Near-infrared Fluorescent Light Research Articles

Suprapancreatic Lymph Nodes Dissection Using a Novel Multijoint Articulating Instrument and Simultaneous Near-Infrared Image in Patient with Gastric Cancer

Introduction: Optical imaging using near-infrared (NIR) fluorescence is now actively used to observe structures during real-time surgery. The advantages of NIR fluorescent light (700–900 nm) include high tissue penetration and low autofluorescence, which enable sufficient contrast.1 Lymph node dissection along the suprapancreatic area (e.g., nodes 7, 8a, 9, 11p, and 12a) during laparoscopic gastrectomy remains challenging even for an experienced surgeon. Fluorescent lymphography may be useful for performing a complete lymphadenectomy by assessing the adequacy of lymphadenectomy in real time.2 To facilitate this procedure, a sophisticated articulation device was used with NIR fluorescence imaging guidance.3 Materials and Methods: A 54-year-old man was found to have gastric adenocarcinoma located at the midbody along the lesser curvature of the stomach. An abdominal computed tomography scan revealed clinical stage T2N1M0. No metastatic lesions were found on preoperative testing. Laparoscopic distal gastrectomy was performed with a D2 lymph node dissection. The laparoscopic articulating instrument with a multijointed structure that synchronized with the surgeon's hand, wrist, and finger movements was used to facilitate the lymph node dissection. Of note, indocyanine green was injected submucosally at four sites around the cancerous tissues during intraoperative endoscopy before the lymph node dissection. Results: The operating time was 150 minutes, and the estimated blood loss was 30 mL. The patient recovered well, and he was started on a liquid diet on postoperative day 3. He was discharged on postoperative day 6 without any complications. The final pathologic report revealed that 45 lymph nodes had been retrieved and 2 were metastatic. He received adjuvant therapy and is alive at 1.6 years follow-up without recurrence. Conclusion: The suprapancreatic lymph node dissection procedure can be accomplished by using a novel multijointed articulating instrument and simultaneous NIR imaging in a patient with gastric cancer. No competing financial interests exist. Runtime of video: 7 mins 41 secs

Near-infrared diffuse in vivo flow cytometry.

.SignificanceDiffuse in vivo flow cytometry (DiFC) is an emerging technique for enumerating rare fluorescently labeled circulating cells noninvasively in the bloodstream. Thus far, we have reported red and blue-green versions of DiFC. Use of near-infrared (NIR) fluorescent light would in principle allow use of DiFC in deeper tissues and would be compatible with emerging NIR fluorescence molecular contrast agents.AimWe describe the design of a NIR-DiFC instrument and demonstrate its use in optical flow phantoms in vitro and in mice in vivo.ApproachWe developed an improved optical fiber probe design for efficient collection of fluorescence from individual circulating cells and efficient rejection of instrument autofluorescence. We built a NIR-DiFC instrument. We tested this with NIR fluorescent microspheres and cell lines labeled with OTL38 fluorescence contrast agent in a flow phantom model. We also tested NIR-DiFC in nude mice injected intravenously with OTL38-labeled L1210A cells.ResultsNIR-DiFC allowed detection of circulating tumor cells (CTCs) in flow phantoms with mean signal-to-noise ratios (SNRs) of 19 to 32 dB. In mice, fluorescently labeled CTCs were detectable with mean SNR of 26 dB. NIR-DiFC also exhibited orders significantly lower autofluorescence and false-alarm rates than blue-green DiFC.ConclusionsNIR-DiFC allows use of emerging NIR contrast agents. Our work could pave the way for future use of NIR-DiFC in humans.

Intravascular Fluorescence Molecular Imaging of Atherosclerosis.

Optical molecular imaging using near-infrared fluorescence (NIRF) light is an emerging high-resolution imaging approach to image a wide range of molecular and cellular species in vivo. Imaging using NIR wavelengths (650-900nm) enables deeper photon penetration into tissue and reduced tissue autofluorescence, resulting in higher sensitivity to detect exogenously administered NIR fluorophores (injectable molecular imaging agents). Greater imaging depth of several centimeters is further achievable in the NIR window as blood absorption is as an order of magnitude lower than in the visible range. Furthermore, as optical imaging is routinely performed in the cardiac catheterization laboratory (e.g., optical coherence tomography), intravascular NIRF offers a promising translational approach for clinical coronary and peripheral arterial imaging. To this point, the first human intravascular NIRF imaging study recently demonstrated the ability to detect NIR autofluorescence in patients with coronary atherosclerosis. This study provides a foundation for targeted intravascular NIRF molecular imaging studies in coronary patients. In this chapter, we detail system engineering, imaging agents and translational applications of intravascular NIRF molecular imaging.

