Indocyanine Green Concentration Research Articles

Abstract WP267: The Impact of Anesthetic Agents on Regional Cerebral Blood Flow During Carotid Artery Clamping in Patients With Debranching Thoracic Endovascular Aortic Repair and Carotid Endarterectomy

Background: Carotid endarterectomy (CEA) and debranching thoracic endovascular aortic repair (debranching TEVAR) would lead to the reduction of cerebral blood flow (CBF) during carotid artery clamping. Intravenous anesthetics decrease CBF more than volatile anesthetics and may exacerbate cerebral hypoperfusion during carotid artery clamping. We have developed an innovative quantitative measure of regional cerebral blood flow (rCBF) that can be performed at the bedside using near-infrared spectroscopy (NIRS). Using this technique, we measured rCBF during CEA and TEVAR to determine the optimal anesthetic for carotid artery clamping. Methods: Patients undergoing debranching TEVAR and CEA were enrolled. We used NIRS and intravenous injection of Indocyanine green (ICG) to measure rCBF before carotid artery clamping, 10 minutes after clamping, and after de-clamping. The rCBF was calculated by Fick’s principle, using the maximum gradient model that combines the peak values and change in arterial blood concentration of ICG in the brain tissue. We evaluated the effects of each anesthetic (intravenous and volatile) on the rCBF of the cross-clamp side of the carotid artery. Results: The results of the intermediate analysis are shown below. Thirty-two patients who underwent debranching TEVAR and twenty-six who underwent CEA were enrolled. In patients who underwent debranching TEVAR, the rCBF increased from 48.4 to 53.5 ml/min/100g in patients anesthetized with volatile anesthetics and decreased from 55.1 to 32.8 ml/min/100g in patients anesthetized with intravenous anesthetics, as shown in the Figure. There was a significant difference between both anesthetics (p=0.034) but no significant difference between both anesthetics with CEA (p=0.93). Conclusion: In patients undergoing debranching TEVAR, volatile anesthetics may be preferable to intravenous anesthetics during carotid clamping.

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.

Real-time fluorescence-guided adhesiolysis with indocyanine green in intra-abdominal surgery (with video)

Intra-abdominal adhesions have consistently posed a challenge for surgeons during procedures. This study aims to investigate the feasibility of utilizing indocyanine green (ICG) in conjunction with near-infrared imaging for the detection of intra-abdominal adhesions. In vitro, we analyzed factors affecting ICG fluorescence. We divided SD rats into groups to study ICG excretion in different digestive tract regions. Additionally, we reviewed surgical videos from previous cholecystectomy cases, categorizing them by ICG injection timing and assessing fluorescence imaging in various digestive tract regions. Finally, we preoperatively injected ICG into two cholecystectomized patients with abdominal adhesions, guiding intraoperative adhesiolysis with near-infrared fluorescence imaging. In vitro, we observed a significant influence of protein and ICG concentrations on ICG fluorescence intensity. Our rat experiments unveiled a strong and highly significant correlation (Kendall’s tau-b = 1, P < 0.001) between the timing of ICG injection and the farthest point of intestinal fluorescence. A retrospective case analysis further validated this finding (Kendall’s tau-b = 0.967, P < 0.001). Under the guidance of fluorescence navigation, two cholecystectomized patients with intra-abdominal adhesions successfully underwent adhesiolysis, and no postoperative complications occurred. The intraoperative combination of ICG with near-infrared fluorescence imaging effectively enhances the visibility of the liver, bile ducts, and various segments of the gastrointestinal tract while providing real-time navigation. This real-time fluorescence guidance has the potential to aid surgeons in the dissection of intra-abdominal adhesions.

Appropriate concentration setting for the intraoperative administration of indocyanine green for fluorescence imaging to identify the sentinel lymph node in early gastric cancer: a clinical pilot study.

