Fluorescence properties and metabolic features of indocyanine green (ICG) as related to angiography

Indocyanine green J-aggregate (IJA) theranostics: Challenges and opportunities

Indocyanine green is an FDA-approved fluorescent imaging dye used for determining cardiac output, hepatic function, liver blood flow, and retinal perfusion. It has been investigated preclinically in photoacoustic imaging and photothermal therapy (PTT); however, ICG photodegradation limits its biomedical applications. An aggregated form of ICG, known as J-aggregate (IJA), exhibits superior photoacoustic signals and thermal stability than the monomeric ICG. Nevertheless, IJA still suffers from low stability in the biological milieu, and short in vivo blood circulation. To address these limitations, a range of nanocarriers have been developed to enhance IJA stability and performance. This review focuses on IJA potentials and limitations, besides the recent development of IJA-loaded nanocarriers, particularly for cancer imaging and therapy.

Use of near-infrared fluorescence angiography with indocyanine green to evaluate direct cutaneous arteries used for canine axial pattern flaps

OBJECTIVE

To describe the use of near-infrared angiography (NIRFA) to identify the vascularization of three canine axial pattern flaps (APFs) omocervical (OMO), thoracodorsal (THO), and caudal superficial epigastric (CSE); to establish a vascular fluorescence pattern (VFP) grading system; and to evaluate the effect of NIRFA on surgeon flap dimension planning compared to traditional landmark palpation (LP) and visualization assessments.

STUDY DESIGN

Experimental study.

ANIMALS

A total of 15 healthy, client-owned dogs.

METHODS

Dogs were sedated and flap sites were clipped. LP-based margins were drawn and preinjection images were recorded. Indocyanine green (ICG) was administered and VFP images were recorded. VFP scores were determined by five surgeons. Margin alterations were performed based on NIRFA-ICG images. Altered measurements were compared between LP and NIRFA-ICG images.

RESULTS

Vascularization of the CSE flap was most visible with NIRFA with VFP scores 4/4 for 13/15 dogs. Intersurgeon agreement for VFP grades was poorest for THO (ICC = 0.35) and intermediate for OMO (ICC = 0.49) flaps. Surgeons were more likely to adjust dimensions for CSE flaps relative to OMO (OR 17.3, 95% CI: 6.2, 47.8) or THO (25.5; 8.6, 75.7).

CONCLUSION

Using a grading system, we demonstrated that the CSE flap was most visible. Surgeons were more likely to adjust the LP-CSE flap margins based on fluorescence patterns and were more likely to rely on LP when visualization scores were low.

CLINICAL SIGNIFICANCE

NIRFA has possible applications identifying some direct cutaneous arteries of APFs and their associated angiosomes in real-time. Further investigation is indicated to study NIRFA's potential to improve patient specific APF planning.

Recent Updates on the Diagnosis and Management of Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is the leading cause of irreversible blindness in the Western world, with a higher prevalence among Europeans and North Americans than that in Africans, Hispanics, and Asians. Advanced AMD is categorized as atrophic (dry) or exudative (wet/neovascular age-related macular degeneration [nAMD]). Dry AMD is characterized by progressive geographic atrophy of the retinal pigment epithelium and outer retinal layers, whereas nAMD is characterized by new vessels that invade the subretinal and/or subretinal pigment epithelium spaces. Existing treatments delay the onset of advanced AMD and reverses vision loss for a couple of years before atrophy usually decreases central visual acuity. We searched PubMed and Medline databases from January 1, 1980, to December 1, 2023, using the following search terms: macular degeneration, choroidal neovascularization, geographic atrophy, drusen, age-related maculopathy, AMD, ARMD, and anti-VEGF. Relevant articles in English (or English translations) were retrieved and reviewed. Bibliographies of the identified manuscripts were also reviewed to identify relevant studies. Age-related macular degeneration most commonly affects people older than 55 years. Visual prognosis varies, with advanced lesions (nAMD and geographic atrophy) leading to rapid, progressive loss of central vision and contrast sensitivity. Although AMD is not a life-threatening disease, reduced vision profoundly compromises quality of life and necessitates living assistance for many patients. Over the past 2 decades, advances in prevention (vitamin supplementation) and therapy (antivascular endothelial growth factor and complement inhibitor drugs) have reduced vision loss and blindness. Further research is needed to decrease the incidence of blindness in patients with advanced disease.

Development of Indocyanine Green/Methyl-β-cyclodextrin Complex-Loaded Liposomes for Enhanced Photothermal Cancer Therapy

Photothermal therapy (PTT) is a promising cancer therapeutic approach due to its spatial selectivity and high potency. Indocyanine green (ICG) has been considered a biocompatible PTT agent. However, ICG has several challenges to hinder its clinical use including rapid blood clearance and instability to heat, light, and solvent, leading to a loss of photoactivation property and PTT efficacy. Herein, we leveraged stabilizing components, methyl-β-cyclodextrin and liposomes, in one nanoplatform (ICD lipo) to enhance ICG stability and the photothermal therapeutic effect against cancer. Compared to ICG, ICD lipo displayed a 4.8-fold reduction in degradation in PBS solvent after 30 days and a 3.4-fold reduction in photobleaching after near-infrared laser irradiation. Moreover, in tumor-bearing mice, ICD lipo presented a 2.7-fold increase in tumor targetability and inhibited tumor growth 9.6 times more effectively than did ICG without any serious toxicity. We believe that ICD lipo could be a potential PTT agent for cancer therapeutics.

Fluorescence Intensity between Standard versus Diluted Indocyanine Green to Evaluate Flap Perfusion in Rats

The ideal dose for indocyanine green (ICG) has not been established yet, although 5 mg per mL is widely accepted for free flap evaluation. Due to its high price and rarity in developing countries, this preliminary study aimed to find the lowest concentration of ICG without reducing the fluorescence quality read by near-infrared camera in animal models. An experimental study was conducted on 25 Wistar rats divided into five groups based on the injected ICG, which was in 5 mg per mL, 3.75 mg per mL, 2.5 mg per mL, 1.25 mg per mL, and 0.5 mg per mL concentrations. The epigastric flap was elevated and confirmed to be vital on the fifth day. Upon confirmation, bolus IV injection of ICG was given via the tail, and the flap was read using near-infrared camera. The 25 different videos are randomized and rated individually in a blind manner by five microsurgeons, chosen beforehand. The videos are evaluated with a scoring system ranging from 0 to 4, assessing fluorescence visibility and flap vasculature. Nonetheless, the intraclass correlation coefficient is 0.779. There was no difference between standard and diluted ICG concentrations to evaluate flap perfusion. The 2.5 mg per mL concentration of ICG was the most favorable. This finding is not clinically relevant for application in human subjects yet. However, this study shows promising results for further usage of ICG in daily practice at a lower cost.

Clinical applications of aqueous angiography in glaucoma

Aqueous humor outflow (AHO) pathways are the main site of resistance causing elevated intraocular pressure in glaucoma, especially primary open-angle glaucoma patients. With the recently introduced technique of aqueous angiography (AA); functional, real time assessment of AHO from proximal (trabecuar meshwork) to distal pathways under physiological conditions has been made possible. AHO pathways are segmental, and AA can identify high-flow region (increased angiographic signals) and low flow region (decreased angiographic signals) in an individual. With the introduction of canal-based minimally invasive glaucoma surgeries (MIGS), the assessment of AHO can help guide the placement of stents/incisions during MIGS procedures. This can allow individualized and targeted MIGS procedures in glaucoma patients for better results. Based on the density of AHO pathways visualized on AA, surgeons can decide whether to perform MIGS or conventional glaucoma surgery for improved outcomes for the patient. Immediate intraoperative assessment for functionality of the MIGS procedure performed is possible with AA, allowing for surgical adjustments of MIGS procedure in the same sitting, if needed. This review provides a summary of the studies performed with AA to date, with a special focus on Indian patients. It covers the basics and clinical applications of AA for improving surgical outcomes in glaucoma patients.

Repurposing indocyanine green: exploring the potential of an old drug in modern medicine

The repurposing of existing drugs, referred to as theranostics, has made profound impacts on precision medicine. Indocyanine green (ICG), a well-established and clinical dye, has continued to be a star agent, described as a multifunctional molecule with concurrent photo- or sono-sensitiveness capabilities and co-delivery accessibility, showing remarkable potential in the area of unimodal or multimodal imaging-guided therapy of various diseases, leading to the extensive consideration of immediate clinical translations. In this review, we strive to bring the understanding of repurposing performance assessment for ICG into practice by clarifying the relationships between its features and applicability. Specifically, we address the obstacles encountered in the process of developing an ICG repurposing strategy, as well as the noteworthy advancements made in the field of ICG repurposing. We also go into detail about the structure-function correlations of drugs containing ICG and how different structural groups significantly affect the physicochemical properties.

