Intraoperative fluorescence vascular angiography: during tibial bypass

Intraoperative indocyanine green angiography in preventing hypoparathyroidism after thyroid cancer surgery

BACKGROUND

The aim of this study was to determine whether the use of indocyanine green angiography to identify devascularized parathyroids during thyroidectomy for thyroid cancer would decrease the rates of postoperative hypoparathyroidism.

METHODS

Retrospective study of patients who had undergone total thyroidectomy for treatment of thyroid cancer between March 2021 and March 2023. The indocyanine group included patients with all four parathyroids identified and evaluated by indocyanine green angiography at the end of the procedure. Those with parathyroid glands classified with no vascularization had the glands autotransplanted. A group without indocyanine angiography was used to compare results.

RESULTS

The analysis included 100 patients in each group. Indocyanine angiography identified 14.75% of devascularized parathyroids at surgery. The number of parathyroids with a score of 2 (i.e., good vascularization) was not a safe predictor of normal parathyroid hormone levels after surgery. Indeed, 29.2% of the patients with three parathyroids with a score of 2 developed transient hypoparathyroidism. Permanent hypoparathyroidism occurred in 7% of the patients without indocyanine group and in none of the patients in the indocyanine group (p = 0.014).

CONCLUSION

Intraoperative angiography with indocyanine green could contribute to reduce the occurrence of permanent hypoparathyroidism in patients undergoing surgical treatment for thyroid cancer.

Practicality and Hemodynamic Advantage of Microvascularly Augmented Pectoralis Major Musculocutaneous Flap: Technical Approach and Evidence Based on Indocyanine Green Angiography

ABSTRACT

We have recently shown that including the blood flow from the lateral thoracic artery (LTA) in addition to the thoracoacromial artery in the pectoralis major muscle musculocutaneous (PMMC) flap (bipedicle PMMC flap) can increase the perfusion of the flap. We also developed the concept of the supercharged PMMC flap, in which the LTA included in the flap was once cut and anastomosed to a cervical artery under a microscope. It is an effective solution to maintain the additional blood flow from the LTA, when the length of the LTA is compromised for reconstruction. The mandibular reconstruction of an oral cancer patient was performed with a supercharged PMMC flap. Intraoperative indocyanine green angiography was performed in a single pedicle, bipedicle, and supercharged conditions, and the videos were analyzed with a quantitative assessment system of perfusion using some parameters. As a result, blood supply from the LTA was essential for flap survival in this patient, and supercharging from the cervical artery improved flap perfusion compared with the perfusion in the bipedicle condition. The supercharged PMMC flap can resolve the compromise of pedicle length and be also hemodynamically advantageous, thus making the reconstruction more reliable than the conventional technique.

Intraoperative indocyanine green angiography for predicting postoperative hypoparathyroidism

BACKGROUND

Postoperative hypocalcemia is a common complication of thyroidectomy. This problem is most often associated with accidental devascularization or excision of the parathyroid glands (PG).

AIM

Aim was to study near-infrared (NIR) fluorescent imaging with intraoperative PG indocyanine green (ICG) angiography to help identify and preserve PG during total thyroidectomy in order to avoid postoperative hypocalcemia.

MATERIAL AND METHODS

From 2017 to 2022, a total of 92 patients underwent total thyroidectomy at Odessa Regional Hospital. Indications for surgery were multinodular goiter (n = 42), thyroid cancer (n = 43), and Graves' disease (n = 7). By randomization all patients were divided into two groups: in the control group, 48 patients underwent standard total thyroidectomy, and in the main group, 44 patients underwent NIR-assisted total thyroidectomy with ICG angiography. Serum calcium and parathyroid hormone levels were compared between the two groups of patients in 1, 7-15 days after surgery and then 3, 6 months later.

RESULTS

In the control group, based on a visual assessment of the PG, autotransplantation of the PG was conducted in only five cases. In the second group, autotransplantation was performed in 16 patients. The transient postoperative hypocalcemia was observed in 8 patients of the control group (16, 70%) and in the 2 patients of ICG group (4, 50%) on 5-10 postoperative days. In the first group, 2 patients at 3 months after surgery had permanent hypocalcaemia.

CONCLUSION

NIR fluorescent imaging with intraoperative PG ICG angiography is a safe and an easily repeatable method. This technique provides improved detecting and assessment of the perfusion of the PG. The need for autotransplantation of the PG can be determined more objectively using ICG imaging than simple visualization.

Does the advantage of transcutaneous oximetry measurements in diabetic foot ulcer apply equally to free flap reconstruction?

BACKGROUND

Transcutaneous oxygen pressure (TcpO₂) is a precise method for determining oxygen perfusion in wounded tissues. The device uses either electrochemical or optical sensors.

AIM

To evaluate the usefulness of TcpO₂ measurements on free flaps (FFs) in diabetic foot ulcers (DFUs).

METHODS

TcpO₂ was measured in 17 patients with DFUs who underwent anterolateral thigh (ALT)-FF surgery and compared with 30 patients with DFU without FF surgery.

RESULTS

Significant differences were observed in the ankle-brachial index; duration of diabetes; and haemoglobin, creatinine, and C-reactive protein levels between the two groups. TcpO₂ values were similar between two groups except on postoperative days 30 and 60 when the values in the ALT-FF group remained < 30 mmHg and did not increase > 50 mmHg.

CONCLUSION

Even if the flap is clinically stable, sympathectomy due to adventitia stripping during anastomosis and arteriovenous shunt progression due to diabetic polyneuropathy could lead to low TcpO₂ values in the ALT-FF owing to its thick fat tissues, which is supported by the slow recovery of the sympathetic tone following FF. Therefore, TcpO₂ measurements in patients with DFU who underwent FF reconstruction may be less accurate than in those who did not.

