SPY technology as an adjunctive measure for lower extremity perfusion

Methods for tissue perfusion assessment after Dellon decompression of tarsal tunnels in diabetic neuropathy: key to effective management-a narrative review

Background and Objective

Diabetic neuropathy significantly elevates the risk of foot ulceration and lower-limb amputation, underscoring the need for precise assessment of tissue perfusion to optimize management. This narrative review explores the intricate relationship between sympathetic nerves and tissue perfusion in diabetic neuropathy, highlighting the important role of autonomic neuropathy in blood flow dynamics and subsequent compromises in tissue perfusion. The consequences extend to the development of diabetic peripheral neuropathy and related foot complications. By analyzing both non-invasive diagnostic methods and surgical interventions, such as tarsal tunnel decompression, the paper seeks to highlight their effectiveness in improving tissue perfusion, preventing ulcers, and reducing the risk of amputations in patients with diabetic peripheral neuropathy.

Methods

We reviewed current literature on both non-invasive diagnostic tools and surgical techniques for assessing and improving tissue perfusion in diabetic neuropathy. Methods discussed include transcutaneous oxygen pressure (TcPO2), Doppler ultrasound, Tissue-Muscle Perfusion Scintigraphy with 99mTc-MIBI, and the SPY Laser Angiographic System.

Key Content and Findings

Emphasizing the critical importance of surgical interventions, such as tarsal tunnel decompression and neurolysis of the posterior tibial nerve, the article underscores their efficacy in enhancing tissue perfusion and preventing ulcers and amputations. Additionally, it addresses the significance of precise blood flow measurement and timely intervention in the management of diabetic neuropathy and foot ulcers. The non-invasive techniques for assessing tissue perfusion and blood flow in diabetic neuropathy such as TcPO2, Doppler ultrasound and Tissue-Muscle Perfusion Scintigraphy with 99mTc-MIBI are explained. Also, this review introduces the SPY Laser Angiographic System, which employs near-infrared fluorescence imaging to assess blood flow and perfusion in tissues. This advanced tool generates real-time microvascular blood flow images and proves instrumental in diagnosing and monitoring diabetic foot ulcers.

Conclusions

In conclusion, surgical interventions, both vascular and peripheral nerve are pivotal for optimizing patient care. Early identification of foot ulcers and peripheral arterial disease is imperative, and an understanding of blood flow dynamics, combined with effective surgical techniques, constitutes key elements in managing diabetic neuropathy, healing and preventing ulcers, and limb salvage.

Near-Infrared Fluorescence Imaging With Indocyanine Green to Predict Clinical Outcome After Revascularization in Lower Extremity Arterial Disease

Contemporary quality control methods are often insufficient in predicting clinical outcomes after revascularization in lower extremity arterial disease (LEAD) patients. This study evaluates the potential of near-infrared fluorescence imaging with indocyanine green to predict the clinical outcome following revascularization. Near-infrared fluorescence imaging was performed before and within 5 days following the revascularization procedure. Clinical improvement was defined as substantial improvement of pain free walking distance, reduction of rest- and/or nocturnal pain, or tendency toward wound healing. Time-intensity curves and 8 perfusion parameters were extracted from the dorsum of the treated foot. The quantified postinterventional perfusion improvement was compared within the clinical outcome groups. Successful near-infrared fluorescence imaging was performed in 72 patients (76 limbs, 52.6% claudication, 47.4% chronic limb-threatening ischemia) including 40 endovascular- and 36 surgical/hybrid revascularizations. Clinical improvement was observed in 61 patients. All perfusion parameters showed a significant postinterventional difference in the clinical improvement group (P-values <.001), while no significant differences were seen in the group without clinical improvement (P-values .168-.929). Four parameters demonstrated significant differences in percentage improvement comparing the outcome groups (P-values within .002-.006). Near-infrared fluorescence imaging has promising additional value besides clinical parameters for predicting the clinical outcome of revascularized LEAD patients.

Challenges in flap monitoring with indocyanine green angiography in experimental models

Introduction

Non-invasive angiography with indocyanine green dye facilitates the assessment of flaps. Although ICG angiography has been successfully utilized in clinical settings for human beings, its application in experimental models exhibits certain limitations. This study aimed to address the encountered issues in angiography with different experimental models and introduce a novel modification to the ICG imaging of the McFarlane flap.

Materials-methods

Rats were randomly divided into three groups: the first group received an epigastric flap (n = 4), the second group received a deep inferior epigastric perforator flap (n = 4), and the third group received a dorsal flap (n = 8). In the first group, sterile silicone background was placed under two flaps. In the second group, no background was used. In the third group, a sterile silicone or aluminum foil was placed under the flaps. Flap perfusions were assessed using fluorescent imaging after flap adaptations, at postoperative 30th minute and 3., 5. and 7. days. Necrosis calculations were performed using all images obtained from the digital camera and the fluorescent imaging. In the third group, the flow velocities were also calculated. All flaps were sent for histopathological examination.

