Fluorescence navigation with indocyanine green for detecting sentinel lymph nodes in breast cancer

A parallel excitation based fluorescence molecular tomography system for whole-body simultaneous imaging of small animals

Challenges remain in imaging complete dynamic physiological processes in vivo through the whole small animal body using fluorescence molecular tomography (FMT). In this article, a novel non-contact full-angle FMT system that enables whole-body simultaneous imaging of small animals is presented. The whole-body simultaneous imaging ability is achieved by employing a line-shaped parallel excitation source, which can provide extended spatial sampling dataset to reconstruct multiple fluorescent targets distributed in whole animal body during one full-angle FMT imaging process. The key performances of this system were evaluated by a series of experiments. Quantitation linearity for over two orders of magnitude of fluorescence markers concentration was demonstrated, and an accessible simultaneous imaging domain of 4.0 x 1.5 cm² could be achieved utilizing the parallel excitation pattern. Moreover, the in vivo imaging feasibility and performance were validated by localizing two fluorescent targets implanted at different positions of a nude mouse. The results suggest that compared with conventional single point excitation FMT system, the proposed system can achieve a whole-body simultaneous imaging domain and impart the ability to image complete dynamic physiological processes in vivo.

Image-guided sentinel lymph node mapping and nanotechnology-based nodal treatment in lung cancer using invisible near-infrared fluorescent light

Current methods for sentinel lymph node (SLN) mapping and nodal treatment in lung cancer remain inadequate for routine clinical use. In this study, we discuss the potential for using the combination of invisible near-infrared (NIR) fluorescent light and nanotechnology for these applications. NIR fluorescence imaging has recently received significant attention for in vivo imaging applications because of its low tissue autofluorescence, high photon penetration into living tissue, and high signal-to-background ratio. Our large animal in vivo studies have been able to successfully identify SLNs in lung tissue, and several clinical studies have examined the use of NIR fluorescence imaging systems for SLN mapping in breast and gastric cancer. Promising new nanoparticle technologies, when combined with NIR fluorescence imaging, offer the potential for image-guided treatment of lymph nodes at high risk for tumor recurrence. This review provides a theoretic and empiric framework for developing the next generation of diagnostic and therapeutic agents for lung cancer.

Near-Infrared Fluorescence Imaging in Humans with Indocyanine Green: A Review and Update

Near-infrared (NIR) fluorescence imaging clinical studies have been reported in the literature with six different devices that employ various doses of indocyanine green (ICG) as a non-specific contrast agent. To date, clinical applications range from (i) angiography, intraoperative assessment of vessel patency, and tumor/metastasis delineation following intravenous administration of ICG, and (ii) imaging lymphatic architecture and function following subcutaneous and intradermal ICG administration. In the latter case, NIR fluorescence imaging may enable new discoveries associated with lymphatic function due to (i) a unique niche that is not met by any other conventional imaging technology and (ii) its exquisite sensitivity enabling high spatial and temporal resolution. Herein, we (i) review the basics of clinical NIR fluorescence imaging, (ii) survey the literature on clinical application of investigational devices using ICG fluorescent contrast, (iii) provide an update of non-invasive dynamic lymphatic imaging conducted with our FDPM device, and finally, (iv) comment on the future NIR fluorescence imaging for non-invasive and intraoperative use given recent demonstrations showing capabilities for imaging following microdose administration of contrast agent.

Sentinel lymph nodes and lymphatic vessels: noninvasive dual-modality in vivo mapping by using indocyanine green in rats--volumetric spectroscopic photoacoustic imaging and planar fluorescence imaging

PURPOSE

To noninvasively map sentinel lymph nodes (SLNs) and lymphatic vessels in rats in vivo by using dual-modality nonionizing imaging-volumetric spectroscopic photoacoustic imaging, which measures optical absorption, and planar fluorescence imaging, which measures fluorescent emission-of indocyanine green (ICG).

MATERIALS AND METHODS

Institutional animal care and use committee approval was obtained. Healthy Sprague-Dawley rats weighing 250-420 g (age range, 60-120 days) were imaged by using volumetric photoacoustic imaging (n = 5) and planar fluorescence imaging (n = 3) before and after injection of 1 mmol/L ICG. Student paired t tests based on a logarithmic scale were performed to evaluate the change in photoacoustic signal enhancement of SLNs and lymphatic vessels before and after ICG injection. The spatial resolutions of both imaging systems were compared at various imaging depths (2-8 mm) by layering additional biologic tissues on top of the rats in vivo. Spectroscopic photoacoustic imaging was applied to identify ICG-dyed SLNs.

RESULTS

In all five rats examined with photoacoustic imaging, SLNs were clearly visible, with a mean signal enhancement of 5.9 arbitrary units (AU) + or - 1.8 (standard error of the mean) (P < .002) at 0.2 hour after injection, while lymphatic vessels were seen in four of the five rats, with a signal enhancement of 4.3 AU + or - 0.6 (P = .001). In all three rats examined with fluorescence imaging, SLNs and lymphatic vessels were seen. The average full width at half maximum (FWHM) of the SLNs in the photoacoustic images at three imaging depths (2, 6, and 8 mm) was 2.0 mm + or - 0.2 (standard deviation), comparable to the size of a dissected lymph node as measured with a caliper. However, the FWHM of the SLNs in fluorescence images widened from 8 to 22 mm as the imaging depth increased, owing to strong light scattering. SLNs were identified spectroscopically in photoacoustic images.

CONCLUSION

These two modalities, when used together with ICG, have the potential to help map SLNs in axillary staging and to help evaluate tumor metastasis in patients with breast cancer.

New approaches to lymphatic imaging

Accurate imaging of the lymphatic system can aid in cancer staging, optimize surgical procedures to reduce lymphedema, and may one day be a means of delivering intralymphatic therapy. The Sentinel Lymph Node (SLN) concept has been pivotal in driving new imaging techniques. Metastasis to a SLN is a critical indicator of advanced disease. However, presently, few tools are available for imaging the lymphatics, and even fewer are available for locating the SLN for biopsy. Recently, new macromolecular agents, including gadolinium-labeled dendrimers, fluorescent quantum dots, and fluorescently-labeled immunoglobins, have been used to image the lymphatics and SLN with MRI and optical techniques, and new fluorescent nanoparticles such as upconverting nanocrystals are potential future agents. Additionally, multi-modality probes combining two modalities such as optical/MR dendrimers have been designed to provide both preoperative imaging, and intraoperative guidance during lymph node resections. These probes can map the lymphatic system for maximal therapeutic benefit while minimizing complications such as lymphedema. Advances in the understanding of the molecular mechanisms of lymphangiogenesis and lymphatic spread of tumors offer the opportunity for more targeted imaging of the lymphatic system. Additionally, these imaging agents could be used as powerful research tools for tracking immunological cells and monitoring the immune response as well as providing the means to deliver lymphatic-targeted therapies. The future holds great promise for the translation of these methods to the clinic.

