Research progress on the use of the optical coherence tomography system for the diagnosis and treatment of central nervous system tumors

Abstract

In central nervous system (CNS) surgery, the accurate identification of tumor boundaries, achieving complete resection of the tumor, and safeguarding healthy brain tissue remain paramount challenges. Despite the expertise of neurosurgeons, the infiltrative nature of the tumors into the surrounding brain tissue often hampers intraoperative differentiation between tumorous and non-tumorous tissue, thus hindering total tumor removal. Optical coherence tomography (OCT), with its unique advantages of high-resolution imaging, efficient image acquisition, real-time intraoperative detection, and radiation-free and noninvasive properties, offers accurate diagnostic capabilities and invaluable intraoperative guidance for minimally invasive CNS tumor diagnosis and treatment. Various OCT systems have been employed in neurological tumor research, including polarization-sensitive OCT systems, orthogonal polarization OCT systems, Doppler OCT systems, and OCT angiography systems. In addition, OCT-based diagnostic and therapeutic techniques have been explored for the surgical resection of CNS tumors. This review aims to compile and evaluate the research progress surrounding the principles of OCT systems and their applications in CNS tumors, providing insights into potential future research avenues and clinical applications.

Keywords: animal models; intraoperative real‐time detection; optical coherence tomography system; tumor boundary detection.

Figure 1

Cortical cross‐sectional optical coherence tomography scans of normal brain tissue and glioma tissue. The figures on the left show normal tissue, while the figures on the right exhibit glioma tissue. (A) Arachnoid space, (B) blood vessels, (C) vessel shadows, and (D) blood. [Color figure can be viewed at wileyonlinelibrary.com]

Figure 2

SS‐OCT/FD‐OCT image of a glioma specimen with a passive polarization delay unit (A–C) and OCT surface map of the glioma specimen showing the vasculature (D–F). (A) Setup program of SS‐OCT. The sample illumination path contains a polarization delay unit. The sample and reference beams interfere at the unpolarized beam splitter and are then split into orthogonally polarized components by the polarizing beam splitter. (B) Passive delay cell scheme. (C) Demonstration of the phase difference between orthogonal detection channels. (D) A general view of the surface of an ex vivo glioma specimen (approximately 5 × 5 mm in size) showing vasculature (arrows). (E) The OCT grayscale sequence surface map shows iso‐ and hyperintensity in the tumor area and hypointensity in the vascular area (arrows). (F) A surface scan enhancement image showed that the tumor area was hyperintensity, and the blood vessel area was hypodense (arrows). OCT, optical coherence tomography; SS‐OCT, Swept‐source optical coherence tomography; SS‐OCT/FD‐OCT, Swept‐source/Fourier domain optical coherence tomography. [Color figure can be viewed at wileyonlinelibrary.com]

Figure 3

Application of the optical coherence tomography (OCT) system in detecting tumor boundaries in glioma in an SD rat in vivo. (A) Preoperative intracranial magnetic resonance T2 imaging showing a glioma located in the right frontal lobe in an SD rat (triangular arrows). (B) The rat was properly immobilized after induction of anesthesia, and the anesthesia was maintained by a mask. The limbs were affixed with electrocardiograph (ECG) monitoring clips and oxygen saturation detection clips, and an anal temperature monitor was inserted into the anus. (C) The ECG monitor displayed the animal's electrocardiogram, heart rate, oxygen saturation, respiratory rate, and body temperature so that we could adjust anesthesia parameters such as isoflurane concentration and oxygen flow according to the monitoring of vital signs during surgery to ensure safe tumor boundary detection in vivo. (D, E) After craniotomy, the bone window was removed, the brain tissue covering the surface of the tumor was removed, the tumor area was exposed, and the area of interest (green box) was detected in real time without any touching the OCT system. (F) A B‐scan grayscale map of this region shows the boundary between the tumor and the peritumoral normal brain tissue (orange dashed line). The left side of the dashed line is the hypointense region indicating the tumor (* in D), and the right side of the dashed line is the hyperintense region indicating the peritumoral normal brain tissue (# in D). (G) The two‐dimensional color map reconstructed using ImageJ software showed that the tumor area was dominated by lower color levels (e.g., green), while the peritumoral normal brain tissue contained higher color levels (e.g., blue). The (H) chart is a reference scale for the color visualization transformation of the gray value from 0–255 of the (G) chart. ECG, electrocardiography; OCT, optical coherence tomography. [Color figure can be viewed at wileyonlinelibrary.com]

Figure 4

Intraoperative OCT imaging during glioblastoma resection. (A)Collagen‐rich cortical scar H&E stained (left) with deposition of iron‐pigmented macrophages (right; Berlin blue reaction). (B) Microcystic changes within the tumor infiltration zone. (C) Vascular proliferation and pleomorphic tumor cells. (D) Pleomorphic tumor cells within the tumor center (right) and tumor necrosis (left). H&E, hematoxylin and eosin; OCT, optical coherence tomography. [Color figure can be viewed at wileyonlinelibrary.com]

Figure 5

Typical OCT cross‐sectional image of low‐grade glioma tissue. (A) The image covers a width and depth of 1.5 × 0.7 mm and allows the identification of typical microstructures such as glioblastoma multiforme (blue arrows), mucin‐like stroma (green arrows), and gliomas (orange arrows), as well as vesicles (red arrows) and fibers (yellow arrows). (B) Histology typical histological images of glioma tissue images with hematoxylin and eosin: ×100. OCT, optical coherence tomography. [Color figure can be viewed at wileyonlinelibrary.com]

Figure 6

The machine learning‐based tissue types differentiation task by OCT system, including necrosis, significant tumor, and healthy tissue. Examples of analyzed tissue types: (A) Necrosis, (B) Vital tumor, and (C) Healthy tissue. The left panel represents a general photograph of the tissue sample, with the square in the image marking the mid‐column OCT B‐scan on the surface of the acquired image of the entire volume; the dotted line indicates the actual location of the OCT B‐scan shown. Photos show tissue samples with OCT B‐scans (middle panel) and histology slides (right panel). OCT reveals smooth, healthy tissue (C) versus irregular necrosis (A) and tumor (B). Histology shows acellular necrosis (A), high cellularity in tumor (B), and structured healthy tissue (C) with glial cells. Dashed lines in photos mark OCT scan positions. Automated tissue classification was verified by histological examination to accurately classify necrotic, vital tumor, and healthy brain tissue. OCT, optical coherence tomography. [Color figure can be viewed at wileyonlinelibrary.com]

Figure 7

Mind map of the full text. With the advantages of high‐resolution imaging, efficient image acquisition, intraoperative real‐time detection, and radiation‐free and noninvasive characteristics, OCT provides accurate diagnosis and effective intraoperative guidance for the minimally invasive diagnosis and treatment of CNS tumors. These methods include swept‐source OCT, polarization‐sensitive OCT, orthogonal polarization OCT, Doppler OCT, and OCT angiography. This review summarizes the relevant literature and the research progress on the roles and applications of OCT in CNS tumors, provides a synopsis of the advantages of the OCT system in the surgical guidance and diagnosis of CNS tumors based on the detection of the OCT system, and introduces relevant clinical studies on the integration of the OCT system with other neurosurgical therapeutic techniques for the treatment of CNS tumors to provide prospects for future research directions. CNS, central nervous system; OCT, optical coherence tomography. [Color figure can be viewed at wileyonlinelibrary.com]