The effects of section thickness on the estimation of liver volume by the Cavalieri principle using computed tomography images.

Estimation of liver volume using routine CT scans has been described previously. We have, however, not found a gold standard study which analyzes the effect of section thickness on the estimation of liver volume using CT images. In the present study, five normal livers obtained from cadavers were scanned using a Spiral CT Scanner (Xpress/GX Toshiba, Tocigi-Ken) in the horizontal plane. Consecutive sections at a thickness of 10, 5 and 1mm were used to estimate the total volume of the livers by means of the Cavalieri principle. With a view to evaluating inter-observer differences, liver volume was estimated by three observers. The estimated volume using the classical volume estimation formula did not concur with the actual volume of the livers obtained by the fluid displacement technique. The section thickness has an over- or under-projection effect on the estimated volume. The obtained volume estimation results were, therefore, calibrated using three different approaches. The volume obtained by the calibration formulae did not differ statistically from actual liver volumes (P<0.05). There were also no significant differences between the performers' estimates (P>0.05). Results showed that the effect of section thickness on the volume estimates could not be omitted and the obtained values could be calibrated using the proposed approaches presented in this study.