Spatial Relationship Between the Hepatic Artery and Portal Vein Based on the Fusion Image of CT Angiography and CT Arterial Portography: The Left Hemiliver

OBJECTIVE. The objective of our study was to clarify the hepatic artery anatomy of the left hemiliver using the fusion image of CT angiography (CTA) and CT arterial portography. MATERIALS AND METHODS. CTA and CT arterial portography were performed on a 64-MDCT scanner in 144 patients. All images were transferred to a workstation for 3D analysis using the multiimage fusion mode. We classified the left hepatic artery (LHA) and middle hepatic artery (MHA) as type L when only the LHA was present, type MB when a medial branch from the LHA was present, type LM when both the LHA and MHA were present, and type M when only the MHA was present. The hepatic artery was classified into infraportal and supraportal groups on the basis of its relationship with the laterosuperior branch of the left portal vein. We also classified the branching pattern of the arteries to each segment. Pattern 1 was defined as when the LHA divided into the laterosuperior segment artery (A2), which then divided into the lateroinferior segment artery (A3) and medial segment artery (A4). Pattern 2 was defined as when the LHA divided into A3, which then divided into A2 and A4. Pattern 3 was defined as when the LHA divided into A4, which then divided into A2 and A3. Pattern 4 was defined as when the LHA divided into A2, A3, and A4 simultaneously. RESULTS. The prevalence of each type was as follows: type L (n = 37, 25.7%), type MB (n = 44, 30.6%), type LM (n = 53, 36.8%), and type M (n = 6, 4.2%). The number of cases classified as infraportal was 54 (37.5%) and supraportal, 73 (50.7%). The cases classified by branching pattern were as follows: pattern 1, 26 cases (18.0%); pattern 2, eight (5.6%); pattern 3, 93 (64.5%); and pattern 4, 13 (9.0 %). CONCLUSION. Three-dimensional fusion images based on CTA and CT arterial portography can show the various anatomic patterns of the left hemiliver hepatic artery in relation to the left portal vein.