Laparoscopic Fluorescent Visualization of the Ureter With Intravenous IRDye800CW

Enhancing visualization and guidance in general surgery: a comprehensive and narrative review of the current cutting-edge technologies and future perspectives

BACKGROUND

In the last decade, there has been a great effort in developing new technologies to enhance surgical visualization and guidance. This comprehensive and narrative review aimed to provide a wide and extensive overview of the current state of the art on this topic and their near-future perspectives linked to the development of artificial intelligence (AI), by focusing on the most recent and relevant literature.

METHODS

A comprehensive and narrative review of the literature was performed by searching specific terms on PubMed/MEDLINE, Scopus, and Embase databases, assessing the current state of the art on this topic.

RESULTS

Fluorescence-guided surgery, contrast-enhanced ultrasound (CEUS), ultra-high frequency ultrasound (UHFUS), photoacoustic imaging (PAI), and augmented reality (AR) are boosting the field of image-guided techniques as the rapid development of AI in surgery is promising a more automated decision-making and surgical movements in the operating room.

CONCLUSION

Fluorescence-guided surgery, CEUS, UHFUS, PAI, and AR are becoming crucial to give surgeons a new level of information during the intervention, with the right timing and sequence, and represent the future of surgery. As many more controlled studies are needed to validate the employment of these technologies, the next generation of surgeons must become more familiar with the basics of AI to better incorporate new tools into the daily surgical practice of the future.

Evaluation of the Utilization of Near-Infrared Fluorescent Contrast Agent ASP5354 for In Vivo Ureteral Identification in Renal Diseases Using Rat Models of Gentamicin-Induced Acute Kidney Injury

ASP5354 was recently developed as a near-infrared fluorescence (NIRF) contrast agent for intraoperative ureteral identification, and its use has been evaluated in healthy animals. However, the utilization of ASP5354 for ureteral identification has not been evaluated in animals with renal injury. In this study, we assessed the application of ASP5354 for ureteral imaging using rat models of gentamicin-induced mild, moderate, and severe acute kidney injury (AKI), using a clinically available NIRF detection system. NIRF was detected in the abdominal cavity and ureters after laparotomy, and the efficiency of ASP5354 was evaluated based on the NIRF signal intensity over 60 min. After the intravenous injection of ASP5354 into rats with mild or moderate AKI, the ureters were clearly imaged at a high ratio of NIRF intensity in the ureter to that in the tissues around the ureter. Six days after intravenous injection, the use of ASP5354 in rats with moderate AKI did not affect the biochemical kidney functions or histopathological conditions of the kidney tissues, as compared to those with no injection of ASP5354. In rats with severe AKI, ureteral imaging was not effective due to the relatively strong NIRF expression in the tissues around the ureters. These data indicate that ASP5354 holds potential as a contrast agent for intraoperative ureteral identification in patients with limited renal injury.

Detection of Tumour-Targeted IRDye800CW Tracer with Commercially Available Laparoscopic Surgical Systems

(1) Introduction: Near-infrared fluorescence (NIRF) combined with tumour-targeted tracers, such as bevacizumab-800CW, could aid surgical decision-making. This study explored the use of IRDye800CW, conjugated to bevacizumab, with four commercially available NIRF laparoscopes optimised for indocyanine green (ICG). (2) Methods: A (lymph node) phantom was made from a calibration device for NIRF and tissue-mimicking material. Serial dilutions of bevacizumab-800CW were made and ICG functioned as a reference. System settings, working distance, and thickness of tissue-mimicking material were varied to assess visibility of the fluorescence signal and tissue penetration. Tests were performed with four laparoscopes: VISERA ELITE II, Olympus; IMAGE1 S™ 4U Rubina, KARL STORZ; ENDOCAM Logic 4K platform, Richard Wolf; da Vinci Xi, Intuitive Surgical. (3) Results: The lowest visible bevacizumab-800CW concentration ranged between 13-850 nM (8-512 times diluted stock solution) for all laparoscopes, but the tracer was not visible through 0.8 cm of tissue in all systems. In contrast, ICG was still visible at a concentration of 0.4 nM (16,384 times diluted) and through 1.6-2.4 cm of tissue. Visibility and tissue penetration generally improved with a reduced working distance and manually adjusted system settings. (4) Conclusion: Depending on the application, bevacizumab-800CW might be sufficiently visible with current laparoscopes, but optimisation would widen applicability of tumour-targeted IRDye800CW tracers.

