A wide range of diagnostic imaging modalities, including ultrasonography, CT, and MRI (including contrast-enhanced methods) are used to diagnose liver tumors. Due to advances in these diagnostic imaging techniques allowing the detection of ever smaller liver tumors, today metastatic liver cancer is diagnosed more frequently both before and after treatment of the primary lesion. Each diagnostic imaging modality has advantages and disadvantages in the evaluation of liver metastasis (Table 1).
Modality | Advantages | Disadvantages |
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CT |
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MRI |
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Ultrasonography |
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PET/CT |
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The Japanese Imaging Guideline 20168), edited by the Japan Radiological Society, strongly recommends (recommendation grade A: there is firm scientific evidence and the procedure is strongly recommended) dynamic MRI with Gadoxetate disodium(Gd-EOB-DTPA) as an imaging investigation useful for diagnosing metastatic liver tumors. The guideline gives the explanation shown in Table 2.
Due to evidence that an MRI with liver-specific contrast agents provides superior diagnostic performance compared to ultrasonography and contrast-enhanced CT, MRI with liver-specific contrast agents is strongly recommended. Recently, the use of EOB-MRI has become particularly common. Contrast-enhanced CT is also recommended as it provides the next best diagnostic performance after MRI with liver-specific contrast agents, though there are also benefits to performing EOB-MRI in addition to contrast-enhanced CT. This use of EOB-MRI in addition to contrast-enhanced CT is recommended if EOB-MRI is available. Meanwhile, there is insufficient scientific evidence to determine whether B-mode ultrasonography or contrast-enhanced ultrasonography are superior to contrast-enhanced CT and MRI in terms of diagnostic performance in detecting liver metastasis. Accordingly, B-mode ultrasonography and contrast-enhanced ultrasonography may be considered, but diagnosing liver metastasis based on ultrasonography alone is not recommended, and ultrasonography should be used in combination with another diagnostic imaging technique.