Real-time display of intracranial subdural electrodes and the brain surface during an electrode implantation procedure using permeable film

Abstract

Background: Subdural electrode (SDE) implantation is an important method of diagnosing epileptogenic lesions and mapping brain function, even with the current preference for stereoelectroencephalography. We developed a novel method to assess SDEs and the brain surface during the electrode implantation procedure using brain images printed onto permeable films and intraoperative fluoroscopy. This method can help verify the location of the electrode during surgery and improve the accuracy of SDE implantation.

Methods: We performed preoperative imaging by magnetic resonance imaging and computed tomography. Subsequently, the images were edited and fused to visualize the gyrus and sulcus better. We printed the images on permeable films and superimposed them on the intraoperative fluoroscopy display. The intraoperative and postoperative coordinates of the electrodes were obtained after the implantation surgery, and the differences in the locations were calculated.

Results: Permeable films were created for a total of eight patients with intractable epilepsy. The median difference of the electrodes between the intraoperative and postoperative images was 4.6 mm (Interquartile range 2.9-7.1). The locations of electrodes implanted outside the operation field were not significantly different from those implanted inside.

Conclusion: Our new method may guide the implantation of SDEs into their planned location.

Keywords: Accuracy of the implanted electrode; Epilepsy surgery; Real-time display; Subdural electrode implantation.

Figure 1:

Processing images obtained before surgery. (a) A three-dimensional (3D) brain image is reconstructed using magnetic resonance fast spoiled gradient echo images. (b) Fusion images of 3D brain and bone images. (c) Edited image. (d) The edited image is printed on the permeable film.

Figure 2:

Postoperative images to evaluate the distance error. (a) Postoperative fusion image. The location of the electrodes is reconstructed from computed tomography images and three-dimensional brain images from preoperative magnetic resonance images. The subdural electrodes are colored blue. (b) Intraoperative fluoroscopy image of patient 1. The subdural electrodes are colored green. (c) The superimposed image of (a and b). The coordinates are obtained from this image.

Figure 3:

Box plot showing the distance error (DE) of the electrodes. Vertical axis indicates the DE in mm. (a) Box plot showing the DE of the electrodes for each patient. The median DE is indicated by a horizontal line within the box; error bars indicate the interquartile range. (b) Box plot showing the DE of electrodes implanted outside or inside the operation field. Horizontal lines within the box and error bars indicate the same as that stated in panel A. n s: not significant