Quantitative analysis of colon perfusion pattern using indocyanine green (ICG) angiography in laparoscopic colorectal surgery. Surg Endosc. 2019;33:1640-1649. [PMID: 30203201 PMCID: PMC6484815 DOI: 10.1007/s00464-018-6439-y]

Comparative outcomes of parenchyma-sparing repeat pancreatectomy vs completion pancreatectomy: impact on endocrine function and diabetes management

BACKGROUND

Although completion pancreatectomy (CP) is the standard approach for repeat pancreatectomy of secondary pancreatic tumors, the incidence of postoperative endocrine insufficiency is high. Parenchyma-sparing repeat pancreatectomy (PSRP) can preserve this function. However, its feasibility and long-term outcomes have not been evaluated. This study compared short-term outcomes and long-term endocrine pancreatic function between PSRP and CP.

METHODS

Consecutive patients who underwent a second pancreatectomy between April 2005 and March 2024 at 2 high-volume centers were included. This study compared the short- and long-term outcomes between the PSRP and CP groups. Serum hemoglobin A1c (HbA1c) levels 6 months after surgery and the occurrence of hypoglycemic episodes were evaluated as indicators of endocrine function.

RESULTS

A total of 30 patients (11 in the PSRP group and 19 in the CP group) were included. The 2 groups showed no significant differences in the preoperative or intraoperative findings. None of the patients in the PSRP group experienced major morbidity (Clavien-Dindo grade of ≥III), whereas 4 patients (21%) in the CP group experienced major morbidity. HbA1c levels and the requirement for insulin therapy were significantly lower in the PSRP group than in the CP group (6.2% vs 7.6% [P <.001] and 27.0% vs 100.0% [P <.001], respectively). Hypoglycemic episodes were observed only in the CP group (4 patients).

CONCLUSION

PSRP might have favorable short-term outcomes and better long-term endocrine function than CP.

Biophysical modeling and artificial intelligence for quantitative assessment of anastomotic blood supply in laparoscopic low anterior rectal resection

PURPOSE

Fluorescence imaging is critical for intraoperative intestinal perfusion assessment in colorectal surgery, yet its clinical adoption remains limited by subjective interpretation and lack of quantitative standards. This study introduces an integrated approach combining fluorescence curve analysis, biophysical modeling, and machine learning to improve intraoperative perfusion assessment.

METHODS

Laparoscopic fluorescence videos from 68 low rectal cancer patients were analyzed, with 1,263 measurement points (15-20 per case) selected along colonic bands. Fluorescence intensity dynamics were extracted via color space transformation, video stabilization and image registration, then modeled using the Random Sample Consensus (RANSAC) algorithm and nonlinear least squares fitting to derive biophysical parameters. Three clinicians independently scored perfusion quality (0-100 scale) using morphological features and biophysical metrics. An XGBoost model was trained on these parameters to automate scoring.

RESULTS

The model achieved superior test performance, with a root mean square error (RMSE) of 2.47, a mean absolute error (MAE) of 1.99, and an R2 of 97.2%, outperforming conventional time-factor analyses. It demonstrated robust generalizability, showing no statistically significant prediction differences across age, diabetes, or smoking subgroups (P > 0.05). Clinically, low perfusion scores in distal anastomotic regions were significantly associated with postoperative complications (P < 0.001), validating the scoring system's clinical relevance and discriminative capacity. The automated software we developed completed analyses within 2 min, enabling rapid intraoperative assessment.

CONCLUSION

This framework synergistically enhances surgical evaluation through three innovations: (1) Biophysical modeling quantifies perfusion dynamics beyond time-based parameters; (2) Machine learning integrates multimodal data for surgeon-level accuracy; (3) Automated workflow enables practical clinical translation. By addressing limitations of visual assessment through quantitative, rapid, and generalizable analysis, this method advances intraoperative perfusion monitoring and decision-making in colorectal surgery.

Advancement of indocyanine green fluorescence imaging technology in laparoscopic surgery for rectal cancer

Indocyanine green fluorescence imaging technology has been increasingly utilized in rectal surgery in recent years. As a safe tracer, indocyanine green can facilitate lymph node tracing, assess the blood supply at anastomotic sites, and localize tumour lesions during laparoscopic surgery, thereby resulting in favourable outcomes. This technology helps surgeons to achieve more precise diagnoses and treatments in laparoscopic procedures, thus ultimately benefiting patients. However, the current application of indocyanine green fluorescence imaging technology still lacks standardized regulations, and certain effects remain contentious. This study provides a comprehensive review of the application of indocyanine green in laparoscopic surgery for rectal cancer based on the pertinent literature.

Quantification of indocyanine green fluorescence angiography in colorectal surgery: a systematic review of the literature

BACKGROUND

Indocyanine green fluorescence angiography (ICGFA) during colorectal surgery associates with reduced post-operative anastomotic complication rates. Because its interpretation is subjective, quantification has been proposed to address inter-user variability. This study reviews the published literature regarding ICGFA quantification during colorectal surgery with a focus on impactful clinical deployment.

METHODS

A systematic review was performed of English language publications regarding clinical studies of ICGFA quantification in colorectal surgery in PubMed, Scopus, Web of Science and Cochrane Library on 29th August 2024, updated to 18th November 2024, following PRISMA guidelines. Newcastle Ottawa scale (NOS) was used to assess quality.

RESULTS

A total of 1428 studies were screened with 22 studies (1469 patients) selected. There was significant heterogeneity of ICGFA methodology, quantification methods and parameter selection and only three studies were NOS "high" quality. Extracorporeal application was most common. Four studies (154 patients) conducted real-time ICGFA analyses (others were post hoc) and four utilised artificial intelligence methods. Eleven studies only included patients undergoing left-sided resection (six focusing specifically on rectal resections). Only one study employed the quantification method to guide intra-operative decision-making regarding colonic transection. Twenty-six different perfusion parameters were assessed, with time from injection to visible fluorescence and maximum intensity the most commonly (but not only) correlated parameters regarding anastomotic complication (n = 18). Other grounding correlates were tissue oxygenation (n = 3, two with hyperspectral imagery), metabolites (n = 2) and surgeon interpretation (n = 5).

CONCLUSION

Quantification of the ICGFA signal for colorectal surgery is feasible but has so far seen limited academic advancement beyond feasibility.

Evaluation of anastomotic blood supply during digestive tract reconstruction with the use of the oxygen saturation index: A pooling up analysis

PURPOSE

Anastomotic leakage (AL) is one of the most serious clinical complications in digestive tract reconstruction (DTR) surgery, and it is currently hypothesized that this may be related to insufficient anastomotic blood supply. Thus, Therefore, we aimed to assess the ability of tissue oxygen saturation(StO2) as a measure to evaluate anastomotic blood supply.

METHODS

A comprehensive literature search was performed using Embase, PubMed and Cochrane Library. StO2 was used as an evaluation index of anastomotic blood supply after DTR to analyze the potential association between this index and the occurrence of AL in the postoperative period.

RESULTS

A total of eleven articles involving 867 participants were included in this systematic review and meta-analysis. After pooling the standardized mean difference (SMD) and 95% confidence intervals (Cls), low StO2 was found to be an independent risk factor for AL (P < 0.00001; 95%CI: 1.02 [0.53-1.51]). The mean StO2 in the AL group (62.3%) was significantly lower than that in the non-AL group (74.3%); AL incidence increased with the reduction of StO2 to a certain value to 201.8% and 338.1% respectively.

CONCLUSION

Oxygen saturation index can be utilized in DTR to accurately and quantitatively evaluate the anastomotic blood supply to reduce the probability of postoperative AL.

Photoacoustic Imaging for Image-Guided Gastric Tube Placement: Ex Vivo Characterization

Over 250,000 gastrostomy tubes (G-tubes) are placed annually in the United States. Percutaneous endoscopic gastrostomy (PEG) is the most widely used clinical method for placing G-tubes within the stomach. However, endoscope detectability is limited due to the scattering of light by tissues. Poor organ visibility and low sensitivity of the palpation techniques cause blind needle insertions, which cause colon/liver perforations, abdominal bleeding, and gastric resections. Additionally, imaging artifacts and the poor distinguishability between water-filled tissues make ultrasound (US) imaging-based techniques incompatible with G-tube placement. The risk of ionizing radiation exposure and the confinement of fluoroscopy to radiology suites limits its bedside utility in patients. Considering these limitations, we propose to design a safe, point-of-care integrated US and photoacoustic (PA) imaging system for accurate G-tube placement procedures, for a broad spectrum of patients, and to characterize the system's effectiveness. Our proposed technology utilizes a clinically safe contrast agent and a dual-wavelength approach for precise procedures. Our ex vivo tissue studies indicated that PA imaging accurately differentiates the different organs at specific wavelengths. Our characterization studies revealed that PA imaging could detect lower concentrations of Indocyanine Green (ICG) dye coating the colon wall, minimizing the risk of ICG dye-related toxicity and providing safer G-tube placements.

Implementation of intraoperative procedures to prevent anastomotic leak in low anterior rectal resections: a pilot study for a novel technique to evaluate anastomotic vascularization

INTRODUCTION

Altered vascular microcirculation is recognized as a risk factor for anastomotic leakage (AL) in colorectal surgery. However, few studies evaluated its impact on AL using different devices, with heterogeneous results. The present study reported the initial experience measuring gut microcirculatory density and flow with the aid of incidence dark-field (IDF) videomicroscopy (Cytocam, Braedius, Amsterdam, The Netherlands) comparing its operative outcome using a propensity score matching (PSM) model based on age, gender, and Charlson Comorbidity Index (CCI).

MATERIALS AND METHODS

Videos from 5 different sites (at least 10 s/site) were recorded from both the mucosal and serosal site of the left colon end after the colonic resection. Total vessel density (TVD), Perfused Vessel Density (PVD), De Backer score, Proportion of Perfused Vessels (PPV), and Microvascular Flow Index (MFI) were analyzed. At each recording, noninvasive measurements of blood pressure, heart rate, temperature, use of vasoactive drugs, and peripheral oxygen saturation were simultaneously recorded. The association between postoperative outcomes and microcirculation evaluation was investigated using PSM analyses.

