Optical coherence tomography of cranial dura mater: Microstructural visualization in vivo

Purpose: The study explores microscope integrated optical coherence tomography (OCT) as a intraoperative imaging technique to delineate the microstructural composition of human dura mater cranialis and underlying leptomeninges for surgical guidance.

Methods: OCT volume scans, light microscopic pictures and light microscopic videos of the dura mater were acquired in patients (n = 20) with indication for craniotomy. OCT volume scans and corresponding light microscopic data were analyzed post procedural. Thickness of anatomical structures was measured during this phase.

Results: OCT scanning of the human cranial dura mater was feasible during microsurgical dissection. A discrimination of the endosteal and inner meningeal layer of the cranial dura mater was possible in 70 % (n = 14) of the patients. Transdural OCT scans could further demonstrate subdural anatomical structures: subdural space 10 % (n = 2), subarachnoid space in 35 % (n = 7), arachnoid vessels in 80 % (n = 16) and brain cortex in 90 % (n = 16) of the patients. Orthogonal distance measurement was possible. The cranial dura mater showed a mean depth of 216 μm, the endosteal layer of 120 μm and the inner meningeal layer of 132 μm. Imaging quality of the dural segment was high - approaching spatial resolution of histopathology. Imaging quality of subdural segments was lower and demonstrated A-line artifacts in 45 % (n = 7).

Conclusion: These results illustrate - for the first time - strengths and weaknesses of three dimensional microscope integrated OCT as an in vivo imaging method of the human cranial dura mater, underlying leptomeninges and human brain cortex as a surgical guidance tool. OCT imaging of the cranial dura mater showed extensive details. Transdural imaging of subdural micro anatomical structures was possible, but showed lower image quality with intermittent A-line artifacts. OCT stated the first intraoperative imaging tool to measure the depth of micro anatomical structures with a high spatial resolution of 7,5 μm.