A novel method for sentinel lymph node biopsy by indocyanine green fluorescence technique in breast cancer

We investigated the feasibility of sentinel lymph node (SLN) biopsy using indocyanine green (ICG) technique in 411 patients with early breast cancer at three institutes. ICG, a fluorescence source, and blue dye were injected into the subareolar area to enable real-time image-guided surgery and identification of SLN fluorescence after meticulous dissection. The subcutaneous lymphatic channels were precisely detected in all cases. SLN identification rate was 99% (408/411) with a mean of 2.3 nodes identified per patient. Thirty-nine cases (9.5%) had SLNs involved and all of them were ICG positive. Thus, the ICG technique has a high SLN identification rate comparable with that of the radioisotope method.

An alternative tool for intraoperative assessment of renal vasculature after revascularization of a transplanted kidney

Intraoperative assessment of flow in the renal artery and vein after reconstruction is a crucial matter in kidney transplantation. Conventional Doppler ultrasound detects blood flow only in a limited area. The authors report a newly developed device that noninvasively visualizes the condition of perfusion of an entire allograft at one time from any angle and also clearly detects the state of anastomosis of the renal vessels. This near-infrared camera system provides the opportunity for the intraoperative assessment of the vasculature of renal allografts.

Video-assisted thoracoscopic indocyanine green fluorescence imaging system shows sentinel lymph nodes in non-small-cell lung cancer

OBJECTIVE

The primary objective was to assess the feasibility and accuracy of intraoperative sentinel lymph node mapping by using a video-assisted thoracoscopic indocyanine green fluorescence imaging system in patients with clinical stage I non-small-cell lung cancer.

METHODS

Thirty-one patients who underwent operation between January 2009 and September 2009 were investigated for sentinel node biopsy. Indocyanine green fluorescence imaging was applied by an infrared light charge-coupled device, and sentinel nodes were identified intraoperatively and dissected. Histologic examination by hematoxylin-eosin staining was used to evaluate metastases.

RESULTS

Sentinel lymph nodes were identified by segmentectomy in 11 of 14 patients (78.5%) and by lobectomy in 14 of 17 patients (82.4%). The total identification rate was 80.7% (25/31 patients), the false-negative rate was 0% (0/24 patients), and the overall accuracy rate was 80.7% (25/31 patients).

CONCLUSION

Video-assisted thoracoscopic indocyanine green fluorescence image-guided surgery is feasible for sentinel node biopsy and may be a powerful tool to eliminate unnecessary lymph node dissection in patients with lung cancer.

Low-frequency wide-field fluorescence lifetime imaging using a high-power near-infrared light-emitting diode light source

Fluorescence lifetime imaging (FLi) could potentially improve exogenous near-infrared (NIR) fluorescence imaging, because it offers the capability of discriminating a signal of interest from background, provides real-time monitoring of a chemical environment, and permits the use of several different fluorescent dyes having the same emission wavelength. We present a high-power, LED-based, NIR light source for the clinical translation of wide-field (larger than 5 cm in diameter) FLi at frequencies up to 35 MHz. Lifetime imaging of indocyanine green (ICG), IRDye 800-CW, and 3,3(')-diethylthiatricarbocyanine iodide (DTTCI) was performed over a large field of view (10 cm by 7.5 cm) using the LED light source. For comparison, a laser diode light source was employed as a gold standard. Experiments were performed both on the bench by diluting the fluorescent dyes in various chemical environments in Eppendorf tubes, and in vivo by injecting the fluorescent dyes mixed in Matrigel subcutaneously into CD-1 mice. Last, measured fluorescence lifetimes obtained using the LED and the laser diode sources were compared with those obtained using a state-of-the-art time-domain imaging system and with those previously described in the literature. On average, lifetime values obtained using the LED and the laser diode light sources were consistent, exhibiting a mean difference of 3% from the expected values and a coefficient of variation of 12%. Taken together, our study offers an alternative to laser diodes for clinical translation of FLi and explores the use of relatively low frequency modulation for in vivo imaging.

Sentinel node mapping guided by indocyanine green fluorescence imaging during laparoscopic surgery in gastric cancer

BACKGROUND

Indocyanine green (ICG) fluorescence imaging has recently been reported as a new method for sentinel node (SN) mapping in several types of cancers. In this study, we determined the possible usefulness of SN mapping guided by ICG fluorescence imaging during laparoscopy-assisted gastrectomy (LAG) for gastric cancer.

METHODS

Our series consisted of 77 patients with cT1- or cT2-stage gastric cancer who had undergone LAG (LAG group; 38 patients) or conventional open gastrectomy (OG group; 39 patients). Intraoperative SN mapping guided by ICG fluorescence imaging was conducted with a charge-coupled device camera with a light-emitting diode as the light source and a cut filter as the detector.

RESULTS

The detection rate and mean number of fluorescent nodes (FNs) were 94.7% and 7.9, respectively, in the LAG group, and 94.9% and 7.2, respectively, in the OG group. The accuracy and false-negative rates were 97.2% (35 of 36 cases) and 25% (1 of 4), respectively, in the LAG group, and 91.9% (34 of 37) and 23.1% (3 of 13), respectively, in the OG group. Among 33 LAG group patients and 27 OG group patients without FN metastasis, lymph node metastasis was found only in non-SNs located in the same lymphatic basin as the detected FNs.

CONCLUSIONS

SN mapping guidance by ICG fluorescence imaging could be useful for predicting the lymph node metastasis in gastric cancer, even during LAG. Our data suggest that dissection of the lymphatic basin containing FNs with laparoscopic surgery may be a promising approach as a new type of minimally invasive surgery for patients with cT1- or cT2-stage gastric cancer having no metastasis in FNs.