Synthesis and Bioapplications of Ag2 S Quantum Dots with Near-Infrared Fluorescence.

Quantum dots (QDs) with near-infrared fluorescence (NIR) are an emerging class of QDs with unique capabilities owing to the deeper tissue penetrability of NIR light compared with visible light. NIR light also effectively overcomes organism autofluorescence, making NIR QDs particularly attractive in biological imaging applications for disease diagnosis. Considering latest developments, Ag2 S QDs are a rising star among NIR QDs due to their excellent NIR fluorescence properties and biocompatibility. This review presents the various methods to synthesize NIR Ag2 S QDs, and systematically discusses their applications in biosensing, bioimaging, and theranostics. Major challenges and future perspectives concerning the synthesis and bioapplications of NIR Ag2 S QDs are discussed.

Downshifting nanoprobes with follicle stimulating hormone peptide fabrication for highly efficient NIR II fluorescent bioimaging guided ovarian tumor surgery

Failure of intraoperative detection, early minimal lesion and microscopic residual tumor margins elimination causes metastatic diffusion and lethal recurrence. However, during surgical process, surgeons can only rely largely on palpation and visual examination. Intraoperative bioimaging with the aid of the second near-infrared fluorescent (NIR II FL) light has entered the surgical excision area to bridge the gap of preoperative bioimaging and intraoperative resection. Here, we demonstrate that the follicle-stimulating hormone peptide (FSHP) engineered NIR II downshifting nanoparticles (DSNPs@FSHP) selectively undergo efficient ovarian tumor targeting property. Owing to the special biocompatibility of nanoprobes, this strategy provided rapid body clearance and efficient tumor targeting with significantly tumor to background (T/B) ratio enhanced for surgical excision. Based on these, this strategy can successfully empower the detection and surgical removal for both ovarian tumor lesions and ovarian tumor margins by NIR II FL bioimaging.

Real-time Indocyanine Green Videolymphography Navigation for Lymphaticovenular Anastomosis

Summary:Indocyanine green (ICG) lymphography is a useful imaging modality for evaluation of lymphedema and detection of lymphatic vessels. It also allows us to ensure patency of the anastomosed vessels intraoperatively. However, strong light from the operating microscope usually disturbs ICG fluorescence imaging. Only some built-in ICG camera systems with specific operating microscopes make real-time ICG lymphography possible in lymphaticovenular anastomosis (LVA). We applied a new high-resolution ICG videolymphography system, which is separated from the operating microscope. Because the system can divide near-infrared fluorescence light of ICG from visible light of the operating microscope, real-time ICG videolymphography-navigated LVA under operating microscope illumination is possible regardless types of operating microscopes. The study involved 10 patients with upper extremity lymphedema characterized by International Society of Lymphology stage 2 and treated by 3 lymphaticovenular anastomoses at the forearm (30 lymphaticovenular anastomoses incorporating 30 lymphatic vessels) under real-time ICG videolymphography. The rate of intraoperative detection of lymphatic vessels using real-time ICG videolymphography was 86.7% (0.25–0.85 mm in diameter), and that of lymph flow through the lymphaticovenular anastomoses was 76.7%. None of lymphatic vessels and no flow were detected under the microscope light by means of another non-built-in ICG lymphography camera. Real-time ICG videolymphography in LVA is beneficial, because the surgeon could find lymphatic vessels easily by checking dual images of original view and ICG fluorescent view and ensure accuracy of the LVA in a suture by a suture without any pauses of the surgical procedures.

