Design and synthesis of large Stokes shift DNA dyes with reduced genotoxicity

Despite intensive search over the past decades, only a few small-molecule DNA fluorescent dyes were found with large Stokes shifts. These molecules, however, are often too toxic for widespread usage. Here, we designed DNA-specific fluorescent dyes rooted in benzimidazole architectures with a hitherto unexplored molecular framework based on thiazole-benzimidazole scaffolding. We further incorporated a pyrazole ring with an extended sidechain to prevent cell penetration. These novel benzimidazole derivatives were predicted by quantum calculations and subsequently validated to have large Stokes shifts ranging from 135 to 143 nm, with their emission colors changed from capri blue for the Hoechst reference compound to iguana green. These readily-synthesized compounds, which displayed improved DNA staining intensity and detection limits along with a complete loss of capability for cellular membrane permeation and negligible mutagenic effects as designed, offer a safer alternative to the existing high-performance small-molecule DNA fluorescent dyes.

First-in-man study of the PSMA Minibody IR800-IAB2M for molecularly targeted intraoperative fluorescence guidance during radical prostatectomy

PURPOSE

Prostate-specific membrane antigen (PSMA) is increasingly used to image prostate cancer in clinical practice. We sought to develop and test a humanised PSMA minibody IAB2M conjugated to the fluorophore IRDye 800CW-NHS ester in men undergoing robot-assisted laparoscopic radical prostatectomy (RARP) to image prostate cancer cells during surgery.

METHODS

The minibody was evaluated pre-clinically using PSMA positive/negative xenograft models, following which 23 men undergoing RARP between 2018 and 2020 received between 2.5 mg and 20 mg of IR800-IAB2M intravenously, at intervals between 24 h and 17 days prior to surgery. At every step of the procedure, the prostate, pelvic lymph node chains and extra-prostatic surrounding tissue were imaged with a dual Near-infrared (NIR) and white light optical platform for fluorescence in vivo and ex vivo. Histopathological evaluation of intraoperative and postoperative microscopic fluorescence imaging was undertaken for verification.

RESULTS

Twenty-three patients were evaluated to optimise both the dose of the reagent and the interval between injection and surgery and secure the best possible specificity of fluorescence images. Six cases are presented in detail as exemplars. Overall sensitivity and specificity in detecting non-lymph-node extra-prostatic cancer tissue were 100% and 65%, and 64% and 64% respectively for lymph node positivity. There were no side-effects associated with administration of the reagent.

CONCLUSION

Intraoperative imaging of prostate cancer tissue is feasible and safe using IR800-IAB2M. Further evaluation is underway to assess the benefit of using the technique in improving completion of surgical excision during RARP.

REGISTRATION

ISCRCTN10046036: https://www.isrctn.com/ISRCTN10046036 .

Anion-π+ AIEgens for Fluorescence Imaging and Photodynamic Therapy

Fluorescence imaging-guided photodynamic therapy (PDT) has attracted extensive attention due to its potential of real-time monitoring the lesion locations and visualizing the treatment process with high sensitivity and resolution. Aggregation-induced emission luminogens (AIEgens) show enhanced fluorescence and reactive oxygen species (ROS) generation after cellular uptake, giving them significant advantages in bioimaging and PDT applications. However, most AIEgens are unfavorable for the application in organisms due to their severe hydrophobicity. Anion-π+ type AIEgens carry intrinsic charges that can effectively alleviate their hydrophobicity and improve their binding capability to cells, which is expected to enhance the bioimaging quality and PDT performance. This concept summarizes the applications of anion-π+ type AIEgens in fluorescence imaging, fluorescence imaging-guided photodynamic anticancer and antimicrobial therapy in recent years, hoping to provide some new ideas for the construction of robust photosensitizers. Finally, the current problems and future challenges of anion-π+ AIEgens are discussed.

Fluorescence-guided surgery using cetuximab-800CW in patients with penile carcinoma

OBJECTIVE

To investigate the feasibility of fluorescence molecular imaging (FMI), using cetuximab-800CW, as an intraoperative tool to determine surgical margins in penile squamous cell carcinoma (PSCC).

PATIENTS AND METHODS

A total of 11 patients with PSCC received 75 mg cetuximab followed by 15 mg cetuximab-800CW 2 days before surgery. FMI of the whole excision specimen and tissue slices was performed. Fluorescence visualisation was correlated to histopathology. Based on tumour and healthy tissue regions of interest, mean fluorescence intensity was calculated for each individual patient.

RESULTS

Significant differences between tumour and healthy mean fluorescence intensity were found with tumour-to-background ratios of a median (IQR) of 1.51 (0.99) and a mean (SD) of 1.51 (0.32) in the excision specimen and tissue slices, respectively. One patient showed a high relative fluorescence intensity with a signal-to-background ratio of 1.79, corresponding to a tumour-positive margin on fresh frozen sectioning.

CONCLUSION

In this Phase I study we showed that cetuximab-800CW seems suitable to discriminate PSCC from background tissue. The tracer was well tolerated, and no false positive spots were seen.

Assessment of open-field fluorescence guided surgery systems: implementing a standardized method for characterization and comparison

Significance

Fluorescence guided surgery (FGS) has demonstrated improvements in decision making and patient outcomes for a wide range of surgical procedures. Not only can FGS systems provide a higher level of structural perfusion accuracy in tissue reconstruction cases but they can also serve for real-time functional characterization. Multiple FGS devices have been Food and Drug administration (FDA) cleared for use in open and laparoscopic surgery. Despite the rapid growth of the field, there has been a lack standardization methods.

Aim

This work overviews commonalities inherent to optical imaging methods that can be exploited to produce such a standardization procedure. Furthermore, a system evaluation pipeline is proposed and executed through the use of photo-stable indocyanine green fluorescence phantoms. Five different FDA-approved open-field FGS systems are used and evaluated with the proposed method.

Approach

The proposed pipeline encompasses the following characterization: (1) imaging spatial resolution and sharpness, (2) sensitivity and linearity, (3) imaging depth into tissue, (4) imaging system DOF, (5) uniformity of illumination, (6) spatial distortion, (7) signal to background ratio, (8) excitation bands, and (9) illumination wavelength and power.

Results

The results highlight how such a standardization approach can be successfully implemented for inter-system comparisons as well as how to better understand essential features within each FGS setup.

