[Possibilities and perspectives of hyperspectral imaging in visceral surgery]

Optimization of anastomotic technique and gastric conduit perfusion with hyperspectral imaging and machine learning in an experimental model for minimally invasive esophagectomy

INTRODUCTION

Esophagectomy is the mainstay of esophageal cancer treatment, but anastomotic insufficiency related morbidity and mortality remain challenging for patient outcome. Therefore, the objective of this work was to optimize anastomotic technique and gastric conduit perfusion with hyperspectral imaging (HSI) for total minimally invasive esophagectomy (MIE) with linear stapled anastomosis.

MATERIAL AND METHODS

A live porcine model (n = 58) for MIE was used with gastric conduit formation and simulation of linear stapled side-to-side esophagogastrostomy. Four main experimental groups differed in stapling length (3 vs. 6 cm) and simulation of anastomotic position on the conduit (cranial vs. caudal). Tissue oxygenation around the anastomotic simulation site was evaluated using HSI and was validated with histopathology.

RESULTS

The tissue oxygenation (ΔStO₂) after the anastomotic simulation remained constant only for the short stapler in caudal position (-0.4 ± 4.4%, n.s.) while it was impaired markedly in the other groups (short-cranial: -15.6 ± 11.5%, p = 0.0002; long-cranial: -20.4 ± 7.6%, p = 0.0126; long-caudal: -16.1 ± 9.4%, p < 0.0001). Tissue samples from avascular stomach as measured by HSI showed correspondent eosinophilic pre-necrotic changes in 35.7 ± 9.7% of the surface area.

CONCLUSION

Tissue oxygenation at the site of anastomotic simulation of the gastric conduit during MIE is influenced by stapling technique. Optimal oxygenation was achieved with a short stapler (3 cm) and sufficient distance of the simulated anastomosis to the cranial end of the gastric conduit. HSI tissue deoxygenation corresponded to histopathologic necrotic tissue changes. The experimental model with HSI and ML allow for systematic optimization of gastric conduit perfusion and anastomotic technique while clinical translation will have to be proven.

Hyperspectral imaging enables the differentiation of differentially inflated and perfused pulmonary tissue: a proof-of-concept study in pulmonary lobectomies for intersegmental plane mapping

OBJECTIVES

The identification of the intersegmental plane is a major interoperative challenges during pulmonary segmentectomies. The objective of this pilot study is to test the feasibility of lung perfusion assessment by Hyperspectral Imaging for identification of the intersegmental plane.

METHODS

A pilot study (clinicaltrials.org: NCT04784884) was conducted in patients with lung cancer. Measuring tissue oxygenation (StO₂; upper tissue perfusion), organ hemoglobin index (OHI), near-infrared index (NIR; deeper tissue perfusion) and tissue water index (TWI), the Hyperspectral Imaging measurements were carried out in inflated (P_vent) and deflated pulmonary lobes (P_nV) as well as in deflated pulmonary lobes with divided circulation (P_nVC) before dissection of the lobar bronchus.

RESULTS

A total of 341 measuring points were evaluated during pulmonary lobectomies. Pulmonary lobes showed a reduced StO2 (P_vent: 84.56% ± 3.92 vs. P_nV: 63.62% ± 11.62 vs. P_nVC: 39.20% ± 23.57; p<0.05) and NIR-perfusion (P_vent: 50.55 ± 5.62 vs. P_nV: 47.55 ± 3.38 vs. P_nVC: 27.60 ± 9.33; p<0.05). There were no differences of OHI and TWI between the three groups.

CONCLUSIONS

This pilot study demonstrates that HSI enables differentiation between different ventilated and perfused pulmonary tissue as a precondition for HSI segment mapping.

Intraoperative Determination of Bronchus Stump and Anastomosis Perfusion with Hyperspectral Imaging

BACKGROUND

The intraoperative evaluation of bronchus perfusion is limited. Hyperspectral Imaging (HSI) is a newly established intraoperative imaging technique that enables a non-invasive, real-time perfusion analysis. Therefore, the purpose of this study was to determine the intraoperative perfusion of bronchus stump and anastomosis during pulmonary resections with HSI.

METHODS

In this prospective, IDEAL Stage 2a study (Clinicaltrials.gov: NCT04784884) HSI measurements were carried out before bronchial dissection and after bronchial stump formation or bronchial anastomosis, respectively. Tissue oxygenation (StO₂; upper tissue perfusion), organ hemoglobin index (OHI), near-infrared index (NIR; deeper tissue perfusion) and tissue water index (TWI) were calculated.

