Pharmacokinetic-rate images of indocyanine green for breast tumors using near-infrared optical methods

Fluorescence imaging for real-time detection of breast cancer tumors using IV injection of indocyanine green with non-conventional imaging: a systematic review of preclinical and clinical studies of perioperative imaging technologies

BACKGROUND

This review summarizes the available data on the effectiveness of indocyanine green fluorescence imaging (ICG-FI) for real-time detection of breast cancer (BC) tumors with perioperative imaging technologies.

METHODS

PubMed and Scopus databases were exhaustively searched for publications on the use of the real-time ICG-FI evaluation of BC tumors with non-conventional breast imaging technologies.

RESULTS

Twenty-three studies were included in this review. ICG-FI has been used for BC tumor identification in 12 orthotopic animal tumor experiences, 4 studies on animal assessment, and for 7 human clinical applications. The BC tumor-to-background ratio (TBR) was 1.1-8.5 in orthotopic tumor models and 1.4-3.9 in animal experiences. The detection of primary human BC tumors varied from 40% to 100%. The mean TBR reported for human BC varied from 2.1 to 3.7. In two studies evaluating BC surgical margins, good sensitivity (93.3% and 100%) and specificity (60% and 96%) have been reported, with a negative predictive value of ICG-FI to predict margin involvement intraoperatively of 100% in one study.

CONCLUSIONS

The use of ICG-FI as a guiding tool for the real-time identification of BC tumors and for the assessment of tumor boundaries is promising. There is great variability between the studies with regard to timing and dose. Further evidence is needed to assess whether ICG-guided BC surgery may be implemented as a standard of care.

High-sensitivity dynamic diffuse fluorescence tomography system for fluorescence pharmacokinetics

SIGNIFICANCE

Dynamic diffuse fluorescence tomography (DFT) can recover the static distribution of fluorophores and track dynamic temporal events related to physiological and disease progression. Dynamic imaging indocyanine green (ICG) approved by the food and drug administration is still under-exploited because of its characteristics of low quantum yield and relatively rapid tissue metabolism.

AIM

In order to acquire the ICG tomographic image sequences for pharmacokinetic analysis, a dynamic DFT system was proposed.

APPROACH

A fiber-based dynamic DFT system adopts square-wave modulation lock-in photon-counting scheme and series-parallel measurement mode, which possesses high sensitivity, large dynamic range, high anti-ambient light ability in common knowledge, as well as good cost performance. In order to investigate the effectiveness of the proposed system, the measurement stability and the anti-crosstalk-a crucial factor affecting the system parallelization-were assessed firstly, then a series of static phantoms, dynamic phantoms and in vivo mice experiments were conducted to verify the imaging capability.

RESULTS

The system has the limited dynamic range of 100 dB, the fluctuation of photon counting within 3%, and channel-to-channel crosstalk ratio better than 1.35. Under the condition of a sufficient signal-to-noise ratio, a complete measurement time for one frame image was 10.08 s. The experimental results of static phantoms with a single target and three targets showed that this system can accurately obtain the positions, sizes, and shapes of the targets and the reconstructed images exhibited a high quantitativeness. Further, the self-designed dynamic phantom experiments demonstrated the capability of the system to capture fast changing fluorescence signals. Finally, the in vivo experiments validated the practical capability of the system to effectively track the ICG metabolism in living mice.

CONCLUSIONS

These results demonstrate that our proposed system can be utilized for assessing ICG pharmacokinetics, which may provide a valuable tool for tumor detection, drug assessment, and liver function evaluation.

Optical clearing of tissues: Issues of antimicrobial phototherapy and drug delivery

This review presents principles and novelties in the field of tissue optical clearing (TOC) technology, as well as application for optical monitoring of drug delivery and effective antimicrobial phototherapy. TOC is based on altering the optical properties of tissue through the introduction of immersion optical cleaning agents (OCA), which impregnate the tissue of interest. We also analyze various methods and kinetics of delivery of photodynamic agents, nanoantibiotics and their mixtures with OCAs into the tissue depth in the context of antimicrobial and antifungal phototherapy. In vitro and in vivo studies of antimicrobial phototherapies, such as photodynamic, photothermal plasmonic and photocatalytic, are summarized, and the prospects of a new TOC technology for effective killing of pathogens are discussed.

Application of an indocyanine green-mediated fluorescence imaging navigation system in detecting mice tumors

Background

Surgical operation plays an important role in the treatment of cancer. The success of the operation lies in the complete removal of the primary and disseminated tumor tissue while preserving the normal tissue. The development of optical molecular image navigation technology has provided a new option for intraoperative tumor visualization. In this study, a fluorescence imaging navigation system was used to detect the diameter of mice tumors and provide experimental evidence for the further development of digital diagnosis and treatment equipment.

Methods

The minimum detection concentration in vitro of the fluorescence imaging navigation system for indocyanine green (ICG) was first detected, then 120 female Institute of Cancer Research (ICR) mice and 120 female BALB/c nude mice were randomly divided into three groups by weight, high-dose (H, 4 mg/kg), middle-dose (M, 2 mg/kg), and low-dose (L, 1 mg/kg) groups of ICG solution. After inoculating solid tumors, high, medium, and low doses of ICG were injected via the tail vein, and the tumor diameter was measured by a fluorescence imaging navigation system and vernier caliper within 24 hours of injection.

Results

The minimum detectable diameter of the system could reach 0.2 mm compared with the vernier caliper, and the actual measurement error was within 0.2 mm.

Conclusions

A fluorescence imaging navigation system has high accuracy and sensitivity in the application of tumor detection, which may assist the clinical diagnosis and treatment of tumors.

Pharmacokinetics of Single Domain Antibodies and Conjugated Nanoparticles Using a Hybrid near Infrared Method

Iron oxide nanoparticles and single domain antibodies from camelids (VHHs) have been increasingly recognized for their potential uses for medical diagnosis and treatment. However, there have been relatively few detailed characterizations of their pharmacokinetics (PK). The aim of this study was to develop imaging methods and pharmacokinetic models to aid the future development of a novel family of brain MRI molecular contrast agents. An efficient near-infrared (NIR) imaging method was established to monitor VHH and VHH conjugated nanoparticle kinetics in mice using a hybrid approach: kinetics in blood were assessed by direct sampling, and kinetics in kidney, liver, and brain were assessed by serial in vivo NIR imaging. These studies were performed under "basal" circumstances in which the VHH constructs and VHH-conjugated nanoparticles do not substantially interact with targets nor cross the blood brain barrier. Using this approach, we constructed a five-compartment PK model that fits the data well for single VHHs, engineered VHH trimers, and iron oxide nanoparticles conjugated to VHH trimers. The establishment of the feasibility of these methods lays a foundation for future PK studies of candidate brain MRI molecular contrast agents.