RESULTS

Ninety-nine patients were included in the Cytocam group. The mean TVD small was 8.9 ± 2.8 mm/mm2, the PPV small % was 100 in all patients but 1, while the MFI was 3 in all patients. The mean PVD small was 8.76 ± 2.8 mm/mm2 and the mean De Becker score was 4.4 ± 1.3. In 2 patients (10.5%), the finding of altered vascularization resulted in the change of the operative strategy with an extension of the resection point. AL occurred in 2 patients of the No Cytocam group (p = 0.811).

CONCLUSION

This type of anastomotic evaluation has shown to be feasible, safe, and useful in easily detecting any alteration of the resected colon before anastomotic construction. Moreover, this technology could offer a more cost-effective manner than other devices.

Impact of indocyanine green fluorescence angiography on surgeon action and anastomotic leak in colorectal resections. A systematic review and meta-analysis

BACKGROUND

Indocyanine green fluorescence angiography (ICGFA) during colorectal surgery either reassures surgeons regarding intestinal perfusion sufficiency or prompts changed surgical strategy by indicating unsuspected insufficiency. This study describes existing evidence supporting ICGFA use in colorectal surgery, particularly regarding impact on intraoperative decisions.

METHODS

Searches were performed on PubMed, ScienceDirect, Scopus, Web of Science, Cochrane Collaboration databases on 5th December 2023, updated to 19th August 2024. Full English language publications of clinical studies in human patients undergoing colorectal resection with primary anastomosis with the use of ICGFA to assess bowel perfusion intraoperatively, with a control group, were included. Pooling of anastomotic leak (AL) rates was performed for primary outcome analysis with odds ratio (OR) and number-needed-to-treat (NNT) calculated regarding leak reduction.

RESULTS

45 studies comprising 14,333 patients were included, with 7 randomised controlled trials (2911 patients). Overall, AL rate was 6.8%, 4.5% with ICGFA and 8.5% without (OR:0.47, p < 0.001, NNT 23), increasing to 9.5%, 7.5% and 11.6%, respectively, in randomised controlled trials (OR:0.62, p < 0.01, NNT 25). In rectal resections, AL rate was 4.7% with ICGFA vs 11.5% without (OR: 0.38, p < 0.0001). 26 studies performed ICGFA before and after anastomosis formation and 19 used ICGFA only prior to bowel transection, with no significant difference of AL rate reduction on subgroup testing. ICGFA prompted a change in surgical plan in 8.4% of thirty-four studies reporting this. Interestingly, in these studies, leak rates overall were 3.7% when ICGFA matched surgeon judgement versus 5.7% when it prompted change (OR 0.51, p < 0.0025), versus 7.7% without (OR 0.45, p < 0.0001). In rectal resections, these figures were 5%, 8.8% (OR 0.42, p = 0.01) and 12.0% (OR0.39, p < 0.0001), respectively.

CONCLUSIONS

ICGFA colorectal perfusion assessment is associated with lower anastomotic leak rates, especially when confirming surgeons' judgement, and may so stratify patients post-operatively regarding subsequent anastomotic leak rate.

Feasibility of indocyanine green fluorescence imaging to predict biliary complications in living donor liver transplantation: A pilot study

Backgrounds/Aims

Liver transplantation (LT) is now a critical, life-saving treatment for patients with liver cirrhosis or hepatocellular carcinoma. Despite its significant benefits, biliary complications (BCs) continue to be a major cause of postoperative morbidity. This study evaluates the fluorescence intensity (FI) of the common bile duct (CBD) utilizing near-infrared indocyanine green (ICG) imaging, and examines its association with the incidence of BCs within three months post-LT.

Methods

This investigation analyzed data from nine living donor LT (LDLT) recipients who were administered 0.05 mg/kg of ICG prior to bile duct anastomosis. Real-time perfusion of the CBD was recorded for three minutes using an ICG camera, and FI was quantified using Image J (National Institutes of Health). Key parameters assessed included F max, F1/2 max, T1/2 max, and the slope (F max/T max) to evaluate the fluorescence response.

Results

BCs occurred in two out of nine patients. These two patients exhibited the longest T1/2 max values, which were linked with lower slope values, implicating a potential relationship between extended T1/2 max, reduced slope, and the occurrence of postoperative BCs.

Conclusions

The study indicates that ICG fluorescence imaging may serve as an effective tool for assessing bile duct perfusion in LDLT patients. While the data suggest that an extended T1/2 max and lower slope may correlate with an increased risk of BCs, further validation through larger studies is required to confirm the predictive value of ICG fluorescence imaging in this setting.

Colorectal surgeons' perspectives on the efficacy of intraoperative bowel perfusion technology with a focus on indocyanine green fluorescence angiography

BACKGROUND

Level one evidence supports indocyanine green fluorescence angiography (ICGFA) use reducing anastomotic leak rates in colorectal surgery. We surveyed surgeons exploring perceptions and factors affecting its use in daily practice and adoption as routine standard of care.

METHODS

Validated electronic survey distributed via the Irish Association of Coloproctology, Royal College of Surgeons in Ireland, European Society of Surgical Oncology, European Association for Endoscopic Surgery, Milan Colorectal Congress and social media.

RESULTS

200 colorectal surgeons (143 consultants) responded. 147 (73.5%) surgeons already use ICGFA, with 90 (61.2%) using it routinely and 69 (46.9%) having a concomitant research interest. Strong clinical evidence base (83.5%) and protocol standardisation (78%) were overall rated most important for bowel perfusion technology with a majority of surgeons rating lack of standardisation and inter-user variability as challenges (similar between consultants and non-consultants). Lack of training and staff, reliability concerns and data security were perceived as significant barriers by selective users compared to non-users, and cost and operating time were perceived as significant barriers by selective users compared to routine users. Most surgeons (41.5%) ideated a number needed to treat (NNT) between 20 and 40 acceptable to advocate routine ICGFA use with 28% requiring a NNT < 20. Most surgeons (38.5%) indicate a per case cost savings of €250-500 supports routine use with 17% advocating it > €750.

CONCLUSIONS

With now a strong evidence base regarding clinical benefit, the survey respondents articulate remaining challenges for ICGFA as standard of care. Levels of expected benefit are largely in keeping with its reported performance.

Indocyanine green fluorescence-guided surgery in the emergency setting: the WSES international consensus position paper

BACKGROUND

Decision-making in emergency settings is inherently complex, requiring surgeons to rapidly evaluate various clinical, diagnostic, and environmental factors. The primary objective is to assess a patient's risk for adverse outcomes while balancing diagnoses, management strategies, and available resources. Recently, indocyanine green (ICG) fluorescence imaging has emerged as a valuable tool to enhance surgical vision, demonstrating proven benefits in elective surgeries.

AIM

This consensus paper provides evidence-based and expert opinion-based recommendations for the standardized use of ICG fluorescence imaging in emergency settings.

METHODS

Using the PICO framework, the consensus coordinator identified key research areas, topics, and questions regarding the implementation of ICG fluorescence-guided surgery in emergencies. A systematic literature review was conducted, and evidence was evaluated using the GRADE criteria. A panel of expert surgeons reviewed and refined statements and recommendations through a Delphi consensus process, culminating in final approval.

RESULTS

ICG fluorescence imaging, including angiography and cholangiography, improves intraoperative decision-making in emergency surgeries, potentially reducing procedure duration, complications, and hospital stays. Optimal use requires careful consideration of dosage and timing due to limited tissue penetration (5-10 mm) and variable performance in patients with significant inflammation, scarring, or obesity. ICG is contraindicated in patients with known allergies to iodine or iodine-based contrast agents. Successful implementation depends on appropriate training, availability of equipment, and careful patient selection.

CONCLUSIONS

Advanced technologies and intraoperative navigation techniques, such as ICG fluorescence-guided surgery, should be prioritized in emergency surgery to improve outcomes. This technology exemplifies precision surgery by enhancing minimally invasive approaches and providing superior real-time evaluation of bowel viability and biliary structures-areas traditionally reliant on the surgeon's visual assessment. Its adoption in emergency settings requires proper training, equipment availability, and standardized protocols. Further research is needed to evaluate cost-effectiveness and expand its applications in urgent surgical procedures.

Fluorescence angiography with indocyanine green for low anterior resection in patients with rectal cancer: a prospective before and after study

BACKGROUND

Inadequate bowel perfusion is among risk factors for colorectal anastomotic leaks. Perfusion can be assessed with indocyanine green fluorescence angiography (ICG) during colon resections. Possible benefits from its systematic use in high-risk patients with rectal cancer remain inconsistent. This study aimed to evaluate the surgical modifications induced by ICG assessment during rectal cancer surgery and associated anastomotic leaks.

METHODS

This prospective before and after cohort study was conducted in a single Canadian high-volume colorectal surgery center. Eligible patients were undergoing a low anterior resection for rectal cancer below 15 cm from the anal margin. Stapled and handsewn coloanal anastomoses were included. The experimental group was recruited prospectively, undergoing surgery using fluorescence angiography with ICG. The control group was built retrospectively from consecutive patients who had been operated on without ICG, prior to its implementation.

RESULTS

Each cohort included 113 patients. The use of ICG led to modifications from initial surgical plan in 10.6% of patients, with no occurrence of anastomotic leaks in this specific group. When comparing leak rates, using ICG seemed to be protective, but this could not be statistically proven, overall (13.3% vs. 6.2%, p = 0.07), nor for handsewn coloanal anastomoses (11.8% vs. 5.9%, p = 0.67). A lack of power could explain such non-significant results, especially with low overall anastomotic leak rates recorded.

CONCLUSION

ICG influenced ultimate proximal resection margin in a clinically relevant proportion of cases. It might be associated with reduced leak rates although not formally proven with this data. This technology is safe and easy to apply in high-volume colorectal centers.

Advancing Pediatric Surgery with Indocyanine Green: Nonhepatobiliary Applications and Outcomes

Aim

This prospective single-center study aimed to evaluate the nonhepatobiliary applications of indocyanine green fluorescence-guided surgery (ICG FGS) in pediatric patients, assessing its utility as an adjunct for intraoperative imaging.

Materials and Methods

Over a 30-month period from January 2021 to July 2023, pediatric patients undergoing various surgical procedures, excluding hepatobiliary cases, were included in the study. ICG (Aurogreen™) was administered intravenously or directly injected in tissue, and fluorescence imaging was conducted using specialized equipment (KARL STORZ GmbH and Co. KG). Patient demographics, diagnoses, surgical procedures, ICG protocols, intraoperative findings, and perioperative outcomes were analyzed.

