In Vivo Microscopy in Neurosurgical Oncology

An actively stabilized, miniaturized epi-fluorescence widefield microscope for real-time observation in vivo

Recent developments in real-time, in vivo micro-imaging have allowed for the visualization of tissue pathological changes, facilitating rapid diagnosis. However, miniaturization, magnification, the field of view, and in vivo image stabilization remain challenging factors to reconcile. A key issue for this technology is ensuring it is user friendly for surgeons, enabling them to use the device manually and obtain instantaneous information necessary for surgical decision-making. This descriptive study introduces a handheld, actively stabilized, miniaturized epi-fluorescence widefield microscope (MEW-M) for real-time observation in vivo with high resolution. The methodology of MEW-M system includes high resolution microscopy miniaturization technology, thousandfold shaking suppression (actively stabilized), ultra-photosensitivity, and tailored image signal processing cell image capture and processing technology, which support for the excellent real-time imaging performance of MEW-M system in brain, mammary, liver, lung, and kidney tissue imaging of rats in vivo. With a single-objective and high-frame-rate imaging, the MEW-M system facilitates roving image acquisition, enabling contiguous analysis of large tissue areas. RESEARCH HIGHLIGHTS: A handheld, actively stabilized MEW-M system was introduced. Excellent real-time, in vivo imaging with high resolution and active stabilization in brain, mammary, liver, lung, and kidney tissue of rats.

Deep Learning-Assisted Segmentation and Classification of Brain Tumor Types on Magnetic Resonance and Surgical Microscope Images

OBJECTIVE

The primary aim of this research was to harness the capabilities of deep learning to enhance neurosurgical procedures, focusing on accurate tumor boundary delineation and classification. Through advanced diagnostic tools, we aimed to offer surgeons a more insightful perspective during surgeries, improving surgical outcomes and patient care.

METHODS

The study deployed the Mask R-convolutional neural network (CNN) architecture, leveraging its sophisticated features to process and analyze data from surgical microscope videos and preoperative magnetic resonance images. Resnet101 and Resnet50 backbone networks are used in the Mask R-CNN method, and experimental results are given. We subsequently tested its performance across various metrics, such as accuracy, precision, recall, dice coefficient (DICE), and Jaccard index. Deep learning models were trained from magnetic resonance imaging and surgical microscope images, and the classification result obtained for each patient was combined with the weighted average.

RESULTS

The algorithm exhibited remarkable capabilities in distinguishing among meningiomas, metastases, and high-grade glial tumors. Specifically, for the Mask R-CNN Resnet 101 architecture, precision, recall, DICE, and Jaccard index values were recorded as 96%, 93%, 91%, and 84%, respectively. Conversely, for the Mask R-CNN Resnet 50 architecture, these values stood at 94%, 89%, 89%, and 82%. Additionally, the model achieved an impressive DICE score range of 94%-95% and an accuracy of 98% in pathology estimation.

CONCLUSIONS

As illustrated in our study, the confluence of deep learning with neurosurgical procedures marks a transformative phase in medical science. The results are promising but underscore diverse data sets' significance for training and refining these deep learning models.

Comparison of Short-Term Surgery Outcomes and Clinical Characteristics Between Elderly and Non-Elderly Patients with Middle Third Parasagittal and Parafalcine Meningiomas

Purpose

This study aims to compare the short-term surgery outcomes of the resection of meningiomas and clinical characteristics between elderly and non-elderly patients.

Patients and Methods

This retrospective study included patients who underwent a resection of middle third parasagittal and parafalcine meningiomas between January 2011 and December 2020. All lesions arise from the middle third of the parafalcine or infiltrate superior sagittal sinus (SSS). The clinical characteristics studied included neurological deficit, peritumoral brain edema (PTBE), SSS invasion, tumor size, and symptoms; perioperative complications, and short-term surgery outcomes including neurological deficit, operative blood loss, postoperative hospitalization duration, and WHO classification were compared.

