Liver cancer imaging: role of CT, MRI, US and PET

Abstract

Liver imaging in patients with a history of known or suspected malignancy is important because the liver is a common site of metastatic spread, especially tumours from the colon, lung, pancreas and stomach, and in patients with chronic liver disease who are at risk for developing hepatocellular carcinoma. Since benign liver lesions are common, liverimaging strategies should incorporate liver lesion detection and characterisation. Survey examination in patients with a known extra-hepatic malignancy to exclude the presence of hepatic and extra-hepatic involvement is normally undertaken with a contrast-enhanced computed tomography examination. When patients with hepatic metastases are being considered for metastasesectomy, they undergo a staging examination with contrast-enhanced magnetic resonance imaging (MRI) using tissue-specific contrast agents. Patients with chronic liver disease who are at risk for hepatocellular carcinoma undergo periodic liver screening for focal liver detection, usually with ultrasonography (US) with MRI being used when US is equivocal. Finally, contrast-enhanced MRI with extra-cellular gadolinium chelates is preferred for characterisation of indeterminate hepatic masses with liver biopsy used when tissue diagnosis is needed.

Figure 1

Arterial phase contrast-enhanced computed tomography in a patient with renal cell carcinoma demonstrating hypervascular metastases to the pancreas.

Figure 2

PET (a) demonstrates a focus of uptake in the right liver lobe in a patient with colon carcinoma who had undergone a metastasectomy, as seen on the CT (b). No tumour recurrence was present on follow-up scans.

Figure 3

T1-weighted MRI of the liver demonstrates higher metastases–liver contrast on hepatocyte-specific contrast agent (mangafodipir) enhanced images (a) compared to the pre-contrast images (b). Note that an additional lesion is seen on post-contrast image in segment IV.

Figure 4

MRI of the liver in a patient with chronic liver disease. T1-weighted pre-contrast injection (a), T2-weighted (b) and arterial phase extracellular Gd-chelate-enhanced MRI (c) demonstrating a T1 and T2 hyperintense mass which is enhanced in the arterial phase, indicative of an HCC.