Simultaneous, Multi-Channel, Near-Infrared Fluorescence Visualization of Mesenteric Lymph Nodes Using Indocyanine Green and Methylene Blue: A Demonstration in a Porcine Model

Near-infrared fluorescence (NIRF) image-guided surgery is a useful tool that can help reduce perioperative complications and improve tissue recognition. Indocyanine green (ICG) dye is the most frequently used in clinical studies. ICG NIRF imaging has been used for lymph node identification. However, there are still many challenges in lymph node identification by ICG. There is increasing evidence that methylene blue (MB), another clinically applicable fluorescent dye, can also be useful in the intraoperative fluorescence-guided identification of structures and tissues. We hypothesized that MB NIRF imaging could be used for lymph node identification. The aim of this study was to evaluate the feasibility of intraoperative lymph node fluorescence detection using intravenously (IV) administered MB and compare it to ICG via a camera that has two dedicated near-infrared (NIR) channels. Three pigs were used in this study. ICG (0.2 mg/kg) was administered via a peripheral venous catheter followed by immediate administration of MB (0.25 mg/kg). NIRF images were acquired as video recordings at different time points (every 10 min) over an hour using the QUEST SPECTRUM^® 3 system (Quest Medical Imaging, Middenmeer, The Netherlands), which has two dedicated NIR channels for simultaneous intraoperative fluorescence guidance. The 800 nm channel was used to capture ICG fluorescence and the 700 nm channel was used for MB. The target (lymph nodes and small bowel) and the background (vessels-free field of the mesentery) were highlighted as the regions of interest (ROIs), and corresponding fluorescence intensities (FI) from these ROIs were measured. The target-to-background ratio (TBR) was then computed as the mean FI of the target minus the mean FI of the background divided by the mean FI of the background. In all included animals, a clear identification of lymph nodes was achieved at all time points. The mean TBR of ICG in lymph nodes and small bowel was 4.57 ± 1.00 and 4.37 ± 1.70, respectively for the overall experimental time. Regarding MB, the mean TBR in lymph nodes and small bowel was 4.60 ± 0.92 and 3.27 ± 0.62, respectively. The Mann-Whitney U test of the lymph node TBR/small bowel TBR showed that the TBR ratio of MB was statistically significantly higher than ICG. The fluorescence optical imaging technology used allows for double-wavelength assessment. This feasibility study proves that lymph nodes can be discriminated using two different fluorophores (MB and ICG) with different wavelengths. The results suggest that MB has a promising potential to be used to detect lymphatic tissue during image-guided surgery. Further preclinical trials are needed before clinical translation.

[Evaluation of tissue perfusion by indocyanine green fluorescein angiography in patients with neuroischemic diabetic foot syndrome after endovascular treatment]

OBJECTIVE

To evaluate the fluorescence angiography (FA) parameters with Indocyanine green (ICG) and their dynamics in diabetic foot patients after endovascular treatment.

MATERIAL AND METHODS

A single-center prospective non-blinded study was conducted with the inclusion of 47 diabetic foot patients with Chronic limb-threatening ischemia (CLTI). TcPO2 and FA-ICG were done before and after angioplasty. Zones of interest were selected for FA-ICG: the area of minimum and maximum fluorescence, the area of of the largest part of the foot. Also presented are the parameters of FA ICG: Tstart (sec) - the time of occurrence of min fluorescence (Istart, unit) in the zone of interest after the introduction of ICG; Tmax (sec) - the time to achieve max fluorescence (Imax, unit) after the introduction of ICG; Tmax -Tstart (sec) - the difference in the time of reaching Imax and Istart.

RESULTS

The median TcPO2 values indicated the presence of CLTI before revascularization. Technical success of revascularization was achieved in 45 patients. In the postoperative period, statistically significant changes in TcPO2 and Tstart, Tmax, Tmax-Tstar were obtained. A reduction in the time to reach the ICZ to the zones of interest was noted.

CONCLUSION

FA-ICG evaluate the visual and quantitative characteristics of perfusion of soft tissues of the foot. Reducing the time to reach the fluorescent substance in the areas of interest makes it possible to assume the restoration of the main blood flow to the foot. Further investigations are warranted to determine threshold values to predict wound healing and indications for revascularization.

Impact of N-Acetyl-Cysteine on Ischemic Stumps Following Major Lower Extremity Amputation: A Pilot Randomized Clinical Trial

OBJECTIVE

To evaluate the impact of N-acetyl-cysteine (NAC) on amputation stump perfusion and healing in patients with critical limb-threatening ischemia (CLTI).

BACKGROUND

Patients with CLTI are at increased risk of poor amputation site healing leading to increased procedure-associated morbidity.

METHODS

In a pilot, double-blind, placebo-controlled, randomized controlled trial, patients with CLTI undergoing major elective lower extremity amputation were randomized 1:1 to intravenous NAC (1200 mg twice-daily) or placebo for up to 5 days postoperatively. Primary outcomes were change in stump perfusion at postoperative day 3 (POD3) and POD5, and healing at POD30. Stumps were serially evaluated for wound healing, and tissue perfusion was evaluated using noninvasive laser-assisted fluorescent angiography.

RESULTS

Thirty-three patients were randomized to NAC (n = 16) or placebo (n = 17). Thirty-one patients were eligible for intent-to-treat analysis (NAC14; placebo17). Twenty patients (NAC7; placebo13) had amputation stump perfusion defects at POD0 and were considered high-risk for poor healing. Intent-to-treat analysis revealed no significant differences between treatment groups. Subgroup analysis of high-risk patients revealed differences in stump perfusion defect size (NAC-0.53-fold, placebo +0.71-fold; 95% confidence interval -2.11 to-0.35; P < 0.05) and healing (NAC [100%], placebo [46%]; P < 0.01) between study treatments.

CONCLUSIONS

Postoperative NAC administration may improve amputation stump perfusion and healing in patients with CLTI and tissue perfusion defects at the time of amputation. Intraoperative laser-assisted fluorescent angiogra-phy may help surgeons identify high-risk patients with stump perfusion defects and provide early adjunctive interventions. Future studies can further explore the therapeutic benefits of NAC in the healing and perfusion of other surgical operative sites in high-risk individuals.

TRIAL REGISTRATION

clinicaltrials.gov, Identifier: NCT03253328.

Assessment of Flap Viability for Complex Transmetatarsal Amputation Using Indocyanine Green Fluorescent Angiography: A Case Study

Despite advancements in the treatment of diabetic patients with "at-risk" limbs, minor and major amputations remain commonplace. The diabetic population is especially prone to surgical complications from lower extremity amputation because of comorbidities such as renal disease, hypertension, hyperlipidemia, microvascular and macrovascular disease, and peripheral neuropathy. Complication occurrence may result in increases in hospital stay duration, unplanned readmission rate, mortality rate, number of operations, and incidence of infection. Skin flap necrosis and wound healing delay secondary to inadequate perfusion of soft tissues continues to result in significant morbidity, mortality, and cost to individuals and the health-care system. Intraoperative indocyanine green fluorescent angiography for the assessment of tissue perfusion may be used to assess tissue perfusion in this patient population to minimize complications associated with amputations. This technology provides real-time functional assessment of the macrovascular and microvascular systems in addition to arterial and venous flow to and from the flap soft tissues. This case study explores the use of indocyanine green fluorescent angiography for the treatment of a diabetic patient with a large dorsal and plantar soft-tissue deficit and need for transmetatarsal amputation with nontraditional rotational flap coverage. The authors theorize that the use of indocyanine green may decrease postoperative complications and cost to the health-care system through fewer readmissions and fewer procedures.