Preclinical Development and Validation of ASP5354: A Near-Infrared Fluorescent Agent for Intraoperative Ureter Visualization

PURPOSE

Iatrogenic ureteral injury (IUI) can complicate minimally invasive and open abdominopelvic surgery. The incidence of IUI is low and dependent on the type of surgery (< 10 %), but it is associated with high morbidity. Therefore, intraoperative visualization of the ureter is critical to reduce the incidence of IUI, and some methodologies for ureter visualization have been developed. Amongst these, near-infrared fluorescence (NIRF) visualization is thought to bring an advantage with real-time retroperitoneal visualization through the retroperitoneum. We investigated an indocyanine green (ICG) derivative, ASP5354, which emits NIRF at 820 nm when exposed to near-infrared light at a wavelength of 780 nm, in a rodent and porcine model.

PROCEDURES

Wistar rats and Göttingen minipigs under anesthesia were laparotomized and then administered ASP5354 chloride intravenously at dose of 0.03 and 0.3 mg/kg for rats and 0.001 and 0.01 mg/kg for minipigs, respectively. Videos of the abdominal cavity in minipigs were taken using a near-infrared fluorescent camera (pde-neo) and assessed visually by three independent clinicians. Toxicological evaluation was demonstrated with cynomolgus monkeys.

RESULTS

The proportion of animals whose ureters were visible up to 3 h after administration of ASP5354 chloride were 33 % at 0.001 mg/kg and 100 % at 0.01 mg/kg, respectively. In a toxicological study in cynomolgus monkeys, ASP5354 chloride demonstrated no significant toxicity, suggesting that 0.01 mg/kg provides an optimal dose when used clinically and could allow for ureter visualization during routine surgical procedures.

CONCLUSIONS

The dose of 0.01 mg/kg provided an optimal dose for ureter visualization up to 3 h after administration. ASP5354 shows promise for ureter visualization during abdominopelvic surgery, which may potentially lower the risk of IUI.

Quantifying the Impact of Signal-to-background Ratios on Surgical Discrimination of Fluorescent Lesions

PURPOSE

Surgical fluorescence guidance has gained popularity in various settings, e.g., minimally invasive robot-assisted laparoscopic surgery. In pursuit of novel receptor-targeted tracers, the field of fluorescence-guided surgery is currently moving toward increasingly lower signal intensities. This highlights the importance of understanding the impact of low fluorescence intensities on clinical decision making. This study uses kinematics to investigate the impact of signal-to-background ratios (SBR) on surgical performance.

METHODS

Using a custom grid exercise containing hidden fluorescent targets, a da Vinci Xi robot with Firefly fluorescence endoscope and ProGrasp and Maryland forceps instruments, we studied how the participants' (N = 16) actions were influenced by the fluorescent SBR. To monitor the surgeon's actions, the surgical instrument tip was tracked using a custom video-based tracking framework. The digitized instrument tracks were then subjected to multi-parametric kinematic analysis, allowing for the isolation of various metrics (e.g., velocity, jerkiness, tortuosity). These were incorporated in scores for dexterity (Dx), decision making (DM), overall performance (PS) and proficiency. All were related to the SBR values.

RESULTS

Multi-parametric analysis showed that task completion time, time spent in fluorescence-imaging mode and total pathlength are metrics that are directly related to the SBR. Below SBR 1.5, these values substantially increased, and handling errors became more frequent. The difference in Dx and DM between the targets that gave SBR < 1.50 and SBR > 1.50, indicates that the latter group generally yields a 2.5-fold higher Dx value and a threefold higher DM value. As these values provide the basis for the PS score, proficiency could only be achieved at SBR > 1.55.

CONCLUSION

By tracking the surgical instruments we were able to, for the first time, quantitatively and objectively assess how the instrument positioning is impacted by fluorescent SBR. Our findings suggest that in ideal situations a minimum SBR of 1.5 is required to discriminate fluorescent lesions, a substantially lower value than the SBR 2 often reported in literature.

In Vivo Optical Imaging of Bladder Cancer Tissues in an MB49 Bladder Cancer Orthotopic Mouse Model Using the Intravesical or Intravenous Administration of Near-Infrared Fluorescence Probe

Bladder cancer was the twelfth most common cancer worldwide in 2020. Although bladder cancer has been diagnosed using macroscopic techniques, such as white-light cystoscopy and fluorescence blue-light cystoscopy, there is a need to explore more effective noninvasive optical imaging techniques for accurate bladder cancer diagnosis. This study demonstrates the high effectiveness of the near-infrared fluorescence (NIRF) probe ASP5354, which has been developed for ureteral identification during in vivo diagnosis of bladder cancer in an MB49 bladder cancer orthotopic mouse model. After the intravesical injection of 2.4 μM ASP5354 followed by bladder rinsing with saline at 5 min post injection or intravenous administration of ASP5354 at 240 nmol/kg mouse body weight, followed by a waiting period of 5-24 h in mice, ASP5354 was absorbed specifically by cancerous tissue and not by normal tissues in the bladder. NIRF of ASP5354 in cancer tissues was detected using the NIRF imaging camera system. The NIRF clearly showed a boundary between cancerous and normal tissues. Therefore, ASP5354 provides noninvasive and specific optical in vivo imaging of MB49 bladder cancer using intravesical or intravenous injection of ASP5354. ASP5354 may allow for new diagnostic applications for bladder cancer in humans.

