title: Virtual nonenhanced abdominal dual-energy MDCT: Analysis of image characteristics.
abstract: OBJECTIVE
  To evaluate abdominal and pelvic image characteristics and artifacts on virtual nonenhanced (VNE) images generated from contrast-enhanced dual-energy multidetector computed tomography (MDCT) studies.
  
  
  METHODS
  Hadassah-Hebrew University Medical Institutional Review Board approval was obtained; 22 patients underwent clinically-indicated abdominal and pelvic single-source dual-energy MDCT (Philips Healthcare, Cleveland, OH, USA), pre- and post-IV administration of Omnipaque 300 contrast (100 cc). Various solid and vascular structures were evaluated. VNE images were generated from the portal contrast-enhanced phase using probabilistic separation. Contrast-enhanced-, regular nonenhanced (RNE)-, and VNE images were evaluated with a total of 1494 density measurements. The ratio of iodine contrast deletion was calculated. Visualization of calcifications, urinary tract stones, and image artifacts in VNE images were assessed.
  
  
  RESULTS
  VNE images were successfully generated in all patients. Significant portal-phase iodine contrast deletion was seen in the kidney (61.7%), adrenal gland (55.3%), iliac artery (55.0%), aorta (51.6%), and spleen (34.5%). Contrast deletion was also significant in the right atrium (RA) (51.5%) and portal vein (39.3%), but insignificant in the iliac vein and inferior vena cava (IVC). Average post contrast-to-VNE HU differences were significant (P < 0.05) in the: RA -135.3 (SD 121.8), aorta -114.1 (SD 48.5), iliac artery -104.6 (SD 53.7), kidney -30.3 (SD 34.9), spleen -9.2 (SD 8.8), and portal vein -7.7 (SD 13.2). Average VNE-to-RNE HU differences were significant in all organs but the prostate and subcutaneous fat: aorta 38.0 (SD 9.3), RA 37.8 (SD 16.1), portal vein 21.8 (SD 12.0), IVC 12.2 (SD 11.6), muscle 3.3 (SD 4.9), liver 5.7 (SD 6.4), spleen 22.3 (SD 9.8), kidney 40.5 (SD 6.8), and adrenal 20.7 (SD 13.5). On VNE images, 196/213 calcifications (92%) and 5/6 renal stones (84%) were visualized. Lytic-like artifacts in the vertebral bodies were seen in all studies.
  
  
  CONCLUSIONS
  Iodine deletion in VNE images is most significant in arteries, and less significant in solid organs and veins. Most vascular and intra-abdominal organ calcifications are preserved.
authors.affiliation: Jacob Sosna, Shmuel Mahgerefteh, Department of Radiology, Hadassah-Hebrew University Medical Center, Jerusalem 91120, Israel.
authors.forename: Jacob
authors.initials: J
authors.lastname: Sosna
authors.forename: Shmuel
authors.initials: S
authors.lastname: Mahgerefteh
authors.forename: Liran
authors.initials: L
authors.lastname: Goshen
authors.forename: Galit
authors.initials: G
authors.lastname: Kafri
authors.forename: Galit
authors.initials: G
authors.lastname: Aviram
authors.forename: Arye
authors.initials: A
authors.lastname: Blachar