Animal Models of Metastatic Lesions to the Spine: a Focus on Epidural Spinal Cord Compression

Epidural spinal cord compression (ESCC) secondary to spine metastases is one of the most devastating sequelae of primary cancer as it may lead to muscle weakness, paresthesia, pain, and paralysis. Spine metastases occur through a multi-step process that can result in eventual ESCC; however, the lack of a preclinical model to effectively recapitulate each step of this metastatic cascade and the symptom burden of ESCC has limited our understanding of this disease process. In this review, we discuss animal models that best recapitulate ESCC; we start with a broad discussion of commonly used models of bone metastasis and end with a focused discussion of models used to specifically study ESCC. Orthotopic models offer the most authentic recapitulation of metastasis development; however, they rarely result in symptomatic ESCC and are challenging to replicate. Conversely, models that involve injection of tumor cells directly into the bloodstream or bone better mimic the symptoms of ESCC; however, they provide limited insight into the epithelial to mesenchymal transition (EMT) and natural hematogenous spread of tumor cell. Therefore, until an ideal model is created, it is critical to select an animal model that is specifically designed to answer the scientific question of interest.

Near-Infrared Fluorescence Imaging of Breast Cancer and Axillary Lymph Nodes After Intravenous Injection of Free Indocyanine Green

Background

Near-infrared fluorescence imaging (NIRFI) of breast cancer (BC) after the intravenous (IV) injection of free indocyanine green (fICG) has been reported to be feasible. However, some questions remained unclarified.

Objective

To evaluate the distribution of fICG in BC and the axillary lymph nodes (LNs) of women undergoing surgery with complete axillary LN dissection (CALND) and/or selective lymphadenectomy (SLN) of sentinel LNs (NCT no. 01993576 and NCT no. 02027818).

Methods

An intravenous injection of fICG (0.25 mg/kg) was administered to one series of 20 women undergoing treatment with mastectomy, the day before surgery in 5 (group 1) and immediately before surgery in 15 (group 2: tumor localization, 25; and pN+ CALND, 4) as well as to another series of 20 women undergoing treatment with tumorectomy (group 3). A dedicated NIR camera was used for ex vivo fluorescence imaging of the 45 BC lesions and the LNs.

Results

In group 1, two of the four BC lesions and one large pN+ LN exhibited fluorescence. In contrast, 24 of the 25 tumors in group 2 and all of the tumors in group 3 were fluorescent. The sentinel LNs were all fluorescent, as well as some of the LNs in all CALND specimens. Metastatic cells were found in the fluorescent LNs of the pN+ cases. Fluorescent BC lesions could be identified ex vivo on the surface of the lumpectomy specimen in 14 of 19 cases.

Conclusions

When fICG is injected intravenously just before surgery, BC can be detected using NIRFI with high sensitivity, with metastatic axillary LNs also showing fluorescence. Such a technical approach seems promising in the management of BC and merits further investigation.

Absence of residual fluorescence in the surgical bed at near-infrared fluorescence imaging predicts negative margins at final pathology in patients treated with breast-conserving surgery for breast cancer

INTRODUCTION

Positive margins after breast-conserving surgery (BCS) for breast cancer (BC) remain a major concern. In this study we investigate the feasibility and accuracy of indocyanine green (ICG) fluorescence imaging (FI) for the in vivo assessment of surgical margins during BCS.

MATERIALS AND METHODS

Patients with BC admitted for BCS from October 2015 to April 2016 were proposed to be included in the present study (NCT02027818). ICG (0.25 mg/kg) was intravenously injected at induction anesthesia and ICG-FI of the surgical beds was correlated with final pathology results.

RESULTS

Fifty patients consented to participate and thirty-five patients were retained for final analysis, 15 patients having been excluded for, respectively, incomplete video records data for signal to background ratio (SBR) calculation (11) and in situ tumors (4). The final pathological assessment of 35 breast specimens identified 5 (14.7%) positive margins. Intraoperative ICG-FI revealed hyperfluorescent signals in 15 (42.9%) patients and an absence of fluorescent signals in 20 (57.1%). Median SBR in patients with involved margins was 1.8 (SD 0.7) and was 1.25 (SD 0.6) in patients with clear margins (p = 0.05). The accuracy, specificity, positive and negative predictive value of ICG-FI for breast surgical margin assessment were 71%, 60%, 29% and 100%, respectively.

CONCLUSION

ICG-FI of BC surgical beds has a high negative predictive value for surgical margin assessment during BCS. The absence of residual fluorescence in the surgical bed of patients with fluorescent tumors predicts negative margins at final pathology and allows the surgeon to avoid further intraoperative analysis.

Current and future trends in photoacoustic breast imaging

Non-invasive detection of breast cancer has been regarded as the holy grail of applications for photoacoustic (optoacoustic) imaging right from the early days of re-discovery of the method. Two-and-a-half decades later we report on the state-of-the-art in photoacoustic breast imaging technology and clinical studies. Even within the single application of breast imaging, we find imagers with various measurement geometries, ultrasound detection characteristics, illumination schemes, and image reconstruction strategies. We first analyze the implications on performance of a few of these design choices in a generic imaging system, before going into detailed descriptions of the imagers. Per imaging system we present highlights of patient studies, which barring a couple are mostly in the nature of technology demonstrations and proof-of-principle studies. We close this work with a discussion on several aspects that may turn out to be crucial for the future clinical translation of the method.

In Vivo Pharmacokinetics Assessment of Indocyanine Green-Loaded Nanoparticles in Tumor Tissue with a Dynamic Diffuse Fluorescence Tomography System

PURPOSE

The purpose of this study was to show a systematic strategy for assessing the pharmacokinetics of indocyanine green (ICG)-loaded nanoparticles in the tumor tissue based on a dynamic diffuse fluorescence tomography (DFT) system.