Results

A total of 43 elderly patients and 63 non-elderly patients were included. Compared with non-elderly patients, elderly patients had larger lesions (P = 0.013) and presented with a larger PTBE (P = 0.019). SSS blockage was identified in 28.57% of elderly patients and 19.57% of non-elderly patients. Compared with non-elderly patients, elderly patients tended to suffer from more aggressive lesions (WHO II/III meningioma 6 vs 3, P = 0.154) and presented with longer postoperative hospital stays (17.25 ± 5.8 vs 13.50 ± 3.8, P = 0.009); conversely, while the non-elderly patients experienced more blood loss (P = 0.022) and had more perioperative reoperations (3 vs 1). No significant difference in neurological deficit was detected between the two groups (P = 0.97). After total tumor resection, patients with neurological deficits in both groups can recover during the follow-up period.

Conclusion

Among the 106 patients with middle third parasagittal and falx meningiomas in our hospital, elderly patients had larger lesions, presented with more severe PTBE, and had longer postoperative hospital stays than younger patients. Conversely, younger patients had more blood loss and serious complications than elderly patients. Postoperative neurological dysfunction in elderly patients was similar to that in middle-aged and young patients.

OCT-Guided Surgery for Gliomas: Current Concept and Future Perspectives

Optical coherence tomography (OCT) has been recently suggested as a promising method to obtain in vivo and real-time high-resolution images of tissue structure in brain tumor surgery. This review focuses on the basics of OCT imaging, types of OCT images and currently suggested OCT scanner devices and the results of their application in neurosurgery. OCT can assist in achieving intraoperative precision identification of tumor infiltration within surrounding brain parenchyma by using qualitative or quantitative OCT image analysis of scanned tissue. OCT is able to identify tumorous tissue and blood vessels detection during stereotactic biopsy procedures. The combination of OCT with traditional imaging such as MRI, ultrasound and 5-ALA fluorescence has the potential to increase the safety and accuracy of the resection. OCT can improve the extent of resection by offering the direct visualization of tumor with cellular resolution when using microscopic OCT contact probes. The theranostic implementation of OCT as a part of intelligent optical diagnosis and automated lesion localization and ablation could achieve high precision, automation and intelligence in brain tumor surgery. We present this review for the increase of knowledge and formation of critical opinion in the field of OCT implementation in brain tumor surgery.

Recent Advances in Biomedical Photonic Sensors: A Focus on Optical-Fibre-Based Sensing

In this invited review, we provide an overview of the recent advances in biomedical photonic sensors within the last five years. This review is focused on works using optical-fibre technology, employing diverse optical fibres, sensing techniques, and configurations applied in several medical fields. We identified technical innovations and advancements with increased implementations of optical-fibre sensors, multiparameter sensors, and control systems in real applications. Examples of outstanding optical-fibre sensor performances for physical and biochemical parameters are covered, including diverse sensing strategies and fibre-optical probes for integration into medical instruments such as catheters, needles, or endoscopes.

Comprehensive review of surgical microscopes: technology development and medical applications

SIGNIFICANCE

Surgical microscopes provide adjustable magnification, bright illumination, and clear visualization of the surgical field and have been increasingly used in operating rooms. State-of-the-art surgical microscopes are integrated with various imaging modalities, such as optical coherence tomography (OCT), fluorescence imaging, and augmented reality (AR) for image-guided surgery.

AIM

This comprehensive review is based on the literature of over 500 papers that cover the technology development and applications of surgical microscopy over the past century. The aim of this review is threefold: (i) providing a comprehensive technical overview of surgical microscopes, (ii) providing critical references for microscope selection and system development, and (iii) providing an overview of various medical applications.

APPROACH

More than 500 references were collected and reviewed. A timeline of important milestones during the evolution of surgical microscope is provided in this study. An in-depth technical overview of the optical system, mechanical system, illumination, visualization, and integration with advanced imaging modalities is provided. Various medical applications of surgical microscopes in neurosurgery and spine surgery, ophthalmic surgery, ear-nose-throat (ENT) surgery, endodontics, and plastic and reconstructive surgery are described.

RESULTS

Surgical microscopy has been significantly advanced in the technical aspects of high-end optics, bright and shadow-free illumination, stable and flexible mechanical design, and versatile visualization. New imaging modalities, such as hyperspectral imaging, OCT, fluorescence imaging, photoacoustic microscopy, and laser speckle contrast imaging, are being integrated with surgical microscopes. Advanced visualization and AR are being added to surgical microscopes as new features that are changing clinical practices in the operating room.