Some prospective trials have demonstrated the feasibility of sentinel node (SN) biopsy in gastric cancer (GC) surgery. This study aimed to identify the appropriate concentration settings for the intraoperative injection of indocyanine green (ICG) for SN biopsy. Before the clinical studies, porcine model experiments explored the optimal concentration of ICG injected intraoperatively. Next, nine GC patients were enrolled in the clinical research. ICG (0.5ml) was injected intraoperatively into four quadrants of the submucosa around the tumor at various concentrations (0.5, 0.25, and 0.1mg/ml). The lymphatic basin dissection method was applied to the ICG-positive lymphatic areas. The number and location of the lymphatic basins and positive nodes were recorded intraoperatively. In the porcine model, the visibility gradually became clear at an ICG concentration higher than 0.1mg/ml. In the clinical study, the average number of detected lymphatic basins was 3.3, 1.7, and 1.7, respectively. The mean number of detected SNs was 14.7, 6.7, and 4.0, respectively. To improve the reproducibility of SN biopsy, it is essential to prepare the correct concentration setting of ICG. Under current conditions in which ICG is injected intraoperatively, a 0.1mg/ml concentration setting of ICG may be necessary and sufficient for SN identification.

Multimodal real-time imaging with laser speckle contrast and fluorescent contrast

IntroductionLaser speckle contrast imaging (LSCI) can achieve real-time 2D perfusion maps non-invasively. However, LSCI is still difficult to use in general clinical applications because of movement sensitivity and limitations in blood flow analysis. To overcome this, fluorescence imaging (FI) is combined with LSCI using a light source with a wavelength of 785 nm in near-infrared (NIR) region and validates to visualize real-time blood perfusion. Materials and methodsThe system was performed using Intralipid and indocyanine green (ICG) in a flow phantom that has three tubes and controlled the flow rate in 0–150 μl/min range. First, real-time LSCI was monitored and measured the change in speckle contrast by reperfusion. Then, we visualized blood perfusion of a rabbit ear under the non-invasive condition by intravenous injection using a total of five different ICG concentration solutions from 128 μM to 3.22 mM. ResultsThe combined system achieved the performance of processing laser speckle images at about 37–38 fps, and we simultaneously confirmed the fluorescence of ICG and changes in speckle contrast due to intralipid as a light scatterer. In addition, we obtained real-time contrast variation and fluorescent images occurring in rabbit's blood perfusion. ConclusionsThe aim of this study is to provide a real-time diagnostic imaging system that can be used in general clinical applications. LSCI and FI are combined complementary for observing tissue perfusion using a single NIR light source. The combined system could achieve real-time visualization of blood perfusion non-invasively.

Thermal damage analysis of sub-surface soft tissue sarcoma for indocyanine green mediated photothermal cancer therapy

Photothermal therapy is a minimal invasive technique to treat tumors situated near the skin or other light accessible organs. Here, a photothermal agent is delivered to tumor either intratumorally or intravenously and the tumor is irradiated with near infrared (NIR) radiation to generate heat for thermal damage of tumor. In this paper, thermal damage of soft tissue sarcoma, a type of sub-surface forearm tumor, is evaluated for photothermal therapy using numerical simulations. Indocyanine green (ICG) is used as photothermal agent and the effect of various spatial distributions and doses of ICG for sub surface tumors located at various depths (3–6 mm) were investigated. Further, numerical simulation is validated experimentally through tumor-tissue mimicking phantoms. Computations were performed in MATLAB software using Lattice Boltzmann method and validated through experiments using tumor-tissue mimicking phantoms. Results show that the thermal damage region (damage parameter (Ω) of magnitude 4.6) was enlarged on increasing the concentration of ICG while it got shrunk for the deeper tumors. Computations reveal that ICG concentration of 50 μg/mL is optimum, for intravenous distribution, for photothermal therapy with minimal damage to surrounding tissue. It is found that irradiation duration of more than 900 s is required to achieve the complete damage of tumor. For the case of deeper tumors, about 1200 s of exposure is required, at irradiation intensity of 0.25 W/cm2. This study provides a numerical approach to determine therapeutic parameters and demonstrates the thermal damage for subsurface tumors through ICG mediated photothermal therapy by proper selection of therapeutic parameters.

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.

Indocyanine Green (ICG) Fluorescence Is Dependent on Monomer with Planar and Twisted Structures and Inhibited by H-Aggregation.

