Assessing intraoperative blood flow in cardiovascular surgery

Intraoperative Blood Flow Evaluation Using Indocyanine Green Fluorescence Angiography for the Surgical Reconstruction of a Hilar Renal Artery Aneurysm

Surgical reconstruction is one of the standard treatments for renal artery aneurysm. However, its intraoperative evaluation is sometimes difficult depending on the operative field, aneurysm morphology, and peripheral blood vessel distribution. This case demonstrated that after renal artery reconstruction, indocyanine green fluorescence angiography is used to evaluate the results of repairing. This method is useful in visceral aneurysm evaluation not only for assessing reconstructed blood flow but also for confirming tissue perfusion of the renal parenchyma.

Tumor Segmentation in Intraoperative Fluorescence Images Based on Transfer Learning and Convolutional Neural Networks

OBJECTIVE

To propose a transfer learning based method of tumor segmentation in intraoperative fluorescence images, which will assist surgeons to efficiently and accurately identify the boundary of tumors of interest.

METHODS

We employed transfer learning and deep convolutional neural networks (DCNNs) for tumor segmentation. Specifically, we first pre-trained four networks on the ImageNet dataset to extract low-level features. Subsequently, we fine-tuned these networks on two fluorescence image datasets (ABFM and DTHP) separately to enhance the segmentation performance of fluorescence images. Finally, we tested the trained models on the DTHL dataset. The performance of this approach was compared and evaluated against DCNNs trained end-to-end and the traditional level-set method.

RESULTS

The transfer learning-based UNet++ model achieved high segmentation accuracies of 82.17% on the ABFM dataset, 95.61% on the DTHP dataset, and 85.49% on the DTHL test set. For the DTHP dataset, the pre-trained Deeplab v3 + network performed exceptionally well, with a segmentation accuracy of 96.48%. Furthermore, all models achieved segmentation accuracies of over 90% when dealing with the DTHP dataset.

CONCLUSION

To the best of our knowledge, this study explores tumor segmentation on intraoperative fluorescent images for the first time. The results show that compared to traditional methods, deep learning has significant advantages in improving segmentation performance. Transfer learning enables deep learning models to perform better on small-sample fluorescence image data compared to end-to-end training. This discovery provides strong support for surgeons to obtain more reliable and accurate image segmentation results during surgery.

Realtime assessment of vascular occlusion and reperfusion in animal models of intraoperative imaging - a pilot study

Objectives

Intraoperative monitoring of blood flow (BF) remains vital to guiding surgical decisions. Here, we report the use of SurgeON™ Blood Flow Monitor (BFM), a prototype system that attaches to surgical microscopes and implements laser speckle contrast imaging (LSCI) to noninvasively obtain and present vascular BF information in real-time within the microscope's eyepiece.

Methods

The ability of SurgeON BFM to monitor BF status during reversible vascular occlusion procedures was investigated in two large animal models: occlusion of saphenous veins in six NZW rabbit hindlimbs and clipping of middle cerebral artery (MCA) branches in four Dorset sheep brain hemispheres. SurgeON BFM acquired, presented, and stored LSCI-based blood flow velocity index (BFVi) data and performed indocyanine green video angiography (ICG-VA) for corroboration.

Results

Stored BFVi data were analyzed for each phase: pre-occlusion (baseline), with the vessel occluded (occlusion), and after reversal of occlusion (re-perfusion). In saphenous veins, BFVi relative to baseline reduced to 5.2±3.7 % during occlusion and returned to 102.9±14.9 % during re-perfusion. Unlike ICG-VA, SurgeON BFM was able to monitor reduced BFVi and characterize re-perfusion robustly during five serial occlusion procedures conducted 2-5 min apart on the same vessel. Across four sheep MCA vessels, BFVi reduced to 18.6±7.7 % and returned to 120.1±27.8 % of baseline during occlusion and re-perfusion phases, respectively.

Conclusions

SurgeON BFM can noninvasively monitor vascular occlusion status and provide intuitive visualization of BF information in real-time to an operating surgeon. This technology may find application in vascular, plastic, and neurovascular surgery.

Fluorescence-guided surgery: National trends in adoption and application in pediatric surgery

BACKGROUND

Fluorescence-guided surgery (FGS) with indocyanine green (ICG) is a rapidly diffusing surgical innovation, but its utilization in pediatrics remains unknown. We present a cross-sectional descriptive analysis of trends from a national database.

METHODS

The Pediatric Health Information System (PHIS) database was queried for patient encounters between January 2016 and July 2021 with an associated ICG administration within 3 days prior to surgery. All procedure codes from each encounter were reviewed by two surgeons to determine the most likely associated FGS procedure and assign an operative category.