Conclusions

Despite clinical use being the end goal, a robust yet simple standardization pipeline before clinical trials, such as the one presented herein, should benefit regulatory agencies, manufacturers, and end-users to better assess basic performance and improvements to be made in next generation FGS systems.

Fluorescent nano- and microparticles for sensing cellular microenvironment: past, present and future applications

The tumor microenvironment (TME) demonstrates distinct hallmarks, including acidosis, hypoxia, reactive oxygen species (ROS) generation, and altered ion fluxes, which are crucial targets for early cancer biomarker detection, tumor diagnosis, and therapeutic strategies. Various imaging and sensing techniques have been developed and employed in both research and clinical settings to visualize and monitor cellular and TME dynamics. Among these, ratiometric fluorescence-based sensors have emerged as powerful analytical tools, providing precise and sensitive insights into TME and enabling real-time detection and tracking of dynamic changes. In this comprehensive review, we discuss the latest advancements in ratiometric fluorescent probes designed for the optical mapping of pH, oxygen, ROS, ions, and biomarkers within the TME. We elucidate their structural designs and sensing mechanisms as well as their applications in in vitro and in vivo detection. Furthermore, we explore integrated sensing platforms that reveal the spatiotemporal behavior of complex tumor cultures, highlighting the potential of high-resolution imaging techniques combined with computational methods. This review aims to provide a solid foundation for understanding the current state of the art and the future potential of fluorescent nano- and microparticles in the field of cellular microenvironment sensing.

Short-wave infrared fluorescence imaging of near-infrared dyes with robust end-tail emission using a small-animal imaging device

Commercially available near-infrared (NIR) dyes, including indocyanine green (ICG), display an end-tail of the fluorescence emission spectrum detectable in the short-wave infrared (SWIR) window. Imaging methods based on the second NIR spectral region (1,000-1,700 nm) are gaining interest within the biomedical imaging community due to minimal autofluorescence and scattering, allowing higher spatial resolution and depth sensitivity. Using a SWIR fluorescence imaging device, the properties of ICG vs. heptamethine cyanine dyes with emission >800 nm were evaluated using tissue-simulating phantoms and animal experiments. In this study, we tested the hypothesis that an increased rigidity of the heptamethine chain may increase the SWIR imaging performance due to the bathochromic shift of the emission spectrum. Fluorescence SWIR imaging of capillary plastic tubes filled with dyes was followed by experiments on healthy animals in which a time series of fluorescence hindlimb images were analyzed. Our findings suggest that higher spatial resolution can be achieved even at greater depths (>5 mm) or longer wavelengths (>1,100 nm), in both tissue phantoms and animals, opening the possibility to translate the SWIR prototype toward clinical application.

A Blood-Responsive AIE Bioprobe for the Ultrasensitive Detection and Assessment of Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is a severe subtype of stroke caused by the rupturing of blood vessels in the brain. The ability to accurately assess the degree of bleeding in an SAH model is crucial for understanding the brain-damage mechanisms and developing therapeutic strategies. However, current methods are unable to monitor microbleeding owing to their limited sensitivities. Herein, a new bleeding assessment system using a bioprobe TTVP with aggregation-induced emission (AIE) characteristics is demonstrated. TTVP is a water-soluble, small-molecule probe that specifically interacts with blood. Taking advantage of its AIE characteristics, cell membranes affinity, and albumin-targeting ability, TTVP fluoresces in bleeding areas and detects the presence of blood with a high signal-to-noise (S/N) ratio. The degree of SAH bleeding in an endovascular perforation model is clearly evaluated based on the intensity of the fluorescence observed in the brain, which enables the ultrasensitive detection of mirco-bleeding in the SAH model in a manner that outperforms the current imaging strategies. This method serves as a promising tool for the sensitive analysis of the degree of bleeding in SAHs and other hemorrhagic diseases.

Image restoration for blurry optical images caused by photon diffusion with deep learning

Optical macroscopic imaging techniques have shown great significance in the investigations of biomedical issues by revealing structural or functional information of living bodies through the detection of visible or near-infrared light derived from different mechanisms. However, optical macroscopic imaging techniques suffer from poor spatial resolution due to photon diffusion in biological tissues. This dramatically restricts the application of optical imaging techniques in numerous situations. In this paper, an image restoration method based on deep learning is proposed to eliminate the blur caused by photon diffusion in optical macroscopic imaging. Two blurry images captured at orthogonal angles are used as the additional information to ensure the uniqueness of the solution and restore the small targets at deep locations. Then a fully convolutional neural network is proposed to accomplish the image restoration, which consists of three sectors: V-shaped network for central view, V-shaped network for side views, and synthetical path. The two V-shaped networks are concatenated to the synthetical path with skip connections to generate the output image. Simulations as well as phantom and mouse experiments are implemented. Results indicate the effectiveness of the proposed method.

Poly(Styrene-Co-Maleic Acid)-Conjugated 6-Aminofluorescein and Rhodamine Micelle as Macromolecular Fluorescent Probes for Micro-Tumors Detection and Imaging

Styrene-co-maleic acid (SMA) copolymer was evaluated as a polymer platform to conjugate with two fluorescent dyes, i.e., 6-aminofluorescein (AF) and Rhodamine (Rho); which spontaneously self-assembles in an aqueous medium and forms a micelle through a non-covalent interaction. These SMA-dye conjugates showed the nanosized micelle formation through dynamic light scattering (DLS) with discrete distributions having mean particle sizes of 135.3 nm, and 190.9 nm for SMA-AF, and SMA-Rho, respectively. The apparent molecular weight of the micelle was evaluated using Sephadex G-100 gel chromatography and it was found that the 49.3 kDa, and 28.7 kDa for SMA-AF, and SMA-Rho, respectively. Moreover, the biodistribution study showed the selective accumulation of the SMA-dye conjugates in the tumor of mice. Taken together, the SMA-dye conjugated micelles appear in high concentrations in the tumor by utilizing the enhanced permeability and retention (EPR) effect of the tumor-targeted delivery. These results indicate that SMA-dye conjugates have the advanced potential as macromolecular fluorescent probes for microtumor imaging by means of a photodynamic diagnosis.

Decoupling channel count from field of view and spatial resolution in single-sensor imaging systems for fluorescence image-guided surgery

SIGNIFICANCE

Near-infrared fluorescence image-guided surgery is often thought of as a spectral imaging problem where the channel count is the critical parameter, but it should also be thought of as a multiscale imaging problem where the field of view and spatial resolution are similarly important.

