In another series, MRI with and without IV contrast is able to establish a definitive diagnosis in 95% of liver lesions, which is significantly higher than contrast- enhanced CT [11]. Furthermore, only 1.5% of patients with MRIs require recommendation for further imaging as opposed to 10% with CT [11]. Performance characteristics of MRI depend on the sequences and type of contrast, as well as the lesion itself. A combination of diffusion-weighted imaging (DWI) and HBP allows correct classification of lesions as benign or malignant in 91% of cases and exact characterization in 85% of cases [15]. Gadoxetate-enhanced MRI has an accuracy of 95% to 99% for diagnosis of hemangioma, accuracy of 88% to 99% for the diagnosis of FNH, and accuracy of 97% for diagnosis of HCC in patients with incidentally discovered liver lesions [10,12]. For differentiation between adenoma and FNH, low signal on HBP is 100% specific, 92% sensitive, Liver Lesion-Initial Characterization and 97% accurate for hepatocellular adenoma [16]. However, it should be noted that inflammatory adenoma can mimic FNH on MRI [17]. For the diagnosis of a hemangioma, MRI with extracellular gadolinium contrast has sensitivity of 93%, specificity of 99%, accuracy of 98%, PPV of 96%, and NPV of 99% [18]. Although apparent diffusion coefficient (ADC) values of solid benign lesions are higher than those of the solid malignant lesions, there is a considerable overlap of the ADC values between the two groups [19]. Therefore, in patients without a history of malignancy, the value of DWI for differentiating solid liver masses may be limited. There is no relevant literature that has assessed the performance of MRI without IV contrast specifically for this clinical scenario. Therefore, the committee recommendations on the use of MRI without IV contrast are based primarily on expert opinion.
Liver Lesion Initial Characterization. In another series, MRI with and without IV contrast is able to establish a definitive diagnosis in 95% of liver lesions, which is significantly higher than contrast- enhanced CT [11]. Furthermore, only 1.5% of patients with MRIs require recommendation for further imaging as opposed to 10% with CT [11]. Performance characteristics of MRI depend on the sequences and type of contrast, as well as the lesion itself. A combination of diffusion-weighted imaging (DWI) and HBP allows correct classification of lesions as benign or malignant in 91% of cases and exact characterization in 85% of cases [15]. Gadoxetate-enhanced MRI has an accuracy of 95% to 99% for diagnosis of hemangioma, accuracy of 88% to 99% for the diagnosis of FNH, and accuracy of 97% for diagnosis of HCC in patients with incidentally discovered liver lesions [10,12]. For differentiation between adenoma and FNH, low signal on HBP is 100% specific, 92% sensitive, Liver Lesion-Initial Characterization and 97% accurate for hepatocellular adenoma [16]. However, it should be noted that inflammatory adenoma can mimic FNH on MRI [17]. For the diagnosis of a hemangioma, MRI with extracellular gadolinium contrast has sensitivity of 93%, specificity of 99%, accuracy of 98%, PPV of 96%, and NPV of 99% [18]. Although apparent diffusion coefficient (ADC) values of solid benign lesions are higher than those of the solid malignant lesions, there is a considerable overlap of the ADC values between the two groups [19]. Therefore, in patients without a history of malignancy, the value of DWI for differentiating solid liver masses may be limited. There is no relevant literature that has assessed the performance of MRI without IV contrast specifically for this clinical scenario. Therefore, the committee recommendations on the use of MRI without IV contrast are based primarily on expert opinion.