Results

The study included seventeen pediatric cases including Hirschsprung disease, anorectal malformations, undescended testes, varicocele, Mayer-Rokitansky-Kustner-Hauser syndrome, ovarian torsion, chylous ascites, chylothorax, and Wilms' tumor. ICG aided in the real-time assessment of vascular, intestinal perfusion in Hirschsprung disease, anorectal malformations, delineation of lymphatics from vessels in varicocele, confirmation of preserved vascularity after detorsion of ovary, identification of lymphatics for ligation in chylothorax, and chylous ascites. ICG thus aided in precise dissection and confirming tissue viability without reported adverse events.

Conclusion

ICG FGS demonstrates significant potential as a tool for enhancing surgical outcomes in pediatric surgeries including indications beyond hepatobiliary cases. The findings suggest that ICG FGS can improve surgical precision by providing real-time assessment of tissue perfusion, and lymphatic mapping, thereby potentially reducing intraoperative complications. Further research and prospective studies are essential to validate its efficacy and establish standardized protocols, aiming to integrate ICG FGS as a routine adjunct in pediatric surgical practice.

Indocyanine Blue (ICB) as a Functional Alternative to Indocyanine Green (ICG) for Enhanced 700 nm NIR Imaging

Despite significant advancements in bioimaging technology, only a limited number of fluorophores are currently approved for clinical applications. Indocyanine green (ICG) is the first FDA-approved near-infrared (NIR) fluorophore and has significantly advanced clinical interventions over the past three decades. However, its single-channel imaging at 800 nm emission is often insufficient for capturing comprehensive diagnostic information during surgery. In this study, we evaluate indocyanine blue (ICB), an ICG analog with a shorter polymethine bridge, as a promising candidate for multi-channel NIR imaging. ICB demonstrated peak absorption and emission approximately 100 nm shorter than ICG in aqueous solutions, placing it within the 700 nm range of the NIR window. Furthermore, ICB exhibited favorable solubility and optical properties in aqueous environments, supporting its potential for in vivo imaging applications. Notably, ICB shows rapid systemic clearance, likely due to its lower molecular weight, which facilitates clear visualization in angiography, cholangiography, and lymph node mapping with minimal background interference. Additionally, dual-channel imaging of tumors and lymph nodes was achieved using a tumor-targeting fluorophore in conjunction with ICB, illustrating the potential for enhanced intraoperative guidance. ICB emitting at 700 nm, therefore, can be useful in NIR imaging, broadening the possibilities for improved diagnostic accuracy and therapeutic outcomes in clinical settings.

Optimal Indocyanine Green Dosage for Repetitive Angiography for Laparoscopic Colorectal Surgery

Background and Objectives: This study aimed to determine the minimal effective dose of indocyanine green (ICG) required for accurately assessing colonic perfusion during laparoscopic colorectal surgery using a laser-assisted laparoscopic near-infrared (NIR) camera system. Materials and Methods: In 15 patients with colorectal cancer undergoing right hemicolectomy, the left branch of the middle colic artery was preserved, and ICG angiography was performed in the transverse colon. To determine the optimal ICG dose, experimental doses of 0.01, 0.02, 0.03, 0.04, and 0.05 mg of ICG per patient's body weight (kg) were administered intravenously in each group. Additionally, a conventional dose of 0.2 mg/kg was administered in the same patients more than 30 min after the initial dose. For quantitative analysis, the fluorescent expression region was extracted, and fluorescence intensity was analyzed using automatic image processing. Analysis accessibility, T1/2MAX, perfusion time ratio, slope, artificial intelligence (AI)-based perfusion pattern analysis, and washout time were measured in 150 detailed regions of interest in each image. Results: Group 1 (0.01 mg/kg) showed significantly lower accessibility rates for quantitative analysis (48.0%) compared with Groups 2-5 (84.7-100%). The mean slope value in Group 1 was 3.7, which fell below the acceptable threshold (>4) and was significantly lower than that of the other groups (p < 0.001). An acceptable AI-based perfusion pattern was 14.2% in Group 1, significantly lower than in Groups 2-5 (66.4-100%). Washout time was significantly faster with minimal doses compared with conventional doses (39.0 ± 15.8 s vs. 117.5 ± 4.9 s, respectively, p < 0.001). Conclusions: This study supports the use of minimal ICG doses, ranging from 0.02 to 0.05 mg/kg, to optimize repetitive ICG angiography using a laser-assisted laparoscopic NIR camera.

Application of indocyanine green fluorescence angiography in evaluating blood flow in rotator cuff tears: a preliminary study

BACKGROUND

The relationship between the degree of vascularization at the edge of a torn rotator cuff tendon and cuff healing remains unclear. The purpose of this study was to employ indocyanine green (ICG) fluorescence angiography to evaluate the blood flow at the edge of a torn rotator cuff tendon under the subacromial view.

METHODS

Thirteen shoulders of 13 patients who underwent arthroscopic repair of full-thickness rotator cuff tears were included in this prospective study. Viewing from the posterolateral portal, ICG at 0.2 mg/kg body weight was intravenously administered, and the blood flow was recorded. After resecting the poorly vascularized torn edge of the tendon, ICG administration was repeated at the same volume. The fluorescence intensity and perfusion time of the tendon blood flow were evaluated using video analysis and modeling tools. Cuff integrity was evaluated using magnetic resonance imaging at 6 months postoperatively. Patients were divided into healed and retear groups, and the differences in the degree of blood flow were evaluated.

RESULTS

ICG fluorescence angiography could visualize the blood flow in the rotator cuff tendon, and the torn edge of the tendon with poor blood flow was resected. The overall retear rate was 23.1% (3/13). Based on quantitative analysis, the fluorescence intensity factors were significantly lower in the retear group than in the healed group before tendon débridement. The retear rate in the high blood flow group was 0% (0/7), while that in the low blood flow group was 50.0% (3/6).

CONCLUSIONS

ICG fluorescence angiography may play a role in the future of shoulder arthroscopy. Further study is needed to determine the effect of blood flow on tendon healing.

Dye-less quantification of tissue perfusion by laser speckle contrast imaging is equivalent to quantified indocyanine green in a porcine model

INTRODUCTION

Subjective surgeon interpretation of near-infrared perfusion video is limited by low inter-observer agreement and poor correlation to clinical outcomes. In contrast, quantification of indocyanine green fluorescence video (Q-ICG) correlates with histologic level of perfusion as well as clinical outcomes. Measuring dye volume over time, however, has limitations, such as it is not on-demand, has poor spatial resolution, and is not easily repeatable. Laser speckle contrast imaging quantification (Q-LSCI) is a real-time, dye-free alternative, but further validation is needed. We hypothesize that Q-LSCI will distinguish ischemic tissue and correlate over a range of perfusion levels equivalent to Q-ICG.

METHODS

Nine sections of intestine in three swine were devascularized. Pairs of indocyanine green fluorescence imaging and laser speckle contrast imaging video were quantified within perfused, watershed, and ischemic regions. Q-ICG used normalized peak inflow slope. Q-LSCI methods were laser speckle perfusion units (LSPU), the base unit of laser speckle imaging, relative perfusion units (RPU), a previously described methodology which utilizes an internal control, and zero-lag normalized cross-correlation (X-Corr), to investigate if the signal deviations convey accurate perfusion information. We determine the ability to distinguish ischemic regions and correlation to Q-ICG over a perfusion gradient.

RESULTS

All modalities distinguished ischemic from perfused regions of interest; Q-ICG values of 0.028 and 0.155 (p < 0.001); RPU values of 0.15 and 0.68 (p < 0.001); and X-corr values of 0.73 and 0.24 (p < 0.001). Over a range of perfusion levels, RPU had the best correlation with Q-ICG (r = 0.79, p < 0.001) compared with LSPU (r = 0.74, p < 0.001) and X-Corr (r = 0.46, p < 0.001).

CONCLUSION

These results demonstrate that Q-LSCI discriminates ischemic from perfused tissue and represents similar perfusion information over a broad range of perfusion levels comparable to clinically validated Q-ICG. This suggests that Q-LSCI might offer clinically predictive real-time dye-free quantification of tissue perfusion. Further work should include validation in histologic studies and human clinical trials.

The use of indocyanine green for colorectal anastomoses: a systematic review and meta-analysis

INTRODUCTION

Anastomotic leak is a relatively common and debilitating complication. Colorectal leak rates vary widely in the literature, ranging from 1% to 20%. In modern surgical practice, there is much emphasis on the use of indocyanine green (ICG). This is a fluorescent dye administered intravenously to locate and predict an adequate line of anastomosis. We sought to analyse the current literature and supporting evidence behind the use of ICG in the context of elective colorectal surgery.

METHODS

A literature search was conducted for papers published between January 1991 and December 2022 concerning the use of ICG in colorectal surgery. Data on anastomotic leak, overall complication rate, operative time and involvement of artificial intelligence (AI) were compared.

RESULTS

A total of 24 studies were selected, including 3 randomised controlled trials. There was an anastomotic leak rate of 4.3% in cases with ICG administration compared with 9.5% in the control group (p<0.00001). Seven studies mentioned overall complication rates. These were lower in the ICG cohort than in the control group (15.5% vs 24.5%). There was no significant correlation between ICG use and operative time (p=0.78). Five studies looked at AI, with results suggesting that use of AI leads to much better accuracy in ICG metric analysis. However, the current literature is still inconclusive.

CONCLUSIONS

While there is strong evidence behind ICG use in the existing literature, more randomised controlled trials are required for better recommendations. AI in ICG metric interpretation has proved to be difficult owing to interpatient variability. Nevertheless, new data suggest better understanding and standardisation.

Indocyanine Green (ICG) Fluorescence in the Assessment of Vascularity of Anastomotic Margins in Colorectal Surgery in a Lower Middle-Income Country (LMIC) Hospital

Background and Objective

One of the uses of indocyanine green (ICG) in the surgical field is the evaluation of the anastomotic margins in colorectal surgery. This is of particular importance because fluorescence imaging may aid in detecting vascular compromise, allowing the surgeon to change the resection margin thereby decreasing the chance of an anastomotic leak. To date, there has been no study with its use locally. This study aimed to determine whether the use of ICG can safely identify if the margins of resection are well-vascularized in patients undergoing left-sided colon or rectal surgery, which in turn may reduce anastomotic leak rates.