Urologic Complication after Laparoscopic Hysterectomy in Gynecology Oncology: A Single-Center Analysis and Narrative Review of the Literature

Background and Objectives: Minimally invasive surgery (MIS) has recently increased its application in the treatment of gynecological malignancies. Despite technological and surgical advances, urologic complications (UC) are still the main concern in gynecology surgery. Current literature reports a wide range of urinary tract injuries, and consistent scientific evidence is still lacking or dated. This study aims to report a large single-center experience of urinary complications during laparoscopic hysterectomy for gynecologic oncologic disease. Materials and Methods: All patients who underwent laparoscopic hysterectomy for gynecologic malignancy at the Department of Medicine and Surgery of the University Hospital of Parma from 2017 to 2021 were retrospectively included. Women with endometrial cancer, cervical cancer, ovarian cancer, uterine sarcoma, or borderline ovarian tumors were included. Patients undergoing robotic surgery with incomplete anatomopathological data or patients lost during follow-up were excluded from the analysis. Intraoperative and postoperative UC were analyzed and ranked according to the Clavien-Dindo classification. Results: Two hundred-sixty patients were included in the study: 180 endometrial cancer, 18 cervical cancer, nine ovarian cancer, two uterine sarcomas, and 60 borderline ovarian tumors. Nine (3.5%) UCs were reported (five intraoperative and four postoperative complications). No anamnestic variables showed a statistical correlation with the surgical complication in the univariable analyses. C1 radical hysterectomy, a higher FIGO stage, and postoperative adjuvant treatment (p-value = 0.001, p-value = 0.046, and p-value = 0.046, respectively) were independent risk factors associated with the occurrence of UC. Conclusions: The urological complication rates in patients with oncological disease are relatively rare events in the expert hands of dedicated surgeons. Radical hysterectomy, FIGO stage, and adjuvant treatment are independent factors associated with urinary complications.

Computer-Assisted Differentiation between Colon-Mesocolon and Retroperitoneum Using Hyperspectral Imaging (HSI) Technology

Complete mesocolic excision (CME), which involves the adequate resection of the tumor-bearing colonic segment with “en bloc” removal of its mesocolon along embryological fascial planes is associated with superior oncological outcomes. However, CME presents a higher complication rate compared to non-CME resections due to a higher risk of vascular injury. Hyperspectral imaging (HSI) is a contrast-free optical imaging technology, which facilitates the quantitative imaging of physiological tissue parameters and the visualization of anatomical structures. This study evaluates the accuracy of HSI combined with deep learning (DL) to differentiate the colon and its mesenteric tissue from retroperitoneal tissue. In an animal study including 20 pig models, intraoperative hyperspectral images of the sigmoid colon, sigmoid mesentery, and retroperitoneum were recorded. A convolutional neural network (CNN) was trained to distinguish the two tissue classes using HSI data, validated with a leave-one-out cross-validation process. The overall recognition sensitivity of the tissues to be preserved (retroperitoneum) and the tissues to be resected (colon and mesentery) was 79.0 ± 21.0% and 86.0 ± 16.0%, respectively. Automatic classification based on HSI and CNNs is a promising tool to automatically, non-invasively, and objectively differentiate the colon and its mesentery from retroperitoneal tissue.

Photoacoustic-Guided Laparoscopic and Open Hysterectomy Procedures Demonstrated With Human Cadavers

Hysterectomy (i.e., surgical removal of the uterus) requires severing the main blood supply to the uterus (i.e., the uterine arteries) while preserving the nearby, often overlapping, ureters. In this paper, we investigate dual-wavelength and audiovisual photoacoustic imaging-based approaches to visualize and differentiate the ureter from the uterine artery and to provide the real-time information needed to avoid accidental ureteral injuries during hysterectomies. Dual-wavelength 690/750 nm photoacoustic imaging was implemented during laparoscopic and open hysterectomies performed on human cadavers, with a custom display approach designed to visualize the ureter and uterine artery. The proximity of the surgical tool to the ureter was calculated and conveyed by tracking the surgical tool in photoacoustic images and mapping distance to auditory signals. The dual-wavelength display showed up to 10 dB contrast differences between the ureter and uterine artery at three separation distances (i.e., 4 mm, 5 mm, and 6 mm) during the open hysterectomy. During the laparoscopic hysterectomy, the ureter and uterine artery were visualized in the dual-wavelength image with up to 24 dB contrast differences. Distances between the ureter and the surgical tool ranged from 2.47 to 7.31 mm. These results are promising for the introduction of dual-wavelength photoacoustic imaging to differentiate the ureter from the uterine artery, estimate the position of the ureter relative to a surgical tool tip, map photoacoustic-based distance measurements to auditory signals, and ultimately guide hysterectomy procedures to reduce the risk of accidental ureteral injuries.