PROCEDURES

Twelve-seven-week-old male Balb/c nude mice bearing HepG2/ADR hepatocellular carcinoma were randomly divided into four groups (n = 3 per group). Four hundred microliters of three types of ICG-loaded nanoparticles (content of ICG: 50 μg/ml) and free ICG (50 μg/ml) was intravenously injected into the mice in each group, respectively. Afterwards, the real-time tomographic images on the spatial level were acquired at 2-11 min, 30 min, 1, 2, 3, 4, 6, 8, 10, 12, and 24 h post-injection, and pharmacokinetic rates were derived for semi-quantitative assessment of the pharmacokinetics of nanoparticles at the tumor site using our proposed pharmacokinetic analysis method.

RESULTS

The results obtained from our proposed dynamic DFT experiment demonstrated the distribution of different ICG formulations on the spatial level and enabled the semi-quantitative analysis of the pharmacokinetics of nanoparticles in the tumor tissue.

CONCLUSIONS

The obtained pharmacokinetic rates effectively reflected the metabolic processes of nanoparticles in the tumor tissue, which proves to be beneficial for the development of tumor diagnosis and therapy.

Parameterized level-set based pharmacokinetic fluorescence optical tomography using the regularized Gauss-Newton filter

Pharmacokinetic tomography is emerging as an important methodology for detecting abnormalities in tissue based upon spatially varying estimation of the pharmacokinetic rates governing the leakage of an injected fluorophore between blood plasma and tissue. We present a shape-based reconstruction framework of a compartment-model based formulation of this dynamic fluorescent optical tomography problem to solve for the pharmacokinetic rates and concentrations of the fluorophore from time-varying log intensity measurements of the optical signal. The compartment-model based state variable model is set up in a radial basis function parameterized level set setting. The state (concentrations) and (pharmacokinetic) parameter estimation problem is solved with an iteratively regularized Gauss-Newton filter in a trust-region framework. Reconstructions obtained using this scheme for noisy data obtained from cancer mimicking numerical phantoms of near/sub-cm sizes show a good localization of the affected regions and reasonable estimates of the pharmacokinetic rates and concentration curves.

Optical molecular imaging for tumor detection and image-guided surgery

We have witnessed rapid development of fluorescence molecular imaging of solid tumors for cancer diagnosis and image-guided surgery in the past decade. Many biomarkers unique to cancer cells or tumor microenvironment, such as cell surface receptors, hypoxia, secreted proteases and extracellular acidosis have been characterized, and can be used to distinguish cancer from normal tissue. A variety of optical imaging probes have been developed to target these biomarkers to improve tumor contrast over the background tissue. Unlike conventional anatomical and molecular imaging technologies, fluorescent imaging method benefits from its safety, high-spatial resolution and real-time capability, and therefore, has become a highly adoptable imaging method for tumor detection and image-guided surgery in clinics. In this review, we summarize recent progress in 'always-ON' and stimuli-activatable fluorescent imaging probes, and discuss their potentials in tumor detection and image-guided surgery.

Activatable clinical fluorophore-quencher antibody pairs as dual molecular probes for the enhanced specificity of image-guided surgery

The emergence of fluorescently labeled therapeutic antibodies has given rise to molecular probes for image-guided surgery. However, the extraneous interstitial presence of an unbound and nonspecifically accumulated probe gives rise to false-positive detection of tumor tissue and margins. Thus, the concept of tumor-cell activation of smart probes provides a potentially superior mechanism of delineating tumor margins as well as small tumor deposits. The combination of molecular targeting with intracellular activation circumvents the presence of extracellular, nonspecific signals of targeted probe accumulation. Here, we present a demonstration of the clinical antibodies cetuximab (cet, anti-EGFR mAb) and trastuzumab (trast, anti-HER-2 mAb) conjugated to Alexa Fluor molecules and IRDye QC-1 quencher optimized at the ratio of 1∶2∶6 to provide the greatest degree of proteolytic fluorescence activation, synonymous with intracellular lysosomal degradation. The cet-AF-Q-C1 conjugate (1∶2∶6) provides up to 9.8-fold proteolytic fluorescence activation. By preparing a spectrally distinct, irrelevant sham IgG-AF-QC-1 conjugate, a dual-activatable probe approach is shown to enhance the specificity of imaging within an orthotopic AsPC-1 pancreatic cancer xenograft model. The dual-activatable approach warrants expedited clinical translation to improve the specificity of image-guided surgery by spectrally decomposing specific from nonspecific probe accumulation, binding, and internalization.

Effects of temperature on multiparametric evaluation of hindlimb ischemia with dynamic fluorescence imaging

Quantitative evaluation of hindlimb ischemia is essential for early diagnosis and therapy of peripheral arterial disease (PAD). Dynamic imaging using near-infrared (NIR) fluorophore indocyanine green (ICG) is a noninvasive and effective tool to monitor multiple vascular parameters including perfusion rate (PR), perfusion vascular density (PVD) and hemodynamics. It has been previously demonstrated that temperature changes could lead to significant variations of blood flow rate and vascular perfusion. In this paper, multiparametric evaluation of hindlimb ischemia was performed at different temperatures. Five different parameters were extracted from dynamic fluorescence imaging, including PR, PVD, rising time (T_rise ), blood flow index (BFI) and mean fluorescence intensity (MFI). Temperatures varied from 15 °C to 40 °C were set on a mouse model of hindlimb ischemia. The aforementioned five parameters were obtained at each temperature. The results suggest that PVD, BFI and MFI could be effective indicators to distinguish ischemic tissues from normal tissues in mouse hindlimb at different temperatures. In contrast, PR is effective only when the temperature is higher than 25 °C, while T_rise is effective only when the temperature is lower than 35 °C. The parameters of PVD, BFI and MFI could provide quantitative and comprehensive evaluation for PAD at different temperatures. (A) Bright-field image of the normal (left) and ischemic (right) hindlimbs. (B-D) Parametric images of perfusion vascular density, blood flow index and mean fluorescence intensity.

