(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.

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.

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.

Foot ulceration is a significant and growing health problem worldwide, particularly due to rises in diabetes mellitus (DM) and peripheral artery disease. The prediction of ulcer healing remains a major challenge. In patients with foot ulcers, medial arterial calcification (MAC) can be present as a result of concomitant DM or chronic kidney disease and is a prognostic factor for unfavorable outcome. This systematic review aimed to evaluate the prognostic reliability of bedside tests to predict ulcer healing and wound healing after minor amputation in patients prone to MAC, following PRISMA guidelines. Primary endpoints were the positive and negative likelihood ratios for ulcer healing. Methodological quality and risk of bias were assessed using the QUIPS-tool. A total of 35 studies were included, predominantly investigating transcutaneous oxygen pressure (TcPO ₂ ), followed by ankle–brachial index and toe pressure. None of these bedside tests effectively provided an acceptable trade-off between predicting healing and nonhealing. A TcPO ₂ below 30 mmHg was most closely associated with nonhealing of an ulcer. The same applied to wound healing after minor amputation, in which none of the bedside tests was able to sufficiently predict healing or nonhealing. To conclude, currently used bedside tests lack acceptable prognostic performance for ulcer healing and healing after minor amputation in patients prone to MAC. Future prospective studies should establish a clear definition of ulcer healing, utilize a standardized wound classification system, and minimize patient heterogeneity. A combined assessment of microvascular and macrovascular perfusion status could improve the prediction of wound healing.

Near-infrared fluorescence imaging with indocyanine green (ICG) is increasingly being used in the field of image-guided surgery. Although ICG is considered non-nephrotoxic in current literature, caution is advised for the use of ICG in patients with advanced chronic kidney disease (CKD), including kidney transplant recipients. Therefore, a scoping review was performed to assess the safety of ICG in patients with advanced CKD or a renal allograft. This scoping review was guided by the PRISMA-ScR (Preferred Reporting Items for Systematic Reviews and Meta-analyses Extension for Scoping Reviews). Web of Science, PubMed, and Embase were searched for articles and abstracts in which ICG was administered in patients with CKD or a renal allograft. The extracted data included the incidence of adverse events, kidney function after injection of ICG, preservation of transplant function, and type of other possible complications. The initial search resulted in 635 records of which 19 studies were found eligible for the review. ICG was used for multiple purposes but never specifically as an objective to investigate possible nephrotoxicity. No adverse events were reported in the transplant group (n=250) or the CKD group (n=74). Despite ICG-injection, preservation of transplant function after transplantation surgery was 94% in 198 patients, and no increase in possible ICG-related other complications was reported. This scoping review found no evidence that ICG increases the risk of adverse events in patients with CKD, including kidney transplant recipients. Therefore, the administration of ICG should not be withheld from these patients.

Infective native aneurysms (INA) of the infrapopliteal arteries are rare and have previously been poorly described. This systematic review aims to provide an overview of the literature of this entity. Furthermore, two case reports of our own clinical experience are presented. PubMed, ScienceDirect, Cochrane, Ovid Embase, Ovid MEDLINE, and Web of Science were searched for articles on INAs of the infrapopliteal segment from January 1990 to September 2023. Article screening and selection were performed adhering to PRISMA guidelines. A total of 98 articles were screened and 20 were eligible for inclusion, of which all were case reports. In total, 22 patients with 28 infrapopliteal INAs were identified. The majority of INAs were located in the tibioperoneal trunk ( n = 10, 36%) followed by the posterior tibial artery ( n = 7, 25%). A current, or history of, infective endocarditis (IE) was described in 18 out of 22 patients (82%). Two patients died during hospitalization and one patient required a transfemoral amputation. A conservative antibiotic-only approach was chosen in three out of 28 INAs, two of which were the case reports described in this article; surgical or endovascular intervention was performed in 19 out of 28 aneurysms. No complications occurred in the conservative group, but one complication (transfemoral amputation) occurred in the interventional group. Infrapopliteal INA is a rare entity, and most described cases are precipitated by IE. Surgery or endovascular treatment might be indicated, but more research is warranted to define which patient would benefit and by what surgical approach.