title: Virtual Monochromatic Images from Dual-Energy Multidetector CT: Variance in CT Numbers from the Same Lesion between Single-Source Projection-based and Dual-Source Image-based Implementations.
abstract: OBJECTIVE
  To determine the variance in virtual monochromatic computed tomography (CT) numbers from the same lesion, comparing the two clinically available dual-energy multidetector CT hardware implementations (single-source projection-based and dual-source image-based), in a phantom-based simulated abdominal environment.
  
  
  METHODS
  This phantom-based study was exempt from institutional review board oversight. Polyethylene terephthalate spheres (15 and 18 mm) with two iodine-to-saline dilutions (0.8 and 1.2 mg of iodine per millilliter) were serially suspended in a cylindrical polypropylene bottle filled with diluted iodinated contrast material. The bottle was placed into a 36-cm-wide torso-shaped water phantom simulating the abdomen of a medium-sized patient. Dual-energy (80/140 kVp) and single-energy (100 and 120 kVp) scans were obtained with single-source and dual-source multidetector CT implementations. Virtual monochromatic images were reconstructed at energy levels of 40-140 keV (in 10-keV increments) in either the projection-space or image-space domain. A multivariate regression analysis approach was used to investigate the effect of energy level, lesion size, lesion iodine content, and implementation type on measured CT numbers.
  
  
  RESULTS
  There were significant differences in the attenuation values measured in the simulated lesions with the single-source projection-based platform and the dual-source image-based implementation (P < .001 for all comparisons). The magnitude of these differences was greatest at lower monochromatic energy levels and at lower iodine concentrations (average difference at 40 keV: 25.7 HU; average difference at 140 keV: 7 HU). The monochromatic energy level and the lesion iodine concentration had a significant effect on the difference in the measured attenuation values between the two implementations, which indicates that the two imaging platforms respond differently to changes in investigated variables (P < .001 for all comparisons).
  
  
  CONCLUSIONS
  There is a statistically significant variance in virtual monochromatic CT numbers from the same lesion examined with single-source projection-based and dual-source image-based implementations. The magnitude of the variance is a function of the selected energy level and the lesion iodine content.
authors.affiliation: From the Department of Radiology (A.M., A.B., D.M., S.S.S., R.C.N.) and Carl E. Ravin Advanced Imaging Laboratories (K.R.C., J.M.W.), Duke University Medical Center, Box 3808, Erwin Rd, Durham, NC 27710.
authors.forename: Achille
authors.initials: A
authors.lastname: Mileto
authors.affiliation: From the Department of Radiology (A.M., A.B., D.M., S.S.S., R.C.N.) and Carl E. Ravin Advanced Imaging Laboratories (K.R.C., J.M.W.), Duke University Medical Center, Box 3808, Erwin Rd, Durham, NC 27710.
authors.forename: Andrew
authors.initials: A
authors.lastname: Barina
authors.affiliation: From the Department of Radiology (A.M., A.B., D.M., S.S.S., R.C.N.) and Carl E. Ravin Advanced Imaging Laboratories (K.R.C., J.M.W.), Duke University Medical Center, Box 3808, Erwin Rd, Durham, NC 27710.
authors.forename: Daniele
authors.initials: D
authors.lastname: Marin
authors.affiliation: From the Department of Radiology (A.M., A.B., D.M., S.S.S., R.C.N.) and Carl E. Ravin Advanced Imaging Laboratories (K.R.C., J.M.W.), Duke University Medical Center, Box 3808, Erwin Rd, Durham, NC 27710.
authors.forename: Sandra S
authors.initials: SS
authors.lastname: Stinnett
authors.affiliation: From the Department of Radiology (A.M., A.B., D.M., S.S.S., R.C.N.) and Carl E. Ravin Advanced Imaging Laboratories (K.R.C., J.M.W.), Duke University Medical Center, Box 3808, Erwin Rd, Durham, NC 27710.
authors.forename: Kingshuk
authors.initials: K
authors.lastname: Roy Choudhury
authors.affiliation: From the Department of Radiology (A.M., A.B., D.M., S.S.S., R.C.N.) and Carl E. Ravin Advanced Imaging Laboratories (K.R.C., J.M.W.), Duke University Medical Center, Box 3808, Erwin Rd, Durham, NC 27710.
authors.forename: Joshua M
authors.initials: JM
authors.lastname: Wilson
authors.affiliation: From the Department of Radiology (A.M., A.B., D.M., S.S.S., R.C.N.) and Carl E. Ravin Advanced Imaging Laboratories (K.R.C., J.M.W.), Duke University Medical Center, Box 3808, Erwin Rd, Durham, NC 27710.
authors.forename: Rendon C
authors.initials: RC
authors.lastname: Nelson
mesh_terms: D003116:Color; D003287:Contrast Media; D006801:Humans; D061330:Multidetector Computed Tomography / Q000379:methods*; D019047:Phantoms, Imaging; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015900:Radiography, Dual-Energy Scanned Projection / Q000379:methods
chemical_list: D003287:Contrast Media