Evaluation of sentinel node biopsy by combined fluorescent and dye method and lymph flow for breast cancer

BACKGROUND

Conservative breast resection with subsequent sentinel lymph node biopsy (SNB) is an increasingly popular initial approach for the treatment of breast cancer due to decreased invasiveness. SNB is a shorter procedure with fewer side effects than more substantial surgical procedures, but it sometimes fails to identify metastatic disease. Therefore, a highly sensitive and convenient method is needed to identify sentinel lymph nodes (SLN) with a high probability of containing disease in SNB. We compared the combination of radioisotope or dye with a fluorescence compound to analyze lymph flow to identify targets for SNB.

MATERIALS AND METHODS

We examined patients with breast cancer lacking metastases in the axillary lymph node (ALN). Two methods for targeted SNB were developed: (1) Indocyanine Green (ICG) and Patent blue were injected into the skin overlying the tumor and sub-areolar region just before the surgical procedure. (2) ICG and radiocolloid were injected into the skin overlying the tumor and sub-areolar region. The draining fluorescent lymphatic duct was visualized using a Photodynamic Eye (PDE). We removed the SLNs that were identified by the dye and fluorescence imaging methods. Method 1 was applied to 113 patients undergoing SNB, and 29 patients were treated with Method 2. In our study, patients were grouped by lymph flow into two types: Type C demonstrated convergence to one lymph duct. Type S demonstrated separate lymph ducts.

RESULTS

Using the fluorescence imaging method, 99.3% of SLNs were identified, and 3.8 SLNs per patient were seen. The SLN identification rates for Patent blue dye and radiocolloid were 92.9% and 100%, respectively, while 1.9 and 2.0 SLNs per patient, respectively, were seen with these methods. We classified two types of lymph flow based on the pattern of lymphatic drainage. Type C converged to a single lymph duct, while Type S drained to separate ducts. Type S lymph drainage was seen in 29/142 patients (20.4%), and Type C drainage was found in 113/141 patients (79.6%). Of the patients with Type S drainage, there were 4.1 SLNs per patient, but only 3.4 SLNs per patient were seen in individuals with Type C drainage. Forty cases had metastases found in the ALNs, and five of these cases were dye-negative and fluorescence-positive. Among these cases, the average number of SLNs identified was one.

CONCLUSION

The combination of fluorescence with a visible dye is a highly sensitive method for SLN identification. When SNB is guided by only the dye method, there is a risk of missing appropriate SLNs in patients with Type S lymph drainage or weak dye staining. The use of a fluorescence method together with dye could increase sensitivity of detection in these cases. Furthermore, fluorescent methods are ideal for hospitals that cannot use conventional radioactive measures.

ICG fluorescence-guided sentinel node biopsy for axillary nodal staging in breast cancer

BACKGROUND

Sentinel lymph node (SLN) biopsy is a selective approach to axillary staging of breast cancer with reduced morbidity. Current detection methods including radioisotope and blue dye show good results but some drawbacks are remaining. Indocyanine green (ICG) fluorescence detection was evaluated as a new method for SLN biopsy in breast cancer allowing both transcutaneous visualization of lymphatic vessels and intraoperative identification of SLN.

METHODS

Forty-three women with clinically node negative breast cancer received subareolar injection of ICG for fluorescence detection of SLN. All patients underwent either planned axillary lymph node dissection (ALND) with SLN biopsy or selective SLN biopsy to determine need for ALND. Clinical feasibility, detection rate, sensitivity, and axillary recurrence after isolated SLN biopsy were analyzed.

RESULTS

Overall ICG fluorescence imaging identified 2.0 SLN in average in 42 of 43 patients (detection rate: 97.7%). Metastatic involvement of the SLN was found in 17 of 18 nodal positive patients by conventional histopathology (sensitivity: 94.4%). Immunohistochemistry revealed isolated tumor cells in five further cases. There was only one false-negative case in 43 patients (5.6%). In 17 of 23 overall nodal positive patients, the SLN was the only positive lymph node. After a median follow-up of 4.7 years none of the patients presented with axillary recurrence.

CONCLUSION

ICG fluorescence imaging is a new method for SLN biopsy in breast cancer with acceptable sensitivity and specificity comparable to conventional methods. One advantage of this technique is that it allows transcutaneous visualization of lymphatic vessels and intraoperative lymph node detection without radioisotope.

Sentinel lymph node mapping by a near-infrared fluorescent heptamethine dye

We describe a near-infrared fluorescent heptamethine dye (IR-780 iodide) with unique properties for sentinel lymph node (SLN) mapping in both small and large animals. This dye has a significant photobrightening effect in serum and a long retention time in the lymphatic system which allows to acquire much higher signal-to-noise ratios. Injection of only 10 nmol of this dye permits SLNs to be imaged easily in pigs using excitation fluence rates of only 2 microW/cm(2). In addition, this dye has a unique stability property after formalin fixation in tissues which raises the possibility of developing new and sensitive means of detecting lymph nodes in harvested surgical specimens. This dye can be completely cleared from the circulation in a couple of days and does not cause acute systemic toxicity.

The use of fluorescent dyes and probes in surgical oncology

AIMS AND BACKGROUND

Improved visualization of surgical targets inside of the patient helps to improve radical resection of the tumor while sparing healthy surrounding tissue. In order to achieve an image, optical contrast must be generated by properties intrinsic to the tissue, or require the attachment of special visualization labels to the tumor. In this overview the current status of the clinical use of fluorescent dyes and probes are reviewed.

METHODS

In this review, all experimental and clinical studies concerning fluorescent imaging were included. In addition, in the search for the optimal fluorescent imaging modality, all characteristics of a fluorescent dye were described.

FINDINGS AND CONCLUSIONS

Although the technique of imaging through fluorescence sounds promising and several animal models show efficacy, official approval of these agents for further clinical evaluation, is eagerly awaited.

Clinical implications of near-infrared fluorescence imaging in cancer

Near-infrared (NIR) fluorescence cancer imaging is a growing field for both preclinical and clinical application to the clinical management for cancer patients due to its advantageous features, including a high spatial resolution, portability, real-time display and detailed molecular profiling with the multiplexed use of fluorescent probes. In this review, we present a basic concept of NIR fluorescence imaging and overview its potential clinical applications for in vivo cancer imaging, including cancer detection/characterization, lymphatic imaging (sentinel lymph node detection) and surgical/endoscopic guidance. NIR fluorescence imaging can compensate some limitations of conventional imaging modalities, and thus it could play an important role for cancer imaging combined with other modalities in clinical practice.

