Improvements in volumetric quantification of circumscribed hepatic lesions by three dimensional sonography

The size of hepatic tumors is commonly estimated by ultrasound as well as by computed tomography by measuring the three diameters followed by computing of the volume by applicating the ellipsoid formula. Using the new technique of three-dimensional-sonography it is possible to perform volume measurement by computer-linked planimetry. Initial tests with water filled balloons of defined volume revealed the accuracy (mean error of 3.0%) and high reproducibility (low intra- and inter-observer variance) of the method applied by one investigator (intraindividual SD +/- 1.3%) as well as by four different investigators (interindividual SD +/- 2.1%). Circumscribed hepatic lesions of 63 patients were investigated by using conventional sonography (ellipsoid formula), computed tomography (ellipsoid formula) and three-dimensional-sonography (ellipsoid formula, ortrip, planimetry). As a volume of reference a mathematical approximation for infinite sonographical slices (planimetry) of a very well circumscribed hemangioma of the liver was defined. Based on these results a mean error of -6% (SD +/- 39%) was determined for conventional sonography. For computed tomography a mean error of 2+ (SD +/- 35%) was found, for three-dimensional-sonography that figure was -6% (SD +/- 5%). Follow up investigations can only demonstrate significant alterations of volume when the SD-interval is exceeded. Therefore, three-dimensional-sonography provides a more sensitive and reliable recognition of volumetric changes of liver tumors than conventional sonography or computed tomography does.