CONCLUSIONS

The combination of new imaging technologies and surgical microscopy will enable surgeons to perform challenging procedures and improve surgical outcomes. With advanced visualization and improved ergonomics, the surgical microscope has become a powerful tool in neurosurgery, spinal, ENT, ophthalmic, plastic and reconstructive surgeries.

Ex Vivo Fluorescein-Assisted Confocal Laser Endomicroscopy (CONVIVO® System) in Patients With Glioblastoma: Results From a Prospective Study

Background

Confocal laser endomicroscopy (CLE) allowing intraoperative near real-time high-resolution cellular visualization is a promising method in neurosurgery. We prospectively tested the accuracy of a new-designed miniatured CLE (CONVIVO® system) in giving an intraoperative first-diagnosis during glioblastoma removal.

Methods

Between January and May 2018, 15 patients with newly diagnosed glioblastoma underwent fluorescein-guided surgery. Two biopsies from both tumor central core and margins were harvested, dividing each sample into two specimens. Biopsies were firstly intraoperatively ex vivo analyzed by CLE, subsequently processed for frozen and permanent fixation, respectively. Then, a blind comparison was conducted between CLE and standard permanent section analyses, checking for CLE ability to provide diagnosis and categorize morphological patterns intraoperatively.

Results

Blindly comparing CONVIVO® and frozen sections images we obtained a high rate of concordance in both providing a correct diagnosis and categorizing patterns at tumor central core (80 and 93.3%, respectively) and at tumor margins (80% for both objectives). Comparing CONVIVO® and permanent sections, concordance resulted similar at central core (total/partial concordance in 80 and 86.7% for diagnosis and morphological categorization, respectively) and lower at tumor margins (66.6% for both categories). Time from fluorescein injection and time from biopsy sampling to CONVIVO® scanning was 134 ± 31 min (122–214 min) and 9.23 min (1–17min), respectively. Mean time needed for CONVIVO® images interpretation was 5.74 min (1–7 min).

Conclusions

The high rate of diagnostic/morphological consistency found between CONVIVO® and frozen section analyses suggests the possibility to use CLE as a complementary tool for intraoperative diagnosis of ex vivo tissue specimens during glioblastoma surgery.

Rapid Label-Free Analysis of Brain Tumor Biopsies by Near Infrared Raman and Fluorescence Spectroscopy-A Study of 209 Patients

In brain surgery, novel technologies are continuously developed to achieve better tumor delineation and maximize the extent of resection. Raman spectroscopy is an optical method that enables to retrieve a molecular signature of tissue biochemical composition in order to identify tumor and normal tissue. Here, the translation of Raman spectroscopy to the surgical practice for discerning a variety of different tumor entities from non-neoplastic brain parenchyma was investigated. Fresh unprocessed biopsies obtained from brain tumor surgery were analyzed over 1.5 years including all patients that gave consent. Measurements were performed with a Raman microscope by medical personnel as routine activity. The Raman and fluorescence signals of the acquired spectra were analyzed by principal component analysis, followed by supervised classification to discriminate non-tumor tissue vs. tumor and distinguish tumor entities. Histopathology of the measured biopsies was performed as reference. Classification led to the correct recognition of all non-neoplastic biopsies (7/7) and of 97% of the investigated tumor biopsies (195/202). For instance, GBM was recognized as tumor with a correct rate of 94% if primary, and of 100% if recurrent. Astrocytoma and oligodendroglioma were recognized as tumor with correct rates of 86 and 90%, respectively. All brain metastases, meningioma and schwannoma were correctly recognized as tumor and distinguished from non-neoplastic brain tissue. Furthermore, metastases were discerned from glioma with correct rate of 90%. Oligodendroglioma and astrocytoma IDH1-mutant, which differ in the presence of 1p/19q codeletion, were discerned with a correct rate of 81%. These results demonstrate the feasibility of rapid brain tumors recognition and extraction of diagnostic information by Raman spectroscopy, using a protocol that can be easily included in the routine surgical workflow.