RESULTS

1270 encounters were identified from 38 participating hospitals. The mean patient age (SD) was 8.3 (6.4) years, 54.5% were male, 63.8% were white, and 30.1% were Hispanic. The most common categories for ICG use were neurosurgery (21.3%), biliary (18.3%), perfusion (14.8%), urology (12.5%), gastrointestinal (10.8%), ophthalmology (8.8%), and thoracic (5.6%). Utilization over time increased for some categories (thoracic, visceral perfusion, and neurological procedures) or remained stable for other categories. Overall ICG utilization has increased in 2020 (n = 314) compared to 2016 (N = 83). The number of centers utilizing ICG has also increased from 14 hospitals in 2016 to 29 hospitals in 2020 though adoption remains unevenly distributed, with 5 high-utilization hospitals accounting for 56.8% of all ICG FGS cases.

CONCLUSION

ICG is being used across a wide variety of pediatric surgical disciplines. Trends over time show increasingly frequent adoption across the country, with a few high-volume centers driving the innovation. Fluorescence-guided surgery is commercially available and is becoming more commonplace for pediatric surgeons. Dedicated efforts will now be needed to assess outcomes using this promising technology.

LEVEL OF EVIDENCE

Level IV.

STUDY TYPE

Retrospective study.

The current status and future prospects for molecular imaging-guided precision surgery

Molecular imaging technologies are increasingly used to diagnose, monitor, and guide treatment of i.e., cancer. In this review, the current status and future prospects of the use of molecular imaging as an instrument to help realize precision surgery is addressed with focus on the main components that form the conceptual basis of intraoperative molecular imaging. Paramount for successful interventions is the relevance and accessibility of surgical targets. In addition, selection of the correct combination of imaging agents and modalities is critical to visualize both microscopic and bulk disease sites with high affinity and specificity. In this context developments within engineering/imaging physics continue to drive the growth of image-guided surgery. Particularly important herein is enhancement of sensitivity through improved contrast and spatial resolution, features that are critical if sites of cancer involvement are not to be overlooked during surgery. By facilitating the connection between surgical planning and surgical execution, digital surgery technologies such as computer-aided visualization nicely complement these technologies. The complexity of image guidance, combined with the plurality of technologies that are becoming available, also drives the need for evaluation mechanisms that can objectively score the impact that technologies exert on the performance of healthcare professionals and outcome improvement for patients.

The impact of the quantitative assessment procedure for coronary artery bypass graft evaluations using high-resolution near-infrared fluorescence angiography

PURPOSE

Near-infrared angiography (NIR) is used for on-site graft assessment during coronary artery bypass grafting. This study evaluated the results of a quantitative NIR assessment using a new high-resolution NIR device (h-NIR) for graft assessment.

METHODS

Forty-three patients were enrolled in our study. Internal thoracic artery (ITA) grafts anastomosed to the left anterior descending artery and examined intraoperatively using h-NIR were included. The ITA grafts were divided into 2 groups for a comparative analysis: patent grafts (P group; n = 37) and failed grafts (F group; n = 6). The graft flow was evaluated by a "quantitative NIR assessment", and the fluorescence luminance intensity (FLI) was measured. Direct observation of the graft and anastomosis with h-NIR was also performed.

RESULTS

The FLI was higher in the P group than in the F group. The receiver operating characteristic analysis revealed the following cut-off values for FLIs depending on imaging duration: 21.1% at 1 s, 35.5% at 2 s, 58.4% at 3 s, and 83.3% at 4 s. The sensitivity and specificity for detecting graft failure were 83.3% and 69.8-80.6%, respectively. Furthermore, h-NIR was also able to visualize arterial dissection in ITA grafts.

CONCLUSIONS

A quantitative NIR assessment with an h-NIR device can improve the detectability of anastomotic stenosis, and h-NIR successfully detected arterial dissection of grafts.

Intraoperative fluorescence with indocyanine green in congenital cardiac surgery: Potential applications of a novel technology

Background

Achieving successful repair of congenital heart defects requires attention to detail. Careful evaluation of anastomotic site patency, reimplanted coronary arteries, location of epicardial coronaries, and myocardial perfusion may be necessary to ensure safe conduct of the operation and achieve excellent outcomes.

Methods

Intraoperative fluorescence angiography (IOFA) was performed using indocyanine green in patients undergoing the following procedures: coronary artery reimplantation, coronary artery unroofing, evaluation of intraoperative coronary anatomy, reoperation requiring ventriculotomy, coarctation/interrupted aortic arch repair, systemic-to-pulmonary artery shunt, Norwood procedure, thoracic duct localization, and vascular rings.

Results

The technique was feasible in all patients. No mortality or adverse events related to the dye were encountered. Adequate intraoperative imaging was obtained in 15 patients (20 images), which correlated well with postoperative studies. The imaging quality was superior for assessing shunt patency, myocardial perfusion, and anastomotic patency and determining the location of epicardial coronary arteries but was less so for assessing branch pulmonary arteries.

Conclusions

IOFA is a useful and safe technique that can provide a quick on-table assessment of a variety of congenital surgical procedures. This may help answer questions that can minimize postoperative interventions and help ensure a smooth perioperative course and excellent outcomes.