The optical properties of indocyanine green (ICG) as a near-infrared (NIR) fluorescence dye depend on the nature of the solvent medium and the dye concentration. In the ICG absorption spectra of water, at high concentrations, there were absorption maxima at 700 nm, implying H-aggregates. With ICG dilution, the main absorption peak was at 780 nm, implying monomers. However, in ethanol, the absorption maximum was 780 nm, and the shapes of the absorption spectra were identical regardless of the ICG concentration, indicating that ICG in ethanol exists only as a monomer without H-aggregates. We found that emission was due to the monomer form and decreased with H-aggregate formation. In the fluorescence spectra, the 820 nm emission band was dominant at low concentrations, whereas at high concentrations, we found that the emission peaks were converted to 880 nm, suggesting a new form via the twisted intramolecular charge transfer (TICT) process of ICG. The NIR fluorescence intensity of ICG in ethanol was approximately 12- and 9-times brighter than in water in the NIR-I and -II regions, respectively. We propose an energy diagram of ICG to describe absorptive and emissive transitions through the ICG structures such as the monomer, H-aggregated, and TICT monomer forms.

Liver functional assessment using time-associated change in the liver-to-spleen signal intensity ratio on enhanced magnetic resonance imaging: a retrospective study

BackgroundLiver-to-spleen signal intensity ratio (LSR) is evaluated by magnetic resonance imaging (MRI) in the hepatobiliary phase and has been reported as a useful radiological assessment of regional liver function. However, LSR is a passive (non-time-associated) assessment of liver function, not a dynamic (time-associated) assessment. Moreover, LSR shows limitations such as a dose bias of contrast medium and a timing bias of imaging. Previous studies have reported the advantages of time-associated liver functional assessment as a precise assessment of liver function. For instance, the indocyanine green (ICG) disappearance rate, which is calculated from serum ICG concentrations at multiple time points, reflects a precise preoperative liver function for predicting post-hepatectomy liver failure without the dose bias of ICG or the timing bias of blood sampling. The aim of this study was to develop a novel time-associated radiological liver functional assessment and verify its correlation with traditional liver functional parameters.MethodsA total of 279 pancreatic cancer patients were evaluated to clarify fundamental time-associated changes to LSR in normal liver. We defined the time-associated radiological assessment of liver function, calculated using information on LSR from four time points, as the “LSR increasing rate” (LSRi). We then investigated correlations between LSRi and previous liver functional parameters. Furthermore, we evaluated how timing bias and protocol bias affect LSRi.ResultsSignificant correlations were observed between LSRi and previous liver functional parameters such as total bilirubin, Child-Pugh grade, and albumin-bilirubin grade (P < 0.001 each). Moreover, considerably high correlations were observed between LSRi calculated using four time points and that calculated using three time points (r > 0.973 each), indicating that the timing bias of imaging was minimal.ConclusionsThis study propose a novel time-associated radiological assessment, and revealed that the LSRi correlated significantly with traditional liver functional parameters. Changes in LSR over time may provide a superior preoperative assessment of regional liver function that is better for predicting post-hepatectomy liver failure than LSR using the hepatobiliary phase alone.

Handheld photoacoustic imaging of indocyanine green clearance for real-time quantitative evaluation of liver reserve function.

Preoperative assessment of liver function reserve (LFR) is essential for determining the extent of liver resection and predicting the prognosis of patients with liver disease. In this paper, we present a real-time, handheld photoacoustic imaging (PAI) system-based noninvasive approach for rapid LFR assessment. A linear-array ultrasound transducer was sealed in a housing filled with water; its front end was covered with a plastic wrap. This PAI system was first implemented on phantoms to confirm that the photoacoustic (PA) intensity of indocyanine green (ICG) in blood reflects the concentration of ICG in blood. In vivo studies on normal rabbits and rabbits with liver fibrosis were carried out by recording the dynamic PA signal of ICG in their jugular veins. By analyzing the PA intensity-time curve, a clear difference was identified in the pharmacokinetic behavior of ICG between the two groups. In normal rabbits, the mean ICG clearance rate obtained by PAI at 15 min after administration (PAI-R15) was below 21.6%, whereas in rabbits with liver fibrosis, PAI-R15 exceeded 62.0% because of poor liver metabolism. The effectiveness of the proposed method was further validated by the conventional ICG clearance test and pathological examination. Our findings suggest that PAI is a rapid, noninvasive, and convenient method for LFR assessment and has immense potential for assisting clinicians in diagnosing and managing patients with liver disease.

