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Phantom Validation of Spectral Detector Computed Tomography–Derived Virtual Monoenergetic, Virtual Noncontrast, and Iodine Quantification Images

Ananthakrishnan, Lakshmi, MD; Duan, Xinhui, PhD; Rajiah, Prabhakar, MD; Soesbe, Todd C., PhD; Lewis, Matthew A., PhD; Xi, Yin, PhD; Fielding, Julia R., MD; Lenkinski, Robert E., PhD; Leyendecker, John R., MD; Abbara, Suhny, MD

Journal of Computer Assisted Tomography: November/December 2018 - Volume 42 - Issue 6 - p 959–964
doi: 10.1097/RCT.0000000000000763
Technical Developments in Dual Energy CT

Purpose Spectral detector computed tomography (SDCT) is a new CT technology that uses a dual-layer detector to perform energy separation. We aim to assess 3 clinical concepts using a phantom model: noise profile across the virtual monoenergetic (VME) spectrum, accuracy of iodine quantification, and virtual noncontrast (VNC) reconstructions' ability to remove iodine contribution to attenuation.

Methods Six vials containing varying concentrations of iodinated contrast (0–6 mg/mL) diluted in water were placed in a water bath and scanned on an SDCT scanner. Virtual monoenergetic (40–200 keV at 10-keV increments), iodine–no-water, and VNC reconstructions were created. Attenuation (in Hounsfield units [HU]), VME noise at each energy level, CT-derived iodine concentration, and VNC attenuation were recorded.

Results Virtual monoenergetic noise was improved at all energies compared with conventional images (conventional, 9.8–11.2; VME, 7.5–9.5). Noise profile showed a slightly higher image noise at 40 keV, but was otherwise relatively flat across the energy spectrum. On iodine–no-water reconstructions, measured varied from actual iodine concentration by ±0.1 mg/mL (SD, 0.16–0.36). Virtual noncontrast attenuation was within 5 HU of water attenuation at all iodine concentrations.

Conclusion Reconstructions of SDCT show lower VME image noise, accurate iodine quantification, and VNC attenuation values within 5 HU of expected in a phantom model.

From the UT Southwestern Medical Center, Dallas, TX.

Received for publication December 9, 2017; accepted April 2, 2018.

Correspondence to: Lakshmi Ananthakrishnan, MD, Department of Radiology, UT Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390–8827 (e-mail:

The authors declare no conflict of interest.

An institutional research agreement exists between UT Southwestern Medical Center and Philips Healthcare. Individual authors have no relevant conflicts of interest.

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