Evolution of photodynamic medicine based on fluorescence image-guided diagnosis using indocyanine green and 5-aminolevulinic acid

New diagnostic techniques based on photodynamic medicine, such as near-infrared fluorescence using indocyanine green (NIR-ICG) and 5-aminolevulinic acid-mediated photodynamic diagnosis (ALA-PDD), are aiding navigation tasks across various fields of surgery. Specifically, NIR-ICG is being used for the intraoperative identification of sentinel lymph nodes or blood vessels in organ resection and for blood flow evaluation in surgery. These ICG-fluorescent imaging techniques could provide an additional and potentially valuable way to identify vascular and lymphatic structures in surrounding tissue. 5-Aminolevulinic acid is a precursor of a photosensitizing substance with affinity for tumors; thus, diagnostic laparoscopy using ALA-PDD in combination should improve the accuracy of detecting peritoneal dissemination in patients with advanced gastric cancer. The ability to overlay fluorescent imaging with conventional color images in real time using ALA-PDD and NIR with ICG would be of immense benefit to surgeons, providing good visualization and detection of target lesions not seen with the naked eye. A multi-center clinical study examining the safety and efficacy of ALA-PDD during laparoscopic examination for patients with advanced gastric cancer is currently underway in the form of doctor-initiated trials, and further verification studies will be conducted. Such imaging capability could have broad potential across cancer and vascular surgery.

The evaluation of the hemodynamics of a gastric tube in esophagectomy using a new noninvasive blood flow evaluation device utilizing near-infrared spectroscopy

OBJECTIVE

We herein evaluated the hemodynamics of a gastric tube in esophagectomy using a new noninvasive blood flow evaluation device utilizing near-infrared spectroscopy.

METHODS

Thirty-two cases of subtotal esophagectomy and gastric tube reconstruction for esophageal cancer were studied. The new device measures the regional tissue saturation of oxygen (rSO₂: 0-99%) and total hemoglobin index (T-HbI: 0-1.0) with a small sensor. We measured these values at the antrum (point A), final branch of the right gastroepiploic artery (point B) and planned anastomotic point (point C) before and after gastric tube formation. The values at the three points were compared, and the gradients at the three points from before to after gastric tube formation were compared.

RESULTS

The mean values of rSO₂ at point A, B, and C before gastric tube formation were 57.2%, 57.8% and 56.0%, and those after formation were 54.6%, 58.0% and 55.8%, respectively. There was no significant difference in the comparison of the rSO₂ gradient before and after formation (p = 0.167). The mean values of T-HbI at point A, B, and C before formation were 0.126, 0.178 and 0.211, and those after formation were 0.167, 0.247 and 0.292, respectively. There was no significant difference in the gradient of the increase before and after formation (p = 0.461).

CONCLUSION

A new device has shown that the gastric tube used in our facility is one that maintains tissue saturation of oxygen and does not cause excessive congestion at anastomosis.

Usefulness of blood flow evaluation by indocyanine green fluorescence system in laparoscopic anterior resection

BACKGROUND

One of the major cause of anastomotic leakage (AL) in anterior resection of the rectum is insufficient blood flow of the remnant colon. The indocyanine green fluorescence system (ICG-FS) can visualize the blood flow of organs intra-operatively. The aim of this study is to investigate the usefulness of ICG-FS for evaluating the blood flow of the remnant colon in laparoscopic anterior resection.

MATERIALS AND METHODS

Rectal cancer patients (n=24) who underwent laparoscopic anterior resection were included in this study. After resection of the rectum, 7.5mg of ICG was administered intravenously, and the blood flow of the oral stump was evaluated by the ICG-FS. The relationship between the fluorescence time (FT) of the oral stump and AL was investigated retrospectively.

RESULT

Two of twenty-four patients (8.3%) suffered AL. The FT of these two cases were over 60 seconds. In the case with the FT was over 80 seconds, we performed additional resection of the late fluorescence portion of the remnant colon and could avoid AL. In patients whose FT was under 60 seconds, no patients suffered AL.

CONCLUSION

ICG-FS may be useful for evaluating the blood flow of the remnant colon to avoid AL in laparoscopic anterior resection. J. Med. Invest. 66 : 65-69, February, 2019.

Real-Time Fluorescence Imaging in Thoracic Surgery

Near-infrared (NIR) fluorescence imaging provides a safe and cost-efficient method for immediate data acquisition and visualization of tissues, with technical advantages including minimal autofluorescence, reduced photon absorption, and low scattering in tissue. In this review, we introduce recent advances in NIR fluorescence imaging systems for thoracic surgery that improve the identification of vital tissues and facilitate the resection of tumorous tissues. When coupled with appropriate NIR fluorophores, NIR fluorescence imaging may transform current intraoperative thoracic surgery methods by enhancing the precision of surgical procedures and augmenting postoperative outcomes through improvements in diagnostic accuracy and reductions in the remission rate.

