Imaging Of Tumor Angiogenesis Research Articles

Exploring the Role of [68Ga]Ga-DOTAGA-IAC and Comparison of Its Diagnostic Performance with [18F]F-FDG PET/CT in Radioiodine Refractory Differentiated Thyroid Carcinoma.

Introduction: Integrin antagonist complex (IAC), a novel αvβ3 integrin antagonist peptidomimetic, has emerged as a promising agent for molecular imaging of tumor angiogenesis. This study evaluates the biodistribution and clinical efficacy of [68Ga]Ga-DOTAGA-IAC PET/CT in detecting radioiodine-refractory differentiated thyroid carcinoma (RAIR-DTC), comparing its diagnostic performance with [18F]F-FDG PET/CT. Materials and Methods: In this prospective pilot study, RAIR-DTC patients underwent whole-body imaging with [18F] F-FDG PET/CT, followed by [68Ga]Ga-DOTAGA-IAC PET/CT. Biodistribution patterns of [68Ga]Ga-DOTAGA-IAC were assessed. Lesions with abnormal, nonphysiologic tracer uptake (showing activity exceeding mediastinal blood pool) were considered positive for disease. Imaging findings were compared between the two modalities, and quantitative metrics, including SUVmax, metabolic tumor volume, and total lesion glycolysis, were analyzed statistically. Results: Among 30 patients with RAIR-DTC, [68Ga]Ga-DOTAGA-IAC PET/CT revealed predominant physiological tracer uptake in the kidneys. [18F]F-FDG PET/CT identified 97 lesions, predominantly nodal (73.2%), while [68Ga]Ga-DOTAGA-IAC PET/CT detected 34 lesions, 50% of which were nodal. Few patients exhibited multiple lesions with varying uptake grades, with 20% showing coexisting higher-grade lesions (grade II or above) on [68Ga]Ga-DOTAGA-IAC PET/CT. Conclusion: Angiogenesis imaging using [68Ga]Ga-DOTAGA-IAC PET/CT demonstrates limited sensitivity for lesion detection in patients with RAIR-DTC compared with [18F]F-FDG PET/CT. However, the potential of [68Ga]Ga-DOTAGA-IAC as a diagnostic tool for other cancers has been used in other cancers with positive imaging characteristics warranting further exploration.

Volumetric imaging and morphometric analysis of breast tumor angiogenesis using a new contrast-free ultrasound technique: a feasibility study

BackgroundThere is a strong correlation between the morphological features of new tumor vessels and malignancy. However, angiogenic heterogeneity necessitates 3D microvascular data of tumor microvessels for more reliable quantification. To provide more accurate information regarding vessel morphological features and improve breast lesion characterization, we introduced a quantitative 3D high-definition microvasculature imaging (q3D-HDMI) as a new easily applicable and robust tool to morphologically characterize microvasculature networks in breast tumors using a contrast-free ultrasound-based imaging approach.MethodsIn this prospective study, from January 2020 through December 2021, a newly developed q3D-HDMI technique was evaluated on participants with ultrasound-identified suspicious breast lesions recommended for core needle biopsy. The morphological features of breast tumor microvessels were extracted from the q3D-HDMI. Leave-one-out cross-validation (LOOCV) was applied to test the combined diagnostic performance of multiple morphological parameters of breast tumor microvessels. Receiver operating characteristic (ROC) curves were used to evaluate the prediction performance of the generated pooled model.ResultsNinety-three participants (mean age 52 ± 17 years, 91 women) with 93 breast lesions were studied. The area under the ROC curve (AUC) generated with q3D-HDMI was 95.8% (95% CI 0.901–1.000), yielding a sensitivity of 91.7% and a specificity of 98.2%, that was significantly higher than the AUC generated with the q2D-HDMI (p = 0.02). When compared to q2D-HDMI, the tumor microvessel morphological parameters obtained from q3D-HDMI provides distinctive information that increases accuracy in differentiating breast tumors.ConclusionsThe proposed quantitative volumetric imaging technique augments conventional breast ultrasound evaluation by increasing specificity in differentiating malignant from benign breast masses.