Intraoperative fluorescent imaging using indocyanine green for liver mapping and cholangiography

BACKGROUND

Preoperative imaging is widely used and extremely helpful in hepatobiliary surgery. However, transfer of preoperative data to a intraoperative situation is very difficult. Surgeons need intraoperative anatomical information using imaging data for safe and precise operation in the field of hepatobiliary surgery. We have developed a new system for mapping liver segments and cholangiograms using intraoperative indocyanine green (ICG) fluorescence under infrared light observation.

METHOD

The imaging technique for mapping liver segments and cholangiogram based on ICG fluorescence used an infrared-based navigation system. Eighty one patients with liver tumors underwent hepatectomy from 2006, January to 2009, March. In liver surgery, 1 ml of ICG was injected via the portal vein under observation by the fluorescent imaging system. Fourteen patients were underwent laparoscopic cholecystectomy for chronic cholecystitis with gallstones. In laparoscopic cholecystectomy, 5 ml of ICG was administered intravenously just before operation and the bile duct was observed using the infrared-based navigation system.

RESULT

This new technique successfully identified stained subsegments and segments of the liver in 73 of 81 patients (90.1%). Moreover, clear mapping of liver segments was obtained even against a background of liver cirrhosis. Fluorescent cholangiography clearly showed the common bile duct and cystic duct in 10 of 14 patients (71.4%). No adverse reactions to the ICG were encountered.

CONCLUSION

Application of this technique allows intraoperative identification of anatomical landmark in hepatobiliary surgery.

Intraoperative exploration of biliary anatomy using fluorescence imaging of indocyanine green in experimental and clinical cholecystectomies

BACKGROUND/PURPOSE

We evaluated the usefulness of intraoperative exploration of the biliary anatomy using fluorescence imaging with indocyanine green (ICG) in experimental and clinical cholecystectomies.

METHODS

The experimental study was done using two 40-kg pigs and the clinical study was done in 12 patients for whom cholecystectomy was planned from January 2009 to June 2009. Initially we used a laparoscopic approach for the evaluation of fluorescence imaging of the biliary system in the two pigs. Then the clinical study was started on the basis of these experimental results. ICG (1.0 ml/body of 2.5 mg/ml ICG) was infused 1-2 h before surgery. With the subjects under general anesthesia we observed in real time the condition of the biliary tract under the guidance of fluorescence imaging employing an infrared camera or a prototype laparoscope. ICG was added intravenously to observe the location or flow condition of the cystic artery.

RESULTS

We obtained a clear view of the biliary tract and the location of the cystic duct in the two pigs. Local compression with a transparent hemispherical plastic device was effective for offering a clearer view. The biliary tract, except for the gallbladder, was clearly recognized in all clinical subjects. Local compression with a transparent hemispherical plastic device for open cholecystectomy and a flat plastic device for laparoscopy provided clearer visualization of the confluence between the cystic duct and common bile duct or common hepatic duct. The location of the cystic artery was revealed after division of the connective tissues, and the flow condition of the cystic artery was confirmed 7-10 s after intravenous re-infusion of ICG. There were no adverse events related to the intraoperative procedure or the ICG itself.

CONCLUSIONS

This method is safe and easy for the identification of the biliary anatomy, without requiring cannulation into the cystic duct, X-ray equipment, or the use of radioactive materials. Although fluorescence imaging is still at an early stage of application in comparison with ordinary intraoperative cholangiography, we expect that this method will become routine, offering a lower degree of invasiveness that will help avoid bile duct injury.

Feasibility of a lateral region sentinel node biopsy of lower rectal cancer guided by indocyanine green using a near-infrared camera system

BACKGROUND

A lateral pelvic lymph node dissection (LPLD) for lower rectal cancer may be beneficial for a limited number of patients. If sentinel node (SN) navigation surgery could be applied to lower rectal cancer, then unnecessary LPLDs could be avoided. The aim of this study was to investigate the feasibility of lateral region SN biopsy by means of indocyanine green (ICG) visualized with a near-infrared camera system (Photodynamic Eye, PDE).

METHODS

This study investigated the existence of a lateral region SN in 25 patients with lower rectal cancer. ICG was injected around the tumor, and the lateral pelvic region was observed with PDE.

RESULTS

With PDE, the lymph nodes and lymph vessels that received ICG appeared as shining fluorescent spots and streams in the fluorescence image. This allowed the detection of not only tumor-negative SNs but also tumor-positive SNs as shining spots. The lateral SNs were detected in 6 of 6 T1 and T2 diseases and 17 of 19 T3 diseases. The lateral SNs were successfully identified in 23 (92%) of the 25 patients. The mean number of lateral SNs per patients was 2.1. Of the 23 patients, 6 patients underwent LPLD. Of the 3 patients who had a tumor-negative SN, all dissected lateral non-SNs were negative in all 3 cases.

CONCLUSIONS

We could detect the lateral SNs, not only in T1 and T2 disease, but also in T3 disease. Although this is only a preliminary study, the detection of lateral SNs in lower rectal cancer by means of the ICG fluorescence imaging system is considered to be a promising technique that may be used for determining the indications for performing LPLD.

Near-infrared fluorescence venography: a navigation system for varicose surgery

BACKGROUND

Successful varicose vein surgery depends on accurate assessment and identification of veins. We report clinical experiences with a simple, rapid method of detecting varicose veins using indocyanine green (ICG) fluorescence video venography.

PATIENTS AND METHOD

ICG percutaneously injected into the great saphenous vein at the ankle or into the ligated end of veins in 20 patients with varicose veins was used as the optical tracer agent. Intraoperative ICG imaging was performed using a laser-fluorescence imaging device.

RESULTS

ICG fluorescence venography was performed without any adverse effects. The imaging device provides unparalleled visualization of varicose veins during vein ligation, phlebectomy, and stripping.

CONCLUSION

This method enabled easy, safe, and accurate diagnoses, simplified the search for veins during the operation, and minimized surgical invasiveness in varicose vein surgery. The system has great potential as a navigational technique for phlebologic diagnosis and treatment of varicose veins. Further research and development to improve its utility are suggested.