AIM

Conventional imaging systems based on division-of-focal-plane architectures suffer from a strict relationship between the channel count on one hand and the field of view and spatial resolution on the other, but bioinspired imaging systems that combine stacked photodiode image sensors and long-pass/short-pass filter arrays offer a weaker tradeoff.

APPROACH

In this paper, we explore how the relevant changes to the image sensor and associated image processing routines affect image fidelity during image-guided surgeries for tumor removal in an animal model of breast cancer and nodal mapping in women with breast cancer.

RESULTS

We demonstrate that a transition from a conventional imaging system to a bioinspired one, along with optimization of the image processing routines, yields improvements in multiple measures of spectral and textural rendition relevant to surgical decision-making.

CONCLUSIONS

These results call for a critical examination of the devices and algorithms that underpin image-guided surgery to ensure that surgeons receive high-quality guidance and patients receive high-quality outcomes as these technologies enter clinical practice.

Validation of a surgical training model containing indocyanine green for near‐infrared fluorescence imaging

Objective

To determine the efficacy of a surgical training model for fluorescence‐guided cancer surgery and validate its utility to detect any residual tumors after tumor resection using electrocautery.

Methods

We developed surgical training models containing indocyanine green (ICG) for near‐infrared (NIR) fluorescence imaging using a root vegetable organic material (konjac). After the fluorescence assessment for the models, the surgical simulation for fluorescence‐guided cancer surgery using electrocautery was performed. ICG‐containing tumors were divided into two surgical groups: “Enucleation” (removal of the entire visible tumor) and “Complete resection” (removal of the tumor with an appropriate 5‐mm surgical margin).

Results

All 12 ICG‐containing tumors were clearly visible from the normal view but not from the flipped view. The tumor resection time was significantly longer in the “Complete resection” group than in the “Enucleation” group (p < .001). The ICG‐containing tumors showed a high tumor‐to background ratio from the normal (average = 45.8) and flipped (average = 19.2) views, indicating that the models including ICG‐containing tumors were useful for a surgical simulation in fluorescence‐guided surgery. The average mean fluorescence intensity of the wound bed was significantly higher in the “Enucleation” group than in the “Complete resection” group (p < .01). No decrease in fluorescence signal was found in the wound bed even at 2 days postresection.

Conclusion

Our surgical training model containing a fluorescent agent is safe, inexpensive, not harmful for humans, and easy to dispose after use. Our model would be beneficial for surgeons to learn NIR fluorescence imaging and to accelerate fluorescence‐guided cancer surgery into clinical application.

Intraoperative imaging in pathology-assisted surgery

The pathological assessment of surgical specimens during surgery can reduce the incidence of positive resection margins, which otherwise can result in additional surgeries or aggressive therapeutic regimens. To improve patient outcomes, intraoperative spectroscopic, fluorescence-based, structural, optoacoustic and radiological imaging techniques are being tested on freshly excised tissue. The specific clinical setting and tumour type largely determine whether endogenous or exogenous contrast is to be detected and whether the tumour specificity of the detected biomarker, image resolution, image-acquisition times or penetration depth are to be prioritized. In this Perspective, we describe current clinical standards for intraoperative tissue analysis and discuss how intraoperative imaging is being implemented. We also discuss potential implementations of intraoperative pathology-assisted surgery for clinical decision-making.

Multiplexed imaging in oncology

In oncology, technologies for clinical molecular imaging are used to diagnose patients, establish the efficacy of treatments and monitor the recurrence of disease. Multiplexed methods increase the number of disease-specific biomarkers that can be detected simultaneously, such as the overexpression of oncogenic proteins, aberrant metabolite uptake and anomalous blood perfusion. The quantitative localization of each biomarker could considerably increase the specificity and the accuracy of technologies for clinical molecular imaging to facilitate granular diagnoses, patient stratification and earlier assessments of the responses to administered therapeutics. In this Review, we discuss established techniques for multiplexed imaging and the most promising emerging multiplexing technologies applied to the imaging of isolated tissues and cells and to non-invasive whole-body imaging. We also highlight advances in radiology that have been made possible by multiplexed imaging.

Towards Complete Tumor Resection: Novel Dual-Modality Probes for Improved Image-Guided Surgery of GRPR-Expressing Prostate Cancer

Nuclear and optical dual-modality probes can be of great assistance in prostate cancer localization, providing the means for both preoperative nuclear imaging and intraoperative surgical guidance. We developed a series of probes based on the backbone of the established GRPR-targeting radiotracer NeoB. The inverse electron demand of the Diels–Alder reaction was used to integrate the sulfo-cyanine 5 dye. Indium-111 radiolabeling, stability studies and a competition binding assay were carried out. Pilot biodistribution and imaging studies were performed in PC-3 tumor-bearing mice, using the best two dual-labeled probes. The dual-modality probes were radiolabeled with a high yield (>92%), were proven to be hydrophilic and demonstrated high stability in mouse serum (>94% intact labeled ligand at 4 h). The binding affinity for the GRPR was in the nanomolar range (21.9–118.7 nM). SPECT/CT images at 2 h p.i. clearly visualized the tumor xenograft and biodistribution studies, after scanning confirmed the high tumor uptake (8.47 ± 0.46%ID/g and 6.90 ± 0.81%ID/g for probe [111In]In-12 and [111In]In-15, respectively). Receptor specificity was illustrated with blocking studies, and co-localization of the radioactive and fluorescent signal was verified by ex vivo fluorescent imaging. Although optimal tumor-to-blood and tumor-to-kidney ratios might not yet have been reached due to the prolonged blood circulation, our probes are promising candidates for the preoperative and intraoperative visualization of GRPR-positive prostate cancer.

Donor–acceptor strategy to construct near infrared AIEgens for cell imaging

A donor–acceptor strategy was applied to construct NIR AIEgens. Six new AIEgens were obtained and among them, DMNIC exhibited the longest emission maximum at 694 nm and was successfully applied for NIR cell imaging.

Molecular Imaging-Guided Sonodynamic Therapy

Low-intensity ultrasound-triggered sonodynamic therapy (SDT) is a promising noninvasive therapeutic modality due to its strong tissue penetration ability. In recent years, with the development of nanotechnology, nanoparticle-based sonosensitizer-mediated SDT has been widely investigated. With the increasing demand for precise and personalized treatment, abundant novel sonosensitizers with imaging capabilities have been developed for determining the optimal therapeutic window, thus significantly enhancing treatment efficacy. In this review, we focus on the molecular imaging-guided SDT. The prevalent mechanisms of SDT are discussed, including ultrasonic cavitation, sonoluminescence, reactive oxygen species, and mechanical damage. In addition, we introduce the major molecular imaging techniques and the design principles based on nanoparticles to achieve efficient imaging. Furthermore, the imaging-guided SDT for the treatment of cancer, bacterial infections, and vascular diseases is summarized. The ultimate goal is to design more effective imaging-guided SDT modalities and provide novel ideas for clinical translation of SDT.

