Quantification of indocyanine green near-infrared fluorescence bowel perfusion assessment in colorectal surgery

BACKGROUND

Indocyanine green near-infrared fluorescence bowel perfusion assessment has shown its potential benefit in preventing anastomotic leakage. However, the surgeon's subjective visual interpretation of the fluorescence signal limits the validity and reproducibility of the technique. Therefore, this study aimed to identify objective quantified bowel perfusion patterns in patients undergoing colorectal surgery using a standardized imaging protocol.

METHOD

A standardized fluorescence video was recorded. Postoperatively, the fluorescence videos were quantified by drawing contiguous region of interests (ROIs) on the bowel. For each ROI, a time-intensity curve was plotted from which perfusion parameters (n = 10) were derived and analyzed. Furthermore, the inter-observer agreement of the surgeon's subjective interpretation of the fluorescence signal was assessed.

RESULTS

Twenty patients who underwent colorectal surgery were included in the study. Based on the quantified time-intensity curves, three different perfusion patterns were identified. Similar for both the ileum and colon, perfusion pattern 1 had a steep inflow that reached its peak fluorescence intensity rapidly, followed by a steep outflow. Perfusion pattern 2 had a relatively flat outflow slope immediately followed by its plateau phase. Perfusion pattern 3 only reached its peak fluorescence intensity after 3 min with a slow inflow gradient preceding it. The inter-observer agreement was poor-moderate (Intraclass Correlation Coefficient (ICC): 0.378, 95% CI 0.210-0.579).

CONCLUSION

This study showed that quantification of bowel perfusion is a feasible method to differentiate between different perfusion patterns. In addition, the poor-moderate inter-observer agreement of the subjective interpretation of the fluorescence signal between surgeons emphasizes the need for objective quantification.

Intraoperative molecular imaging of colorectal lung metastases with SGM-101: a feasibility study

PURPOSE

Metastasectomy is a common treatment option for patients with colorectal lung metastases (CLM). Challenges exist with margin assessment and identification of small nodules, especially during minimally invasive surgery. Intraoperative fluorescence imaging has the potential to overcome these challenges. The aim of this study was to assess feasibility of targeting CLM with the carcinoembryonic antigen (CEA) specific fluorescent tracer SGM-101.

METHODS

This was a prospective, open-label feasibility study. The primary outcome was the number of CLM that showed a true positive fluorescence signal with SGM-101. Fluorescence positive signal was defined as a signal-to-background ratio (SBR) ≥ 1.5. A secondary endpoint was the CEA expression in the colorectal lung metastases, assessed with the immunohistochemistry, and scored by the total immunostaining score.

RESULTS

Thirteen patients were included in this study. Positive fluorescence signal with in vivo, back table, and closed-field bread loaf imaging was observed in 31%, 45%, and 94% of the tumors respectively. Median SBRs for the three imaging modalities were 1.00 (IQR: 1.00-1.53), 1.45 (IQR: 1.00-1.89), and 4.81 (IQR: 2.70-7.41). All tumor lesions had a maximum total immunostaining score for CEA expression of 12/12.

CONCLUSION

This study demonstrated the potential of fluorescence imaging of CLM with SGM-101. CEA expression was observed in all tumors, and closed-field imaging showed excellent CEA specific targeting of the tracer to the tumor nodules. The full potential of SGM-101 for in vivo detection of the tracer can be achieved with improved minimal invasive imaging systems and optimal patient selection.

TRIAL REGISTRATION

The study was registered in ClinicalTrial.gov under identifier NCT04737213 at February 2021.

Robot-assisted thoracic surgery for stages IIB-IVA non-small cell lung cancer: retrospective study of feasibility and outcome

Robot-assisted thoracic surgery (RATS) for higher stages non-small cell lung carcinoma (NSCLC) remains controversial. This study reports the feasibility of RATS in patients with stages IIB-IVA NSCLC. A single-institute, retrospective study was conducted with patients undergoing RATS for stages IIB-IVA NSCLC, from January 2015 until January 2020. Unforeseen N2 disease was excluded. Data were collected from the Dutch Lung Cancer Audit database. Conversion rate, radical (R0) resection rate, local recurrence rate and complications were analyzed, as were risk factors for conversion. RATS was performed in 95 patients with NSCLC clinical or pathological stages IIB (N = 51), IIIA (N = 39), IIIB (N = 2) and IVA (N = 3). 10.5% had received neoadjuvant chemoradiotherapy. Pathological staging was T3 in 33.7% and T4 in 34.7%. RATS was completed in 77.9% with a radical resection rate of 94.8%. Lobectomy was performed in 67.4% of the total resections. Conversion was for strategic (18.9%) and emergency (3.2%) reasons. Pneumonectomy (p = 0.001), squamous cell carcinoma (p < 0.001), additional resection of adjacent structures (p = 0.025) and neoadjuvant chemoradiation (p = 0.017) were independent risk factors for conversion. Major post-operative complications occurred in ten patients (10.5%) including an in-hospital mortality of 2.1% (n = 2). Median recurrence-free survival was estimated at 39.4 months (CI 16.4-62.5). Two- and 5-year recurrence-free survival rates were 53.8% and 36.7%, respectively. This study concludes that RATS is safe and feasible in higher staged NSCLC tumors after exclusion of unforeseen N2 disease. It brings new perspective on the potential of RATS in higher stages, dealing with larger and more invasive tumors.

A quantitative assessment of perfusion of the gastric conduit after oesophagectomy using near-infrared fluorescence with indocyanine green

INTRODUCTION

Anastomotic leakage is a severe complication after oesophageal resection with gastric conduit reconstruction. Poor perfusion of the gastric conduit plays an important role in the development of anastomotic leakage. Quantitative near-infrared (NIR) fluorescence angiography with indocyanine green (ICG-FA) is an objective technique that can be used for perfusion assessment. This study aims to assess perfusion patterns of the gastric conduit with quantitative ICG-FA.

METHODS

In this exploratory study, 20 patients undergoing oesophagectomy with gastric conduit reconstruction were included. A standardized NIR ICG-FA video of the gastric conduit was recorded. Postoperatively, the videos were quantified. Primary outcomes were the time-intensity curves and nine perfusion parameters from contiguous regions of interest on the gastric conduit. A secondary outcome was the inter-observer agreement of subjective interpretation of the ICG-FA videos between six surgeons. The inter-observer agreement was tested with an intraclass correlation coefficient (ICC).

RESULTS

In a total of 427 curves, three distinct perfusion patterns were recognized: pattern 1 (steep inflow, steep outflow); pattern 2 (steep inflow, minor outflow); and pattern 3 (slow inflow, no outflow). All perfusion parameters were significantly different between the perfusion patterns. The inter-observer agreement was poor - moderate (ICC:0.345,95%CI:0.164-0.584).