Sentinel node detection method using contrast-enhanced ultrasonography with sonazoid in breast cancer: preliminary clinical study

This study aimed to evaluate the usefulness of sentinel lymph node (SLN) detection in breast cancer using contrast-enhanced ultrasonography (CEUS) with subareolar Sonazoid injection. The subjects were 20 breast cancer patients. General anesthesia was induced and 2 mL of Sonazoid was injected subareolarly. After massage of the injection site, the axillary area was observed transdermally using coded phase inversion harmonic ultrasonography with mechanical indices of 0.15 to 0.19. When contrast-enhanced lymph nodes (LNs) were seen, they were defined as CE-SLN. Two other SLN detection methods, the gamma-probe-guided and dye-guided methods, were performed together. We evaluated the SLNs detected by each method to determine if they corresponded with each other and calculated the SLN detection rate. After the SLNs were resected, pathologic examinations were done. The SLN detection rate of the CEUS-guided method, the dye-guided method and the gamma-probe-guided method were 70%, 75% and 100%, respectively. There was no statistically significant difference in these rates between the CEUS-guided and dye-guided methods (p = 0.99) but the CEUS-guided method showed a significantly lower rate than the gamma-probe-guided method (p = 0.020), and dye-guided method also showed a significantly lower rate than the gamma-probe-guided method (p = 0.047). The number of CE-SLNs was 1 or 2 (average 1.1) and each took 2 to 20 (average 5.3) min to detect. The CE-SLNs corresponded grossly with SLNs detected by the gamma-probe-guided and dye-guided methods. The pathologic results indicated no metastasis from the resected SLNs in 15 of 20 cases. However, the CEUS-guided method detected 12 cases of these 15 and CE-SLNs were detected in two of the remaining five metastasis cases. In summary, in breast cancer patients, after subareolar injection of Sonazoid, contrast-enhanced LNs were observed in real time with ultrasonography. In an initial clinical study of 20 cases, the detection rate of the CEUS-guided method was less than that of the gamma-probe-guided method. It is suggested that the CEUS-guided method using Sonazoid may, with some improvements, be a useful new modality for sentinel node identification.

The FLARE intraoperative near-infrared fluorescence imaging system: a first-in-human clinical trial in breast cancer sentinel lymph node mapping

BACKGROUND

Invisible NIR fluorescent light can provide high sensitivity, high-resolution, and real-time image-guidance during oncologic surgery, but imaging systems that are presently available do not display this invisible light in the context of surgical anatomy. The FLARE imaging system overcomes this major obstacle.

METHODS

Color video was acquired simultaneously, and in real-time, along with two independent channels of NIR fluorescence. Grayscale NIR fluorescence images were converted to visible "pseudo-colors" and overlaid onto the color video image. Yorkshire pigs weighing 35 kg (n = 5) were used for final preclinical validation of the imaging system. A six-patient pilot study was conducted in women undergoing sentinel lymph node (SLN) mapping for breast cancer. Subjects received (99m)Tc-sulfur colloid lymphoscintigraphy. In addition, 12.5 microg of indocyanine green (ICG) diluted in human serum albumin (HSA) was used as an NIR fluorescent lymphatic tracer.

RESULTS

The FLARE system permitted facile positioning in the operating room. NIR light did not change the look of the surgical field. Simultaneous pan-lymphatic and SLN mapping was demonstrated in swine using clinically available NIR fluorophores and the dual NIR capabilities of the system. In the pilot clinical trial, a total of nine SLNs were identified by (99m)Tc- lymphoscintigraphy and nine SLNs were identified by NIR fluorescence, although results differed in two patients. No adverse events were encountered.

CONCLUSIONS

We describe the successful clinical translation of a new NIR fluorescence imaging system for image-guided oncologic surgery.

Lymphangiogenesis and cancer metastasis

Metastasis is a characteristic trait of most tumour types and the cause for the majority of cancer deaths. Many tumour types, including melanoma and breast and prostate cancers, first metastasize via lymphatic vessels to their regional lymph nodes. Although the connection between lymph node metastases and shorter survival times of patients was made decades ago, the active involvement of the lymphatic system in cancer, metastasis has been unravelled only recently, after molecular markers of lymphatic vessels were identified. A growing body of evidence indicates that tumour-induced lymphangiogenesis is a predictive indicator of metastasis to lymph nodes and might also be a target for prevention of metastasis. This article reviews the current understanding of lymphangiogenesis in cancer anti-lymphangiogenic strategies for prevention and therapy of metastatic disease, quantification of lymphangiogenesis for the prognosis and diagnosis of metastasis and in vivo imaging technologies for the assessment of lymphatic vessels, drainage and lymph nodes.

A novel image-guided surgery of hepatocellular carcinoma by indocyanine green fluorescence imaging navigation

BACKGROUND AND OBJECTIVES

The clear delineation between tumor and normal tissue is ideal for real-time surgical navigation imaging. We present a novel indocyanine green (ICG) fluorescence imaging technique to visualize hepatocellular carcinoma (HCC).

METHODS

Ten patients with solitary HCC underwent hepatectomy between February and September 2007 at Osaka Medical Center for Cancer and Cardiovascular Diseases. ICG had been injected intravenously several days before surgery at a dose of 0.5 mg/kg body weight. After laparotomy, the liver was inspected with intraoperative ultrasonography (IOUS), and then with a near-infrared (NIR) fluorescence imaging system (PDE; Hamamatsu Photonics K.K. Hamamatsu, Japan).

RESULTS

All the 10 primary tumors showed bright fluorescent signals and could be completely removed with negative margins under the guide of PDE. In four cases (40.0%), new HCC nodules that were not detected by use of any preoperative examinations including IOUS were detected by PDE. These newly identified HCC nodules were very small in size and most of the tumors were well-differentiated HCCs.

CONCLUSIONS

This novel technique is simple and safe, and is therefore considered to be a promising tool for routine intraoperative imaging during a hepatic resection and further clinical exploration for HCC.

