Alternative intraoperative optical imaging modalities for fluorescence angiography in gastrointestinal surgery: spectral imaging and imaging photoplethysmography.

INTRODUCTION: Intraoperative near-infrared fluorescence angiography with indocyanine green (ICG-FA) is a well-established modality in gastrointestinal surgery. Its main drawback is the application of a fluorescent agent with possible side effects for patients. The goal of this review paper is the presentation of alternative, non-invasive optical imaging methods and their comparison with ICG-FA. MATERIAL AND METHODS: The principles of ICG-FA, spectral imaging, imaging photoplethysmography (iPPG), and their applications in gastrointestinal surgery are described based on selected published works. RESULTS: The main applications of the three modalities are the evaluation of tissue perfusion, the identification of risk structures, and tissue segmentation or classification. While the ICG-FA images are mainly evaluated visually, leading to subjective interpretations, quantitative physiological parameters and tissue segmentation are provided in spectral imaging and iPPG. The combination of ICG-FA and spectral imaging is a promising method. CONCLUSIONS: Non-invasive spectral imaging and iPPG have shown promising results in gastrointestinal surgery. They can overcome the main drawbacks of ICG-FA, i.e. the use of contrast agents, the lack of quantitative analysis, repeatability, and a difficult standardization of the acquisition. Further technical improvements and clinical evaluations are necessary to establish them in daily clinical routine.

New Intraoperative Imaging Tools and Image-Guided Surgery in Gastric Cancer Surgery.

Innovations and new advancements in intraoperative real-time imaging have gained significant importance in the field of gastric cancer surgery in the recent past. Currently, the most promising procedures include indocyanine green fluorescence imaging (ICG-FI) and hyperspectral imaging or multispectral imaging (HSI, MSI). ICG-FI is utilized in a broad range of clinical applications, e.g., assessment of perfusion or lymphatic drainage, and additional implementations are currently investigated. HSI is still in the experimental phase and its value and clinical relevance require further evaluation, but initial studies have shown a successful application in perfusion assessment, and prospects concerning non-invasive tissue and tumor classification are promising. The application of machine learning and artificial intelligence technologies might enable an automatic evaluation of the acquired image data in the future. Both methods facilitate the accurate visualization of tissue characteristics that are initially indistinguishable for the human eye. By aiding surgeons in optimizing the surgical procedure, image-guided surgery can contribute to the oncologic safety and reduction of complications in gastric cancer surgery and recent advances hold promise for the application of HSI in intraoperative tissue diagnostics.

[Status of minimally invasive gastrectomy : Current advancements: robotic surgery and intraoperative imaging for gastric cancer]. / Stellenwert der minimal-invasiven Gastrektomie : Aktuelle Weiterentwicklungen: Robotik und intraoperatives Imaging beim Magenkarzinom.

The surgical treatment of gastric cancer has arrived at a turning point towards the routine application of minimally invasive techniques. After the first results of prospective randomized trials from Asia confirmed the surgical and oncological safety, the latest results of international trials provided evidence for minimally invasive gastrectomy of advanced gastric cancer in a multimodal setting. A new addition in the field of minimally invasive procedures is robotic-assisted surgical techniques, which have already been implemented for these indications in many centers in Germany. The technical advantages that are applicable in the robotics setting in comparison to laparoscopy lead to a rapid dissemination of the procedure but still need to be evaluated in controlled trials. Further developments for the surgical treatment of gastric cancer are found in the field of intraoperative imaging procedures. In this field various technologies are available, such as fluorescence imaging using a near-infrared camera, which requires the use of a fluorescent agent or the hyperspectral camera system, which does not require the application of a fluorophore and merges pictures from visible and non-visible wavelengths to a functional image. It is to be expected that in the future various technological advancements can make a valuable contribution to the surgical treatment of gastric cancer in the clinical routine, especially if they support and facilitate the use of minimally invasive surgical techniques.

Novel Intraoperative Imaging of Gastric Tube Perfusion during Oncologic Esophagectomy-A Pilot Study Comparing Hyperspectral Imaging (HSI) and Fluorescence Imaging (FI) with Indocyanine Green (ICG).

BACKGROUND: Novel intraoperative imaging techniques, namely, hyperspectral (HSI) and fluorescence imaging (FI), are promising with respect to reducing severe postoperative complications, thus increasing patient safety. Both tools have already been used to evaluate perfusion of the gastric conduit after esophagectomy and before anastomosis. To our knowledge, this is the first study evaluating both modalities simultaneously during esophagectomy. METHODS: In our pilot study, 13 patients, who underwent Ivor Lewis esophagectomy and gastric conduit reconstruction, were analyzed prospectively. HSI and FI were recorded before establishing the anastomosis in order to determine its optimum position. RESULTS: No anastomotic leak occurred during this pilot study. In five patients, the imaging methods resulted in a more peripheral adaptation of the anastomosis. There were no significant differences between the two imaging tools, and no adverse events due to the imaging methods or indocyanine green (ICG) injection occurred. CONCLUSIONS: Simultaneous intraoperative application of both modalities was feasible and not time consuming. They are complementary with regard to the ideal anastomotic position and may contribute to better surgical outcomes. The impact of their simultaneous application will be proven in consecutive prospective trials with a large patient cohort.