Methods

Through a retrospective study design, the investigators gathered data of patients who underwent left-sided colon or rectal surgery. The groups were divided into those with and without the use of ICG and a comparative data on the anastomotic leak rates were analyzed.

Results

Eighty-six (86) patients with similar patient characteristics, tumor staging, and surgical approach were compared. Both the leak rates identified during the initial hospital stay and at 30 days post-operatively were lower in those where ICG was used (p=0.035, p=0.047, respectively) than those where ICG was not used.

Conclusion

ICG fluorescence imaging may reduce the anastomotic leak rates in patients undergoing colorectal surgery.

Advancing indocyanine green fluorescence flap perfusion assessment via near infrared signal quantification

Introduction

Intraoperative indocyanine green fluorescence angiography (ICGFA) perfusion assessment has been demonstrated to reduce complications in reconstructive surgery. This study sought to advance ICGFA flap perfusion assessment via quantification methodologies.

Method

Patients undergoing pedicled and free flap reconstruction were subjected to intraoperative ICGFA flap perfusion assessment using either an open or endoscopic system. Patient demographics, clinical impact of ICGFA and outcomes were documented. From the ICGFA recordings, fluorescence signal quality, as well as inflow/outflow milestones for the flap and surrounding (control) tissue were computationally quantified post hoc and compared on a region of interest (ROI) level. Further software development intended full flap quantification, metric computation and heatmap generation.

Results

Fifteen patients underwent ICGFA assessment at reconstruction (8 head and neck, 6 breast and 1 perineum) including 10 free and 5 pedicled flaps. Visual ICGFA interpretation altered on-table management in 33.3% of cases, with flap edges trimmed in 4 and a re-anastomosis in 1 patient. One patient suffered post-operative flap dehiscence. Laparoscopic camera use proved feasible but recorded a lower quality signal than the open system.Using established and novel metrics, objective ICGFA signal ROI quantification permitted perfusion comparisons between the flap and surrounding tissue. Full flap assessment feasibility was demonstrated by computing all pixels and subsequent outputs summarisation as heatmaps.

Conclusion

This trial demonstrated the feasibility and potential for ICGFA with operator based and quantitative flap perfusion assessment across several reconstructive applications. Further development and implementation of these computational methods requires technique and device standardisation.

Diagnostic laparoscopy with indocyanine green fluorescence test for the evaluation of intestinal perfusion in abdominal blunt injury: a case report

BACKGROUND

The indocyanine green (ICG) fluorescence test has become a standard test in surgical procedures, facilitating the assessment of blood perfusion in real-time. While its utility in emergency surgeries for evaluating anastomotic blood supply is well-established, its application in trauma cases, especially those involving mesenteric hematoma, remains underexplored. Herein, we present a case to illustrate the efficacy of the ICG fluorescence test in such scenarios.

CASE PRESENTATION

A 51-year-old man with uncontrolled hypertension suffered blunt abdominal trauma following a motor vehicle accident. We used the intra-operative ICG fluorescence test to chart the surgical plan for the patient. A combination of diagnostic laparoscopy with ICG fluorescence testing effectively excluded bowel ischemia, leading to the avoidance of intestinal resection and the need for a temporary ostomy. The patient resumed enteral nutrition.

CONCLUSIONS

Our case underscores the efficacy of ICG fluorescence testing in assessing bowel viability and guiding surgical strategies in trauma patients with mesenteric hematoma. By facilitating real-time visualization of blood perfusion, ICG testing enables the adoption of conservative treatments in patients who would traditionally require more invasive surgical interventions, with minimal effect on operation time and cost.

Real time organ hypoperfusion detection using Indocyanine Green in a piglet model

BACKGROUND

Preserving sufficient oxygen supply to the tissue is fundamental for maintaining organ function. However, our ability to identify those at risk and promptly recognize tissue hypoperfusion during abdominal surgery is limited. To address this problem, we aimed to develop a new method of perfusion monitoring that can be used during surgical procedures and aid surgeons' decision-making.

METHODS

In this experimental porcine study, thirteen subjects were randomly assigned one organ of interest [stomach (n = 3), ascending colon (n = 3), rectum (n = 3), and spleen (n = 3)]. After baseline perfusion recordings, using high-frequency, low-dose bolus injections with weight-adjusted (0.008 mg/kg) ICG, organ-supplying arteries were manually and completely occluded leading to hypoperfusion of the target organ. Continuous organ perfusion monitoring was performed throughout the experimental conditions.

RESULTS

After manual occlusion of pre-selected organ-supplying arteries, occlusion of the peripheral arterial supply translated in an immediate decrease in oscillation signal in most organs (3/3 ventricle, 3/3 ascending colon, 3/3 rectum, 2/3 spleen). Occlusion of the central arterial supply resulted in a further decrease or complete disappearance of the oscillation curves in the ventricle (3/3), ascending colon (3/3), rectum (3/3), and spleen (1/3).

CONCLUSION

Continuous organ-perfusion monitoring using a high-frequency, low-dose ICG bolus regimen can detect organ hypoperfusion in real-time.

Quantitative analysis of intestinal perfusion with indocyanine green (ICG) and methylene blue (MB) using a single clinically approved fluorescence imaging system: a demonstration in a porcine model

BACKGROUND

Near-infrared fluorescence (NIRF) angiography with intraoperative administration of indocyanine green (ICG) has rapidly disseminated in clinical practice. Another clinically approved, and widely available dye, methylene blue (MB), has up to now not been used for this purpose. Recently, we demonstrated promising results for the real-time evaluation of intestinal perfusion using this dye. The primary aim of this study was to perform a quantitative analysis of bowel perfusion assessment for both ICG and MB.

METHODS

Four mature female Landrace pigs underwent laparotomy under general anesthesia. An ischemic bowel loop with five regions of interest (ROIs) with varying levels of perfusion was created in each animal. An intravenous (IV) injection of 0.25 mg/kg-0.50 mg/kg MB was administered after 10 min, followed by NIRF imaging in MB mode and measurement of local lactate levels in all corresponding ROIs. This procedure was repeated in ICG mode (IV dose of 0.2 mg/kg) after 60 min. The quest spectrum fluorescence camera (Quest Medical Imaging, Middenmeer, The Netherlands) was used for NIRF imaging of both MB and ICG.

RESULTS

Intraoperative NIRF imaging of bowel perfusion assessment with MB and ICG was successful in all studied animals. Ingress (i/s) levels were calculated and correlated with local lactate levels. Both MB and ICG ingress values showed a significant negative correlation (r = - 0.7709; p =  < 0.001; r = - 0.5367, p = 0.015, respectively) with local lactate levels. This correlation was stronger for MB compared to ICG, although ICG analysis showed higher absolute ingress values.

CONCLUSION

Our fluorescence quantification analysis validates the potential to use MB for bowel perfusion assessment besides the well-known and widely used ICG. Further human studies are necessary to translate our findings to clinical applications.

Perfusion Mapping of Flaps Using Indocyanine Green Fluorescence Angiography and Laser Speckle Contrast Imaging

Background

Indocyanine green fluorescence angiography (ICG-FA) is often used for assessing tissue circulation in reconstructive surgery. Indocyanine green (ICG) is injected intravenously and visualized in the tissue with an infrared camera. The information is used to plan the surgery, for example, in free flap breast reconstructions. Laser speckle contrast imaging (LSCI) is another method that uses laser to assess tissue perfusion in the skin. Unlike ICG-FA, LSCI is noninvasive and may therefore have an advantaged compared with ICG-FA. The aim of this study was to evaluate the correlation between information obtained from these two techniques.

Methods

Five deep inferior epigastric perforator patients were included. The flaps were assessed with LSCI and ICG-FA. For LSCI, the perfusion was calculated in 32 regions of interest. For ICG-FA, the maximum slope and area under curve (AUC) were calculated based on average pixel intensity data.

Results

Large variations in maximum slope values could be seen between flaps, whereas AUC had lower variability within the same flap and between flaps. Pearson rank correlation comparing average perfusion (LSCI) and AUC (ICG-FA) showed a correlation between the values (r = 0.55, P < 0.0001). No significant correlation was observed between perfusion and maximum slope (r = 0.11, P = 0.18).

Conclusions

There is a significant correlation between data obtained using LSCI and ICG-FA, when ICG-FA data are presented as AUC of the ICG-FA intensity curve. Maximum slope lacks significant correlation with flap data obtained with LSCI. The study indicates that LSCI may be used in reconstructive surgery to assess tissue circulation in a way similar to ICG-FA.

Clinical and computational development of a patient-calibrated ICGFA bowel transection recommender

INTRODUCTION

Intraoperative indocyanine green fluorescence angiography (ICGFA) aims to reduce colorectal anastomotic complications. However, signal interpretation is inconsistent and confounded by patient physiology and system behaviours. Here, we demonstrate a proof of concept of a novel clinical and computational method for patient calibrated quantitative ICGFA (QICGFA) bowel transection recommendation.

METHODS

Patients undergoing elective colorectal resection had colonic ICGFA both immediately after operative commencement prior to any dissection and again, as usual, just before anastomotic construction. Video recordings of both ICGFA acquisitions were blindly quantified post hoc across selected colonic regions of interest (ROIs) using tracking-quantification software and computationally compared with satisfactory perfusion assumed in second time-point ROIs, demonstrating 85% agreement with baseline ICGFA. ROI quantification outputs detailing projected perfusion sufficiency-insufficiency zones were compared to the actual surgeon-selected transection/anastomotic construction site for left/right-sided resections, respectively. Anastomotic outcomes were recorded, and tissue lactate was also measured in the devascularised colonic segment in a subgroup of patients. The novel perfusion zone projections were developed as full-screen recommendations via overlay heatmaps.

RESULTS

No patient suffered intra- or early postoperative anastomotic complications. Following computational development (n = 14) the software recommended zone (ROI) contained the expert surgical site of transection in almost all cases (Jaccard similarity index 0.91) of the nine patient validation series. Previously published ICGFA time-series milestone descriptors correlated moderately well, but lactate measurements did not. High resolution augmented reality heatmaps presenting recommendations from all pixels of the bowel ICGFA were generated for all cases.

CONCLUSIONS

By benchmarking to the patient's own baseline perfusion, this novel QICGFA method could allow the deployment of algorithmic personalised NIR bowel transection point recommendation in a way fitting existing clinical workflow.