Fluorescence navigation with indocyanine green for detecting sentinel nodes in extramammary Paget's disease and squamous cell carcinoma

The radioisotope navigation method, which has usually been used for identification of sentinel nodes, is less useful in locating sentinel nodes close to primary lesions in cases of extramammary Paget's disease because of overlapping radioactivity from the primary site. We applied fluorescence navigation with indocyanine green (ICG) in two patients with skin cancer to cover this defect. The use of a charge-coupled device camera enabled real-time visualization of dynamic lymph flow without skin incision. The inguinal skin over the identified sentinel node with a handheld gamma probe was in accordance with the point detected by ICG fluorescence in a patient with squamous cell carcinoma of the foot. Sentinel node biopsy using fluorescence navigation with ICG proved to be easy and reliable.

Evaluation of cholecystic venous flow using indocyanine green fluorescence angiography

BACKGROUND/PURPOSE

The cholecystic veins are thought to be an important metastatic route of gallbladder carcinoma to the liver. In the present study we evaluated the cholecystic venous drainage area, utilizing a novel method, indocyanine green (ICG) fluorescence angiography after superselective catheterization of the cholecystic artery, to detect and elucidate cholecystic venous flow.

METHODS

Cannulation of the cholecystic artery was performed under laparotomy in nine patients who required a cholecystectomy. After ICG injection into the cholecystic artery, the cholecystic venous flow images were visualized with a near-infrared camera system and were analyzed according to site, shape, and time of fluorescence.

RESULTS

Fluorescence images of the cholecystic venous flow could be viewed as real-time images in all patients. We demonstrated that the route of the cholecystic venous flow could be classified into two patterns: type 1, in which the cholecystic veins flowed directly into the hepatic parenchyma adjacent to the gallbladder; and type 2, in which the veins flowed into sites separate from the gallbladder. In the type 1 pattern, fluorescence was observed in segment (S; defined according to Couinaud's nomenclature) 4a or S5 adjacent to the gallbladder in all cases. On the other hand, in the type-2 pattern, fluorescence was observed in S4a (6/9), S5 (8/9), S4b (2/9), S3 (2/9), S1 (1/9), S2 (1/9), and S8 (1/9) distant from the gallbladder. Overall, two-thirds of the cases showed fluorescence in segments other than S4a or S5.

CONCLUSIONS

Indocyanine green (ICG) fluorescence angiography is considered to be a useful method to detect and elucidate cholecystic venous flow in real time. This study showed that the cholecystic venous flow spread to the liver through two different pathways, one that flowed directly into the hepatic parenchyma adjacent to the gallbladder, while the other flowed into sites separate from the gallbladder. Taking these findings into consideration, we may therefore need to reconsider the preventive effects of a hepatic resection.

Colonic tattooing using fluorescence imaging with light-emitting diode-activated indocyanine green: a feasibility study

PURPOSE

We investigated the feasibility of a fluorescence imaging technique using light-emitting diode (LED)-activated indocyanine green (ICG) fluorescence.

METHODS

Indocyanine green injections were given to patients undergoing preoperative colonoscopy for early colon cancer or colon adenoma. During subsequent laparotomy, the colon was first observed with the naked eye, and then using a prototype machine with a charge-coupled device (CCD) video camera equipped with a cutoff filter and a LED at a wavelength of 760 nm as the light source.

RESULTS

LED-induced fluorescence showed tumor localization clearly and accurately in all ten patients (100%) enrolled in this study, whereas it was seen with the naked eye as a green spot in only two patients (20%) (P = 0.0077; Wilcoxon's signed-rank test). There were no complications of LED-induced fluorescence and no inflammatory signs were noted on the hematoxylin-eosin-stained slides for the identified injection sites in the resected specimens.

CONCLUSIONS

Colonic tattooing using this fluorescence imaging technique of LED-activated ICG fluorescence is a new concept of colonic marking based on the characteristics that ICG is a near infrared fluorescent dye, and is useful, without any adverse effects, to identify perioperatively the tumor localization.

ICG fluorescence endoscope for visualization of the placental vascular network

Intrauterine laser photocoagulation for twin-twin transfusion syndrome (TTTS) needs accurate in-situ recognition of placental vascular anastomosis. Because the conventional procedure is highly dependent upon the operators' skill and experience, we developed a new way to visualize the placental vascular network by a rigid-type fluorescence endoscope coupled with intravenous administration of Indocyanine green (ICG). The feasibility of the fluorescence endoscope was examined with monkey placentas and pregnant rats. The ICG fluorescence endoscope can visualize the placental vascular network in detail even in the presence of turbid amniotic fluid. Thus, this method is potentially useful for in-situ definition of the placental vascular anastomoses during the treatment for TTTS. In addition, our rigid-type fluorescence endoscope will also be a useful tool for lymph node dissection using ICG by endoscopic surgery.

Lymphatic imaging in humans with near-infrared fluorescence

While the lymphatic system is increasingly associated with diseases of prevalence, study of these diseases is difficult owing to the paucity of imaging techniques with the sensitivity and temporal resolution to discriminate lymphatic function. Herein, we review the known, pertinent features of the human lymphatic system in health and disease and set the context for a number of emerging studies that use near-infrared fluorescence imaging to non-invasively assess tumor draining lymphatic basins in cancer patients, intraoperatively guide resection of first draining lymph nodes, and to interrogate the difference between normal and aberrant lymphatic structure and function.

Sentinel node mapping guided by indocyanine green fluorescence imaging in gastric cancer

OBJECTIVE

In this study, we determined the possible usefulness of sentinel node (SN) mapping guided by indocyanine green (ICG) fluorescence imaging in the management of gastric cancer.

SUMMARY BACKGROUND DATA

ICG fluorescence imaging system has recently been developed for obtaining biochemical information from living tissues.

METHODS

Our series consisted of 56 patients with gastric cancer who underwent standard gastrectomy with lymphadenectomy. Two milliliters of ICG solution (0.5%) was injected into the submucosa around the tumor endoscopically before the operation or into the subserosa intraoperatively. ICG fluorescence imaging was conducted using a charge-coupled device camera with a light-emitting diode having a wavelength of 760 nm as the light source and a cut filter to filter out light with wavelengths below 820 nm as the detector.

