CLINICAL ARTICLE Is MRI a reliable tool to locate the electrode after deep brain stimulation surgery? Comparison study of CT and MRI for the localization of electrodes after DBS Ji Yeoun Lee & Jin Wook Kim & Jee-Young Lee & Yong Hoon Lim & Cheolyoung Kim & Dong Gyu Kim & Beom Seok Jeon & Sun Ha Paek Received: 12 October 2009 / Accepted: 13 August 2010 / Published online: 30 September 2010 # Springer-Verlag 2010 Abstract Purpose MRI has been utilized to localize the electrode after deep brain stimulation, but its accuracy has been questioned due to image distortion. Under the hypothesis that MRI is not adequate for evaluation of electrode position after deep brain stimulation, this study is aimed at validating the accuracy of MRI in electrode localization in comparison with CT scan. Methods Sixty one patients who had undergone STN DBS were enrolled for the analysis. Using mutual information technique, CT and MRI taken at 6 months after the operation were fused. The x and y coordinates of the centers of electrodes shown of CT and MRI were compared in the fused images to calculate average difference at five different levels. The difference of the tips of the electrodes, designated as the z coordinate, was also calculated. Results The average of the distance between the centers of the electrodes in the five levels estimated in the fused image of brain CT and MRI taken at least 6 months after STN DBS was 1.33 mm (0.1–5.8 mm). The average discrepancy of x coordinates for all five levels between MRI and CT was 0.56±0.54 mm (0–5.7 mm), the discrepancy of y coordinates was 1.06±0.59 mm (0–3.5 mm), and for the z coordinate, it was 0.98±0.52 mm (0–3.1 mm) (all p values <0.001). Notably, the average discrepancy of x coordinates at 3.5 mm below AC–PC level, i.e., at the STN level between MRI and CT, was 0.59±0.42 mm (0–2.4 mm); the discrepancy of y coordinates was 0.81±0.47 mm (0–2.9 mm) (p values<0.001). Conclusions The results suggest that there was significant discrepancy between the centers of electrodes estimated by CT and MRI after STN DBS surgery. Keywords CT . DBS . Electrode localization . Image fusion . MRI . Parkinson's disease Introduction Deep brain stimulation (DBS) of the subthalamic nucleus (STN) has been proven as effective for the management of the advanced Parkinson's disease (PD) patients treated with long-term use of anti-PD drugs [12, 13]. The accurate J. Y. Lee : J. W. Kim : Y. H. Lim : D. G. Kim : S. H. Paek (*) Department of Neurosurgery, Seoul National University College of Medicine, 28 Yeongeon-dong, Jongno-gu, Seoul 110-744, South Korea e-mail: paeksh@snu.ac.kr J.-Y. Lee : B. S. Jeon (*) Department of Neurology, Seoul National University College of Medicine, 28 Yeongeon-dong, Jongno-gu, Seoul 110-744, South Korea e-mail: brain@snu.ac.kr S. H. Paek Ischemic/Hypoxic Disease Institute, Seoul National University College of Medicine, Seoul, South Korea S. H. Paek Cancer Research Institute, Seoul National University College of Medicine, Seoul, South Korea B. S. Jeon : S. H. Paek Clinical Research Institute, Seoul National University Hospital, Seoul, South Korea C. Kim Medical Imaging Laboratory, CyberMed, Inc., Seoul, South Korea Acta Neurochir (2010) 152:2029–2036 DOI 10.1007/s00701-010-0779-2