Quantification of fluorescence angiography for visceral perfusion assessment: measuring agreement between two software algorithms

BACKGROUND

Indocyanine green fluorescence angiography (ICG-FA) may reduce perfusion-related complications of gastrointestinal anastomosis. Software implementations for quantifying ICG-FA are emerging to overcome a subjective interpretation of the technology. Comparison between quantification algorithms is needed to judge its external validity. This study aimed to measure the agreement for visceral perfusion assessment between two independently developed quantification software implementations.

METHODS

This retrospective cohort analysis included standardized ICG-FA video recordings of patients who underwent esophagectomy with gastric conduit reconstruction between August 2020 until February 2022. Recordings were analyzed by two quantification software implementations: AMS and CPH. The quantitative parameter used to measure visceral perfusion was the normalized maximum slope derived from fluorescence time curves. The agreement between AMS and CPH was evaluated in a Bland-Altman analysis. The relation between the intraoperative measurement of perfusion and the incidence of anastomotic leakage was determined for both software implementations.

RESULTS

Seventy pre-anastomosis ICG-FA recordings were included in the study. The Bland-Altman analysis indicated a mean relative difference of + 58.2% in the measurement of the normalized maximum slope when comparing the AMS software to CPH. The agreement between AMS and CPH deteriorated as the magnitude of the measured values increased, revealing a proportional (linear) bias (R2 = 0.512, p < 0.001). Neither the AMS nor the CPH measurements of the normalized maximum slope held a significant relationship with the occurrence of anastomotic leakage (median of 0.081 versus 0.074, p = 0.32 and 0.041 vs 0.042, p = 0.51, respectively).

CONCLUSION

This is the first study to demonstrate technical differences in software implementations that can lead to discrepancies in ICG-FA quantification in human clinical cases. The possible variation among software-based quantification methods should be considered when interpreting studies that report quantitative ICG-FA parameters and derived thresholds, as there may be a limited external validity.

Indocyanine green: A novel marker for assessment of graft quality during ex situ normothermic machine perfusion of human livers

BACKGROUND

Ex situ machine perfusion facilitates the assessment of livers prior to transplantation. However, currently available markers of liver function poorly predict long-term graft function. Indocyanine green (ICG) is a liver-specific dye which, although common in vivo, has never been comprehensively evaluated for the assessment of graft quality during ex situ machine perfusion. This study aimed to assess the utility of ICG in the ex situ setting.

METHODS

Using a customized long-term perfusion system, human livers that were not suitable for transplantation were perfused using a red cell-based perfusate. ICG was delivered into the perfusate on days 0, 1, and 4 to assess ICG clearance (spectrophotometric absorbance at 805 nm) and ICG fluorescence (near-infrared camera).

RESULTS

Sixteen partial livers were perfused for a median duration of 172 h (7.2 days). On day 0, the median ICG perfusate disappearance rate (PDR) was 7.5%/min and the median ICG retention at 15 min was 9.9%. Grafts that survived ≥7 days had a significantly higher median ICG PDR on day 0 (14.5%/min vs. 6.5%/min, p = 0.005) but not on days 1 or 4. ICG perfusion demonstrated that long-surviving grafts had a significantly lower median red-value (89.8 vs. 118.6, p = 0.011) and a significantly lower median blue-value (12.9 vs. 22.6, p = 0.045) than short-surviving grafts.

CONCLUSION

ICG is a novel marker for the assessment of liver function during ex situ normothermic machine perfusion. ICG PDR and quantitative ICG perfusion can distinguish between long- and short-surviving grafts and demonstrate the utility of ICG in the assessment of graft quality prior to transplant.

Blinded Intraoperative Quantitative Indocyanine Green Metrics Associate With Intestinal Margin Acceptance in Colorectal Surgery

BACKGROUND

Indocyanine green is a useful tool in colorectal surgery. Quantitative values may enhance and standardize its application.

OBJECTIVE

To determine whether quantitative indocyanine green metrics correlate with standard subjective indocyanine green perfusion assessment in acceptance or rejection of anastomotic margins.

DESIGN

Prospective single-arm, single-institution cohort study. Surgeons viewed subjective indocyanine green images but were blinded to quantitative indocyanine green metrics.

SETTING

Tertiary academic center.

PATIENTS

Adults undergoing planned intestinal resection.

MAIN OUTCOME MEASURES

Accepted perfusion and rejected perfusion of the intestinal margin were defined by the absence or presence of ischemia by subjective indocyanine green and gross inspection. The primary outcomes included quantitative indocyanine green values, maximum fluorescence, and time-to-maximum fluorescence in accepted compared to rejected perfusion. Secondary outcomes included maximum fluorescence and time-to-maximum fluorescence values in anastomotic leak.

RESULTS

There were 89 perfusion assessments comprising 156 intestinal segments. Nine segments were subjectively assessed to have poor perfusion by visual inspection and subjective indocyanine green. Maximum fluorescence (% intensity) exhibited higher intensity in accepted perfusion (accepted perfusion 161% [82%-351%] vs rejected perfusion 63% [10%-76%]; p = 0.03). Similarly, time-to-maximum fluorescence (seconds) was earlier in accepted perfusion compared to rejected perfusion (10 seconds [1-40] vs 120 seconds [90-120]; p < 0.01). Increased BMI was associated with higher maximum fluorescence. Anastomotic leak did not correlate with maximum fluorescence or time-to-maximum fluorescence.

LIMITATIONS

Small cohort study, not powered to measure the association between quantitative indocyanine green metrics and anastomotic leak.

CONCLUSIONS

We demonstrated that blinded quantitative values reliably correlate with subjective indocyanine green perfusion assessment. Time-to-maximum intensity is an important metric in perfusion evaluation. Quantitative indocyanine green metrics may enhance intraoperative intestinal perfusion assessment. Future studies may attempt to correlate quantitative indocyanine green values with anastomotic leak. See Video Abstract .

LAS MTRICAS CUANTITATIVAS INTRAOPERATORIAS CIEGAS DEL VERDE DE INDOCIANINA SE ASOCIAN CON LA ACEPTACIN DEL MARGEN INTESTINAL EN LA CIRUGA COLORRECTAL

ANTECEDENTES:El verde de indocianina es una herramienta útil en la cirugía colorrectal. Los valores cuantitativos pueden mejorar y estandarizar su aplicación.OBJETIVO:Determinar si las métricas cuantitativas de verde de indocianina se correlacionan con la evaluación subjetiva estándar de perfusión de verde de indocianina en la aceptación o rechazo de los márgenes anastomóticos.DISEÑO:Estudio de cohorte prospectivo de un solo brazo y de una sola institución. Los cirujanos vieron imágenes subjetivas de verde de indocianina, pero no conocían las métricas cuantitativas de verde de indocianina.AJUSTE:Centro académico terciario.PACIENTES:Adultos sometidos a resección intestinal planificada.PRINCIPALES MEDIDAS DE RESULTADO:La perfusión aceptada y la perfusión rechazada del margen intestinal se definieron por la ausencia o presencia de isquemia mediante verde de indocianina subjetiva y la inspección macroscópica. Los resultados primarios fueron los valores cuantitativos de verde de indocianina, la fluorescencia máxima y el tiempo hasta la fluorescencia máxima en la perfusión aceptada en comparación con la rechazada. Los resultados secundarios incluyeron la fluorescencia máxima y el tiempo hasta alcanzar los valores máximos de fluorescencia en la fuga anastomótica.RESULTADOS:Se realizaron 89 evaluaciones de perfusión, comprendiendo 156 segmentos intestinales. Se evaluó subjetivamente que 9 segmentos tenían mala perfusión mediante inspección visual y verde de indocianina subjetiva. La fluorescencia máxima (% de intensidad) mostró una mayor intensidad en la perfusión aceptada [Perfusión aceptada 161% (82-351) vs Perfusión rechazada 63% (10-76); p = 0,03]. De manera similar, el tiempo hasta la fluorescencia máxima (segundos) fue más temprano en la perfusión aceptada en comparación con la rechazada [10 s (1-40) frente a 120 s (90-120); p < 0,01]. Aumento del índice de masa corporal asociado con una fluorescencia máxima más alta. La fuga anastomótica no se correlacionó con la fluorescencia máxima ni con el tiempo hasta la fluorescencia máxima.LIMITACIONES:Estudio de cohorte pequeño, sin poder para medir la asociación entre las mediciones cuantitativas del verde de indocianina y la fuga anastomótica.CONCLUSIÓN:Demostramos que los valores cuantitativos ciegos se correlacionan de manera confiable con la evaluación subjetiva de la perfusión de verde de indocianina. El tiempo hasta la intensidad máxima es una métrica importante en la evaluación de la perfusión. Las métricas cuantitativas de verde de indocianina pueden mejorar la evaluación de la perfusión intestinal intraoperatoria. Los estudios futuros pueden intentar correlacionar los valores cuantitativos de verde de indocianina con la fuga anastomótica. (Traducción-Dr. Yolanda Colorado).

Impact of standardising indocyanine green fluorescence angiography technique for visual and quantitative interpretation on interuser variability in colorectal surgery

AIM/BACKGROUND

Intra-operative colonic perfusion assessment via indocyanine green fluorescence angiography (ICGFA) aims to address malperfusion-related anastomotic complications; however, its interpretation suffers interuser variability (IUV), especially early in ICGFA experience. This work assesses the impact of a protocol developed for both operator-based judgement and computational development on interpretation consistency, focusing on senior surgeons yet to start using ICGFA.

METHODS

Experienced and junior gastrointestinal surgeons were invited to complete an ICGFA-experience questionnaire. They subsequently interpreted nine operative ICGFA videos regarding perfusion sufficiency of a surgically prepared distal colon during laparoscopic anterior resection by indicating their preferred site of proximal transection using an online annotation platform (mindstamp.com). Six ICGFA videos had been prepared with a clinical standardisation protocol controlling camera and patient positioning of which three each had monochrome near infrared (NIR) and overlay display. Three others were non-standardised controls with synchronous NIR and overlay picture-in-picture display. Differences in transection level between different cohorts were assessed for intraclass correlation coefficient (ICC) via ImageJ and IBM SPSS.

RESULTS

58 clinicians (12 ICGFA experts, 46 ICGFA inexperienced of whom 23 were either finished or within one year of finishing training and 23 were junior trainees) participated as per power calculations. 63% felt that ICGFA should be routinely deployed with 57% believing interpretative competence requires 11-50 cases. Transection level concordance was generally good (ICC = 0.869) across all videos and levels of expertise (0.833-0.915). However, poor agreement was evident with the standardised protocol videos for overlay presentation (0.208-0.345). Similarly, poor agreement was seen for the monochrome display (0.392-0.517), except for those who were trained but ICG inexperienced (0.877) although even here agreement was less than with unstandardised videos (0.943).