Results

Even with a silicone background, clear perfusion evaluation and determining the threshold value for predicting necrosis rates were challenging. Moreover, a portion of the flaps without background material survived as grafts. Using an aluminum foil background improved image quality by reducing reflection from interior organs.

Conclusion

The use of an aluminum foil background is beneficial in non-invasive angiography for assessing flap perfusions accurately and predicting necrosis in experimental animal models.

High Rates of Discordant Ureteral Perfusion During Open Ureteral Reconstruction With Indocyanine Green: Does Near-Infrared Fluorescence Imaging Change Management or Stricture Outcomes?

OBJECTIVE

To determine the role of near-infrared fluorescence imaging (NIFI) combined with indocyanine green (ICG) to assess ureteral tissue perfusion in a benign genitourinary reconstruction cohort with a high prevalence of prior abdominopelvic radiation and surgery.

MATERIALS AND METHODS

A prospective, single-surgeon series, between June 2018 and April 2022, of patients who underwent open genitourinary reconstructive surgeries in which NIFI/ICG was utilized to intraoperatively assess ureteral tissue perfusion prior to ureteral anastomosis. Primary outcome was ureteroanastomotic stricture (UAS). Secondary outcomes included impact of NIFI/ICG on surgical decision-making and ureter resection length.

RESULTS

Thirty nine patients, median age 66, underwent 40 multimodality reconstructive surgeries during which NIFI/ICG was utilized in the open setting. Radiation-induced etiology was present in 32 of 40 (80%) patients. UAS occurred in 1 of 57 (1.8%) anastomoses with median follow-up of 23.4 months. Use of NIFI/ICG changed intraoperative decision-making in 63% of cases. Change in intraoperative decision-making was more common in patients with prior abdominopelvic radiation (66%) compared to non-radiated patients (13%), P = .007. Discordance between subjective (white-light) and objective (NIFI/ICG) ureteral perfusion (white-light) occurred in 61% of ureters. Mean length of resected ureter was higher following objective assessment with NIFI/ICG (3.6 cm) versus subjective assessment (white light) conditions (1.8 cm), P = .001.

CONCLUSION

Use of NIFI/ICG was associated with low rates of UAS at 2-year follow-up in a cohort with high prevalence of prior radiation. NIFI/ICG was associated with longer lengths of ureter resection and ureteral perfusion assessment discordance compared to subjective surgeon assessment under white-light conditions.

Detection of wound healing disorders after major amputations by measurements of the microcirculation: A prospective single-center study

Introduction

Although major amputations can often be avoided due to evolving methods of endovascular and surgical revascularizations techniques, in patients with chronic limb-threatening ischemia, it is still necessary in some cases. Aim of this study was the detection of wound healing disorders through intraoperative microcirculation measurements in major limb amputations.

Materials and methods

In this single-center clinical study, patients with an indication for major amputation were enrolled prospectively. Cause of amputation, patients' comorbidities including cardiovascular risk profile were assessed. Macrocirculation, as well as microcirculation were assessed. Microcirculation measurements were performed by fluorescence angiography with the administration of indocyanine green. A preoperative measurement was obtained at the amputation level, followed by three additional measurements of the amputation stump postoperatively. Wound healing was monitored and correlated with the microcirculatory findings, based on the perfusion parameters ingress and ingress rate, calculated in the indocyanine green fluorescence video sequences of the amputation stumps.

Results

Forty-five patients were enrolled, including 19 (42%) below-the-knee amputations and 26 (58%) above-the-knee amputations. When considering the need for revision, a change in the microperfusion parameters was observed postoperatively. The mean value for ingress was significantly lower directly postoperatively in stumps requiring revisions (5 ± 0 A.U. versus 40.5 ± 42.5 A.U., p < 0.001). The mean value of ingress rate behaved similarly (0.15 ± 0.07 A.U./s versus 2.8 ± 5.0 A.U./s, p = 0.005). The evaluation of indocyanine green measurements when wound healing disorders occurred also showed nonsignificant differences in the mean values.

Conclusion

Fluorescence angiography after major lower limb amputations appears to be an option of depicting microperfusion. Especially, the early postoperative detection of reduced perfusion can indicate a subsequent need for revision. Therefore, this method could possibly serve as a tool for intraoperative quality control after major limb amputation.

