Combined Diffuse Light Reflectance and Electrical Impedance Measurements as a Navigation Aid in Deep Brain Surgery

Abstract

Aim: The aim of this study is to assess reflected light intensity combined with impedance as a navigation aid during stereotactic neurosurgery. Methods: During creation of 21 trajectories for stereotactic implantation of deep brain stimulation electrodes in the globus pallidus internus or subthalamus (zona incerta or subthalamic nucleus), impedance at 512 kHz and reflected light intensity at 780 nm were measured continuously and simultaneously with a radio frequency electrode containing optical fibres. The signals were compared with the anatomy, determined from pre- and post-operative MRI and CT. The measurements were performed within minutes, and signal analysis was done post-operatively. Results: Reflected light intensity was low from the cortex, lateral ventricle, caudate nucleus and putamen; intermediate from the globus pallidus and thalamus; while it was high from the subcortical white matter, internal capsule and subthalamus. The electrical impedance was less consistent, but generally low in the cortex, intermediate in the subcortical white matter, putamen, globus pallidus and thalamus, and high in the internal capsule and subthalamus. Conclusion: Reflected light intensity and electrical impedance give complementary information about passed tissue, and the combination seems promising as a navigation aid during stereotactic neurosurgery.

Intracerebral quantitative chromophore estimation from reflectance spectra captured during deep brain stimulation implantation

“…A previously developed optical system was used for the intracerebral measurements [10,11]. It consists of a spectrometer (AvaSpec-2048-2, Avantes BV, The Netherlands) and a white lamp (AvaLight-Hal-S, Avantes BV, The Netherlands).…”

“…Recently, optical methods for intracerebal guidance and verification of target structures and pre-planned trajectories have been presented [8][9][10][11][12]. These are based on differentiation of grey, light grey and white matter by diffuse light scattering using wavelengths in the near infrared region where the impact of light absorption is very small for short fibre separations.…”

“…These are based on differentiation of grey, light grey and white matter by diffuse light scattering using wavelengths in the near infrared region where the impact of light absorption is very small for short fibre separations. We have used laser Doppler perfusion monitoring (LDPM) [9] and diffuse reflectance spectroscopy (DRS) for such differentiation during clinical creation of trajectories for DBS electrodes [11]. Laser Doppler has the added advantage of measuring not only the total light intensity (tissue greyness) but also the microvascular perfusion in the vicinity of the probe tip.…”

Stereotactic implantation of deep brain stimulation electrodes: a review of technical systems, methods and emerging tools

“…Up to date, the spectral measurements during clinical implantations of DBS electrodes have been used by Giller and co-workers in more than 200 implantation procedures and also been compared with microelectrode recording [35]. The concept developed by Wårdell and colleagues, which is based on both laser Doppler perfusion monitoring (LDPM) [118] and diffuse reflection spectroscopy [2], have been clinically evaluated on more than 50 DBS lead implantations and compared to impedance recordings [58]. This group extracts curve data from specific wavelength intervals e.g.…”

“…The last section differs depending on the target area aimed at. For the GPi a characteristic "double peak", representing light intensity changes during insertion through the white lamina surrounding the Putamen, GPe and GPi has been identified [58] (Fig. 4).…”