CONCLUSION

Colorectal ICGFA acquisition and display standardisation impacts IUV with this specific protocol tending to diminish surgeon interpretation consistency. ICGFA video recording for computational development may require dedicated protocols.

Indocyanine green (ICG) fluorescence-enhanced applications in pediatric surgery

The breadth of pediatric surgical practice and variety of anatomic anomalies that characterize surgical disease in children and neonates require a unique level of operative mastery and versatility. Intraoperative navigation of small, complex, and often abnormal anatomy presents a particular challenge for pediatric surgeons. Clinical experience with fluorescent tissue dye, specifically indocyanine green (ICG), is quickly gaining widespread incorporation into adult surgical practice as a safe, non-toxic means of accurately visualizing tissue perfusion, lymphatic flow, and biliary anatomy to enhance operative speed, safety, and patient outcomes. Experience in pediatric surgery, however, remains limited. ICG-fluorescence guided surgery is poised to address the challenges of pediatric and neonatal operations for a growing breadth of surgical pathology. Fluorescent angiography has permitted intraoperative visualization of colorectal flap perfusion for complex pelvic reconstruction and anastomotic perfusion after esophageal atresia repair, while its hepatic absorption and biliary excretion has made it an excellent agent for delineating the dissection plane in the Kasai portoenterostomy and identifying both primary and metastatic hepatoblastoma lesions. Subcutaneous and intra-lymphatic ICG injection can identify iatrogenic chylous leaks and improved yields in sentinel lymph node biopsies. ICG-guided surgery holds promise for more widespread use in pediatric surgical conditions, and continued evaluation of efficacy will be necessary to better inform clinical practice and identify where to focus and develop this technical resource.

Indocyanine Green Tattooing During Colonoscopy as a Guide to Laparoscopic Colorectal Cancer Surgery: A Literature Review

BACKGROUND

Endoscopic tattooing of colorectal lesions has been performed employing several markers. The indocyanine green (ICG) that uses near infrared fluorescence technology, has been recently adopted in laparoscopic colorectal cancer surgery. This study aims to systematically review the international literature to validate the ICG in laparoscopic colorectal surgery, in order to include the ICG in the therapeutic protocol.

METHODS

Following AMSTAR 2 criteria, we performed a systematic review to evaluate the use of green indocyanine as a marker for preoperative endoscopic tattooing and for lymph nodes mapping. The study selection was conducted using the PubMed database from January 1989 to July 2022.

RESULTS

We identified 25 eligible studies. 13 based on fluorescent tumor localization in laparoscopic colorectal surgery using ICG while 12 of them reported the lymphatic road mapping and sentinel node identification by ICG using a near-infrared camera system. One study analyzed both topics.

CONCLUSIONS

In laparoscopic colorectal cancer surgery indocyanine green can be used to localize fluorescent tumors and mapping fluorescence lymph node. The use of ICG appears to be a valid and safe technique that helps the surgeon to achieve a better oncological radicality. However, the protocols need to be clarified by further studies.

Semi-automatic standardized analysis method to objectively evaluate near-infrared fluorescent dyes in image-guided surgery

Significance

Near-infrared fluorescence imaging still lacks a standardized, objective method to evaluate fluorescent dye efficacy in oncological surgical applications. This results in difficulties in translation between preclinical to clinical studies with fluorescent dyes and in the reproduction of results between studies, which in turn hampers further clinical translation of novel fluorescent dyes.

Aim

Our aim is to develop and evaluate a semi-automatic standardized method to objectively assess fluorescent signals in resected tissue.

Approach

A standardized imaging procedure was designed and quantitative analysis methods were developed to evaluate non-targeted and tumor-targeted fluorescent dyes. The developed analysis methods included manual selection of region of interest (ROI) on white light images, automated fluorescence signal ROI selection, and automatic quantitative image analysis. The proposed analysis method was then compared with a conventional analysis method, where fluorescence signal ROIs were manually selected on fluorescence images. Dice similarity coefficients and intraclass correlation coefficients were calculated to determine the inter- and intraobserver variabilities of the ROI selections and the determined signal- and tumor-to-background ratios.

Results

The proposed non-targeted fluorescent dyes analysis method showed statistically significantly improved variabilities after application on indocyanine green specimens. For specimens with the targeted dye SGM-101, the variability of the background ROI selection was statistically significantly improved by implementing the proposed method.

Conclusion

Semi-automatic methods for standardized quantitative analysis of fluorescence images were successfully developed and showed promising results to further improve the reproducibility and standardization of clinical studies evaluating fluorescent dyes.

[Prospects of qualitative and quantitative assessment of bowel perfusion by fluorescent angiography with indocyanine green in colorectal surgery. First experience]

OBJECTIVE

To assess the possibilities of fluorescent detection system in qualitative and quantitative assessment of bowel perfusion in colorectal resections.

MATERIAL AND METHODS

From May to August 2023, a single-center pilot cross-sectional unblinded study with inclusion of 18 patients with colon cancer (of left-sided - 12, of right-sided - 6, mean age - 72.9 years, m/w - 61/39%) was conducted. All patients underwent laparoscopic colorectal resections with extracorporeal stage of bowel transection. The evaluation of the bowel's ICG perfusion was conducted to assist in decision making about the level of its resection. Qualitative (visual) assessment was carried out in all 18 patients, in one patient twice, quantitative assessment of perfusion was conducted in 8 patients (left-sided resections - 6, right-sided hemicolectomy - 2). The qualitative evaluation was performed in real time on the analysis of the color gradient. The time parameters and fluorescence intensity at different level proximally and distally from the resection line were quantitatively estimated: Tstart - time of occurrence of minimal fluorescence in the areas of interest after the ICG injection (sec); Tmax - time to achieve maximum fluorescence intensity after the ICG injection (sec); Tmax-start - time interval between Tstart and Tmax, Imax - level of maximum fluorescence intensity (I).

RESULTS

Visual qualitative analysis of fluorescence revealed unsatisfactory perfusion characteristics (black, dark-gray color) in the area planned by the surgeon to anastomose the bowel in 3 of 18 patients (16.6%). When analyzing the quantitative data of this group of patients, there was a 2-6-fold decrease in Imax level, and one patient had an increase in Tmax-start at the level of intended resection compared to the bowel's sections in the favorable zone. In all cases, the final bowel transection was conducted in the area of good perfusion. There was no clinical evidence of anastomotic dehiscence in the study group.

CONCLUSION

Intraoperative evaluation of bowel perfusion is an important component of safe anastomosis formation in colorectal surgery. The use of ICG-FA allows to conduct qualitative and quantitative assessment of tissue perfusion of the bowel in order to assist in making intraoperative decisions. Quantitative evaluation of fluorescence provides more objective information about perfusion parameters. Imax and Tmax-start are the most promising quantitative indicators of local bowel's perfusion. Nevertheless, the precise interpretation of the quantitative indicators of ICG perfusion needs to be clarified.

Inferior Mesenteric Artery Ligation Level in Rectal Cancer Surgery beyond Conventions: A Review

Within the intricate field of rectal cancer surgery, the contentious debate over the optimal level of ligation of the inferior mesenteric artery (IMA) persists as an ongoing discussion, influencing surgical approaches and patient outcomes. This narrative review incorporates historical perspectives, technical considerations, and functional as well as oncological outcomes, addressing key questions related to anastomotic leakage risks, genitourinary function, and oncological concerns, providing a more critical understanding of the well-known inconclusive evidence. Beyond the dichotomy of high versus low tie, it navigates the complexities of colorectal cancer surgery with a fresh perspective, posing a transformative question: "Is low tie ligation truly reproducible?" Considering a multidimensional approach that enhances patient outcomes by integrating the surgeon, patient, technique, and technology, instead of a rigid and categorical statement, we argued that a balanced response to this challenging question may require compromise.

Fluorescence-guided colorectal surgery: applications, clinical results, and protocols

In recent years, the rise of minimally invasive surgery has driven the development of surgical devices. Indocyanine green (ICG) fluorescence imaging is receiving increased attention in colorectal surgery for improved intraoperative visualization and decision-making. ICG, approved by the U.S. Food and Drug Administration in 1959, rapidly binds to plasma proteins and is primarily intravascular. ICG absorption of near-infrared light (750-800 nm) and emission as fluorescence (830 nm) when bound to tissue proteins enhances deep tissue visualization. Applications include assessing anastomotic perfusion, identifying sentinel lymph nodes, and detecting colorectal cancer metastasis. However, standardized protocols and research on clinical outcomes remain limited. This study explores ICG's role, advantages, disadvantages, and potential clinical impact in colorectal surgery.

Blood Perfusion Assessment by Indocyanine Green Fluorescence Imaging for Minimally Invasive Rectal Cancer Surgery (EssentiAL trial): A Randomized Clinical Trial

OBJECTIVE

The aim of the present randomized controlled trial was to evaluate the superiority of indocyanine green fluorescence imaging (ICG-FI) in reducing the rate of anastomotic leakage in minimally invasive rectal cancer surgery.

BACKGROUND

The role of ICG-FI in anastomotic leakage in minimally invasive rectal cancer surgery is controversial according to the published literature.

METHODS

This randomized, open-label, phase 3, trial was performed at 41 hospitals in Japan. Patients with clinically stage 0-III rectal carcinoma less than 12 cm from the anal verge, scheduled for minimally invasive sphincter-preserving surgery were preoperatively randomly assigned to receive a blood flow evaluation by ICG-FI (ICG+ group) or no blood flow evaluation by ICG-FI (ICG- group). The primary endpoint was the anastomotic leakage rate (grade A+B+C, expected reduction rate of 6%) analyzed in the modified intention-to-treat population.

RESULTS

Between December 2018 and February 2021, a total of 850 patients were enrolled and randomized. After the exclusion of 11 patients, 839 were subject to the modified intention-to-treat population (422 in the ICG+ group and 417 in the ICG- group). The rate of anastomotic leakage (grade A+B+C) was significantly lower in the ICG+ group (7.6%) than in the ICG- group (11.8%) (relative risk, 0.645; 95% confidence interval 0.422-0.987; P =0.041). The rate of anastomotic leakage (grade B+C) was 4.7% in the ICG+ group and 8.2% in the ICG- group ( P =0.044), and the respective reoperation rates were 0.5% and 2.4% ( P =0.021).

