habitus limits accuracy to detect subtle iodine uptake. By combining dual-energy iodine extraction with iterative reconstruction, accuracy of detecting subtle iodine uptake could be improved.

Boll, D, Heye, T, Feuerlein, S, Iodine Quantification Utilizing Dual Energy MDCT Imaging: Phantom Study Assessing Impact of Iterative Reconstruction Schemes and Patient Habitus on Accuracy.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12032825.html