Fluorescence image-guided neurosurgery

Combination of Tractography, Intraoperative Computed Tomography and 5-Aminolevulinic Acid Fluorescence in Stereotactic Brain Biopsies: A Case Series

Stereotactic needle biopsy (SNB) may be performed to collect tissue samples from lesions not amenable to open surgery. Integration of tractography, intraoperative imaging and fluorescence has been applied to reduce risk of complications and confirm the adequacy of bioptic specimens. Clinical and radiological data from patients who underwent stereotactic needle biopsy with the use of intraoperative CT, tractography and 5-aminolevulinic acid (5-ALA) fluorescence in a single Hospital were retrospectively reviewed to evaluate the accuracy and safety of the procedure. Seven patients were included in the study, and all the collected specimens showed red fluorescence. In six of them, the final histopathological diagnosis was grade 4 glioblastoma IDH-wt and in the other case it was Diffuse large B-Cell Lymphoma. The integration of tractography, intraoperative CT and 5-ALA as an intraoperative marker of diagnostic samples may be suggested in biopsies of suspect gliomas and lymphomas. The cost-effectiveness of the procedure should be evaluated in future studies.

5-Aminolevulinic Acid Fluorescence-Guided Surgery in Head and Neck Squamous Cell Carcinoma

OBJECTIVES

To determine the utility of 5-aminolevulinic acid (5-ALA) fluorescence for resection of head and neck carcinoma.

METHODS

In this prospective pilot trial, 5-ALA was administered as an oral suspension 3-5 h prior to induction of anesthesia for resection of head and neck squamous cell carcinoma (HNSCC). Following resection, 405 nm blue light was applied, and fluorescence of the tumor as well as the surgical bed was recorded. Specimen fluorescence intensity was graded categorically as none (score = 0), mild (1), moderate (2), or robust (3) by the operating surgeon intraoperatively and corroborated with final pathologic diagnosis.

RESULTS

Seven patients underwent resection with 5-ALA. Five (83%) were male with an age range of 33-82 years (mean = 60). Sites included nasal cavity (n = 3), oral cavity (n = 3), and the larynx (n = 1). All specimens demonstrated robust fluorescence when 5-ALA was administered 3-5 h preoperatively. 5-ALA fluorescence predicted the presence of perineural invasion, a positive margin, and metastatic lymphadenopathy. Two patients had acute photosensitivity reactions, and one patient had a temporary elevation of hepatic enzymes.

CONCLUSIONS

5-ALA induces robust intraoperative fluorescence of HNSCC, capable of demonstrating a positive margin, perineural invasion, and metastatic nodal disease. Although no conclusions are there about the safety of this drug in the head and neck cancer population, our study parallels the extensive safety data in the neurosurgical literature. Future applications may include intraoperative assessment of margin status, diagnostic accuracy, and impacts on survival.

LEVEL OF EVIDENCE

4 Laryngoscope, 134:741-748, 2024.

Fluorescein-guided surgery for high-grade glioma resection: a five-year-long retrospective study at our institute

Objective

This study investigates the extent of resection, duration of surgery, intraoperative blood loss, and postoperative complications in patients with high-grade glioma who received surgery with or without sodium fluorescein guidance.

Methods

A single-center retrospective cohort study was conducted on 112 patients who visited our department and underwent surgery between July 2017 and June 2022, with 61 in the fluorescein group and 51 in the non-fluorescein group. Baseline characteristics, intraoperative blood loss, surgery duration, resection extent, and postoperative complications were documented.