Intraoperative localization of insulinoma using invisible near-infrared fluorescent light. Report of 3 cases

The combination of PET and MRI is one of the recent advances of hybrid imaging. Yet to date, the adoption rate of PET/MRI systems has been rather slow. This seems to be partially caused by the high costs of PET/MRI systems and the need to verify an incremental benefit over PET/CT or sequential PET/CT and MRI.In analogy to PET/CT, the MRI part of PET/MRI was primarily used for anatomical imaging. Though this can be advantageous, for example in diseases where the superior soft tissue contrast of MRI is highly appreciated, the sole use of MRI for anatomical orientation lessens the potential of PET/MRI. Consequently, more recent studies focused on its multiparametric potential and employed diffusion weighted sequences and other functional imaging sequences in PET/MRI. This integration puts the focus on a more wholesome approach to PET/MR imaging, in terms of releasing its full potential for local primary staging based on multiparametric imaging and an included one-stop shop approach for whole-body staging. This approach as well as the implementation of computational analysis, in terms of radiomics analysis, has been shown valuable in several oncological diseases, as will be discussed in this review article.

Bioimaging of botulinum toxin and hyaluronate hydrogels using zwitterionic near-infrared fluorophores

BackgroundThe injection of botulinum toxin (BTX) to reduce facial wrinkles is one of the most frequently performed plastic surgery procedures. The biocompatible hydrogels are injected with BTX for effective tissue augmentation. However, it is difficult to determine the interval of injection for effective tissue augmentation.MethodBTX and hyaluronate (HA) hydrogels were labeled with zwitterionic (ZW) near-infrared (NIR) fluorophores and visualized for 3 weeks after injection to BALB/c nude mice.ResultsBTX-ZW conjugates and diaminohexane (DAH)-HA-ZW hydrogels were successfully prepared by the conventional EDC/NHS chemistry. Using the NIR fluorescence imaging, we confirmed that approximately 10% of BTX-ZW conjugates and 50% of DAH-HA-ZW hydrogels remained 3 weeks post-injection.ConclusionThis bioimaging technique using invisible NIR fluorescence light can be exploited for various biomedical applications.

Near Infrared Fluorescence Imaging in Nano-Therapeutics and Photo-Thermal Evaluation.

The unresolved and paramount challenge in bio-imaging and targeted therapy is to clearly define and demarcate the physical margins of tumor tissue. The ability to outline the healthy vital tissues to be carefully navigated with transection while an intraoperative surgery procedure is performed sets up a necessary and under-researched goal. To achieve the aforementioned objectives, there is a need to optimize design considerations in order to not only obtain an effective imaging agent but to also achieve attributes like favorable water solubility, biocompatibility, high molecular brightness, and a tissue specific targeting approach. The emergence of near infra-red fluorescence (NIRF) light for tissue scale imaging owes to the provision of highly specific images of the target organ. The special characteristics of near infra-red window such as minimal auto-fluorescence, low light scattering, and absorption of biomolecules in tissue converge to form an attractive modality for cancer imaging. Imparting molecular fluorescence as an exogenous contrast agent is the most beneficial attribute of NIRF light as a clinical imaging technology. Additionally, many such agents also display therapeutic potentials as photo-thermal agents, thus meeting the dual purpose of imaging and therapy. Here, we primarily discuss molecular imaging and therapeutic potentials of two such classes of materials, i.e., inorganic NIR dyes and metallic gold nanoparticle based materials.

Tissue-Specific Near-Infrared Fluorescence Imaging.

Near-infrared (NIR) fluorescence light has been widely utilized in clinical imaging by providing surgeons highly specific images of target tissue. The "NIR window" from 650 to 900 nm is especially useful due to several special features such as minimal autofluorescence and absorption of biomolecules in tissue, as well as low light scattering. Compared with visible wavelengths, NIR fluorescence light is invisible, thus allowing highly sensitivity real-time image guidance in human surgery without changing the surgical field. The benefit of using NIR fluorescence light as a clinical imaging technology can be attributed to its molecular fluorescence as an exogenous contrast agent. Indeed, whole body preoperative imaging of single-photon emission computed tomography (SPECT) and positron emission tomography (PET) remains important in diagnostic utility, but they lack the efficacy of innocuous and targeted NIR fluorophores to simultaneously facilitate the real-time delineation of diseased tissue while preserving vital tissues. Admittedly, NIR imaging technology has been slow to enter clinical use mostly due to the late-coming development of truly breakthrough contrast agents for use with current imaging systems. Therefore, clearly defining the physical margins of tumorous tissue remains of paramount importance in bioimaging and targeted therapy. An equally noteworthy yet less researched goal is the ability to outline healthy vital tissues that should be carefully navigated without transection during the intraoperative surgery. Both of these paths require optimizing a gauntlet of design considerations to obtain not only an effective imaging agent in the NIR window but also high molecular brightness, water solubility, biocompatibility, and tissue-specific targetability. The imaging community recognizes three strategic approaches which include (1) passive targeting via the EPR effect, (2) active targeting using the innate overall biodistribution of known molecules, and (3) activatable targeting through an internal stimulus, which turns on fluorescence from an off state. Recent advances in nanomedicine and bioimaging offer much needed promise toward fulfilling these stringent requirements as we develop a successful catalog of targeted contrast agents for illuminating both tumors and vital tissues in the same surgical space by employing spectrally distinct fluorophores in real time. These tissue-specific contrast agents can be versatile arsenals to physicians for real-time intraoperative navigation as well as image-guided targeted therapy. There is a versatile library of tissue-specific fluorophores available in the literature, with many discussed herein, which offers clinicians an array of possibilities that will undoubtedly improve intraoperative success and long-term postoperation prognosis.