3D printing fluorescent material with tunable optical properties

The 3D printing of fluorescent materials could help develop, validate, and translate imaging technologies, including systems for fluorescence-guided surgery. Despite advances in 3D printing techniques for optical targets, no comprehensive method has been demonstrated for the simultaneous incorporation of fluorophores and fine-tuning of absorption and scattering properties. Here, we introduce a photopolymer-based 3D printing method for manufacturing fluorescent material with tunable optical properties. The results demonstrate the ability to 3D print various individual fluorophores at reasonably high fluorescence yields, including IR-125, quantum dots, methylene blue, and rhodamine 590. Furthermore, tuning of the absorption and reduced scattering coefficients is demonstrated within the relevant mamalian soft tissue coefficient ranges of 0.005-0.05 mm-1 and 0.2-1.5 mm-1, respectively. Fabrication of fluorophore-doped biomimicking and complex geometric structures validated the ability to print feature sizes less than 200 μm. The presented methods and optical characterization techniques provide the foundation for the manufacturing of solid 3D printed fluorescent structures, with direct relevance to biomedical optics and the broad adoption of fast manufacturing methods in fluorescence imaging.

Photophysical Properties of Indocyanine Green in the Shortwave Infrared Region

With the growing development of new contrast agents for optical imaging using near-infrared and shortwave infrared (SWIR) wavelengths, it is essential to have consistent bench-marks for emitters in these regions. Indocyanine green (ICG), a ubiquitous and FDA-approved organic dye and optical imaging agent, is commonly employed as a standard for photophysical properties and biological performance for imaging experiments at these wavelengths. Yet, its reported photophysical properties across organic and aqueous solvents vary greatly in the literature, which hinders its ability to be used as a consistent benchmark. Herein, we measure photophysical properties in organic and aqueous solvents using InGaAs detection (~950-1,700 nm), providing particular relevance for SWIR imaging.

Biodegradable Harmonophores for Targeted High-Resolution In Vivo Tumor Imaging

Optical imaging probes have played a major role in detecting and monitoring a variety of diseases. In particular, nonlinear optical imaging probes, such as second harmonic generating (SHG) nanoprobes, hold great promise as clinical contrast agents, as they can be imaged with little background signal and unmatched long-term photostability. As their chemical composition often includes transition metals, the use of inorganic SHG nanoprobes can raise long-term health concerns. Ideally, contrast agents for biomedical applications should be degraded in vivo without any long-term toxicological consequences to the organism. Here, we developed biodegradable harmonophores (bioharmonophores) that consist of polymer-encapsulated, self-assembling peptides that generate a strong SHG signal. When functionalized with tumor cell surface markers, these reporters can target single cancer cells with high detection sensitivity in zebrafish embryos in vivo. Thus, bioharmonophores will enable an innovative approach to cancer treatment using targeted high-resolution optical imaging for diagnostics and therapy.

Near-Infrared Fluorescence Imaging of Breast Cancer and Axillary Lymph Nodes After Intravenous Injection of Free Indocyanine Green

Background

Near-infrared fluorescence imaging (NIRFI) of breast cancer (BC) after the intravenous (IV) injection of free indocyanine green (fICG) has been reported to be feasible. However, some questions remained unclarified.

Objective

To evaluate the distribution of fICG in BC and the axillary lymph nodes (LNs) of women undergoing surgery with complete axillary LN dissection (CALND) and/or selective lymphadenectomy (SLN) of sentinel LNs (NCT no. 01993576 and NCT no. 02027818).

Methods

An intravenous injection of fICG (0.25 mg/kg) was administered to one series of 20 women undergoing treatment with mastectomy, the day before surgery in 5 (group 1) and immediately before surgery in 15 (group 2: tumor localization, 25; and pN+ CALND, 4) as well as to another series of 20 women undergoing treatment with tumorectomy (group 3). A dedicated NIR camera was used for ex vivo fluorescence imaging of the 45 BC lesions and the LNs.

Results

In group 1, two of the four BC lesions and one large pN+ LN exhibited fluorescence. In contrast, 24 of the 25 tumors in group 2 and all of the tumors in group 3 were fluorescent. The sentinel LNs were all fluorescent, as well as some of the LNs in all CALND specimens. Metastatic cells were found in the fluorescent LNs of the pN+ cases. Fluorescent BC lesions could be identified ex vivo on the surface of the lumpectomy specimen in 14 of 19 cases.

Conclusions

When fICG is injected intravenously just before surgery, BC can be detected using NIRFI with high sensitivity, with metastatic axillary LNs also showing fluorescence. Such a technical approach seems promising in the management of BC and merits further investigation.

Novel Multimodal, Multiscale Imaging System with Augmented Reality

A novel multimodal, multiscale imaging system with augmented reality capability were developed and characterized. The system offers 3D color reflectance imaging, 3D fluorescence imaging, and augmented reality in real time. Multiscale fluorescence imaging was enabled by developing and integrating an in vivo fiber-optic microscope. Real-time ultrasound-fluorescence multimodal imaging used optically tracked fiducial markers for registration. Tomographical data are also incorporated using optically tracked fiducial markers for registration. Furthermore, we characterized system performance and registration accuracy in a benchtop setting. The multiscale fluorescence imaging facilitated assessing the functional status of tissues, extending the minimal resolution of fluorescence imaging to ~17.5 µm. The system achieved a mean of Target Registration error of less than 2 mm for registering fluorescence images to ultrasound images and MRI-based 3D model, which is within clinically acceptable range. The low latency and high frame rate of the prototype system has shown the promise of applying the reported techniques in clinically relevant settings in the future.

A novel fluorescent cardiac imaging system for preclinical intraoperative angiography

BACKGROUND

Intraoperative coronary angiography can tremendously reduce early coronary bypass graft failures. Fluorescent cardiac imaging provides an advanced method for intraoperative observation and real-time quantitation of blood flow with high resolution.