Role of near-infrared fluorescence in colorectal surgery

Near-infrared fluorescence (NIRF) is a technique of augmented reality that, when applied in the operating theatre, allows the colorectal surgeon to visualize and assess bowel vascularization, to identify lymph nodes draining a cancer site and to identify ureters. Herein, we review the literature regarding NIRF in colorectal surgery.

Utility of Intraoperative Fluorescence Imaging in Gynecologic Surgery: Systematic Review and Consensus Statement

BACKGROUND

This study aimed to review the current knowledge on the utility of intraoperative fluorescence imaging in gynecologic surgery and to give evidence-based recommendations to improve the quality of care for women who undergo gynecologic surgery.

METHODS

A computer-based systematic review of the MEDLINE, CENTRAL, Pubmed, EMBASE, and SciSearch databases as well as institutional guidelines was performed. The time limit was set at 2000-2019. For the literature search, PRISMA guidelines were followed. A modified-Delphi method was performed in three rounds by a panel of experts to reach a consensus of conclusions and recommendations.

RESULTS

Indocyanine green (ICG) is used primarily in gynecology for sentinel node-mapping. In endometrial and cervical cancer, ICG is a feasible, safe, time-efficient, and reliable method for lymphatic mapping, with better bilateral detection rates. Experience in vulvar cancer is more limited, with ICG used together with Tc-99 m as a dual tracer and alone in video endoscopic inguinal lymphadenectomy. In early ovarian cancer, results are still preliminary but promising. Indocyanine green fluorescence imaging also is used for ureteral assessment, allowing intraoperative ureteral visualization, to reduce the risk of ureteral injury during gynecologic surgery.

CONCLUSIONS

For most gynecologic cancers, ICG fluorescence imaging is considered the tracer of choice for lymphatic mapping. The use of this new technology expands to a better ureteral assessment.

Ureter Identification In an Inflammatory Pig Model Using a Novel Near-Infrared Fluorescent Dye

BACKGROUND AND OBJECTIVES

Ureters are at risk of injury in settings of inflammation and distorted anatomy. The use of a fluorescent dye can improve intraoperative ureteral identification without the need for any additional invasive procedures. Our team has previously described the development of a preclinical ureter-specific dye, UL-766, tested in a rat model. Here, we present the use of the fluorescent dye during laparoscopy to assist in ureteral identification in a swine model with an inflamed abdomen; the results of this study serve as proof of feasibility for use in the setting of tissue edema and erythema.

STUDY DESIGN/MATERIALS AND METHODS

With institutional approval, two 20-25 kg pigs underwent abdominal surgery with the use of a Food and Drug Administration-approved fluorescence laparoscopic system. Using standard laparoscopy, inflammation was induced with sharp and blunt dissection and irritation was induced with gauze. The animals were allowed to recover and returned to the operating room after 7 days. Images of the inflamed right retroperitoneum, with fluorescence imaging, turned on, were taken before and after intravenous injection of the novel fluorescent dye at 120 μg/kg. The time until fluorescence visualization of the ureters was measured, and the fluorescent signal was measured for up to 4 hours from the time of the initial dye injection. Partial and complete transection of ureteral injuries was made by scissors and monitored under both standard video and fluorescence laparoscopy.

RESULTS

Inflammation reduced the certainty of ureter identification by white light alone. Despite surrounding tissue erythema and edema, ureteral visualization under fluorescence laparoscopy was achieved within 5-10 minutes after dye injection. The fluorescent signal remained visible for at least 4 hours after injection, and the fluorescent dye showed a partial ureteral injury that would not have been observed under standard laparoscopy.

CONCLUSIONS

UL-766 is a preclinical fluorescent dye useful for the intraoperative identification of the ureters and ureteral injuries in an inflamed abdomen. With the acquisition of additional preclinical data, this novel dye can be a valuable tool during laparoscopic abdominal and pelvic surgeries. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

Fluorescence Imaging of the Ureter in Minimally Invasive Pelvic Surgery

STUDY OBJECTIVE

Determine near-optimal dose, safety, and efficacy of nerindocianine in pelvic ureter detection with near-infrared fluorescence imaging in women undergoing minimally invasive pelvic surgery with 3 Food and Drug Administration-cleared imaging systems.

