Introduction to Liver MRI for Surgeons
- Diagnosis of Metastatic Liver Cancer -

Imaging investigations used in liver tumor diagnosis and liver MRI basics (1)

Imaging investigations used to diagnose liver tumors

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).

Table 1. Comparison between different imaging modalities for liver metastasis diagnosis ⁷⁾

Modality	Advantages	Disadvantages
CT	Low cost Availability Higher sensitivity than ultrasonography Whole-body evaluation Anatomical mapping Therapy response assessment	Low sensitivity in cases of steatosis and small metastases (< 1 cm) Low confidence in distinction between malignant and benign lesions Not suitable for renal impaired patients Ionizing radiation
MRI	Most accurate method, especially useful for small lesions (< 1 cm) and in the setting of steatosis High confidence in distinction between malignant and benign lesions Therapy response assessment No ionizing radiation Less allergic reactions	Not suitable for pacemaker carriers Limited use in patients with not suitable for renal impaired patients for increasing risk of nephrogenic systemic fibrosis (NSF)
Ultrasonography	Low cost Availability	Operator dependence Body habitus dependence Low sensitivity Limited ability to distinguish benign lesions from malignant lesions
PET/CT	Accurate extrahepatic detection Therapy response assessment	Highest ionizing radiation dose Low sensitivity for small liver metastases (< 1 cm)

Diagnostic imaging guidelines on EOB-MRI for metastatic liver cancer diagnosis

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.

Table 2 The Japanese Imaging Guideline 2016
CQ80: Which imaging investigations are useful for diagnosing liver metastasis (metastatic liver tumors)?⁸⁾

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.

Introduction to Liver MRI for Surgeons- Diagnosis of Metastatic Liver Cancer -