METHODS

We devised a system comprised of an LED light source, special filters, lenses and a detector for preclinical coronary artery angiography. The optical setup was implemented by using two achromatic doublet lenses, two positive meniscus lenses, a band-pass filter, a pinhole and a CCD sensor. The setup was optimized by Zemax software. Optical design was further challenged to obtain more parallel light beams, less diffusion and higher resolutions to levels as small as arterioles. Ex vivo rat hearts were prepared and coronary arteries were retrogradely perfused by indocyanine green (ICG). Video angiography was employed to assess blood flow and plot time-dependent fluorescence intensity curve (TIC). Quantitation of blood flow was performed by calculating either the gradient of TIC or area under curve. The correlation between blood flow and each calculated parameters was assessed and used to evaluate the quality of flow.

RESULTS

High-resolution images of flow in coronary arteries were obtained as precise as 62 µm vessel diameter, by our custom-made ICG angiography system. The gradient of TIC was 3.4-6.3 s^-1, while the area under curve indicated 712-1282 s values which ultimately gained correlation coefficients of 0.9938 and 0.9951 with relative blood flow, respectively.

CONCLUSION

The present ICG angiography system may facilitate evaluation of blood flow in animal studies of myocardial infarction and coronary artery grafts intraoperatively.

Bimodal Imaging of Mouse Peripheral Nerves with Chlorin Tracers

Almost 17 million Americans have a history of cancer, a number expected to reach over 22 million by 2030. Cancer patients often undergo chemotherapy in the form of antineoplastic agents such as cis-platin and paclitaxel. Though effective, these agents can induce debilitating side effects; the most common neurotoxic effect, chemotherapy-induced peripheral neuropathy (CIPN), can endure long after treatment ends. Despite the widespread and chronic nature of the dysfunction, no tools exist to quantitatively measure chemotherapy-induced peripheral neuropathy. Such a tool would not only benefit patients but their stratification could also save significant financial and social costs associated with neuropathic pain. In our first step toward addressing this unmet clinical need, we explored a novel dual approach to localize peripheral nerves: Cerenkov luminescence imaging (CLI) and fluorescence imaging (FI). Our approach revolves around the targeting and imaging of voltage-gated sodium channel subtype Na_V1.7, highly expressed in peripheral nerves from both harvested human and mouse tissues. For the first time, we show that Hsp1a, a radiolabeled Na_V1.7-selective peptide isolated from Homoeomma spec. Peru, can serve as a targeted vector for delivering a radioactive sensor to the peripheral nervous system. In situ, we observe high signal-to-noise ratios in the sciatic nerves of animals injected with fluorescently labeled Hsp1a and radiolabeled Hsp1a. Moreover, confocal microscopy on fresh nerve tissue shows the same high ratios of fluorescence, corroborating our in vivo results. This study indicates that fluorescently labeled and radiolabeled Hsp1a tracers could be used to identify and demarcate nerves in a clinical setting.

In Cellulo Generation of Fluorescent Probes for Live-Cell Imaging of Cylooxygenase-2

Live-cell imaging with fluorescent probes is an essential tool in chemical biology to visualize the dynamics of biological processes in real-time. Intracellular disease biomarker imaging remains a formidable challenge due to the intrinsic limitations of conventional fluorescent probes and the complex nature of cells. This work reports the in cellulo assembly of a fluorescent probe to image cyclooxygenase-2 (COX-2). We developed celecoxib-azide derivative 14, possessing favorable biophysical properties and excellent COX-2 selectivity profile. In cellulo strain-promoted fluorogenic click chemistry of COX-2-engaged compound 14 with non/weakly-fluorescent compounds 11 and 17 formed fluorescent probes 15 and 18 for the detection of COX-2 in living cells. Competitive binding studies, biophysical, and comprehensive computational analyses were used to describe protein-ligand interactions. The reported new chemical toolbox enables precise visualization and tracking of COX-2 in live cells with superior sensitivity in the visible range.

A matrix metalloproteinase activation probe for painting human tumours

A probe that allows specific 'painting' of human tumours is described. Probe activation was mediated by specific matrix metalloproteinases, resulting not only in disruption of a FRET pair, but in the generation of a fragment that "fluorescently paints" human tumours. This probe demonstrated rapid and effective human tumour labelling with the potential to allow margin detection during surgical resection.

Optical Imaging Modalities: Principles and Applications in Preclinical Research and Clinical Settings

With the ability to noninvasively image and monitor molecular processes within tumors, molecular imaging represents a fundamental tool for cancer scientists. In the current review, we describe emergent optical technologies for molecular imaging. We aim to provide the reader with an overview of the fundamental principles on which each imaging strategy is based, to introduce established and future applications, and to provide a rationale for selecting optical technologies for molecular imaging depending on disease location, biology, and anatomy. To accelerate clinical translation of imaging techniques, we also describe examples of practical applications in patients. Elevating these techniques into standard-of-care tools will transform patient stratification, disease monitoring, and response evaluation.

Molecularly Imprinted Polymers: Antibody Mimics for Bioimaging and Therapy

Molecularly imprinted polymers (MIPs) are tailor-made chemical receptors that recognize and bind target molecules with a high affinity and selectivity. MIPs came into the spotlight in 1993 when they were dubbed "antibody mimics," and ever since, they have been widely studied for the extraction or trapping of chemical pollutants, in immunoassays, and for the design of sensors. Owing to novel synthesis strategies resulting in more biocompatible MIPs in the form of soluble nanogels, these synthetic antibodies have found favor in the biomedical domain since 2010, when for the first time, they were shown to capture and eliminate a toxin in live mice. This review, covering the years 2015-2020, will first describe the rationale behind these antibody mimics, and the different synthesis methods that have been employed for the preparation of MIPs destined for in vitro and in vivo targeting and bioimaging of cancer biomarkers, an emerging and fast-growing area of MIP applications. MIPs have been synthesized for targeting and visualizing glycans and protein-based cell receptors overexpressed in certain diseases, which are well-known biomarkers for example for tumors. When loaded with drugs, the MIPs could locally kill the tumor cells, making them efficient therapeutic agents. We will end the review by reporting how MIPs themselves can act as therapeutics by inhibiting cancer growth. These works mark a new opening in the use of MIPs for antibody therapy and even immunotherapy, as materials of the future in nanomedicine.