DESIGN

Open label, phase 1/2a study.

SETTING

University of Alabama at Birmingham.

PATIENTS

Forty-one female subjects undergoing minimally invasive gynecologic surgery.

INTERVENTIONS

Subjects received a single dose of nerindocianine sodium, starting at 0.06-mg/kg body weight and increased/decreased until the near-optimal dose was determined (part A). Examine the degree of concordance between endoscopic and robotic devices (part B).

MEASUREMENTS AND MAIN RESULTS

In part A, composite scores were collected every 10 minutes for 30 minutes and then every 15 minutes through 90 minutes using a scale measuring the anatomy/laterality of ureter visualization. In part B (paired imaging system efficacy), 2 cohorts of 8 subjects each received the near-optimal dose. Composite scores for visualization of the ureter were collected at 10 and 30 minutes postinfusion with the Firefly Imaging System and either the PINPOINT or 1588 AIM endoscope. Composite scores were compared to examine the degree of concordance between devices. Part A comprised 25 total subjects enrolled in dosing groups 1, 2, and 3 (0.06-, 0.12-, and 0.045-mg/kg, respectively). Median time to first ureter visualization was 10 minutes (all groups). The nerindocianine 0.06-mg/kg and 0.12-mg/kg groups had longer length of time of visualization than the 0.045-mg/kg group, resulting in the selection of 0.06 mg/kg as the near-optimal dose. Part B enrolled 16 total subjects in 2 groups dosed at 0.06 mg/kg. Efficacy analysis showed no statistically significant difference in composite scores with Firefly versus PINPOINT or 1588 AIM.

CONCLUSION

Nerindocianine was well tolerated with visualization of the ureter demonstrated in 88.9% of the subjects through 90 minutes postdosing. No meaningful visualization differences were observed among the Food and Drug Administration-cleared surgical imaging systems used.

A Near-Infrared Fluorescent Probe Coated with β-Cyclodextrin Molecules for Real-Time Imaging-Guided Intraoperative Ureteral Identification and Diagnosis

Although iatrogenic ureteral injury and its lack of recognition due to ureteral invisibility are serious incidents in open and laparoscopic abdominal surgeries, there are currently no safe and effective methods for intraoperative ureteral identification (IUI) and diagnosis (IUD). In this study, I designed and chemically synthesized a near-infrared fluorescence (NIRF) imaging probe (CD-NIR-1) and evaluated its clearance and ability for IUI and IUD in animal models. CD-NIR-1 demonstrated high specificity and ultrarapid clearance by rat kidneys to the urinary bladder following intravenous administration of a single dose (25 nmol/kg of body weight), with 96% of the dose ultimately excreted at the first urination with no chemical modification. Furthermore, urine containing CD-NIR-1 in ureters showed strong NIRF, thereby enabling IUI and IUD via NIRF imaging. These results demonstrated the efficacy of CD-NIR-1 for clinical use.

The sentinel stent? A systematic review of the role of prophylactic ureteric stenting prior to colorectal resections

PURPOSE

'Prophylactic' ureteric stents potentially reduce rates, and facilitate intraoperative recognition, of iatrogenic ureteric injury (IUI) during colorectal resections. A lack of consensus surrounds the risk-benefit equation of this practice, and we aimed to assess the evidence base.

METHODS

A systematic review was performed according to PRISMA guidelines. MEDLINE, Scopus, EMBASE and Cochrane databases were searched using terms 'ureteric/ureteral/JJ/Double J stent' or 'ureteric/ureteral catheter' and 'colorectal/prophylactic/resection/diverticular disease/diverticulitis/iatrogenic injury'. Primary outcomes were rates of ureteric injuries and their intraoperative identification. Secondary outcomes included stent complication rates.

RESULTS

We identified 987 publications; 22 papers met the inclusion criteria. No randomised controlled trials were found. The total number of patients pooled for evaluation was 869,603 (102,370 with ureteric stents/catheters, 767,233 controls). The most frequent indications for prophylactic stents were diverticular disease (45.38%), neoplasia (33.45%) and inflammatory bowel disease (9.37%). Pooled results saw IUI in 1521/102,370 (1.49%) with, and in 1333/767,233 (0.17%) without, prophylactic ureteric stents. Intraoperative recognition of IUIs occurred in 10/16 injuries (62.5%) with prophylactic stents, versus 9/17 (52.94%) without stents (p = 0.579). The most serious complications of prophylactic stent use were ureteric injury (2/1716, 0.12%) and transient ureteric obstruction following stent removal (13/666, 1.95%).

