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

MRI is well suited for metastatic disease detection because this modality provides high lesion-to-liver contrast and does not use ionizing radiation. Specifically, metastases have long T2 values because they contain abundant water, rendering them particularly bright on T2-weighted sequences. Metastases may also be detected on T1-weighted scans, which may be acquired with or without the injection of intravenous gadolinium contrast agents. When gadolinium contrast agents are injected, the lesion-to-liver conspicuity is increased. Indeed, most studies show that MRI with or without intravenous contrast is slightly more sensitive than CT for the detection of metastatic disease,[46,47,48,49] With current MRI scanners, it is now possible to acquire excellent-quality images of the entire liver within a single breath hold.[59,60] Such rapid scanning allows dynamic imaging of the liver during a bolus injection of contrast, analogous to dual-phase imaging with CT (Fig. 2).

Figure 2

Hypervascular tumor as demonstrated on contrast-enhanced arterial phase CT and MRI. A. Contrast-enhanced CT during the arterial predominant phase of enhancement shows a large vascular mass in the left lobe of the liver. Note the prominent central arteries. B. Gadolinium-enhanced dynamic gradient echo MRI shows enhancement characteristics similar to the CT in A. This lesion proved to be a metastatic leiomyosarcoma.

Figure 2

Hypervascular tumor as demonstrated on contrast-enhanced arterial phase CT and MRI. A. Contrast-enhanced CT during the arterial predominant phase of enhancement shows a large vascular mass in the left lobe of the liver. Note the prominent central arteries. B. Gadolinium-enhanced dynamic gradient echo MRI shows enhancement characteristics similar to the CT in A. This lesion proved to be a metastatic leiomyosarcoma.

In addition to gadolinium, several liver-specific MRI contrast agents have been developed.[60] Supraparamagnetic iron oxide particles (Feridex, Berlex Laboratories, Wayne, NJ) are phagocytized by the reticuloendothelial system of the liver, resulting in decreased signal on T2-weighted images. Because metastases are free of the reticuloendothelial system, they maintain bright signal intensity on T2-weighted scans and become conspicuous compared with the background liver. Another agent is manganese dipyridoxal diphosphate (Mn-DPDP) (Teslascan, Nycomed Laboratories, Princeton, NJ), which is taken up by hepatocytes and excreted in bile.[60] On T1-weighted scans manganese increases signal intensity of the normal liver. Metastases appear relatively dark compared with the enhanced liver. Interestingly this agent allows discrimination of hepatocyte-containing lesions such as hepatic adenomas from metastatic deposits because hepatocyte-containing lesions take up the agent.

Disadvantages of MRI include high capital equipment costs, high maintenance costs, complex imaging protocols, and susceptibility to motion artifacts from cardiac pulsation, respiration, and bowel peristalsis.[1] Exam times are considerably longer with MRI than with CT, which further drives up the cost of MRI. Finally, because of the superiority of MRI in the central nervous system and musculoskeletal system, most clinical MRI centers have a substantial backlog of cases. Despite these disadvantages, MRI has replaced CT for the evaluation of metastatic disease in some centers.

Our approach to most patients with metastatic disease is to perform a precontrast CT of the liver followed by a contrast-enhanced spiral CT scan of the liver and the remainder of the abdomen and pelvis. In patients with suspected hypervascular metastatic disease, a dual-phase acquisition is performed. These CT examinations are reliable, reproducible, and readily available and provide an excellent screen of the liver as well as the extrahepatic tissues. If a patient cannot receive intravenous contrast due to renal insufficiency or history of allergic reaction, we perform MRI instead.

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