Applications of indocyanine green in surgery: A single center case series

Background

Fluorescence imaging using indocyanine green (ICG) has revolutionized commonly performed general surgical procedures by providing superior anatomic imaging and enhancing safety for patients. ICG, when injected, shows a bright green fluorescence when subjected to the near infra-red (NIR) spectrum.

Materials and methods

We employed the use of ICG in Laparoscopic cholecystectomy, Intestinal Colorectal Anastomosis and Hernia to assess vascularity of resected ends and bowel viability, Sentinel Lymph node mapping, Vascular surgery to assess amputation stump success and in assessing Flap Vascularity and healing.

Results

ICG when administered had successfully shown bright green fluorescence in different cases thereby aiding in surgical procedures.

Conclusion

Routine intraoperative use of ICG could pave the way for a more objective assessment of different surgical circumstances and thereby reduce personalized barriers to aciurgy. ICG fluorescence therefore seems to be a promising apparatus in standard general surgical procedures minimizing untoward errors and improving patient conformance.

•

Fluorescence guided surgery, due to its enhanced visualization ability, has assisted surgeons in minimizing errors.

•

Indocyanine green (ICG) is the only fluorophore to be used in humans and has a wide margin of safety.

•

ICG shows a bright green fluorescence when subjected to near infra-red spectrum.

•

Fluorescence imaging using ICG is a valuable accompaniment to open and laparoscopic surgery.

•

Routine use of ICG provides better visual assessment which helps in decision making, thereby improving patient outcome.

Novel techniques for intraoperative parathyroid gland identification: a comprehensive review

INTRODUCTION

The parathyroid glands (PGs) are critical for calcium regulation and homeostasis. The preservation of PGs during neck surgery is crucial to avoid postoperative hypoparathyroidism. There are no existing guidelines for intraoperative PG identification, and the current approach relies heavily on the experience of the operating surgeon. A technique that accurately and rapidly identifies PGs would represent a useful intraoperative adjunct.

AREAS COVERED

This review aims to assess common dye and fluorescence-based PG imaging techniques and examine their utility for intraoperative PG identification. A literature search of published data on methylene blue (MB), indocyanine green (ICG) angiography, near-infrared autofluorescence (NIRAF), and the PGs between 1971 and 2020 was conducted on PubMed.

EXPERT OPINION

NIRAF and near-infrared (NIR) parathyroid angiography have emerged as promising and reliable techniques for intraoperative PG identification. NIRAF may aid with real-time identification of both normal and diseased PGs and reduce the risk of postoperative complications such as hypocalcemia. Further large prospective multicenter studies should be conducted in thyroid and parathyroid surgical patient populations to confirm the clinical efficacy of these intraoperative NIR-based PG detection techniques.

A Prospective Pilot Study of Vascular Assessment of the Upper Extremity With Laser Angiography

Background: Our goal was to investigate patients' upper extremity tissue perfusion changes using an indocyanine green laser angiography imaging system for various pathologic states and interventions. Methods: This prospective observational study used Spy Elite/LUNA laser angiography to evaluate perfusion in patients with upper extremity vascular compromise. All patients had Spy Elite/LUNA imaging as well as clinical and handheld Doppler examinations preintervention, intraoperatively, if applicable, and at 1 week, 2 weeks, and 2 months postintervention. For each laser angiography scan, we used an unaffected control area with uninjured skin to quantitatively compare with the dysvascular tissues. Results: Twelve patients, 7 men and 5 women, had a total of 16 upper extremities evaluated. The mean age was 53 years, and half of the patients entering the study were smokers. Etiologies of vascular compromise were trauma, primary and secondary vasospastic disease, scleroderma, and intravascular drug injection. Interventions included surgical repair/reconstruction, botulinum toxin injections, and/or systemic medications. Improvement in perfusion following intervention was statistically significant, demonstrated by an increase in Spy Elite/LUNA quantitative score postintervention compared with preintervention scans. Adjusting for other variables, such as smoking and handheld Doppler signal status, demonstrated an independent statistically significant increase in Spy Elite/LUNA scores at all postintervention time points compared with preintervention scores. Laser angiography was able to confirm adequate vascular status, with ultimate tissue survival, in some cases when Doppler signals were not initially present. Conclusions: Laser angiography provided objective data to document improved upper extremity tissue perfusion following various interventions.

Intraoperative Indocyanine Green (ICG) Angiography for the Identification of the Parathyroid Glands: Current Evidence and Future Perspectives

BACKGROUND/AIM

Recently, indocyanine green (ICG) fluorescence imaging has been used for the identification of the parathyroid glands (PG) during thyroid and parathyroid surgery. However, an overall consensus on the optimal technique, the dosage, the timing of the ICG administration and finally its interpretation and clinical usefulness is still lacking evidence. The aim of this review is to investigate the use of ICG angiography during thyroidectomy and/or parathyroidectomy for identification as well as for the perfusion integrity of the parathyroid glands.

MATERIALS AND METHODS

The PubMed database was systematically searched for publications regarding intraoperative ICG imaging in patients that undergo thyroidectomy or parathyroidectomy.

RESULTS

Eighteen publications reporting on 612 patients, namely 71 parathyroidectomy and 541 thyroidectomy patients met the inclusion criteria. Eleven publications reported the use of ICG angiography for the identification of the parathyroid glands during thyroidectomy and seven during parathyroidectomy for primary and secondary hyperparathyroidism.

CONCLUSION

ICG fluorescence imaging is a simple, fast and reproducible method capable of intraoperatively visualizing and assessing the function of parathyroid glands, and can, therefore, assist surgeons in their decision-making. Despite all this, ICG fluorescence imaging technique for PG detection still lacks standardization and further studies are needed to establish its clinical utility.

Intraoperative fluorescence perfusion assessment should be corrected by a measured subject-specific arterial input function

SIGNIFICANCE

The effects of varying the indocyanine green injection dose, injection rate, physiologic dispersion of dye, and intravenous tubing volume propagate into the shape and magnitude of the arterial input function (AIF) during intraoperative fluorescence perfusion assessment, thereby altering the observed kinetics of the fluorescence images in vivo.

AIM

Numerical simulations are used to demonstrate the effect of AIF on metrics derived from tissue concentration curves such as peak fluorescence, time-to-peak (TTP), and egress slope.