Multiparametric evaluation of hindlimb ischemia using time-series indocyanine green fluorescence imaging

Peripheral arterial disease (PAD) can further cause lower limb ischemia. Quantitative evaluation of the vascular perfusion in the ischemic limb contributes to diagnosis of PAD and preclinical development of new drug. In vivo time-series indocyanine green (ICG) fluorescence imaging can noninvasively monitor blood flow and has a deep tissue penetration. The perfusion rate estimated from the time-series ICG images is not enough for the evaluation of hindlimb ischemia. The information relevant to the vascular density is also important, because angiogenesis is an essential mechanism for post-ischemic recovery. In this paper, a multiparametric evaluation method is proposed for simultaneous estimation of multiple vascular perfusion parameters, including not only the perfusion rate but also the vascular perfusion density and the time-varying ICG concentration in veins. The target method is based on a mathematical model of ICG pharmacokinetics in the mouse hindlimb. The regression analysis performed on the time-series ICG images obtained from a dynamic reflectance fluorescence imaging system. The results demonstrate that the estimated multiple parameters are effective to quantitatively evaluate the vascular perfusion and distinguish hypo-perfused tissues from well-perfused tissues in the mouse hindlimb. The proposed multiparametric evaluation method could be useful for PAD diagnosis. The estimated perfusion rate and vascular perfusion density maps (left) and the time-varying ICG concentration in veins of the ankle region (right) of the normal and ischemic hindlimbs.

Automatic selection of regularization parameters for dynamic fluorescence molecular tomography: a comparison of L-curve and U-curve methods

Dynamic fluorescence molecular tomography (FMT) is a promising technique for the study of the metabolic process of fluorescent agents in the biological body in vivo, and the quality of the parametric images relies heavily on the accuracy of the reconstructed FMT images. In typical dynamic FMT implementations, the imaged object is continuously monitored for more than 50 minutes. During each minute, a set of the fluorescent measurements is acquired and the corresponding FMT image is reconstructed. It is difficult to manually set the regularization parameter in the reconstruction of each FMT image. In this paper, the parametric images obtained with the L-curve and U-curve methods are quantitatively evaluated through numerical simulations, phantom experiments and in vivo experiments. The results illustrate that the U-curve method obtains better accuracy, stronger robustness and higher noise-resistance in parametric imaging. Therefore, it is a promising approach to automatic selection of the regularization parameters for dynamic FMT.

Direct reconstruction in CT-analogous pharmacokinetic diffuse fluorescence tomography: two-dimensional simulative and experimental validations

We present a generalized strategy for direct reconstruction in pharmacokinetic diffuse fluorescence tomography (DFT) with CT-analogous scanning mode, which can accomplish one-step reconstruction of the indocyanine-green pharmacokinetic-rate images within in vivo small animals by incorporating the compartmental kinetic model into an adaptive extended Kalman filtering scheme and using an instantaneous sampling dataset. This scheme, compared with the established indirect and direct methods, eliminates the interim error of the DFT inversion and relaxes the expensive requirement of the instrument for obtaining highly time-resolved date-sets of complete 360 deg projections. The scheme is validated by two-dimensional simulations for the two-compartment model and pilot phantom experiments for the one-compartment model, suggesting that the proposed method can estimate the compartmental concentrations and the pharmacokinetic-rates simultaneously with a fair quantitative and localization accuracy, and is well suitable for cost-effective and dense-sampling instrumentation based on the highly-sensitive photon counting technique.

Reconstruction of in vivo fluorophore concentration variation with structural priors and smooth penalty

Reconstruction of fluorophore concentration variation in fluorescence molecular tomography is expected to reveal the metabolic processes of fluorescent biomarkers in vivo. However, the complicated and strong noise within in vivo data inhibits its applications for in vivo cases. A smooth penalty method is presented in this work to suppress the noise. The method is based on a recursive reconstruction scheme which reconstructs the fluorophore concentration variation rates (FCVRs) of two neighboring frames at the same time within an inner iteration. In addition, the performance of the Laplacian-type regularization incorporating structural priors is investigated. Results of simulations suggest that the smooth penalty method almost has no influence on the reconstructed FCVRs when the target curve is smooth, and results of in vivo experiments on mice indicate that the method is capable of suppressing the noise and achieving smooth time courses of fluorescent yield. Results of both the simulations and in vivo experiments demonstrate that the Laplacian-type regularization can improve the image quality.

Lock-in-photon-counting-based highly-sensitive and large-dynamic imaging system for continuous-wave diffuse optical tomography

We implemented a novel lock-in photon-counting detection architecture that combines the ultra-high sensitivity of the photon-counting detection and the measurement parallelism of the lock-in technique. Based on this technique, a dual-wavelength simultaneous measurement continuous wave diffuse optical tomography system was developed with a configuration of 16 sources and 16 detectors that works in a tandem serial-to-parallel fashion. Methodology validation and performance assessment of the system were conducted using phantom experiments that demonstrate excellent measurement linearity, moderate-term system stability, robustness to noise and negligible inter-wavelength crosstalk. 2-D imaging experiments further validate high sensitivity of the lock-in photon-counting methodology as well as high reliability of the proposed system. The advanced detection principle can be adapted to achieving a fully parallelized instrumentation for the extended applications.

3D mouse shape reconstruction based on phase-shifting algorithm for fluorescence molecular tomography imaging system

This work introduces a fast, low-cost, robust method based on fringe pattern and phase shifting to obtain three-dimensional (3D) mouse surface geometry for fluorescence molecular tomography (FMT) imaging. We used two pico projector/webcam pairs to project and capture fringe patterns from different views. We first calibrated the pico projectors and the webcams to obtain their system parameters. Each pico projector/webcam pair had its own coordinate system. We used a cylindrical calibration bar to calculate the transformation matrix between these two coordinate systems. After that, the pico projectors projected nine fringe patterns with a phase-shifting step of 2π/9 onto the surface of a mouse-shaped phantom. The deformed fringe patterns were captured by the corresponding webcam respectively, and then were used to construct two phase maps, which were further converted to two 3D surfaces composed of scattered points. The two 3D point clouds were further merged into one with the transformation matrix. The surface extraction process took less than 30 seconds. Finally, we applied the Digiwarp method to warp a standard Digimouse into the measured surface. The proposed method can reconstruct the surface of a mouse-sized object with an accuracy of 0.5 mm, which we believe is sufficient to obtain a finite element mesh for FMT imaging. We performed an FMT experiment using a mouse-shaped phantom with one embedded fluorescence capillary target. With the warped finite element mesh, we successfully reconstructed the target, which validated our surface extraction approach.