DISCUSSION

This was the first study to describe perfusion patterns of the complete gastric conduit after oesophagectomy. Three distinct perfusion patterns were observed. The poor inter-observer agreement of the subjective assessment underlines the need for quantification of ICG-FA of the gastric conduit. Further studies should evaluate the predictive value of perfusion patterns and parameters on anastomotic leakage.

Use of fluorescence imaging and indocyanine green during laparoscopic cholecystectomy: Results of an international Delphi survey

BACKGROUND

Published empirical data have increasingly suggested that using near-infrared fluorescence cholangiography during laparoscopic cholecystectomy markedly increases biliary anatomy visualization. The technology is rapidly evolving, and different equipment and doses may be used. We aimed to identify areas of consensus and nonconsensus in the use of incisionless near-infrared fluorescent cholangiography during laparoscopic cholecystectomy.

METHODS

A 2-round Delphi survey was conducted among 28 international experts in minimally invasive surgery and near-infrared fluorescent cholangiography in 2020, during which respondents voted on 62 statements on patient preparation and contraindications (n = 12); on indocyanine green administration (n = 14); on potential advantages and uses of near-infrared fluorescent cholangiography (n = 18); comparing near-infrared fluorescent cholangiography with intraoperative x-ray cholangiography (n = 7); and on potential disadvantages of and required training for near-infrared fluorescent cholangiography (n = 11).

RESULTS

Expert consensus strongly supports near-infrared fluorescent cholangiography superiority over white light for the visualization of biliary structures and reduction of laparoscopic cholecystectomy risks. It also offers other advantages like enhancing anatomic visualization in obese patients and those with moderate to severe inflammation. Regarding indocyanine green administration, consensus was reached that dosing should be on a milligrams/kilogram basis, rather than as an absolute dose, and that doses >0.05 mg/kg are necessary. Although there is no consensus on the optimum preoperative timing of indocyanine green injections, the majority of participants consider it important to administer indocyanine green at least 45 minutes before the procedure to decrease the light intensity of the liver.

CONCLUSION

Near-infrared fluorescent cholangiography experts strongly agree on its effectiveness and safety during laparoscopic cholecystectomy and that it should be used routinely, but further research is necessary to establish optimum timing and doses for indocyanine green.

Near-Infrared Fluorescence Tumor-Targeted Imaging in Lung Cancer: A Systematic Review

Lung cancer is the most common cancer type worldwide, with non-small cell lung cancer (NSCLC) being the most common subtype. Non-disseminated NSCLC is mainly treated with surgical resection. The intraoperative detection of lung cancer can be challenging, since small and deeply located pulmonary nodules can be invisible under white light. Due to the increasing use of minimally invasive surgical techniques, tactile information is often reduced. Therefore, several intraoperative imaging techniques have been tested to localize pulmonary nodules, of which near-infrared (NIR) fluorescence is an emerging modality. In this systematic review, the available literature on fluorescence imaging of lung cancers is presented, which shows that NIR fluorescence-guided lung surgery has the potential to identify the tumor during surgery, detect additional lesions and prevent tumor-positive resection margins.

The ESSO core curriculum committee update on surgical oncology

INTRODUCTION

Surgical oncology is a defined specialty within the European Board of Surgery within the European Union of Medical Specialists (UEMS). Variation in training and specialization still occurs across Europe. There is a need to align the core knowledge needed to fulfil the criteria across subspecialities in surgical oncology.

MATERIAL AND METHODS

The core curriculum, established in 2013, was developed with contributions from expert advisors from within the European Society of Surgical Oncology (ESSO), European Society for Radiotherapy and Oncology (ESTRO) and European Society of Medical Oncology (ESMO) and related subspeciality experts.

RESULTS

The current version reiterates and updates the core curriculum structure needed for current and future candidates who plans to train for and eventually sit the European fellowship exam for the European Board of Surgery in Surgical Oncology. The content included is not intended to be exhaustive but, rather to give the candidate an idea of expectations and areas for in depth study, in addition to the practical requirements. The five elements included are: Basic principles of oncology; Disease site specific oncology; Generic clinical skills; Training recommendations, and, lastly; Eligibility for the EBSQ exam in Surgical Oncology.

CONCLUSIONS

As evidence-based care for cancer patients evolves through research into basic science, translational research and clinical trials, the core curriculum will evolve, mature and adapt to deliver continual improvements in cancer outcomes for patients.

Fluorescence-guided surgery in colorectal cancer; A review on clinical results and future perspectives

BACKGROUND

Colorectal cancer is the fourth most diagnosed malignancy worldwide and surgery is one of the cornerstones of the treatment strategy. Near-infrared (NIR) fluorescence imaging is a new and upcoming technique, which uses an NIR fluorescent agent combined with a specialised camera that can detect light in the NIR range. It aims for more precise surgery with improved oncological outcomes and a reduction in complications by improving discrimination between different structures.

METHODS

A systematic search was conducted in the Embase, Medline and Cochrane databases with search terms corresponding to 'fluorescence-guided surgery', 'colorectal surgery', and 'colorectal cancer' to identify all relevant trials.

RESULTS

The following clinical applications of fluorescence guided surgery for colorectal cancer were identified and discussed: (1) tumour imaging, (2) sentinel lymph node imaging, (3) imaging of distant metastases, (4) imaging of vital structures, (5) imaging of perfusion. Both experimental and FDA/EMA approved fluorescent agents are debated. Furthermore, promising future modalities are discussed.

CONCLUSION

Fluorescence-guided surgery for colorectal cancer is a rapidly evolving field. The first studies show additional value of this technique regarding change in surgical management. Future trials should focus on patient related outcomes such as complication rates, disease free survival, and overall survival.

Intraoperative near-infrared fluorescence imaging of parathyroid adenomas with use of low-dose methylene blue

BACKGROUND

Intraoperative identification of parathyroid adenomas can be challenging. We hypothesized that low-doses methylene blue (MB) and near-infrared fluorescence (NIRF) imaging could be used to identify parathyroid adenomas intraoperatively.

METHODS

MB was injected intravenously after exploration at a dose of 0.5 mg/kg into 12 patients who underwent parathyroid surgery. NIRF imaging was performed using the Mini-FLARE imaging system.

RESULTS

In 10 of 12 patients, histology confirmed a parathyroid adenoma. In 9 of these patients, NIRF could clearly identify the parathyroid adenoma during surgery. Seven of these 9 patients had a positive preoperative (99m) Tc-sestamibi single photon emission CT (SPECT) scan. Importantly, in 2 patients, parathyroid adenomas could be identified only using NIRF.