Molecular Imaging of Tumor Progression and Angiogenesis by Dual Bioluminescence.

Angiogenesis is a prerequisite for tumor growth and invasion, and anti-angiogenesis has become a highlight in tumor treatment research. However, so far, there is no reliable solution for how to simultaneously visualize the relationship between tumor progression and angiogenesis. Bioluminescence imaging (BLI) has been broadly utilized and is a very promising non-invasive imaging technique with the advantages of low cost, high sensitivity, and robust specificity. In this chapter, we describe a dual bioluminescence imaging BLI protocol for tumor progression and angiogenesis through implanting murine breast cancer cell line 4T1 which stably expressing Renilla luciferase (RLuc) into the transgenic mice with angiogenesis-induced firefly luciferase (FLuc) expression. This modality enables us to synchronously monitor the tumor progression and angiogenesis in the same mouse, which has broad applicability in oncology studies.

Nanoparticles modified with vasculature-homing peptides for targeted cancer therapy and angiogenesis imaging

The two major challenges in cancer treatment include lack of early detection and ineffective therapies with various side effects. Angiogenesis is the key process in the growth, survival, invasiveness, and metastasis of many of cancerous tumors. Imaging of the angiogenesis could lead to diagnosis of tumors in the early stage and evaluation of the therapeutic responses. Angiogenic blood vessels express specific molecular markers different from normal blood vessels (in level or kind). This fact would make the tumor vasculature a suitable site to target therapeutics and imaging agents within the tumor. Surface modified nanoparticles using peptide ligands with high binding affinity to the vasculature markers, provide efficient delivery of therapeutic and imaging agents, while avoiding undesirable side effects. In this review, we discuss discoveries of various tumor targeting peptides useful for tumor angiogenesis imaging and targeted therapy with emphasis on surface modified nanomedicines using vasculature targeting peptides.

Synthesis of Novel, Dual-Targeting 68Ga-NODAGA-LacN-E[c(RGDfK)]2 Glycopeptide as a PET Imaging Agent for Cancer Diagnosis.

Radiolabeled peptides possessing an Arg-Gly-Asp (RGD) motif are widely used radiopharmaceuticals for PET imaging of tumor angiogenesis due to their high affinity and selectivity to αvβ3 integrin. This receptor is overexpressed in tumor and tumor endothelial cells in the case of numerous cancer cell lines, therefore, it is an excellent biomarker for cancer diagnosis. The galectin-3 protein is also highly expressed in tumor cells and N-acetyllactosamine is a well-established ligand of this receptor. We have developed a synthetic method to prepare a lactosamine-containing radiotracer, namely 68Ga-NODAGA-LacN-E[c(RGDfK)]2, for cancer diagnosis. First, a lactosamine derivative with azido-propyl aglycone was synthetized. Then, NODAGA-NHS was attached to the amino group of this lactosamine derivative. The obtained compound was conjugated to an E[c(RGDfK)]2 peptide with a strain-promoted click reaction. We have accomplished the radiolabeling of the synthetized NODAGA-LacN-E[c(RGDfK)]2 precursor with a positron-emitting 68Ga isotope (radiochemical yield of >95%). The purification of the labeled compound with solid-phase extraction resulted in a radiochemical purity of >99%. Subsequently, the octanol–water partition coefficient (log P) of the labeled complex was determined to be −2.58. In addition, the in vitro stability of 68Ga-NODAGA-LacN-E[c(RGDfK)]2 was investigated and it was found that it was stable under the examined conditions.

Current Concepts in Multi-Modality Imaging of Solid Tumor Angiogenesis.

