Hepatic Lesion Detection: Comparison of MR Imaging after the Administration of Superparamagnetic Iron Oxide with Dual-Phase CT by Using Alternative-Free Response Receiver Operating Characteristic Analysis

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Abstract
PURPOSE: To compare the performance of magnetic resonance (MR) imaging after the administration of superparamagnetic iron oxide (SPIO) and dual-phase computed tomography (CT) in the depiction of liver metastases. MATERIALS AND METHODS: Fifty-one hepatic resection candidates with known colorectal metastases were examined. MR imaging comprised fast spin-echo (SE) T2-weighted imaging, T1-weighted gradient-echo (GRE) fast low-angle shot imaging before SPIO enhancement, dual-echo SE imaging, T2-weighted fast low-angle shot imaging, and T1-weighted GRE imaging after SPIO enhancement. CT was performed with 8-mm collimation and 1:1 pitch; imaging commenced 20 seconds and 65–70 seconds after injection of 150 mL of contrast medium. All images were reviewed independently by four blinded observers. The alternative–free response receiver operating characteristic (ROC) method was used to analyze the results, which were correlated with findings from surgery, intraoperative ultrasonography, and histopathologic studies in 31 patients and with consensus review together with all other imaging and clinical follow-up in 20 patients. Sensitivities were also calculated. RESULTS: The mean sensitivity of MR was significantly higher than that of CT (P < .02): 79.8% for MR and 75.3% for CT for all lesions, and 80.6% for MR and 73.5% for CT for malignant lesions. The mean areas under the alternative–free response ROC curves were 0.83 for MR and 0.78 for CT (difference not significant). CONCLUSION: SPIO-enhanced MR imaging was more sensitive than dual-phase CT in the depiction of colorectal metastases.