Evaluation of the Liver for Metastatic Disease

Erik K. Paulson, MD1, 1Department of Radiology, Duke University Medical Center, Durham, North Carolina.

Semin Liver Dis. 2001;21(2) 

In This Article

Magnetic Resonance Imaging

By MRI, the appearance of metastases varies based on the imaging sequence performed.[1,59,60] Typically, on T1-weighted scans, metastases are of low signal intensity relative to the background liver. On T2-weighted scans, metastases are of high signal intensity relative to the background liver (Fig. 15). However, the signal intensity of metastases on T2-weighted images is less than that of hemangiomas or cysts, which typically have an intensity similar to fluid in the thecal space or gallbladder. As with CT and US, metastases are usually multiple, round, and heterogeneous. Enhancement characteristics of metastases with gadolinium parallel that of CT. As with US, metastases by MRI may be rimmed by a halo of high signal intensity or appear as a target lesion.

Figure 15

Colon carcinoma metastasis on MRI. T2-weighted MRI of the liver shows two hyperintense masses. The high signal and heterogeneous nature of these tumors are typical for metastatic deposits.

MRI is particularly helpful in the patient with suspected diffuse metastatic disease in whom CT or US might underestimate tumor burden (Fig. 16).

Figure 16

Multiple metastases from breast cancer seen to better advantage using MRI than CT. A. Contrast-enhanced CT is normal. Metastases are not identified. B. T2-weighted MRI shows multiple liver metastases. In this case, MRI was considerably more sensitive for lesion detection than CT.

Figure 16

Multiple metastases from breast cancer seen to better advantage using MRI than CT. A. Contrast-enhanced CT is normal. Metastases are not identified. B. T2-weighted MRI shows multiple liver metastases. In this case, MRI was considerably more sensitive for lesion detection than CT.

An additional scenario where MRI is useful is in the patient with fatty infiltration in whom by CT or US it may be difficult to differentiate metastatic deposits from regions of liver that are spared fatty infiltration (Fig. 17). In this scenario, chemical shift imaging is useful.

Figure 17

Metastasis in the presence of fatty infiltration. A. Precontrast CT scan shows the liver parenchyma to be of diffuse low attenuation due to diffuse fatty infiltration. In the dome, there is a rounded focus of high attenuation (arrow), which could represent either a metastatic deposit or an area of sparing of fatty infiltration. B. Gadolinium-enhanced gradient echo MRI of the liver shows the lesion to be uniformly hyperenhancing. This lesion proved to be a hypervascular metastatic deposit in a patient with neuroendocrine tumor. In this case, MRI clarified an indeterminate CT scan finding.

Figure 17

Metastasis in the presence of fatty infiltration. A. Precontrast CT scan shows the liver parenchyma to be of diffuse low attenuation due to diffuse fatty infiltration. In the dome, there is a rounded focus of high attenuation (arrow), which could represent either a metastatic deposit or an area of sparing of fatty infiltration. B. Gadolinium-enhanced gradient echo MRI of the liver shows the lesion to be uniformly hyperenhancing. This lesion proved to be a hypervascular metastatic deposit in a patient with neuroendocrine tumor. In this case, MRI clarified an indeterminate CT scan finding.

On T1-weighted images, some metastases will appear as high signal intensity lesions. This may occur in melanoma deposits due to the paramagnetic effect of melanin, lesions that are hemorrhagic, and necrotic lesions that contain fluid with a high protein concentration.

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