104 Indocyanine Green Fluorescence Differentiates Necrotic Cells from Healthy and Apoptotic Cells

Abstract Introduction No objective technique exists to distinguish necrotic from viable tissue, risking over-excision in burns and loss of wound healing potential. Using delayed fluorescence imaging of indocyanine green (ICG), a method called second window ICG (SWIG), we have shown that high dose ICG persists in burn wounds in both animals and patients 24 hours after infusion. The necrotic avidity of ICG is proposed as the underlying mechanism, although inflammation also likely has a role. The objective of this study is to examine the hypothesis at both the tissue and cellular levels. Methods To examine the localization of ICG in burn tissue, 4-mm biopsies taken from burn patients who underwent SWIG were embedded and sequentially sectioned for H&amp;E (tissue architecture) and LDH (tissue viability) and ICG fluorescence imaging. To examine whether ICG preferentially binds to necrotic cells, primary skin cells (fibroblasts or keratinocytes) were subjected to thermal injury at 65ºC for 0 (untreated), 2.5 or 5 minutes. The cells were subsequently incubated with ICG at concentrations ranging from 0.5 to 5 μg/mL at 37ºC for 30 minutes. A necrosis and apoptosis detection kit with Yo-Pro™-1 and propidium iodide (PI) was used to differentiate live, apoptotic and necrotic cell populations in flow cytometry. The ICG florescence intensity of each cell population was measured with flow cytometry. Results The fluorescence microscopic imaging revealed that ICG intensity was most intense in the superficial severely thermally-injured tissue and gradually decreased with depth. This zone of high ICG intensity was co-localized with high cellularity (shown in H&amp;E) consisting of a mixture of nonviable skin cells (shown in LDH) and inflammatory infiltrates. Using flow cytometry, the optimal concentration of ICG with the highest ICG florescence median intensity (FMI) and the best separation of live, apoptotic and necrotic cell populations was 2.5 μg/mL, which was used for subsequent flow cytometry experiments. For both fibroblasts and keratinocytes, the ICG FMI was significantly higher in the necrotic cell population than that of either the live or apoptotic cell population, suggesting higher affinity of ICG to necrotic cells. The ICG FMI of necrotic cells with longer heat exposure (5 minutes) was significantly higher than that of necrotic cells with shorter heat exposure (2.5 minutes), suggesting that the binding sites for ICG increase with the degree of thermal injury. Conclusions This study demonstrates the necrotic avidity of ICG in burned skin tissue and two primary skin cell types. Further studies are needed to study the ICG binding characteristics with inflammatory cell populations and single cell suspensions dissociated from human burn tissue. Applicability of Research to Practice This, along with our pilot study of SWIG in patients, supports the feasibility of SWIG in guiding surgical decision-making in burn excision by defining thresholds of fluorescence intensity values.

Evaluation of indocyanine-mediated photodynamic therapy cytotoxicity in human osteoblast-like cells: an in vitro study.

Antimicrobial photodynamic therapy (aPDT) is an adjunctive non-invasive procedure for the management of periodontal tissue infection and deep periodontal pocket decontamination. However, the effects of this procedure on periodontal cells like osteoblasts that play a role in periodontal tissue repair and regeneration is not yet clear.

Paradoxical alteration of indocyanine green concentration in bile and the visibility of the intra-operative fluorescence cholangiography in pigs.

A significant difference exists between the reported optimal timing of indocyanine green (ICG) injection during fluorescence cholangiography and ICG dissipation time from the serum. There are no reports on alterations in ICG concentration in biliary fluid over time. Herein, we measured the concentration of ICG and the fluorescence intensity ratio between the common bile duct (CBD) and liver, which was recognized as a parameter of the visibility of the CBD. ICG (0.05mg/kg) was injected intravenously into female pigs (n=7). Afterwards, the fluorescence of the CBD and liver was detected at 30min, 2h, and 4h. Biliary fluid was collected from cannulated CBD tubes. The fluorescence intensity was measured using captured images and calculated using the ImageJ image-processing program. ICG concentration was measured using spectrophotometry and compared using an analysis of variance test. Biliary ICG concentrations at 30min, 2h, and 4h were 92.07±27.72μg/mL, 37.14±9.76μg/mL (p<0.05 vs. 30 min), and 13.91±5.71μg/mL (p<0.05 vs. 30 min), respectively; p<0.01. The CBD/liver fluorescence intensity ratios at 30min, 2h, and 4h were 1.25±0.72, 2.39±1.28 (p<0.05 vs. 30 min and 4h), and 3.38±1.73 (p<0.05 vs. 30 min and 2h), respectively. The ICG biliary concentration was highest at 30min, whereas the CBD/liver fluorescence intensity ratio was highest at 4h. Decreasing the fluorescence intensity of the liver may be an important approach for improving the visualization of the CBD during fluorescence cholangiography. PE/EA/491-5/2020.

