Utilization of indocynanine green fluorescent imaging (ICG-FI) for the assessment of microperfusion in vascular medicine

The Wonder Dye: Uses and Implications of Indigocyanine Green in Various Surgeries

Indigocyanine green (ICG) is a fluorophore dye that has been extensively used in recent modern times for bioimaging in numerous surgeries to aid in easier identification of occult and often tricky-to-find anatomical structures. Surgery becomes complex and challenging due to multiple anatomical anomalies, pathological fibrosis, obesity, or previous surgeries. To overcome these obstacles in surgery, the surgeon yearns to know the structures present beyond their white light vision so that while dissecting the organ, they can avoid injuring the critical systems in the vicinity of dissection. Near-infrared (NIR) imaging aids in visualising the tissues at depth/in the area of dissection, thereby preventing any possible surgical catastrophes due to them inadvertently damaging surrounding vital structures. Various advantages in surgeries like gastric sleeve surgery, lymph node and tumour detection, localisation of ureters and biliary tracts, and intraoperative tissue perfusion of flaps have been described in this study. This review article aims to compile a short list of utilities of ICG with NIR imaging in various surgical interventions. The merits and demerits of this imaging technique have been noted. The study points out the uses of ICG fluorescence imaging under different surgical fronts. This review article concludes by comparing the results of studies performed by various authors. Results have been compared to conventional surgical modalities.

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.

Feasibility and comparison of laparoscopic laser speckle contrast imaging to near-infrared display of indocyanine green in intraoperative tissue blood flow/tissue perfusion in preclinical porcine models

OBJECTIVE

To determine if laser speckle contrast imaging (LSCI) mitigates variations and subjectivity in the use and interpretation of indocyanine green (ICG) fluorescence in the current visualization paradigm of real-time intraoperative tissue blood flow/perfusion in clinically relevant scenarios.

METHODS

De novo laparoscopic imaging form-factor detecting real-time blood flow using LSCI and blood volume by near-infrared fluorescence (NIRF) of ICG was compared to ICG NIRF alone, for dye-less real-time visualization of tissue blood flow/perfusion. Experienced surgeons examined LSCI and ICG in segmentally devascularized intestine, partial gastrectomy, and the renal hilum across six porcine models. Precision and accuracy of identifying demarcating lines of ischemia/perfusion in tissues were determined in blinded subjects with varying levels of surgical experience.

RESULTS

Unlike ICG, LSCI perfusion detection was real time (latency < 150 ms: p < 0.01), repeatable and on-demand without fluorophore injection. Operating surgeons (n = 6) precisely and accurately identified concordant demarcating lines in white light, LSCI, and ICG modes immediately. Blinded subjects (n = 21) demonstrated similar spatial-temporal precision and accuracy with all three modes ≤ 2 min after ICG injection, and discordance in ICG mode at ≥ 5 min in devascularized small intestine (p < 0.0001) and in partial gastrectomy (p < 0.0001).

CONCLUSIONS

Combining LSCI for near real-time blood flow detection with ICG fluorescence for blood volume detection significantly improves precision and accuracy of perfusion detection in tissue locations over time, in real time, and repeatably on-demand than ICG alone.

Normalization of Time-Intensity Curves for Quantification of Foot Perfusion Using Near-Infrared Fluorescence Imaging With Indocyanine Green

PURPOSE

Near-infrared (NIR) fluorescence imaging using indocyanine green (ICG) is gaining popularity for the quantification of tissue perfusion, including foot perfusion in patients with lower extremity arterial disease (LEAD). However, the absolute fluorescence intensity is influenced by patient-and system-related factors limiting reliable and valid quantification. To enhance the quality of quantitative perfusion assessment using ICG NIR fluorescence imaging, normalization of the measured time-intensity curves seems useful.

MATERIALS AND METHODS

In this cohort study, the effect of normalization on 2 aspects of ICG NIR fluorescence imaging in assessment of foot perfusion was measured: the repeatability and the region selection. Following intravenous administration of ICG, the NIR fluorescence intensity in both feet was recorded for 10 mins using the Quest Spectrum platform^®. The effect of normalization on repeatability was measured in the nontreated foot in patients undergoing unilateral revascularization preprocedural and postprocedural (repeatability group). The effect of normalization on region selection was performed in patients without LEAD (region selection group). Absolute and normalized time-intensity curves were compared.

RESULTS

Successful ICG NIR fluorescence imaging was performed in 54 patients (repeatability group, n = 38; region selection group, n = 16). For the repeatability group, normalization of the time-intensity curves displayed a comparable inflow pattern for repeated measurements. For the region selection group, the maximum fluorescence intensity (Imax) demonstrated significant differences between the 3 measured regions of the foot (P = .002). Following normalization, the time-intensity curves in both feet were comparable for all 3 regions.