APPROACH

Forward models of tissue concentration were produced by convolving simulated AIFs with the adiabatic approximation to the tissue homogeneity model using input parameters representing six different tissue examples (normal brain, glioma, normal skin, ischemic skin, normal bone, and osteonecrosis).

RESULTS

The results show that AIF perturbations result in variations in estimates of total intensity of up to 80% and TTP error of up to 200%, with the errors more dominant in brain, less in skin, and less in bone. Interestingly, error in ingress slope was as high as 60% across all tissue types. These are key observable parameters used in fluorescence imaging either implicitly by viewing the image or explicitly through intensity fitting algorithms. Correcting by deconvolving the image with a measured subject-specific AIF provides an intuitive means of visualizing the data while also removing the source of variance and allowing intra- and intersubject comparisons.

CONCLUSIONS

These results suggest that intraoperative fluorescence perfusion assessment should be corrected by patient-specific AIFs measured by pulse dye densitometry.

Assessment of foot perfusion: Overview of modalities, review of evidence, and identification of evidence gaps

Patients with critical limb ischemia have nonhealing wounds and/or ischemic rest pain and are at high risk for amputation and mortality. Accurate evaluation of foot perfusion should help avoid unnecessary amputation, guide revascularization strategies, and offer efficient surveillance for patency. Our aim is to review current modalities of assessing foot perfusion in the context of the practical clinical management of patients with critical limb ischemia.

A systematic review of the use of near-infrared fluorescence imaging in patients with peripheral artery disease

OBJECTIVE

In the diagnosis of peripheral artery disease (PAD), the ankle-brachial index plays an important role. However, results of the ankle-brachial index are unreliable in patients with severe media sclerosis. Near-infrared (NIR) fluorescence imaging using indocyanine green (ICG) can provide information about tissue perfusion and has already been studied in oncologic, reconstructive, and cardiac surgery. For patients with PAD, this technique might give insight into skin perfusion and thereby guide treatment. We performed a systematic review of the literature on the use of NIR fluorescence imaging in patients with PAD.

METHODS

PubMed, MEDLINE, Embase, and Cochrane were searched for articles and abstracts on the application of NIR fluorescence imaging using ICG as fluorescent dye in patients with PAD. Our search strategy combined the terms "fluorescence," "ICG," or synonyms and "peripheral artery disease" or synonyms. The extracted data included fluorescence parameters and test characteristics for diagnosis of PAD.

RESULTS

Twenty-three articles were found eligible for this review using 18 different parameters for evaluation of the fluorescence signal intensity. NIR fluorescence imaging was used for four main indications: diagnosis, quality control in revascularization, guidance in amputation surgery, and visualization of vascular structures. For the diagnosis of PAD, NIR fluorescence imaging yields a sensitivity ranging from 67% to 100% and a specificity varying between 72% and 100%. Significant increases in multiple fluorescence parameters were found in comparing patients before and after revascularization.

CONCLUSIONS

NIR fluorescence imaging can be used for several indications in patients with PAD. NIR fluorescence imaging seems promising in diagnosis of PAD and guidance of surgeons in treatment, especially in patients in whom current diagnostic methods are not applicable. Further standardization is needed to reliably use this modality in patients with PAD.

New Advances of ICG Angiography in Parathyroid Identification

Objective:

For surgeons, locating parathyroid in thyroidectomy and parathyroidectomy is critical since parathyroid plays an important role in calcium balance. The fluorescence of parathyroid has already been found by researchers and the angiography equipment detecting the fluorescence of parathyroid with indocyanine green has been widely applied. Using the indocyanine green angiography and looking at the actual fluorescence of in vivo and in vitro tissues, it was possible to identify thyroid, parathyroid, lymph nodes and fat tissues during the surgical procedure. This mini-review aims to present the application of indocyanine green angiography in parathyroid detection and discusses the safety of this method.

Methods:

The relevant data were searched by using the keywords “Indocyanine green,” “Parathyroid,” and “Identification” and “Protection” in “Pubmed,” “Web of Science” and “China Knowledge Resource Integrated databases”, and a manual search was done to acquire peer-reviewed articles and reports about indocyanine green.

Results:

Indocyanine green dye along with the intraoperative fluorescence imaging system is safe in detecting parathyroid and predicting postoperative hypoparathyroidism.

Conclusion:

The conclusion suggests that indocyanine green angiography is a safe, effective and easy way to detect parathyroid glands. The conclusion will be of interest to surgeons regarding thyroidectomy and parathyroidectomy.

Research on indocyanine green angiography for predicting postoperative hypoparathyroidism

BACKGROUND

It may be critical to locate the parathyroid for surgeons during thyroidectomy or parathyroidectomy due to the significant function of the parathyroid in calcium balance. According to recent reports, the intrinsic fluorescence of the parathyroid has been found. There is some evidence supporting that new equipment can detect fluorescence via imaging technology. In this study, a newly invented intraoperative fluorescence imaging system and indocyanine green dye were applied to detect the parathyroid glands and evaluate the vascularization of the parathyroid. The report is as follows.

METHODS

From 1 May to 8 August 2018, 26 patients underwent total thyroidectomy in Zhuhai People's Hospital and were recruited into our research. All identified parathyroid glands were scored visually from grade 0 to grade 2 according to the vascularity of the parathyroid before ICG angiography was performed. After ICG angiography, parathyroid glands were scored from score 0 to score 2 according to the FI.

RESULTS

Visual scores were significantly higher than ICG angiography scores. In the 22 patients with at least one parathyroid gland with an ICG score of 2, postoperative PTH levels were in the normal range. In the four patients with no parathyroid gland with an ICG score of 2, two of them developed transient hypoparathyroidism, with recovery on POD 7 for the first patient and after 3 months for the second one.

CONCLUSION

This study has identified that the fluorescence imaging system applied with indocyanine green is a safe, easy and effective method to protect the parathyroid and predict postoperative hypoparathyroidism. Registration number: ChiCTR1800016864.

Application of a Fluorescence Imaging System with Indocyanine Green to Protect the Parathyroid Gland Intraoperatively and to Predict Postoperative Parathyroidism

INTRODUCTION

Identifying the parathyroid gland during surgery may be difficult for surgeons. It is critical for them to be able to locate it during thyroidectomy or parathyroidectomy because of the significant function of the parathyroid in the calcium balance. According to recent reports, intrinsic fluorescence of the parathyroid has been found. There is some evidence to suggest that new equipment can detect the fluorescence via imaging technology. In this study, a newly invented intraoperative fluorescence imaging system and indocyanine green (ICG) dye were applied to detect the parathyroid glands and evaluate the vascularization of the parathyroid.