Quantitative perfusion assessment using indocyanine green during surgery - current applications and recommendations for future use

PURPOSE

Incorrect assessment of tissue perfusion carries a significant risk of complications in surgery. The use of near-infrared (NIR) fluorescence imaging with Indocyanine Green (ICG) presents a possible solution. However, only through quantification of the fluorescence signal can an objective and reproducible evaluation of tissue perfusion be obtained. This narrative review aims to provide an overview of the available quantification methods for perfusion assessment using ICG NIR fluorescence imaging and to present an overview of current clinically utilized software implementations.

METHODS

PubMed was searched for clinical studies on the quantification of ICG NIR fluorescence imaging to assess tissue perfusion. Data on the utilized camera systems and performed methods of quantification were collected.

RESULTS

Eleven software programs for quantifying tissue perfusion using ICG NIR fluorescence imaging were identified. Five of the 11 programs have been described in three or more clinical studies, including Flow® 800, ROIs Software, IC Calc, SPY-Q™, and the Quest Research Framework®. In addition, applying normalization to fluorescence intensity analysis was described for two software programs.

CONCLUSION

Several systems or software solutions provide a quantification of ICG fluorescence; however, intraoperative applications are scarce and quantification methods vary abundantly. In the widespread search for reliable quantification of perfusion with ICG NIR fluorescence imaging, standardization of quantification methods and data acquisition is essential.

Evaluation of the Angiosome Concept Using Near-Infrared Fluorescence Imaging with Indocyanine Green

BACKGROUND

The angiosome concept is defined as the anatomical territory of a source artery within all tissue layers. When applying this theory in vascular surgery, direct revascularization (DR) is preferred to achieve increased blood flow toward the targeted angiosome of the foot in patients with lower extremity arterial disease (LEAD). This study evaluates the applicability of the angiosome concept using quantified near-infrared (NIR) fluorescence imaging with indocyanine green (ICG).

METHODS

This study included patients undergoing an endovascular- or surgical revascularization of the leg between January 2019 and December 2021. Preinterventional and postinterventional ICG NIR fluorescence imaging was performed. Three angiosomes on the dorsum of the foot were determined: the posterior tibial artery (hallux), the anterior tibial artery (dorsum of the foot) and the combined angiosome (second to fifth digit). The angiosomes were classified from the electronic patient records and the degree of collateralization was classified based on preprocedural computed tomography angiography and/or X-ray angiography. Fluorescence intensity was quantified in all angiosomes. A subgroup analysis based on endovascular or surgical revascularized angiosomes, and within critical limb threatening ischemia (CLTI) patients was performed.

RESULTS

ICG NIR fluorescence measurements were obtained in 52 patients (54 limbs) including a total of 157 angiosomes (121 DR and 36 indirect revascularizations [IR]). A significant improvement of all perfusion parameters in both the directly and indirectly revascularized angiosomes was found (P-values between <0.001-0.007). Within the indirectly revascularized angiosomes, 90.6% of the scored collaterals were classified as significant. When comparing the percentual change in perfusion parameters between the directly and indirectly revascularized angiosomes, no significant difference was seen in all perfusion parameters (P-values between 0.253 and 0.881). Similar results were shown in the CLTI patients subgroup analysis, displaying a significant improvement of perfusion parameters in both the direct and indirect angiosome groups (P-values between <0.001 and 0.007), and no significant difference when comparing the percentual parameter improvement between both angiosome groups (P-values between 0.134 and 0.359). Furthermore, no significant differences were observed when comparing percentual changes of perfusion parameters in directly and indirectly revascularized angiosomes for both endovascular and surgical interventions (P-values between 0.053 and 0.899).

CONCLUSIONS

This study proves that both DR and IR of an angiosome leads to an improvement of perfusion. This suggests that interventional strategies should not only focus on creating in-line flow to the supplying angiosome. One can argue that the angiosome concept is not applicable in patients with LEAD.

A Systematic Review and Critical Appraisal of Peri-Procedural Tissue Perfusion Techniques and their Clinical Value in Patients with Peripheral Arterial Disease

OBJECTIVE

Many techniques have been introduced to enable quantification of tissue perfusion in patients with peripheral arterial disease (PAD). Currently, none of these techniques is widely used to analyse real time tissue perfusion changes during endovascular or surgical revascularisation procedures. The aim of this systematic review was to provide an up to date overview of the peri-procedural applicability of currently available techniques, diagnostic accuracy of assessing tissue perfusion and the relationship with clinical outcomes.

DATA SOURCES

MEDLINE, Embase, CINAHL, and the Cochrane Central Register of Controlled Trials.

REVIEW METHODS

This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic review and Meta-Analysis (PRISMA) guidelines. Four electronic databases were searched up to 31 12 2020 for eligible articles: MEDLINE, Embase, CINAHL and the Cochrane Central Register of Controlled Trials. Eligible articles describing a perfusion measurement technique, used in a peri-procedural setting before and within 24 hours after the revascularisation procedure, with the aim of determining the effect of intervention in patients with PAD, were assessed for inclusion. The QUADAS-2 tool was used to assess the risk of bias and applicability of the studies.

