ESTIMATION OF THE ACCURACY OF A SURFACE MATCHING TECHNIQUE FOR REGISTRATION OF EEG AND MRI DATA

Objectives: We developed a method to register EEG and MRT data used fo r the source reconstruction of electric brain activity. Methods: The m ethod is based on matching of the head surfaces as obtained by 3D scan ning after the EEG recording, and by segmentation of MRI data. The reg istration accuracy was estimated by calculating the residual error of the surface matching and its intra-individual and inter-individual var iability. In addition, the test-retest reliability concerning the tran sformation of electrode positions was studied, to estimate how inaccur acies resulting from the 3D scanning of the head surface translate int o registration uncertainty. Results: For 61 measurements, performed on 20 subjects, the average root mean square of the Euclidean distances between the 3D-scanned and the MRI-derived head surfaces amounted to 3 .4 mm. An inter-individual standard deviation of 0.24 mm, and an intra individual standard deviation of 0.003-0.31 mm proved a high inter-and intra-subject stability of the surface matching technique. The variat ion of transformation results when studying the test-retest reliabilit y amounted to 1.6 mm on average. The maximum error of transformation w as smaller than the diameter of the electrodes. Conclusions:The findin gs suggest that the surface matching technique is a precise method for determination of the transformation of electrode positions and MRI da ta into a single co-ordinate system and can successfully be used in a routine laboratory setting. (C) 1998 Elsevier Science Ireland Ltd.