Technical description and feasibility of laparoscopic adrenal contouring using fluorescence imaging

Impact of indocyanine green on decision making for performing laparoscopic cortical sparing adrenalectomy

BACKGROUND

Indocyanine green imaging (ICG) is an expansion technology that can contribute to the development of demanding techniques such as cortical-sparing adrenalectomy (CSA). The aim of this study was to determine in which cases CSA should be performed and when total adrenalectomy should be performed instead based on ICG fluorescence. Here, we present our experience through a series of cases and videos.

METHODS

Prospective and descriptive study on patients with surgical adrenal lesions who were proposed for CSA using ICG with near-infrared fluorescence imaging in our center. A first bolus of 6,25 mg ICG was administered intravenously upon exposure of the retroperitoneal plane. Fluorescence was visualized using a Storz® NIR/ICG endoscopic system.

RESULTS

Seven patients were proposed for CSA. After the application of ICG, a change in attitude was carried out in 71.4% of the cases (five of seven). In the two patients in whom CSA could be performed, the adrenal remnants were functional, and the resection margins of the surgical specimens were free of disease. The reasons why partial adrenalectomy could not be completed, and a total adrenalectomy was decided instead were the presence of a tumor located very close to the adrenal vein that prevented a correct remnant volume (n = 4) and one case of isofluorescent tumor with the adrenal parenchyma.

CONCLUSION

ICG fluorescence guidance could help in the decision making to select patients intraoperatively for successful cortical preservation.

Imaging guided adrenalectomy with Indocyanine green fluorescence in a dog with a pheochromocytoma

IMPORTANCE

This case report presents the successful surgical removal of a pheochromocytoma in a dog using indocyanine green (ICG) fluorescence imaging.

CASE PRESENTATION

A 10-year-old, 6.87 kg, spayed female poodle was referred for an abdominal mass and eight episodes of vomiting. Computed tomography revealed masses in the spleen and left adrenal gland. Based on the plasma normetanephrine levels, the patient was diagnosed with pheochromocytoma. Subsequently, a total splenectomy and left adrenalectomy were performed. A dose of 5 mg/kg ICG was administered intravenously 24 h prior to surgery. Using ICG allowed visualization of tumor margins, aiding in complete resection and minimizing anesthesia-related risks.

CONCLUSIONS AND RELEVANCE

No evidence of recurrence or metastasis has been observed for 12 months. To our knowledge, this is the first report of the surgical removal of a pheochromocytoma using intraoperative ICG imaging in veterinary medicine. This case highlights the efficacy of ICG fluorescence imaging as a valuable tool for the surgical management of adrenal tumors in veterinary medicine.

Fluorescence imaging to visualize the recurrent laryngeal nerve during thyroidectomy procedures: analysis of 65 cases and 81 nerves

BACKGROUND

Recurrent laryngeal nerve (RLN) injury after thyroidectomy is relatively common. Locating the RLN prior to thyroid dissection is paramount to avoid injury. We developed a fluorescence imaging system that permits nerve autofluorescence. We aimed to determine the sensitivity and specificity of fluorescence imaging at detecting the RLN relative to thyroid and other background tissue and compared it to white light.

METHODS

In this prospective study, 65 patients underwent thyroidectomy from January to April 2022 (16 bilateral thyroid resections) using white and fluorescent light. Fluorescence intensity [relative fluorescence units (RFU)] was recorded for RLN, thyroid, and background. RFU mean, minimum, and maximum values were calculated using Image J software. Thirty randomly selected pairs of white and fluorescent light images were independently reviewed by two examiners to compare RLN detection rate, number of branches, and length and minimum width of nerves visualized. Parametric and nonparametric statistical analysis was performed.