RESULTS

An overview of 10 techniques found in 26 eligible articles focused on study protocols, research goals, and clinical outcomes is provided. Non-invasive techniques included laser speckle contrast imaging, micro-lightguide spectrophotometry, magnetic resonance imaging perfusion, near infrared spectroscopy, skin perfusion pressure, and plantar thermography. Invasive techniques included two dimensional perfusion angiography, contrast enhanced ultrasound, computed tomography perfusion imaging, and indocyanine green angiography. The results of the 26 eligible studies, which were mostly of poor quality according to QUADAS-2, were without exception, not sufficient to substantiate implementation in daily clinical practice.

CONCLUSION

This systematic review provides an overview of 10 tissue perfusion assessment techniques for patients with PAD. It seems too early to appoint one of them as a reference standard. The scope of future research in this domain should therefore focus on clinical accuracy, reliability, and validation of the techniques.

Near-infrared fluorescence imaging with indocyanine green for quantification of changes in tissue perfusion following revascularization

OBJECTIVES

Current diagnostic modalities for patients with peripheral artery disease (PAD) mainly focus on the macrovascular level. For assessment of tissue perfusion, near-infrared (NIR) fluorescence imaging using indocyanine green (ICG) seems promising. In this prospective cohort study, ICG NIR fluorescence imaging was performed pre- and post-revascularization to assess changes in foot perfusion.

METHODS

ICG NIR fluorescence imaging was performed in 36 patients with PAD pre- and post-intervention. After intravenous bolus injection of 0.1 mg/kg ICG, the camera registered the NIR fluorescence intensity over time on the dorsum of the feet for 15 min using the Quest Spectrum Platform®. Time-intensity curves were plotted for three regions of interest (ROI): (1) the dorsum of the foot, (2) the forefoot, and (3) the hallux. Time-intensity curves were normalized for maximum fluorescence intensity. Extracted parameters were the maximum slope, area under the curve (AUC) for the ingress, and the AUC for the egress. The non-treated contralateral leg was used as a control group.

RESULTS

Successful revascularization was performed in 32 patients. There was a significant increase for the maximum slope and AUC egress in all three ROIs. The most significant difference was seen for the maximum slope in ROI 3 (3.7%/s to 6.6%/s, p < 0.001). In the control group, no significant differences were seen for the maximum slope and AUC egress in all ROIs.

CONCLUSIONS

This study shows the potential of ICG NIR fluorescence imaging in assessing the effect of revascularization procedures on foot perfusion. Future studies should focus on the use of this technique in predicting favorable outcome of revascularization procedures.

Perfusion Parameters in Near-Infrared Fluorescence Imaging with Indocyanine Green: A Systematic Review of the Literature

(1) Background: Near-infrared fluorescence imaging is a technique capable of assessing tissue perfusion and has been adopted in various fields including plastic surgery, vascular surgery, coronary arterial disease, and gastrointestinal surgery. While the usefulness of this technique has been broadly explored, there is a large variety in the calculation of perfusion parameters. In this systematic review, we aim to provide a detailed overview of current perfusion parameters, and determine the perfusion parameters with the most potential for application in near-infrared fluorescence imaging. (2) Methods: A comprehensive search of the literature was performed in Pubmed, Embase, Medline, and Cochrane Review. We included all clinical studies referencing near-infrared perfusion parameters. (3) Results: A total of 1511 articles were found, of which, 113 were suitable for review, with a final selection of 59 articles. Near-infrared fluorescence imaging parameters are heterogeneous in their correlation to perfusion. Time-related parameters appear superior to absolute intensity parameters in a clinical setting. (4) Conclusions: This literature review demonstrates the variety of parameters selected for the quantification of perfusion in near-infrared fluorescence imaging.

Fluorescent angiography used as a tool to guide angiosome-directed endovascular therapy for diabetic foot ulcers

Angiosome-directed endovascular therapy for the treatment of chronic limb-threatening ischemia (CLTI) remains controversial owing to the overlap of wound angiosomes. Angiographic grading of success has limitations and translesional pressure assessments are seldom performed in the infrapopliteal vessels. Objective criteria to determine revascularization success in tibiopedal vessels have not been well described. Quantifying perfusion to a wound bed after establishing direct or indirect (via collateral) flow after revascularization is an important component for treating CLTI patients yet is seldom performed. We report the use of fluorescent angiography to quantitatively examine perfusion of a diabetic foot ulcer before and after angiosome-directed endovascular therapy.