Indocyanine green fluorescence imaging-assisted laparoscopy resection of retroperitoneal tumors in children: case report and literature review

This study examined the applicability of indocyanine green (ICG) fluorescence imaging to assist the laparoscopic resection of retroperitoneal tumors in pediatric patients via an abdominal approach. Conducted prospectively at the Guangzhou Women and Children's Medical Center from May to September 2023, the research included three pediatric cases, for whom laparoscopic retroperitoneal tumor resections were performed utilizing ICG fluorescence imaging. In each case, ICG was intravenously administered (0.3 mg/kg) prior to surgery, enabling the visualization of vital vascular structures through real-time fluorescence imaging. The trocar's placement was guided by a "four-hole" technique from the healthy side in a 70-degree lateral decubitus position. The operations were accomplished successfully without any complications. Pathological analysis of the patients identified one case of Wilms tumor of the embryonal type, one ganglioneuroblastoma of the mature type without N-MYC gene amplification, and one mature cystic teratoma. The findings suggest that with careful patient selection and skilled surgical execution, the utilization of ICG fluorescence imaging in the laparoscopic resection of retroperitoneal tumors is both safe and effective in children. This approach significantly improves the visualization of critical blood vessels, thus enhancing surgical safety.

Validation of retinal oximetry vessel selection using fluorescein angiography in patients with optic disc drusen

Retinal oximetry could provide insights into the pathophysiology of optic nerve disease, including optic disc drusen (ODD). Vessel selection for oximetry analysis is based on morphological characteristics of arterioles and venules and supported by an overlay of estimated blood oxygen saturations. The purpose of this cross-sectional study was to determine the validity of this vessel selection procedure by comparing it with vessel selection supported by video fluorescein angiography (FA). The study included 36 eyes of 36 patients with ODD who underwent retinal oximetry (Oxymap retinal oximeter T1) followed by FA (Heidelberg Spectralis). Two trained graders selected vessel segments in a pre-defined measurement area around the optic disc. One of these graders additionally performed the vessel segment selection with the support of FA images. When performed by the same grader, FA-supported and non-FA-supported vessel selection did not lead to significant differences in total vessel segment length, estimated oxygen saturations or vessel diameters (all p > 0.05). Inter-grader differences were found for arterial and venous segment lengths and arterial saturation (p < 0.05). A similar tendency was found for the arteriovenous saturation difference (p = 0.10). In conclusion, identifying vessel segments for retinal oximetry analysis based on vessel morphology and supported by a color-coded saturation overlay appears to be a valid method without the need for invasive angiography. A numerically small inter-grader variation may influence oximetry results. Further studies of retinal oximetry in ODD are warranted.

Real time monitoring peripheral nerve function with ICG and BDA-ICG by NIR-II fluorescence imaging

Neuroanatomical tract tracers are important for studying axoplasmic transport and the complex interconnections of the nervous system. Though traditional fluorescent tracers are widely used, they have several prominent drawbacks when imaging, including low resolutions and low tissue penetrations and inability to be supervised dynamically within a long peripheral nerve during the long term. Here, we explored the potential of ICG as a neural tracer for axoplasmic transport and for the first time demonstrated that ICG could be used to detect transport function within peripheral nerve by near-infrared region II (NIR-II) imaging. On basis of this finding, a novel bi-directional neural tracer biotinylated dextran amine-indocyanine green (BDA-ICG) was prepared and characterized with better long-term stability and higher nerve-to-background ratio than ICG in vivo, and successfully imaged the injured peripheral nerve from the healthy one within 24 h. Our results show that BDA-ICG are promising neural tracers and clinically available dyes with NIR-II emission tail characteristics as ICG.

Near-infrared fluorescence lymph node template region dissection plus backup lymphadenectomy in open radical cystectomy for bladder cancer using an innovative handheld device: A single center experience

BACKGROUND

The extent of pelvic lymphadenectomy (PLND) as part of radical cystectomy (RC) for bladder cancer (BC) remains unclear. Sentinel-based and lymphangiographic approaches could lead to reduced morbidity without sacrificing oncologic safety.

OBJECTIVE

To evaluate the feasibility and diagnostic value of fluorescence-guided template sentinel region dissection (FTD) using a handheld near-infrared fluorescence (NIRF) camera in open radical cystectomy.

DESIGN, SETTING, AND PARTICIPANTS

After peritumoral cystoscopic injection of indocyanine green (ICG) 21 patients underwent open RC with FTD due to BC between June 2019 and June 2021. Intraoperatively, the FIS-00 Hamamatsu Photonics® NIRF camera was used to identify and resect fluorescent template sentinel regions (FTRs) followed by extended pelvic lymphadenectomy (ePLND) as oncological back-up.

OUTCOME MEASUREMENT AND STATISTICAL ANALYSIS

Descriptive analysis of positive and negative results per template region.

RESULTS AND LIMITATIONS

FTRs were identified in all 21 cases. Median time (range) from ICG injection to fluorescence detection was 75 (55-125) minutes. On average (SD), 33.4 (9.6) lymph nodes were dissected per patient. Considering template regions as the basis of analysis, 67 (38.3%) of 175 resected regions were NIRF-positive, with 13 (7.4%) regions harboring lymph node metastases. We found no metastatic lymph nodes in NIRF-negative template regions. Outside the standard template, two NIRF-positive benign nodes were identified.

CONCLUSION

The concept of NIRF-guided FTD proved for this group all lymph node metastases to be found in NIRF-positive template regions. Pending validation in a larger collective, resection of approximately 40% of standard regions may be sufficient and may result in less morbidity.

Active Targeting Hyaluronan Conjugated Nanoprobe for Magnetic Particle Imaging and Near-Infrared Fluorescence Imaging of Breast Cancer and Lung Metastasis

A major contributing cause to breast cancer related death is metastasis. Moreover, breast cancer metastasis often shows little symptoms until a large area of the organs is occupied by metastatic cancer cells. Breast cancer multimodal imaging is attractive since it integrates advantages from several modalities, enabling more accurate cancer detection. Glycoprotein CD44 is overexpressed on most breast cancer cells and is the primary cell surface receptor for hyaluronan (HA). To facilitate breast cancer diagnosis, we report an indocyanine green (ICG) and HA conjugated iron oxide nanoparticle (NP-ICG-HA), which enabled active targeting to breast cancer by HA-CD44 interaction and detected metastasis with magnetic particle imaging (MPI) and near-infrared fluorescence imaging (NIR-FI). When evaluated in a transgenic breast cancer mouse model, NP-ICG-HA enabled the detection of multiple breast tumors in MPI and NIR-FI, providing more comprehensive images and a diagnosis of breast cancer. Furthermore, NP-ICG-HAs were evaluated in a lung metastasis model. Upon NP-ICG-HA administration, MPI showed clear signals in the lungs, indicating the tumor sites. This is the first time that HA-based NPs have enabled MPI of cancer. NP-ICG-HAs are an attractive platform for noninvasive detection of primary breast cancer and lung metastasis.

Fluorescence Imaging Using Deep-Red Indocyanine Blue, a Complementary Partner for Near-Infrared Indocyanine Green

Indocyanine Blue (ICB) is the deep-red pentamethine analogue of the widely used clinical near-infrared heptamethine cyanine dye Indocyanine Green (ICG). The two fluorophores have the same number of functional groups and molecular charge and vary only by a single vinylene unit in the polymethine chain, which produces a predictable difference in spectral and physicochemical properties. We find that the two dyes can be employed as a complementary pair in diverse types of fundamental and applied fluorescence imaging experiments. A fundamental fluorescence spectroscopy study used ICB and ICG to test a recently proposed Förster Resonance Energy Transfer (FRET) mechanism for enhanced fluorescence brightness in heavy water (D2O). The results support two important corollaries of the proposal: (a) the strategy of using heavy water to increase the brightness of fluorescent dyes for microscopy or imaging is most effective when the dye emission band is above 650 nm, and (b) the magnitude of the heavy water florescence enhancement effect for near-infrared ICG is substantially diminished when the ICG surface is dehydrated due to binding by albumin protein. Two applied fluorescence imaging studies demonstrated how deep-red ICB can be combined with a near-infrared fluorophore for paired agent imaging in the same living subject. One study used dual-channel mouse imaging to visualize increased blood flow in a model of inflamed tissue, and a second mouse tumor imaging study simultaneously visualized the vasculature and cancerous tissue in separate fluorescence channels. The results suggest that ICB and ICG can be incorporated within multicolor fluorescence imaging methods for perfusion imaging and hemodynamic characterization of a wide range of diseases.