Influence of residual coronary flow on bypass graft flow for graft assessment using near-infrared fluorescence angiography

PURPOSE

Near-infrared fluorescence angiography (NIR) detects the attenuation of fluorescence luminance intensity (FLI) through coronary artery bypass grafts affected by anastomotic stenosis. This study investigates the influence of residual blood flow of the host coronary artery (Ho) on bypass graft (Gr) FLI using a coronary artery bypass (CABG) model.

METHODS

A mock circuit system was created using artificial vessels and artificial blood was supplied to the Gr and the Ho. We used NIR to examine the changes in FLI through the Gr.

RESULTS

The Gr FLI was significantly attenuated according to the degree of Gr stenosis. The Gr FLI did not differ significantly among all degrees of Ho stenosis. High FLI grafts included grafts with degrees of Gr stenosis ≤ 75%, regardless of the severity of Ho stenosis. Moderate and low FLI grafts had 90 or 99% Gr stenosis, regardless of the severity of Ho stenosis. Gr FLI with 99% Gr stenosis was higher in 99% Ho stenosis than in ≤ 90% Ho stenosis.

CONCLUSIONS

A high Gr FLI indicated the absence of ≥ 90% stenosis in the anastomosis and a low Gr FLI indicated severe stenosis in the anastomosis despite Ho stenosis. High Ho stenosis may prevent the attenuation of Gr FLI in severely stenosed grafts.

Usefulness of the HyperEye Medical System in Obstructive Colitis Proximal to Colon Carcinoma

Obstructive colitis (OC) is a nonspecific inflammatory condition that occurs at the proximal side of a completely or partially stenotic lesion typically caused by colorectal cancer. Impaired blood flow caused by these stenotic changes in the colon or rectum results in this condition. During surgery for sigmoid colon carcinoma with OC, complete surgical removal of the OC lesions is required. However, it is difficult to anticipate the range of OC before surgery. Diagnosing the potential ischemia during surgery would decrease the need for re-operation. This is the first report of HyperEye Medical System (HEMS) angiography for surgery of colon cancer with OC. We report a case of sigmoid colon carcinoma in which HEMS angiography was used and found to be useful for real-time detection of the OC lesion.

Evaluation of graft anastomosis using time-intensity curves and quantitative near-infrared fluorescence angiography during peripheral arterial bypass grafting

Near-infrared fluorescence angiography (NIR) visualizes blood perfusion using the fluorescence property of indocyanine green (ICG). This study aimed to retrospectively determine the usefulness of a quantitative analysis using NIR to predict the patency of peripheral arterial bypass grafts by measuring their fluorescence luminance intensities (FLIs).Thirteen grafts in 11 patients who underwent peripheral arterial bypass grafting were divided into a patent graft group (n = 7) and a failed graft group (n = 6). The changes in the FLIs of ICG opacification through the graft and distal host artery were retrospectively analyzed using stored NIR data. The time-intensity curves (TICs) of ICG opacification through the graft (Q_graft) and distal host artery (Q_distal) were measured. Two parameters, Δ(Q_graft - Q_distal) and integral(Q_graft - Q_distal), were also analyzed.Although not significant, decreases in Q_graft were observed in the failed graft groups. The Q_distal of the failed graft group was significantly attenuated as compared with that of the patent graft group. Δ(Q_graft - Q_distal) increased only in the failed graft group, which indicates widening of the gap in FLI. Integral(Q_graft - Q_distal) was higher in the failed graft group, as it reflects the accumulation of ICG opacification.The TICs were influenced by anastomotic stenosis in the distal site of the host arteries. Our results indicate that the comparison of Δ(Q_graft - Q_distal) and integral (Q_graft - Q_distal) quantitatively analyzed using NIR can potentially predict anastomotic stenosis.

Clinical application of photodynamic medicine technology using light-emitting fluorescence imaging based on a specialized luminous source

The natural amino acid 5-aminolevulinic acid (ALA) is a protoporphyrin IX (PpIX) precursor and a new-generation photosensitive substance that accumulates specifically in cancer cells. When indocyanine green (ICG) is irradiated with near-infrared (NIR) light, it shifts to a higher energy state and emits infrared light with a longer wavelength than the irradiated NIR light. Photodynamic diagnosis (PDD) using ALA and ICG-based NIR fluorescence imaging has emerged as a new diagnostic technique. Specifically, in laparoscopic examinations for serosa-invading advanced gastric cancer, peritoneal metastases could be detected by ALA-PDD, but not by conventional visible-light imaging. The HyperEye Medical System (HEMS) can visualize ICG fluorescence as color images simultaneously projected with visible light in real time. This ICG fluorescence method is widely applicable, including for intraoperative identification of sentinel lymph nodes, visualization of blood vessels in organ resection, and blood flow evaluation during surgery. Fluorescence navigation by ALA-PDD and NIR using ICG imaging provides good visualization and detection of the target lesions that is not possible with the naked eye. We propose that this technique should be used in fundamental research on the relationship among cellular dynamics, metabolic enzymes, and tumor tissues, and to evaluate clinical efficacy and safety in multicenter cooperative clinical trials.