2D perfusion DSA with an open-source, semi-automated, color-coded software for the quantification of foot perfusion following infrapopliteal angioplasty: a feasibility study

BACKGROUND

Foot perfusion has been recently implemented as a new tool for optimizing outcomes of peripheral endovascular procedures. A custom-made, two-dimensional perfusion digital subtraction angiography (PDSA) algorithm has been implemented to quantify outcomes of endovascular treatment of critical limb ischemia (CLI), assist intra-procedural decision-making, and enhance clinical outcomes.

METHODS

The study was approved by the Hospital's Ethics Committee. This prospective, single-center study included seven consecutive patients scheduled to undergo infrapopliteal endovascular treatment of CLI. Perfusion blood volume (PBV), mean transit time (MTT), and perfusion blood flow (PBF) maps were extracted by analyzing time-intensity curves and signal intensity on the perfused vessel mask. Mean values calculated from user-specified regions of interest (ROIs) on perfusion maps were employed to evaluate pre- and post-endovascular treatment condition. Measurements were performed immediately after final PDSA.

RESULTS

In total, five patients (aged 54 ± 16 years, mean ± standard deviation) were analyzed, as two patients were excluded due to significant motion artifacts. Post-procedural MTT presented a mean decrease of 19.1% for all patients and increased only in 1 of 5 patients, demonstrating in 4/5 patients an increase in tissue perfusion after revascularization. Overall mean PBF and PBV values were also analogously increased following revascularization (446% and 69.5% mean, respectively) and in the majority of selected ROIs (13/15 and 12/15 ROIs, respectively).

CONCLUSIONS

Quantification of infrapopliteal angioplasty outcomes using this newly proposed, custom-made, intra-procedural PDSA algorithm was performed using PBV, MTT, and PBF maps. Further studies are required to determine its role in peripheral endovascular procedures ( ClinicalTrials.gov Identifier: NCT04356092).

Intraoperative fluorescence perfusion assessment should be corrected by a measured subject-specific arterial input function

SIGNIFICANCE

The effects of varying the indocyanine green injection dose, injection rate, physiologic dispersion of dye, and intravenous tubing volume propagate into the shape and magnitude of the arterial input function (AIF) during intraoperative fluorescence perfusion assessment, thereby altering the observed kinetics of the fluorescence images in vivo.

AIM

Numerical simulations are used to demonstrate the effect of AIF on metrics derived from tissue concentration curves such as peak fluorescence, time-to-peak (TTP), and egress slope.

APPROACH

Forward models of tissue concentration were produced by convolving simulated AIFs with the adiabatic approximation to the tissue homogeneity model using input parameters representing six different tissue examples (normal brain, glioma, normal skin, ischemic skin, normal bone, and osteonecrosis).

RESULTS

The results show that AIF perturbations result in variations in estimates of total intensity of up to 80% and TTP error of up to 200%, with the errors more dominant in brain, less in skin, and less in bone. Interestingly, error in ingress slope was as high as 60% across all tissue types. These are key observable parameters used in fluorescence imaging either implicitly by viewing the image or explicitly through intensity fitting algorithms. Correcting by deconvolving the image with a measured subject-specific AIF provides an intuitive means of visualizing the data while also removing the source of variance and allowing intra- and intersubject comparisons.

CONCLUSIONS

These results suggest that intraoperative fluorescence perfusion assessment should be corrected by patient-specific AIFs measured by pulse dye densitometry.

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.

Assessment of foot perfusion: Overview of modalities, review of evidence, and identification of evidence gaps

Patients with critical limb ischemia have nonhealing wounds and/or ischemic rest pain and are at high risk for amputation and mortality. Accurate evaluation of foot perfusion should help avoid unnecessary amputation, guide revascularization strategies, and offer efficient surveillance for patency. Our aim is to review current modalities of assessing foot perfusion in the context of the practical clinical management of patients with critical limb ischemia.

Fluorescence angiography compared to toe blood pressure in the evaluation of severe limb ischemia

Background: Severity of limb ischemia in peripheral arterial disease (PAD) patients is usually evaluated by clinical assessment and toe blood pressure (TBP) or transcutaneous oxygen pressures (TcPO 2). Indocyanin green angiography (IGA) is a promising tool generating a foot cartography of skin microvascular perfusion. However, there is no consensus about the fluorescence parameters that should be used to evaluate ischemia. The purpose of this cross-sectional evaluation and 3-month clinical follow-up was to determine the best fluorescence parameter for the evaluation of severe PAD, using TBP as reference. Patients and methods: IGA was realized in patients with clinical suspicion of CLI in addition to TBP and TcPO 2. Parameters from the time intensity fluorescence curve measured on the foot were compared with TBP (primary reference), and with TcPO2. Clinical outcomes (amputation, revascularization, death) were recorded at 3 months follow-up. Results: Thirty-four patients were included and IGA could be analysed in 29 of them. When all limbs were studied, no significant correlation was found between any of the measured fluorescence parameters (saturation time, ingress slope, amplitude, delay) and TBP pressure neither TCPO2. In the limbs with CLI, a significant correlation between the TBP and amplitude on the forefoot was found. According to the outcome, none of the fluorescence parameters showed a significant prognostic value in contrast to the significant results for TBP and TcPO2. Conclusions: In this study, quantitative analysis of IGA parameters did not show any prognostic value, nor was there any significant statistical association with well-established prognostic parameters such as TBP and TcPO 2 in patients with suspected CLI. A correlation was found between amplitude and TBP in patients with CLI. Topographical information such as perfusion heterogeneity was not evaluated and remains a valuable target to be investigated.