RESULTS

SNs were detected in 54 (96.4%) of the 56 patients, and the mean number of SNs was 7.2 +/- 7.0. Even SNs that were not green in color could be easily and clearly visualized by ICG fluorescence imaging. cT1-stage cancers were associated with a significantly higher accuracy rate (97.2% vs. 72.2%, P = 0.0127) than cT2-or cT3-stage cancers. Preoperative ICG injection was associated with a significantly higher incidence of cT1-stage cancers (87.1% vs. 40.0%, P = 0.0004), a larger mean number of SNs (9.9 +/- 7.5 vs. 4.1 +/- 5.0, P < 0.0001), a higher accuracy rate (100% vs. 73.9%, P = 0.0039), and a lower false negative rate (0% vs. 60.0%, P = 0.0345) as compared with intraoperative ICG injection.

CONCLUSIONS

This study shows that ICG fluorescence imaging allows highly sensitive image-guided intraoperative SN mapping in cases of gastric cancer. Our data suggest that SN mapping guided by ICG fluorescence imaging might be useful for predicting the metastatic status in lymph nodes in cases of gastric cancer, especially those with cT1-stage cancer.

Image-guided liver mapping using fluorescence navigation system with indocyanine green for anatomical hepatic resection

BACKGROUND

In malignant hepatic neoplasm, anatomic resection could improve survival and limit complications from hepatectomy. Our purpose was to develop an intraoperative method for identifying segment and subsegment of the liver with high-sensitivity near-infrared fluorescence imaging.

METHODS

The subjects were 35 patients with hepatic malignant liver disease who received hepatectomy in 2006. The segments of liver method of identification that used infrared observation camera system termed Photo Dynamic Eye-2 (PDE-2) with indocianine green (ICG) for the patient with malignant liver tumor (hepatocellular carcinoma: 13 cases; metastatic liver cancer: 18 cases; intrahepatic cholangio carcinoma: 4 cases) were performed before liver resection.

RESULTS

Although greenish stain of the liver surface after the injection of ICG via portal vein is not visible clearly without infrared observation camera system PDE-2, 1 minute after injection of ICG with fluorescent using infrared observation camera system PDE-2, demarcation of liver segment and subsegment was clearly detected. Ten minutes after injection of ICG with fluorescent using infrared observation camera system PDE-2, fluorescence of liver subsegment remained. Stained subsegment and segment of liver were identifiable in 33 (94.3%) of the 35 patients. There were no complications or side-effects related to the injection of patent blue dye.

CONCLUSION

We demonstrated here that near-infrared fluorescence imaging system is a novel and reliable intraoperative technique to identify hepatic segment and subsegment for anatomical hepatic resection.

New horizons for imaging lymphatic function

In this review, we provide a comprehensive summary of noninvasive imaging modalities used clinically for the diagnosis of lymphatic diseases, new imaging agents for assessing lymphatic architecture and cancer status of lymph nodes, and emerging near-infrared (NIR) fluorescent optical imaging technologies and agents for functional lymphatic imaging. Given the promise of NIR optical imaging, we provide example results of functional lymphatic imaging in mice, swine, and humans, showing the ability of this technology to quantify lymph velocity and frequencies of propulsion resulting from the contractility of lymphatic structures.

Sentinel lymph node detection in skin cancer patients using real-time fluorescence navigation with indocyanine green: preliminary experience

BACKGROUND

Sentinel lymph node (SLN) biopsy has become the most widely used procedure to determine the regional lymph node status of patients with cutaneous malignant melanoma, and its application has spread rapidly to other malignancies such as squamous cell carcinoma of the skin, breast cancer and gastric cancer.

OBJECTIVE

SLN detection was performed in skin cancer patients using a newly developed real-time fluorescence navigation system with indocyanine green (ICG).

METHODS

SLN biopsy was performed by this method in 10 skin cancer patients (seven with melanoma and three with squamous cell carcinoma). After ICG was injected intradermally around the tumours, the lymphatic drainage was detected and the SLNs were identified by real-time fluorescence imaging.

RESULTS

The SLNs and their associated subcutaneous lymphatics were successfully identified in all patients. Fluorescence from SLNs was detected by this system for at least 3 hours after the injection of ICG.

CONCLUSION

SLN biopsy using ICG fluorescence achieves a high identification rate and allows effective observation for several hours. This method may become a useful option for the detection of SLNs in patients with skin cancer.

Detection of sentinel node in gastric cancer surgery by indocyanine green fluorescence imaging: comparison with infrared imaging

BACKGROUND

Secure methods for clinical detection of the sentinel node (SN) are in great demand to avoid unnecessary resection. This was a clinical exploration/feasibility study of a novel detection system for SN biopsy using indocyanine green (ICG) fluorescence imaging in gastric cancer surgery.

METHODS

SN biopsy using ICG dye was performed in three patients who had gastric cancer. ICG fluorescence images were obtained using a detection system comprising a charge-coupled device (CCD) camera with a cut filter as the detector and light emitting diodes (LED) as the light source. The nodes were also examined simultaneously by an infrared (IR) imaging videoscope.

RESULTS

Immediately after intraoperative ICG injection, the fluorescence imaging system allowed easy visualization of the lymphatic vessels draining from the primary gastric tumor toward the lymph nodes and tracing of the moving injected dye. Some lymph vessels and nodes were hardly recognized by ICG green color or IR imaging. The ICG fluorescence system also allowed visualization of the lymph node when ICG was injected the day before surgery, similar to the radio-guided method.

CONCLUSIONS

Detection of SNs in gastric cancer surgery using the ICG fluorescence imaging system is a promising novel technique and may perhaps prove useful for laparoscopic surgery.

Intraoperative identification of sentinel lymph nodes by near-infrared fluorescence imaging in patients with breast cancer

We present a novel method for sentinel lymph node (SLN) identification by fluorescence imaging that provides a high detection rate and a low false-negativity rate. Twenty-five breast cancer patients with tumors less than 3 cm in diameter were enrolled. A combination of indocyanine green and indigo carmine was injected subdermally in the areola. Subcutaneous lymphatic channels draining from the areola to the axilla were immediately showed by fluorescence imaging. After incising the axillary skin near the point of disappearance of the fluorescence, the SLN was dissected under fluorescence guidance. In all patients, the lymphatic channels and SLN were successfully visualized. The mean number of fluorescent SLN and blue-dyed SLN were 5.5 and 2.3. Eight patients were found to have lymph node metastases pathologically. All of them were recognized by fluorescence imaging. This method is feasible and safe for intraoperative detection of SLN allowing real-time observation without any need for training.