Fluorescence-Guided Surgery

Surgical resection of cancer remains an important treatment modality. Despite advances in preoperative imaging, surgery itself is primarily guided by the surgeon’s ability to locate pathology with conventional white light imaging. Fluorescence-guided surgery (FGS) can be used to define tumor location and margins during the procedure. Intraoperative visualization of tumors may not only allow more complete resections but also improve safety by avoiding unnecessary damage to normal tissue which can also reduce operative time and decrease the need for second-look surgeries. A number of new FGS imaging probes have recently been developed, complementing a small but useful number of existing probes. In this review, we describe current and new fluorescent probes that may assist FGS.

Severe hemodynamic instability after indocyanine green injection during off-pump coronary artery bypass grafting: A case report

RATIONALE

The increasingly intraoperative use of indocyanine green (ICG) means that it is necessary to be aware of both its advantages and potential adverse effects.

PATIENT CONCERNS

A 76-year-old woman developed symptoms of sudden severe hemodynamic instability while undergoing coronary artery bypass grafting with ICG injection to detect the patency of the graft. The main clinical manifestations were a sudden drop in blood pressure and increased heart rate.

DIAGNOSES

Severe side effects or allergic reaction of ICG.

INTERVENTIONS

Cardiopulmonary bypass (CPB) was established, and an intra-aortic balloon pump was implanted in the left femoral artery after intravenous epinephrine and manual cardiac compression failed.

OUTCOMES

The patient was extubated and transferred to the general ward on the third postoperative day.

LESSONS

Invasive blood pressure monitoring should be carried out in patients undergoing intraoperative ICG administration. Anesthetists should pay close attention to the patient's hemodynamic fluctuations, and effective emergency measures should be implemented immediately if severe hemodynamic instability occurs.

Successful treatment of non-occlusive mesenteric ischemia with indocyanine green fluorescence and open-abdomen management

Non-occlusive mesenteric ischemia (NOMI), which can lead to multifocal and segmental intestinal necrosis without demonstrable occlusion in the main mesenteric artery, is associated with extremely high mortality. Because these intestinal ischemic changes can progress, it is difficult to make a definitive determination intraoperatively as to whether resection of damaged intestine is required. A 62-year-old man who underwent esophagectomy for advanced cervicothoracic esophageal cancer complained of severe abdominal pain on postoperative day 4. Enhanced computed tomography revealed pneumatosis intestinalis in the wall of the small bowel. Emergency laparotomy revealed ischemia in segments of the small intestine suspicious for NOMI. Intraoperative evaluation of the mesenteric and bowel circulation was performed under indocyanine green (ICG) fluorescence. Although the ischemic bowel segments were visible, open-abdomen management was undertaken so that mesenteric and bowel circulation could be reexamined 24 h later. During the second-look operation, the small intestine was able to be preserved because intestinal perfusion was confirmed on revisualization under ICG fluorescence. The present case demonstrated that open-abdomen management and repeat visualization under ICG fluorescence are effective in preserving damaged intestine during surgery for NOMI.

In vivo visualization and ex vivo quantification of experimental myocardial infarction by indocyanine green fluorescence imaging

The fluorophore indocyanine green accumulates in areas of ischemia-reperfusion injury due to an increase in vascular permeability and extravasation of the dye. The aim of the study was to validate an indocyanine green-based technique of in vivo visualization of myocardial infarction. A further aim was to quantify infarct size ex vivo and compare this technique with the standard triphenyltetrazolium chloride staining. Wistar rats were subjected to regional myocardial ischemia (30 minutes) followed by reperfusion (n = 7). Indocyanine green (0.25 mg/mL in 1 mL of normal saline) was infused intravenously for 10 minutes starting from the 25th minute of ischemia. Video registration in the near-infrared fluorescence was performed. Epicardial fluorescence of indocyanine green corresponded to the injured area after 30 minutes of reperfusion. Infarct size was similar when determined ex vivo using traditional triphenyltetrazolium chloride assay and indocyanine green fluorescent labeling. Intravital visualization of irreversible injury can be done directly by fluorescence on the surface of the heart. This technique may also be an alternative for ex vivo measurements of infarct size.

Influence of vessel stenosis on indocyanine green fluorescence intensity assessed by near-infrared fluorescence angiography

PURPOSE

Although useful for visualizing blood flow during revascularization surgery, the permeability of near-infrared fluorescence (NIR) angiography using indocyanine green (ICG) does not allow for vessel stenosis visualization. We hypothesized that changes in ICG fluorescence intensity reflect vessel stenosis, and evaluated the influence of stenosis on blood flow by ex vivo experimentation.

METHODS

The vessel stenosis model comprised a silicon tube, a graft occluder, and artificial blood. During near-infrared angiography, the fluorescense intensity was calculated during pre- and post-stenosis of an artificial circuit, using a NIR angiography. We measured the maximum fluorescence intensity and the time to maximum fluorescence intensity.

