Distinction of Hepatic Vein from Portal Vein by MR Imaging

Abstract

Fast magnetic resonance (MR) imaging techniques are assuming importance in imaging of the abdomen in part due to their ability to produce images during breath-holding, which ensures high spatial resolution and no respiratory motion artifacts. One problem with rapid scanning of the liver, shared with other MR techniques, is confusion between portal and hepatic veins due to similarity in signal intensity. The fast low angle shot (FLASH) technique (flip angle 40 degrees, repetition time 28 ms, and echo time 16 ms) produces high signal in both venous systems. To remedy the problem we incorporated presaturation pulses applied across the portal and mesenteric veins to the FLASH technique; this induced a decrease in signal in the portal venous system and facilitated their differentiation from hepatic veins. Moreover, in one patient an intraportal tumor thrombus not detected on the standard FLASH technique was rendered visible by presaturation. Although the presaturation pulses in the present series were confined to the sagittal plane, the technique should be applicable in any plane as dictated by the anatomy and direction of blood flow. We anticipate wide use of combined presaturation and rapid scanning techniques.