Virtual nonenhanced abdominal dual-energy MDCT: Analysis of image characteristics

AIM: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-toRNE 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.CONCLUSION: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.