RESULTS

Severe stenosis (≥75%) attenuated the increase in ICG fluorescence intensity in the tube significantly, pre- and post-stenosis. The time to maximum fluorescence intensity did not differ between sites pre- and post-stenosis, irrespective of stenosis severity.

CONCLUSION

Stenosis affected the ICG fluorescence intensity through the vessel. Thus, quantitative analysis using NIR angiography may detect severe vessel stenosis (≥75%), and the extinction curve of indocyanine fluorescence intensity may support the evaluation of blood flow. The absence of differences in the time to maximum fluorescence intensity for degrees of stenosis might suggest a limitation of previous conventional qualitative assessments.

Factors Affecting Blood Flow at the Tip of the Reconstructed Gastric Tube During Esophagectomy: A Study Using Indocyanine Green Fluorescence Angiography

The objective of this study was to clarify the factors affecting blood flow at the tip of the gastric tube during esophagectomy using indocyanine green (ICG) fluorescence angiography. The time until enhancement of the gastric tube tip determined using ICG fluorescence imaging is a useful indicator of blood flow, and has been shown not to differ significantly according to the connection status of the right or left gastroepiploic artery. Using ICG fluorescence imaging, the time until enhancement of the gastric tube tip was measured in 50 patients undergoing esophagectomy. Blood flow at the gastric tube tip was compared between 2 groups of patients: those in whom a connecting vessel from the left gastro-epiploic artery to the short gastric artery (l-s GA) was present and those in whom it was absent. The factors affecting blood flow to the gastric tube tip were also investigated using univariate and multivariate logistic regression analysis. The median time taken for the gastric tube tip to show enhancement with ICG was significantly shorter in the group with an l-s GA connection (P = 0.02). Multivariate analysis showed that the absence of an l-s GA connection (P = 0.04) and presence of arteriosclerosis-related disease (P = 0.02) were significant independent factors that delayed blood flow to the gastric tube. It is essential to preserve the whole vessel arcade of the greater curvature to achieve good perfusion of the gastric tube with blood. The presence of arteriosclerosis-related disease is a major factor affecting the safety of anastomosis during gastric tube reconstruction.

Quantitative assessment technique of HyperEye medical system angiography for coronary artery bypass grafting

PURPOSE

The HyperEye Medical System (HEMS) uses indocyanine green (ICG) to visualize blood vessels in coronary artery bypass grafting (CABG). We performed quantitative HEMS assessment to detect grafts at risk of occlusion.

METHODS

We assessed the HEMS angiograms of 177 grafts from 69 patients who underwent CABG and compared the results with those of fluoroscopic coronary angiography, by measuring the increasing rate of ICG intensity, average acceleration value, and time to peak luminance intensity.

RESULTS

Grafts in the patent and failed groups showed significant differences in their increasing rate of intensity and average acceleration value. The average accelerations value of ICG intensity of internal thoracic artery (ITA) and saphenous vein (SV) grafts were 112.3 and 144.9 intensity/s² in the patent group, and 71.0 and 91.8 intensity/s² in the failed group. The time to peak luminance intensity was 1.7 and 1.4 s in the patent group and 2.3 and 1.9 s in the failed group; these values were not significantly different.

CONCLUSION

Significant reductions in the ICG intensity rate and average acceleration value can occur in failed grafts. Therefore, quantifiable changes in ICG intensity may help detect minute changes in blood flow.

Recent advances in near-infrared fluorescence-guided imaging surgery using indocyanine green

Near-infrared (NIR) fluorescence imaging has better tissue penetration, allowing for the effective rejection of excitation light and detection deep inside organs. Indocyanine green (ICG) generates NIR fluorescence after illumination by an NIR ray, enabling real-time intraoperative visualization of superficial lymphatic channels and vessels transcutaneously. The HyperEye Medical System (HEMS) can simultaneously detect NIR rays under room light to provide color imaging, which enables visualization under bright light. Thus, NIR fluorescence imaging using ICG can provide for excellent diagnostic accuracy in detecting sentinel lymph nodes in cancer and microvascular circulation in various ischemic diseases, to assist us with intraoperative decision making. Including HEMS in this system could further improve the sentinel lymph node mapping and intraoperative identification of blood supply in reconstructive organs and ischemic diseases, making it more attractive than conventional imaging. Moreover, the development of new laparoscopic imaging systems equipped with NIR will allow fluorescence-guided surgery in a minimally invasive setting. Future directions, including the conjugation of NIR fluorophores to target specific cancer markers might be realistic technology with diagnostic and therapeutic benefits.

Creation of gastric conduit free-graft with intraoperative perfusion imaging during pancreaticoduodenectomy in a patient post esophagectomy

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Pancreaticoduodenectomy in a patient post esophagectomy.

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Microvascular anastomosis of the gastroepiploic pedicle was performed to the middle colic vessels.

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Intraoperative perfusion imaging during pancreaticoduodenectomy.