RESULTS

Bronchus stumps showed a reduced NIR (77.82 ± 10.27 vs 68.01 ± 8.95; P = 0,02158) and OHI (48.60 ± 1.39 vs 38.15 ± 9.74; P = <.0001), although the perfusion of the upper tissue layers was equivalent before and after resection (67.42% ± 12.53 vs 65.91% ± 10.40). In the sleeve resection group, we found both a significant decrease in StO 2 and NIR between central bronchus and anastomosis region (StO₂: 65.09% ± 12.57 vs 49.45 ± 9.94; P = .044; NIR: 83.73 ± 10.92 vs 58.62 ± 3.01; P = .0063). Additionally, NIR was decreased in the re-anastomosed bronchus compared to central bronchus region (83.73 ± 10.92 vs 55.15 ± 17.56; P = .0029).

CONCLUSIONS

Although both bronchus stumps and anastomosis show an intraoperative reduction of tissue perfusion, there is no difference of tissue hemoglobin level in bronchus anastomosis.

Hyperspectral Imaging-A Novel Tool to Assess Tissue Perfusion and Oxygenation in Esophageal Anastomoses

Anastomotic stricture and leakage are common complications after repair of esophageal atresia (EA). A compromised perfusion of the anastomosis is a contributing factor. Hyperspectral imaging (HSI) is an ultrashort noninvasive method to measure tissue perfusion. We present two cases of with tracheoesophageal fistula (TEF)/EA repair, in whom we applied HSI: the first patient was a newborn with EA type C who underwent open TEF repair. The second one had an EA type A and cervical esophagostomy, in whom we performed gastric transposition. In both patients, HSI confirmed a good tissue perfusion of the later anastomosis. The postoperative course was uneventful and both patients are on full enteral feeds. We conclude that HSI is a safe and noninvasive tool that allows near real-time assessment of tissue perfusion and can contribute to the identification of the optimal anastomotic region during pediatric esophageal surgery.

Leberchirurgie 4.0 - OP-Planung, Volumetrie, Navigation und Virtuelle Realität

Durch die Optimierung der konservativen Behandlung, die Verbesserung der bildgebenden Verfahren und die Weiterentwicklung der Operationstechniken haben sich das operative Spektrum sowie der Maßstab für die Resektabilität in Bezug auf die Leberchirurgie in den letzten Jahrzehnten deutlich verändert.

Dank zahlreicher technischer Entwicklungen, insbesondere der 3-dimensionalen Segmentierung, kann heutzutage die präoperative Planung und die Orientierung während der Operation selbst, vor allem bei komplexen Eingriffen, unter Berücksichtigung der patientenspezifischen Anatomie erleichtert werden.

Neue Technologien wie 3-D-Druck, virtuelle und augmentierte Realität bieten zusätzliche Darstellungsmöglichkeiten für die individuelle Anatomie. Verschiedene intraoperative Navigationsmöglichkeiten sollen die präoperative Planung im Operationssaal verfügbar machen, um so die Patientensicherheit zu erhöhen.

Dieser Übersichtsartikel soll einen Überblick über den gegenwärtigen Stand der verfügbaren Technologien sowie einen Ausblick in den Operationssaal der Zukunft geben.

Hyperspectral Imaging (HSI) of Human Kidney Allografts

OBJECTIVE

Aim of our study was to test a noninvasive HSI technique as an intraoperative real time assessment tool for deceased donor kidney quality and function in human kidney allotransplantation.

SUMMARY OF BACKGROUND DATA

HSI is capable to deliver quantitative diagnostic information about tissue pathology, morphology, and composition, based on the spectral characteristics of the investigated tissue. Because tools for objective intraoperative graft viability and performance assessment are lacking, we applied this novel technique to human kidney transplantation.

METHODS

Hyperspectral images of distinct components of kidney allografts (parenchyma, ureter) were acquired 15 and 45 minutes after reperfusion and subsequently analyzed using specialized HSI acquisition software capable to compute oxygen saturation levels (StO2), near infrared perfusion indices (NIR), organ hemoglobin indices, and tissue water indices of explored tissues.

RESULTS

Seventeen kidney transplants were analyzed. Median recipient and donor age were 55 years. Cold ischemia time was 10.8 ± 4.1 hours and anastomosis time was 35 ± 7 minutes (mean ± standard deviation). Two patients (11.8%) developed delayed graft function (DGF). cold ischemia time was significantly longer (18.6 ± 1.6) in patients with DGF (P < 0.01). Kidneys with DGF furthermore displayed significant lower StO2 (P = 0.02) and NIR perfusion indices, 15 minutes after reperfusion (P < 0.01). Transplant ureters displayed a significant decrease of NIR perfusion with increased distance to the renal pelvis, identifying well and poor perfused segments.