Performance enhancement of diffuse fluorescence tomography based on an extended Kalman filtering-long short term memory neural network correction model

To alleviate the ill-posedness of diffuse fluorescence tomography (DFT) reconstruction and improve imaging quality and speed, a model-derived deep-learning method is proposed by combining extended Kalman filtering (EKF) with a long short term memory (LSTM) neural network, where the iterative process parameters acquired by implementing semi-iteration EKF (SEKF) served as inputs to the LSTM neural network correction model for predicting the optimal fluorescence distributions. To verify the effectiveness of the SEKF-LSTM algorithm, a series of numerical simulations, phantom and in vivo experiments are conducted, and the experimental results are quantitatively evaluated and compared with the traditional EKF algorithm. The simulation experimental results show that the proposed new algorithm can effectively improve the reconstructed image quality and reconstruction speed. Importantly, the LSTM correction model trained by the simulation data also obtains satisfactory results in the experimental data, suggesting that the SEKF-LSTM algorithm possesses strong generalization ability and great potential for practical applications.

Rotor-based image-guided therapy of glioblastoma

Glioblastoma (GBM), deep in the brain, is more challenging to diagnose and treat than other tumors. Such challenges have blocked the development of high-impact therapeutic approaches that combine reliable diagnosis with targeted therapy. Herein, effective cyanine dyes (IRLy) with the near-infrared two region (NIR-II) adsorption and aggregation-induced emission (AIE) have been developed via an "extended conjugation & molecular rotor" strategy for multimodal imaging and phototherapy of deep orthotopic GBM. IRLy was synthesized successfully through a rational molecular rotor modification with stronger penetration, higher signal-to-noise ratio, and a high photothermal conversion efficiency (PCE) up to ∼60%, which can achieve efficient NIR-II photo-response. The multifunctional nanoparticles (Tf-IRLy NPs) were further fabricated to cross the blood-brain barrier (BBB) introducing transferrin (Tf) as a targeting ligand. Tf-IRLy NPs showed high biosafety and good tumor enrichment for GBM in vitro and in vivo, and thus enabled accurate, efficient, and less invasive NIR-II multimodal imaging and photothermal therapy. This versatile Tf-IRLy nanosystem can provide a reference for the efficient, precise and low-invasive multi-synergistic brain targeted photo-theranostics. In addition, the "extended conjugation & molecular rotor" strategy can be used to guide the design of other photothermal agents.

Fluorescence imaging for real-time detection of breast cancer tumors using IV injection of indocyanine green with non-conventional imaging: a systematic review of preclinical and clinical studies of perioperative imaging technologies

BACKGROUND

This review summarizes the available data on the effectiveness of indocyanine green fluorescence imaging (ICG-FI) for real-time detection of breast cancer (BC) tumors with perioperative imaging technologies.

METHODS

PubMed and Scopus databases were exhaustively searched for publications on the use of the real-time ICG-FI evaluation of BC tumors with non-conventional breast imaging technologies.

RESULTS

Twenty-three studies were included in this review. ICG-FI has been used for BC tumor identification in 12 orthotopic animal tumor experiences, 4 studies on animal assessment, and for 7 human clinical applications. The BC tumor-to-background ratio (TBR) was 1.1-8.5 in orthotopic tumor models and 1.4-3.9 in animal experiences. The detection of primary human BC tumors varied from 40% to 100%. The mean TBR reported for human BC varied from 2.1 to 3.7. In two studies evaluating BC surgical margins, good sensitivity (93.3% and 100%) and specificity (60% and 96%) have been reported, with a negative predictive value of ICG-FI to predict margin involvement intraoperatively of 100% in one study.

CONCLUSIONS

The use of ICG-FI as a guiding tool for the real-time identification of BC tumors and for the assessment of tumor boundaries is promising. There is great variability between the studies with regard to timing and dose. Further evidence is needed to assess whether ICG-guided BC surgery may be implemented as a standard of care.

MRI-guided photothermal/photodynamic immune activation combined with PD-1 inhibitor for the multimodal combination therapy of melanoma and metastases

Non-invasive image-guided precise photothermal/photodynamic therapy (PTT/PDT) has been proven to be an effective local treatment modality but incompetent against metastases. Hence, the combination of local PTT/PDT and systemic immunotherapy would be a promising strategy for tumor eradication. Herein, a magnetic resonance imaging (MRI)-visualized PTT/PDT agent (SIDP NMs) was constructed, and the efficacy of its multimodal combination with a programmed cell death 1 (PD-1) inhibitor in the treatment of melanoma and metastases was studied. Due to the hydrophobic encapsulation of indocyanine green within the micellar core, SIDP NMs exhibited excellent photothermal/photodynamic properties and stability under an 808 nm near-infrared laser. In vitro cell experiments showed that SIDP NMs had a good killing effect. After incubating with B16-F10 cells for 24 h and irradiating with an 808-nm laser for 10 min, cell viability decreased significantly. Magnetic resonance imaging experiments in melanoma-bearing mice have shown that the dynamic distribution of SIDP NMs in tumor tissue could be monitored by T2WI and T2-MAP non-invasively due to the presence of superparamagnetic iron oxide nanocrystal in SIDP NMs. When the 808 nm laser was irradiated at the maximum focusing time point shown by MRI, the temperature of the tumor area rapidly increased from 32°C to 60.7°C in 5 min. In mouse melanoma ablation and distant tumor immunotherapy studies, SIDP NMs provided excellent MRI-guided PTT/PDT results and, when combined with PD-1 inhibitor, have great potential to cure primary tumors and eradicate metastases.

Photodynamic Therapy and Cardiovascular Diseases

Cardiovascular diseases are the third most common cause of death in the world. The most common are heart attacks and stroke. Cardiovascular diseases are a global problem monitored by many centers, including the World Health Organization (WHO). Atherosclerosis is one aspect that significantly influences the development and management of cardiovascular diseases. Photodynamic therapy (PDT) is one of the therapeutic methods used for various types of inflammatory, cancerous and non-cancer diseases. Currently, it is not practiced very often in the field of cardiology. It is most often practiced and tested experimentally under in vitro experimental conditions. In clinical practice, the use of PDT is still rare. The aim of this review was to characterize the effectiveness of PDT in the treatment of cardiovascular diseases. Additionally, the most frequently used photosensitizers in cardiology are summarized.

Perfusion Analysis Using High-Definition Indocyanine Green Angiography in Burn Comb Model

Indocyanine green angiography (ICGA) has been widely employed for quantitative evaluation of the rat comb burn model, but the imaging equipment, imaging protocol, and fluorescence data interpretation of ICGA remain unsatisfactory. This study aims to provide better solutions for the application of ICGA in perfusion analysis. The rat comb burn model was established under a series of different comb contact durations, including 10, 20, 25, 30, 35, and 40 s. Indocyanine green angiography was used to analyze wound perfusion. In total, 16 rats were divided into ibuprofen and control groups for the burn model, and their perfusion was compared. A total of 16 identical models were divided into standard- and high-dose indocyanine green (ICG) groups, and ICGA was conducted to investigate the dynamic change in wound fluorescence. Escharectomy was performed under real-time fluorescence mapping and navigation. The results showed that a comb contact duration of 30 s was optimum for the burn model. Indocyanine green angiography could accurately evaluate the histologically determined depth of thermal injury and wound perfusion in the rat comb model. Digital subtraction of residual fluorescence was necessary for multiple comparisons of perfusion. Dynamic changes in fluorescence and necrotic tissues were observed more clearly by high-dose (0.5 mg/kg) ICG in angiography. In conclusion, perfusion analysis by ICGA can be used to assess the histologically determined depth of thermal injury and the impact of a specific treatment on wound perfusion. Indocyanine green angiography can help to identify necrotic tissue. The above findings and related imaging protocols lay the foundation for future research.