Sentinel Lymph Node Mapping of Liver.

Although the sentinel lymph node (SLN) hypothesis has been applied to many tissues and organs, liver has remained unstudied. Currently, it is unclear whether hepatic SLNs even exist. If so, they could alter the management of intrahepatic cholangiocarcinoma and other hepatic malignancies by minimizing the extent of surgery while still providing precise nodal staging. This study investigated whether invisible yet tissue-penetrating near-infrared (NIR) fluorescent light can provide simultaneous identification of both the SLN and all other regional lymph nodes (RLNs) in the liver. In 25 Yorkshire pigs, this study determined whether SLNs exist in liver and compared the effectiveness of two clinically available NIR fluorophores [methylene blue and indocyanine green (ICG)], and two novel NIR fluorophores previously described by our group (ESNF14 and ZW800-3C) for SLN and RLN mapping. In this study, ESNF14 showed the highest signal-to-background ratio and the longest retention time in SLNs without leakage to second-tier lymph nodes. The findings showed that ICG had apparent leakage to second-tier nodes, and ZW800-3C had poor migration after intraparenchymal injection. However, when injected intravenously, ZW800-3C was able to highlight all RLNs in liver during a 4- to 6-h period. Simultaneous dual-channel imaging of SLN (ESNF14) and RLN (ZW800-3C) permitted unambiguous identification and image-guided resection of SLNs and RLNs in liver. The NIR imaging technology enables real-time intraoperative identification of SLNs and RLNs in the liver of swine. If these results are confirmed in patients, new strategies for the surgical management of intrahepatic malignancies should be possible.

Abstract 2055: Modulated near-infrared fluorescence light imaging of primary tumor margins, cancer positive lymph nodes, and freshly excised human cancers with imaging agent targeting EpCAM

Abstract We developed an epithelial cancer-specific, imaging agent labeled for near-infrared florescence (NIRF) imaging together with an intraoperative surgical device for sensitive detection of tumor margins and local metastatic lesions within the surgical field of view. The drug/device combination was tested on an orthotopic model and on freshly resected, human cancerous tissues. To maximize device performance, we illuminated tissue surfaces with modulated near-infrared (NIR) excitation light (785 nm) and collected fluroescent light (830 nm) via using a NIR sensitive image intensifier modulated at with 90 degree phase delays added between 3 consecutively acquired images. These phase-delayed images were collected by a CCD and processed in near-real time to provide images of fluroescence amplitude with significantly higher contrast and without significant reduction in signal to noise ratio as compared to conventional images acquired without modulation. To develop a universal imaging agent for use with the device, a high affinity monoclonal antibody (mAb) against epithelial cell adhesion molecule (EpCAM) was selected from a previously generated panel and labeled with NIRF dye, IRDye800. The labeled mAb was characterized for conserved biological activity. Upon dual-labeling this lead mAb candidate for both PET and NIRF, we showed the accuracy of planar NIRF imaging (96%) to be superior to PET (93%) for detecting cancer positive lymph nodes 24 hours following 40 ug i.v. injection in an orthotopic model of PC3 human metastatic prostate cancer 10-12 weeks post-implantation. Compared to NIRF labeled isotype control mAb, the labeled anti-EpCAM mAb accurately detected primary tumor margins as indicated by both pathology and far-red fluorescent protein reporter, iRFP (excitation 690 nm/ emission 720 nm), that was stably expressed in implanted PC3 cells. Furthermore, modulated light imaging provided greater accuracy in detecting margins compared to the widely used conventional fluorescent collection techniques. Upon immersing freshly excised human squamous cell carcinoma tissues from individual patients in dilute solutions of labeled anti-EpCAM and labeled isotype control and rinsing, we used the device to demonstrate consistent and specific binding of labeled anti-EpCAM mAb to cancer sites. In addition, cancer margins detected by NIRF were pathologically confirmed. When combined with a high-affinity imaging agent targeting an antigen overexpressed on nearly all epithelial cancers, NIRF imaging can be used to accurate detect margins as well as cancer positive LNs. Finally, the modulated NIRF imaging can be deployed for open surgeries as well as endoscopic and robotic surgeries wherein surgical field illumination would otherwise destroy molecular imaging contrast. Citation Format: Banghe Zhu, Barrett Harvey, Melissa Aldrich, Grace Wu, Nathaniel Wilganowski, Holly Robinson, Kenneth Pinkston, Gao Peng, Songlin Zhang, Ron Karni, Eva M. Sevick-Muraca. Modulated near-infrared fluorescence light imaging of primary tumor margins, cancer positive lymph nodes, and freshly excised human cancers with imaging agent targeting EpCAM. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2055. doi:10.1158/1538-7445.AM2014-2055

