From our experience, the combination of DWI with Gd-EOB-DTPA MRI yields the highest sensitivity for small liver metastases. Figure

3 Small colorectal liver metastases on MRI using delayed hepatobiliary phase imaging and diffusion weighted imaging. A 52-year-old woman who underwent percutaneous radiofrequency ablation in the right hepatic lobe (large arrow), developed a 3-mm recurrence … MRI may not be the examination of choice for every patient. Patients with contraindications to MRI (e.g. implantable pacemakers), or unable to tolerate MRI (e.g. due to claustrophobia) Inhibitors,research,lifescience,medical would preferably undergo preoperative imaging with CT. selleck compound Motion related imaging artifacts that can severely dampen the diagnostic quality of MRI will occur in patients who are unable to breath hold for longer than 20 seconds. Positron Inhibitors,research,lifescience,medical emission tomography (PET) Positron Emission Tomography (PET) is performed to detect the uptake of a glucose analog, 18F-fluorodeoxyglucose (FDG) in hypermetabolic tumors. FDG-PET is now routinely performed in combination with CT, either with or without intravenous contrast, Inhibitors,research,lifescience,medical and excels at the detection of colorectal liver and extrahepatic metastases (23). On PET, hypermetabolic liver tumors demonstrate high uptake (Figure 2 B). However, physiologic background liver

uptake of FDG in combination with the inherent low resolution of PET can limit the sensitivity for detection of small liver metastases (24). The use of intravenous contrast during the CT portion of the examination is preferred, improving the detection of liver metastases (25). Comparison between modalities A recent meta-analysis was performed on prospective studies Inhibitors,research,lifescience,medical using CT, MRI, FDG PET (Table 1) between 1990 and January 2010 on metastatic colorectal patients who had not Inhibitors,research,lifescience,medical undergone any prior therapy (26). This analysis found large heterogeneity in the methodologies between studies, which is expected when reviewing studies spanning 20 years. The authors concluded that CT generally had the lowest sensitivity, especially

for lesions smaller than 10 mm. They also found that MRI had significantly increased sensitivity over the years, especially comparing studies before and after 2004 (from 70% to 85% sensitivity), and recommended MRI as the first line modality, with FDG-PET playing a role for extrahepatic disease detection. Table 1 Sensitivity and specificity of CT, nearly MRI, FDG-PET. A recent study comparing multi detector CT, contrast-enhanced US and MRI from Japan found the highest sensitivity for MRI (95%) compared to CT and US (63% and 73% respectively) (27). In this study, MRI was performed with both DWI and delayed hepatobiliary phase imaging using Gd-EOB-DTPA. A limitation in studies comparing imaging modalities for detection of liver metastases is the lack of an absolute reference standard.