CONCLUSION

This is the first study to show that low-dose MB can be used as NIRF tracer for identification of parathyroid adenomas, and suggests a correlation with preoperative (99m) Tc-sestamibi SPECT scanning.

Near-infrared fluorescence-guided resection of colorectal liver metastases

BACKGROUND

The fundamental principle of oncologic surgery is the complete resection of malignant cells. However, small tumors are often difficult to find during surgery using conventional techniques. The objectives of this study were to determine if optical imaging, using a contrast agent already approved for other indications, could improve hepatic metastasectomy with curative intent, to optimize dose and timing, and to determine the mechanism of contrast agent accumulation.

METHODS

The high tissue penetration of near-infrared (NIR) light was exploited by use of the FLARE (Fluorescence-Assisted Resection and Exploration) image-guided surgery system and the NIR fluorophore indocyanine green in a clinical trial of 40 patients undergoing hepatic resection for colorectal cancer metastases.

RESULTS

A total of 71 superficially located (< 6.2 mm beneath the liver capsule) colorectal liver metastases were identified and resected using NIR fluorescence imaging. Median tumor-to-liver ratio was 7.0 (range, 1.9-18.7) and no significant differences between time points or doses were found. Indocyanine green fluorescence was seen as a rim around the tumor, which is shown to be entrapment around cytokeratin 7-positive hepatocytes compressed by the tumor. Importantly, in 5 of 40 patients (12.5%, 95% confidence interval = 5.0-26.6), additional small and superficially located lesions were detected using NIR fluorescence, and were otherwise undetectable by preoperative computed tomography, intraoperative ultrasound, visual inspection, and palpation.

CONCLUSIONS

NIR fluorescence imaging, even when used with a nontargeted, clinically available NIR fluorophore, is complementary to conventional imaging and able to identify missed lesions by other modalities.

Image-guided hepatopancreatobiliary surgery using near-infrared fluorescent light

Background

Improved imaging methods and surgical techniques have created a new era in hepatopancreatobiliary (HPB) surgery. Despite these developments, visual inspection, palpation, and intraoperative ultrasound remain the most utilized tools during surgery today. This is problematic, though, especially in laparoscopic HPB surgery, where palpation is not possible. Optical imaging using near-infrared (NIR) fluorescence can be used for the real-time assessment of both anatomy (e.g., sensitive detection and demarcation of tumours and vital structures) and function (e.g., assessment of luminal flow and tissue perfusion) during both open and minimally invasive surgeries.

Methods

This article reviews the published literature related to preclinical development and clinical applications of NIR fluorescence imaging during HPB surgery.

Results

NIR fluorescence imaging combines the use of otherwise invisible NIR fluorescent contrast agents and specially designed camera systems, which are capable of detecting these contrast agents during surgery. Unlike visible light, NIR fluorescent light can penetrate several millimetres through blood and living tissue, thus providing improved detectability. Applications of this technique during HPB surgery include tumour imaging in liver and pancreas, and real-time imaging of the biliary tree.

Conclusions

NIR fluorescence imaging is a promising new technique that may someday improve surgical accuracy and lower complications.

Ex vivo sentinel node mapping in colon cancer combining blue dye staining and fluorescence imaging

BACKGROUND

The sentinel lymph node procedure has been proposed to improve nodal staging in colon cancer patients. The aim of this study was to assess the added value of near-infrared (NIR) fluorescence imaging to conventional blue dye staining for ex vivo sentinel lymph node mapping.

MATERIALS AND METHODS

We included 22 consecutive patients undergoing surgery for colon cancer. After tumor resection, we submucosally injected a premixed cocktail of the near-infrared lymphatic tracer HSA800 and blue dye around the tumor for detection of sentinel lymph nodes. We used the Mini-FLARE imaging system for fluorescence imaging.

RESULTS

In 95% of patients, we identified at least one sentinel lymph node. Overall, a total of 77 sentinel lymph nodes were identified, 77 of which were fluorescent (100%) and 70 of which were blue (91%). Sentinel lymph nodes that were located deeper in the mesenteric fat could easily be located by NIR fluorescence. In four of five patients with lymph node metastases, tumor cells were present in at least one of the sentinel lymph nodes.

CONCLUSIONS

This study shows the successful use and added value of the NIR fluorescence tracer HSA800 to conventional blue dye for the ex vivo sentinel lymph node procedure in colon cancer.

Dose optimization for near-infrared fluorescence sentinel lymph node mapping in patients with melanoma

BACKGROUND

Regional lymph node involvement is the most important prognostic factor in cutaneous melanoma. As only 20% of patients with melanoma have occult nodal disease and would benefit from a regional lymphadenectomy, the sentinel lymph node (SLN) biopsy was introduced. Near-infrared (NIR) fluorescence has been hypothesized to improve SLN mapping.

OBJECTIVES

  To assess the potential of intraoperative NIR fluorescence imaging to improve SLN mapping in patients with melanoma and to examine the optimal dose of indocyanine green adsorbed to human serum albumin (ICG:HSA).

METHODS

  Fifteen consecutive patients with cutaneous melanoma underwent the standard SLN procedure using (99m) technetium-nancolloid and patent blue. In addition, intraoperative NIR fluorescence imaging was performed after injection of 1·6 mL of 600, 800, 1000 or 1200 μmolL(-1) of ICG: HSA in four quadrants around the primary excision scar.

RESULTS

  NIR fluorescence SLN mapping was successful in 93% of patients. In one patient, no SLN could be identified using either conventional methods or NIR fluorescence. A total of 30 SLNs (average 2·0, range 1-7) were detected, 30 radioactive (100%), 27 blue (73%) and 30 NIR fluorescent (100%). With regard to the effect of concentration on signal-to-background ratios a trend (P=0·066) was found favouring the 600, 800 and 1000 μmol L(-1) groups over the 1200 μmol L(-1) group.

CONCLUSION

 This study demonstrates feasibility and accuracy of SLN mapping using ICG: HSA. Considering safety, cost and pharmacological characteristics, an ICG: HSA concentration of 600 μmolL(-1) appears optimal for SLN mapping in cutaneous melanoma, although lower doses need to be assessed.

Near-infrared fluorescence sentinel lymph node mapping of the oral cavity in head and neck cancer patients

OBJECTIVES

Elective neck dissection is frequently performed during surgery in head and neck cancer patients. The sentinel lymph node (SLN) procedure can prevent the morbidity of a neck dissection and improve lymph node staging by fine pathology. Near-infrared (NIR) fluorescence imaging is a promising technique to identify the sentinel lymph node (SLN) intraoperatively. This feasibility study explored the use of indocyanine green adsorbed to human serum albumin (ICG:HSA) for SLN mapping in head and neck cancer patients.