CONCLUSION

This study shows the effect of normalization of time-intensity curves on both the repeatability and region selection in ICG NIR fluorescence imaging. The significant difference between absolute parameters in various regions of the foot demonstrates the limitation of absolute intensity in interpreting tissue perfusion. Therefore, normalization and standardization of camera settings are essential steps toward reliable and valid quantification of tissue perfusion using ICG NIR fluorescence imaging.

Perfusion Patterns in Patients with Chronic Limb-Threatening Ischemia versus Control Patients Using Near-Infrared Fluorescence Imaging with Indocyanine Green

In assessing the severity of lower extremity arterial disease (LEAD), physicians rely on clinical judgements supported by conventional measurements of macrovascular blood flow. However, current diagnostic techniques provide no information about regional tissue perfusion and are of limited value in patients with chronic limb-threatening ischemia (CLTI). Near-infrared (NIR) fluorescence imaging using indocyanine green (ICG) has been used extensively in perfusion studies and is a possible modality for tissue perfusion measurement in patients with CLTI. In this prospective cohort study, ICG NIR fluorescence imaging was performed in patients with CLTI and control patients using the Quest Spectrum Platform^® (Middenmeer, The Netherlands). The time–intensity curves were analyzed using the Quest Research Framework. Fourteen parameters were extracted. Successful ICG NIR fluorescence imaging was performed in 19 patients with CLTI and in 16 control patients. The time to maximum intensity (seconds) was lower for CLTI patients (90.5 vs. 143.3, p = 0.002). For the inflow parameters, the maximum slope, the normalized maximum slope and the ingress rate were all significantly higher in the CLTI group. The inflow parameters observed in patients with CLTI were superior to the control group. Possible explanations for the increased inflow include damage to the regulatory mechanisms of the microcirculation, arterial stiffness, and transcapillary leakage.

The use of Indocyanine green fluorescent in patients with abdominal trauma for better intraoperative decision-making and less bowel anastomosis leak: case series

Despite technological advances in the management of blunt abdominal trauma, the rate of bowel anastomotic leakage (AL) remains high. The etiology of AL is multifactorial, but insufficient blood perfusion is considered to play a substantial role in the pathogenesis. In recent years, angiography with Indocyanine green (ICG), a fluorescent dye, has been introduced in the clinical practice to assess organ perfusion in several conditions. Given the scarcity of publications describing the use of ICG in trauma patients as a potentially useful strategy that may facilitate intraoperative decisions and limit the extent of bowel resection, we presented the utility of intraoperative ICG fluorescent in abdominal trauma patients in a level 1 trauma center. The use of ICG fluoroscopy in patients with abdominal trauma is feasible and useful; however, large prospective studies in trauma patients are warranted.

New Innovations and Devices in the Management of Chronic Limb-Threatening Ischemia

As the number of patients afflicted by chronic limb-threatening ischemia (CLTI) continues to grow, new solutions are necessary to provide effective, durable treatment options that will lead to improved outcomes. The diagnosis of CLTI remains mostly clinical, and endovascular revascularization remains mostly balloon-based. Multiple innovative techniques and technologies are in development or in early usage that may provide new solutions. This review categorizes areas of advancement, highlights recent developments in the management of CLTI and looks forward to novel devices that are currently under investigation.

Application of Fluorescent Dyes in Visceral Surgery: State of the Art and Future Perspectives

Background

Through the improvement and implementation of advanced intraoperative imaging, the indications for intraoperative fluorescence have spread to various fields of visceral surgery. Indocyanine green (ICG)-based fluorescence angiography and the imaging systems using this certain dye are currently the cornerstone of intraoperative, fluorescence-based medical imaging.

Summary

The article focuses on principles and approaches of intraoperative fluorescence in general surgery. The current clinical practice of intraoperative fluorescence and its evidence are described. Emerging new fields of application are put in a perspective. Furthermore, the technique and possible pit-falls in the performance of intraoperative ICG fluorescence angiography are described in this review article.

Key Messages

Overall growing evidence suggests that intraoperative fluorescence imaging delivers valuable additional information to the surgeon, which might help to perform surgery more exactly and reduce perioperative complications. Perfusion assessment can be a helpful tool when performing critical anastomoses. There is evidence from prospective and randomized trials for the benefit of intraoperative ICG fluorescence angiography during esophageal reconstruction, colorectal surgery, and surgery for mesenteric ischemia. Most studies suggest the administration of 2.5-10 mg of ICG. Standardized settings and documentation are essential. The benefit of ICG fluorescence imaging for gastrointestinal sentinel node detection and detection of liver tumors and colorectal metastases of the liver cannot clearly be estimated duo to the small number of prospective studies. Critical points in the use of intraoperative fluorescence imaging remain the low standardization and reproducibility of the results and the associated difficulty in comparing the results of the existing trials. Furthermore, little is known about the influence of hemodynamic parameters on the quantitative assessment of ICG fluorescence during surgery.