METHODS

From 1 May to 8 August 2018, 26 patients underwent total thyroidectomy in Zhuhai People's Hospital. These 26 subjects were recruited in our research. All identified parathyroid glands were scored visually from grade 0 to grade 2 according to the vascularity of the parathyroid before ICG angiography was performed. After ICG angiography, the parathyroid glands were scored from 0 to 2 according to the fluorescence intensity (FI).

RESULTS

Visual scores were significantly higher than ICG angiography scores. In the 22 patients with at least one parathyroid gland with an ICG score of 2, postoperative parathyroidism (PTH) levels were in the normal range. Of the four patients with no parathyroid gland with an ICG score of 2, two developed transient hypoparathyroidism, with recovery on postoperative day (POD) 7 for the first patient and after 3 months for the second.

CONCLUSION

This study has shown that a fluorescence imaging system applied with indocyanine green is a safe, easy and effective method to protect the parathyroid and predict postoperative parathyroidism.

TRIAL REGISTRATION

Chinese Clinical Trial Registry no. ChiCTR1800016864.

Intraoperative Imaging and Image Fusion for Venous Interventions

Advanced imaging for intraoperative evaluation of venous pathologies has played an increasingly significant role in this era of evolving minimally invasive surgical and interventional therapies. The evolution of dedicated venous stents and other novel interventional devices has mandated the need for advanced imaging tools to optimize safe and accurate device deployment. Most venous interventions are typically performed using a combination of standard 2-dimensional (2D) fluoroscopy, digital-subtraction angiography, and intravascular ultrasound imaging techniques. Latest generation computer tomography (CT) and magnetic resonance imaging (MRI) scanners have been shown to provide high-resolution 3D and 4D information about venous vasculature. In addition to morphological imaging, novel MRI techniques such as 3D time-resolved MR venography and 4D flow sequences can provide quantitative information and help visualize intricate flow patterns to better understand complex venous pathologies. Moreover, the high-fidelity information from multiple imaging techniques can be integrated using image fusion to overcome the limitations of current intraoperative imaging techniques. For example, the limitations of standard 2D fluoroscopy and luminal angiography can be compensated for by perivascular and soft-tissue information from MRI during complex venous interventions using image fusion techniques. Intraoperative dynamic evaluation of devices such as venous stents and real-time understanding of changes in flow patterns during venous interventions may be routinely available in future interventional suites with integrated multimodality CT or MR imaging capabilities. The purpose of this review is to discuss the outlook for intraoperative imaging and multimodality image fusion techniques and highlight their value during complex venous interventions.

Significance of the Lateral Thoracic Artery in Pectoralis Major Musculocutaneous Flap Reconstruction: Quantitative Assessment of Blood Circulation Using Indocyanine Green Angiography

Free tissue transfer is the preferred reconstruction option in most major head and neck reconstructions. The pectoralis major muscle musculocutaneous (PMMC) flap is commonly used in salvage of necrotic free flaps and is the first choice for patients who are not candidates for free flaps. The lateral thoracic artery (LTA), which is thought to contribute to blood perfusion of the inferior and lateral mammary area, is not preserved in a conventionally harvested PMMC flap. With regard to blood supply, it has been suggested that the LTA should be preserved, in addition to the pectoral branch of the thoracoacromial artery, when a skin island is designed in the lower chest to attain a pedicle length sufficient for head and neck reconstruction. However, an effect on hemodynamic improvement using the LTA has not been shown quantitatively. In this study, we examined 8 patients with oral cancer who underwent reconstruction procedures with a bipedicle PMMC flap that included the LTA, in addition to the thoracoacromial artery. Intraoperative indocyanine green angiography was performed to examine circulation to the PMMC flap with or without LTA clamping after harvesting. After image processing, data were analyzed using a new quantitative perfusion assessment system with parameters that we recently established for assessment of peripheral arterial disease of the lower limbs. All patients had good clinical courses with whole-flap survival, no vascular insufficiency of the skin island, and no fistula formation. Intraoperative indocyanine green angiography showed an increased inflow rate into the skin island in an LTA-declamped condition in all cases, implying that the preserved LTA increased the blood supply to skin islands in the pectoralis major muscle. We conclude that preserving the LTA in a PMMC flap can increase blood perfusion and stabilize the vascularity of the flap, making the reconstruction more effective and reliable than with use of a conventionally harvested flap. Therefore, it is worthwhile to preserve the LTA as a major contributor to a lateral and distal PMMC flap.

The Ability of Fluorescence Angiography to Detect Local Ischemia in Patients With Heel Ulceration

Heel ulcerations are a significant burden of care in both hospital and long-term care settings. The presence of peripheral arterial disease as a contributing factor to delayed healing is often not recognized, resulting in prolonged healing and high patient morbidity and mortality. Formal vascular evaluation and intervention is often not performed as these patients can have palpable pedal pulses while having localized ischemia of the heel. As routine noninvasive vascular studies can be affected by medial calcinosis and collateralization and do not specifically assess tissue perfusion to the heel, a false sense of security of adequate perfusion for healing can result. Indocyanine green fluorescence angiography (ICGFA) allows for real-time visualization and objective assessment of site specific tissue perfusion not limited by the factors that can make routine noninvasive vascular studies unreliable or unobtainable. A retrospective medical record review of a subset of patients with chronic heel ulceration from a prospective institutional review board-approved study in which serial ICGFA was performed during their treatment course was performed. ICGFA was able to identify local heel ischemia and expedite vascular intervention. ICGFA should be considered as an additional vascular study in patients presenting with chronic, nonhealing heel ulcerations.

LEVELS OF EVIDENCE

Level IV: Diagnostic, Case series.

Is non-invasive indocyanine-green angiography a useful adjunct for the debridement of infected sternal wounds?