RESULTS

All 81 RNLs observed were visualized more clearly under fluorescence (mean intensity, µ = 134.3 RFU) than either thyroid (µ = 33.7, p < 0.001) or background (µ = 14.4, p < 0.001). Forest plots revealed no overlap between RLN intensity and that of either other tissue. Sensitivity and specificity for RLN were 100%. All 30 RLNs and all 45 nerve branches were clearly visualized under fluorescence, versus 17 and 22, respectively, with white light (both p < 0.001). Visible nerve length was 2.5 × as great with fluorescence as with white light (µ = 1.90 vs. 0.76 cm, p < 0.001).

CONCLUSIONS

In 65 patients and 81 nerves, RLN detection was markedly and consistently enhanced with autofluorescence neuro-imaging during thyroidectomy, with 100% sensitivity and specificity.

Characterization of indocyanine green fluorescence imaging patterns of pheochromocytomas

BACKGROUND

Indocyanine green (ICG) fluorescence is a new intraoperative imaging modality for adrenal tumors. Previous work suggested that pheochromocytomas did not show fluorescence, but experience is limited. The objective of this study is to analyze fluorescence imaging patterns of pheochromocytomas.

METHODS

This was an IRB-approved retrospective study. Patients who underwent adrenalectomy with ICG imaging were identified from a departmental database. Intraoperative fluorescence patterns were analyzed by reviewing surgical videos. Descriptive and comparative statistical analyses were performed to determine factors associated with different fluorescence patterns of pheochromocytomas.

RESULTS

Of the 46 pheochromocytomas included, 50% (n = 23) exhibited fluorescence. Parameters predicting fluorescence on univariate analysis were age, tumor size and hereditary. On multivariate analysis, tumor size was the only predictive parameter of ICG fluorescence, with loss of fluorescence at a threshold of > 3.2 cm (p = 0.004).

CONCLUSIONS

This is the largest cohort to date assessing fluorescence properties of pheochromocytomas. In contrast to previous studies, we demonstrated that smaller pheochromocytomas do exhibit fluorescence. This may support the application of intraoperative ICG imaging for smaller or bilateral pheochromocytomas, which may assist in identification and/or cortical-sparing during adrenalectomy.

Adrenal Near-Infrared Autofluorescence

Context

Parathyroid tissue is one of the few tissues to have strong near-infrared (NIR) autofluorescence, which has been exploited to improve intraoperative parathyroid identification. The US Food and Drug Administration has approved 2 devices for this purpose. Adrenal glands can be difficult to distinguish from surrounding fat, an issue during total adrenalectomy.

Objective

We hypothesized adrenal tissue may also possess considerable NIR autofluorescence.

Methods

Resected patient adrenal specimens were examined after robotic adrenalectomy with an NIR camera intraoperatively. Patients did not receive fluorescent dye. Images were taken of both gross and sectioned specimens. Post hoc image analysis was performed with ImageJ software. Confocal microscopy was performed on selected tissues using immunofluorescence and hematoxylin-eosin staining.

Results

Resected tissue was examined from 22 patients undergoing surgery for pheochromocytomas (6), primary aldosteronism (3), adrenocorticotropin-independent hypercortisolism (10), and a growing or suspicious mass (3). Normal adrenal tissue demonstrated strong NIR autofluorescence. The intensity ratio compared to background (set as 1) for gross images was 2.03 ± 0.51 (P < .0001) compared to adjacent adipose of 1.24 ± 0.18. Autofluorescence from adrenal tumors was also detected at variable levels of intensity. Cortisol-producing tumors had the highest fluorescence ratio of 3.01 ± 0.41. Confocal imaging localized autofluorescence to the cytosol, with the highest intensity in the zona reticularis followed by the zona fasciculata.

Conclusion

Normal and abnormal adrenal tissues possess natural NIR autofluorescence. Highest autofluorescence levels were associated with cortisol-producing tumors. Confocal imaging demonstrated the highest intensity in the zona reticularis. NIR cameras may have the potential to improve identification of adrenal tissue during surgery.