CONCLUSIONS

Placement of prophylactic ureteric stents has a low complication rate. There is insufficient evidence to conclude that stents decrease ureteric injury or increase intraoperative detection of IUIs. Apparently higher rates of IUI in stented patients likely reflect use in higher risk resections. A prospective registry with harmonised data collection points and stratification of intraoperative risk is needed.

Intraoperative ureter visualization using a near-infrared imaging agent

The fluorescent imaging agent IS-001 was determined to be well tolerated in all subjects and has the potential to provide ureter visualization throughout minimally invasive hysterectomy procedures. This study was conducted to evaluate clinical safety and efficacy of a real-time ureter visualization technique for use during hysterectomy surgery. The study drug appears safe, is renally excreted, and allows enhanced ureter visualization when imaged with a clinically approved near-infrared sensitive endoscope. This is a first-in-human study showing preliminary results that the drug is safe and effective during surgery for improved ureter visualization.

Prognostic imaging of iatrogenic and traumatic ureteral injury by near-infrared fluorescence

Background

Iatrogenic or traumatic ureteral injuries are life-threatening but difficult to diagnose early. Ureteral visualization is essential for both the prevention and diagnosis of iatrogenic or traumatic ureter injuries. In the present study, we evaluated the feasibility of near-infrared (NIR) with ZW800-1C as a diagnostic tool of iatrogenic or traumatic ureteral injury in addition to ureter visualization, compared to methylene blue.

Methods

With mice model, we compared the image quality of ZW800-1C with methylene blue for ureter visualization. We also made ureter perforation, obstruction, crushing injury, and transection model with mice and evaluated the feasibility of ZW800-1C for diagnostic tool for ureteral injuries.

Results

We could confirm the ureter in the ZW800-1C images in maximally 30 minutes after injection, and the ureter was visible until NIR imaging concluded at 180 minutes after injection. However, methylene blue failed to provide clear ureter imaging during the same period. ZW800-1C imaging successfully visualized ureters subjected to obstruction, transection, perforation, and crush injuries, although urinary leakage was not visible by eye.

Conclusions

Our results indicate ZW800-1C is better suited for ureter visualization than methylene blue and that ZW800-1C has considerable potential for the early diagnosis of various ureteral injuries.

Emerging Fluorescent Molecular Tracers to Guide Intra-Operative Surgical Decision-Making

Fluorescence imaging is an emerging technology that can provide real-time information about the operating field during cancer surgery. Non-specific fluorescent agents, used for the assessment of blood flow and sentinel lymph node detection, have so far dominated this field. However, over the last decade, several clinical studies have demonstrated the great potential of targeted fluorescent tracers to visualize tumor lesions in a more specific way. This has led to an exponential growth in the development of novel molecular fluorescent contrast agents. In this review, the design of fluorescent molecular tracers will be discussed, with particular attention for agents and approaches that are of interest for clinical translation.

Currently available and experimental dyes for intraoperative near-infrared fluorescence imaging of the ureters: a systematic review

Background

Iatrogenic ureteral injury (IUI) following abdominal surgery has a relatively low incidence, but is associated with high risks of morbidity and mortality. Conventional assessment of IUI includes visual inspection and palpation. This is especially challenging during laparoscopic procedures and has translated into an increased risk of IUI. The use of near-infrared fluorescent (NIRF) imaging is currently being considered as a novel method to identify the ureters intraoperatively. The aim of this review is to describe the currently available and experimental dyes for ureter visualization and to evaluate their feasibility of using them and their effectiveness.

Methods

This article adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) standard for systematic reviews. A systematic literature search was performed in the PubMed database. All included articles were screened for eligibility by two authors. Three clinical trial databases were consulted to identify ongoing or completed unpublished trials. Risk of bias was assessed for all articles.

Results

The search yielded 20 articles on ureter visualization. Two clinically available dyes, indocyanine green (ICG) and methylene blue (MB), and eight experimental dyes were described and assessed for their feasibility to identify the ureter. Two ongoing clinical trials on CW800-BK and one trial on ZW800-1 for ureter visualization were identified.

Conclusions

Currently available dyes, ICG and MB, are safe, but suboptimal for ureter visualization based on the route of administration and optical properties, respectively. Currently, MB has potential to be routinely used for ureter visualization in most patients, but (cRGD-)ZW800-1 holds potential for this role in the future, owing to its exclusive renal clearance and the near absence of background. To assess the benefit of NIRF imaging for reducing the incidence of IUI, larger patient cohorts need to be examined.

Electronic supplementary material

The online version of this article (10.1007/s10151-019-01973-4) contains supplementary material, which is available to authorized users.

