Abstract: Objective Point matching method is widely used in the spatial registration of computer assisted intervention system. There are three kinds of errors defined in point matching:fiducial localization error (FLE), fiducial registration error (FRE), and target registration error (TRE). The relationship among these errors, and its impact on clinical application were studied in this article. Methods The CT image data was utilized to simulate the spatial registration in order to study the relationship among three kinds of errors. Different number of fiducial points and different models of the FLE (Gaussian model and non-Gaussian model) were used to conduct the simulation. Results Both the FRE and the TRE increased along with the increase of the magnitude of the FLE. Under the same FLE model, FRE increased but TRE decreased along with the increase of the number of fiducial points. When Gaussian model of FLE was used, the FRE and the TRE was uncorrelated. When the non-Gaussian model of FLE was used, the correlation coefficient between FRE and TRE was approximately 0.35. Conclusion When different number of fiducial points are used, the spatial registration accuracy cannot be compared according to the average TRE. When the same fiducial configuration is used, weather or not the average FRE reflects the accuracy of spatial registration depends on the underlying distribution model of the FLE.

Key words: Point matching, Spatial registration, Computer assisted intervention