Purpose: CT series can be used to define a reference position forcorrection of tumor alignment in radio therapeutic cancer treatmentby comparison of the projected slices to digital radiographic images.Because the pose of the CT dataset with respect to the table is apriori unknown, a method is introduced that automatically evaluatesthe placement of a table inlay and generates absolute CT coordinates.Methods and Materials: CT slices of different sections of a patienton a CT table with an inlay were used to determine the actual tableposition and pitch angle with respect to a fixed coordinate system.The inlay was designed so that it was possible to unambiguously identifya respective table section by just one single CT slice. Automaticmatching of the partly recorded inlay with a given model of the geometrygives the absolute position of the table origin and pitch. Resultsfrom manual 3D matching of the model to the inlay were taken as thegold standard.Results: Comparisons to the manual determination of the table alignmentshow that the absolute position of the table origin can be foundwith an accuracy of ±0.5 times the voxel size. The deviation of thepitch value lies within ±0.1°.Conclusion: Automatic model based matching of a table inlay providesa fast and accurate method to determine absolute CT table coordinates.The method can increase the reliability of alignment correction proceduresand offers a practical solution to the problem of the absence ofabsolute CT coordinates.     «

Purpose: CT series can be used to define a reference position forcorrection of tumor alignment in radio therapeutic cancer treatmentby comparison of the projected slices to digital radiographic images.Because the pose of the CT dataset with respect to the table is apriori unknown, a method is introduced that automatically evaluatesthe placement of a table inlay and generates absolute CT coordinates.Methods and Materials: CT slices of different sections of a patienton a CT table with an inlay wer...     »