Imaging of lymph flow in breast cancer patients after microdose administration of a near-infrared fluorophore: feasibility study

PURPOSE

To prospectively demonstrate the feasibility of using indocyanine green, a near-infrared (NIR) fluorophore at the minimum dose needed for noninvasive optical imaging of lymph nodes (LNs) in breast cancer patients undergoing sentinel lymph node mapping (SLNM).

MATERIALS AND METHODS

Informed consent was obtained from 24 women (age range, 30-85 years) who received intradermal subcutaneous injections of 0.31-100 microg indocyanine green in the breast in this IRB-approved, HIPAA-compliant, dose escalation study to find the minimum microdose for imaging. The breast, axilla, and sternum were illuminated with NIR light and the fluorescence generated in the tissue was collected with an NIR-sensitive intensified charged-coupled device. Lymphoscintigraphy was also performed. Resected LNs were evaluated for the presence of radioactivity, blue dye accumulation, and fluorescence. The associations between the resected LNs that were fluorescent and (a) the time elapsed between NIR fluorophore administration and resection and (b) the dosage of NIR fluorophores were tested with the Spearman rank and Pearson product moment correlation tests, respectively.

RESULTS

Lymph imaging consistently failed with indocyanine green microdosages between 0.31 and 0.77 microg. When indocyanine green dosages were 10 microg or higher, lymph drainage pathways from the injection site to LNs were imaged in eight of nine women; lymph propulsion was observed in seven of those eight. When propulsion in the breast and axilla regions was present, the mean apparent velocities ranged from 0.08 to 0.32 cm/sec, the time elapsed between "packets" of propelled fluid varied from 14 to 92 seconds. In patients who received 10 microg of indocyanine green or more, a weak negative correlation between the fluorescence status of resected LNs and the time between NIR fluorophore administration and LN resection was found. No statistical association was found between the fluorescence status of resected LNs and the dose of NIR fluorophore.

CONCLUSION

NIR fluorescence imaging of lymph function and LNs is feasible in humans at microdoses that would be needed for future molecular imaging of cancer-positive LNs.

Novel lymphography using indocyanine green dye for near-infrared fluorescence labeling

Lymphedema is known to be caused by many pathologic conditions; however, its diagnostic and therapeutic strategies remain to be unestablished. In this study, we investigated the usefulness of a novel lymphographic method based on fluorometric sensing using indocyanine green (ICG) dye for imaging lymphatic vessels using rat models. The real-time imaging system enabled visualization of superficial lymphatic vessels with a diameter of 0.1 mm in 33 frames/second. In addition, morphologic changes in lymphatic vessels in a radiation-induced lymphedema model were detected even at the latent stage. These results suggest that this imaging technique is acceptable as an evaluation method for the lymphatic system.

Intraoperative Lymphography Using Indocyanine Green Dye for Near-Infrared Fluorescence Labeling in Lymphedema

A new method for easy detection of functional lymphatic vessels in the superficial layer is reported. In a clinical trial, lymphography using indocyanine green dye for near-infrared fluorescence labeling in lymphaticovenular anastomoses was performed in 5 patients with lymphedema. The technique is simple and enables a minimally invasive operation to be performed. The results indicate that this technique is useful for acceptance as one of the examinations to evaluation of lymphedema.

Preliminary experience with a novel fluorescence lymphography using indocyanine green in patients with secondary lymphedema

BACKGROUND

Lymphoscintigraphy has largely been performed to diagnose lymphedema. It is, however a time-consuming and expensive technique, which has not been covered by Japanese medical insurance since the year 2002. In this report we introduce a new imaging technique of fluorescent lymphography to diagnose lymphedema.

METHODS

Fluorescence images of subcutaneous lymphatic drainage after subcutaneous injection of indocyanine green (ICG) at the foot were obtained using a newly developed near-infrared camera system. ICG fluorescent lymphography was performed in 12 patients with secondary lymphedema and 10 healthy volunteers. The 12 patients were diagnosed with secondary lymphedema according to the medical history and lymphoscintigram, of which 11 had a history of hysterectomy with extended lymph node dissection and local radiation therapy for uterine cancer. Lymphedema developed in one patient after femorotibial artery bypass for peripheral artery occlusive disease.

RESULTS

Four abnormal fluorescent patterns of the lymph drainage were observed in lymphedema: dermal backflow (an abnormal filling of the lymph capillaries), extended fluorescent signal at the dorsum and plantar region of the foot, dilated lymph channels with proximal obliteration, and diffuse glittering of fluorescent signals with scattered twinkling of the dye. Continuous lymph channels from the injection site of the foot to the groin were observed along the medial aspect of thigh in healthy subjects.

CONCLUSION

ICG fluorescence lymphography is safe, simple, and minimally invasive. The device is portable and easy to use. The technique may be useful in clinical practice to identify presence of lymphatic disorder.

Advances in small animal mesentery models for in vivo flow cytometry, dynamic microscopy, and drug screening

Using animal mesentery with intravital optical microscopy is a well-established experimental model for studying blood and lymph microcirculation in vivo. Recent advances in cell biology and optical techniques provide the basis for extending this model for new applications, which should generate significantly improved experimental data. This review summarizes the achievements in this specific area, including in vivo label-free blood and lymph photothermal flow cytometry, super-sensitive fluorescence image cytometry, light scattering and speckle flow cytometry, microvessel dynamic microscopy, infrared (IR) angiography, and high-speed imaging of individual cells in fast flow. The capabilities of these techniques, using the rat mesentery model, were demonstrated in various studies; e.g., real-time quantitative detection of circulating and migrating individual blood and cancer cells, studies on vascular dynamics with a focus on lymphatics under normal conditions and under different interventions (e.g. lasers, drugs, nicotine), assessment of lymphatic disturbances from experimental lymphedema, monitoring cell traffic between blood and lymph systems, and high-speed imaging of cell transient deformability in flow. In particular, the obtained results demonstrated that individual cell transportation in living organisms depends on cell type (e.g., normal blood or leukemic cells), the cell’s functional state (e.g., live, apoptotic, or necrotic), and the functional status of the organism. Possible future applications, including in vivo early diagnosis and prevention of disease, monitoring immune response and apoptosis, chemo- and radio-sensitivity tests, and drug screening, are also discussed.