Laser-assisted indocyanine-green imaging (ICG) has a wide range of surgical applications, and has been used in reconstructive surgery to aid in assessing the viability of free tissue transfers and to help predict poor tissue perfusion. However, its indications for use is limited to assessing free flap tissue perfusion, coronary artery perfusion during coronary artery bypass (CABG), and tissue perfusion in diabetic foot ulcers, to name a few. This system has been proven to be a safe, reliable adjunctive modality to assess microvascular compromise or poor perfusion peri-operatively, which could minimize skin necrosis and other post-operative complications (Further et al., 2013).¹ The ability to objectively assess tissue perfusion has led to improved post-operative outcomes in breast, abdominal wall, colorectal, and cardiac surgery. To date, no studies have reviewed the use of ICG in delineating devitalized bone during sternal wound debridement after cardiac surgery. At our institution, we have encountered a cohort of patients with post-cardiac surgery sternal wound infections who have required debridement of infected and devitalized bone. We propose that SPY technology aids in delineating this devitalized bone, and may aid in the timing muscle flap coverage. In this paper, we will demonstrate two cases of patients who had post-operative sternal wound infections after undergoing cardiac surgery for which ICG was used to demarcate debridement zones and subsequent flap coverage. In these cases, ICG allowed for efficient and reliable intraoperative evaluation of bony perfusion and has aided in early adequate debridement and flap coverage.

Assessment of lower extremity ischemia using smartphone thermographic imaging

Conventional diagnostic modalities for assessing arterial circulation or tissue perfusion include blood pressure measurement, ultrasound evaluation, and contrast-based angiographic assessment. An infrared thermal camera can detect infrared radiation energy from the human body, which generates a thermographic image to allow tissue perfusion analysis. We describe a smartphone-based miniature thermal imaging system that can be used as an adjunctive imaging modality to assess tissue perfusion. This smartphone-based camera device is noninvasive, simple to use, and cost-effective in assessing patients with lower extremity tissue perfusion. Assessment of patients with lower extremity arterial ischemia can be performed by a variety of diagnostic modalities, including ankle-brachial index, absolute systolic ankle or toe pressure, transcutaneous oximetry, arterial Doppler waveform, arterial duplex ultrasound, computed tomography scan, arterial angiography, and thermal imaging. We herein describe a noninvasive imaging modality using smartphone-based infrared thermography.

Vascular assessment of wound healing: a clinical review

Although macrovascular screening of patients with chronic wounds, particularly in the lower extremities, is accepted as part of clinical practice guidelines, microvascular investigation is less commonly used for a variety of reasons. This can be an issue because most patients with macrovascular disease also develop concomitant microvascular dysfunction. Part of the reason for less comprehensive microvascular screening has been the lack of suitable imaging techniques that can quantify microvascular dysfunction in connection with non-healing chronic wounds. This is changing with the introduction of fluorescence microangiography. The objective of this review is to examine macro- and microvascular disease, the strengths and limitations of the approaches used and to highlight the importance of microvascular angiography in the context of wound healing.

Utility of Indocyanine Green Angiography in Arterial Selection during Free Flap Harvest in Patients with Severe Peripheral Vascular Disease

Indocyanine green angiography (SPY) was used to guide arterial selection for an anterolateral thigh free flap in the setting of severe peripheral vascular disease. SPY technology serves as a novel and sensitive intraoperative tool to predict decreased tissue perfusion from vessel sacrifice for flap harvest. Change in SPY time parameters measuring superficial blood flow distal to the donor site while temporarily intraoperatively clamping different possible arterial pedicles can optimize free flap design to avoid iatrogenic critical limb ischemia.

Review of near-infrared methods for wound assessment

Wound management is a challenging and costly problem that is growing in importance as people are living longer. Instrumental methods are increasingly being relied upon to provide objective measures of wound assessment to help guide management. Technologies that employ near-infrared (NIR) light form a prominent contingent among the existing and emerging technologies. We review some of these technologies. Some are already established, such as indocyanine green fluorescence angiography, while we also speculate on others that have the potential to be clinically relevant to wound monitoring and assessment. These various NIR-based technologies address clinical wound management needs along the entire healing trajectory of a wound.

Intraoperative indocyanine green angiography for the objective measurement of blood flow

PURPOSE

Intraoperative assessment of tissue perfusion is important to predict wound healing or improvement of symptoms in patients with peripheral arterial disease (PAD) or vascular trauma. There is no widely accepted standard for intraoperative measurement of tissue perfusion. Here, we report the use of indocyanine green (ICG)-based angiography to determine the blood flow in patients with PAD and vascular trauma.

METHODS

The SPY fluorescent imaging system was utilized. A dose of 3-5 mL of ICG (2.5 mg/mL) was injected intravenously followed by a 10 mL normal saline flush. The SPY imaging system was used to quantitatively assess perfusion. During the study period, the SPY imaging system was applied in 4 patients with PAD and one patient with vascular trauma.

RESULTS

In 3 patients with PAD associated with an ischemic wound, complete wound healing was achieved with the indication of viable tissue by the SPY system. In one patient with severe claudication in both lower extremities, the ICG angiography was used to determine the increased blood flow after revascularization. In the case of vascular trauma, this imaging system enabled the delineation of viability of the injured tissue.

CONCLUSION

ICG angiography can determine the surface tissue viability in PAD patients. In cases of severe vascular trauma,the SPY system can be used to determine tissue perfusion. Further study is warranted to define the definite utility of this technology to assess perfusion, response to revascularization, and potentially, to predict the likelihood of wound healing.

Assessment of foot perfusion in patients with a diabetic foot ulcer

Assessment of foot perfusion is a vital step in the management of patients with diabetic foot ulceration, in order to understand the risk of amputation and likelihood of wound healing. Underlying peripheral artery disease is a common finding in patients with foot ulceration and is associated with poor outcomes. Assessment of foot perfusion should therefore focus on identifying the presence of peripheral artery disease and to subsequently estimate the effect this may have on wound healing. Assessment of perfusion can be difficult because of the often complex, diffuse and distal nature of peripheral artery disease in patients with diabetes, as well as poor collateralisation and heavy vascular calcification. Conventional methods of assessing tissue perfusion in the peripheral circulation may be unreliable in patients with diabetes, and it may therefore be difficult to determine the extent to which poor perfusion contributes to foot ulceration. Anatomical data obtained on cross-sectional imaging is important but must be combined with measurements of tissue perfusion (such as transcutaneous oxygen tension) in order to understand the global and regional perfusion deficit present in a patient with diabetic foot ulceration. Ankle-brachial pressure index is routinely used to screen for peripheral artery disease, but its use in patients with diabetes is limited in the presence of neuropathy and medial arterial calcification. Toe pressure index may be more useful because of the relative sparing of pedal arteries from medial calcification but may not always be possible in patients with ulceration. Fluorescence angiography is a non-invasive technique that can provide rapid quantitative information about regional tissue perfusion; capillaroscopy, iontophoresis and hyperspectral imaging may also be useful in assessing physiological perfusion but are not widely available. There may be a future role for specialized perfusion imaging of these patients, including magnetic resonance imaging techniques, single-photon emission computed tomography and PET-based molecular imaging; however, these novel techniques require further validation and are unlikely to become standard practice in the near future.