A visual quantification of tissue distinction in robotic transabdominal lateral adrenalectomy: comparison of indocyanine green and conventional views

BACKGROUND

Recent studies have reported the feasibility of indocyanine green fluorescence imaging of adrenal tumors to guide dissection. Although the adrenal has been reported to concentrate the dye more than surrounding tissues, the amount of tissue distinction and how this compares with conventional vision has not been quantified before. The aim of this study is to quantify this distinction using color analysis.

METHODS

This was an institutional review board-approved retrospective study. By excluding adrenal cortical carcinoma, metastasis and pheochromocytoma, video recordings of 50 patients who underwent robotic transabdominal lateral adrenalectomy with indocyanine green (ICG) imaging for adrenocortical tumors between August 2015 and May 2018 were reviewed. Using a color analysis software, the pixel intensity of adrenal tumors versus adjacent retroperitoneal tissues was calculated for conventional red, green and blue, as well as indocyanine green (ICG) scales. Statistical analysis was performed using ANOVA.

RESULTS

A total of 50 patients underwent unilateral robotic transabdominal lateral adrenalectomy. All procedures were completed robotically without a conversion to laparoscopy or open. Morbidity was 4%. Measured pixel intensity of adrenal tumors was higher than adjacent retroperitoneal tissues for all conventional color and ICG modes (p < 0.0001), with the gradient being more pronounced for ICG green versus conventional red, green and blue modes.

CONCLUSIONS

To our knowledge this is the first study attempting to encode tissue planes in robotic adrenalectomy. The results show that the visual contrast distinction observed between adrenal and adjacent retroperitoneal tissues can be quantified using pixel intensity. ICG enabled the distinction of tissue planes with a wider gradient compared to conventional RGB view, quantifying its subjective benefits reported in prior studies.

Indocyanine green fluorescence imaging for robotic adrenalectomy

Despite the novel and innovative developments in minimal invasive platforms and the expanding indications regarding adrenal surgery, surgeons are still confronted with some obstacles. The use of intraoperative indocyanine green aims to overcome these problems, but there is still limited data and ongoing debates in terms of robot-assisted adrenal surgery. The aim of this article is to discuss the benefit of indocyanine green fluorescence imaging for robot-assisted adrenalectomy and provide up-to date data.

Laparoscopic partial adrenalectomy using near-infrared imaging: the initial experience

INTRODUCTION

To present our initial clinical experience with laparoscopic partial adrenalectomy using indocyanine green dye with near-infrared fluorescence imaging.

MATERIAL AND METHODS

A total of eight patients underwent transperitoneal laparoscopic partial adrenalectomy using indocyanine green dye with near-infrared fluorescence imaging in our clinic. After 5 mg intravenous indocyanine green dye administration, we resected the mass under the guidance of near-infrared fluorescence imaging and white light visualization in an effort to completely excise the mass while sparing uninvolved adrenal tissue.

RESULTS

Seven patients underwent unilateral and one patient underwent bilateral laparoscopic partial adrenalectomy. The median tumor size was 43 mm. The surgery was successfully performed with negative margins in all patients. The tumors were hypofluorescent relative to normal adrenal tissue with indocyanine green dye with near-infrared fluorescence imaging in patients with Cushing's syndrome, aldosteronoma, and adrenal cyst. However, pheochromocytoma and angiomyolipoma were noted to be isoflourorescent and hyperfluorescent relative to normal adrenal parenchyma, respectively.

CONCLUSIONS

Laparoscopic partial adrenalectomy using intraoperative indocyanine green dye with near-infrared fluorescence imaging seems to be safe and feasible. This technology may ultimately be helpful in resecting lesions with more precise surgical margins by identifying the vascular structure during laparoscopic partial adrenalectomy. Abbreviations: LTA: Laparoscopic total adrenalectomy; LPA:Laparoscopic partial adrenalectomy; ICG: Indocynanine green; NIRF: Near-infrared fluorescence; HPA: Hypothalamic-pituitary-adrenal.

