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

Abstract

AIM: To evaluate abdominal and pelvic image char-acteristics and artifacts on virtual nonenhanced (VNE) images generated from contrast-enhanced dual-energy multidetector computed tomography (M�CT) studies. METHODS: Hadassah-Hebrew University Medical In-stitutional Review Board approval was obtained; 22 pa-tients underwent clinically-indicated abdominal and pel-vic single-source dual-energy M�CT (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 signifi-cant 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 dif-ferences were significant (P < 0.05) in the: RA -135.3 (S� 121.8), aorta -114.1 (S� 48.5), iliac artery -104.6 (S� 53.7), kidney -30.3 (S� 34.9), spleen -9.2 (S� 8.8), and portal vein -7.7 (S� 13.2). Average VNE-to-RNE HU differences were significant in all organs but the prostate and subcutaneous fat: aorta 38.0 (S� 9.3), RA 37.8 (S� 16.1), portal vein 21.8 (S� 12.0), IVC 12.2 (S� 11.6), muscle 3.3 (S� 4.9), liver 5.7 (S� 6.4), spleen 22.3 (S� 9.8), kidney 40.5 (S� 6.8), and adrenal 20.7 (S� 13.5). On VNE images, 196/213 calci-fications (92%) and 5/6 renal stones (84%) were visu-alized. 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 or-gans and veins. Most vascular and intra-abdominal or-gan calcifications are preserved.