Current Application of Navigation Systems in Robotic-Assisted and Laparoscopic Partial Nephrectomy: Focus on the Improvement of Surgical Performance and Outcomes

Kidney cancer represents the third most prevalent malignancy among all types of genitourinary cancer worldwide. Currently, there is a growing trend of employing partial nephrectomy for the management of large and complex tumors. Surgical outcomes are associated with some amendable surgical factors, including warm ischemic time, pedicle clamping, preserved volume of renal parenchyma, appropriate surgical strategy, and precise resection of the tumor. Improving surgical performance is pivotal for achieving favorable surgical outcomes. Due to advancements in imaging visualization technology and the shift of the medical paradigm toward precision medicine, an increasing number of navigation systems have been implemented in partial nephrectomy procedures. The navigation system can assist surgeons in formulating optimal surgical strategies and enhance the safety, precision, and feasibility of resecting complex renal tumors. In this review, we provide an overview of currently available navigation systems and their feasible applications, with a focus on how they contribute to the improvement of surgical performance and outcomes during robotic-assisted and laparoscopic partial nephrectomy.

Photoacoustic Imaging as a Novel Non-invasive Biomarker to Assess Intestinal Tissue Oxygenation and Motility in Neonatal Rats

BACKGROUND

Within the premature infant intestine, oxygenation and motility play key physiological roles in healthy development and disease such as necrotizing enterocolitis. To date, there are limited techniques to reliably assess these physiological functions that are also clinically feasible for critically ill infants. To address this clinical need, we hypothesized that photoacoustic imaging (PAI) can provide non-invasive assessment of intestinal tissue oxygenation and motility to characterize intestinal physiology and health.

METHODS

Ultrasound and photoacoustic images were acquired in 2-day and 4-day old neonatal rats. For PAI assessment of intestinal tissue oxygenation, an inspired gas challenge was performed using hypoxic, normoxic, and hyperoxic inspired oxygen (FiO2). For intestinal motility, oral administration of ICG contrast agent was used to compare control animals to an experimental model of loperamide-induced intestinal motility inhibition.

RESULTS

PAI demonstrated progressive increases in oxygen saturation (sO2) as FiO2 increased, while the pattern of oxygen localization remained relatively consistent in both 2-day and 4-day old neonatal rats. Analysis of intraluminal ICG contrast enhanced PAI images yielded a map of the motility index in control and loperamide treated rats. From PAI analysis, loperamide significantly inhibited intestinal motility, with a 32.6% decrease in intestinal motility index scores in 4-day old rats.

CONCLUSION

These data establish the feasibility and application of PAI to non-invasively and quantitatively measure intestinal tissue oxygenation and motility. This proof-of-concept study is an important first step in developing and optimizing photoacoustic imaging to provide valuable insight into intestinal health and disease to improve the care of premature infants.

Translating color fundus photography to indocyanine green angiography using deep-learning for age-related macular degeneration screening

Age-related macular degeneration (AMD) is the leading cause of central vision impairment among the elderly. Effective and accurate AMD screening tools are urgently needed. Indocyanine green angiography (ICGA) is a well-established technique for detecting chorioretinal diseases, but its invasive nature and potential risks impede its routine clinical application. Here, we innovatively developed a deep-learning model capable of generating realistic ICGA images from color fundus photography (CF) using generative adversarial networks (GANs) and evaluated its performance in AMD classification. The model was developed with 99,002 CF-ICGA pairs from a tertiary center. The quality of the generated ICGA images underwent objective evaluation using mean absolute error (MAE), peak signal-to-noise ratio (PSNR), structural similarity measures (SSIM), etc., and subjective evaluation by two experienced ophthalmologists. The model generated realistic early, mid and late-phase ICGA images, with SSIM spanned from 0.57 to 0.65. The subjective quality scores ranged from 1.46 to 2.74 on the five-point scale (1 refers to the real ICGA image quality, Kappa 0.79-0.84). Moreover, we assessed the application of translated ICGA images in AMD screening on an external dataset (n = 13887) by calculating area under the ROC curve (AUC) in classifying AMD. Combining generated ICGA with real CF images improved the accuracy of AMD classification with AUC increased from 0.93 to 0.97 (P < 0.001). These results suggested that CF-to-ICGA translation can serve as a cross-modal data augmentation method to address the data hunger often encountered in deep-learning research, and as a promising add-on for population-based AMD screening. Real-world validation is warranted before clinical usage.

Antibody-Conjugated Polymersomes with Encapsulated Indocyanine Green J-Aggregates and High Near-Infrared Absorption for Molecular Photoacoustic Cancer Imaging

Imaging plays a critical role in all stages of cancer care from early detection to diagnosis, prognosis, and therapy monitoring. Recently, photoacoustic imaging (PAI) has started to emerge into the clinical realm due to its high sensitivity and ability to penetrate tissues up to several centimeters deep. Herein, we encapsulated indocyanine green J (ICGJ) aggregate, one of the only FDA-approved organic exogenous contrast agents that absorbs in the near-infrared range, at high loadings up to ∼40% w/w within biodegradable polymersomes (ICGJ-Ps) composed of poly(lactide-co-glycolide-b-polyethylene glycol) (PLGA-b-PEG). The small Ps hydrodynamic diameter of 80 nm is advantageous for in vivo applications, while directional conjugation with epidermal growth factor receptor (EGFR) targeting cetuximab antibodies renders molecular specificity. Even when exposed to serum, the ∼11 nm-thick membrane of the Ps prevents dissociation of the encapsulated ICGJ for at least 48 h with a high ratio of ICGJ to monomeric ICG absorbances (i.e., I895/I780 ratio) of approximately 5.0 that enables generation of a strong NIR photoacoustic (PA) signal. The PA signal of polymersome-labeled breast cancer cells is proportional to the level of cellular EGFR expression, indicating the feasibility of molecular PAI with antibody-conjugated ICGJ-Ps. Furthermore, the labeled cells were successfully detected with PAI in highly turbid tissue-mimicking phantoms up to a depth of 5 mm with the PA signal proportional to the amount of cells. These data show the potential of molecular PAI with ICGJ-Ps for clinical applications such as tumor margin detection, evaluation of lymph nodes for the presence of micrometastasis, and laparoscopic imaging procedures.

Indocyanine-Green-Loaded Liposomes for Photodynamic and Photothermal Therapies: Inducing Apoptosis and Ferroptosis in Cancer Cells with Implications beyond Oral Cancer

Oral cancer represents a global health burden, necessitating novel therapeutic strategies. Photodynamic and photothermal therapies using indocyanine green (ICG) have shown promise due to their distinctive near-infrared (NIR) light absorption characteristics and FDA-approved safety profiles. This study develops ICG-loaded liposomes (Lipo-ICGs) to further explore their potential in oral cancer treatments. We synthesized and characterized the Lipo-ICGs, conducted in vitro cell culture experiments to assess cellular uptake and photodynamic/photothermal effects, and performed in vivo animal studies to evaluate their therapeutic efficacy. Quantitative cell apoptosis and gene expression variation were further characterized using flow cytometry and RNA sequencing, respectively. Lipo-ICGs demonstrated a uniform molecular weight distribution among particles. The in vitro studies showed a successful internalization of Lipo-ICGs into the cells and a significant photodynamic treatment effect. The in vivo studies confirmed the efficient delivery of Lipo-ICGs to tumor sites and successful tumor growth inhibition following photodynamic therapy. Moreover, light exposure induced a time-sensitive photothermal effect, facilitating the further release of ICG, and enhancing the treatment efficacy. RNA sequencing data showed significant changes in gene expression patterns upon Lipo-ICG treatment, suggesting the activation of apoptosis and ferroptosis pathways. The findings demonstrate the potential of Lipo-ICGs as a therapeutic tool for oral cancer management, potentially extending to other cancer types.

Membrane cholesterol enrichment and folic acid functionalization lead to increased accumulation of erythrocyte-derived optical nano-constructs within the ovarian intraperitoneal tumor implants in mice

Cytoreductive surgery remains as the gold standard to treat ovarian cancer, but with limited efficacy since not all tumors can be intraoperatively visualized for resection. We have engineered erythrocyte-derived nano-constructs that encapsulate the near infrared (NIR) fluorophore, indocyanine green (ICG), as optical probes for NIR fluorescence imaging of ovarian tumors. Herein, we have enriched the membrane of these nano-constructs with cholesterol, and functionalized their surface with folic acid (FA) to target the folate receptor-α. Using a mouse model, we show that the average fraction of the injected dose per tumor mass for nano-constructs with both membrane cholesterol enrichment and FA functionalization was ~ sixfold higher than non-encapsulated ICG, ~ twofold higher than nano-constructs enriched with cholesterol alone, and 33 % higher than nano-constructs with only FA functionalization at 24-h post-injection. These results suggest that erythrocyte-derived nano-constructs containing both cholesterol and FA present a platform for improved fluorescence imaging of ovarian tumors.

