Imaging of small hepatic metastases of colorectal carcinoma: how to use superparamagnetic iron oxide-enhanced magnetic resonance imaging in the multidetector-row computed tomography age?

To compare the accuracy of dynamic contrast-enhanced multidetector-row computed tomography (CT) and superparamagnetic iron oxide-enhanced magnetic resonance imaging (MRI) in the evaluation of small hepatic metastases of colorectal carcinoma. Of 94 patients with colorectal carcinoma analyzed, 76 hepatic metastases (<2 cm) were diagnosed in 17 patients. Superparamagnetic iron oxide (SPIO)-magnetic resonance (precontrast and postcontrast MRI) and dynamic contrast-enhanced multidetector-row CT (dynamic CT [precontrast, arterial, portal-venous, and delayed phase]) were evaluated. The alternative free-response receiver operating characteristic analysis was performed, and the sensitivities and positive predictive values were analyzed. The Az values and sensitivities of portal-venous phase CT, dynamic CT, and SPIO-MRI (0.62/59%, 0.69/61%, and 0.67/61%) were identical. The mean positive predictive value of dynamic CT (82%) was inferior to that of SPIO-MRI (91%). The diagnostic ability of dynamic CT is identical to that of SPIO-MRI in Az value and sensitivity. Superparamagnetic iron oxide-MRI should be recommended only if an equivocal lesion is detected by dynamic CT.