Objective: Evaluation of lead position accuracy may be accomplished by postoperative CT or MRI. Image distortion induced by the lead contacts in MRI question the accuracy of this technique. We compared the electrode position in postoperative CT and MRI by direct fusion of both modalities.

Background: DBS is a well-established treatment for dystonia and PD. Model based programming approaches by visualizing the volume of tissue activated within the individual MRI based anatomy are becoming increasingly important to reduce the postoperative programming burden. Therefore, visual electrode selection and related determination of stimulation parameters in post-OP MRI or CT-MRI fusion is of rising importance.

Methods: After DBS 9 subjects (2 dystonia, Ø age 57.7, 8 male) were investigated by postoperative imaging including MRI T1-MPRAGE (3Tesla, Trio, Siemens Inc, 1mm slices) and CT-scan (64-channel, Philips, 1mm slices) at a minimum of 4 weeks post-operatively to avoid pneumocephalus artefacts. Image analysis was performed in three steps, first direct image fusion of postoperative MRI T1-MPRAGE and postoperative CT was performed (Suretune, Medtronic) , second anterior and posterior commissure distance (AC_PC) and its midpoint were identified and third coordinates of the most distal electrode contact tip relative to AC_PC-midpoint were registered. In either modality coordinates and the average difference of the electrode position were measured taking modality induced MRI or CT artefacts into account.^1,2

Results: 18 electrodes were analyzed. Average vector distances of the distal electrode tip in post-op MRI versus CT fused images was 1.04mm (range 0.1- 2.74mm). Further analysis showed special differences in z coordinates, with significant deeper electrode position in CT versus MRI by a mean of 0.61mm (SD 0.9 mm, p = 0.03*), but no statistically significant differences in other planes by either technique.

Conclusions: Comparison of electrode localization showed on average differences below pixel resolution, although, in few individuals discrepancies above 2 mm were detected. In most patients a systematic deeper localization of the most inferior electrode contact was identified by CT compared to MRI. These findings could be of clinical relevance in attempts of prediction of neurostimulation effects by VTA models. For optimal implementation of postoperative MRI into the control and programming planning work flow, these cases need further systematic analysis.

References:

1. Pollo, C., Villemure, J.-G., Vingerhoets, F., Ghika, J., Maeder, P., & Meuli, R., (2004) Magnetic resonance artifact induced by the electrode Activa 3389 an in vitro and in vivo study. Acta Neurochir 146: 161-164.
    
2. Hemm, S., Coste, J., Gabrillargues, J., Ouchchane, L., Sarry, L., Caire, F., Vassal, F., Nuti, C., Derost, P., Durif, F. & Lemaire, J-J. (2009) Contact position analysis of deep brain stimulation electrodes on post-operative CT images. Acta Neurochir 151:823-829.

« Back to 2017 International Congress

MDS Abstracts - https://www.mdsabstracts.org/abstract/comparison-of-lead-localization-in-postoperative-ct-versus-mri/