Small hepatocellular carcinoma: assessment with T1-weighted spin-echo magnetic resonance imaging with and without fat...

We examined the detectability of small hepatocellular carcinomas (HCCs) and the factors that affect hyperintensity of small HCC on T1-weighted images (T1W) by using T1-weighted fat-suppressed images (T1FS).

Thirty-nine HCCs (29 patients) measuring 30 mm or less were enrolled. The mean size of HCCs was 21.0+/-4.9 mm. Spin-echo T1W, T2-weighted images (T2W), and T1FS were obtained using a 1.5 T system. We evaluated the detectability in each sequence by receiver-operating-characteristic (ROC) analysis and the tumor-to-hepatic parenchyma contrast-to-noise ratio (CNR), the variance in the detectability among all interpreters with each sequence, and the presence or absence of improvement in the detectability by interpreting T1FS in addition to conventional T1W plus T2W. The contents of fat, copper, and iron in histologically diagnosed HCCs showing hyperintensity on both T1W and T1FS were measured. For determination of heavy metals, we used a particle induced X-ray emission analytical instrument.

ROC analyses revealed that T1FS were superior to T1W and T2W in detecting small HCCs (0.900+/-0.017 for T1FS, 0.859+/-0.019 for T1W, and 0.745+/-0.030 for T2W). The detectability by interpreting T1FS in addition to conventional T1W plus T2W was improved (0.931+/-0.013 for the conventional images and 0.973+/-0.008 for the conventional images plus T1FS, P<0.001). The detected lesions on T1FS demonstrated favorable CNR values. The copper content in the cancer and the ratio of the copper content in the cancer to that in the non-cancerous tissue were 275.4+/-219.0 microg/g dry weight, 6.9+/-5.5 in HCCs showing hyperintensity on both T1W and T1FS. Both were significantly higher (P<0.05).

T1FS showed excellent sensitivity and specificity in detecting small HCCS irrespective of the experience of interpreters. The use of T1FS suggested the involvement of copper might be one of the factors in hyperintensity of HCCs on T1W.