Diagnosis of Hepatic Metastasis: Comparison of Respiration-Triggered Diffusion-Weighted Echo-Planar MRI and Five T2-Weighted Turbo Spin-Echo Sequences

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Abstract
OBJECTIVE. The purpose of this study was to compare the value of respiration-triggered diffusion-weighted (DW) single-shot echo-planar MRI (EPI) and five variants of T2-weighted turbo spin-echo (TSE) sequences in the diagnosis of hepatic metastasis. MATERIALS AND METHODS. Fifty-two patients with extrahepatic primary malignant tumors underwent 1.5-T MRI that included DW EPI and the following variants of T2-weighted TSE techniques: breath-hold fat-suppressed HASTE, breath-hold fat-supressed TSE, respiration-triggered fat-suppressed TSE, breath-hold STIR, and respiration-triggered STIR. Images were reviewed independently by two blinded observers who used a 5-point confidence scale to identify lesions. Results were correlated with surgical and histopathologic findings and follow-up imaging findings. The accuracy of each technique was measured with free-response receiver operating characteristic analysis. RESULTS. A total of 118 hepatic metastatic lesions (mean diameter, 12.8 mm; range, 3–84 mm) were evaluated. Accuracy values were higher (p < 0.001) with DW EPI (0.91–0.92) than with the T2-weighted TSE techniques (0.47–0.67). Imaging with the HASTE sequence (0.47–0.52) was less accurate (p < 0.05) than imaging with the breath-hold TSE, breath-hold STIR, respiration-triggered TSE, and respiration-triggered STIR sequences (0.59–0.67). Sensitivity was higher (p < 0.001) with DW EPI (0.88–0.91) than with T2-weighted TSE techniques (0.45–0.62). For small (≤ 10 mm) metastatic lesions only, the differences in sensitivity between DW EPI (0.85) and T2-weighted TSE techniques (0.26–0.44) were even more pronounced. CONCLUSION. DW EPI was more sensitive and more accurate than imaging with T2-weighted TSE techniques. Because of the black-blood effect on vessels and low susceptibility to motion artifacts, DW EPI was particularly useful for the detection of small (≤ 10 mm) metastatic lesions.

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