MR angiography of the portal and hepatic venous systems: preliminary experience with echoplanar imaging.

Abstract

The purpose of this study was to evaluate the ability of echoplanar MR angiography to depict the major hepatic and portal venous structures. Echoplanar and conventional MR angiographic examinations were performed in 10 subjects (seven healthy volunteers, three patients with focal hepatic lesions). A gradient-recalled echo (GRE) time-of-flight technique (125/10 [TR/TE], 90 degrees flip angle) was used for echoplanar angiography. Eight complete single-excitation images were acquired at each level in 1.5 sec and then collapsed into a single maximal intensity projection. Conventional time-of-flight MR angiography (34/13, 30 degrees flip angle) also was performed. The vascular anatomy from the right atrium to the splenic vein was imaged (6-mm contiguous levels) in three 10.5-sec breath-holds with echoplanar imaging, as compared with seven 11.5-sec breath-holds with conventional MR angiography. Echoplanar and conventional images were compared quantitatively and qualitatively. Echoplanar imaging was 61% faster than conventional MR angiography. Vessel-to-liver signal-intensity ratios were significantly higher for echoplanar imaging (p < .0001), signal-to-noise ratios were significantly higher for conventional MR angiography (p < .0001), and contrast-to-noise ratios were comparable. Qualitatively, echoplanar imaging and conventional MR angiography provided similar anatomic information about the hepatic and portal veins. Angiograms of the hepatic and portal venous systems that are of diagnostic quality can be acquired much more quickly with echoplanar imaging than with conventional MR angiography.