MATERIALS AND METHODS

A total of 10 consecutive patients with oral cavity or oropharyngeal cancer and a clinical N0 neck were included. After exposure of the neck, 1.6 mL of ICG:HSA (500 μM) was injected at four quadrants around the tumor. During the neck dissection, levels I-IV were measured for fluorescence using the Mini-FLARE imaging system.

RESULTS

In all 10 patients, NIR fluorescence imaging enabled visualization of one or more SLNs. A total of 17 SLNs were identified. The mean contrast between the fluorescent signal of the lymph nodes and of the surrounding tissue was 8.7±6.4. In 3 patients, of which 1 was false-negative, lymph node metastases were found. After administration of ICG:HSA, the average number of fluorescent lymph nodes significantly increased over time (P<0.001).

CONCLUSION

This study demonstrated feasibility to detect draining lymph nodes in head and neck cancer patients using NIR fluorescence imaging. However, the fluorescent tracer quickly migrated beyond the SLN to higher tier nodes.

Near-infrared fluorescence imaging of a solitary fibrous tumor of the pancreas using methylene blue

A 67-year-old female presented with unexplained abdominal pain. A contrast-enhanced computed tomography scan of the abdomen incidentally revealed a mass in the uncinate process of the pancreas. This mass was resected and based on histopathological findings, diagnosed as a solitary fibrous tumor (SFT) of the pancreas. A SFT is an extremely rare benign mesenchymal tumor that in 65% of cases affects the visceral pleura but can also affect extra-pleural sites. The intraoperative demarcation of pancreatic tumors, such as SFTs, can be challenging. In this report, the first clear intraoperative identification of a SFT of the pancreas in a human was shown using near-infrared fluorescence and methylene blue.

Translational optical imaging in diagnosis and treatment of cancer

In cancer imaging, many different modalities are used that each have their specific features, leading to the combined use of different techniques for the detection, staging and treatment evaluation of cancer. Optical imaging using near-infrared fluorescence light is a new imaging modality that has recently emerged in the field of cancer imaging. After extensive preclinical research, the first steps of translation to the clinical practice are currently being made. In this article, we discuss the preclinical and clinical results of near-infrared optical imaging for non-invasive detection and classification of tumors, therapy monitoring, sentinel lymph node procedures, and image-guided cancer surgery. Widespread availability of imaging systems and optical contrast agents will enable larger studies on their clinical benefit and can help establish a definitive role in clinical practice.

Randomized comparison of near-infrared fluorescence imaging using indocyanine green and 99(m) technetium with or without patent blue for the sentinel lymph node procedure in breast cancer patients

Background

Near-infrared (NIR) fluorescence imaging using indocyanine green (ICG) has the potential to improve sentinel lymph node (SLN) mapping of breast cancer. We performed a randomized clinical trial to assess the value of blue dyes when used in combination with NIR fluorescence. We also preliminarily examined the possibility of performing SLN mapping without radiotracers.

Methods

Clinical trial subjects were 24 consecutive breast cancer patients scheduled to undergo SLN biopsy. All patients received standard of care using 99^m technetium-nanocolloid and received 1.6 mL of 500 μM ICG injected periareolarly. Patients were randomly assigned to undergo SLN biopsy with or without patent blue. To assess the need for radiocolloids to localize the SLN or SLNs, the surgeon did not use the handheld gamma probe during the first 15 min after the axillary skin incision.

Results

SLN mapping was successful in 23 of the 24 patients. No significant difference was found in signal-to-background ratio between the groups with and without patent blue (8.3 ± 3.8 vs. 10.3 ± 5.7, respectively, P = 0.32). In both groups, 100 % of SLNs were radioactive and fluorescent, and in the patent blue group, only 84 % of SLNs were stained blue. In 25 % of patients, the use of the gamma probe was necessary to localize the SLN within the first 15 min.

Conclusions

This study shows that there is no benefit of using patent blue for SLN mapping in breast cancer patients when using NIR fluorescence and 99^m technetium-nanocolloid. NIR fluorescence imaging outperformed patent blue in all patients.

Simultaneous Assessment of Luminal Integrity and Vascular Perfusion of the Gastrointestinal Tract Using Dual-Channel Near-Infrared Fluorescence

Anastomotic complications such as stenosis and leakage in the gastrointestinal (GI) tract can cause high patient morbidity and mortality. To identify the potential preconditions of these complications intraoperatively, we explored the use of two 700 nm near-infrared (NIR) fluorophores administered intraluminally: (1) chlorella, an over-the-counter herbal supplement containing high concentrations of chlorophyll, and (2) methylene blue (MB). In parallel, we administered the 800 nm NIR fluorophore indocyanine green (ICG) intravenously to assess vascular function. Dual-channel, real-time intraoperative imaging and quantitation of the contrast to background ratio (CBR) were performed under normal conditions or after anastomosis or leakage of the stomach and intestines in 35 kg Yorkshire pigs using the Fluorescence-Assisted Resection and Exploration (FLARE) imaging system. Luminal integrity could be assessed with relatively high sensitivity with either chlorella or MB, although chlorella provided significantly higher CBR. ICG angiography provided assessment of blood perfusion of normal, ischemic, and anastomotic areas of the GI tract. Used simultaneously, 700 nm (chlorella or MB) and 800 nm (ICG) NIR fluorescence permitted independent assessment of luminal integrity and vascular perfusion of the GI tract intraoperatively and in real time. This technology has the potential to identify critical complications, such as anastomotic leakage, intraoperatively, when correction is still possible.

Simultaneous assessment of luminal integrity and vascular perfusion of the gastrointestinal tract using dual-channel near-infrared fluorescence

Anastomotic complications such as stenosis and leakage in the gastrointestinal (GI) tract can cause high patient morbidity and mortality. To identify the potential preconditions of these complications intraoperatively, we explored the use of two 700 nm near-infrared (NIR) fluorophores administered intraluminally: (1) chlorella, an over-the-counter herbal supplement containing high concentrations of chlorophyll, and (2) methylene blue (MB). In parallel, we administered the 800 nm NIR fluorophore indocyanine green (ICG) intravenously to assess vascular function. Dual-channel, real-time intraoperative imaging and quantitation of the contrast to background ratio (CBR) were performed under normal conditions or after anastomosis or leakage of the stomach and intestines in 35 kg Yorkshire pigs using the Fluorescence-Assisted Resection and Exploration (FLARE) imaging system. Luminal integrity could be assessed with relatively high sensitivity with either chlorella or MB, although chlorella provided significantly higher CBR. ICG angiography provided assessment of blood perfusion of normal, ischemic, and anastomotic areas of the GI tract. Used simultaneously, 700 nm (chlorella or MB) and 800 nm (ICG) NIR fluorescence permitted independent assessment of luminal integrity and vascular perfusion of the GI tract intraoperatively and in real time. This technology has the potential to identify critical complications, such as anastomotic leakage, intraoperatively, when correction is still possible.