Results

The duration of surgery was significantly shorter in the fluorescein group than in the non-fluorescein group (P = 0.022), especially in patients with tumors in the occipital lobes (P = 0.013). More critically, the gross total resection (GTR) rate was significantly higher in the fluorescein group than in the non-fluorescein group (45.9% vs. 19.6%, P = 0.003). The postoperative residual tumor volume (PRTV) was also significantly lower in the fluorescein group than in the non-fluorescein group (0.40 [0.12-7.11] cm³ vs. 4.76 [0.44-11.00] cm³, P = 0.020). Particularly in patients with tumors located in the temporal and occipital lobes (temporal, GTR 47.1% vs. 8.3%, P = 0.026; PRTV 0.23 [0.12-8.97] cm³ vs. 8.35 [4.05-20.59] cm³, P = 0.027; occipital, GTR 75.0% vs. 0.0%, P = 0.005; PRTV 0.15 [0.13-1.50] cm³ vs. 6.58 [3.70-18.79] cm³, P = 0.005). However, the two groups had no significant difference in intraoperative blood loss (P = 0.407) or postoperative complications (P = 0.481).

Conclusions

Fluorescein-guided resection of high-grade gliomas using a special operating microscope is a feasible, safe, and convenient technique that significantly improves GTR rates and reduces postoperative residual tumor volume when compared to conventional white light surgery without fluorescein guidance. This technique is particularly advantageous for patients with tumors located in non-verbal, sensory, motor, and cognitive areas such as the temporal and occipital lobes, and does not increase the incidence of postoperative complications.

The usefulness of intraoperative sodium fluorescein in the surgical treatment of relapsed high-grade brain tumors in pediatric patients

PURPOSE

We report the usefulness of intraoperative sodium fluorescein (SF) in the surgical treatment of relapsed high-grade brain tumors in pediatric neurosurgery.

METHODS

We describe our protocol for intraoperative SF and three cases of patients between 5 and 11 years diagnosed and surgically treated for relapsed high-grade brain tumors using SF.

RESULTS

The 560-nm microscope filter enables the use of low doses of this fluorochrome. A dose of 3 mg/kg of patient weight of 10% SF, administered intravenously, is safe and effective in children. The effect of SF was immediate, providing a clear margin between the tumor and healthy tissue, which enabled good tumor resection. We observed no adverse effects in the postoperative period, and the patients evolved satisfactorily.

CONCLUSIONS

To the best of our knowledge, we describe for the first time the use of fluorescein in reoperations of relapsed high-grade brain tumors in childhood with promising results. Using SF in children is a safe, affordable, and effective technique that offers an excellent intraoperative image, being a feasible option to improve oncological resection. This study is one of the few that uses SF in pediatric neurosurgery, where it could be very beneficial.

Effect of 5-Aminolevulinic Acid and Sodium Fluorescein on the Extent of Resection in High-Grade Gliomas and Brain Metastasis

Surgery is essential in the treatment of high-grade gliomas (HGG) and gross total resection (GTR) is known to increase the overall survival and progression-free survival. Several studies have shown that fluorescence-guided surgery with 5-aminolevulinic acid (5-ALA) increases GTR considerably compared to white light surgery (65% vs. 36%). In recent years, sodium fluorescein (SF) has become an increasingly popular agent for fluorescence-guided surgery due to numerous utility benefits compared to 5-ALA, including lower cost, non-toxicity, easy administration during surgery and a wide indication range covering all contrast-enhancing lesions with disruption of the blood-brain barrier in the CNS. However, currently, SF is an off-label agent and the level of evidence for use in HGG surgery is inferior compared to 5-ALA. Here, we give an update and review the latest literature on fluorescence-guided surgery with 5-ALA and SF for brain tumors with emphasis on fluorescence-guided surgery in HGG and brain metastases. Further, we assess the advantages and disadvantages of both fluorophores and discuss their future perspectives.