Prototype nerve-specific near-infrared fluorophores.

Nerve preservation is an important issue during most surgery because accidental transection or injury results in significant morbidity, including numbness, pain, weakness, or paralysis. Currently, nerves are still identified only by gross appearance and anatomical location during surgery, without intraoperative image guidance. Near-infrared (NIR) fluorescent light, in the wavelength range of 650-900 nm, has the potential to provide high-resolution, high-sensitivity, and real-time avoidance of nerve damage, but only if nerve-specific NIR fluorophores can be developed. In this study, we evaluated a series of Oxazine derivatives to highlight various peripheral nerve structures in small and large animals. Among the targeted fluorophores, Oxazine 4 has peak emission near into the NIR, which provided nerve-targeted signal in the brachial plexus and sciatic nerve for up to 12 h after a single intravenous injection. In addition, recurrent laryngeal nerves were successfully identified and highlighted in real time in swine, which could be preserved during the course of thyroid resection. Although optical properties of these agents are not yet optimal, chemical structure analysis provides a basis for improving these prototype nerve-specific NIR fluorophores even further.

Image-guided cancer surgery using near-infrared fluorescence

Paradigm shifts in surgery arise when surgeons are empowered to perform surgery faster, better and less expensively than current standards. Optical imaging that exploits invisible near-infrared (NIR) fluorescent light (700-900 nm) has the potential to improve cancer surgery outcomes, minimize the time patients are under anaesthesia and lower health-care costs largely by way of its improved contrast and depth of tissue penetration relative to visible light. Accordingly, the past few years have witnessed an explosion of proof-of-concept clinical trials in the field. In this Review, we introduce the concept of NIR fluorescence imaging for cancer surgery, examine the clinical trial literature to date and outline the key issues pertaining to imaging system and contrast agent optimization. Although NIR seems to be superior to many traditional imaging techniques, its incorporation into routine care of patients with cancer depends on rigorous clinical trials and validation studies.

Image‐guided hepatopancreatobiliary surgery using near‐infrared fluorescent light

BackgroundImproved 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.MethodsThis article reviews the published literature related to preclinical development and clinical applications of NIR fluorescence imaging during HPB surgery.ResultsNIR 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.ConclusionsNIR fluorescence imaging is a promising new technique that may someday improve surgical accuracy and lower complications.

Aqueous CdPbS quantum dots for near-infrared imaging

Quantum dots (QDs) are semiconducting nanocrystals that have photoluminescent (PL) properties brighter than fluorescent molecules and do not photo-bleach, ideal for in vivo imaging of diseased tissues or monitoring of biological processes. Near-infrared (NIR) fluorescent light within the window of 700–1000 nm, which is separated from the major absorption peaks of hemoglobin and water, has the potential to be detected several millimeters under the surface with minimal interference from tissue autofluorescence. Here we report the synthesis and bioimaging demonstration of a new NIR QDs system, namely, CdPbS, made by an aqueous approach with 3-mercaptopropionic acid (MPA) as the capping molecule. The aqueous-synthesized, MPA-capped CdPbS QDs exhibited an NIR emission in the range of 800–950 nm with xi ≥ 0.3, where xi denotes the initial Pb molar fraction during the synthesis. Optimal PL performance of the CdPbS QDs occurred at xi = 0.7, which was about 4 nm in size as determined by transmission electron microscopy, had a rock salt structure and a quantum yield of 12%. Imaging of CdPbS QDs was tested in membrane staining and transfection studies. Cells transfected with CdPbS QDs were shown to be visible underneath a slab of chicken muscle tissue of up to 0.7 mm in thickness without the use of multiple-photon microscopy.