Progress in Confocal Laser Endomicroscopy for Neurosurgery and Technical Nuances for Brain Tumor Imaging With Fluorescein

Background: Previous studies showed that confocal laser endomicroscopy (CLE) images of brain tumors acquired by a first-generation (Gen1) CLE system using fluorescein sodium (FNa) contrast yielded a diagnostic accuracy similar to frozen surgical sections and histologic analysis. We investigated performance improvements of a second-generation (Gen2) CLE system designed specifically for neurosurgical use.

Methods: Rodent glioma models were used for in vivo and rapid ex vivo CLE imaging. FNa and 5-aminolevulinic acid were used as contrast agents. Gen1 and Gen2 CLE images were compared to distinguish cytoarchitectural features of tumor mass and margin and surrounding and normal brain regions. We assessed imaging parameters (gain, laser power, brightness, scanning speed, imaging depth, and Z-stack [3D image acquisition]) and evaluated optimal values for better neurosurgical imaging performance with Gen2.

Results: Efficacy of Gen1 and Gen2 was similar in identifying normal brain tissue, vasculature, and tumor cells in masses or at margins. Gen2 had smaller field of view, but higher image resolution, and sharper, clearer images. Other advantages of the Gen2 were auto-brightness correction, user interface, image metadata handling, and image transfer. CLE imaging with FNa allowed identification of nuclear and cytoplasmic contours in tumor cells. Injection of higher dosages of FNa (20 and 40 mg/kg vs. 0.1–8 mg/kg) resulted in better image clarity and structural identification. When used with 5-aminolevulinic acid, CLE was not able to detect individual glioma cells labeled with protoporphyrin IX, but overall fluorescence intensity was higher (p < 0.01) than in the normal hemisphere. Gen2 Z-stack imaging allowed a unique 3D image volume presentation through the focal depth.

Conclusion: Compared with Gen1, advantages of Gen2 CLE included a more responsive and intuitive user interface, collection of metadata with each image, automatic Z-stack imaging, sharper images, and a sterile sheath. Shortcomings of Gen2 were a slightly slower maximal imaging speed and smaller field of view. Optimal Gen2 imaging parameters to visualize brain tumor cytoarchitecture with FNa as a fluorescent contrast were defined to aid further neurosurgical clinical in vivo and rapid ex vivo use. Further validation of the Gen2 CLE for microscopic visualization and diagnosis of brain tumors is ongoing.

Neurosurgical Flexible Probe Microscopy with Enhanced Architectural and Cytological Detail

BACKGROUND

Microscopic delineation and clearance of tumor cells at neurosurgical excision margins potentially reduce tumor recurrence and increase patient survival. Probe-based in vivo fluorescence microscopy technologies are promising for neurosurgical in vivo microscopy.

OBJECTIVE

We sought to demonstrate a flexible fiberoptic epifluorescence microscope capable of enhanced architectural and cytological imaging for in vivo microscopy during neurosurgical procedures.

METHODS

Eighteen specimens were procured from neurosurgical procedures. These specimens were stained with acridine orange and imaged with a 3-dimensional (3D)-printed epifluorescent microscope that incorporates a flexible fiberoptic probe. Still images and video sequence frames were processed using frame alignment, signal projection, and pseudo-coloring, resulting in resolution enhancement and an increased field of view.

RESULTS

Images produced displayed good nuclear contrast and architectural detail. Grade 1 meningiomas demonstrated 3D chords and whorls. Low-grade meningothelial nuclei showed streaming and displayed regularity in size, shape, and distribution. Oligodendrogliomas showed regular round nuclei and a variably staining background. Glioblastomas showed high degrees of nuclear pleomorphism and disarray. Mitoses, vascular proliferation, and necrosis were evident.

CONCLUSIONS

We demonstrate the utility of a 3D-printed, flexible probe microscope for high-resolution microscopic imaging with increased architectural detail. Enhanced in vivo imaging using this device may improve our ability to detect and decrease microscopic tumor burden at excision margins during neurosurgical procedures.

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

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.

In Vivo Real-Time Discrimination Among Glioma, Infiltration Zone, and Normal Brain Tissue via Autofluorescence Technology

BACKGROUND

Surgery is the first-line therapy for glioblastoma. There is evidence that extent of resection is significantly associated with patient survival. Unfortunately, optimal surgical resection is usually limited because of the difficulty in discriminating tumor-infiltrated region and normal brain tissue. This study aimed to develop a tool to distinguish between infiltration zone and normal tissue in real time during glioma surgery.