CONCLUSIONS

Although the actual reduction rate of anastomotic leakage in the ICG+ group was lower than the expected reduction rate and ICG-FI was not superior to white light, ICG-FI significantly reduced the anastomotic leakage rate by 4.2%.

Indocyanine green dye and its application in gastrointestinal surgery: The future is bright green

Indocyanine green (ICG) is a water-soluble fluorescent dye that is minimally toxic and widely used in gastrointestinal surgery. ICG facilitates anatomical identification of structures (e.g., ureters), assessment of lymph nodes, biliary mapping, organ perfusion and anastomosis assessment, and aids in determining the adequacy of oncological margins. In addition, ICG can be conjugated to artificially created antibodies for tumour markers, such as carcinoembryonic antigen for colorectal, breast, lung, and gastric cancer, prostate-specific antigen for prostate cancer, and cancer antigen 125 for ovarian cancer. Although ICG has shown promising results, the optimization of patient factors, dye factors, equipment, and the method of assessing fluorescence intensity could further enhance its utility. This review summarizes the clinical application of ICG in gastrointestinal surgery and discusses the emergence of novel dyes such as ZW-800 and VM678 that have demonstrated appropriate pharmacokinetic properties and improved target-to-background ratios in animal studies. With the emergence of robotic technology and the increasing reporting of ICG utility, a comprehensive review of clinical application of ICG in gastrointestinal surgery is timely and this review serves that aim.

Application of fluorescence-guided surgery in the acute care setting: a systematic literature review

PURPOSE

Fluorescence-based imaging has found application in several fields of elective surgery, but there is still a lack of evidence in the literature about its use in emergency setting. The present review critically summarizes currently available applications and limitations of indocyanine green (ICG) fluorescence in abdominal emergencies including acute cholecystitis, mesenteric ischemia, and trauma surgery.

METHODS

A systematic review was performed according to the PRISMA statement identifying articles about the use of ICG fluorescence in the management of the most common general surgery emergency. Only studies focusing on the use of ICG fluorescence for the management of acute surgical conditions in adults were included.

RESULTS

Thirty-six articles were considered for qualitative analysis. The most frequent disease was occlusive or non-occlusive mesenteric ischemia followed by acute cholecystitis. Benefits from using ICG for acute cholecystitis were reported in 48% of cases (clear identification of biliary structures and a safer surgical procedure). In one hundred and twenty cases that concerned the use of ICG for occlusive or non-occlusive mesenteric ischemia, ICG injection led to a modification of the surgical decision in 44 patients (36.6%). Three studies evaluated the use of ICG in trauma patients to assess the viability of bowel or parenchymatous organs in abdominal trauma, to evaluate the perfusion-related tissue impairment in extremity or craniofacial trauma, and to reassess the efficacy of surgical procedures performed in terms of vascularization. ICG injection led to a modification of the surgical decision in 50 patients (23.9%).

CONCLUSION

ICG fluorescence is a safe and feasible tool also in an emergency setting. There is increasing evidence that the use of ICG fluorescence during abdominal surgery could facilitate intra-operative decision-making and improve patient outcomes, even in the field of emergency surgery.

Intraoperative Utilization of Indocyanine Green (ICG) Dye for the Assessment of Ovarian Perfusion-Case Report and Review of the Literature

The assessment of ovarian perfusion after detorsion is crucial in the surgical management of patients with ovarian torsion. In current routine clinical practice, the surgical decision (preservation of the ovary versus oophorectomy) is based on the subjective impression of the surgeon. Intraoperative indocyanine green (ICG) angiography has been shown to sufficiently reflect tissue perfusion with a potential impact on the surgical procedure. Currently, there are only sparse data available on the utilization of ICG in the surgical treatment of ovarian torsion. Here, we describe the successful intraoperative use of ICG in a 17-year-old female patient with ovarian torsion who underwent ovary-preserving surgery. Further, a systematic literature review was performed. Based on the data available to date, the use of ICG in the surgical treatment of ovarian torsion is feasible and safe. The extent to which this might reduce the necessity for oophorectomy has to be evaluated in further investigations.

Quantification of indocyanine green near-infrared fluorescence bowel perfusion assessment in colorectal surgery

BACKGROUND

Indocyanine green near-infrared fluorescence bowel perfusion assessment has shown its potential benefit in preventing anastomotic leakage. However, the surgeon's subjective visual interpretation of the fluorescence signal limits the validity and reproducibility of the technique. Therefore, this study aimed to identify objective quantified bowel perfusion patterns in patients undergoing colorectal surgery using a standardized imaging protocol.

METHOD

A standardized fluorescence video was recorded. Postoperatively, the fluorescence videos were quantified by drawing contiguous region of interests (ROIs) on the bowel. For each ROI, a time-intensity curve was plotted from which perfusion parameters (n = 10) were derived and analyzed. Furthermore, the inter-observer agreement of the surgeon's subjective interpretation of the fluorescence signal was assessed.

RESULTS

Twenty patients who underwent colorectal surgery were included in the study. Based on the quantified time-intensity curves, three different perfusion patterns were identified. Similar for both the ileum and colon, perfusion pattern 1 had a steep inflow that reached its peak fluorescence intensity rapidly, followed by a steep outflow. Perfusion pattern 2 had a relatively flat outflow slope immediately followed by its plateau phase. Perfusion pattern 3 only reached its peak fluorescence intensity after 3 min with a slow inflow gradient preceding it. The inter-observer agreement was poor-moderate (Intraclass Correlation Coefficient (ICC): 0.378, 95% CI 0.210-0.579).

CONCLUSION

This study showed that quantification of bowel perfusion is a feasible method to differentiate between different perfusion patterns. In addition, the poor-moderate inter-observer agreement of the subjective interpretation of the fluorescence signal between surgeons emphasizes the need for objective quantification.

Correlation between Indocyanine Green Fluorescence Angiography and Laser Speckle Contrast Imaging in a Flap Model

Background

Indocyanine green fluorescence angiography (ICG-FA) is used to assess tissue intraoperatively in reconstructive surgery. This requires an intra-venous dye injection for each assessment. This is not necessary in laser speckle contrast imaging (LSCI); therefore, this method may be better suited for tissue evaluation. To determine this, we compared the two methods in a porcine flap model.

Methods

One random and one pedicled flap were raised on each buttock of six animals. They were assessed with LSCI at baseline, when raised (T0), at 30 minutes (T30) and with ICG-FA at T0 and T30. Regions of interest (ROI) were chosen along the flap axis. Perfusion, measured as perfusion units (PU) in the LSCI assessment and pixel-intensity for the ICG-FA video uptake, was calculated in the ROI. Correlation was calculated between PU and pixel-intensity measured as time to peak (TTP) and area under curve for 60 seconds (AUC60).

Results

Correlation between LSCI and AUC60 for the ICG-FA in corresponding ROI could be seen in all flaps at all time points. The correlation was higher for T0 (r=0.7 for random flap and r=0.6 for pedicled flap) than for T30 (r=0.57 for random flap and r=0.59 for pedicled flap). Even higher correlation could be seen PU and TTP (T0: random flap r=-0.8 and pedicled flap r=0.76. T30: random flap r=-0.8 and pedicled flap r=0.71).

Conclusion

There is a correlation between PU from LSCI and TTP and AUC60 for ICG-FA, indicating that LSCI could be considered for intraoperative tissue assessment.

Fluorescent ICG angiography in laparoscopic rectal resection - a randomized controlled trial. Preliminary report

Introduction

Anastomotic leakage is one of the most dangerous complications after rectal surgery. It can cause systemic complications, reduce the quality of life and worsen the results of oncological treatment. One of the causes of anastomotic leak is insufficient blood supply to the anastomosis. Intraoperative infrared angiography with indocyanine green (ICG) is expected to improve the assessment of intestinal perfusion and thus prevent anastomotic leakage.

Aim

To present the results of the use of ICG intraoperative angiography during rectal surgery in the prevention of anastomotic leakage.

Material and methods

The study included 76 patients undergoing rectal cancer surgery. Patients were randomized to 2 groups: Group I - 41 patients with ICG intraoperative angiography; and Group II - 35 patients without ICG imaging. Anastomotic leak, length of hospitalization, and complication rate were compared.

Results

Group I patients received intravenous ICG before the anastomosis. Average time of intestinal wall contrasting was 42 s (22-65 s). Average ICG procedure time was 4 min (3.2% of total time of surgery). Three (7.3%) patients after angiography revealed intestinal ischemia requiring widened resection. No anastomotic leak was found post-operatively, and no side effects were observed after administration of ICG. In group II, 3 (8.6%) anastomotic leakages were diagnosed, 2 of which required reoperation.

Conclusions

Intraoperative angiography with ICG in near-infrared light is a safe and effective method of assessing intestinal perfusion. ICG angiography may change the surgical plan and reduce the risk of anastomotic leakage. It is necessary to continue the study until the assumed number of patients is reached.

Real-time quantification of bowel perfusion using Laparoscopic Laser Speckle Contrast Imaging (LSCI) in a porcine model

BACKGROUND/PURPOSE

Real-time quantification of tissue perfusion can improve intraoperative surgical decision making. Here we demonstrate the utility of Laser Speckle Contrast Imaging as an intra-operative tool that quantifies real-time regional differences in intestinal perfusion and distinguishes ischemic changes resulting from arterial/venous obstruction.

METHODS

Porcine models (n = 3) consisted of selectively devascularized small bowel loops that were used to measure the perfusion responses under conditions of control/no vascular occlusion, arterial inflow occlusion, and venous outflow occlusion using laser speckle imaging and indocyanine green fluoroscopy. Laser Speckle was also used to assess perfusion differences between small bowel antimesenteric-antimesenteric and mesenteric-mesenteric anastomoses. Perfusion quantification was measured in relative perfusion units calculated from the laser speckle perfusion heatmap.

RESULTS

Laser Speckle distinguished between visually identified perfused, watershed, and ischemic intestinal segments with both color heatmap and quantification (p < .00001). It detected a continuous gradient of relative intestinal perfusion as a function of distance from the stapled ischemic bowel edge. Strong positive linear correlation between relative perfusion units and changes in mean arterial pressure resulting from both arterial (R2 = .96/.79) and venous pressure changes (R2 = .86/.96) was observed. Furthermore, Laser Speckle showed that the antimesenteric anastomosis had a higher perfusion than mesenteric anastomosis (p < 0.01).

