Improving precision surgery: A review of current intraoperative nerve tissue fluorescence imaging

Matrix-designed bright near-infrared fluorophores for precision peripheral nerve imaging

The FDA's recent approval of pafolacianine, the first molecular targeted contrast agent for fluorescence-guided surgery (FGS), signifies a remarkable milestone in precision medicine. This advance offers new hope for cancer patients by enabling guided removal of cancerous tissues, where completed surgical removal remains a consistent challenge without real-time intraoperative guidance. For optimal surgical outcomes, delicate nerve tissues must be preserved to maintain patient quality of life. Despite advances in the clinical translation pipeline, the development of clinically viable nerve-specific contrast agents for FGS remains a significant challenge. Herein, a medicinal chemistry-based matrix design strategy was applied to effectively generate a synthetic roadmap permitting management of nerve-specificity within the near-infrared (NIR) oxazine fluorophore family. Many of these newly developed fluorophores demonstrated robust nerve-specificity and superior safety profiles, while also offering spectral profiles that are compatible with the clinical surgical FGS infrastructure. Notably, improving observed brightness in vivo enabled exceptional visibility of buried nerve tissue, a priority during surgical procedures. Critically, the lead probe showed a large dosage safety window capable of generating substantial contrast at doses 100x lower than the maximum tolerated dose. Following clinical translation, such NIR nerve-specific fluorophores stand poised to significantly improve outcomes for surgical patients by improving identification and visualization of surface and buried nerve tissues in real time within the surgical arena.

Intraoperative nerve imaging with sodium fluorescein

Nerve damage during surgery is a common and serious complication, often leading to chronic pain, functional impairments, and diminished quality of life. However, existing methods for intraoperative nerve identification remain insufficient, especially for detecting small or hidden nerve branches. Here we present a new application of a clinically approved fluorescent agent, sodium fluorescein, to enhance nerve visualization during surgery. Utilizing both clinical and customized imaging systems, fluorescein remarkably improved nerve contrast, revealing structures undetectable with white light, including small branches embedded within tissues. With its established safety profile, low cost, and immediate clinical applicability, sodium fluorescein offers the potential to revolutionize surgical practice by minimizing nerve injuries and improving patient outcomes. Clinical Trial Registration: NCT06054178 .

Graphical abstract

Intraoperative fluorescence redefining neurosurgical precision

Surgical resection is essential for treating solid tumors, with success largely dependent on the complete excision of neoplastic cells. However, neurosurgical procedures must delicately balance tumor removal with the preservation of surrounding tissue. Achieving clear margins is particularly challenging in cases like glioblastoma due to the limitations of traditional white light visualization. These limitations often result in incomplete resections, leading to frequent recurrences, or excessive resection that harms vital neural structures, causing iatrogenic nerve damage, which can lead to sensory and functional deficits. Current statistics reveal a 90% recurrence rate for malignant gliomas. Similarly, an 8% incidence of iatrogenic nerve trauma contributes to an estimated 25 million cases of peripheral nerve injury globally each year. These figures underscore the urgent need for improved intraoperative techniques for lesion margin and nerve identification and visualization. Recent advances in neurosurgical imaging, such as fluorescence-guided surgery (FGS), have begun to address these challenges. Fluorescent agents used in FGS illuminate target tissues, although not all do so selectively. Despite the promising results of agents such as 5-aminolevulinic acid and indocyanine green, their applications are mainly limited by issues of sensitivity and specificity. Furthermore, these agents do not effectively address the need for precise nerve visualization. Nerve Peptide 41, a novel systemically administered fluorescent nerve-targeted probe, shows promise in filling this gap. This review assesses the major fluorescent imaging modalities in neurosurgery, highlighting each of their benefits, limitations, and potential.

How to objectively evaluate the impact of image-guided surgery technologies

PURPOSE

This manuscript aims to provide a better understanding of methods and techniques with which one can better quantify the impact of image-guided surgical technologies.

METHODS

A literature review was conducted with regard to economic and technical methods of medical device evaluation in various countries. Attention was focused on applications related to image-guided interventions that have enabled procedures to be performed in a minimally invasive manner, produced superior clinical outcomes, or have become standard of care.

RESULTS

The review provides examples of successful implementations and adoption of image-guided surgical techniques, mostly in the field of neurosurgery. Failures as well as newly developed technologies still undergoing cost-efficacy analysis are discussed.

