Determination of liver volume in vivo in rats using MRI

Accurate estimation of the liver volume may be important for the diagnosis of several pathological processes in patients and for the study of new therapies in experimental oncology. Although sonography and computed tomography (CT) have been used for this purpose in patients, the lack of spatial resolution and tissue differentiation is a source of measurement errors which, at present, makes it impossible to accept sonography and CT widely for the determination of the liver volume. In the present study, the liver volumes of seven rats were measured by magnetic resonance imaging (MRI) and an automated image analysis system before and after the animals were killed. Volume computation was carried out by adding up the individual volumes in the sequential MR sections. Adequate MR images with high contrast between the liver and surrounding structures were obtained with spin echo pulse sequence and retarded phase encoding while no contrast material was used. The mean volumes of the livers measured by MR in vivo and in cadavers were 11.91 +/- 0.40 and 11.92 +/- 0.45 ml, respectively. When compared with the actual liver volumes measured in vitro after resection, the errors of determinations in vivo and in cadavers were as small as 3.1 and 2.1%, respectively. These data indicate that MR imaging is an accurate means to determine the liver volume in vivo and that it may be potentially useful to measure small intrahepatic lesions in patients.