A systematic review of the use of near-infrared fluorescence imaging in patients with peripheral artery disease

OBJECTIVE

In the diagnosis of peripheral artery disease (PAD), the ankle-brachial index plays an important role. However, results of the ankle-brachial index are unreliable in patients with severe media sclerosis. Near-infrared (NIR) fluorescence imaging using indocyanine green (ICG) can provide information about tissue perfusion and has already been studied in oncologic, reconstructive, and cardiac surgery. For patients with PAD, this technique might give insight into skin perfusion and thereby guide treatment. We performed a systematic review of the literature on the use of NIR fluorescence imaging in patients with PAD.

METHODS

PubMed, MEDLINE, Embase, and Cochrane were searched for articles and abstracts on the application of NIR fluorescence imaging using ICG as fluorescent dye in patients with PAD. Our search strategy combined the terms "fluorescence," "ICG," or synonyms and "peripheral artery disease" or synonyms. The extracted data included fluorescence parameters and test characteristics for diagnosis of PAD.

RESULTS

Twenty-three articles were found eligible for this review using 18 different parameters for evaluation of the fluorescence signal intensity. NIR fluorescence imaging was used for four main indications: diagnosis, quality control in revascularization, guidance in amputation surgery, and visualization of vascular structures. For the diagnosis of PAD, NIR fluorescence imaging yields a sensitivity ranging from 67% to 100% and a specificity varying between 72% and 100%. Significant increases in multiple fluorescence parameters were found in comparing patients before and after revascularization.

CONCLUSIONS

NIR fluorescence imaging can be used for several indications in patients with PAD. NIR fluorescence imaging seems promising in diagnosis of PAD and guidance of surgeons in treatment, especially in patients in whom current diagnostic methods are not applicable. Further standardization is needed to reliably use this modality in patients with PAD.

Unique Uses of SPY: High-risk Facelift

Skin flap necrosis occurs in 1-3% of facelift procedures. The SPY Elite Fluorescence Imaging System has been widely used in evaluating mastectomy skin flaps for breast reconstruction but has not been described in assessing skin flaps during facelifts. This case report describes the intraoperative use of SPY to assess flap perfusion during a high-risk facelift and static sling for the correction of facial paralysis. The use of intraoperative SPY during this high-risk facelift allowed for the timely assessment of perfusion, successful intervention of nitroglycerin paste to improve blood flow, and prevention of any additional surgical interventions. SPY may have a more widespread role in facelift patients with a higher risk of skin flap necrosis.

Real-Time Quantitative Measurements of Foot Perfusion in Patients With Critical Limb Ischemia

INTRODUCTION

Current methods of evaluating adequacy of endovascular procedures are imperfect and do not always predict which patients will do well. The purpose of this study was to evaluate the role of real-time quantitative measurements of perfusion among patients with critical limb ischemia.

MATERIALS AND METHODS

Thirty-four patients with critical limb ischemia undergoing endovascular treatment were recruited. Perfusion Images of the foot were obtained pre and post successful angioplasty using an SPY Elite System (Novadaq Technologies, Ontario, Canada). Patients were followed for 6 months. Subsequently a logistic regression was performed to determine whether intraprocedural perfusion parameters predicted the odds of wound healing.

RESULTS

Twenty-nine patients had successful angioplasty. Median age was 69.5% ± 8.3; 75% were men and 64% were diabetic. Rutherford stages were (4%-39%, 5%-57%, 6%-4%), and the average target limb ankle-brachial index (ABI) was 0.58 (SD 2.24). There was no significant correlation between the ABI and perfusion parameters. Inflow perfusion rate correlated significantly with Rutherford stage (Spearman rho 0.398, P = .036). After successful angioplasty 39% had a decrease in inflow rate and 57% had a decreased total inflow. In all, 25 patients completed 6 months of follow-up. Resolution of rest pain and/or healing of the ischemic wound occurred in 10 (40%) patients at 1 month, 4 (16%) at 3 months, and 2 (8%) at 6 months. One patient underwent a major amputation at 2 months. Eight (32%) patients never healed or had persistent rest pain. None of the real-time perfusion variables were significant predictors of wound healing.