PEGylated BF2-Azadipyrromethene (NIR-AZA) fluorophores, for intraoperative imaging

Clinical imaging utilising near-infrared fluorescence is growing as an intraoperative aid for the decision-making processes during complex surgical procedures. Existing uses include perfusion assessment and lymph node identification with many new applications currently being proposed and developed. While imaging hardware and software have significantly progressed in recent times, suitable NIR-fluorophores remain a limiting factor. In this report, we describe the design, synthesis, photophysical characterization and in vivo imaging assessment of new PEGylated NIR-fluorophores based on the BF₂-azadipyrromethene fluorophore class. The synthetic route includes PEGylation as the final step, thereby allowing routine access to derivatives substituted with different molecular weights of PEG. Absorption and emission wavelength maxima in PBS lie at 690 and 720 nm respectively with quantum yields over 12%. They show excellent photostability and no light induced singlet oxygen production. A time-course of NIR-fluorescence imaging, post i.v. administration, in BALB/c mice showed a rapid and preferential accumulation in the renal excretion pathway within 20 min, indicative of potential clinical usage for intraoperative identification of vial structures along this pathway. Assessment with clinical imaging equipment showed the NIR-AZA fluorophores to be wavelength compatible and brighter than currently used methylene blue (MB), and that they have the ability to be imaged simultaneously with indocyanine green (ICG) offering a potential for dual colour clinical imaging.

Evaluation of a novel dye for near-infrared fluorescence delineation of the ureters during laparoscopy

BACKGROUND

Iatrogenic ureteric injury remains a risk in laparoscopic pelvic procedures. Near-infrared fluorescence (NIRF) imaging is a promising new technique for enhanced intraoperative visualization of anatomical structures that could improve the safety of laparoscopic surgery. A new dye, IRDye® 800-BK, has been developed for intraoperative visualization of the ureters using NIRF. The present study was a first evaluation of the performance of IRDye® 800-BK for ureteric imaging during NIRF laparoscopy.

METHODS

This study consisted of three parts: real-time in vivo NIRF imaging using IRDye® 800-BK in pigs during laparoscopic surgery, ex vivo NIRF imaging of freshly explanted pig ureters and ex vivo NIRF imaging of explanted human ureters.

RESULTS

In all animals, both left and right ureters were visualized throughout the laparoscopic procedure for 120 min, with the best results at a dose of 0·15 mg dye per kg bodyweight. NIRF imaging was successful in all human and porcine ureters studied, with a range of dye concentrations.

CONCLUSION

NIRF imaging of the ureters using IRDye® 800-BK was used successfully both in vivo in a porcine model, and ex vivo in porcine and human ureters.

Intraoperative Ureter Visualization Using a Novel Near-Infrared Fluorescent Dye

Ureters can be accidentally severed during pelvic surgeries, significantly prolonging the times in the operating room to allow for complete repair of damaged ureters and leading to significant morbidities associated with consequent ureter obstruction and possible kidney dysfunction. In an effort to prevent these complications, light-emitting stents and urine-excreted dyes have been introduced to illuminate the ureter during surgery. However, problems with mechanical insertion, ureter spasm, image contrast, and localized injection have limited interest in their clinical applications. We report here the synthesis and characterization of a new near-infrared (NIR) fluorescent dye (UreterGlow) that can be injected systemically but is excreted primarily through the renal system, allowing ureter imaging with an NIR fluorescence camera. Following intravenous injection of 0.1 mg/kg UreterGlow, we have monitored the flow of UreterGlow through the proximal, medial, and distal segments of the ureter. The timing of ureter visualization was calculated from the time of injection of the drug. The null hypothesis was that "Visualization of the ureter in pigs is possible 60 min after administration of UreterGlow using an NIR camera". UreterGlow displayed excitation and emission maxima of λ_ex = 800 nm and λ_em = 830 nm in phosphate buffered saline, pH 7.4, and could be imaged in the urinary tract in mice. Shortly after injection of UreterGlow into Yorkshire pigs, peristalsis of the ureter could be observed. The distal ureter could be visualized under NIR illumination after 60 min with constant fluorescence in all five pigs for >2 h. The same ureters could not be seen using visible light ( X², p = 0.0001). Because both excitation and emission of UreterGlow occurs at >30 nm longer wavelength than most tumor-imaging fluorescent dyes, it should be possible to distinguish ureter fluorescence from tumor fluorescence with this dye.

