PLANIMETRIC VOLUMETRY OF THE PROSTATE - HOW ACCURATE IS IT

Planimetric volumetry is used in clinical practice when accurate volum e determination of the prostate is needed. The prostate volume is dete rmined by discretization of the 3D prostate shape. The area of the pro state is calculated in consecutive ultrasonographic cross-sections. Th is area is multiplied by the distance between the cross-sections and t he total Volume is determined by summation of all contributions. Besid es the quality of the automated outlining, the accuracy of this method depends on this intersection distance and on the angle of the scan pl ane with the probe. Also, the location of the first cross-section is o f influence. This paper describes the influences of these parameters o n the accuracy of the volume determination using a simple prostate mod el. This theoretical influence is compared to clinical volume determin ations using automated planimetric volumetry with different step sizes . From our data, it is concluded that a step size of 4 mm for planimet ric prostate volume determination is a good compromise between investi gation time and accuracy in a clinical setting.