Purpose: To evaluate the usefulness of the alternate display of arterial and equilibrium phase images (ADAEI) of 2 mm-pitch reconstruction computed tomography (CT) in the detection of hepatocellular carcinoma (HCC).
Materials and methods: One hundred and eleven nodules in 72 patients were confirmed as HCC by radiology, histology, or clinical course. Blinded to the outcome, we retrospectively reviewed the CT images obtained with dual-phase spiral CT (Radix Prima, Hitachi Medical, Tokyo, Japan) by ADAEI and by conventional display on cut films. Scanning for the arterial and equilibrium phases was initiated at 33 and 120 s, respectively, after starting the injection of contrast medium (iopamidol 3 ml/s) with a section thickness of 5 mm and a table feed speed of 5-7 mm/s. In ADAEI, all images were reconstructed with a 2-mm interval, and displayed on the monitor in an alternating fashion so that an image in the arterial phase was followed by the corresponding image in the equilibrium phase, and then by the next pair of images in the craniocaudal direction.
Results: All 20 HCC nodules larger than 20 mm in diameter were detected by both ADAEI and the conventional display (NS). On the other hand, detectability of smaller HCC nodules was 91/91 (100%) and 72/91 (79%), respectively (P<0.0001 by McNemar' test). False-positively identified HCC nodules, including those diagnosed as possible HCC, were 11 by ADAEI and eight by conventional display.
Conclusion: The novel, alternate display, ADAEI of 2 mm-pitch reconstruction CT images was useful in detecting small HCC nodules while not requiring additional equipment or expense.