Fast reconstruction of fluorophore concentration variation based on the derivation of the diffusion equation

The information of fluorophore concentration variation (FCV) has the potential for drug development and tumor studies, but the reconstruction of FCV is time-consuming in dynamic fluorescence molecular tomography (DFMT). In this paper, a time-efficient reconstruction method for FCV is presented. The system equation of this method is derived from the derivation of the diffusion equation, and its size does not change with the number of frames. The computational time can be significantly reduced by using this method because the images of different frames are reconstructed separately. Simulations and phantom experiments are performed to validate the performance of the proposed method. The results show that compared with the previous method, the proposed method can obtain better results and consumes less computational time with the same number of iterations. In addition, the time consumption in a single iteration of the proposed method increases much slower with the number of frames.

The Value of Intraoperative Near-Infrared Fluorescence Imaging Based on Enhanced Permeability and Retention of Indocyanine Green: Feasibility and False-Positives in Ovarian Cancer

Objective

In ovarian cancer, two of the most important prognostic factors for survival are completeness of staging and completeness of cytoreductive surgery. Therefore, intra-operative visualization of tumor lesions is of great importance. Preclinical data already demonstrated tumor visualization in a mouse-model using near-infrared (NIR) fluorescence imaging and indocyanine green (ICG) as a result of enhanced permeability and retention (EPR). The aim of this study was to determine feasibility of intraoperative ovarian cancer metastases imaging using NIR fluorescence imaging and ICG in a clinical setting.

Methods

Ten patients suspected of ovarian cancer scheduled for staging or cytoreductive surgery were included. Patients received 20 mg ICG intravenously after opening the abdominal cavity. The mini-FLARE NIR fluorescence imaging system was used to detect NIR fluorescent lesions.

Results

6 out of 10 patients had malignant disease of the ovary or fallopian tube, of which 2 had metastatic disease outside the pelvis. Eight metastatic lesions were detected in these 2 patients, which were all NIR fluorescent. However, 13 non-malignant lesions were also NIR fluorescent, resulting in a false-positive rate of 62%. There was no significant difference in tumor-to-background ratio between malignant and benign lesions (2.0 vs 2.0; P=0.99).

Conclusions

This is the first clinical trial demonstrating intraoperative detection of ovarian cancer metastases using NIR fluorescence imaging and ICG. Despite detection of all malignant lesions, a high false-positive rate was observed. Therefore, NIR fluorescence imaging using ICG based on the EPR effect is not satisfactory for the detection of ovarian cancer metastases. The need for tumor-specific intraoperative agents remains.

Trial Registration

ISRCTN Registry ISRCTN16945066

Performance Enhancement of Pharmacokinetic Diffuse Fluorescence Tomography by Use of Adaptive Extended Kalman Filtering

Due to both the physiological and morphological differences in the vascularization between healthy and diseased tissues, pharmacokinetic diffuse fluorescence tomography (DFT) can provide contrast-enhanced and comprehensive information for tumor diagnosis and staging. In this regime, the extended Kalman filtering (EKF) based method shows numerous advantages including accurate modeling, online estimation of multiparameters, and universal applicability to any optical fluorophore. Nevertheless the performance of the conventional EKF highly hinges on the exact and inaccessible prior knowledge about the initial values. To address the above issues, an adaptive-EKF scheme is proposed based on a two-compartmental model for the enhancement, which utilizes a variable forgetting-factor to compensate the inaccuracy of the initial states and emphasize the effect of the current data. It is demonstrated using two-dimensional simulative investigations on a circular domain that the proposed adaptive-EKF can obtain preferable estimation of the pharmacokinetic-rates to the conventional-EKF and the enhanced-EKF in terms of quantitativeness, noise robustness, and initialization independence. Further three-dimensional numerical experiments on a digital mouse model validate the efficacy of the method as applied in realistic biological systems.

Bayesian Framework Based Direct Reconstruction of Fluorescence Parametric Images

Fluorescence imaging has been successfully used in the study of pharmacokinetic analysis, while dynamic fluorescence molecular tomography (FMT) is an attractive imaging technique for three-dimensionally resolving the metabolic process of fluorescent biomarkers in small animals in vivo. Parametric images obtained by combining dynamic FMT with compartmental modeling can provide quantitative physiological information for biological studies and drug development. However, images obtained with conventional indirect methods suffer from poor image quality because of failure in utilizing the temporal correlations of boundary measurements. Besides, FMT suffers from low spatial resolution due to its ill-posed nature, which further reduces the image quality. In this paper, we propose a novel method to directly reconstruct parametric images from boundary measurements based on maximum a posteriori (MAP) estimation with structural priors in a Bayesian framework. The proposed method can utilize structural priors obtained from an X-ray computed tomography system to mitigate the ill-posedness of dynamic FMT inverse problem, and use direct reconstruction strategy to make full use of temporal correlations of boundary measurements. The results of numerical simulations and in vivo mouse experiments demonstrate that the proposed method leads to significant improvements in the reconstruction quality of parametric images as compared with the conventional indirect method and a previously developed direct method.

In vivo mouse fluorescence imaging for folate-targeted delivery and release kinetics

Many cancer cells over-express folate receptors, and this provides an opportunity for both folate-targeted fluorescence imaging and the development of targeted anti-cancer drugs. We present an optical imaging modality that allows for the monitoring and evaluation of drug delivery and release through disulfide bond reduction inside a tumor in vivo for the first time. A near-infrared folate-targeting fluorophore pair was synthesized and used to image a xenograft tumor grown from KB cells in a live mouse. The in vivo results are shown to be in agreement with previous in vitro studies, confirming the validity and feasibility of our method as an effective tool for preclinical studies in drug development.

