Liver, biliary tract and pancreas

Published on 01/04/2015 by admin

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Last modified 01/04/2015

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Chapter 4 Liver, biliary tract and pancreas

Methods of imaging the hepatobiliary system

ULTRASOUND OF THE LIVER

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Ultrasound of the Gallbladder and Biliary System

Additional views

Ultrasound of the Pancreas

Computed Tomography of the Liver and Biliary Tree

Multi-phasic contrast-enhanced CT

The fast imaging times of helical/multi-slice CT enable the liver to be scanned multiple times after a single bolus injection of contrast medium. Most liver tumours receive their blood supply from the hepatic artery, unlike the hepatic parenchyma, which receives 80% of its blood supply from the portal vein. Thus liver tumours (particularly hypervascular tumours) will be strongly enhanced during the arterial phase (beginning 20–25 s after the start of a bolus injection) but of similar density to enhanced normal parenchyma during the portal venous phase. Some tumours are most conspicuous during early-phase arterial scanning (25 s after the start of a bolus injection), others later, during the late arterial phase 35 s after the start of a bolus injection. Thus a patient who is likely to have hypervascular primary or secondary liver tumours should have an arterial phase scan as well as a portal venous phase CT scan (see above). Early and late arterial phase with portal venous phase is appropriate for patients with suspected hepatocellular cancer (triple phase). In general, late arterial and portal venous scans are appropriate to investigate suspected hypervascular metastases, although an alternative strategy would be to perform an unenhanced scan followed by a portal venous phase scan.

Haemangiomas often show a characteristic peripheral nodular enhancement and progressive centripetal ‘fill-in’. After the initial dual- or triple-phase protocol, delayed images at 5 and 10 min are obtained through the lesion.

Computed Tomography of the Pancreas