State-of-the-art imaging for glioma surgery

Diffuse gliomas are infiltrative primary brain tumors with a poor prognosis despite multimodal treatment. Maximum safe resection is recommended whenever feasible. The extent of resection (EOR) is positively correlated with survival. Identification of glioma tissue during surgery is difficult due to its diffuse nature. Therefore, glioma resection is imaging-guided, making the choice for imaging technique an important aspect of glioma surgery. The current standard for resection guidance in non-enhancing gliomas is T2 weighted or T2w-fluid attenuation inversion recovery magnetic resonance imaging (MRI), and in enhancing gliomas T1-weighted MRI with a gadolinium-based contrast agent. Other MRI sequences, like magnetic resonance spectroscopy, imaging modalities, such as positron emission tomography, as well as intraoperative imaging techniques, including the use of fluorescence, are also available for the guidance of glioma resection. The neurosurgeon’s goal is to find the balance between maximizing the EOR and preserving brain functions since surgery-induced neurological deficits result in lower quality of life and shortened survival. This requires localization of important brain functions and white matter tracts to aid the pre-operative planning and surgical decision-making. Visualization of brain functions and white matter tracts is possible with functional MRI, diffusion tensor imaging, magnetoencephalography, and navigated transcranial magnetic stimulation. In this review, we discuss the current available imaging techniques for the guidance of glioma resection and the localization of brain functions and white matter tracts.

Combined-therapeutic strategies synergistically potentiate glioblastoma multiforme treatment via nanotechnology

Glioblastoma multiforme (GBM) is a highly aggressive and devastating brain tumor characterized by poor prognosis and high rates of recurrence. Numerous therapeutic strategies and delivery systems are developed to prolong the survival time. They exhibit enhanced therapeutic effects in animal models, whereas few of them is applied in clinical trials. Taking into account the drug-resistance and high recurrence of GBM, combined-therapeutic strategies are exploited to maximize therapeutic efficacy. The combined therapies demonstrate superior results than those of single therapies against GBM. The co-therapeutic agents, the timing of therapeutic strategies and the delivery systems greatly affect the overall outcomes. Herein, the current advances in combined therapies for glioblastoma via systemic administration are exhibited in this review. And we will discuss the pros and cons of these combined-therapeutic strategies via nanotechnology, and provide the guidance for developing rational delivery systems to optimize treatments against GBM and other malignancies in central nervous system.

Comparison of 5-aminolevulinic acid and sodium fluorescein for intraoperative tumor visualization in patients with high-grade gliomas: a single-center retrospective study

OBJECTIVE

Maximal safe resection is an important surgical goal in the treatment for high-grade gliomas. Fluorescent dyes help the surgeon to distinguish malignant tissue from healthy. The aims of this study were 1) to compare the 2 fluorescent dyes 5-aminolevulinic acid (5-ALA) and sodium fluorescein (fluorescein) regarding extent of resection, progression-free survival, and overall survival; and 2) to assess the influence of other risk factors on clinical outcome and screen for potential disadvantages of the dyes.

METHODS

A total of 209 patients with high-grade gliomas were included in this retrospective study. Resections were performed in the period from 2012 to 2017 using 5-ALA or fluorescein. Extent of resection was assessed as the difference in tumor volume between early postoperative and preoperative MRI studies. Tumor progression-free survival and overall survival were analyzed using an adjusted Cox proportional hazards model.

RESULTS

One hundred fifty-eight patients were operated on with 5-ALA and 51 with fluorescein. The median duration of follow-up was 46.7 and 21.2 months, respectively. Covariables were evenly distributed. There was no statistically significant difference in volumetrically assessed median extent of resection (96.9% for 5-ALA vs 97.4% for fluorescein, p = 0.46) or the percentage of patients with residual tumor volume less than 0.175 cm3 (29.5% for 5-ALA vs 36.2% for fluorescein, p = 0.39). The median overall survival was 14.8 months for the 5-ALA group and 19.7 months for the fluorescein group (p = 0.06). The median adjusted progression-free survival was 8.7 months for the 5-ALA group and 9.2 months for the fluorescein group (p = 0.03).

CONCLUSIONS

Fluorescein can be used as a viable alternative to 5-ALA for intraoperative fluorescent guidance in brain tumor surgery. Comparative, prospective, and randomized studies are much needed.

Development of a Simulation Model for Fluorescence-Guided Brain Tumor Surgery

Objective: Fluorescence dyes are increasingly used in brain tumor surgeries, and thus the development of simulation models is important for teaching neurosurgery trainees how to perform fluorescence-guided operations. We aimed to create a tumor model for fluorescence-guided surgery in high-grade glioma (HGG).