Optimization of near-infrared fluorescent sentinel lymph node mapping for vulvar cancer

OBJECTIVES

Near-infrared fluorescence imaging has the potential to improve sentinel lymph node mapping in vulvar cancer, which was assessed in the current study. Furthermore, dose optimization of indocyanine green adsorbed to human serum albumin was performed.

STUDY DESIGN

Nine vulvar cancer patients underwent the standard sentinel lymph node procedure using (99m)technetium-nancolloid and patent blue. In addition, intraoperative imaging was performed after peritumoral injection of 1.6 mL of 500, 750, or 1000 μM of indocyanine green adsorbed to human serum albumin.

RESULTS

Near-infrared fluorescence sentinel lymph node mapping was successful in all patients. A total of 14 sentinel lymph nodes (average, 1.6; range, 1-4) were detected: 14 radioactive (100%), 11 blue (79%), and 14 near-infrared fluorescent (100%).

CONCLUSION

This study demonstrates feasibility and accuracy of sentinel lymph node mapping using indocyanine green adsorbed to human serum albumin. Considering safety, cost, and pharmacy preferences, an indocyanine green adsorbed to human serum albumin concentration of 500 μM appears optimal for sentinel lymph node mapping in vulvar cancer.

The clinical use of indocyanine green as a near-infrared fluorescent contrast agent for image-guided oncologic surgery

Optical imaging using near-infrared (NIR) fluorescence provides new prospects for general and oncologic surgery. ICG is currently utilised in NIR fluorescence cancer-related surgery for three indications: sentinel lymph node (SLN) mapping, intraoperative identification of solid tumours, and angiography during reconstructive surgery. Therefore, understanding its advantages and limitations is of significant importance. Although non-targeted and non-conjugatable, ICG appears to be laying the foundation for more widespread use of NIR fluorescence-guided surgery.

Near-infrared fluorescence imaging in patients undergoing pancreaticoduodenectomy

BACKGROUND

Intraoperative visualization of pancreatic tumors has the potential to improve radical resection rates. Intraoperative visualization of the common bile duct and bile duct anastomoses could be of added value. In this study, we explored the use of indocyanine green (ICG) for these applications and attempted to optimize injection timing and dose.

METHODS

Eight patients undergoing a pancreaticoduodenectomy were injected intravenously with 5 or 10 mg ICG. During and after injection, the pancreas, tumor, common bile duct and surrounding organs were imaged in real time using the Mini-FLARE™ near-infrared (NIR) imaging system.

RESULTS

No clear tumor-to-pancreas contrast was observed, except for incidental contrast in 1 patient. The common bile duct was clearly visualized using NIR fluorescence, within 10 min after injection, with a maximal contrast between 30 and 90 min after injection. Patency of biliary anastomoses could be visualized due to biliary excretion of ICG.

CONCLUSION

No useful tumor demarcation could be visualized in pancreatic cancer patients after intravenous injection of ICG. However, the common bile duct and biliary anastomoses were clearly visualized during the observation period. Therefore, these imaging strategies could be beneficial during biliary surgery in cases where the surgical anatomy is aberrant or difficult to identify.

Optical image-guided surgery--where do we stand?

In cancer surgery, intra-operative assessment of the tumor-free margin, which is critical for the prognosis of the patient, relies on the visual appearance and palpation of the tumor. Optical imaging techniques provide real-time visualization of the tumor, warranting intra-operative image-guided surgery. Within this field, imaging in the near-infrared light spectrum offers two essential advantages: increased tissue penetration of light and an increased signal-to-background-ratio of contrast agents. In this article, we review the various techniques, contrast agents, and camera systems that are currently used for image-guided surgery. Furthermore, we provide an overview of the wide range of molecular contrast agents targeting specific hallmarks of cancer and we describe perspectives on its future use in cancer surgery.

Abstract 4140: Preclinical optimization and clinical translation of near-infrared fluorescence imaging of colorectal liver metastases using indocyanine green

Background: Near-infrared (NIR) fluorescence imaging using indocyanine green (ICG) is a promising technique to obtain real-time assessment of the extent and number of colorectal liver metastases during liver surgery. The current study aims to optimize dosage and timing of ICG administration.

Materials and methods: The Mini-FLARE imaging system was used for real-time identification of liver tumors in 18 rats. Liver tumors were measured at 24, 48, 72 or 96 hours after administration of 0.04, 0.08, or 0.16 mg ICG (0.13, 0.26 or 0.53 mg / kg, respectively). Guided by these results, intraoperative identification of liver metastases was performed in 12 patients undergoing liver resection. NIR fluorescence imaging was performed 24 or 48 hours after administration of 10 or 20 mg ICG (0.13 or 0.26 mg / kg, respectively). After intraoperative imaging, resection specimens were sliced to examine internal fluorescent patterns using the Mini-FLARE imaging system. Subsequently, frozen tissue sections were measured for fluorescence using the Nuance multispectral imager.

Results: Using NIR fluorescence imaging and ICG, all colorectal liver metastases (N = 34), could be identified in all rats. Average tumor-to-liver (TLR) ratio over all groups was 3.0 ± 1.2. Liver signal was lower in the 72 h time group compared to other time points, resulting in a significantly higher TLR. ICG dose did not significantly influence TLR, but a trend was found favoring the 0.08 mg dose group. Clinically, during intraoperative NIR fluorescence imaging, all superficially located metastases (&lt; 1 cm beneath liver capsule) were identified (N = 18). Average TLR was 11.1 ± 5.1 and no significant differences between time-points or doses were found. Liver signal was comparable to pre-injection signal at 24 to 48 hours post-injection, eliminating the need to test other time-points. In all patients, a fluorescent rim around the tumor was found, as described in earlier studies. Using fluorescence microscopy, this clear fluorescent rim was localized in stromal tissue in the transition area between tumor and normal liver tissue in all liver metastases. In this area, multiple cell types that are involved in tissue inflammation (e.g. granulocytes, lymphocytes) were found. In two patients, additional small (2 – 8 mm) metastases were identified using NIR fluorescence that were otherwise missed preoperatively and intraoperatively using only visual inspection and ultrasound.

Conclusions: This study demonstrates that colorectal cancer liver metastases can be clearly identified during surgery using ICG and the Mini-FLARE imaging system. NIR fluorescence imaging has the potential to improve intraoperative detection of in particular small and superficially located liver metastases and can therefore be seen as an addition to the conventional imaging modalities.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4140. doi:10.1158/1538-7445.AM2011-4140

Toward optimization of imaging system and lymphatic tracer for near-infrared fluorescent sentinel lymph node mapping in breast cancer

Background

Near-infrared (NIR) fluorescent sentinel lymph node (SLN) mapping in breast cancer requires optimized imaging systems and lymphatic tracers.

