A roentgen stereophotogrammetric system. Construction, calibration and technical accuracy

The principles for a system of roentgen stereophotogrammetric analysis for experimental and clinical applications are presented. Only the positions of implanted reference markers in the investigated object are measured. Tantalum balls, 0.5 or 0.8 mm in diameter, are used as reference markers. Standard roentgen equipment, permitting simultaneous exposure from two roentgen tubes, is employed. The calibration equipment, a glass calibration cage containing radiopaque markers, introduces a rectangular laboratory coordinate system in the roentgen investigation. The calibration of the calibration equipment itself and the obtained methodologic accuracy in determining distances, volumes and movement parameters is described for various film/screen and marker combinations.