CONCLUSION

Many patients experience a paradoxical decrease in perfusion following successful angioplasty suggesting perfusion may not correlate with angiographic outcome, possibly due to microemboli, microvascular disease, or vasospasm. Real-time perfusion imaging following intra-arterial infusion of indocyanine green does not predict the odds of wound healing.

Fallopian tube perfusion in ex-vivo and in-vivo laparoscopic hysterectomy specimens: potential application for uterine transplantation

STUDY QUESTION

Is there perfusion to the fallopian tubes in ex-vivo and in-vivo uteri at the time of total laparoscopic hysterectomy (TLH), as observed using laser angiography with indocyanine green (ICG)?

SUMMARY ANSWER

The fallopian tubes may have perfusion from the utero-ovarian vasculature alone.

WHAT IS KNOWN ALREADY

The fallopian tubes are perfused by the uterine and utero-ovarian vessels. Perfusion can be measured using laser angiography with ICG.

STUDY DESIGN, SIZE, DURATION

This prospective pilot cohort study included 15 women, ages 32-59 years old, who underwent TLH with bilateral salpingectomy for benign indications.

PARTICIPANTS/MATERIALS, SETTING, METHODS

In five participants, TLH was performed and the utero-ovarian artery was cannulated ex vivo and injected with ICG. The other 10 participants underwent the in-vivo protocol. The mesosalpinx and uterine vessels were transected in the partial protocol. Colpotomy was also performed in the complete protocol. All fallopian tubes were imaged using laser angiography with ICG. The relative fluorescence and the fluorescence intensity ratio (length of fluorescent fallopian tube/total length of fallopian tube) of the fallopian tubes were measured in the ex-vivo and in-vivo protocols, respectively.

MAIN RESULTS AND THE ROLE OF CHANCE

Ex vivo, the fimbria of the ipsilateral fallopian tube had 47% median relative fluorescence as compared to the contralateral fallopian tube, which had 2.4% median relative fluorescence. In vivo, the post-ICG fluorescence intensity ratios were 0.61 ± 0.40 for the partial protocol, and 0.78 ± 0.30 for the complete protocol, with mean differences of 0.37 (95% CI: 0.23-0.50, P < .0001) and 0.22 (95% CI: 0.12-0.31, P < 0.0001), respectively, between the pre-procedure and the post-ICG fluorescence intensity ratios. Greater than 0.75 fluorescence intensity ratios (i.e. >75% tubal length fluorescence) was seen in 60% of fallopian tubes.

LIMITATIONS, REASONS FOR CAUTION

This is a pilot study with a small sample size and pathologic uteri, which would not be appropriate for uterine transplantation. No conclusions can be made regarding the functionality of the fallopian tubes.

WIDER IMPLICATIONS OF THE FINDINGS

The fallopian tubes may have perfusion with the utero-ovarian vasculature alone, potentially allowing for future animal studies regarding tubal viability in recipients of uterine-tubal transplants. If successful, human uterine-tubal transplantation may allow for spontaneous conception rather than IVF.

STUDY FUNDING/COMPETING INTEREST(S)

No external funding was used. S.F., P.F.P., K.A.S. and R.F. have no conflicts of interest to report. M.L.S. is an educational consultant for Medtronic (Dublin, Republic of Ireland) and Applied Medical (Rancho Santa Margarita, CA, USA), as well as a stockholder for SynDaver Labs (Tampa, FL, USA). S.E.Z. is an educational consultant for Applied Medical (Rancho Santa Margarita, CA, USA) and is on the advisory board for AbbVie Inc. (Chicago, IL, USA).

TRIAL REGISTRATION NUMBER

Not applicable.

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

Intraoperative valuation of organ and tissue microperfusion is always a current topic in different surgical situations. Although indocyanine green fluorescent imaging (ICG-FI) has turned to be a more and more common technique to evaluate organ perfusion, only few studies tried to quantitatively validate the technique for microperfusion assessment. The aim of the following manuscript is to present the results of our interdisciplinary research confirming additional quantitative assessment tools in different surgical conditions. Thus, we are implementing the background-subtracted peak fluorescent intensity (BSFI), the slope of fluorescence intensity (SFI), and the time to slope (TTS) using ICG-FI in several regions of interest (ROI).

