There are two main categories of gadolinium contrast agents used Gefitinib molecular weight for hepatic imaging: extracellular agents and hepatocyte-specific agents (Table 1).8, 9 The most widely used are the extracellular gadolinium agents,
which are used for routine imaging throughout the body. These agents circulate in the vascular system, are distributed into the extracellular space, and are excreted by the kidneys. The enhancement characteristics of hepatic lesions are similar to those seen on CT. However, in some cases, the enhancement may be more conspicuous on MRI because of the increased soft tissue contrast. There are two liver-specific contrast agents: gadobenate dimeglumine (MultiHance, Bracco) and gadoxetate disodium (Eovist from Bayer HealthCare, which is also known as Primovist in Europe).8, 9 These agents are taken up by normally functioning hepatocytes and are excreted into the biliary system. Therefore, these agents may be able to differentiate tumors that have
normally functioning hepatocytes and biliary excretion from those that do not. Both gadobenate dimeglumine and gadoxetate disodium NVP-AUY922 in vitro are injected dynamically and are circulated and distributed in the extracellular space similarly to extracellular gadolinium agents. Therefore, similarly to the extracellular agents, imaging can be performed during the arterial and portal venous phases. However, the ability to allow delayed hepatocyte-specific imaging provides additional information. Gadobenate dimeglumine is taken up by hepatocytes and
is excreted into the biliary system by anion transport. Delayed imaging, also known as the hepatocyte phase, is usually performed at 60 to 90 minutes. Delayed imaging allows the differentiation of lesions that have normally functioning hepatocytes, which show some degree Bacterial neuraminidase of contrast uptake, from lesions without normally functioning hepatocytes, which have lower intensity in comparison with normal parenchyma. Gadoxetate disodium is transported from the extracellular space into the hepatocytes by adenosine triphosphate–dependent organic anion transporting polypeptide 1. It is subsequently excreted into the biliary canaliculi by the canalicular multispecific organic anion transporter.8 Fifty percent of this agent is excreted by the biliary system, whereas only 5% of gadobenate dimeglumine is. Therefore, there is more intense enhancement of the liver with gadoxetate disodium. In addition, the hepatocyte phase scans can be performed at only 20 minutes, and this improves efficiency. A limitation of gadoxetate disodium is that the recommended dose of 0.025 mmol/kg (0.1 mL/kg) is only one-quarter of the dose of gadobenate dimeglumine and various other extracellular agents (0.1 mmol/kg or 0.2 mL/kg). The volume of contrast administered to a 70-kg patient is one-half or 7 mL.