Diffusion tensor imaging of cysts, hemangiomas, and metastases of the liver.

BACKGROUND: Although diffusion-weighted magnetic resonance imaging imaging (DW-MRI) is commonly used to characterize hepatic lesions, the literature is sparse about the use of MR diffusion tensor imaging (DTI) in this regard. By using DTI, one is able to obtain not only apparent diffusion coefficients (ADCs) but also fractional anisotropy (Fa) values.

PURPOSE: To evaluate DTI using ADC and Fa values in the imaging of hepatic cysts, hemangiomas, and metastases.

MATERIAL AND METHODS: Sixty-six patients with 77 lesions were examined with DTI. There were 32 metastases, 13 cysts, and 32 hemangiomas. Two radiologists performed ADC and Fa measurements. Inter-observer agreement was evaluated using Bland-Altman plots. ADCs and Fa values were correlated using Pearson correlation. The differences were compared using ANOVA and Tukey tests. A ROC analysis was applied; sensitivities and specificities were calculated.

RESULTS: The inter-observer agreement was very good. The correlation between ADC and Fa was negative, weak, and significant (r = -0.36). The mean ADC value of cysts (3.30 ± 0.8 × 10(-3) mm(2)/s) was significantly higher than that of hemangiomas (2.23 ± 0.5 × 10(-3) mm(2)/s) and metastases (1.62 ± 0.4 × 10(-3) mm(2)/s). The mean Fa value of cysts (0.2 ± 0.05) was significantly lower than hemangiomas (0.37 ± 0.1) and metastases (0.46 ± 0.1). The Az values for discriminating metastases from benign hepatic lesions for ADC and Fa value were 0.885 and 0.731, respectively. The sensitivity and specificity of ADC and Fa were 87.5% and 84.4%, and 78.1% and 57.8%, respectively. The Az value for discriminating cysts from hemangiomas for Fa was 0.96. The sensitivity and specificity were 90.6% and 92.3%, respectively.

CONCLUSION: Fa values may play a supportive role in the imaging of liver lesions. Whereas metastases tend to have low ADCs and high Fa values, cysts have high ADCs and low Fa values and hemangiomas have high ADCs and high Fa values.