A Review on Advances in Intra-operative Imaging for Surgery and Therapy: Imagining the Operating Room of the Future

With the advent of Minimally Invasive Surgery (MIS), intra-operative imaging has become crucial for surgery and therapy guidance, allowing to partially compensate for the lack of information typical of MIS. This paper reviews the advancements in both classical (i.e. ultrasounds, X-ray, optical coherence tomography and magnetic resonance imaging) and more recent (i.e. multispectral, photoacoustic and Raman imaging) intra-operative imaging modalities. Each imaging modality was analyzed, focusing on benefits and disadvantages in terms of compatibility with the operating room, costs, acquisition time and image characteristics. Tables are included to summarize this information. New generation of hybrid surgical room and algorithms for real time/in room image processing were also investigated. Each imaging modality has its own (site- and procedure-specific) peculiarities in terms of spatial and temporal resolution, field of view and contrasted tissues. Besides the benefits that each technique offers for guidance, considerations about operators and patient risk, costs, and extra time required for surgical procedures have to be considered. The current trend is to equip surgical rooms with multimodal imaging systems, so as to integrate multiple information for real-time data extraction and computer-assisted processing. The future of surgery is to enhance surgeons eye to minimize intra- and after-surgery adverse events and provide surgeons with all possible support to objectify and optimize the care-delivery process.

Classification of hyperspectral endocrine tissue images using support vector machines

BACKGROUND

Thyroidectomy is one of the most commonly performed surgical procedures. The region of the neck has a very complex structural organization. It would be beneficial to introduce a tool that can assist the surgeon in tissue discrimination during the procedure. One such solution is the noninvasive and contactless technique, called hyperspectral imaging (HSI).

METHODS

To interpret the HSI data, we implemented a supervised classification method to automatically discriminate the parathyroid, the thyroid, and the recurrent laryngeal nerve from surrounding tissue(muscle, skin) and materials (instruments, gauze). A leave-one-patient-out cross-validation was performed.

RESULTS

The best performance was obtained using support vector machine (SVM) with a classification and visualization in less than 1.4 seconds. A mean patient accuracy of 68% ± 23% was obtained for all tissues and material types.

CONCLUSIONS

The proposed method showed promising results and have to be confirmed on a larger cohort of patient data.

In vivo near-infrared fluorescent optical imaging for CNS drug discovery

INTRODUCTION

In vivo imaging technologies have become integral and essential component of drug discovery, development, and clinical assessment for central nervous system (CNS) diseases. Near-infrared (NIR) fluorescence imaging in the range of 650-950 nm is widely used for pre-clinical in vivo imaging studies. The recent expansion of NIR imaging into the shortwave infrared (SWIR, 1000-1700 nm) window enabled improvements in tissue penetration and resolution required for anatomical, dynamic, and molecular neuroimaging with high potential for clinical translation.

AREAS COVERED

This review focuses on the latest progress in near-infrared (NIR)-fluorescent optical imaging modalities with an emphasis on the SWIR window. Advantages and challenges in developing novel organic and inorganic SWIR emitters, with special attention to their toxicology and pharmacology, are discussed. Examples of their application in preclinical imaging of brain function and pathology provide a platform to assess the potential for their clinical translation.

EXPERT OPINION

Propelled through concomitant technological advancements in imaging instrumentation, algorithms and new SWIR emitters, SWIR imaging has addressed key barriers to optical imaging modalities used in pre-clinical studies addressing the CNS. Development of biocompatible SWIR emitters and adoption of SWIR into multi-modal imaging modalities promise to rapidly advance optical imaging into translational studies and clinical applications.

Indocyanine green matching phantom for fluorescence-guided surgery imaging system characterization and performance assessment

SIGNIFICANCE

Expanded use of fluorescence-guided surgery with devices approved for use with indocyanine green (ICG) has led to a range of commercial systems available. There is a compelling need to be able to independently characterize system performance and allow for cross-system comparisons.

AIM

The goal of this work is to expand on previous proposed fluorescence imaging standard designs to develop a long-term stable phantom that spectrally matches ICG characteristics and utilizes 3D printing technology for incorporating tissue-equivalent materials.

APPROACH

A batch of test targets was created to assess ICG concentration sensitivity in the 0.3- to 1000-nM range, tissue-equivalent depth sensitivity down to 6 mm, and spatial resolution with a USAF test chart. Comparisons were completed with a range of systems that have significantly different imaging capabilities and applications, including the Li-Cor® Odyssey, Li-Cor® Pearl, PerkinElmer® Solaris, and Stryker® Spy Elite.

RESULTS

Imaging of the ICG-matching phantoms with all four commercially available systems showed the ability to benchmark system performance and allow for cross-system comparisons. The fluorescence tests were able to assess differences in the detectable concentrations of ICG with sensitivity differences >10× for preclinical and clinical systems. Furthermore, the tests successfully assessed system differences in the depth-signal decay rate, as well as resolution performance and image artifacts. The manufacturing variations, photostability, and mechanical design of the tests showed promise in providing long-term stable standards for fluorescence imaging.

CONCLUSIONS

The presented ICG-matching phantom provides a major step toward standardizing performance characterization and cross-system comparisons for devices approved for use with ICG. The developed hybrid manufacturing platform can incorporate long-term stable fluorescing agents with 3D printed tissue-equivalent material. Further, long-term testing of the phantom and refinements to the manufacturing process are necessary for future implementation as a widely adopted fluorescence imaging standard.

C-Met targeted fluorescence molecular endoscopy in Barrett's esophagus patients and identification of outcome parameters for phase-I studies

Fluorescence molecular endoscopy (FME) is an emerging technique in the field of gastroenterology that holds potential to improve diagnosis and guide therapy, by serving as a 'red-flag' endoscopic imaging technique. Here, we investigated the safety, feasibility and optimal method of administration of EMI-137, targeting c-Met, during FME in Barrett's Esophagus (BE) and report several outcome parameters for early phase FME studies.

Methods: FME was performed in 15 Barrett's neoplasia patients. EMI-137 was administered to three cohorts of five patients: 0.13 mg/kg intravenously (IV); 0.09 mg/kg IV or topically at a dose of 200 μg/cm BE (n=1) or 100 μg/cm BE (n=4). Fluorescence was visualized in vivo, quantified in vivo using multi-diameter single-fiber reflectance, single-fiber fluorescence (MDSFR/SFF) spectroscopy and correlated to histopathology and immunohistochemistry. EMI-137 localization was assessed using fluorescence microscopy.