CONCLUSION

The field of image-guided surgery has evolved from solely using preoperative images to utilizing highly specific tools and software to provide more information to the interventionalist in real time. While deformations in soft tissue often preclude the use of such instruments outside of neurosurgery, recent developments in optical and radioactive guidance have enabled surgeons to better account for organ motion and provide feedback to the surgeon as tissue is cut. These technologies are currently undergoing value assessments in many countries and hold promise to improve outcomes for patients, surgeons, care teams, payors, and society in general.

Fluorescence in neurosurgery: its therapeutic and diagnostic significance - a comprehensive review

This review provides a comprehensive overview of the therapeutic and diagnostic implications of fluorescence imaging in neurosurgery. Fluorescence imaging has become a valuable intraoperative visualization and guidance tool, facilitating precise surgical interventions. The therapeutic role of fluorescence is examined, including its application in photodynamic therapy and tumor-targeted therapy. It also explores its diagnostic capabilities in tumor detection, margin assessment, and blood-brain barrier evaluation. Drawing from clinical and preclinical studies, the review underscores the growing evidence supporting the efficacy of fluorescence imaging in neurosurgical practice. Furthermore, it discusses current limitations and future directions, emphasizing the potential for emerging technologies to enhance the utility and accessibility of fluorescence imaging, ultimately improving patient outcomes in neurosurgery.

Making the Brightest Ones Dim: Maximizing the Photothermal Conversion Efficiency of BODIPY-Based Photothermal Agents

The successful implementation of photothermal therapy (PTT) in cancer treatment hinges on the development of highly effective photothermal agents (PTAs). Boron dipyrromethene (BODIPY) dyes, being well known for their high brightness and quantum efficiencies, are the antithesis of PTAs. Nonetheless, a systematic exploration of the photophysics and photothermal characteristics of a series of π-extended BODIPY dyes with high absorptivity in the near-infrared (NIR) region has achieved superior photothermal conversion efficiencies (>90%), in both monomeric state and nanoparticles after encapsulation in a biocompatible polyethyleneglycol 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy-(polyethylene glycol)-2000]. Optimal PTA candidates combine strong NIR absorption provided by extended donor-acceptor conjugation and an optimization of the electronic and steric effects of meso-substituents to maximize photothermal conversion performance. The PTT-optimized meso-CF3-BODIPY, TCF3PEn exhibits exceptional efficacy in inducing cancer cell apoptosis and in vivo tumor ablation using low-power NIR laser irradiation (0.3 W cm-2, 808 nm) as well as excellent biological safety, underscoring its potential for advancing light-induced cancer therapies.

NIR-II light in clinical oncology: opportunities and challenges

Novel strategies utilizing light in the second near-infrared region (NIR-II; 900-1,880 nm wavelengths) offer the potential to visualize and treat solid tumours with enhanced precision. Over the past few decades, numerous techniques leveraging NIR-II light have been developed with the aim of precisely eliminating tumours while maximally preserving organ function. During cancer surgery, NIR-II optical imaging enables the visualization of clinically occult lesions and surrounding vital structures with increased sensitivity and resolution, thereby enhancing surgical quality and improving patient prognosis. Furthermore, the use of NIR-II light promises to improve cancer phototherapy by enabling the selective delivery of increased therapeutic energy to tissues at greater depths. Initial clinical studies of NIR-II-based imaging and phototherapy have indicated impressive potential to decrease cancer recurrence, reduce complications and prolong survival. Despite the encouraging results achieved, clinical translation of innovative NIR-II techniques remains challenging and inefficient; multidisciplinary cooperation is necessary to bridge the gap between preclinical research and clinical practice, and thus accelerate the translation of technical advances into clinical benefits. In this Review, we summarize the available clinical data on NIR-II-based imaging and phototherapy, demonstrating the feasibility and utility of integrating these technologies into the treatment of cancer. We also introduce emerging NIR-II-based approaches with substantial potential to further enhance patient outcomes, while also highlighting the challenges associated with imminent clinical studies of these modalities.

