Objective Perfusion Assessment in Gracilis Muscle Interposition—A Novel Software-Based Approach to Indocyanine Green Derived Near-Infrared Fluorescence in Reconstructive Surgery

Optimizing Indocyanine Green Dosage for Near-Infrared Fluorescence Perfusion Assessment in Bowel Anastomosis: A Prospective, Systematic Dose-Ranging Study

BACKGROUND

Indocyanine green (ICG) near-infrared fluorescence (NIRF) has emerged as a promising technique for visualizing tissue perfusion. However, within the wide range of dosages and imaging conditions currently being applied, the optimal dosage of ICG remains unclear. This study aimed to investigate the feasibility and implications of implementing lower dosages of ICG than commonly used for visual and quantitative perfusion assessment in a standardized setting.

METHODS

A prospective single-center cohort study was conducted on patients undergoing ileostomy reversal by hand-sewn anastomosis. ICG-NIRF visualization was performed before (T1) and after (T2) anastomosis with one of four different dosages of ICG (5 mg, 2.5 mg, 1.25 mg, or 0.625 mg) and recorded. Postoperatively, each visualization was evaluated for signal strength, completeness, and homogeneity of fluorescence. Additionally, perfusion graphs were generated by a software-based quantitative perfusion assessment, allowing an analysis of perfusion parameters. Statistical analysis comparing the effect of the investigated dosages on these parameters was performed.

RESULTS

In total, 40 patients were investigated. Visual evaluation demonstrated strong, complete, and homogeneous fluorescence signals across all dosages. Perfusion graph assessment revealed a consistent shape for all dosages (ingress followed by egress phase). While the average signal intensity decreased with dosage, it was sufficient to enable perfusion assessment even at the lowest dosages of 1.25 mg and 0.625 mg of ICG. The baseline intensity at T2 (the second intraoperative visualization) significantly decreased with dosage. The slope of the egress phase steepened with decreasing dosage.

CONCLUSIONS

Lower dosages of ICG were sufficient for intraoperative perfusion assessment, while causing lower residual fluorescence and quicker egress in subsequent visualizations.

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.

Indocyanine Green Fluorescence Guided Surgery in Colorectal Surgery

BACKGROUND

Indocyanine green (ICG) imaging has been increasingly used for intraoperative guidance in colorectal surgery over the past decade. The aim of this study was to review and organize, according to different type of use, all available literature on ICG guided colorectal surgery and highlight areas in need of further research and discuss future perspectives.

METHODS

PubMed, Scopus, and Google Scholar databases were searched systematically through November 2022 for all available studies on fluorescence-guided surgery in colorectal surgery.

RESULTS

Available studies described ICG use in colorectal surgery for perfusion assessment, ureteral and urethral assessment, lymphatic mapping, and hepatic and peritoneal metastases assessment. Although the level of evidence is low, results are promising, especially in the role of ICG in reducing anastomotic leaks.

CONCLUSIONS

ICG imaging is a safe and relatively cheap imaging modality in colorectal surgery, especially for perfusion assessment. Work is underway regarding its use in lymphatic mapping, ureter identification, and the assessment of intraperitoneal metastatic disease.

Feasibility of Novel Software-Based Perfusion Indicators for the Ileal J-Pouch-On the Path towards Objective and Quantifiable Intraoperative Perfusion Assessment with Indocyanine Green Near-Infrared Fluorescence

BACKGROUND

In restorative proctocolectomy with ileal J-pouch, perfusion assessment is vital to prevent complications such as anastomotic leak (AL). Indocyanine green near-infrared fluorescence (ICG-NIRF) is gaining popularity, while its interpretation and relevance remain subjective. This study aimed to evaluate a standardized ICG-NIRF imaging protocol combined with a novel, software-based assessment to detect areas of impaired perfusion and a possible correlation with AL of the pouch.

METHODS

In this prospective study, patients undergoing ileal J-pouch for ulcerative colitis at an inflammatory bowel disease (IBD) referral center were included. Intraoperatively, strictly standardized ICG-NIRF visualization was performed and video-recorded. Postoperatively, a specific software was utilized to determine the change in fluorescence intensity per second (i/s) for systematic regions of interest, generating perfusion-time curves and a pixel-to-pixel map. These were analysed in detail and correlated with clinical outcome (primary end point: AL within 30 days; clearly defined and screened for by pouchoscopy).

RESULTS

Four out of 18 included patients developed AL of the ileal pouch-anal anastomosis (IPAA). In the AL group, the perfusion curves on the area adjacent to the IPAA (pouch apex) displayed considerably lower ingress/inflow (median = 1.7; range = 8.5; interquartile-range = 3.8 i/s) and egress/outflow (median = -0.1; range = 0.7; interquartile-range = 0.5 i/s) values than in the non-AL group (ingress: median = 4.3; range = 10.3; interquartile-range = 4.0 i/s); egress: median = (-1.1); range = 3.9; interquartile range = 1.0 i/s). This was confirmed by further novel parameters of pouch perfusion (maximum ingress; maximum egress) and pixel-to-pixel analysis.

CONCLUSIONS

This study presents the feasibility of a novel methodology to precisely assess pouch perfusion with ICG-NIRF, identifying comparable, quantifiable, and objective parameters to potentially detect perfusion-associated complications in surgery in real-time.