Quantitative nontumorous and tumorous human brain tissue assessment using microstructural co- and cross-polarized optical coherence tomography

Abstract

Optical coherence tomography (OCT) is a promising method for detecting cancer margins during tumor resection. This study focused on differentiating tumorous from nontumorous tissues in human brain tissues using cross-polarization OCT (CP OCT). The study was performed on fresh ex vivo human brain tissues from 30 patients with high- and low-grade gliomas. Different tissue types that neurosurgeons should clearly distinguish during surgery, such as the cortex, white matter, necrosis and tumorous tissue, were separately analyzed. Based on volumetric CP OCT data, tumorous and normal brain tissue were differentiated using two optical coefficients — attenuation and forward cross-scattering. Compared with white matter, tumorous tissue without necrotic areas had significantly lower optical attenuation and forward cross-scattering values. The presence of particular morphological patterns, such as necrosis and injured myelinated fibers, can lead to dramatic changes in coefficient values and create some difficulties in differentiating between tissues. Color-coded CP OCT maps based on optical coefficients provided a visual assessment of the tissue. This study demonstrated the high translational potential of CP OCT in differentiating tumorous tissue from white matter. The clinical use of CP OCT during surgery in patients with gliomas could increase the extent of tumor resection and improve overall and progression-free survival.

Optical coefficients as tools for increasing the optical coherence tomography contrast for normal brain visualization and glioblastoma detection

“…However, the tendency of statistically higher values of the white matter in cochannel attenuation coefficient in comparison to tumor tissue is present in both studies (p < 0.001). Moreover, in our previous study, 27 it was shown that the presence of particular morphological patterns can lead to dramatic changes in coefficient values and that the cortex shows attenuation coefficients in the range of that of different tumor types. It should be noted that these calculations of the coefficients were made while disregarding the confocal factor of the OCT setup.…”

“…Quantitative assessment of the OCT data can be based on the calculation of optical coefficients, for example, the attenuation coefficient [7][8][9][10]27 or machine-learning (classification) methods 28,29 and seems to be more objective. In patients, Böhringer et al 8 used an attenuation coefficient calculated from the log scale attenuation curves of areas with a homogeneous signal in the cross-section images, thus describing the linear part of the attenuation curve, but no data relating to sensitivity or specificity were demonstrated.…”

Parametric imaging of attenuation by optical coherence tomography: review of models, methods, and clinical translation

“…Demonstrations on human and rat brain tissues have indicated the potential for differentiation of cancer and normal tissue. 94,137 We finally observe that, as well as optical properties, parametric OCT imaging can also be used to observe mechanical properties of tissue. 138,139 All such properties, optical and otherwise, show great potential to be combined with OCT attenuation imaging to provide a more comprehensive assessment of tissues.…”

“…Similar contrast was recently reported by Almasian et al 93 from an in vivo study, as summarized in Table 3. A recent study on ex vivo human brain tissue by Yashin et al 94 reported consistently lower attenuation coefficients of the tumorous tissue than the normal tissue. In addition, they observed a significant influence of tumor necrosis on the measured attenuation coefficients.…”

“…133,134 Finally, retrieval of diattenuation-the polarization state-dependent differential attenuation-is also possible via PS-OCT but to the authors' knowledge is thought to be a small effect and has not yet been widely investigated. 135,136 Also based on polarization detection, Yashin et al 94 recently used crosspolarization OCT to simultaneously measure the attenuation coefficients of the co-and crosspolarized detected light. Demonstrations on human and rat brain tissues have indicated the potential for differentiation of cancer and normal tissue.…”