Utility of Indocyanine Green Fluorescence Imaging for Intraoperative Localization in Reoperative Parathyroid Surgery

Background. Due to the variations in anatomic location, the identification of parathyroid glands may be challenging. Although there have been advances in preoperative imaging modalities, there is still a need for an accurate intraoperative guidance. Indocyanine green (ICG) is a new agent that has been used for intraoperative fluorescence imaging in a number of general surgical procedures. Its utility for parathyroid localization in humans has not been reported in the literature. Results. We report 3 patients who underwent reoperative neck surgery for primary hyperparathyroidism. Using a video-assisted technique with intraoperative ICG fluorescence imaging, the parathyroid glands were recognized and removed successfully in all cases. Surrounding soft tissue structures remained nonfluorescent, and could be distinguished from the parathyroid glands. Conclusions. This report suggests a potential utility of ICG imaging in intraoperative localization of parathyroid glands in reoperative neck surgery. Future work is necessary to assess its benefit for first-time parathyroid surgery.

The First-in-Man "Si Se Puede" Study for the use of micro-oxygen sensors (MOXYs) to determine dynamic relative oxygen indices in the feet of patients with limb-threatening ischemia during endovascular therapy

OBJECTIVE

Patients with limb-threatening ischemia exhibit uneven patterns of perfusion in the foot, which makes it challenging to determine adequate topographic perfusion by angiography alone. This study assessed the feasibility of reporting dynamic relative oxygen indices and tissue oxygen concentration from multiple locations on the foot during endovascular therapy using a novel micro-oxygen sensor (MOXY; PROFUSA, Inc, South San Francisco, Calif) approach.

METHODS

A prospective, 28-day, single-arm, observational study was performed in 10 patients who underwent endovascular therapy for limb-threatening ischemia. At least 24 hours before therapy, four microsensors were injected in each patient (one in the arm, three in the treated foot). The optical signal from the microsensors corresponded to tissue oxygen concentration. A custom detector on the surface of the skin was used to continuously and noninvasively measure the signals from the microsensors. The ability to locate and read the signal from each injected microsensor was characterized. Oxygen data from the microsensors were collected throughout the revascularization procedure. The timing of therapy deployment was recorded during the procedure to assess its relationship with the microsensor oxygen data. Oxygen data collection and clinical evaluation were performed immediately postoperatively as well as postoperatively on days 7, 14, 21, and 28.

RESULTS

The study enrolled 10 patients (50% male) with ischemia (30% Rutherford class 4, 70% Rutherford class 5). Patients were a mean age of 70.7 years (range, 46-90 years), and all were Hispanic of varying origin. Microsensors were successfully read 206 of 212 times (97.2%) in all patients during the course of the study. Microsensors were compatible with intraoperative use in the interventional suite and postoperatively in an office setting. In nine of 10 revascularization procedures, at least one of the three MOXYs showed an immediate change in the dynamic relative oxygen index, correlating to deployed therapy. Moreover, there was a statistically significant increase in the concentration of oxygen in the foot in preoperative levels compared with postoperative levels. No adverse events occurred related to the microsensor materials.

CONCLUSIONS

This MOXY approach appears to be safe when implanted in patients with limb-threatening ischemia undergoing endovascular recanalization and is effective in reporting local tissue oxygen concentrations over a course of 28 days. Further testing is needed to determine its potential effect on clinical decision making, both acutely on-table and chronically as a surveillance modality, which ultimately can lead to improved healing and limb salvage.

Intraoperative angiography provides objective assessment of skin perfusion in complex knee reconstruction

BACKGROUND

Wound necrosis is a potentially devastating complication of complex knee reconstruction. Laser-assisted indocyanine green angiography (LA-ICGA) is a technology that has been described in the plastic surgery literature to provide an objective assessment of skin perfusion in the operating room. This novel technology uses a plasma protein bound dye (ICG) and a camera unit that is calibrated to view the frequency emitted by the dye. The intention of this technology is to offer real-time visualization of blood flow to skin and soft tissue in a way that might help surgeons make decisions about closure or coverage of a surgical site based on blood flow, potentially avoiding soft tissue reconstruction while preventing skin necrosis or wound breakdown after primary closures, but its efficacy is untested in the setting of complex TKA.

QUESTIONS/PURPOSES

The purpose of this study was to evaluate perfusion borders and tension ischemia in a series of complex knee reconstructions to guide optimal wound management.

METHODS

Beginning in mid-2011, an LA-ICGA system was used to evaluate soft tissue viability in knee reconstruction procedures that were considered high risk for wound complications. Seven patients undergoing complex primary or revision TKA from 2011 to 2013 were included. These patients were chosen as a convenience sample of knee reconstruction procedures for which we obtained consultation with the plastic surgery service. The perfusion of skin and soft tissue coverage was evaluated intraoperatively for all patients with the LA-ICGA system, and the information was used to guide wound management. Followup was at a mean of 9 months (range, 6-17 months), no patients were lost to followup, and the main study endpoint was uneventful healing of the surgical incision.

RESULTS

All seven closures went on to heal without necrosis. One patient, however, was subsequently revised for a deep periprosthetic infection 4 months after their knee reconstruction and underwent flap coverage at the time of that revision.

CONCLUSIONS

Implementation of LA-ICGA provides an objective intraoperative assessment of soft tissue perfusion. This technology may help guide the surgeon's decisions about wound closure in real-time to accommodate the perfusion challenges unique to each patient. Specifically, patients with medical risk factors for poor perfusion or wound healing (such as diabetes, peripheral vascular disease, tobacco use, corticosteroid therapy, infection) or anatomical/surgical risk factors (ie, previous surgery about the reconstruction site, trauma wounds, or reconstruction of severe deformity) may benefit from objective intraoperative information regarding perfusion of the wound site. Furthermore, LA-ICGA could be used to prospectively evaluate the physiologic impact of different wound closure techniques.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Detection of Peripheral Arterial Disease Within the Foot Using Vascular Optical Tomographic Imaging: A Clinical Pilot Study

OBJECTIVE

Vascular optical tomographic imaging (VOTI) is a novel imaging modality that is capable of detecting hemoglobin concentrations in tissue. VOTI is non-invasive, non-ionizing and does not require contrast injection. This technology was applied to the diagnosis of peripheral arterial disease (PAD) within lower extremities of diabetic patients with calcified arteries. This could be of substantial benefit as these patients suffer from comorbidities such as arterial incompressibility, which complicates diagnosis and monitoring.