Reconstruction of fluorophore concentration variation in dynamic fluorescence molecular tomography

Dynamic fluorescence molecular tomography (DFMT) is a potential approach for drug delivery, tumor detection, diagnosis, and staging. The purpose of DFMT is to quantify the changes of fluorescent agents in the bodies, which offer important information about the underlying physiological processes. However, the conventional method requires that the fluorophore concentrations to be reconstructed are stationary during the data collection period. As thus, it cannot offer the dynamic information of fluorophore concentration variation within the data collection period. In this paper, a method is proposed to reconstruct the fluorophore concentration variation instead of the fluorophore concentration through a linear approximation. The fluorophore concentration variation rate is introduced by the linear approximation as a new unknown term to be reconstructed and is used to obtain the time courses of fluorophore concentration. Simulation and phantom studies are performed to validate the proposed method. The results show that the method is able to reconstruct the fluorophore concentration variation rates and the time courses of fluorophore concentration with relative errors less than 0.0218.

Towards whole-body fluorescence imaging in humans

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

Indocyanine green enhanced co-registered diffuse optical tomography and photoacoustic tomography

To overcome the intensive light scattering in biological tissue, diffuse optical tomography (DOT) in the near-infrared range for breast lesion detection is usually combined with other imaging modalities, such as ultrasound, x-ray, and magnetic resonance imaging, to provide guidance. However, these guiding imaging modalities may depend on different contrast mechanisms compared to the optical contrast in the DOT. As a result, they cannot provide reliable guidance for DOT because some lesions may not be detectable by a nonoptical modality but may have a high optical contrast. An imaging modality that relies on optical contrast to provide guidance is desirable for DOT. We present a system that combines a frequency-domain DOT and real-time photoacoustic tomography (PAT) systems to detect and characterize deeply seated targets embedded in a turbid medium. To further improve the contrast, the exogenous contrast agent, indocyanine green (ICG), is used. Our experimental results show that the combined system can detect a tumor-mimicking phantom, which is immersed in intralipid solution with the concentrations ranging from 100 to 10 μM and with the dimensions of 0.8 cm × 0.8 cm × 0.6 cm, up to 2.5 cm in depth. Mice experiments also confirmed that the combined system can detect tumors and monitor the ICG uptake and washout in the tumor region. This method can potentially improve the accuracy to detect small breast lesions as well as lesions that are sensitive to background tissue changes, such as the lesions located just above the chest wall.

Towards non-invasive characterization of breast cancer and cancer metabolism with diffuse optics

We review recent developments in diffuse optical imaging and monitoring of breast cancer, i.e. optical mammography. Optical mammography permits non-invasive, safe and frequent measurement of tissue hemodynamics oxygen metabolism and components (lipids, water, etc.), the development of new compound indices indicative of the risk and malignancy, and holds potential for frequent non-invasive longitudinal monitoring of therapy progression.

Kinetic model optimization for characterizing tumour physiology by dynamic contrast-enhanced near-infrared spectroscopy

Dynamic contrast-enhanced (DCE) methods are widely used with magnetic resonance imaging and computed tomography to assess the vascular characteristics of tumours since these properties can affect the response to radiotherapy and chemotherapy. In contrast, there have been far fewer studies using optical-based applications despite the advantages of low cost and safety. This study investigated an appropriate kinetic model for optical applications to characterize tumour haemodynamics (blood flow, F, blood volume, V(b), and vascular heterogeneity) and vascular leakage (permeability surface-area product, PS). DCE data were acquired with two dyes, indocyanine green (ICG) and 800 CW carboxylate (IRD(cbx)), from a human colon tumour xenograph model in rats. Due to the smaller molecular weight of IRD(cbx) (1166 Da) compared to albumin-bound ICG (67 kDa), PS of IRD(cbx) was significantly larger; however, no significant differences in F and V(b) were found between the dyes as expected. Error analysis demonstrated that all parameters could be estimated with an uncertainty less than 5% due to the high temporal resolution and signal-to-noise ratio of the optical measurements. The next step is to adapt this approach to optical imaging to generate haemodynamics and permeability maps, which should enhance the clinical interest in optics for treatment monitoring.

Three-dimensional fluorescence tomography of human breast tissues in vivo using a hand-held optical imager

Diffuse optical imaging using non-ionizing radiation is a non-invasive method that shows promise towards breast cancer diagnosis. Hand-held optical imagers show potential for clinical translation of the technology, yet they have not been used towards 3D tomography. Herein, 3D tomography of human breast tissue in vivo is demonstrated for the first time using a hand-held optical imager with automated coregistration facilities. Simulation studies are performed on breast geometries to demonstrate the feasibility of 3D tomographic imaging using a hand-held imager under perfect (1:0) and imperfect (100:1, 50:1) fluorescence absorption contrast ratios. Experimental studies are performed in vivo using a 1 µM ICG filled phantom target placed non-invasively underneath the flap of the breast tissue. Results show the ability to perform automated tracking and coregistered imaging of human breast tissue (with tracking accuracy on the order of ∼1 cm). Three-dimensional tomography results demonstrated the ability to recover a single target placed at a depth of 2.5 cm, from both the simulated (at 1:0, 100:1 and 50:1 contrasts) and experimental cases on actual breast tissues. Ongoing efforts to improve target depth recovery are carried out via implementation of transmittance imaging in the hand-held imager.

Molecular cytogenetic evaluation of the efficacy of photodynamic therapy by indocyanine green in breast adenocarcinoma MCF-7 cells

BACKGROUND

Photodynamic therapy (PDT) is used for the treatment of many types of predominantly epithelial cancers. Photosensitizer is taken up by fast growing tumor cells more actively than by other body cells and is activated by light, generating reactive oxygen species that cause cell death by necrosis or apoptosis. This study aimed to evaluate the efficacy of PDT with indocyanine green (ICG) through the investigation of TP53, HER-2 and TOP2A genes signals as breast cancer gene markers by interphase fluorescence in situ hybridization (nuc-FISH).

METHODS

The photosynthetizer ICG (200 μM) was applied to breast cancer cell line MCF-7 cells (adenocarcinoma) in combination with laser irradiation (807 nm) exposure for 20 min and then incubated for 12, 24 and 48 h. Cell viability was evaluated using trypan blue. The signals for nuc-FISH was investigated and counted for probes specific for the genes TP53 (17p13), HER-2 (17q11.2-q12), and TOP2A (17q21-q22), and BAC-probes RP11-746M1 in 17p11.2 and RP11-403E9 in 17q11.2.