CONCLUSION

Intraoperative HSI is feasible and meaningful to predict DGF in renal allografts. Furthermore, it can be utilized for image guided surgery, providing information about tissue oxygenation, perfusion, hemoglobin concentration, and water concentration, hence allowing intraoperative viability assessment of the kidney parenchyma and the ureter.

Spectral organ fingerprints for machine learning-based intraoperative tissue classification with hyperspectral imaging in a porcine model

Visual discrimination of tissue during surgery can be challenging since different tissues appear similar to the human eye. Hyperspectral imaging (HSI) removes this limitation by associating each pixel with high-dimensional spectral information. While previous work has shown its general potential to discriminate tissue, clinical translation has been limited due to the method’s current lack of robustness and generalizability. Specifically, the scientific community is lacking a comprehensive spectral tissue atlas, and it is unknown whether variability in spectral reflectance is primarily explained by tissue type rather than the recorded individual or specific acquisition conditions. The contribution of this work is threefold: (1) Based on an annotated medical HSI data set (9059 images from 46 pigs), we present a tissue atlas featuring spectral fingerprints of 20 different porcine organs and tissue types. (2) Using the principle of mixed model analysis, we show that the greatest source of variability related to HSI images is the organ under observation. (3) We show that HSI-based fully-automatic tissue differentiation of 20 organ classes with deep neural networks is possible with high accuracy (> 95%). We conclude from our study that automatic tissue discrimination based on HSI data is feasible and could thus aid in intraoperative decisionmaking and pave the way for context-aware computer-assisted surgery systems and autonomous robotics.

Hyperspectral imaging detects perfusion and oxygenation differences between stapled and hand-sewn intestinal anastomoses

OBJECTIVES

Hand-sewn and stapled intestinal anastomoses are both daily performed routine procedures by surgeons. Yet, differences in micro perfusion of these two surgical techniques and their impact on surgical outcomes are still insufficiently understood. Only recently, hyperspectral imaging (HSI) has been established as a non-invasive, contact-free, real-time assessment tool for tissue oxygenation and micro-perfusion. Hence, objective of this study was HSI assessment of different intestinal anastomotic techniques and analysis of patients' clinical outcome.

METHODS

Forty-six consecutive patients with an ileal-ileal anastomoses were included in our study; 21 side-to-side stapled and 25 end-to-end hand-sewn. Based on adsorption and reflectance of the analyzed tissue, chemical color imaging indicates oxygen saturation (StO2), tissue perfusion (near-infrared perfusion index [NIR]), organ hemoglobin index (OHI), and tissue water index (TWI).

RESULTS

StO2 as well as NIR of the region of interest (ROI) was significantly higher in stapled anastomoses as compared to hand-sewn ileal-ileal anastomoses (StO2 0.79 (0.74-0.81) vs. 0.66 (0.62-0.70); p<0.001 NIR 0.83 (0.70-0.86) vs. 0.70 (0.63-0.76); p=0.01). In both groups, neither anastomotic leakage nor abdominal septic complications nor patient death did occur.

CONCLUSIONS

Intraoperative HSI assessment is able to detect significant differences in tissue oxygenation and NIR of hand-sewn and stapled intestinal anastomoses. Long-term clinical consequences resulting from the reduced tissue oxygenation and tissue perfusion in hand-sewn anastomoses need to be evaluated in larger clinical trials, as patients may benefit from further refined surgical techniques.

Hyperspectral Imaging for Assessment of Initial Graft Function in Human Kidney Transplantation

The aim of our study was to evaluate hyperspectral imaging (HSI) as a rapid, non-ionizing technique for the assessment of organ quality and the prediction of delayed graft function (DGF) in kidney transplantation after static cold storage (SCS, n = 20), as well as hypothermic machine perfusion (HMP, n = 18). HSI assessment of the kidney parenchyma was performed during organ preservation and at 10 and 30 min after reperfusion using the TIVITA^® Tissue System (Diaspective Vision GmbH, Am Salzhaff, Germany), calculating oxygen saturation (StO₂), near-infrared perfusion index (NIR), tissue haemoglobin index (THI), and tissue water index (TWI). Recipient and donor characteristics were comparable between organ preservation groups. Cold ischemic time was significantly longer in the HMP group (14.1 h [3.6–23.1] vs. 8.7h [2.2–17.0], p = 0.002). The overall presence of DGF was comparable between groups (HMP group n = 10 (55.6%), SCS group n = 10 (50.0%)). Prediction of DGF was possible in SCS and HMP kidneys; StO₂ at 10 (50.00 [17.75–76.25] vs. 63.17 [27.00–77.75]%, p = 0.0467) and 30 min (57.63 [18.25–78.25] vs. 65.38 [21.25–83.33]%, p = 0.0323) after reperfusion, as well as NIR at 10 (41.75 [1.0–58.00] vs. 48.63 [12.25–69.50], p = 0.0137) and 30 min (49.63 [8.50–66.75] vs. 55.80 [14.75–73.25], p = 0.0261) after reperfusion were significantly lower in DGF kidneys, independent of the organ preservation method. In conclusion, HSI is a reliable method for intraoperative assessment of renal microperfusion, applicable after organ preservation through SCS and HMP, and predicts the development of DGF.