METHODS

Forty individuals (10 non-diabetic patients with PAD, 10 diabetic patients with PAD, and 20 healthy volunteers) were enrolled in a diagnostic pilot study using the VOTI system. The patients were imaged during at high pressure cuff occlusion.

RESULTS

The VOTI system was capable of quantifying the blood volume changes within the foot during the thigh cuff occlusion and outputting diagnostic parameters, such as change in hemoglobin concentration, enabling the assessment of foot perfusion. This study resulted in a statistically significant difference between the healthy cohort and both the non-diabetic and the diabetic PAD cohorts (p = .006, p = .006). Receiver operating characteristic (ROC) curve analysis showed that PAD diagnosis could be made with over 80% sensitivity or specificity depending on the characteristic cutoff point. In addition, VOTI was capable of providing the locations of under-perfused regions within the foot and evaluating the severity of arterial disease, even within diabetic patients with calcified arteries, who are traditionally difficult to diagnose.

CONCLUSION

VOTI can effectively diagnose PAD independently of arterial compressibility, making it very useful for assessing vascular disease in diabetic patients.

Contemporary assessment of foot perfusion in patients with critical limb ischemia

Significant progress in limb salvage for patients with peripheral arterial disease and critical limb ischemia has occurred in the past 2 decades. Improved patient outcomes have resulted from increased knowledge and understanding of the disease processes, as well as efforts to improve revascularization techniques and enhance patient care after open and endovascular procedures. An imaging modality that is noninvasive, fast, and safe would be a useful tool for clinicians in assessing lower-extremity perfusion when planning interventions. Among the current and emerging regional perfusion imaging modalities are transcutaneous oxygen monitoring, hyperspectral imaging, indocyanine green dye-based fluorescent angiography, nuclear diagnostic imaging, and laser Doppler. These tests endeavor to delineate regional foot perfusion to guide directed revascularization therapy in patients with critical limb ischemia and foot ulceration.

A heads-up display for diabetic limb salvage surgery: a view through the google looking glass

Although the use of augmented reality has been well described over the past several years, available devices suffer from high cost, an uncomfortable form factor, suboptimal battery life, and lack an app-based developer ecosystem. This article describes the potential use of a novel, consumer-based, wearable device to assist surgeons in real time during limb preservation surgery and clinical consultation. Using routine intraoperative, clinical, and educational case examples, we describe the use of a wearable augmented reality device (Google Glass; Google, Mountain View, CA). The device facilitated hands-free, rapid communication, documentation, and consultation. An eyeglass-mounted screen form factor has the potential to improve communication, safety, and efficiency of intraoperative and clinical care. We believe this represents a natural progression toward union of medical devices with consumer technology.

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.

Towards whole-body fluorescence imaging in humans

Dynamic near-infrared fluorescence (DNIF) whole-body imaging of small animals has become a popular tool in experimental biomedical research. In humans, however, the field of view has been limited to body parts, such as rheumatoid hands, diabetic feet or sentinel lymph nodes. Here we present a new whole-body DNIF-system suitable for adult subjects. We explored whether this system (i) allows dynamic whole-body fluorescence imaging and (ii) can detect modulations in skin perfusion. The non-specific fluorescent probe indocyanine green (ICG) was injected intravenously into two subjects, and fluorescence images were obtained at 5 Hz. The in- and out-flow kinetics of ICG have been shown to correlate with tissue perfusion. To validate the system, skin perfusion was modulated by warming and cooling distinct areas on the chest and the abdomen. Movies of fluorescence images show a bolus passage first in the face, then in the chest, abdomen and finally in the periphery (~10, 15, 20 and 30 seconds, respectively). When skin perfusion is augmented by warming, bolus arrives about 5 seconds earlier than when the skin is cooled and perfusion decreased. Calculating bolus arrival times and spatial fitting of basis time courses extracted from different regions of interest allowed a mapping of local differences in subcutaneous skin perfusion. This experiment is the first to demonstrate the feasibility of whole-body dynamic fluorescence imaging in humans. Since the whole-body approach demonstrates sensitivity to circumscribed alterations in skinperfusion, it may be used to target autonomous changes in polyneuropathy and to screen for peripheral vascular diseases.

Quantitative evaluation of the outcomes of revascularization procedures for peripheral arterial disease using indocyanine green angiography

OBJECTIVES

We performed indocyanine green angiography (ICGA) in patients with peripheral arterial disease (PAD), and established a method for the quantitative measurement of appropriate parameters to assess peripheral perfusion and the applicability of ICGA tests.

METHODS

Twenty-one patients with PAD underwent revascularization procedures with pre- and postinterventional ICGA tests. The ICGA parameters, which included the magnitude of intensity of indocyanine green, the time to maximum intensity, and the time from fluorescence onset to half the maximum intensity (T1/2) were compared with the ankle-brachial pressure index, toe -brachial pressure index, and toe pressure. We evaluated these parameters for regions of interest (ROIs).

RESULTS

T1/2 was the strongest parameter among all parameters of the ICGA tests. ROI 3, which included the distal region of the first metatarsal bone, correlated more significantly with the traditional measurements than the other ROIs. A value of T1/2 >20 seconds for ROI 3 was significantly correlated with a toe pressure of <50 mmHg (sensitivity: 0.77, specificity: 0.80).

CONCLUSIONS

ICGA can be used to assess peripheral tissue perfusion. By measuring the value of T1/2 in ROI 3, ICGA tests can be used to evaluate the outcomes of revascularization procedures.

Fluorescence imaging in surgery

Although the modern surgical era is highlighted by multiple technological advances and innovations, one area that has remained constant is the dependence of the surgeon's vision on white-light reflectance. This renders different body tissues in a limited palette of various shades of pink and red, thereby limiting the visual contrast available to the operating surgeon. Healthy tissue, anatomic variations, and diseased states are seen as slight discolorations relative to each other and differences are inherently limited in dynamic range. In the upcoming years, surgery will undergo a paradigm shift with the use of targeted fluorescence imaging probes aimed at augmenting the surgical armamentarium by expanding the "visible" spectrum available to surgeons. Such fluorescent "smart probes" will provide real-time, intraoperative, pseudo-color, high-contrast delineation of both normal and pathologic tissues. Fluorescent surgical molecular guidance promises another major leap forward to improve patient safety and clinical outcomes, and to reduce overall healthcare costs. This review provides an overview of current and future surgical applications of fluorescence imaging in diseased and nondiseased tissues and focus on the innovative fields of image processing and instrumentation.