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

NIR-II imaging-based detection of early changes in lower limb perfusion in type 2 diabetes patients without peripheral artery disease

AIMS

The formation of lower limb arterial plaques, exacerbated by type 2 diabetes (T2D), represents an early stage of lower limb peripheral artery disease (PAD). Second near-infrared region (NIR-II) imaging is an emerging technique with high sensitivity for detecting perfusion levels. This study explores the value of NIR-II imaging in identifying perfusion changes due to lower extremity arterial plaques in T2D patients without PAD.

METHODS

NIR-II imaging with indocyanine green (ICG) was conducted on 120 T2D patients, who were categorized into two groups: plaque and non-plaque. NIR-II parameters and clinical characteristics were analyzed between the two groups to identify significant predictors of lower extremity arterial plaques.

RESULTS

Six NIR-II imaging parameters (T start, T 1/2, Tmax, Ingress rate, Egress, and Egress rate) showed significant differences and diagnostic efficacy between the two groups. Three NIR-II parameters (T start, Egress, and Egress rate) and two clinical characteristics (age and sex) were identified as independent predictors of lower limb artery plaques. The nomogram showed that a combined model with NIR-II parameters and clinical characteristics exhibited higher diagnostic efficacy.

CONCLUSION

NIR-II imaging can effectively detect early perfusion changes in T2D patients, showing great potential for pre-diagnosis of individuals at high risk for PAD.

Establishing reference curves for vital tissue perfusion using quantitative near-infrared fluorescence imaging with indocyanine green

PURPOSE

Assessment of tissue perfusion using near-infrared fluorescence (NIR) with indocyanine green (ICG) is gaining popularity, however reliable and objective interpretation remains a challenge. Therefore, this study aimed to establish reference curves for vital tissue perfusion across target tissues using this imaging modality.

METHODS

Data from five prospective study cohorts conducted in three Dutch academic medical centres between December 2018 and June 2023 was included. Quantitative analysis using time-intensity curves was performed in ten target tissues, including the colon, ileum, gastric conduit, deep inferior epigastric artery perforator (DIEP) flap, skin of the foot, trachea, sternocleidomastoid muscle (SCM), carotid artery, parathyroid gland, and skin of the neck.

RESULTS

A total of 178 patients were included in this study, representing 303 target tissues. Three different patterns of reference curves were identified based on a subjective assessment. Seven out of ten tissues showed a reference curve with rapid inflow (median time-to-max (tmax): 13.0-17.8 s, median maximum-normalized-slope (slope norm): 10.6-12.6%/sec), short outflow (median area-under-the-curve of tmax + 60 s (AUC60): 65.0-85.1%) followed by a gradual/absent outflow. Secondly, the DIEP flap and SCM tissue showed a reference curve with longer inflow (median tmax: 24.0, 22.0 s, median slope norm: 9.3, 9.7%/sec respectively) and reduced outflow (median AUC60: 89.1, 89.0% respectively). Thirdly, the skin of the foot showed slow inflow (median tmax 141.1 s, median norm slope 2.1%/sec) without outflow.

CONCLUSION

This study demonstrates reference curves for vital tissue perfusion of multiple target tissues identified with ICG NIR fluorescence imaging, providing a critical step towards the clinical implementation of this technique.

Case Report: The application of novel imaging technologies in lower extremity peripheral artery disease: NIR-II imaging, OCTA, and LSFG

Lower extremity peripheral artery disease (PAD) is a growing global health problem. New methods to diagnose PAD have been explored in recent years. At present, the majority of imaging methods for PAD focus on the macrovascular blood flow, and the exploration of microcirculation and tissue perfusion of PAD remains largely insufficient. In this report, we applied three new imaging technologies, i.e., second near-infrared region (NIR-II, 900-1,880 nm wavelengths) imaging, optical coherence tomography angiography (OCTA), and laser speckle flowgraphy (LSFG), in a PAD patient with a healthy human subject as control. Our results showed that the PAD patient had poorer tissue perfusion than the control without observed adverse effects. Moreover, compared with the first near-infrared region (NIR-I, 700-900 nm wavelengths) imaging results, NIR-II imaging had a higher signal-to-background ratio and resolution than NIR-I imaging and detected microvessels that were not detected by NIR-I imaging. These observations suggested that NIR-II imaging, OCTA, and LSFG are potentially safe and effective methods for diagnosing PAD.

A quantitative assessment of perfusion of the gastric conduit after oesophagectomy using near-infrared fluorescence with indocyanine green

INTRODUCTION

Anastomotic leakage is a severe complication after oesophageal resection with gastric conduit reconstruction. Poor perfusion of the gastric conduit plays an important role in the development of anastomotic leakage. Quantitative near-infrared (NIR) fluorescence angiography with indocyanine green (ICG-FA) is an objective technique that can be used for perfusion assessment. This study aims to assess perfusion patterns of the gastric conduit with quantitative ICG-FA.

METHODS

In this exploratory study, 20 patients undergoing oesophagectomy with gastric conduit reconstruction were included. A standardized NIR ICG-FA video of the gastric conduit was recorded. Postoperatively, the videos were quantified. Primary outcomes were the time-intensity curves and nine perfusion parameters from contiguous regions of interest on the gastric conduit. A secondary outcome was the inter-observer agreement of subjective interpretation of the ICG-FA videos between six surgeons. The inter-observer agreement was tested with an intraclass correlation coefficient (ICC).

RESULTS

In a total of 427 curves, three distinct perfusion patterns were recognized: pattern 1 (steep inflow, steep outflow); pattern 2 (steep inflow, minor outflow); and pattern 3 (slow inflow, no outflow). All perfusion parameters were significantly different between the perfusion patterns. The inter-observer agreement was poor - moderate (ICC:0.345,95%CI:0.164-0.584).

DISCUSSION

This was the first study to describe perfusion patterns of the complete gastric conduit after oesophagectomy. Three distinct perfusion patterns were observed. The poor inter-observer agreement of the subjective assessment underlines the need for quantification of ICG-FA of the gastric conduit. Further studies should evaluate the predictive value of perfusion patterns and parameters on anastomotic leakage.

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.

Near-Infrared Fluorescence with Indocyanine Green to Assess Bone Perfusion: A Systematic Review

Background: Adequate perfusion of a bone flap is essential for successful reconstruction of osseous defects. Unfortunately, complications related to inadequate bone perfusion are common. Near-infrared fluorescence (NIRF) imaging enables intraoperative visualization of perfusion. NIRF has been investigated in reconstructive surgery to aid the surgeon in clinical perioperative assessment of soft tissue perfusion. However, little is known on the beneficial use of NIRF to assess bone perfusion. Therefore, the aim of this review was to search for studies evaluating NIRF to assess bone perfusion. Methods: A systematic review, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline, was performed. Studies up to October 2021 were included. We extracted data regarding the study population, size and design, reported objective fluorescence parameters and the methodology used for fluorescence imaging and processing. Results: Ten articles were included. Studies reported unevenly on the protocol used for NIRF imaging. Five studies reported objective parameters. Absolute and relative perfusion parameters and parameters derived from maximum fluorescence were reported. The clinical significance of these parameters has not been evaluated in humans. Conclusion: The evidence on bone perfusion as measured with NIRF is limited. More clinical studies are required.