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.

Hyperspectral Imaging: A New Intraoperative Tool for Pouch Assessment in Patients Undergoing Restorative Proctocolectomy

Introduction

Restorative proctocolectomy with ileal pouch-anal anastomosis (IPAA) is a challenging operation. Especially the mobilization of the pouch into the pelvis can be complex. Adequate perfusion of the pouch is required for optimal healing and functioning.

Methods

With hyperspectral imaging (HSI) wavelengths between 500 and 1,000 nm can be analyzed in addition to visible light and by reflecting patterns. This intraoperative procedure is non-invasive, contact-free, and no contrast medium is needed. Fifteen patients undergoing IPAA were examined prospectively, and the pouch was evaluated by HSI intraoperatively. HSI was measured in standardized fashion at 4 defined locations of the J-pouch. Each measurement took about 10 s. The clinical postoperative course was assessed in all patients and correlated to the intraoperative HSI findings.

Results

Mean near-infrared perfusion and oxygenation of patients showed values ≥74% for all defined pouch areas, revealing good blood supply. Three minor anastomotic leaks were detected by standard pouchoscopy in the postoperative course, which could be treated conservatively with endosponge therapy.

Conclusion

HSI values of perfusion and oxygenation of the IPAA were high. The leak rate is associated with redo procedures. This is reflected by the current literature and most likely related to the higher complexity of the revisional pouch operation. HSI has proved itself as a quick and effective new intraoperative tool to evaluate pouch perfusion objectively and quantitatively.

[New intraoperative fluorescence-based and spectroscopic imaging techniques in visceral medicine - precision surgery in the "high tech"-operating room]

INTRODUCTION

Fluorescence angiography (FA) with indocyanine green (ICG) and hyperspectral imaging (HSI) are novel intraoperative visualization techniques in abdominal, vascular and transplant surgery. With the purpose of precision surgery, and in order to increase patient's safety, these new tools aim at reducing postoperative morbidity and mortality. This review discusses and highlights recent developments and the future potential of real-time imaging modalities.

METHODS

The underlying mechanisms of the novel imaging methods and their clinical impact are displayed in the context of avoiding anastomotic leaks, the most momentous complications in gastrointestinal surgery after oncologic resections.

RESULTS

While FA is associated with the admission of a fluorescence agent, HSI is contact-free and non-invasive. Both methods are able to record physiological tissue properties in real-time. Additionally, FA also measures dynamic phenomena. The techniques take a few seconds only and do not hamper the operative workflow considerably. With regard to a potential change of the surgical strategy, FA and HSI have an equal significance. Our own advancements reflect, in particular, the topics of data visualization and automated data analyses together with the implementation of artificial intelligence (AI) and minimalization of the current devices to install them into endoscopes, minimal-invasive and robot-guided surgery.

CONCLUSION

There are a limited number of studies in the field of intraoperative imaging techniques. Whether precision surgery in the "high-tech" OR together with FA, HSI and robotics will result in more secure operative procedures to minimize the postoperative morbidity and mortality will have to be evaluated in future multicenter trials.

Usability of Indocyanine Green in Robot-Assisted Hepatic Surgery

Recent developments in robotic surgery have led to an increasing number of robot-assisted hepatobiliary procedures. However, a limitation of robotic surgery is the missing haptic feedback. The fluorescent dye indocyanine green (ICG) may help in this context, which accumulates in hepatocellular cancers and around hepatic metastasis. ICG accumulation may be visualized by a near-infrared camera integrated into some robotic systems, helping to perform surgery more accurately. We aimed to test the feasibility of preoperative ICG application and its intraoperative use in patients suffering from hepatocellular carcinoma and metastasis of colorectal cancer, but also of other origins. In a single-arm, single-center feasibility study, we tested preoperative ICG application and its intraoperative use in patients undergoing robot-assisted hepatic resections. Twenty patients were included in the final analysis. ICG staining helped in most cases by detecting a clear lesion or additional metastases or when performing an R0 resection. However, it has limitations if applied too late before surgery and in patients suffering from severe liver cirrhosis. ICG staining may serve as a beneficial intraoperative aid in patients undergoing robot-assisted hepatic surgery. Dose and time of application and standardized fluorescence intensity need to be further determined.