Quantitative regional cerebral blood flow measurement using near-infrared spectroscopy and indocyanine green in patients undergoing superficial temporal to middle cerebral artery bypass for moyamoya disease: a novel method using a frequency filter.

Measuring regional cerebral blood flow (rCBF) after revascularization for moyamoya disease, as a type of ischemic cerebrovascular disease, is crucial. This study aims to validate our novel technology that combines near-infrared spectroscopy (NIRS) with a frequency filter to extract the arterial component. We measured rCBF before and after revascularization for moyamoya disease and at the end of the surgery using NIRO-200NX (Hamamatsu Photonics, Japan) and indocyanine green (ICG). rCBF was calculated using Fick's principle, change in arterial ICG concentrations, and maximum arterial ICG concentration. rCBF measured with NIRS (rCBF_N) was compared with pre- and postoperative rCBF measured with SPECT (rCBF_S). Thirty-four procedures were analyzed. rCBF_N increased from baseline to end of the surgery (mean difference (MD), 2.99ml/min/100g; 95% confidence interval (CI), 0.40-5.57ml/min/100g on the diseased side; MD, 4.94ml/min/100g; 95% CI, 2.35-7.52ml/min/100g on the non-diseased side). Similar trends were observed for rCBF_S (MD, 3.98ml/min/100g; 95% CI, 2.30-5.67ml/min/100g on the diseased side; MD, 2.77ml/min/100g; 95% CI, 1.09-4.45ml/min/100g on the non-diseased side). Intraclass correlations 3 (ICC3s) between rCBF_N and rCBF_S were weak on the diseased side (ICC3, 0.25; 95% CI, -0.03-0.5; p = 0.07) and the non-diseased side (ICC3, 0.24; 95% CI, -0.05-0.5; p = 0.08). rCBF measurements based on this novel method were weakly correlated with rCBF measurements with SPECT.

Antimicrobial Behavior and Cytotoxicity of Indocyanine Green in Combination with Visible Light and Water-Filtered Infrared A Radiation against Periodontal Bacteria and Subgingival Biofilm.

The widespread increase of antibiotic resistance highlights the need for alternative treatments such as antimicrobial photodynamic therapy (aPDT). This study aimed to evaluate the antimicrobial behavior and cytotoxicity of aPDT with indocyanine green (ICG) in combination with visible light (Vis) and water-filtered infrared A (wIRA). Representative periodontal bacteria (Parvimonas micra, Atopobium riame, Slackia exigua, Actinomyces naeslundii, Porphyromonas gingivalis, Fusobacterium nucleatum, Aggregatibacter actinomycetemcomitans, and Prevotella nigrescens) and subgingival in situ biofilms from periodontal patients were treated with aPDT for 5 min. ICG was used at different concentrations (50–500 µg/mL) and the number of viable cells was determined in colony forming units (CFU). Untreated negative controls and 0.2% chlorhexidine as a positive control were also prepared. The cytotoxicity test on human keratinocytes in vitro was analyzed with the AlamarBlue assay after 5, 10, and 20 min, with four ICG concentrations, and at two temperatures (room temperature and 37 °C). The tested periodontal pathogens treated with aPDT were eliminated in a range between 1.2 and 6.7 log10 CFU, except for A. naeslundii, which was killed at a lower range. The subgingival biofilm treated with aPDT expressed significant differences to the untreated controls except for at 300 µg/mL ICG concentration. The cytotoxicity was directly related to the concentration of ICG and irradiation time. These observations raise questions concerning the use of this specific aPDT as an adjuvant to periodontal treatments due to its possible toxicity towards human gingival cells.

Assessment and Comparison of Three Dimensional Exoscopes for Near-Infrared Fluorescence-Guided Surgery Using Second-Window Indocyanine-Green.

