Early contrast enhancement of the liver: exact description of subphases using MRI Jose A. Goncalves Neto a , Ersan Altun a , Georgeta Vaidean b , Mohamed Elazzazi a , Jeffrey Troy a , Sudha Ramachandran a , Richard C. Semelka a, ⁎ a Department of Radiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA b Department of Preventive Medicine, University of Tennessee Medical Center, Memphis, TN 38163, USA Received 3 August 2008; revised 14 October 2008; accepted 10 November 2008 Abstract Purpose: The purpose of this study was to describe the subphases of early post-contrast enhancement of the liver, using vessel enhancement patterns, and correlate these findings with enhancement patterns of abdominal organs. Materials and Methods: A total of 114 patients who underwent gadolinium-enhanced abdominal magnetic resonance imaging examinations constituted the final study group, of which 56 were women (age range, 3–94 years; mean, 50 years) and 58 were men (age range, 6–85 years; mean, 54 years). Early post-contrast sequences in all patients were evaluated retrospectively by two reviewers for the determination of the presence of contrast enhancement in predetermined major vessels of the abdomen and qualitative and quantitative extent of enhancement of the renal cortex, spleen, pancreas and liver. Based on the overall findings, subphases of early contrast enhancement of the liver were described and quantitative extent of enhancement of organs was correlated with subphases of early contrast enhancement of the liver. Mann– Whitney U test and one-way unbalanced analysis of variance tests were used for the comparisons. Results: Early hepatic arterial phase was observed in 14/114 patients, mid-hepatic arterial phase in 23/114 patients, late hepatic arterial phase in 33/114 patients, splenic vein only hepatic arterial dominant phase in 20/114 patients and hepatic arterial dominant phase in 24/114 patients. There was an overall association between the subphases of enhancement and the quantitative extent of enhancement for all studied organs (Pb .0001). Conclusion: The evaluation of vessel and organ enhancement patterns has allowed the characterization of five different subphases in early post-contrast enhancement of the liver. The quantitative extent of enhancement of abdominal organs also demonstrated significant correlation with these five subphases. © 2009 Elsevier Inc. All rights reserved. Keywords: MRI; Liver; Early enhancement; Phase 1. Introduction Early post-contrast imaging of the liver obtained on either computed tomography or magnetic resonance (MR) images is most often referred to as hepatic arterial phase [1–5]. “Hepatic arterial imaging” is generally used as a catchall term for early dynamic imaging [6–8]. Although this term may be useful so far as it identifies that data have been acquired quickly after the contrast administration, it may result in diagnostic errors in image interpretation because optimal enhancement is likely observed in a relatively short time window in the early post-contrast imaging or “hepatic arterial imaging” phase [2,6–9]. Prior reports in the MR literature have stressed the significance of the hepatic arterial dominant phase (HADP) as the optimal subphase of enhancement in the early post- contrast imaging [2,10,11]. It has been described as the phase in which contrast is present in the hepatic arteries and portal veins prior to contrast appearing in the hepatic veins [10,11]. It has also been stressed that the enhancements of other parenchymal organs demonstrate variations in the early post- contrast imaging [12–14]. Especially, the pancreas exhibits a Available online at www.sciencedirect.com Magnetic Resonance Imaging 27 (2009) 792 – 800 ⁎ Corresponding author. Tel.: +1 919 966 4400; fax: +1 919 966 9143. E-mail address: richsem@med.unc.edu (R.C. Semelka). 0730-725X/$ – see front matter © 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.mri.2008.11.003