Microfluidics-Prepared Ultra-small Biomimetic Nanovesicles for Brain Tumor Targeting

Blood-brain-barrier (BBB) serves as a fatal guard of the central nervous system as well as a formidable obstacle for the treatment of brain diseases such as brain tumors. Cell membrane-derived nanomedicines are promising drug carriers to achieve BBB-penetrating and brain lesion targeting. However, the challenge of precise size control of such nanomedicines has severely limited their therapeutic effect and clinical application in brain diseases. To address this problem, this work develops a microfluidic mixing platform that enables the fabrication of cell membrane-derived nanovesicles with precise controllability and tunability in particle size and component. Sub-100 nm macrophage plasma membrane-derived vesicles as small as 51 nm (nanoscale macrophage vesicles, NMVs), with a narrow size distribution (polydispersity index, PDI: 0.27) and a high drug loading rate (up to 89% for indocyanine green-loaded NMVs, NMVs@ICG (ICG is indocyanine green)), are achieved through a one-step process. Compared to beyond-100 nm macrophage cell membrane vesicles (general macrophage vesicles, GMVs) prepared via the traditional methods, the new NMVs exhibits rapid (within 1 h post-injection) and enhanced orthotopic glioma targeting (up to 78% enhancement), with no extra surface modification. This work demonstrates the great potential of such real-nanoscale cell membrane-derived nanomedicines in targeted brain tumor theranostics.

Nano-induced endothelial leakiness-reversing nanoparticles for targeting, penetration and restoration of endothelial cell barrier

Nano-induced endothelial leakiness (NanoEL) can improve the ability of nanoparticles (NPs) to enter the tumor environment, nevertheless, it can inadvertently trigger adverse effects such as tumor metastasis. To overcome these concerns, it becomes important to develop a NPs design strategy that capitalizes on the NanoEL effect while averting unwanted side effects during the drug delivery process. Herein, we introduce the PLGA-ICG-PEI-Ang1@M NP which has a core comprising poly (lactic-co-glycolic acid) (PLGA) and the inner shell with a highly positively charged polyethyleneimine (PEI) and the anti-permeability growth factor Angiopoietin 1 (Ang1), while the outer shell is camouflaged with a Jurkat cell membrane. During the drug delivery process, our NPs exhibit their capability to selectively target and penetrate endothelial cell layers. Once the NPs penetrate the endothelial layer, the proton sponge effect triggered by PEI in the acidic environment surrounding the tumor site can rupture the cell membrane on the NPs' surface. This rupture, in turn, enables the positively charged Ang1 to be released due to the electrostatic repulsion from PEI and the disrupted endothelial layer can be restored. Consequently, the designed NPs can penetrate endothelial layers, promote the cell layer recovery, restrict the tumor metastasis, and facilitate efficient cancer therapy. STATEMENT OF SIGNIFICANCE.

Current status of indocyanine green fluorescent angiography in assessing perfusion of gastric conduit and oesophago-gastric anastomosis

Anastomotic leak (AL) remains a significant complication after esophagectomy. Indocyanine green fluorescent angiography (ICG-FA) is a promising and safe technique for assessing gastric conduit (GC) perfusion intraoperatively. It provides detailed visualization of tissue perfusion and has demonstrated usefulness in oesophageal surgery. GC perfusion analysis by ICG-FA is crucial in constructing the conduit and selecting the anastomotic site and enables surgeons to make necessary adjustments during surgery to potentially reduce ALs. However, anastomotic integrity involves multiple factors, and ICG-FA must be combined with optimization of patient and procedural factors to decrease AL rates. This review summarizes ICG-FA's current applications in assessing esophago-gastric anastomosis perfusion, including qualitative and quantitative analysis and different imaging systems. It also explores how fluorescent imaging could decrease ALs and aid clinicians in utilizing ICG-FA to improve esophagectomy outcomes.

Preliminary exploration of hepatic parenchymal near-infrared fluorescence imaging technique via retrograde biliary approach: a feasibility study (with video)

This paper explores the feasibility and principle of hepatic parenteral fluorescence imaging technology after retrograde injection of indocyanine green (ICG) through endoscopic nasobiliary drainage (ENBD). The data were collected from 53 patients with cholecystolithiasis and choledocholithiasis, from October 2022 to March 2023, diagnosed by fluorescence imaging technique retrograde biliary approach (FIT-RB). We divided the patients into two groups according to the features of liver parenchyma, the poor group (n = 34, including scattered or no imaging) and the good group (n = 19, regular uniform imaging). We compared and analyzed the perioperative results of the two groups and explored the influencing factors of the success of FIT-RB and the ICG concentration suitable for this imaging technique. The good imaging rate of the 53 enrolled cases was 35.8%. The bilirubin level before ENBD and laparoscopic cholecystectomy in the poor group was significantly higher than that in the good group (P < 0.001). The proportion of higher ICG concentrations (0.5 mg/mL) was significantly higher in the good group (P = 0.028). Our results demonstrated that the success rate of good imaging was 4.53 times higher than that of low-dose ICG (0.125 or 0.25 mg/L) cases at 0.5 mg/ml of ICG. The level of total bilirubin and direct bilirubin were negatively correlated with the imaging effect, and total bilirubin and direct bilirubin levels were important predictors of the efficacy of FIT-RB. FIT-RB is safe and feasible in patients with low site bilirubin levels. An ICG concentration of 0.5 mg/ml may be ideal for implementing this technique.

[ICG angiography is a safety standard in bariatric surgery]

OBJECTIVE

To examine the specific characteristics of ICG-angiography during various bariatric interventions.

MATERIAL AND METHODS

The study included 329 patients, with 105 (32%) undergoing sleeve gastrectomy (LSG), 98 (30%) undergoing mini-gastricbypass (MGB), 126 (38%) undergoing Roux-en-Y gastric bypass (RGB). Intraoperative ICG angiography was perfomed on all patients at 'control points', the perfusion of the gastric stump was qualitatively and quantitatively assessed.

RESULTS

Intraoperative ICG angiography shows that during LSG the angioarchitectonics in the area of the His angle are crucial. The presence of the posterior gastric artery of the gastric main type is a prognostically unfavorable risk factor for the development of ischemic complications. Therefore, to expand the gastric stump it is necessary to suture a 40Fr nasogastric tube and perform peritonization of the staple line. Statistical difference in blood supply at three points were found between and within the two groups of patients (Gis angle area, gastric body, pyloric region) with a p-value <0.001. During MGB, one of the important stages is applying the first (transverse) stapler cassette between the branches of the right and left gastric arteries. This maintains blood supply in anastomosis area, preventing immediate complications such as GEA failure, as well as long-term complications like atrophic gastritis, peptic ulcers, and GEA stenosis.

CONCLUSION

ICG angiography is a useful method for intraoperative assessment of angioarchitecture and perfusion of the gastric stump during bariatric surgery. This helps prevent tissue ischemia and reduce the risk of early and late postoperative complications.

[Implementation of fluorescent imaging technology in endovideosurgical treatment of colorectal endometriosis]

The article includes a clinical case of a patient with deep infiltrating endometriosis with rectum involving and using intraoperative controlled fluorescence in order to increase the radicality of surgery and improve the prognosis of the disease. Surgical excision of the endometrioitic nodules is the only effective way of treating patients with colorectal endometriosis in terms of relieving pain, improving quality of life and restoring reproductive function. The possible types of surgical interventions can be performed: endometrioid lesion shaving, discoid or circular intestinal resection with anastomosis. The extent of the operation is determined by the following morphological parameters: the number of endometrioid infiltrates of the intestinal wall, the size of each of them, the degree of involvement of the intestine circumference, the depth of the intestinal wall lesion, the distance from the level of anus to the endometriotic nodule and lymphatic dissemination.

[Intraoperative near-infrared fluorescence imaging of peripheral lung tumors]

The main objective of surgical intervention in lung cancer is the radical removal of the entire tumor with the maximum possible preservation of healthy tissue. Although the area of the tumor lesion is known by the results of preoperative studies, it can be difficult to use this information to establish the exact boundaries of resection during surgery, especially with small sizes of the lump and when using minimally invasive approaches. There are several techniques to solve this problem. One of the latter is intraoperative fluorescence imaging in the infrared range, which makes it possible to detect a tumor not only with greater contrast than it can be done in white light, but also with its deep location. This review is devoted to the discussion of various aspects of this approach related to molecular imaging methods. The current situation based on the use of green indocyanine green, available for clinical use as a fluorescent agent is considered, the issues of using new targeted drugs are examined, as well as the possibility of increasing the depth of probing and combining with related treatment methods, which should contribute to a more radical operation and reduce the likelihood of local relapses.