Indocyanine green fluorescence imaging during partial adrenalectomy

BACKGROUND

Indocyanine green (ICG) fluorescence imaging represents an emerging technology that facilitates the assessment of tissue vascularity, tissue distinction, and tumor localization during surgery. The aim of this study was to investigate the potential role of ICG imaging during laparoscopic partial adrenalectomy.

METHODS

Indocyanine fluorescence imaging was carried out during laparoscopic partial adrenalectomy for bilateral pheochromocytoma and bilateral Cushing's syndrome. A first bolus of 5 mg ICG was applied intravenously upon exposure of the retroperitoneal plane to identify the adrenal borders. The fluorescence was visualized using a Storz^® NIR/ICG endoscopic system. As the camera of this system detects NIR light as a blue signal, the well-vascularized adrenal tissue was expected to show a strong fluorescence in the blue color channel in contrast to the surrounding adipose tissue. Following partial adrenalectomy, a second bolus of 5 mg ICG was applied intravenously to evaluate the vascularity of the remaining adrenal tissue.

RESULTS

We investigated six adrenal glands from three patients undergoing bilateral partial adrenalectomy. The indication for surgery was pheochromocytoma in two patients and Cushing's syndrome with bilateral adenomas in one patient. Regarding left adrenalectomies, ICG imaging was helpful in visualizing the adrenal borders and the adrenal vein. Further, it facilitated the identification of the hypofluorescent pheochromocytoma and to resect the entire tumor. On the right side, due to the more apparent anatomy, ICG imaging did not contribute to the conduct of the operation. Four adrenal remnants showed a strong vascularization and two remnants were only reasonably vascularized.

CONCLUSION

ICG fluorescence may be helpful in guiding partial adrenalectomy and assessing the vascularity of remaining adrenal tissue.

Fluorescence-enabled assessment of adrenal gland localization and perfusion in posterior retroperitoneoscopic adrenal surgery in a preclinical model

BACKGROUND

The posterior retroperitoneoscopic adrenal access represents a challenge in orientation and working space creation. The aim of this experimental acute study was to evaluate the impact of computer-assisted quantitative fluorescence imaging on adrenal gland identification and assessment of intraoperative remnant perfusion for adrenal resection in the posterior retroperitoneoscopic approach.

METHODS

Six pigs underwent simultaneous (n = 5) or sequential (n = 1) bilateral posterior retroperitoneoscopic adrenalectomy (n = 12). Fluorescence imaging was obtained via intravenous administration of 3 mL of Indocyanine Green (ICG) and by switching the camera systems to near-infrared mode (D-LIGHT P, KARL STORZ; Germany). Fluorescence-based visualization of adrenal glands before vascular division (n = 4), after the main vascular pedicle ligation (negative control, n = 1) or after adrenal resection (n = 7), was followed by completion adrenalectomy. The fluorescence signal intensity dynamics were recorded and analyzed using proprietary software. For each pixel, the slope of fluorescence signal intensity evolution over time was translated into a color-coded perfusion cartography, which was superimposed onto real-time images obtained with the corresponding left and right camera systems. Quantitative fluorescence signal analysis in the regions of interest (ROIs) served to assess adrenal remnant perfusion in divided adrenal glands.

RESULTS

In the retroperitoneum, the vascular anatomy was illuminated in fluorescence imaging first. The adrenal glands were promptly highlighted after primary intravenous ICG administration (n = 9) or showed a fluorescence signal intensity increase upon reinjection (n = 3). Quantitative fluorescence analysis showed a statistically significant difference between perfused and ischemic segments in divided glands (p = 0.0156).

CONCLUSIONS

Fluorescence imaging provides real-time guidance during minimally invasive adrenal surgery. Prior to dissection, it allows to easily discriminate the adrenal gland from surrounding retroperitoneal structures. After adrenal gland division, ICG injection associated with a computer-assisted quantitative analysis helps to distinguish between well-perfused and ischemic segments. Further studies are underway to establish the correlation between remnant perfusion and viability.

