To investigate the efficacy of SPIO (superparamagnetic iron oxide) enhanced MR imaging for the detection of colorectal liver metastasis, compared to the intraoperative ultrasound (IOUS).

Thirteen patients who underwent IOUS during surgery for colorectal liver metastasis as well as a liver MR before and after administration of SPIO. The mean patient age was 57 years (age range: 43-77). Two observers reviewed the SPIO-enhanced MR via a double blind test. We evaluated the efficacy of the SPIO-enhanced MR compared to the results of IOUS.

Following IOUS, 55 lesions were found, including 32 metastases, 20 cysts, 2 calcifications, and 1 coagulation necrosis. The interobserver correlation of the SPIO-enhanced MR is significant, with a kappa index of 0.839. Radiologist 1 and 2 missed three lesions in three patients. Two of the patients had multiple liver lesions (six and eight, respectively), whereas the other patient had tumor recurrence following hepatic surgery for liver metastasis. In the other nine patients, MR detected all lesions. The sensitivity and positive predictive value of the SPIO-enhanced MR was 94.5%, and 100%, respectively.

The SPIO-enhanced liver MR shows a good correlation to IOUS, especially in the case of patients who had fewer than three lesions. Therefore, the SPIO-enhanced MR may help to plan a surgical resection of colorectal liver metastasis.