Use of Ag-Au-ICG to increase fluorescence image of human hepatocellular carcinoma cell lines

Indocyanine green (ICG) is effective for a variety of applications including liver tumour imaging and operates in the near-infrared window. Agents for near-infrared imaging are, however, still in clinical development. The present study aimed to prepare and investigate fluorescence emission properties of ICG in combination with Ag-Au in order to enhance their specific interactions with human hepatocellular carcinoma cell lines (HepG-2). The Ag-Au-ICG complex was prepared via physical adsorption, and hence evaluated for fluorescence spectra using a spectrophotometer. Ag-Au-ICG at an optimised dosage (Ag-Au:ICG = 0.0147:1 molar ratio) in Intralipid medium was added to HepG-2 to observe the maximum fluorescence signal intensity, which further enhanced HepG-2 contrast fluorescence. Ag-Au-ICG served as a fluorescence enhancer bound onto the liposome membrane, whilst free Ag, Au, and pure ICG induced low levels of cytotoxicity in HepG-2 and a normal human cell line. Thus, our findings provided new insights for the liver cancer imaging.HighlightsConcentration-dependent fluorescence peaking in the near-infrared window revealed ICG aggregation in Ag-Au molecules.Ag-Au-ICG fluorescence intensity depended strongly on the environmental media.Human hepatocellular carcinoma cell lines treated with Ag-Au-ICG in Intralipid enhanced the contrast of fluorescence microscopy images by decreasing the level of scattering in the cell lines with the contrast values being approximately five times those observed in pure ICG in Intralipid.

Advances of nanoparticle-mediated diagnostic and theranostic strategies for atherosclerosis

Atherosclerotic plaque remains the primary cause of morbidity and mortality worldwide. Accurate assessment of the degree of atherosclerotic plaque is critical for predicting the risk of atherosclerotic plaque and monitoring the results after intervention. Compared with traditional technology, the imaging technologies of nanoparticles have distinct advantages and great development prospects in the identification and characterization of vulnerable atherosclerotic plaque. Here, we systematically summarize the latest advances of targeted nanoparticle approaches in the diagnosis of atherosclerotic plaque, including multimodal imaging, fluorescence imaging, photoacoustic imaging, exosome diagnosis, and highlighted the theranostic progress as a new therapeutic strategy. Finally, we discuss the major challenges that need to be addressed for future development and clinical transformation.

Hyperfluorescence of choroidal arteries in the peripheral fundus on late-phase ICGA

AIMS

To correlate the hyperfluorescent lines in the peripheral fundus on late-phase indocyanine green angiography (ICGA) to infrared and optical coherence tomography (OCT) findings.

METHODS

This is a retrospective, cross-sectional study. Multimodal imaging data, including ICGA, fluorescein angiography, infrared imaging, and OCT were analyzed. The hyperfluorescent lines were categorized into 2 grades according to their extents. In addition, serum levels of apolipoprotein (Apo) A and B were measured by enzyme linked immunosorbent assay.

RESULTS

A total of 247 patients who underwent multimodal imaging were reviewed. The hyperfluorescent lines in the peripheral fundus on late-phase ICGA were detected in 96 patients, and were correlated to superficial choroidal arteries by infrared imaging and OCT. The incidence of hyperfluorescent choroidal arteries in the peripheral fundus (HCAP) on late-phase ICGA increased in groups of older ages (0-20 years, 4.3%; 20-40 years, 2.6%; 40-60 years, 48.9%; >60 years, 88.7%; p < 0.001). In addition, the mean age increased with the grades of HCAP (grade 1, 52.3 ± 10.8 years; grade 2, 63.3 ± 10.5 years; p < 0.001). The hyperfluorescence was also detected in posterior choroidal arteries in 11 eyes, all patients in grade 2. There was no significant correlation between grades of HCAP and gender, or serum level of ApoA and ApoB.

CONCLUSION

The occurrence and grades of HCAP increased with age. The superficial location of choroidal arteries in the peripheral fundus exposes their hyperfluorescence on late-phase ICGA. HCAP might reveal the local lipid degeneration of choroidal artery walls, according to ICG binding properties.

Evaluation of testicular blood flow during testicular torsion surgery in children using the indocyanine green-guided near-infrared fluorescence imaging technique

Objective

This study investigates the feasibility of the indocyanine green-guided near-infrared fluorescence (ICG-NIRF) imaging technique in evaluating testicular blood flow during testicular torsion (TT) surgery in pediatric cases.

Methods

We retrospectively analyzed the eight pediatric patients with TT who underwent surgery in our hospital between February and July 2023. The intraoperative two-step method of ICG-NIRF imaging and testicular incision was used to evaluate the testicular blood flow, followed by a selection of different surgical methods. The removed testes were pathologically examined after surgery, and all patients were followed up 1 month after surgery to evaluate testicular blood flow using gray-scale ultrasound and color Doppler flow imaging (CDFI).

Results

Eight pediatric TT patients aged 1-16 years, with a median age of 11.5 years, were enrolled. Time from the onset ranged from 4 to 72 h (mean 26.13 ± 25.09 h). A total of eight testes were twisted, including four on the left side and four on the right side. The twisting direction of the testes was clockwise in four cases and counterclockwise in four cases. The rotation of torsion was 180°-1,080° (mean 472.5° ± 396°). There was no statistically significant difference in the imaging time between the four patients with testicular blood vessel imaging on both the torsional and normal sides (P > 0.05). The postoperative recovery was uneventful, with no complications during the follow-up period of 1 month. The postoperative histopathological results of three patients who underwent orchiectomy showed extensive hemorrhage, degeneration, and necrosis of the testicular tissue. Among the five patients who underwent orchiopexy, a gray-scale ultrasound and CDFI examinations showed uniform internal echo of the testes and normal blood flow signals in four patients. One patient with no testicular blood vessel imaging on the torsional side showed uneven internal echo of the testis and no blood flow signals.

Conclusion

ICG-NIRF imaging is a feasible method to evaluate testicular blood flow during TT surgery. Testicular blood vessel imaging within 5 minutes after ICG injection might be the basis for testicular retention during TT surgery.

Near infrared conjugated polymer nanoparticles (CPN™) for tracking cells using fluorescence and optoacoustic imaging

Tracking the biodistribution of cell therapies is crucial for understanding their safety and efficacy. Optical imaging techniques are particularly useful for tracking cells due to their clinical translatability and potential for intra-operative use to validate cell delivery. However, there is a lack of appropriate optical probes for cell tracking. The only FDA-approved material for clinical use is indocyanine green (ICG). ICG can be used for both fluorescence and photoacoustic imaging, but is prone to photodegradation, and at higher concentrations, undergoes quenching and can adversely affect cell health. We have developed novel near-infrared imaging probes comprising conjugated polymer nanoparticles (CPNs™) that can be fine-tuned to absorb and emit light at specific wavelengths. To compare the performance of the CPNs™ with ICG for in vivo cell tracking, labelled mesenchymal stromal cells (MSCs) were injected subcutaneously in mice and detected using fluorescence imaging (FI) and a form of photoacoustic imaging called multispectral optoacoustic tomography (MSOT). MSCs labelled with either ICG or CPN™ 770 could be detected with FI, but only CPN™ 770-labelled MSCs could be detected with MSOT. These results show that CPNs™ show great promise for tracking cells in vivo using optical imaging techniques, and for some applications, out-perform ICG.

Semi-Permanent Use of Indocyanine Green Latex Phantom for Fluorescence Emission

INTRODUCTION

Testing the fluorescence emission of the vascular circulation status of the indocyanine green (ICG) fluorescence contrast agent to validate the system performance is crucial. Hence, the development of an ICG phantom is imperative, and this study proposes a method for manufacturing an ICG phantom.

METHOD

The ICG with an initial concentration was subjected to 0.2 cc sampling through syringe(x), and an ICG (0.2 cc) is diluted with silicon (Si) latex lubber (10 mL) during the manufactured the phantom. The brightest fluorescence expression state is 30 μM, and if it exceeded 50 μM, fluorescence fading occurred and changed to a dark color.

RESULTS

The liquid (ICG) of the concentration range is 0.003 mM to 0.24 mM, and the maximum fluorescence expression range is 0.005 to 0.006 mM when the phantom is irradiated using a 780-nm (800 mW) LED. In addition, the fluorescence emission is reduced to 0.24 mM, and the fluorescence expression concentration is 10 μM, 30 μM, and 50 μM, respectively. The decreasing of the fluorescence emission is beginning to 50 μM.