RESULTS

The cell viability of MCF-7 did not reduced significantly when the cells were treated with ICG (200 μM) or exposed to laser irradiation for 20 min followed by incubation for 24 h. ICG/PDT treatment with laser irradiation exposure for 20 min reduced the cell viability after incubating cells for 12, 24 and 48 h highly significantly in a time dependent manner. For nuc-FISH analysis, TP53, HER-2, TOP2A, RP11-746M1 and RP11-403E9 signals did not reduce or increase in a significant manner when the cells were treated with ICG or exposed to laser irradiation for 20 min then incubated for 24h. PDT enhanced amplification of TP53 signals from nuc ish 17p13(TP53×2) to nuc ish 17p13(TP53×3) or nuc ish 17p13(TP53×4). However, the signals of HER-2 gene, TOP2A gene and BAC probes were reduced highly significantly when MCF-7 cells were treated with PDT with all time intervals.

CONCLUSION

ICG/PDT and laser induced cytotoxic effect in MCF-7 cells. Also, PDT enhanced TP53 gene amplification, and reduced HER-2, TOP2A, and BAC probes RP11-746M1 and RP11-403E9 signals. Therefore ICG/PDT can be used for breast cancer treatment. It has the potential to induce apoptotic effect and reduce HER-2 and TOP2A genes propagation. Further in vivo studies are needed to evaluate ICG/PDT as a promising therapeutic approach for breast cancer.

Near-infrared imaging of breast cancer using optical contrast agents

Breast cancer is the most common malignancy in women worldwide and the second leading cause of cancer death. On the basis of three studies performed by our group, this article reviews the current status of optical breast imaging using extrinsic contrast agents. To date, only two contrast agents have been applied in human studies, indocyanine green (ICG) and omocianine. Both contrast media were used for absorption and fluorescence imaging. Generally speaking, malignant breast lesions exhibited higher absorption contrast as well as higher fluorescence contrast compared to benign lesions or non-diseased breast tissue. Some groups consider early enhancement characteristics helpful for differentiation between malignant and benign lesions. Late fluorescence ICG imaging - capitalizing on the extravasation of the dye through the wall of tumorous vessels - seems to be a promising technique to distinguish malignant from benign breast lesions.

Fluorescent nanoprobes dedicated to in vivo imaging: from preclinical validations to clinical translation

With the fast development, in the last ten years, of a large choice of set-ups dedicated to routine in vivo measurements in rodents, fluorescence imaging techniques are becoming essential tools in preclinical studies. Human clinical uses for diagnostic and image-guided surgery are also emerging. In comparison to low-molecular weight organic dyes, the use of fluorescent nanoprobes can improve both the signal sensitivity (better in vivo optical properties) and the fluorescence biodistribution (passive “nano” uptake in tumours for instance). A wide range of fluorescent nanoprobes have been designed and tested in preclinical studies for the last few years. They will be reviewed and discussed considering the obstacles that need to be overcome for their potential everyday use in clinics. The conjugation of fluorescence imaging with the benefits of nanotechnology should open the way to new medical applications in the near future.

Implicit and explicit prior information in near-infrared spectral imaging: accuracy, quantification and diagnostic value

Near-infrared spectroscopy (NIRS) of tissue provides quantification of absorbers, scattering and luminescent agents in bulk tissue through the use of measurement data and assumptions. Prior knowledge can be critical about things such as (i) the tissue shape and/or structure, (ii) spectral constituents, (iii) limits on parameters, (iv) demographic or biomarker data, and (v) biophysical models of the temporal signal shapes. A general framework of NIRS imaging with prior information is presented, showing that prior information datasets could be incorporated at any step in the NIRS process, with the general workflow being: (i) data acquisition, (ii) pre-processing, (iii) forward model, (iv) inversion/reconstruction, (v) post-processing, and (vi) interpretation/diagnosis. Most of the development in NIRS has used ad hoc or empirical implementations of prior information such as pre-measured absorber or fluorophore spectra, or tissue shapes as estimated by additional imaging tools. A comprehensive analysis would examine what prior information maximizes the accuracy in recovery and value for medical diagnosis, when implemented at separate stages of the NIRS sequence. Individual applications of prior information can show increases in accuracy or improved ability to estimate biochemical features of tissue, while other approaches may not. Most beneficial inclusion of prior information has been in the inversion/reconstruction process, because it solves the mathematical intractability. However, it is not clear that this is always the most beneficial stage.

Near infrared active heptacyanine dyes with unique cancer-imaging and cytotoxic properties

Three near-infrared fluorescent heptacarbocyanine dyes have been synthesized using a facile one-pot synthetic approach. The reaction methodology afforded a mixture of three symmetric and unsymmetric heptacyanines containing various N-indolenine substituents, a dicarbocyclic acid (DA), a monoester (ME), and a diester (DE). These compounds were isolated, purified, characterized and biologically investigated for tumor cell cytotoxicity and uptake selectivity. Using cell viability and in vitro proliferation assays, we found that the esterified dyes (monoester, ME and diester, DE) were selectively cytotoxic to cancer cells and spared normal fibroblast cells. Additionally, confocal fluorescence imaging confirmed selective uptake of these dyes in cancer cells, thus suggesting tumor cell targeting.

Unmixing dynamic fluorescence diffuse optical tomography images with independent component analysis

Dynamic fluorescence diffuse optical tomography (D-FDOT) is important for drug delivery research. However, the low spatial resolution of FDOT and the complex kinetics of drug limit the ability of D-FDOT in resolving metabolic processes of drug throughout whole body of small animals. In this paper, we propose an independent component analysis (ICA)-based method to perform D-FDOT studies. When applied to D-FDOT images, ICA not only generates a set of independent components (ICs) which can illustrate functional structures with different kinetic behaviors, but also provides a set of associated time courses (TCs) which can represent normalized time courses of drug in corresponding functional structures. Further, the drug concentration in specific functional structure at different time points can be recovered by an inverse ICA transformation. To evaluate the performance of the proposed algorithm in the study of drug kinetics at whole-body level, simulation study and phantom experiment are both performed on a full-angle FDOT imaging system with line-shaped excitation pattern. In simulation study, the nanoparticle delivery of indocynaine green (ICG) throughout whole body of a digital mouse is simulated and imaged. In phantom experiment, four tubes containing different ICG concentrations are imaged and used to imitate the uptake and excretion of ICG in organs. The results suggest that we can not only illustrate ICG distributions in different functional structures, but also recover ICG concentrations in specific functional structure at different time points, when ICA is applied to D-FDOT images.