Materials and Methods

A small, portable version of the FLARE imaging system, termed Mini-FLARE, was developed for capturing color video and two semi-independent channels of NIR fluorescence (700 and 800 nm) in real time. Initial optimization of lymphatic tracer dose was performed using 35-kg Yorkshire pigs and a 6-patient pilot clinical trial. More refined optimization was performed in 24 consecutive breast cancer patients. All patients received the standard of care using ^99mTechnetium-nanocolloid and patent blue. In addition, 1.6 ml of indocyanine green adsorbed to human serum albumin (ICG:HSA) was injected directly after patent blue at the same location. Patients were allocated to 1 of 8 escalating ICG:HSA concentration groups from 50 to 1000 μM.

Results

The Mini-FLARE system was positioned easily in the operating room and could be used up to 13 in. from the patient. Mini-FLARE enabled visualization of lymphatic channels and SLNs in all patients. A total of 35 SLNs (mean = 1.45, range 1–3) were detected: 35 radioactive (100%), 30 blue (86%), and 35 NIR fluorescent (100%). Contrast agent quenching at the injection site and dilution within lymphatic channels were major contributors to signal strength of the SLN. Optimal injection dose of ICG:HSA ranged between 400 and 800 μM. No adverse reactions were observed.

Conclusions

We describe the clinical translation of a new NIR fluorescence imaging system and define the optimal ICG:HSA dose range for SLN mapping in breast cancer.

Electronic supplementary material

The online version of this article (doi:10.1245/s10434-011-1566-x) contains supplementary material, which is available to authorized users.

Randomized, double-blind comparison of indocyanine green with or without albumin premixing for near-infrared fluorescence imaging of sentinel lymph nodes in breast cancer patients

Near-infrared (NIR) fluorescence imaging has the potential to improve sentinel lymph node (SLN) mapping in breast cancer. Indocyanine green (ICG) is currently the only clinically available fluorophore that can be used for SLN mapping. Preclinically, ICG adsorbed to human serum albumin (ICG:HSA) improves its performance as a lymphatic tracer in some anatomical sites. The benefit of ICG:HSA for SLN mapping of breast cancer has not yet been assessed in a clinical trial. We performed a double-blind, randomized study to determine if ICG:HSA has advantages over ICG alone. The primary endpoint was the fluorescence brightness, defined as the signal-to-background ratio (SBR), of identified SLNs. Clinical trial subjects were 18 consecutive breast cancer patients scheduled to undergo SLN biopsy. All patients received standard of care using (99m)Technetium-nanocolloid and patent blue. Patients were randomly assigned to receive 1.6 ml of 500 μM ICG:HSA or ICG that was injected periareolarly directly after patent blue. The Mini-Fluorescence-Assisted Resection and Exploration (Mini-FLARE) imaging system was used for NIR fluorescence detection and quantitation. SLN mapping was successful in all patients. Patient, tumor, and treatment characteristics were equally distributed over the treatment groups. No significant difference was found in SBR between the ICG:HSA group and the ICG alone group (8.4 vs. 11.3, respectively, P = 0.18). In both groups, the average number of detected SLNs was 1.4 ± 0.5 SLNs per patient (P = 0.74). This study shows that there is no direct benefit of premixing ICG with HSA prior to injection for SLN mapping in breast cancer patients, thereby reducing the cost and complexity of the procedure. With these optimized parameters that eliminate the necessity of HSA, larger trials can now be performed to determine patient benefit.

Near-infrared fluorescence imaging of liver metastases in rats using indocyanine green

BACKGROUND

Near-infrared (NIR) fluorescence imaging using indocyanine green (ICG) is a promising technique to obtain real-time assessment of the extent and number of colorectal liver metastases during surgery. The current study aims to optimize dosage and timing of ICG administration.

MATERIALS AND METHODS

Liver tumors were induced in 18 male WAG/Rij rats by subcapsular inoculation of CC531 rat colorectal cancer cells into three distinct liver lobes. Rats were divided in two groups: imaging after 24 and 48 h or 72 and 96 h after intravenous ICG administration. In each time group, rats were allocated to three dose groups: 0.04, 0.08, or 0.16 mg ICG. Intraoperative imaging and ex vivo measurements were performed using the Mini-FLARE imaging system and confirmed by fluorescence microscopy. Fluorescence intensity was quantified using the Mini-FLARE software and the difference between tumor signal and liver signal (tumor-to-liver ratio; TLR) was calculated.

RESULTS

In all 18 rats, all colorectal liver metastases (n = 34), some as small as 1.2 mm, were identified using ICG and the Mini-FLARE imaging system. Average tumor-to-liver ratio (TLR) over all groups was 3.0 ± 1.2. TLR was significantly higher in the 72 h time group compared with other time points. ICG dose did not significantly influence TLR, but a trend was found favoring the 0.08 mg dose group. Fluorescence microscopy demonstrated a clear fluorescent rim around the tumor.

CONCLUSIONS

This study demonstrates that colorectal cancer liver metastases can be clearly identified during surgery using ICG and the Mini-FLARE imaging system, with optimal timing of 72 h post-injection and an optimal dose of 0.08 mg (0.25 mg/kg) ICG. NIR fluorescence imaging has the potential to improve intraoperative detection of micrometastases and, thus, the completeness of resection.

Intraoperative near-infrared fluorescence imaging of colorectal metastases targeting integrin α(v)β(3) expression in a syngeneic rat model

AIM

Near-infrared (NIR) fluorescence optical imaging is a promising technique to assess the extent of colorectal metastases during curative-intended surgery. However, NIR fluorescence imaging of liver metastases is highly challenging due to hepatic uptake and clearance of many fluorescent dyes. In the current study, the biodistribution and the ability to demarcate liver and peritoneal metastases were assessed during surgery in a syngeneic rat model of colorectal cancer using an integrin α(v)β(3)-directed NIR fluorescence probe.

METHODS

Liver tumors and peritoneal metastases were induced in 7 male WAG/Rij rats by subcapsular inoculation of 0.5 × 10(6) CC531 colorectal cancer rat cells into three distinct liver lobes. Intraoperative and ex vivo fluorescence measurements were performed 24 (N = 3 rats, 7 tumors) and 48 h (N = 4 rats, 9 tumors) after intravenous administration of the integrin α(v)β(3)-directed NIR fluorescence probe.