CONCLUSIONS

In this study, the proposed phantom with ICG fluorescence emission using latex lubber is proposed. In this works, the proposed phantom is improved the performance for ICG fluorescence emission. In the manufactured phantom, the phantom is used for gelatin, and the advance of phantom has easy manufacturing and long-life fluorescence emission (semipermanent) due to incorrodible material (latex lubber). To experimental results of a phantom, the ICG fluorescent contrast medium (0.055 mM) is same to 30 μM. Then, the 0.055 mM and 30 μM have high resolution and fluorescence emission status. Thus, the results are in good agreement.

Enhanced stability and photothermal efficiency of Indocyanine Green J-aggregates by nanoformulation with Calix[4]arene for photothermal therapy of cancers

Photothermal therapy (PTT) is a method of growing attention, owing to its controllable process, high efficiency and minimal side effect. Indocyanine Green (ICG) is as Food and Drug Administration (FDA) approved agent that stands on the frontline of further developments of PTT toward clinics. However, the applicability of ICG-mediated PTT is limited by the rapid in vivo clearance and photo-degradation of ICG. To improve those parameters, nanosized ICG-loaded nanoparticles (ICG-J/CX) were fabricated in this study by co-assembly of anionic ICG J-aggregates (ICG-J) with cationic tetraguanidinium calix[4]arene (CX). This very simple approach produces ICG-J/CX with a well-defined nanometer range size and a close to neutral charge. The nanoparticles demonstrate high photothermal conversion efficiency (PCE) and dramatically improved photostability, as compared with ICG. The in vitro cellular uptake and cytotoxicity studies further demonstrated that the ICG-J/CX nanoparticles enhance uptake and photothermal efficiency in comparison with ICG or non-formulated ICG-J, overall demonstrating that ICG-J/CX mediated photothermal therapy have significant potential for attaining cancer treatment.

Superior Hypophyseal Artery Intraoperative Indocyanine Green Angiogram as a Predictor of Postoperative Visual Function After Endoscopic Endonasal Surgery

BACKGROUND AND OBJECTIVES

To date, there are no tools to intraoperatively predict postoperative visual function after endoscopic endonasal surgery (EES) for suprasellar lesions. The objective of this study was to retrospectively evaluate the utility of indocyanine green (ICG) angiography as an intraoperative tool to measure optic chiasm perfusion and determine its relationship with postoperative visual function.

METHODS

Videos of patients undergoing EES for resection of suprasellar lesions were reviewed, where 5 mg of ICG was diluted in 10 mL of saline and administered. Time between luminescence of the anterior cerebral artery and the superior hypophyseal artery branches supplying the optic chiasm was noted, and the percentage of optic chiasm vessels that luminesced was recorded. Postoperative examinations and imaging studies were used to assess visual function. Patients with and without new deficits were compared with examination of trends in ICG findings.

RESULTS

A total of 7 trials were reviewed on 6 patients, with no complications occurring from ICG administration. Mean time to chiasm peak luminescence was 3.8 seconds, and 81.8% of chiasm vessels luminesced. Patients with stable or improved vision after resection demonstrated over 90% chiasm luminescence in every case, and mean chiasm time in these postresection ICG administrations was 4.0 seconds. One patient experienced new postoperative visual deficits; on review of their ICG administration, 11.5% of chiasm vessels luminesced, and the chiasm itself failed to display robust luminescence after 30 seconds of direct observation.

CONCLUSION

This pilot study showed the capability of intraoperative ICG angiography to demonstrate perfusion of the optic chiasm during EES for resection of suprasellar lesions. While larger studies are required, preliminary results suggest chiasm times under 5 seconds and over 90% chiasm vessel illumination may reflect adequate chiasm perfusion, while those with delayed or absent chiasm luminescence may have compromised chiasm perfusion.

Near-infrared photodynamic and photothermal co-therapy based on organic small molecular dyes

Near-infrared (NIR) organic small molecule dyes (OSMDs) are effective photothermal agents for photothermal therapy (PTT) due to their advantages of low cost and toxicity, good biodegradation, and strong NIR absorption over a wide wavelength range. Nevertheless, OSMDs have limited applicability in PTT due to their low photothermal conversion efficiency and inadequate destruction of tumor regions that are nonirradiated by NIR light. However, they can also act as photosensitizers (PSs) to produce reactive oxygen species (ROS), which can be further eradicated by using ROS-related therapies to address the above limitations of PTT. In this review, the synergistic mechanism, composition, and properties of photodynamic therapy (PDT)-PTT nanoplatforms were comprehensively discussed. In addition, some specific strategies for further improving the combined PTT and PDT based on OSMDs for cancer to completely eradicate cancer cells were outlined. These strategies include performing image-guided co-therapy, enhancing tumor infiltration, increasing H2O2 or O2 in the tumor microenvironment, and loading anticancer drugs onto nanoplatforms to enable combined therapy with phototherapy and chemotherapy. Meanwhile, the intriguing prospects and challenges of this treatment modality were also summarized with a focus on the future trends of its clinical application.

ICG-mediated fluorescence-assisted debridement to promote wound healing

The purpose of this study was to examine the efficacy of ICG-mediated fluorescence molecular imaging (FMI) in debridement of necrotic tissue. 96 wound-infected rats were randomly divided into control group, ICG group, excitation light (EL)group and FMI group for debridement of necrotic tissue (n = 24). (I) Control group: only debridement; (II) ICG group: ICG injection before debridement; (III) EL group: Debridement under EL; (IV) FMI group: Debridement guided by ICG-mediated FMI. On the 3rd, 6th, and 9th days, the wound tissues of the rats in each group were collected for histological examination, and the levels of serum interleukin-4 (IL-4) and interferon-γ (INF-γ) were analyzed. The wound healing rate, wound score and body weight of the rats in each group were followed up until the wound healed. The results showed that the infected wounds of the rats in the FMI group had significant fluorescence development. The level of serum IL-4 in the FMI group was higher than that in the other three groups on the 6th day (p<0.01), while the level of INF-γ was lower than that in the other three groups on the 6th and 9th day (p<0.05). The results of dynamic wound tissue H&E staining indicated that the wound healing in the FMI group was better than the other three groups. The in vivo follow-up results showed that the wound healing rate and wound score of the FMI group were better than the other three groups, and the growth of rats had no difference with the other groups. ICG-mediated FMI can achieve accurate imaging of necrotic tissue for debridement, and so can accelerate wound healing, which has good clinical application prospects.

Investigation of optimizing indocyanine green solution for in vivo lymphatic research using near-infrared fluorescence indocyanine green lymphangiography

Despite the tireless efforts of many researchers in lymphatic research, indocyanine green (ICG) solution conditions suitable for lymphatic circulation tests have not been perfectly established yet. We aimed to investigate the optimal in vivo conditions of ICG solution to avoid photobleaching and quenching effects, which may affect the accuracy of lymphatic circulation evaluation. After ICG fluorescence intensity (or ICG intensity) was assessed under different in vitro conditions, the image quality of brachial lymph nodes (LNs) and collecting lymphatic vessels (LVs) in eight rats was investigated. The in vitro results showed that ICG intensity depends on concentration and time in various solvents; however, the brightest intensity was observed at a concentration of 8-30 μg/mL in all solvents. ICG concentration in the albumin (bovine serum albumin; BSA) solution and rat's plasma showed more than two times higher fluorescence intensity than in distilled water (DW) in the same range. However, saline reduced the intensity by almost half compared to DW. In the in vivo experiment, we obtained relatively high-quality images of the LNs and LVs using ICG in the BSA solution. Even at low concentrations, the result in the BSA solution was comparable to those obtained from high-concentration solutions commonly used in conventional circulation tests. This study provides valuable information about the conditions for optimal ICG intensity in near infrared fluorescence indocyanine green (NIRF-ICG) lymphangiography, which may be useful not only for the diagnosis of lymphatic circulation diseases such as lymphedema but also for preclinical research for the lymphatic system.

Flap perfusion assessment with indocyanine green angiography in deep inferior epigastric perforator flap breast reconstruction: A systematic review and meta-analysis

BACKGROUND

Indocyanine green angiography (ICG-A) has been widely applied for intraoperative flap assessment in DIEP flap breast reconstruction. However, the beneficial effect of ICG-A in DIEP flap breast reconstruction is still uncertain and no standardized protocol is available. This study aims to analyze the clinical outcome and comprehensively review protocols of this field.