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.

Dynamic fluorescence imaging for multiparametric measurement of tumor vasculature

Angiogenesis is essential for tumor growth and a promising target for cancer therapy. Blood vessel monitoring is an indispensable tool for evaluation and development of anti-angiogenic drugs. Here, we report a new noninvasive in vivo imaging tool, named dynamic fluorescence imaging (DyFI), for the simultaneous measurement of multiple vascular parameters including vascular density, perfusion rate, and permeability using spatiotemporal profiles of indocyanine green. Using DyFI in a tumor xenograft model, we quantitatively measured multiple vascular parameters in tumors and normal tissues with high spatial resolution. The multimodality of this method allowed us to find negative spatial correlations between perfusion and permeability. Moreover, DyFI was effective for revealing the early effects of an anti-angiogenic drug. We suggest that DyFI could be a useful tool for the preclinical development of anti-angiogenic drugs.

Artifact reduction method in ultrasound-guided diffuse optical tomography using exogenous contrast agents

In diffuse optical tomography (DOT), a typical perturbation approach requires two sets of measurements obtained at the lesion breast (lesion or target site) and a contra-lateral location of the normal breast (reference site) for image reconstruction. For patients who have a small amount of breast tissue, the chest-wall underneath the breast tissue at both sites affects the imaging results. In this group of patients, the perturbation, which is the difference between measurements obtained at the lesion and reference sites, may include the information of background mismatch which can generate artifacts or affect the reconstructed quantitative absorption coefficient of the lesion. Also, for patients who have a single breast due to prior surgery, the contra-lateral reference is not available. To improve the DOT performance or overcome its limitation, we introduced a new method based on an exogenous contrast agent and demonstrate its performance using animal models. Co-registered ultrasound was used to guide the lesion localization. The results have shown that artifacts caused by background mismatch can be reduced significantly by using this new method.

Formation of near-infrared fluorescent nanoparticles for medical imaging

Aims: Indocyanine green (ICG) is a US FDA-approved near-infrared fluorescent, water-soluble dye used for diagnostics in vitro and in vivo. The aim of this study was to develop insoluble nanoparticles based on a cationic polymer, ICG and a targeting molecule. The particles are intended for oral administration in the colon, having fluorescence in near-infrared, thus enabling remote detection. Materials & methods: An aqueous dispersion of particles formed from Eudragit-RS by simple precipitation method possessing a mean size of approximately 100 nm and zeta potential of +16 mV was produced. Results: These particles are capable of binding both ICG and fluorescein isothiocyanate–IgG via noncovalent interactions. These composite particles retain the emission characteristics of the fluorescent precursors and also exhibit potential specific recognition ability. The particles were stable in intestinal fluid and are composed only of materials that are FDA approved. Conclusion: The nanoparticles may be suitable for in vivo imaging and therapy by oral delivery systems.

Optical imaging in cancer research: basic principles, tumor detection, and therapeutic monitoring

Accurate and rapid detection of diseases is of great importance for assessing the molecular basis of pathogenesis, preventing the onset of complications, and implementing a tailored therapeutic regimen. The ability of optical imaging to transcend wide spatial imaging scales ranging from cells to organ systems has rejuvenated interest in using this technology for medical imaging. Moreover, optical imaging has at its disposal diverse contrast mechanisms for distinguishing normal from pathologic processes and tissues. To accommodate these signaling strategies, an array of imaging techniques has been developed. Importantly, light absorption, and emission methods, as well as hybrid optical imaging approaches are amenable to both small animal and human studies. Typically, complex methods are needed to extract quantitative data from deep tissues. This review focuses on the development of optical imaging platforms, image processing techniques, and molecular probes, as well as their applications in cancer diagnosis, staging, and monitoring therapeutic response.

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.

Dual-contrast dynamic MRI-DOT for small animal imaging

In this paper we present first-of-its-kind spatially resolved enhancement kinetics of optical and magnetic resonance (MR) agents obtained by a combined MR and Diffuse Optical Tomography (MR-DOT) animal imaging system. A unique MR compatible fiber optic interface allows co-registration of MR and DOT data in space and time. High temporal resolution of the hybrid system permits acquisition of data in dynamic mode. Rats bearing a R3230 AC breast cancer tumor model are used for in vivo studies. Thirty-two optical and thirty MR images are acquired during a single imaging session that lasts nearly ten minutes. Both optical, indocyanine green (ICG), and MR contrast agents, gadolinium-DTPA (Gd-DTPA), are injected simultaneously after the acquisition of several baseline frames. Contrast enhancement time curves obtained by MR and DOT systems both indicate higher average enhancement in tumor regions, up to ten-fold for MRI and 3-fold for DOT, compared to close by non-tumor regions. This feasibility study is the first step towards clinical translation of this hybrid imaging platform. The ultimate aim is to use the enhancement kinetics of the optical agent ICG, which binds to plasma proteins, as complementary information to the kinetics of the MR agent Gd-DTPA, a small molecular agent that does not bind to plasma proteins, to better differentiate benign and malignant lesions.

Late-fluorescence mammography assesses tumor capillary permeability and differentiates malignant from benign lesions

Using scanning time-domain instrumentation we recorded fluorescence projection mammograms on few breast cancer patients prior, during and after infusion of indocyanine green (ICG), while monitoring arterial ICG concentration by transcutaneous pulse densitometry. Late-fluorescence mammograms recorded after ICG had been largely cleared from the blood by the liver, showed invasive carcinomas at high contrast over a rather homogeneous background, whereas benign lesions did not produce (focused) fluorescence contrast. During infusion, tissue concentration contrast and hence fluorescence contrast is determined by intravascular contributions, whereas late-fluorescence mammograms are dominated by contributions from protein-bound ICG extravasated into the interstitium, reflecting relative microvascular permeabilities of carcinomas and normal breast tissue. We simulated intravascular and extravascular contributions to ICG tissue concentration contrast within a two-compartment unidirectional pharmacokinetic model.