CONCLUSIONS

Laser Speckle Contrast Imaging provides objective, quantifiable tissue perfusion information in both color heatmap and relative numerical units. Laser Speckle can detect spatial/temporal differences in perfusion between antimesenteric and mesenteric borders of a bowel segment and precisely detect perfusion changes induced by progressive arterial/venous occlusions in real-time.

Indocyanine Green (ICG) and Colorectal Surgery: A Literature Review on Qualitative and Quantitative Methods of Usage

Background: Due to its many benefits, indocyanine green (ICG) has gained progressive popularity in operating rooms (ORs) globally. This literature review examines its qualitative and quantitative usage in surgical treatment. Method: Relevant terms were searched in five international databases (1. Pubmed, 2. Sciencedirect, 3. Scopus, 4. Oxfordjournals, 5. Reaxys) for a comprehensive literature review. The main benefits of using ICG in colorectal surgery are: intraoperative fluorescence angiography; fluorescence-guided lymph node involvement detection and the sentinel technique; the fluorescent emphasis of a minute liver tumour, counting just 200 tumour cells; facilitation of fistula diagnosis; and tumour tattooing. This methodology can also be used with quantitative characteristics such as maximum intensity, relative maximum intensity, and in-flow parameters such as time-to-peak, slope, and t1/2max. This article concludes that fluorescence surgery with ICG and near-infrared (NIR) light is a relatively new technology that improves anatomical and functional information, allowing more comprehensive and safer tumour removal and the preservation of important structures.

The Safe Values of Quantitative Perfusion Parameters of ICG Angiography Based on Tissue Oxygenation of Hyperspectral Imaging for Laparoscopic Colorectal Surgery: A Prospective Observational Study

BACKGROUND

Safe values for quantitative perfusion parameters of indocyanine green (ICG) angiography have not been fully defined, and interpretation remains at the surgeon's discretion. This prospective observational study aimed to establish the safe values for the quantitative perfusion parameters by comparing tissue oxygenation levels from HSI images in laparoscopic colorectal surgery.

METHODS

ICG angiography was performed using a laparoscopic near-infrared (NIR) camera system with ICG diluted in 10 mL of distilled water. For quantitative perfusion parameters, the changes in fluorescence intensity with perfusion times were analyzed to plot a time-fluorescence intensity graph. To assess real-time tissue oxygen saturation (StO2) in the colon, the TIVITA® Tissue System was utilized for hyperspectral imaging (HSI) acquisition. The StO2 levels were compared with the quantitative perfusion parameters derived from ICG angiography at corresponding points to define the safe range of ICG parameters reflecting good tissue oxygenation.

RESULTS

In the regression analysis, T1/2MAX, TMAX, slope, and NIR perfusion index were correlated with tissue oxygen saturation. Using this regression model, the cutoff values of quantitative perfusion parameters were calculated as T1/2MAX ≤ 10 s, TMAX ≤ 30 s, slope ≥ 5, and NIR perfusion index ≥50, which best reflected colon StO2 higher than 60%. Diagnostic values were analyzed to predict colon StO2 of 60% or more, and the ICG perfusion parameters T1/2MAX, TMAX, and perfusion TR showed high sensitivity values of 97% or more, indicating their ability to correctly identify cases with acceptable StO2.

CONCLUSION

The safe values for quantitative perfusion parameters derived from ICG angiography were T1/2MAX ≤ 10 s and TMAX ≤ 30 s, which were associated with colon tissue oxygenation levels higher than 60% in the laparoscopic colorectal surgery.

Quantification of Indocyanine Green Fluorescence Imaging in General, Visceral and Transplant Surgery

Near-infrared (NIR) imaging with indocyanine green (ICG) has proven to be useful in general, visceral, and transplant surgery. However, most studies have performed only qualitative assessments. Therefore, a systematic overview of all studies performing quantitative indocyanine green evaluation in general, visceral, and transplant surgeries should be conducted. Free term and medical subject heading (MeSH) term searches were performed in the Medline and Cochrane databases until October 2022. The main categories of ICG quantification were esophageal surgery (24.6%), reconstructive surgery (24.6%), and colorectal surgery (21.3%). Concordantly, anastomotic leak (41%) was the main endpoint, followed by the assessment of flap perfusion (23%) and the identification of structures and organs (14.8%). Most studies examined open surgery (67.6%) or laparoscopic surgery (23.1%). The analysis was mainly carried out using manufacturer software (44.3%) and open-source software (15.6%). The most frequently analyzed parameter was intensity over time for blood flow assessment, followed by intensity alone or intensity-to-background ratios for structure and organ identification. Intraoperative ICG quantification could become more important with the increasing impact of robotic surgery and machine learning algorithms for image and video analysis.

Anastomotic perfusion assessment with indocyanine green in robot-assisted low-anterior resection, a multicenter study of interobserver variation

BACKGROUND

Securing sufficient blood perfusion to the anastomotic area after low-anterior resection is a crucial factor in preventing anastomotic leakage (AL). Intra-operative indocyanine green fluorescent imaging (ICG-FI) has been suggested as a tool to assess perfusion. However, knowledge of inter-observer variation among surgeons in the interpretation of ICG-FI is sparse. Our primary objective was to evaluate inter-observer variation among surgeons in the interpretation of bowel blood-perfusion assessed visually by ICG-FI. Our secondary objective was to compare the results both from the visual assessment of ICG and from computer-based quantitative analyses of ICG-FI between patients with and without the development of AL.

METHOD

A multicenter study, including patients undergoing robot-assisted low anterior resection with stapled anastomosis. ICG-FI was evaluated visually by the surgeon intra-operatively. Postoperatively, recorded videos were anonymized and exchanged between centers for inter-observer evaluation. Time to visibility (TTV), time to maximum visibility (TMV), and time to wash-out (TWO) were visually assessed. In addition, the ICG-FI video-recordings were analyzed using validated pixel analysis software to quantify blood perfusion.

RESULTS

Fifty-five patients were included, and five developed clinical AL. Bland-Altman plots (BA plots) demonstrated wide inter-observer variation for visually assessed fluorescence on all parameters (TTV, TMV, and TWO). Comparing leak-group with no-leak group, we found no significant differences for TTV: Hazard Ratio; HR = 0.82 (CI 0.32; 2.08), TMV: HR = 0.62 (CI 0.24; 1.59), or TWO: HR = 1.11 (CI 0.40; 3.11). In the quantitative pixel analysis, a lower slope of the fluorescence time-curve was found in patients with a subsequent leak: median 0.08 (0.07;0.10) compared with non-leak patients: median 0.13 (0.10;0.17) (p = 0.04).

CONCLUSION

The surgeon's visual assessment of the ICG-FI demonstrated wide inter-observer variation, there were no differences between patients with and without AL. However, quantitative pixel analysis showed a significant difference between groups.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT04766060.

Clinical application of machine learning and computer vision to indocyanine green quantification for dynamic intraoperative tissue characterisation: how to do it

INTRODUCTION

Indocyanine green (ICG) quantification and assessment by machine learning (ML) could discriminate tissue types through perfusion characterisation, including delineation of malignancy. Here, we detail the important challenges overcome before effective clinical validation of such capability in a prospective patient series of quantitative fluorescence angiograms regarding primary and secondary colorectal neoplasia.

METHODS

ICG perfusion videos from 50 patients (37 with benign (13) and malignant (24) rectal tumours and 13 with colorectal liver metastases) of between 2- and 15-min duration following intravenously administered ICG were formally studied (clinicaltrials.gov: NCT04220242). Video quality with respect to interpretative ML reliability was studied observing practical, technical and technological aspects of fluorescence signal acquisition. Investigated parameters included ICG dosing and administration, distance-intensity fluorescent signal variation, tissue and camera movement (including real-time camera tracking) as well as sampling issues with user-selected digital tissue biopsy. Attenuating strategies for the identified problems were developed, applied and evaluated. ML methods to classify extracted data, including datasets with interrupted time-series lengths with inference simulated data were also evaluated.

RESULTS

Definable, remediable challenges arose across both rectal and liver cohorts. Varying ICG dose by tissue type was identified as an important feature of real-time fluorescence quantification. Multi-region sampling within a lesion mitigated representation issues whilst distance-intensity relationships, as well as movement-instability issues, were demonstrated and ameliorated with post-processing techniques including normalisation and smoothing of extracted time-fluorescence curves. ML methods (automated feature extraction and classification) enabled ML algorithms glean excellent pathological categorisation results (AUC-ROC > 0.9, 37 rectal lesions) with imputation proving a robust method of compensation for interrupted time-series data with duration discrepancies.

CONCLUSION

Purposeful clinical and data-processing protocols enable powerful pathological characterisation with existing clinical systems. Video analysis as shown can inform iterative and definitive clinical validation studies on how to close the translation gap between research applications and real-world, real-time clinical utility.

Evaluating clinical near-infrared surgical camera systems with a view to optimizing operator and computational signal analysis

SIGNIFICANCE

As clinical evidence on the colorectal application of indocyanine green (ICG) perfusion angiography accrues, there is also interest in computerizing decision support. However, user interpretation and software development may be impacted by system factors affecting the displayed near-infrared (NIR) signal.

AIM

We aim to assess the impact of camera positioning on the displayed NIR signal across different open and laparoscopic camera systems.

APPROACH

The effects of distance, movement, and target location (center versus periphery) on the displayed fluorescence signal of different systems were measured under electromagnetic stereotactic guidance from an ICG-albumin model and in vivo during surgery.

RESULTS

Systems displayed distinct fluorescence performances with variance apparent with scope optical lens configuration (0 deg versus 30 deg), movement, target positioning, and distance. Laparoscopic system readings fitted inverse square function distance-intensity curves with one device and demonstrated a direction dependent sigmoid curve. Laparoscopic cameras presented central targets as brighter than peripheral ones, and laparoscopes with angled optical lens configurations had a diminished field of view. One handheld open system also showed a distance-intensity relationship, whereas the other maintained a consistent signal despite distance, but both presented peripheral targets brighter than central ones.

CONCLUSIONS

Optimal clinical use and signal computational development requires detailed appreciation of system behaviors.