Fluorescence-guided surgery of cancer: applications, tools and perspectives

Thousands of patients die each year from residual cancer that remains following cytoreductive surgery. Use of tumor-targeted fluorescent dyes (TTFDs) to illuminate undetected malignant tissue and thereby facilitate its surgical resection shows promise for reducing morbidity and mortality associated with unresected malignant disease. TTFDs can also improve i) detection of recurrent malignant lesions, ii) differentiation of normal from malignant lymph nodes, iii) accurate staging of cancer patients, iv) detection of tumors during robotic/endoscopic surgery (where tumor palpation is no longer possible), and v) preservation of healthy tissue during resection of cancer tissue. Although TTFDs that passively accumulate in a tumor mass provide some tumor contrast, the most encouraging TTFDs in human clinical trials are either enzyme-activated or ligand-targeted to tumor-specific receptors.

A chemically stable fluorescent marker of the ureter

Surgical methods guided by exogenous fluorescent markers have the potential to define tissue types in real time. Small molecule dyes with efficient and selective renal clearance could enable visualization of the ureter during surgical procedures involving the abdomen and pelvis. These studies report the design and synthesis of a water soluble, net neutral C4'-O-alkyl heptamethine cyanine, Ureter-Label (UL)-766, with excellent properties for ureter visualization. This compound is accessed through a concise synthetic sequence involving an N- to O-transposition reaction that provides other inaccessible C4'-O-alkyl heptamethine cyanines. Unlike molecules containing a C4'-O-aryl substituent, which have also been used for ureter visualization, UL-766 is not reactive towards glutathione and the cellular proteome. In addition, rat models of abdominal surgery reveal that UL-766 undergoes efficient and nearly exclusive renal clearance in vivo. In total, this molecule represents a promising candidate for visualizing the ureter during a variety of surgical interventions.

Enhanced Visualization: From Intraoperative Tissue Differentiation to Augmented Reality

Background

Optimal visualization of the operative field and methods that additionally provide supportive optical information form the basis for target-directed and successful surgery. This article strives to give an overview of current enhanced visualization techniques in visceral surgery and to highlight future developments.

Methods

The article was written as a comprehensive review on this topic and is based on a MEDLINE search and ongoing research from our own group and from other working groups.

Results

Various techniques for enhanced visualization are described comprising augmented reality, unspecific and targeted staining methods, and optical modalities such as narrow-band imaging. All facilitate our surgical performance; however, due to missing randomized controlled studies for most of the innovations reported on, the available evidence is low.

Conclusion

Many new visualization technologies are emerging with the aim to improve our perception of the surgical field leading to less invasive, target-oriented, and elegant treatment forms that are of significant benefit to our patients.

Near-infrared fluorescence laparoscopy of the cystic duct and cystic artery: first experience with two new preclinical dyes in a pig model

Background

Imaging techniques that enhance visualisation of the anatomy may help prevent bile duct injury. Near-Infrared Fluorescence Imaging is such a technique. Previous experiments with ICG have shown that illumination of the extra-hepatic bile ducts is feasible. Yet, there is room for improvement in the visualisation of the target as compared to the background. Experiments with IRDye^® 800CW show promising results. However, this dye is too expensive for routine clinical use. The aim of this study is to test the first applicability of two newly developed preclinical dyes regarding intraoperative imaging of the cystic duct and cystic artery, compared with IRDye^® 800CW.

Methods

Laparoscopic cholecystectomy was performed in three pigs, using a laparoscopic fluorescence imaging system. Each pig received 6 mg of one of the fluorescent dyes (1 mg/mL; IRDye^® 800CW, IRDye^® 800BK or IRDye^® 800NOS) by intravenous injection. Intraoperative recognition of the biliary system and cystic artery was registered at set time points. All procedures were digitally recorded, and the target to background ratio (TBR) was determined to assess the fluorescence signal.

Results

With all three fluorescent dyes, the cystic artery was directly visualised. For the visualisation of the cystic duct, 15, 34 and 30 min were needed using IRDye^® 800BK, IRDye^® 800NOS and IRDye^® 800CW, respectively. The maximum TBR of the cystic duct was the highest with IRDye^® 800NOS (4.20) after 36 min, compared to 2.45 for IRDye^® 800BK and 2.15 for IRDye^® 800CW, both after 45 min. There were no adverse events.

Conclusion

IRDye^® 800BK and IRDye^® 800NOS seem to be good alternatives for IRDye^® 800CW for the visualisation of the cystic duct and cystic artery in pigs.

The quest for precision in transanal total mesorectal excision

Transanal total mesorectal excision (TME) is an emerging minimally invasive approach to rectal cancer, with encouraging preliminary results. However, the new surgical anatomy of the bottom-up approach complicates surgical understanding and increases the risks of inadvertent injuries to crucial anatomical structures, including nerves. Key elements to improve the safety and stimulate interest in such a complex technique might be robotics and image guidance, to enhance the level of precision. In this editorial, some of the technologies that could be used for precision TME are outlined, in light of the experience of our Institute for Image-Guided Surgery.