Results: FME using different IV and topical doses of EMI-137 appeared to be safe and correctly identified 16/18 lesions, although modest target-to-background ratios were observed (median range of 1.12-1.50). C-Met overexpression varied between lesions, while physiological expression in the stomach-type epithelium was observed. Microscopically, EMI-137 accumulated around the neoplastic cell membranes. We identified several outcome parameters important for the validation of EMI-137 for FME: 1) the optimal administration route; 2) optimal dose and safety; 3) in vivo FME contrast; 4) quantification of intrinsic fluorescence; 5) ex vivo correlation of fluorescence, histopathology and target expression; and 6) microscopic tracer distribution.

Conclusions: C-Met targeted FME using EMI-137 may not be the ideal combination to improve BE surveillance endoscopies, however the identified outcome parameters may serve as a valuable guidance for designing and performing future early phase clinical FME studies, independent of which fluorescent tracer is investigated.

Fluorescence-guided imaging for resection margin evaluation in head and neck cancer patients using cetuximab-800CW: A quantitative dose-escalation study

Tumor-positive resection margins are present in up to 23% of head and neck cancer (HNC) surgeries, as intraoperative techniques for real-time evaluation of the resection margins are lacking. In this study, we investigated the safety and potential clinical value of fluorescence-guided imaging (FGI) for resection margin evaluation in HNC patients. We determined the optimal cetuximab-800CW dose by quantification of intrinsic fluorescence values using multi-diameter single-fiber reflectance, single-fiber fluorescence (MDSFR/SFF) spectroscopy.

Methods: Five cohorts of three HNC patients received cetuximab-800CW systemically: three single dose cohorts (10, 25, 50 mg) and two cohorts pre-dosed with 75 mg unlabeled cetuximab (15 or 25 mg). Fluorescence visualization and MDSFR/SFF spectroscopy quantification was performed and were correlated to histopathology.

Results: There were no study-related adverse events higher than Common Terminology Criteria for Adverse Events grade-II. Quantification of intrinsic fluorescence values showed a dose-dependent increase in background fluorescence in the single dose cohorts (p<0.001, p<0.001), which remained consistently low in the pre-dosed cohorts (p=0.6808). Resection margin status was evaluated with a sensitivity of 100% (4/4 tumor-positive margins) and specificity of 91% (10/11 tumor-negative margins).

Conclusion: A pre-dose of 75 mg unlabeled cetuximab followed by 15 mg cetuximab-800CW was considered the optimal dose based on safety, fluorescence visualization and quantification of intrinsic fluorescence values. We were able to use a lower dose cetuximab-800CW than previously described, while remaining a high sensitivity for tumor detection due to application of equipment optimized for IRDye800CW detection, which was validated by quantification of intrinsic fluorescence values.

Mini-Platform for Off-On Near-Infrared Fluorescence Imaging Using Peptide-Targeting Ligands

Here, we propose a zwitterionic near-infrared (NIR) fluorophore-tryptophan (Trp) conjugate with a cleavable linker as a minimal-sized versatile platform (MP) for the preparation of peptide ligand-based off-on type molecular probes. The zwitterionic NIR fluorophore in MP undergoes fluorescence quenching via a photoinduced electron transfer mechanism when in close proximity to tryptophan, and nonspecific binding with serum proteins is minimized by the zwitterionicity of the fluorophore. The linker can be cleaved inside cancer cells in response to tumor-associated stimuli. As a proof-of-concept experiment, ATTO655 was covalently linked with Trp via a diarginine linker to form an MP. A cyclic peptide consisting of Arg-Gly-Asp-d-Phe-Lys (cRGD) was used as a cancer-targeting ligand and was conjugated to the MP to form cRGD-MP. The NIR fluorescence of cRGD-MP could be selectively turned on inside the target cancer cells, thereby enabling specific fluorescence imaging of integrin α_vβ₃-overexpressing cancer cells in vitro and in vivo.

Optical and Optoacoustic Imaging

The present chapter summarizes progress with optical methods that go beyond human vision. The focus is on two particular technologies: fluorescence molecular imaging and optoacoustic (photoacoustic) imaging. The rationale for the selection of these two methods is that in contrast to optical microscopy techniques, both fluorescence and optoacoustic imaging can achieve large fields of view, i.e., spanning several centimeters in two or three dimensions. Such fields of views relate better to human vision and can visualize large parts of tissue, a necessary premise for clinical detection. Conversely, optical microscopy methods only scan millimeter-sized dimensions or smaller. With such operational capacity, optical microscopy methods need to be guided by another visualization technique in order to scan a very specific area in tissue and typically only provide superficial measurements, i.e., information from depths that are of the order of 0.05-1 mm. This practice has generally limited their clinical applicability to some niche applications, such as optical coherence tomography of the retina. On the other hand, fluorescence molecular imaging and optoacoustic imaging emerge as more global optical imaging methods with wide applications in surgery, endoscopy, and non-invasive clinical imaging, as summarized in the following. The current progress in this field is based on a volume of recent review and other literature that highlights key advances achieved in technology and biomedical applications. Context and figures from references from the authors of this chapter have been used here, as it reflects our general view of the current status of the field.

Precise hepatectomy in the intelligent digital era

In the past 20 years, the concept of surgery has undergone profound changes. Surgical practice has shifted from emphasizing the complete elimination of lesions to achieving optimal rehabilitation in patients. Collaborative optimization of surgery consists of three core elements, removal of lesions, organ protection and injury close monitoring, and controlled surgical intervention. As a result, the traditional surgical paradigm has quietly transformed into a modern precision surgical paradigm. In this review, we summarized the latest breakthroughs and applications of precision medicine in liver surgery. In addition, we also outlined the progresses that have been made in precision liver surgery, the opportunities and challenges that may encountered in the future.

[Three-dimensional visualization combined with indocyanine green fluorescence imaging in diagnosis and treatment of primary hepatocellular carcinoma]

OBJECTIVE

To explore the value of three-dimensional visualization technology (3DVT) combined with indocyanine green (ICG) fluorescence imaging in the diagnosis and treatment of primary hepatocellular carcinoma (HCC).

METHODS

We retrospectively analyzed the clinical data of 154 patients with HCC admitted to the Department of Hepatobiliary Surgery, Zhujiang Hospital, Southern Medical University between January, 2016 and November, 2018. In 57 of the patients (3DVT group), preoperative CT and Gd-EOB-DTPA-enhanced MRI were performed and 3D visualization and surgical planning was carried out before the operation; intraoperative ICG florescence imaging was performed for real-time detection of the tumor location and demarcation, intrahepatic satellite lesions and metastases. According to the intraoperative fluorescent signals and 3D visualization-based surgical planning, the final surgical plan was determined. In the other 97 patients (control group), conventional surgical assessment and surgical resection of the tumor was carried out. The preoperative imaging findings, intraoperative tumor detection, postoperative laboratory results, pathological reports, and follow-up data of the patients were analyzed.