Comparison of hyperspectral imaging and fluorescence angiography for the determination of the transection margin in colorectal resections-a comparative study

PURPOSE

One relevant aspect for anastomotic leakage in colorectal surgery is blood perfusion of both ends of the anastomosis. The clinical evaluation of this issue is limited, but new methods like fluorescence angiography with indocyanine green or non-invasive and contactless hyperspectral imaging have evolved as objective parameters for perfusion evaluation.

METHODS

In this prospective, non-randomized, open-label and two-arm study, fluorescence angiography and hyperspectral imaging were compared in 32 consecutive patients with each other and with the clinical assessment by the surgeon. After preparation of the bowel and determination of the surgical resection line, the tissue was evaluated with hyperspectral imaging for 5 min before and after cutting the marginal artery and assessed by 6 hyperspectral pictures followed by fluorescence angiography with indocyanine green.

RESULTS

In 30 of 32 patients, the image data could be evaluated and compared. Both methods provided a comparable borderline between well-perfused and poorly perfused tissue (p = 0.704). In 15 cases, the surgical resection line was shifted to the central position due to the imaging. The border zone was sharper in fluorescence angiography and best assessed 31 s after injection. With hyperspectral imaging, the border zone was visualized wider and with more differences between proximal and distal border.

CONCLUSION

Hyperspectral imaging and fluorescence angiography provide similar results in determining the perfusion border. Both methods allow a good and safe visualization of the blood perfusion at the central resection margin to create a well-perfused anastomosis.

TRIAL REGISTRATION

This study was registered at Clinicaltrials.gov ( NCT04226781 ) on January 13, 2020.

[Indocyanine green fluorescence staining in liver surgery]

BACKGROUND

Indocyanine green (ICG) opens up numerous possibilities for applications in hepatobiliary surgery, due to its exclusive hepatic excretion and its fluorescence properties in the near infrared (NIR) spectrum.

OBJECTIVE

Systematic review of the literature on the application of ICG imaging in open and laparoscopic liver surgery.

MATERIAL AND METHODS

Literature review and summary of the recent scientific original articles and reviews.

RESULTS

The ICG fluorescence imaging is increasingly being used in liver surgery. It allows real-time display of the segmental anatomy of the liver. Moreover, depending on the tumor entity, direct or indirect visualization of liver tumors and metastases is also possible. The detection of bile leaks might also be facilitated. Recent experiences in liver surgery have shown that ICG imaging enables a more sensitive intraoperative detection of additional foci and probably also a higher R0 resection rate; however, the application is mainly helpful for superficial lesions, since the depth of penetration of NIR is only 8-10 mm.

CONCLUSION

Fluorescence staining using ICG is a valuable supplementary tool in modern liver surgery. It is particularly helpful in laparoscopic surgery where tactile control is eliminated and three-dimensional orientation is difficult. These disadvantages can be partially compensated by additional real-time imaging using ICG.

[Digitalization and use of artificial intelligence in microvascular reconstructive facial surgery]

BACKGROUND

When using digitalization and artificial intelligence (AI), large amounts of data (big data) are produced, which can be processed by computers and used in the field of microvascular-reconstructive craniomaxillofacial surgery (CMFS).

OBJECTIVE

The aim of this article is to summarize current applications of digitalized medicine and AI in microvascular reconstructive CMFS.

MATERIAL AND METHODS

Review of frequent applications of digital medicine for microvascular CMFS reconstruction, focusing on digital planning, navigation, robotics and potential applications with AI.

RESULTS

The broadest utilization of medical digitalization is in the virtual planning of microvascular transplants, individualized implants and template-guided reconstruction. Navigation is commonly used for ablative tumor surgery but less frequently in reconstructions. Robotics are mainly employed in the transoral approach for tumor surgery of the hypopharynx, whereas the use of AI is still limited even if possible applications would be automated virtual planning and monitoring systems.

CONCLUSION

The use of digitalized methods and AI are adjuncts to microvascular reconstruction. Automatization approaches and simplification of technologies will provide such applications to a broader clientele in the future; however, in CMFS, robotic-assisted resections and automated flap monitoring are not yet the standard of care.