ObjectiveCompared to microscopes, exoscopes have advantages in field-depth, ergonomics, and educational value. Exoscopes are especially well-poised for adaptation into fluorescence-guided surgery (FGS) due to their excitation source, light path, and image processing capabilities. We evaluated the feasibility of near-infrared FGS using a 3-dimensional (3D), 4 K exoscope with near-infrared fluorescence imaging capability. We then compared it to the most sensitive, commercially-available near-infrared exoscope system (3D and 960 p). In-vitro and intraoperative comparisons were performed. MethodsSerial dilutions of indocyanine-green (1–2000 μg/mL) were imaged with the 3D, 4 K Olympus Orbeye (system 1) and the 3D, 960 p VisionSense Iridium (system 2). Near-infrared sensitivity was calculated using signal-to-background ratios (SBRs). In addition, three patients with brain tumors were administered indocyanine-green and imaged with system 1, with two also imaged with system 2 for comparison. ResultsSystems 1 and 2 detected near-infrared fluorescence from indocyanine green concentrations of >250 μg/L and >31.3 μg/L, respectively. Intraoperatively, system 1 visualized strong near-infrared fluorescence from two, strongly gadolinium-enhancing meningiomas (SBR=2.4, 1.7). The high-resolution, bright images were sufficient for the surgeon to appreciate the underlying anatomy in the near-infrared mode. However, system 1 was not able to visualize fluorescence from a weakly-enhancing intraparenchymal metastasis. In contrast, system 2 successfully visualized both the meningioma and the metastasis but lacked high resolution stereopsis. ConclusionThree-dimensional exoscope systems provide an alternative visualization platform for both standard microsurgery and near-infrared fluorescent guided surgery. However, when tumor fluorescence is weak (i.e., low fluorophore uptake, deep tumors), highly sensitive near-infrared visualization systems may be required.

Customized Color Settings of Digitally Assisted Vitreoretinal Surgery to Enable Use of Lower Dye Concentrations During Macular Surgery.

PurposeThis study evaluated the color contrast ratio (CCR) of the internal limiting membrane (ILM) using different color settings of digitally assisted vitreoretinal surgery (DAVS) with different indocyanine green (ICG) concentrations.sMethodsThis is a prospective comparative observational study. Consecutive patients that underwent 25G vitrectomy and ILM peeling using a standard operating microscope (SOM) (25 eyes), DAVS Ver. 1.1 (12 eyes), or DAVS Ver. 1.3 (13 eyes) were enrolled. The SOM and DAVS Ver. 1.1 groups used 0.075% ICG, and the DAVS Ver. 1.3 group used 0.025% ICG. In DAVS Ver. 1.1, macular CCR was compared between four different presets in the red, green, and blue channels: Default (Red (R) 100%, Green (G) 100%, and Blue (B) 100%); Preset 1 (R 20%, G 100%, B 100%); Preset 2 (R 80%, G 80%, B 100%), and Preset 3 (R 85%, G 100%, B 90%). In DAVS Ver. 1.3, macular CCR was evaluated using two different customized settings that modified the hue and saturation: Customized Setting 1 (R 86, G 100, B 100%, Hue +2°, Saturation 90%, Gamma 1.2) and Customized Setting 2 (R 90, G 100, B 100%, Hue +20°, Saturation 100%, Gamma 0.9). All patients underwent ophthalmologic examinations including BCVA at baseline and at 12 months.ResultsIn DAVS Ver. 1.1, macular CCR was highest in Preset 3 (P < 0.01). The CCR of Customized Setting 2 of DAVS Ver. 1.3 using 0.025% ICG did not differ from that of Preset 3 in DAVS Ver. 1.1 using 0.075% ICG. Furthermore, there was no significant difference in BCVA between the Customized Setting 2 of DAVS Ver. 1.3 with 0.025% ICG and the Preset 3 of DAVS Ver. 1.1 with 0.075% ICG groups at baseline and at 12 months (P > 0.05, respectively).ConclusionCustomized DAVS settings enabled surgeons to use a 3-fold lower ICG concentration in ILM peeling.

Polylactide nanoparticles encapsulating indocyanine green for photothermal therapy of prostate cancer cells