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.

A Near-Infrared Optomechanical Intracranial Pressure Microsensor

We present a wireless and power-free, optomechanical, implantable microsensor that can potentially be used to accurately monitor intracranial pressure (ICP) over long periods of time. The developed microsensor vertically integrates a glass mini-lens with a two-wavelength quantum dot (QD) micropillar that is photolithographically patterned on an ICP-exposed silicon nitride membrane. The operation principle is based on a novel optomechanical transduction scheme that converts ICP changes into changes in the intensity ratio of the two-wavelength, near-infrared fluorescent light emitted from the QDs. The microsensor is microfabricated using silicon bulk micromachining, and it operates at an ICP clinically relevant pressure dynamic range (0-40 mmHg). The microsensor has a maximum error of less than 15% throughout its dynamic range, and it is extremely photostable. We believe that the proposed microsensor will open up a new direction not only in ICP monitoring but in other pressure-related biomedical applications.

A three-dimensional finite element model and image reconstruction algorithm for time-domain fluorescence imaging in highly scattering media

In this work, development and evaluation of a three-dimensional (3D) finite element model (FEM) based on the diffusion approximation of time-domain (TD) near-infrared fluorescence light transport in biological tissue is presented. This model allows both excitation and fluorescence temporal point-spread function (TPSF) data to be generated for heterogeneous scattering and absorbing media of arbitrary geometry. The TD FEM is evaluated via comparisons with analytical and Monte Carlo (MC) calculations and is shown to provide a quantitative accuracy which has less than 0.72% error in intensity and less than 37 ps error for mean time. The use of the Born–Ratio normalized data is demonstrated to reduce data mismatch between MC and FEM to less than 0.22% for intensity and less than 22 ps in mean time. An image reconstruction framework, based on a 3D FEM formulation, is outlined and simulation results based on a heterogeneous mouse model with a source of fluorescence in the pancreas is presented. It is shown that using early photons (i.e. the photons detected within the first 200 ps of the TPSF) improves the spatial resolution compared to using continuous-wave signals. It is also demonstrated, as expected, that the utilization of two time gates (early and latest photons) can improve the accuracy both in terms of spatial resolution and recovered contrast.

Real-Time Simultaneous Near-Infrared Fluorescence Imaging of Bile Duct and Arterial Anatomy

We hypothesized that two independent wavelengths of near-infrared (NIR) fluorescent light could be used to identify bile ducts and hepatic arteries simultaneously, and intraoperatively. Three different combinations of 700 and 800 nm fluorescent contrast agents specific for bile ducts and arteries were injected into N = 10 35-kg female Yorkshire pigs intravenously. Combination 1 (C-1) was methylene blue (MB) for arterial imaging and indocyanine green (ICG) for bile duct imaging. Combination 2 (C-2) was ICG for arterial imaging and MB for bile duct imaging. Combination 3 (C-3) was a newly developed, zwitterionic NIR fluorophore ZW800-1 for arterial imaging and MB for bile duct imaging. Open and minimally invasive surgeries were imaged using the fluorescence-assisted resection and exploration (FLARE) surgical imaging system and minimally invasive FLARE (m-FLARE) imaging systems, respectively. Although the desired bile duct and arterial anatomy could be imaged with contrast-to-background ratios (CBRs) ≥ 6 using all three combinations, each one differed significantly in terms of repetition and prolonged imaging. ICG injection resulted in high CBR of the liver and common bile duct (CBD) and prolonged imaging time (120 min) of the CBD (C-1). However, because ICG also resulted in high background of liver and CBD relative to arteries, ICG produced a lower arterial CBR (C-2) at some time points. C-3 provided the best overall performance, although C-2, which is clinically available, did enable effective laparoscopy. We demonstrate that dual-channel NIR fluorescence imaging provides simultaneous, real-time, and high resolution identification of bile ducts and hepatic arteries during biliary tract surgery.