The Ability of Fluorescence Angiography to Detect Local Ischemia in Patients With Heel Ulceration

Heel ulcerations are a significant burden of care in both hospital and long-term care settings. The presence of peripheral arterial disease as a contributing factor to delayed healing is often not recognized, resulting in prolonged healing and high patient morbidity and mortality. Formal vascular evaluation and intervention is often not performed as these patients can have palpable pedal pulses while having localized ischemia of the heel. As routine noninvasive vascular studies can be affected by medial calcinosis and collateralization and do not specifically assess tissue perfusion to the heel, a false sense of security of adequate perfusion for healing can result. Indocyanine green fluorescence angiography (ICGFA) allows for real-time visualization and objective assessment of site specific tissue perfusion not limited by the factors that can make routine noninvasive vascular studies unreliable or unobtainable. A retrospective medical record review of a subset of patients with chronic heel ulceration from a prospective institutional review board-approved study in which serial ICGFA was performed during their treatment course was performed. ICGFA was able to identify local heel ischemia and expedite vascular intervention. ICGFA should be considered as an additional vascular study in patients presenting with chronic, nonhealing heel ulcerations.

LEVELS OF EVIDENCE

Level IV: Diagnostic, Case series.

Is non-invasive indocyanine-green angiography a useful adjunct for the debridement of infected sternal wounds?

Laser-assisted indocyanine-green imaging (ICG) has a wide range of surgical applications, and has been used in reconstructive surgery to aid in assessing the viability of free tissue transfers and to help predict poor tissue perfusion. However, its indications for use is limited to assessing free flap tissue perfusion, coronary artery perfusion during coronary artery bypass (CABG), and tissue perfusion in diabetic foot ulcers, to name a few. This system has been proven to be a safe, reliable adjunctive modality to assess microvascular compromise or poor perfusion peri-operatively, which could minimize skin necrosis and other post-operative complications (Further et al., 2013).¹ The ability to objectively assess tissue perfusion has led to improved post-operative outcomes in breast, abdominal wall, colorectal, and cardiac surgery. To date, no studies have reviewed the use of ICG in delineating devitalized bone during sternal wound debridement after cardiac surgery. At our institution, we have encountered a cohort of patients with post-cardiac surgery sternal wound infections who have required debridement of infected and devitalized bone. We propose that SPY technology aids in delineating this devitalized bone, and may aid in the timing muscle flap coverage. In this paper, we will demonstrate two cases of patients who had post-operative sternal wound infections after undergoing cardiac surgery for which ICG was used to demarcate debridement zones and subsequent flap coverage. In these cases, ICG allowed for efficient and reliable intraoperative evaluation of bony perfusion and has aided in early adequate debridement and flap coverage.

Noninvasive measurements of tissue perfusion in critical limb ischemia

Critical limb ischemia (CLI) remains a challenge for an interdisciplinary therapeutic team due to chronic nonhealing wounds. Against this background, there is a necessity of quality control after revascularization. Beside the isolated evaluation of the macrocirculation by Ankle-Brachial or Toe-Brachial Index measurements, the microcirculation as an additional important factor of wound healing often remains underestimated. The following article gives an overview about the current investigation methods for noninvasive perfusion control of the CLI patient. Therefore, transcutaneous oxygen pressure (tcpO₂), the “oxygen-to-see” method which is a combination of white light tissue spectrometry and laser-Doppler flowmetry, fluorescence angiography with indocyanine green, and multispectral optoacoustic tomography will be described.

Pilot Assessment of the Angiosome Concept by Intra-operative Fluorescence Angiography After Tibial Bypass Surgery

OBJECTIVES

The "angiosome" concept as a model for decision making in revascularisation of patients with critical limb ischaemia (CLI) has been subject to lively discussion in recent years. The aim of this prospective pilot study was to use intra-operative fluorescence angiography to provide further data on the angiosome concept on the level of microcirculation after tibial bypass surgery.

DESIGN, MATERIALS, AND METHODS

This was a prospective analysis of 40 patients presenting with CLI Rutherford stage IV to VI before and after tibial bypass surgery. The macrocirculation was measured by the ankle brachial index. Skin microcirculation was assessed by intra-operative fluorescence angiography. The alteration of microcirculation was compared in direct and indirect revascularised angiosomes. Clinical follow-up investigations were performed and the wound healing rate was compared between the different revascularisation methods.

RESULTS

Cumulated microcirculation parameters showed a significant improvement after surgery (ingress, ingress rate p<.001). Likewise, general microcirculatory improvement was observed in each foot angiosome after revascularisation, regardless of the tibial artery revascularised. Furthermore, a comparison of the direct (DR) and the indirect revascularised (IR) angiosomes did not show a significant difference concerning the improvement of microcirculation (difference DR-IR, ingress: 1.69, 95% CI 71.73-75.11; ingress rate: 0.08, 95% CI -12.91 to 13.07). The wound healing rate was similar in both groups, although the time to wound healing was faster by on average 2.5 months in the DR group (p=.083).

CONCLUSION

Microcirculatory improvement was seen over the whole foot after tibial bypass. Therefore, fluorescence angiography is a promising tool to evaluate the angiosome concept in future larger studies. Clinicaltrials.gov: NCT03012750.