Neurosurgical Intervention for Nerve and Muscle Biopsies

(1) Background: Neurologic and musculoskeletal diseases represent a considerable portion of the underlying etiologies responsible for the widely prevalent symptoms of pain, weakness, numbness, and paresthesia. Because of the subjective and often nonspecific nature of these symptoms, different diagnostic modalities have been explored and utilized. (2) Methods: Literature review. (3) Results: Nerve and muscle biopsy remains the gold standard for diagnosing many of the responsible neurological and musculoskeletal conditions. However, the need for invasive tissue sampling is diminishing as more investigations explore alternative diagnostic modalities. Because of this, it is important to explore the current role of neurosurgical intervention for nerve and muscle biopsies and its current relevance in the diagnostic landscape of neurological and musculoskeletal disorders. With consideration of the role of nerve and muscle biopsy, it is also important to explore innovations and emerging techniques for conducting these procedures. This review explores the indications and emerging techniques for neurological intervention for nerve and muscle biopsies. (4) Conclusions: The role of neurosurgical intervention for nerve and muscle biopsy remains relevant in diagnosing many neurological and musculoskeletal disorders. Biopsy is especially relevant as a supportive point of evidence for diagnosis in atypical cases. Additionally, emerging techniques have been explored to guide diagnostics and biopsy, conduct less invasive biopsies, and reduce risks of worsening neurologic function and other symptoms secondary to biopsy.

Nerve Visualization using Phenoxazine-Based Near-Infrared Fluorophores to Guide Prostatectomy

Fluorescence-guided surgery (FGS) is poised to revolutionize surgical medicine through near-infrared (NIR) fluorophores for tissue- and disease-specific contrast. Clinical open and laparoscopic FGS vision systems operate nearly exclusively at NIR wavelengths. However, tissue-specific NIR contrast agents compatible with clinically available imaging systems are lacking, leaving nerve tissue identification during prostatectomy a persistent challenge. Here, it is shown that combining drug-like molecular design concepts and fluorophore chemistry enabled the production of a library of NIR phenoxazine-based fluorophores for intraoperative nerve-specific imaging. The lead candidate readily delineated prostatic nerves in the canine and iliac plexus in the swine using the clinical da Vinci Surgical System that has been popularized for minimally invasive prostatectomy procedures. These results demonstrate the feasibility of molecular engineering of NIR nerve-binding fluorophores for ready integration into the existing surgical workflow, paving the path for clinical translation to reduce morbidity from nerve injury for prostate cancer patients.

A Raman topography imaging method toward assisting surgical tumor resection

Achieving complete tumor resection upon initial surgical intervention can lead to better patient outcomes by making adjuvant treatments more efficacious and reducing the strain of repeat surgeries. Complete tumor resection can be difficult to confirm intraoperatively. Methods like touch preparation (TP) have been inconsistent for detecting residual malignant cell populations, and fatty specimens like breast cancer lumpectomies are too fatty to process for rapid histology. We propose a novel workflow of immunostaining and topographic surface imaging of freshly excised tissue to ensure complete resection using highly sensitive and spectrally separable surface-enhanced Raman scattering nanoparticles (SERS NPs) as the targeted contrast agent. Biomarker-targeting SERS NPs are ideal contrast agents for this application because their sensitivity enables rapid detection, and their narrow bands enable extensive intra-pixel multiplexing. The adaptive focus capabilities of an advanced Raman instrument, combined with our rotational accessory device for exposing each surface of the stained specimen to the objective lens, enable topographic mapping of complete excised specimen surfaces. A USB-controlled accessory for a Raman microscope was designed and fabricated to enable programmatic and precise angular manipulation of specimens in concert with instrument stage motions during whole-surface imaging. Specimens are affixed to the accessory on an anti-slip, sterilizable rod, and the tissue surface exposed to the instrument is adjusted on demand using a programmed rotating stepper motor. We demonstrate this topographic imaging strategy on a variety of phantoms and preclinical tissue specimens. The results show detail and texture in specimen surface topography, orientation of findings and navigability across surfaces, and extensive SERS NP multiplexing and linear quantitation capabilities under this new Raman topography imaging method. We demonstrate successful surface mapping and recognition of all 26 of our distinct SERS NP types along with effective deconvolution and localization of randomly assigned NP mixtures. Increasing NP concentrations were also quantitatively assessed and showed a linear correlation with Raman signal with an R2 coefficient of determination of 0.97. Detailed surface renderings color-encoded by unmixed SERS NP abundances show a path forward for content-rich, interactive surgical margin assessment.