Characterization of fluorescence patterns exhibited by different adrenal tumors: Determining the indications for indocyanine green use in adrenalectomy

BACKGROUND

A number of small studies have reported the use of indocyanine green imaging during adrenalectomy. Nevertheless, imaging properties of different tumors and the indications for indocyanine green imaging use in adrenalectomy have not been defined.

METHODS

This is an Institutional Review Board-approved retrospective review of a prospectively maintained database. Consenting patients underwent indocyanine green imaging fluorescence-guided robotic adrenalectomy. Fluorescence patterns of adrenal tumors were assessed. Multivariate logistic regression was performed to determine the best clinical applications.

RESULTS

One hundred patients with Cushing syndrome (n = 29), pheochromocytoma (n = 24), primary hyperaldosteronism (n = 23), nonsecreting adrenocortical adenoma (n = 9), and other tumors (n = 15) underwent robotic adrenalectomy through lateral transabdominal (n = 77) and posterior retroperitoneal (n = 23) approaches. Mean tumor size was 3.6 cm and mean body mass index 33. A total of 74% of the tumors were hyperfluorescent compared with the surrounding retroperitoneal tissues, whereas the remaining 26% were nonfluorescent. Hyperfluorescence was predicted by adrenocortical tissue origin but not by demographic characteristics or tumor size. The contrast distinction between the tumor and the retroperitoneum was better, similar, or inferior on indocyanine green fluoresced compared with the nonfluoresced view in 41%, 27%, and 32% of patients, respectively. The utility was best for adrenocortical adenomas removed through a lateral transabdominal approach. Indocyanine green fluorescence imaging was used to confirm remnant viability in all 4 patients undergoing cortical-sparing adrenalectomy for pheochromocytoma (n = 2), adrenal cyst (n = 1), and lymphatic malformation (n = 1).

CONCLUSION

Adrenal tumors have different patterns of indocyanine green fluorescence based on histologic origin. Indocyanine green confers the highest utility for adrenocortical tumors removed through a lateral transabdominal approach and cortical-sparing adrenalectomy.

The use of near-infrared fluorescence imaging in endocrine surgical procedures

Near-infrared fluorescence imaging in endocrine surgery is a new, yet highly investigated area. It involves indocyanine green use as well as parathyroid autofluorescence. Several groups have described their technique and reported on the observed utility. However, there is no consensus on technical details. Furthermore, the correlation between intraoperative findings and postoperative outcomes is unclear. With this study, we aim to review the current literature on fluorescence imaging and share our insights on technical details.

Indocyanine green delivery systems for tumour detection and treatments

Indocyanine green (ICG) is a cyanine compound that displays fluorescent properties in the near infrared region. This dye is employed for numerous indications but nowadays its major application field regards tumour diagnosis and treatments. Optical imaging by near infrared fluorescence provides news opportunities for oncologic surgery. The imaging of ICG can be useful for intraoperative identification of several solid tumours and metastases, and sentinel lymph node detection. In addition, ICG can be used as an agent for the destruction of malignant tissue, by virtue of the production of reactive oxygen species and/or induction of a hyperthermia effect under irradiation. Nevertheless, ICG shows several drawbacks, which limit its clinical application. Several formulative strategies have been studied to overcome these problems. The rationale of the development of ICG containing drug delivery systems is to enhance the in vivo stability and biodistribution profile of this dye, allowing tumour accumulation and resulting in better efficacy. In this review, ICG containing nano-sized carriers are classified based on their chemical composition and structure. In addition to nanosystems, different formulations including hydrogel, microsystems and others loaded with ICG will be illustrated. In particular, this report describes the preparation, in vitro characterization and in vivo application of ICG platforms for cancer imaging and treatment. The promising results of all systems confirm their clinical utility but further studies are required prior to evaluating the formulations in human trials.