Methods: The tumor model was generated by the following steps: creating a tumor gel with a similar consistency to HGG, selecting fluorophores at optimal concentrations with realistic color, mixing the fluorophores with tumor gel, injecting the gel into fresh pig/sheep brain, and testing resection of the tumor model under a fluorescence microscope. The optimal tumor gel was selected among different combinations of agar and gelatin. The fluorophores included fluorescein, indocyanine green (ICG), europium, chlorin e6 (Ce6), and protoporphyrin IX (PpIX). The tumor model was tested by neurosurgeons and neurosurgery trainees, and a survey was used to assess the validity of the model. In addition, the photobleaching phenomenon was studied to evaluate its influence on fluorescence detection.

Results: The best tumor gel formula in terms of consistency and tactile response was created using 100 mL water at 100°C, 0.5 g of agar, and 3 g of gelatin mixed thoroughly for 3 min. An additional 1 g of agar was added when the tumor gel cooled to 50°C. The optimal fluorophore concentration ranges were fluorescein 1.9 × 10⁻⁴ to 3.8 × 10⁻⁴ mg/mL, ICG 4.9 × 10⁻³ to 9.8 × 10⁻³ mg/mL, europium 7.0 × 10⁻² to 1.4 × 10⁻¹ mg/mL, Ce6 2.2 × 10⁻³ to 4.4 × 10⁻³ mg/mL, and PpIX 1.8 × 10⁻² to 3.5 × 10⁻² mg/mL. No statistical differences among fluorophores were found for face validity, content validity, and fluorophore preference. Europium, ICG, and fluorescein were shown to be relatively stable during photobleaching experiments, while chlorin e6 and PpIX had lower stability.

Conclusions: The model can efficiently highlight the “tumor” with 3 different colors—green, yellow, or infrared green with color overlay. These models showed high face and content validity, although there was no significant difference among the models regarding the degree of simulation and training effectiveness. They are useful educational tools for teaching the key concepts of intra-axial tumor resection techniques, such as subpial dissection and nuances of fluorescence-guided surgery.

Ex-vivo analysis of quantitative 5-ALA fluorescence intensity in diffusely infiltrating gliomas using a handheld spectroscopic probe: Correlation with histopathology, proliferation and microvascular density

BACKGROUND

Intraoperative semiquantitative classification of different visible 5-aminolevulinic acid (5-ALA) fluorescence levels by the neurosurgeon is subjective. Recently, handheld spectroscopic probes were introduced enabling quantitative analysis of 5-ALA induced fluorescence intensity (FI). The aim of this ex-vivo study was to correlate the FI in gliomas of different grades with histopathology, proliferation and microvasular density (MVD).

PATIENTS AND METHODS

Patients with suspected World Health Organization (WHO) grade II-IV gliomas were included and tissue samples from different visible fluorescence levels (strong, vague or none) were intraoperatively collected. After resection, the FI of each sample was investigated ex-vivo by a handheld spectroscopic probe. The FI values were correlated with visible fluorescence, histopathology (WHO grade, quality of tissue, histopathological parameters of anaplasia), proliferation (MIB-1) and MVD.

RESULTS

Altogether, 143 tumor samples with strong (n = 61), vague (n = 21) and no fluorescence (n = 61) were collected in 68 patients. We found significantly different median FI values between all three visible fluorescence levels. Moreover, the median FI value was significantly higher in WHO grade III/IV samples and compact tumor tissue compared to WHO grade II samples and infiltrated tumor tissue. Further, significant differences in median FI values were observed in specific histopathological parameters of anaplasia (mitotic rate, cell density, nuclear pleomorphism and microvascular proliferation) in multivariable analysis. Finally, a significant correlation between the proliferation rate and FI, but not between MVD and FI was noted.

CONCLUSION

Our data indicate that handheld spectroscopic probes are capable of visualizing intratumoral glioma heterogeneity by objective assessment of fluorescence and may thus optimize future glioma surgery.