RESULTS

Colorectal metastases had a minimal two-fold higher NIR fluorescence signal than healthy liver tissue and other abdominal organs (p < 0.001). The tumor-to-background ratio was independent of time of imaging (24 h vs. 48 h post-injection; p = 0.31), which facilitates flexible operation planning in future clinical applications. Total fluorescence intensity was significantly correlated with the size of metastases (R(2) = 0.92 for the 24 h group, R(2) = 0.96 for the 48 h group).

CONCLUSION

These results demonstrate that colorectal intra-abdominal metastases can be clearly demarcated during surgery using an integrin α(v)β(3) targeting NIR fluorescence probe. Translating these findings to the clinic will have an excellent potential to substantially improve the quality of cancer surgery.

Clinical translation of ex vivo sentinel lymph node mapping for colorectal cancer using invisible near-infrared fluorescence light

Background

Sentinel lymph node (SLN) mapping in colorectal cancer may have prognostic and therapeutic significance; however, currently available techniques are not optimal. We hypothesized that the combination of invisible near-infrared (NIR) fluorescent light and ex vivo injection could solve remaining problems of SLN mapping in colorectal cancer.

Methods

The FLARE imaging system was used for real-time identification of SLNs after injection of the NIR lymphatic tracer HSA800 in the colon and rectum of (n = 4) pigs. A total of 32 SLN mappings were performed in vivo and ex vivo after oncologic resection using an identical injection technique. Guided by these results, SLN mappings were performed in ex vivo tissue specimens of 24 consecutive colorectal cancer patients undergoing resection.

Results

Lymph flow could be followed in real-time from the injection site to the SLN using NIR fluorescence. In pigs, the SLN was identified in 32 of 32 (100%) of SLN mappings under both in vivo and ex vivo conditions. Clinically, SLNs were identified in all patients (n = 24) using the ex vivo strategy within 5 min after injection of fluorescent tracer. Also, 9 patients showed lymph node involvement (N1 disease). In 1 patient, a 3-mm mesenteric metastasis was found adjacent to a tumor-negative SLN.

Conclusions

The current pilot study shows proof of principle that ex vivo NIR fluorescence-guided SLN mapping can provide high-sensitivity, rapid, and accurate identification of SLNs in colon and rectum. This creates an experimental platform to test optimized, non-FDA-approved NIR fluorescent lymphatic tracers in a clinical setting.

Image-guided tumor resection using real-time near-infrared fluorescence in a syngeneic rat model of primary breast cancer

Tumor involvement of resection margins is found in a large proportion of patients who undergo breast-conserving surgery. Near-infrared (NIR) fluorescence imaging is an experimental technique to visualize cancer cells during surgery. To determine the accuracy of real-time NIR fluorescence imaging in obtaining tumor-free resection margins, a protease-activatable NIR fluorescence probe and an intraoperative camera system were used in the EMR86 orthotopic syngeneic breast cancer rat model. Influence of concentration, timing and number of tumor cells were tested in the MCR86 rat breast cancer cell line. These variables were significantly associated with NIR fluorescence probe activation. Dosing and tumor size were also significantly associated with fluorescence intensity in the EMR86 rat model, whereas time of imaging was not. Real-time NIR fluorescence guidance of tumor resection resulted in a complete resection of 17 out of 17 tumors with minimal excision of normal healthy tissue (mean minimum and a mean maximum tumor-free margin of 0.2 ± 0.2 mm and 1.3 ± 0.6 mm, respectively). Moreover, the technique enabled identification of remnant tumor tissue in the surgical cavity. Histological analysis revealed that the NIR fluorescence signal was highest at the invasive tumor border and in the stromal compartment of the tumor. In conclusion, NIR fluorescence detection of breast tumor margins was successful in a rat model. This study suggests that clinical introduction of intraoperative NIR fluorescence imaging has the potential to increase the number of complete tumor resections in breast cancer patients undergoing breast-conserving surgery.

Novel intraoperative near-infrared fluorescence camera system for optical image-guided cancer surgery

Current methods of intraoperative tumor margin detection using palpation and visual inspection frequently result in incomplete resections, which is an important problem in surgical oncology. Therefore, real-time visualization of cancer cells is needed to increase the number of patients with a complete tumor resection. For this purpose, near-infrared fluorescence (NIRF) imaging is a promising technique. Here we describe a novel, handheld, intraoperative NIRF camera system equipped with a 690 nm laser; we validated its utility in detecting and guiding resection of cancer tissues in two syngeneic rat models. The camera system was calibrated using an activated cathepsin-sensing probe (ProSense, VisEn Medical, Woburn, MA). Fluorescence intensity was strongly correlated with increased activated-probe concentration (R2= .997). During the intraoperative experiments, a camera exposure time of 10 ms was used, which provided the optimal tumor to background ratio. Primary mammary tumors (n = 20 tumors) were successfully resected under direct fluorescence guidance. The tumor to background ratio was 2.34 using ProSense680 at 10 ms camera exposure time. The background fluorescence of abdominal organs, in particular liver and kidney, was high, thereby limiting the ability to detect peritoneal metastases with cathepsin-sensing probes in these regions. In conclusion, we demonstrated the technical performance of this new camera system and its intraoperative utility in guiding resection of tumors.

Intraoperative near-infrared fluorescence imaging in perforator flap reconstruction: current research and early clinical experience

Despite recent advances in perforator flap reconstruction, there can be significant variability in vessel size and location. Although preoperative evaluation may provide valuable information, real-time intraoperative methods have the potential to provide the greatest benefit. Our laboratory has developed the Fluorescence-Assisted Resection and Exploration (FLARE) near-infrared (NIR) fluorescence imaging system for intraoperative visualization of details of the underlying vasculature. The FLARE system uses indocyanine green, a safe and reliable NIR fluorophore already FDA-approved for other indications. The system has been optimized in large-animal models for the identification of perforator size, location, and perfusion and has also been translated to the clinic for use during breast reconstruction after mastectomy. In this article, we review our preclinical and clinical data, as well as literature describing the use of similar NIR fluorescence imaging systems in plastic and reconstructive surgery.