As surgery becomes more successful for complicated malignancies, patients survive longer and can unfortunately develop subsequent malignancies. Surgical resection in these settings can be treacherous and manipulations of the patient’s anatomy need to be closely considered before embarking on major operations. We report a case of a patient who survived esophageal resection for locally advanced esophageal cancer only to develop a new pancreatic head malignancy. Careful upfront planning allowed for a successful resection with an uncomplicated recovery.

She underwent open pancreaticoduodenectomy, and to maintain perfusion to the gastric conduit a microvascular anastomosis of the gastroepiploic pedicle was performed to the middle colic vessels. Intraoperative fluorescent imaging was used to evaluate the anastomosis as well as gastric and duodenal perfusion during the case.

Intraoperative graft assessment during coronary artery bypass surgery

Coronary artery bypass grafting (CABG) is an established revascularization method for treating multivessel coronary artery disease. The goal of CABG is to achieve complete revascularization with a durable, patent graft without reintervention. However, early graft failure, including that associated with technical errors, has been reported. This makes intraoperative verification of graft patency one of the most important ways in which surgeons can reduce the rate of early graft failure. Conventional angiography is considered the gold standard for graft assessment. However, because it is invasive and inconvenient, several alternatives to intraoperative graft assessment have become available that help reduce early graft failure by allowing revision of the anastomosis intraoperatively. The aim of this article is to review the advantages and disadvantages of several intraoperative graft assessment methods for CABG.

Hemodynamics of the reconstructed gastric tube during esophagectomy: assessment of outcomes with indocyanine green fluorescence

BACKGROUND

Construction of a gastric tube that is well perfused with blood during esophagectomy is the most important factor in avoiding anastomotic leakage. We clarified the hemodynamics of the reconstructed gastric tube with indocyanine green (ICG) fluorescence.

METHODS

In 20 patients undergoing gastric tube reconstruction during esophagectomy, we evaluated blood flow in the gastric tube with ICG fluorescence imaging. We divided the patients into two groups according to the quality of blood flow to the gastric tube-"good" (n = 9) and "sparse or absent" (n = 11)-based on visual assessment of the anastomosis of the right and left gastroepiploic vessels. We measured the time from initial enhancement of the root of the right gastroepiploic artery until enhancement of the most cranial branch of the left gastroepiploic artery and tip of the gastric tube.

RESULTS

The gastric tube was divisible into three zones according to the dominant arteries present in the greater curvature under ICG fluorescence. The left gastroepiploic artery was enhanced in a direction opposite that of physiological blood flow in all cases. The median period from initial enhancement of the root of the right gastroepiploic artery to the most cranial branch of the left gastroepiploic artery until perfusion up to the tip of the gastric tube did not differ significantly between the "good" and the "sparse or absent" groups (P = 0.24, 0.68) CONCLUSIONS: It is essential to preserve the whole vessel arcade of the greater curvature to achieve good blood perfusion in the gastric tube. The ICG fluorescence method has potential usefulness for evaluation of blood flow in the gastric tube.

Usefulness of indocyanine green angiography for evaluation of blood supply in a reconstructed gastric tube during esophagectomy

We report a case of necrosis of a reconstructed gastric tube in a 77-year-old male patient who had undergone esophagectomy. At the time of admission, the patient had active gastric ulcers, but these were resolved by treatment with a proton pump inhibitor. Subtotal esophagectomy with gastric tube reconstruction was performed. Visually, the reconstructed gastric tube appeared to be well perfused with blood. Using indocyanine green (ICG) fluorescence imaging the gastroepiploic vessels were well enhanced and no enhancement was visable 3 to 4 cm from the tip of the gastric tube. Four days after esophagectomy, gastric tube necrosis was confirmed, necessitating a second operation. The necrosis of the gastric tube matched the area that had been shown to lack blood perfusion by ICG angiography imaging. It seems that ICG angiography is useful for the evaluation of perfusion in a reconstructed gastric tube.

Intraoperative imaging-guided cancer surgery: from current fluorescence molecular imaging methods to future multi-modality imaging technology

Cancer is a major threat to human health. Diagnosis and treatment using precision medicine is expected to be an effective method for preventing the initiation and progression of cancer. Although anatomical and functional imaging techniques such as radiography, computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET) have played an important role for accurate preoperative diagnostics, for the most part these techniques cannot be applied intraoperatively. Optical molecular imaging is a promising technique that provides a high degree of sensitivity and specificity in tumor margin detection. Furthermore, existing clinical applications have proven that optical molecular imaging is a powerful intraoperative tool for guiding surgeons performing precision procedures, thus enabling radical resection and improved survival rates. However, detection depth limitation exists in optical molecular imaging methods and further breakthroughs from optical to multi-modality intraoperative imaging methods are needed to develop more extensive and comprehensive intraoperative applications. Here, we review the current intraoperative optical molecular imaging technologies, focusing on contrast agents and surgical navigation systems, and then discuss the future prospects of multi-modality imaging technology for intraoperative imaging-guided cancer surgery.