BackgroundThe aim of this study is to investigate the in vitro phototherapeutic potential of indocyanine green (ICG) loaded polylactide (PLA) nanoparticles on prostate cancer cells. Many attempts at designing drug delivery systems against cancer were made that incorporates ICG as a photothermal, photodynamic or imaging agent. However, most of these systems contain at least one more drug, making it hard to assess the effects of ICG alone. MethodsNanoparticles (ICGNP) were prepared via nanoprecipitation. The effects of phase volume ratio and ICG concentration on size, loading capacity and encapsulation efficiency were explored. Photothermal and photodynamic properties of ICGNP were examined. PC-3 cells were used for cell viability tests. Irradiation was achieved via custom built 809-nm computer controlled diode laser at 1 W/cm2 (up to 600 J/cm2). Data were analyzed by ANOVA followed by Tukey's test (p ≤ 0.05). ResultsICGNP exhibited mean size of 300 nm with low polydispersity, and zeta potential of -14 mV. Upon laser irradiation, ICGNP were capable of causing temperature increase and producing singlet oxygen. On PC-3 cells, ICGNP were proved to be as effective as free ICG in inducing cell death. The measured temperature increase in culture medium and experiments with singlet oxygen quenchers suggest that the decrease in cell viability was mainly the result of photothermal action. ConclusionsICGNP was effective as a photothermal agent on PC-3 cells but further improvements are required to increase ICG loading capacity for it to be useful on a wide range of cell types.

Towards Quantitative ICG Angiography: Fluorescence Monte Carlo Multi Cylinder

Abstract Intraoperative blood flow measurement is an effective way to assess the quality of bypass surgery. Flow quantification from indocyanine green (ICG) angiography promises to be an easy, contact-free method. It shows deviations compared to a reference. These are given as factor k, which depends on the vessel diameter d. The radiation transport within the vessel while recording the ICG passage might cause this. It is analyzed in silico to disclose its impact on k (d). A Fluorescence Monte Carlo Multi Cylinder (FMCMC) model was developed as a static model, assuming homogeneous concentration of ICG. In contrast to published approaches utilizing a Monte Carlo Multi Layer (MCML) model assuming the deepest penetration location within a photon packet’s path to be the fluorescence location, the events are modeled. Fluorescence event modeling, Multi Cylinder geometry and a homogeneous illumination as well as combinations of these were implemented in separate aspect models. Resulting k (d) were compared to k (d) from MCML. Deviations in k (d) derived from FMCMC and MCML in each aspect model were present. The Root Mean Square Error ranges from 6,8% to 36 %, k (d) also varied comparing the aspect models to each other. The model geometry, the modeled fluorescence location and illumination mode show a clear impact on simulated k (d). Therefore, our study shows that simplifications of previous studies are invalid. The developed FMCMC model considers the named aspects, allowing the analysis of radiation transport in ICG angiography. The FMCMC model assumes a homogeneous concentration of ICG which is not true in clinical cases. Obtaining the heterogeneous distribution of ICG is possible via fluid flow models. Coupling the fluid flow model and the developed radiation transport model as well as including a detailed camera optic is the task for future work.

Evaluation of photodynamic effect of Indocyanine green (ICG) on the colon and glioblastoma cancer cell lines pretreated by cold atmospheric plasma

BackgroundCold Atmospheric Plasma (CAP) has been proposed as a new approach based on its anticancer potential. However, its biological effects in combination with other physical modalities may also enhance efficiency and expand the applicability of the CAP method Photodynamic Therapy (PDT) may be improved by the use of indocyanine green (ICG) photosensitizer with absorption wavelength in the near infrared region to allow for deeper treatment depth.. In this study, the effectiveness of cold atmospheric helium plasma (He-CAP) as a pretreatment on the efficiency of ICG mediated PDT was investigated. Methods and materialFirst, toxicity of different concentrations of ICG on HT-29 and U-87MG cell lines was examined for 24 h. IC10 and IC30 of ICG were determined and then cells were treated with this ICG concentrations with different plasma radiation doses and light exposures for 48 h. Finally, MTT assay was performed for all treatment groups. The experiments were repeated at least 4 times at each group for two cell lines, separately. In order to compare the results, several indicators such as treatment efficiency, synergistic ratio, and the amount of optical exposure required for 50% cell death (ED50) were also defined. Finally, SPSS 20 software is used for statistical analysis of data. ResultsPretreatment with CAP could significantly reduce cell survival in both cell lines (P<0.05). Also concentrations, irradiation time with CAP, and appropriate light exposure in both cell lines increased therapeutic efficiency compared to either treatment alone (P<0.05). While increasing the efficiency of photodynamic therapy varied between the two cell lines, the improvement in the PDT process was demonstrated by pretreatment with CAP. ConclusionSynergistic effect in the cell death with PDT were observed following He-CAP treatment and the results indicated that pretreatment with He-CAP improves the efficiency of photodynamic therapy.