Image-Guided Surgery: Breast Cancer Detection Using Monoclonal Antibodies Conjugated to a Near-Infrared Fluorescent Dye in a Syngeneic Rat Model

Background: Incomplete tumor resections occur frequently in patients undergoing breast-conserving surgery. As the surgeon can only rely on palpation and visual inspection, real-time visualization of cancer cells during surgery is needed to increase the number of complete tumor resections. Near-infrared fluorescence (NIRF) imaging using an intra-operative camera system is a novel technique to assess the extent of disease during surgery. Advantages of NIRF light (700-900 nm) include high tissue penetration up to several centimeters deep and low autofluorescence providing sufficient signal-to-noise ratio. Currently, several NIRF dyes are available for chemical conjugation to molecules that can target tumors, e.g. antibodies. This study aimed to investigate whether monoclonal antibodies conjugated to a NIRF dye could detect primary breast carcinomas in a syngeneic rat model.Methods: The hormone-dependent syngeneic breast cancer rat model EMR86 and its derived cell line MCR86 were used. Tumors were induced by orthotopic implantation of fresh EMR86 tumor fragments of 1 mm3 into the flanks at four sites in female WAG/Rij rats (Harlan, the Netherlands). The mouse monoclonal antibody MG1 was used for tumor cell detection. MG1 (IgG2a) recognizes a membrane epitope of rat cancer cells of epithelial origin and is developed by our research group. MG1 was conjugated to the NIRF dye CW-800 (LI-COR, USA) and dye/protein ratio was determined using absorbance measurements (UltroSpec, Amersham, UK). Fluorescence imaging of cells, animals and organs was performed using IVIS Spectrum (Caliper, USA) and Odyssey (LI-COR, USA) equipment.Results: Conjugated antibodies MG1-CW800 bound specifically to cultured MCR86 cells. The signal intensity was linearly correlated with the number of cells and concentration of MG1-CW800 (R2=0.99, p&lt;0.00001). Addition of unconjugated MG1 lowered the fluorescent signal in a competitive binding assay, showing that labeling did not influence binding properties. Intravenous injection of unconjugated MG1 (200 μg/rat) in 3 Wag/Rij rats and subsequent immunohistochemical analysis of tissue sections revealed a specific and exclusive binding of MG1 to the EMR86 tumors and no difference in staining intensity between 24 and 48hrs after injection. Intravenous injection of conjugated MG1-CW800 (200 μg/rat) demonstrated a clear fluorescent demarcation of EMR86 tumors and the surrounding tissue after spectral unmixing (paired t-test 8.17, p&lt;0.00001). Mean fluorescence did not differ between 24 and 48hrs after injection (t=1.85, p=0.11). However, a two-fold increase of the dye/protein ratio led to a two-fold increase of the in vivo fluorescence (t=-6.40, p=0.0001).Conclusion: Intravenous injection of monoclonal antibodies MG1 conjugated to the NIRF dye CW800 enabled detection of primary breast carcinomas in the syngeneic hormone-dependent EMR86 rat model. This study demonstrates proof-of-concept for future labeling of clinically relevant antibodies (e.g. HER2/neu, EGF, VEGF). Translation of this technique to breast cancer patients can lead to intra-operative identification of optimal resection margins in order to increase the comple tumor resection rate.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5006.

Intra-Operative Imaging of the Invasive Tumor Border by a Cathepsin-Sensing Near-Infrared Fluorescence Probe in a Syngeneic Breast Cancer Rat Model

Background: An incomplete tumor resection occurs in 5-45% of the patients undergoing breast-conserving surgery. As the surgeon can only rely on palpation and visual inspection, real-time visualization of cancer cells at the time of surgery is needed to increase the number of complete tumor resections. Near-infrared fluorescence (NIRF) imaging is a promising technique to assess the extent of disease during surgery. This study aimed to validate NIRF imaging in a breast cancer rat model.Methods: The hormone-dependent syngeneic breast cancer rat model EMR86 and its derived cell line MCR86 were used. Tumor cells were detected with the cathepsin-activatable (mainly cathepsin-B) NIRF probe ProSense® (VisEn Medical, USA). Fluorescence imaging of the animals, organs and tissue sections was performed using IVIS Spectrum (Caliper, USA), Odyssey (LI-COR, USA) and SP5 microscope (Leica, Germany). Intra-operative fluorescence imaging was performed using the Fluobeam700 system equipped with a 690 nm class 3B laser and a CCD camera (Fluoptics, France).Results: ProSense was activated by cleavage in MCR86 cells. The signal intensity was linearly correlated with the number of cells, the concentration of ProSense and the incubation time (all R2&gt;0.93, p&lt;0.0001). The influence of ProSense concentration and tumor volume on fluorescent intensity was confirmed in nine rats each bearing four tumors (mean volume=0.38 ±0.36 cm3). In contrast to the in vitro data, no difference in fluorescence intensity was found between 24hr and 48hr after injection of ProSense (paired t=-0.27, p=0.80). Therefore, subsequent experiments were conducted 24hr after injection. Calibration of the intra-operative camera system demonstrated a strong correlation of fluorescence intensity and activated ProSense concentration (R2=0.9903). Using the intra-operative NIRF camera, all 64 mammary tumors (0.01-1.8 cm3) were successfully detected. Histological assessment of residual fluorescent hotspots confirmed the presence of breast cancer cells indicating incomplete resections of the primary tumor (margin positivity). The signal intensity of the tumor was 60-fold higher than the surrounding tissue (p&lt;0.0001). Fluorescence scanning microscopy of 2-mm thick tumor sections revealed a significantly two-fold higher signal intensity at the tumor border compared to the tumor center (t=-8.12, p&lt;0.00001). Fluorescent microscopy of 10 um frozen tissue sections confirmed the higher intensity at the border, which was mainly located in the tumor-associated stroma.Conclusion: We demonstrated that it is possible to detect and resect sub-mm breast tumor depositions under fluorescent guidance in a syngeneic rat model. The higher fluorescent signal at the tumor border likely reflects the extra-cellular matrix degradation induced by increased cathepsin-B activity. Intra-operative imaging of cathepsin activity at the invasive border facilitates clear demarcation of tumor margins. Clinical introduction of this technique has the potential to substantially improve breast-conserving surgery.Acknowledgement: We want to thank Fluoptics for providing us with the Fluobeam700 system to perform the above described experiments.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5007.

Motion-gated acquisition for in vivo optical imaging

Wide-field continuous wave fluorescence imaging, fluorescence lifetime imaging, frequency domain photon migration, and spatially modulated imaging have the potential to provide quantitative measurements in vivo. However, most of these techniques have not yet been successfully translated to the clinic due to challenging environmental constraints. In many circumstances, cardiac and respiratory motion greatly impair image quality and/or quantitative processing. To address this fundamental problem, we have developed a low-cost, field-programmable gate array-based, hardware-only gating device that delivers a phase-locked acquisition window of arbitrary delay and width that is derived from an unlimited number of pseudo-periodic and nonperiodic input signals. All device features can be controlled manually or via USB serial commands. The working range of the device spans the extremes of mouse electrocardiogram (1000 beats per minute) to human respiration (4 breaths per minute), with timing resolution <or=0.06%, and jitter <or=0.008%, of the input signal period. We demonstrate the performance of the gating device, including dramatic improvements in quantitative measurements, in vitro using a motion simulator and in vivo using near-infrared fluorescence angiography of beating pig heart. This gating device should help to enable the clinical translation of promising new optical imaging technologies.