Near-infrared II fluorescence for imaging hindlimb vessel regeneration with dynamic tissue perfusion measurement

BACKGROUND

Real-time vascular imaging that provides both anatomic and hemodynamic information could greatly facilitate the diagnosis of vascular diseases and provide accurate assessment of therapeutic effects. Here, we have developed a novel fluorescence-based all-optical method, named near-infrared II (NIR-II) fluorescence imaging, to image murine hindlimb vasculature and blood flow in an experimental model of peripheral arterial disease, by exploiting fluorescence in the NIR-II region (1000-1400 nm) of photon wavelengths.

METHODS AND RESULTS

Because of the reduced photon scattering of NIR-II fluorescence compared with traditional NIR fluorescence imaging and thus much deeper penetration depth into the body, we demonstrated that the mouse hindlimb vasculature could be imaged with higher spatial resolution than in vivo microscopic computed tomography. Furthermore, imaging during 26 days revealed a significant increase in hindlimb microvascular density in response to experimentally induced ischemia within the first 8 days of the surgery (P<0.005), which was confirmed by histological analysis of microvascular density. Moreover, the tissue perfusion in the ischemic hindlimb could be quantitatively measured by the dynamic NIR-II method, revealing the temporal kinetics of blood flow recovery that resembled microbead-based blood flowmetry and laser Doppler blood spectroscopy.

CONCLUSIONS

The penetration depth of millimeters, high spatial resolution, and fast acquisition rate of NIR-II imaging make it a useful imaging tool for murine models of vascular disease.

Successful treatment of non-occlusive mesenteric ischemia (NOMI) using the HyperEye Medical System™ for intraoperative visualization of the mesenteric and bowel circulation: report of a case

Non-occlusive mesenteric ischemia (NOMI), leading to intestinal gangrene without a demonstrable occlusion in the mesenteric artery, is a rare condition with extremely high mortality. We report a case of NOMI diagnosed preoperatively by computed tomography and treated successfully with surgery, assisted by indocyanine green (ICG) fluorescence in the HyperEye Medical System (HEMS), a new device that can simultaneously detect color and near-infrared rays under room light. This allowed for precise intraoperative evaluation of the mesenteric and bowel circulation. Although the necrotic bowel wall of the distal ileum and the segmental ischemia of the jejunum were visible, the jejunum was finally preserved because perfusion of ICG fluorescence was confirmed. The patient, an 84-year-old man, had an uneventful postoperative course and is alive without critical illness 8 months after surgery. We report this case to demonstrate the potential effectiveness of HEMS during surgery for NOMI.

Essential parameters to consider for the characterization of optical imaging probes

The Molecular Imaging and Contrast Agents Database (MICAD) was launched in 2005 to promote the development and application of imaging and contrast agents (probes) to advance the field of molecular imaging. As of March 2012, there are approximately 1170 agents available in MICAD. Based on the modality used for imaging, the largest category of probes described in MICAD are those used for PET (41.6%), followed by agents used for single-photon emission computed tomography (30.3%), optical imaging (12.0%), MRI (9.3%), multimodality imaging (3.4%), ultrasound (2.4%) and x-ray/computed tomography (1.0%). This article is intended to be a guideline for new investigators and students who wish to characterize an optical imaging probe that will be used to perform in vivo molecular imaging studies. It is necessary, however, to ensure that these agents meet certain quality control parameters before they are used in various in vitro and in vivo applications.

Nitrite anion stimulates ischemic arteriogenesis involving NO metabolism

Nitric oxide (NO) is a potential regulator of ischemic vascular remodeling, and as such therapies augmenting its bioavailability may be useful for the treatment of ischemic tissue diseases. Here we examine the effect of administering the NO prodrug sodium nitrite on arteriogenesis activity during established tissue ischemia. Chronic hindlimb ischemia was induced by permanent unilateral femoral artery and vein ligation. Five days postligation; animals were randomized to control PBS or sodium nitrite (165 μg/kg) therapy twice daily. In situ vascular remodeling was measured longitudinally using SPY angiography and Microfil vascular casting. Delayed sodium nitrite therapy rapidly increased ischemic limb arterial vessel diameter and branching in a NO-dependent manner. SPY imaging angiography over time showed that nitrite therapy enhanced ischemic gracillis collateral vessel formation from the profunda femoris to the saphenous artery. Immunofluorescent staining of smooth muscle cell actin also confirmed that sodium nitrite therapy increased arteriogenesis in a NO-dependent manner. The NO prodrug sodium nitrite significantly increases arteriogenesis and reperfusion of established severe chronic tissue ischemia.

Near-Infrared Fluorescent Nanoprobes for in Vivo Optical Imaging

Near-infrared (NIR) fluorescent probes offer advantages of high photon penetration, reduced light scattering and minimal autofluorescence from living tissues, rendering them valuable for noninvasive mapping of molecular events, assessment of therapeutic efficacy, and monitoring of disease progression in animal models. This review provides an overview of the recent development of the design and optical property of the different classes of NIR fluorescent nanoprobes associated with in vivo imaging applications.