METHODS

In an in vivo study, C6 glioma cells were implanted into the left cerebral hemispheres of 6 rats to mimic tumorigenesis. A newly designed optical fiber-embedded needle probe was used to measure the autofluorescence of both cerebral hemispheres at various depths 5 days after the implantation. These rats were then sacrificed, and both cerebral hemispheres were removed for histopathologic analysis.

RESULTS

Comparative analyses of corresponding areas by histopathology and autofluorescence revealed highly significant (P < 0.001) differences among the normal tissue, infiltration zone, tumors, and the contralateral cerebral hemispheres. The area of the receiver operating characteristic curve was 0.978, and the sensitivity and specificity of tumor delineation were 93.9% and 94.4%, respectively.

CONCLUSIONS

The newly designed in vivo fiber-optic probe can distinguish tumor-infiltration zones from normal brain tissue in this in vivo study. Therefore, it may help neurosurgeons to increase extent of resection without damaging normal brain tissue and thus potentially improve the patients' survival and quality of life.

Probe-based three-dimensional confocal laser endomicroscopy of brain tumors: technical note

Background

Confocal laser endomicroscopy (CLE) is used during fluorescence-guided brain tumor surgery for intraoperative microscopy of tumor tissue with cellular resolution. CLE could augment and expedite intraoperative decision-making and potentially aid in diagnosis and removal of tumor tissue.

Objective

To describe an extension of CLE imaging modality that produces Z-stack images and three-dimensional (3D) pseudocolored volumetric images.

Materials and methods

Hand-held probe-based CLE was used to collect images from GL261-luc2 gliomas in C57BL/6 mice and from human brain tumor biopsies. The mice were injected with fluorescein sodium (FNa) before imaging. Patients received FNa intraoperatively, and biopsies were imaged immediately in the operating room. Some specimens were counterstained with acridine orange, acriflavine, or Hoechst and imaged on a benchtop confocal microscope. CLE images at various depths were acquired automatically, compiled, rendered into 3D volumes using Fiji software and reviewed by a neuropathologist and neurosurgeons.

Results

CLE imaging, Z-stack acquisition, and 3D image rendering were performed using 19 mouse gliomas and 31 human tumors, including meningiomas, gliomas, and pituitary adenomas. Volumetric images and Z-stacks provided additional information about fluorescence signal distribution, cytoarchitecture, and the course of abnormal vasculature.

Conclusion

3D and Z-stack CLE imaging is a unique new option for live intraoperative endomicroscopy of brain tumors. The 3D images afford an increased spatial understanding of tumor cellular architecture and visualization of related structures compared with two-dimensional images. Future application of specific fluorescent probes could benefit from this rapid in vivo imaging technology for interrogation of brain tumor tissue.

Utilization of intraoperative confocal laser endomicroscopy in brain tumor surgery

Precise identification of tumor margins is of the utmost importance in neuro-oncology. Confocal microscopy is capable of rapid imaging of fresh tissues at cellular resolution and has been miniaturized into handheld probe-based systems suitable for use in the operating room. We aimed to perform a literature review to provide an update on the current status of confocal laser endomicroscopy (CLE) technology for brain tumor surgery. Aside from benchtop confocal microscopes used in ex vivo fashion, there are four CLE systems that have been investigated for potential application in the workflow of brain tumor surgery. Preclinical studies on animal tumor models and clinical studies on human brain tumors have assessed in vivo and ex vivo imaging approaches, suggesting that confocal microscopy holds promise for rapid identification of the characteristic (diagnostic) histological features of tumor and normal brain tissues. However, there are few studies assessing diagnostic accuracy sufficient to provide a definitive determination of the clinical and economical value of CLE in brain tumor surgery. Intraoperative real-time, high-resolution tissue imaging has significant clinical potential in the field of neuro-oncology. CLE is an emerging imaging technology that shows promise for improving brain tumor surgery workflow in in vivo and ex vivo studies. Future clinical studies are necessary to demonstrate clinical and economic benefit of CLE.