METHODS

A systematic review was conducted in MEDLINE, EMBASE, and Cochrane CENTRAL databases until September 15, 2022. Studies on the utility of intraoperative ICG-A in DIEP breast reconstruction were included. Data reporting reconstruction outcomes were extracted for pooled analysis.

RESULTS

A total of 22 studies were enrolled in the review, among five studies with 1021 patients included in the meta-analysis. The protocols of ICG-A assessment of DIEP flap varied among studies. According to the pooled results, the incidence of postoperative fat necrosis was 10.89% (50 of 459 patients) with ICG-A and 21.53% (121 of 562 patients) with clinical judgment. The risk for postoperative fat necrosis was significantly lower in patients with intraoperative ICG-A than without (RR 0.47 95% CI 0.29-0.78, p = .004, I2  = 51%). Reoperation occurred in 5 of 48 patients (10.42%) in the ICG-A group and in 21 of 64 patients (32.82%) in the control group summarized from reports in two studies. The risk for reoperation was lower in the ICG-A group than in the control group (RR 0.41 95% CI 0.18-0.93, p = .03, I2  = 0%). Other complications, including flap loss, seroma, hematoma, dehiscence, mastectomy skin necrosis, and infection, were comparable between the two groups. Heterogeneities among studies were acceptable. No significant influence of specific studies was identified in sensitivity analysis.

CONCLUSIONS

ICG-A is an accurate and reliable way to identify problematic perfusion of DIEP flaps during breast reconstruction. Protocols of ICG-A differed in current studies. Intraoperative ICG-A significantly decreases the rate of fat necrosis and reoperation in patients undergoing DIEP breast reconstruction. The synthesized results should be interpreted sensibly due to the sample size limitation. RCTs on the outcomes and high-quality studies for an optimized ICG-A protocol are still needed in the future.

Assessment of jejunal interposition perfusion using indocyanine green

INTRODUCTION

Jejunal interposition (JI) is an option for oesophageal replacement in children; ensuring good graft perfusion is essential. We report three cases where Indocyanine Green (ICG) with Near-Infrared Fluorescence (NIRF) was used to assess perfusion during graft selection, passage into the chest and anastomotic assessment. This extra assessment may reduce risk of anastomotic leak and/or stricture.

METHODS

We describe the technique and salient features of all patients who have undergone ICG/NIRF-assisted JI in our centre. Patient demographics, indications for surgery, intra-operative plan, video of NIR perfusion assessment, complications and outcomes were reviewed.

RESULTS

ICG/NIRF was used in three patients (2M:1F) at a dose of 0.2 mg/kg. ICG/NIRF imaging helped select the jejunal graft and confirmed perfusion after division of segmental arteries. Perfusion was assessed before and after passing the graft through the diaphragmatic hiatus and before and after making the oesophago-jejunal anastomosis. Intrathoracic assessment at the end of the procedure confirmed good perfusion of mesentery and intrathoracic bowel. In two patients, the reassurance contributed to successful procedures. In the third patient, graft selection was satisfactory, but borderline perfusion on clinical assessment after passing the graft to the chest, confirmed by ICG/NIRF meant the graft was abandoned.

CONCLUSIONS

ICG/NIRF imaging was feasible and augmented our subjective assessment of graft perfusion, giving greater confidence during graft preparation, movement, and anastomosis. In addition, the imaging helped us abandon one graft. This series demonstrates the feasibility and benefit of ICG/NIR use in JI surgery. Further studies are required to optimise ICG use in this setting.

Use of Near-Infrared Fluorescence Techniques in Minimally Invasive Surgery for Colorectal Liver Metastases

Colorectal liver metastases (CRLM) afflict a significant proportion of patients with colorectal cancer (CRC), ranging from 25% to 30% of patients throughout the course of the disease. In recent years, there has been a surge of interest in the application of near-infrared fluorescence (NIRF) imaging as an intraoperative imaging technique for liver surgery. The utilisation of NIRF-guided liver surgery, facilitated by the administration of fluorescent dye indocyanine green (ICG), has gained traction in numerous medical institutions worldwide. This innovative approach aims to enhance lesion differentiation and provide valuable guidance for surgical margins. The use of ICG, particularly in minimally invasive surgery, has the potential to improve lesion detection rates, increase the likelihood of achieving R0 resection, and enable anatomically guided resections. However, it is important to acknowledge the limitations of ICG, such as its low specificity. Consequently, there has been a growing demand for the development of tumour-specific fluorescent probes and the advancement of camera systems, which are expected to address these concerns and further refine the accuracy and reliability of intraoperative fluorescence imaging in liver surgery. While NIRF imaging has been extensively studied in patients with CRLM, it is worth noting that a significant proportion of published research has predominantly focused on the detection of hepatocellular carcinoma (HCC). In this study, we present a comprehensive literature review of the existing literature pertaining to intraoperative fluorescence imaging in minimally invasive surgery for CRLM. Moreover, our analysis places specific emphasis on the techniques employed in liver resection using ICG, with a focus on tumour detection in minimal invasive surgery (MIS). Additionally, we delve into recent developments in this field and offer insights into future perspectives for further advancements.

Hyperthermia-triggered biomimetic bubble nanomachines

Nanoparticle-based drug delivery systems have gained much attention in the treatment of various malignant tumors during the past decades. However, limited tumor penetration of nanodrugs remains a significant hurdle for effective tumor therapy due to the existing biological barriers of tumoral microenvironment. Inspired by bubble machines, here we report the successful fabrication of biomimetic nanodevices capable of in-situ secreting cell-membrane-derived nanovesicles with smaller sizes under near infrared (NIR) laser irradiation for synergistic photothermal/photodynamic therapy. Porous Au nanocages (AuNC) are loaded with phase transitable perfluorohexane (PFO) and hemoglobin (Hb), followed by oxygen pre-saturation and indocyanine green (ICG) anchored 4T1 tumor cell membrane camouflage. Upon slight laser treatment, the loaded PFO undergoes phase transition due to surface plasmon resonance effect produced by AuNC framework, thus inducing the budding of outer cell membrane coating into small-scale nanovesicles based on the pore size of AuNC. Therefore, the hyperthermia-triggered generation of nanovesicles with smaller size, sufficient oxygen supply and anchored ICG results in enhanced tumor penetration for further self-sufficient oxygen-augmented photodynamic therapy and photothermal therapy. The as-developed biomimetic bubble nanomachines with temperature responsiveness show great promise as a potential nanoplatform for cancer treatment.

Photoacoustic Imaging as a Novel Non-Invasive Biomarker to Assess Intestinal Tissue Oxygenation and Motility in Neonatal Rats

Background

Within the premature infant intestine, oxygenation and motility play key physiological roles in healthy development and disease such as necrotizing enterocolitis. To date, there are limited techniques to reliably assess these physiological functions that are also clinically feasible for critically ill infants. To address this clinical need, we hypothesized that photoacoustic imaging (PAI) can provide non-invasive assessment of intestinal tissue oxygenation and motility to characterize intestinal physiology and health.

Methods

Ultrasound and photoacoustic images were acquired in 2-day and 4-day old neonatal rats. For PAI assessment of intestinal tissue oxygenation, an inspired gas challenge was performed using hypoxic, normoxic, and hyperoxic inspired oxygen (FiO2). For intestinal motility, oral administration of ICG contrast agent was used to compare control animals to an experimental model of loperamide-induced intestinal motility inhibition.

Results

PAI demonstrated progressive increases in oxygen saturation (sO2) as FiO2 increased, while the pattern of oxygen localization remained relatively consistent in both 2-day and 4-day old neonatal rats. Analysis of intraluminal ICG contrast enhanced PAI images yielded a map of the motility index in control and loperamide treated rats. From PAI analysis, loperamide significantly inhibited intestinal motility, with a 32.6% decrease in intestinal motility index scores in 4-day old rats.

Conclusion

These data establish the feasibility and application of PAI to non-invasively and quantitatively measure intestinal tissue oxygenation and motility. This proof-of-concept study is an important first step in developing and optimizing photoacoustic imaging to provide valuable insight into intestinal health and disease to improve the care of premature infants.

Highlights

Intestinal tissue oxygenation and intestinal motility are important biomarkers of intestinal physiology in health and disease of premature infants.This proof-of-concept preclinical rat study is the first to report application of photoacoustic imaging for the neonatal intestine.Photoacoustic imaging is demonstrated as a promising non-invasive diagnostic imaging method for quantifying intestinal tissue oxygenation and intestinal motility in premature infants.

Graphical abstract