Simulation of reflected light intensity changes during navigation and radio-frequency lesioning in the brain

Abstract

An electrode with adjacent optical fibers for measurements during navigation and radio frequency lesioning in the brain was modeled for Monte Carlo simulations of light transport in brain tissue. Relative reflected light intensity at 780 nm, I 780 , from this electrode and probes with identical fiber configuration were simulated using the intensity from native white matter as reference. Models were made of homogeneous native and coagulated gray, thalamus, and white matter as well as blood. Dual layer models, including models with a layer of cerebrospinal fluid between the fibers and the brain tissue, were also made. Simulated I 780 was 0.16 for gray matter, 0.67 for coagulate gray matter, 0.36 for thalamus, 0.39 for coagulated thalamus, unity for white matter, 0.70 for coagulated white matter and 0.24 for blood. Thalamic matter has also been found to reflect more light than gray matter and less than white matter in clinical studies. In conclusion the reflected light intensity can be used to differentiate between gray and white matter during navigation. Furthermore, coagulation of light gray tissue, such as the thalamus, might be difficult to detect 2 using I 780 , but coagulation in darker gray tissue should result in a rapid increase of I 780 .

Optical and thermal simulations for the design of optodes for minimally invasive optogenetics stimulation or photomodulation of deep and large cortical areas in non-human primate brain

“…Other public MC code are available for the simulation of photon transport Monte Carlo multi layered (MCML), MCextreme or tMCimg [26,42,43], but do not allow to simulate thermal effects simultaneously. MCML has been used to simulate the transport and detection of photons in the context of brain neurosurgery for the safe and accurate positioning of electrodes [44] and is limited to semi-infinite layer geometries. tMCimg and MCextreme allow to simulate more realistic geometries based on segmented MRI or CT images but require data to be formatted into meshed files, which are not straightforward to handle for neurobiologists or neurosurgeons.…”

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

“…Qian and colleagues [101] studied the "look ahead distance" in brain matter by means of Monte Carlo simulation and found that in the near infrared region and for small fiber separation, grey matter is expected to have a slightly increased "look ahead distance" than white matter. This was confirmed by Johansson et al [59]. Nevertheless, the optical resolution is higher than the resolution in a 1.5 Tesla MRI system where imaging is done with 2 mm trans-axial slices.…”

“…In general, the light interaction with tissue, and thus the measurement depth, is affected by several aspects such as probe design, light source and the tissue's scattering and absorption characteristics. Experimental investigations and Monte Carlo simulations show that the optical sampling depth in brain tissue is less than 1 mm [59,71,101]. Qian and colleagues [101] studied the "look ahead distance" in brain matter by means of Monte Carlo simulation and found that in the near infrared region and for small fiber separation, grey matter is expected to have a slightly increased "look ahead distance" than white matter.…”

A laser Doppler system for monitoring cerebral microcirculation: implementation and evaluation during neurosurgery

“…The fibre distances were kept the same resulting in similar sampling volumes. Previous studies based on Monte Carlo simulations using similar optical probe tip designs have estimated the optical sampling depth to approximately 1 mm in brain tissue [16,9,18]. The probe design could also be compared with previous investigations where a subdural optode-strip was used on the brain surface [7,35].…”