RESULTS

In 3DVT group, 63 and 70 lesions were detected by preoperative CT and MRI, respectively; compared with CT examination, intraoperative ICG florescence imaging revealed additional 17 lesions, among which 10 were pathologically confirmed as HCC and 7 as cirrhosis nodules. The median volume of bleeding was 300 mL in 3DVT group, significantly less than that in the control group (400 mL; Z=2.291, P=0.022). In both groups, serious complications or perioperative death occurred in none of the patients. The incidence of postoperative complications was significantly lowed in 3DVT group than in the control group [21% (12/57) vs 48.4% (47/97); χ2=11.406, P=0.001]. The overall disease-free survival rate at 2 years after the operation was significantly higher in 3DVT group than in the control group (74.9% vs 28.9%, P=0.022).

CONCLUSIONS

3DVT combined with ICG fluorescence imaging allows precise preoperative diagnosis, surgical planning and implementation, intraoperative detection of small liver cancers and precise navigation for HCC treatment, thereby helping to reduce postoperative complications and improve the disease-free survival rate of the patients.

Fluorescence imaging reversion using spatially variant deconvolution

Fluorescence imaging opens new possibilities for intraoperative guidance and early cancer detection, in particular when using agents that target specific disease features. Nevertheless, photon scattering in tissue degrades image quality and leads to ambiguity in fluorescence image interpretation and challenges clinical translation. We introduce the concept of capturing the spatially-dependent impulse response of an image and investigate Spatially Adaptive Impulse Response Correction (SAIRC), a method that is proposed for improving the accuracy and sensitivity achieved. Unlike classical methods that presume a homogeneous spatial distribution of optical properties in tissue, SAIRC explicitly measures the optical heterogeneity in tissues. This information allows, for the first time, the application of spatially-dependent deconvolution to correct the fluorescence images captured in relation to their modification by photon scatter. Using experimental measurements from phantoms and animals, we investigate the improvement in resolution and quantification over non-corrected images. We discuss how the proposed method is essential for maximizing the performance of fluorescence molecular imaging in the clinic.

Fluorescence Imaging of Peripheral Nerves by a Nav1.7-Targeted Inhibitor Cystine Knot Peptide

Twenty million Americans suffer from peripheral nerve injury caused by trauma and medical disorders, resulting in a broad spectrum of potentially debilitating side effects. In one out of four cases, patients identify surgery as the root cause of their nerve injury. Particularly during tumor resections or after traumatic injuries, tissue distortion and poor visibility can challenge a surgeon's ability to precisely locate and preserve peripheral nerves. Intuitively, surgical outcomes would improve tremendously if nerves could be highlighted using an exogeneous contrast agent. In clinical practice, however, the current standard of care-visual examination and palpation-remains unchanged. To address this unmet clinical need, we explored the expression of voltage-gated sodium channel Na_v1.7 as an intraoperative marker for the peripheral nervous system. We show that expression of Na_v1.7 is high in peripheral nerves harvested from both human and mouse tissue. We further show that modification of a Na_v1.7-selective peptide, Hsp1a, can serve as a targeted vector for delivering a fluorescent sensor to the peripheral nervous system. Ex vivo, we observe a high signal-to-noise ratio for fluorescently labeled Hsp1a in both histologically prepared and fresh tissue. Using a surgical fluorescent microscope, we show in a simulated clinical scenario that the identification of mouse sciatic nerves is possible, suggesting that fluorescently labeled Hsp1a tracers could be used to discriminate nerves from their surrounding tissues in a routine clinical setting.

Contemporary Approach to Locally Advanced Oral Cavity Squamous Cell Carcinoma

PURPOSE OF REVIEW

Surgical management of locally advanced oral cavity squamous cell carcinomas (OCSCC) has long been recognized as a primary treatment modality. Technological advances have led to significant improvements in our surgical approach, from improvement in the visualization of tumors to more efficient and precise reconstruction. Here, we review the latest technological advances in surgical extirpation and reconstruction of locally advanced OCSCCs.

RECENT FINDINGS

The focus of technological innovation in surgical extirpation has been on improving visualization, with the use of intraoperative ultrasound for margin delineation, intraoperative navigation, narrow-band imaging, and the use of fluorescence. Though early, these are promising steps to ensuring complete resection of the cancer. Advances in reconstruction have been centered on the incorporation of computer assisted design, manufacturing, and virtual surgical planning, allowing for more complex three-dimensional defects to be expeditiously reconstructed. As these technologies are still under development, their impact on oncologic outcomes are not yet robustly defined; however, as technology continues to advance and become more widely available, new technologies will undoubtedly become integrated into enhancing surgical precision and planning.

Multi-Parametric Standardization of Fluorescence Imaging Systems Based on a Composite Phantom

OBJECTIVE

Fluorescence molecular imaging (FMI) has emerged as a promising tool for surgical guidance in oncology, with one of the few remaining challenges being the ability to offer quality control and data referencing. This paper investigates the use of a novel composite phantom to correct and benchmark FMI systems.

METHODS

This paper extends on previous work by describing a phantom design that can provide a more complete assessment of FMI systems through quantification of dynamic range and determination of spatial illumination patterns for both reflectance and fluorescence imaging. Various performance metrics are combined into a robust and descriptive "system benchmarking score," enabling not only the comprehensive comparison of different systems, but also for the first time, correction of the acquired data.

RESULTS

We show that systems developed for targeted fluorescence imaging can achieve benchmarking scores of up to 70%, while clinically available systems optimized for indocyanine green are limited to 50%, mostly due to greater leakage of ambient and excitation illumination and lower resolution. The image uniformity can also be approximated and employed for image flat-fielding, an important milestone toward data referencing. In addition, we demonstrate composite phantom use in assessing the performance of a surgical microscope and of a raster-scan imaging system.

CONCLUSION

Our results suggest that the new phantom has the potential to support high-fidelity FMI through benchmarking and image correction.

SIGNIFICANCE

Standardization of the FMI is a necessary process for establishing good imaging practices in clinical environments and for enabling high-fidelity imaging across patients and multi-center imaging studies.