Abstract: A method of interactive quantification of digitized 3D objects includes a determination of coordinates of observed screen space using a camera that senses the position of pupils of the operator gazing on the screen. Dimensions of studied sub-volume of VOI block of dimensions of Sx, Sy, Sz or VOI cylinder of dimensions of Sx=Sy=Sxy are defined. An analyzed particle and VOI position is selected. A VOI is visualized. Observed space is corrected by VOI visualization. The last level is selected by gaze of the operator from the sequence of probe levels and the gaze is focused on the last level on which the particle is still visible. The property of the marked particle in 3D space is verified, and marked with a color mark. The mark position is determined by interpolation or by finding a representative point.