Simple SummaryThe recent increase in the use of targeted molecular therapy including anti-angiogenetic agents in cancer treatment necessitate the use of robust tools to assess and guide treatment. Angiogenesis, the formation of new disorganized blood vessels, is used by tumor cells to grow and spread using different mechanisms that could be targeted by anti-angiogenetic agents. In this review, we discuss the biological principles of tumor angiogenesis and the imaging modalities that could provide information beyond gross tumor size and morphology to capture the efficacy of anti-angiogenetic therapeutic response.There have been rapid advancements in cancer treatment in recent years, including targeted molecular therapy and the emergence of anti-angiogenic agents, which necessitate the need to quickly and accurately assess treatment response. The ideal tool is robust and non-invasive so that the treatment can be rapidly adjusted or discontinued based on efficacy. Since targeted therapies primarily affect tumor angiogenesis, morphological assessment based on tumor size alone may be insufficient, and other imaging modalities and features may be more helpful in assessing response. This review aims to discuss the biological principles of tumor angiogenesis and the multi-modality imaging evaluation of anti-angiogenic therapeutic responses.

PET Imaging of VEGFR with a Novel 64Cu-Labeled Peptide.

Vascular endothelial growth factor receptors (VEGFRs) are well recognized as significant biomarkers of tumor angiogenesis. Herein, we have developed a first-of-its-kind peptide-based VEGFR positron emission tomography (PET) tracer. The novel [64Cu]VEGF125–136 peptide possessed satisfactory radio-characteristics and showed good specificity for the visualization of VEGFR in various mouse models, in which the tumor-specific radioactivity uptake was highly correlated to the VEGFR expression level. Moreover, the tracer showed high tumor uptake (ca. 5.89 %ID/g at 20 min postinjection in B16F10 mice) and excellent pharmacokinetics, achieving the maximum imaging quality within 1 h after injection. These features convey [64Cu]VEGF125–136 as a promising, clinically translatable PET tracer for the imaging of tumor angiogenesis.

A generative adversarial network for artifact removal in photoacoustic computed tomography with a linear-array transducer.

With balanced spatial resolution, penetration depth, and imaging speed, photoacoustic computed tomography (PACT) is promising for clinical translation such as in breast cancer screening, functional brain imaging, and surgical guidance. Typically using a linear ultrasound (US) transducer array, PACT has great flexibility for hand-held applications. However, the linear US transducer array has a limited detection angle range and frequency bandwidth, resulting in limited-view and limited-bandwidth artifacts in the reconstructed PACT images. These artifacts significantly reduce the imaging quality. To address these issues, existing solutions often have to pay the price of system complexity, cost, and/or imaging speed. Here, we propose a deep-learning-based method that explores the Wasserstein generative adversarial network with gradient penalty (WGAN-GP) to reduce the limited-view and limited-bandwidth artifacts in PACT. Compared with existing reconstruction and convolutional neural network approach, our model has shown improvement in imaging quality and resolution. Our results on simulation, phantom, and in vivo data have collectively demonstrated the feasibility of applying WGAN-GP to improve PACT’s image quality without any modification to the current imaging set-up. Impact statement This study has the following main impacts. It offers a promising solution for removing limited-view and limited-bandwidth artifact in PACT using a linear-array transducer and conventional image reconstruction, which have long hindered its clinical translation. Our solution shows unprecedented artifact removal ability for in vivo image, which may enable important applications such as imaging tumor angiogenesis and hypoxia. The study reports, for the first time, the use of an advanced deep-learning model based on stabilized generative adversarial network. Our results have demonstrated its superiority over other state-of-the-art deep-learning methods.

In vivo detection of tumor boundary using ultrahigh-resolution optical coherence angiography and fluorescence imaging.

Accurate detection of early tumor margin is of great preclinical and clinical implications for predicting the survival rate of subjects and assessing the response of tumor microenvironment to chemotherapy or radiation therapy. Here, we report a multimodality optical imaging study on in vivo detection of tumor boundary by analyzing neoangiogenesis of tumor microenvironment (microangiography), microcirculatory blood flow (optical Doppler tomography) and tumor proliferation (green fluorescent protein [GFP] fluorescence). Microangiography demonstrates superior sensitivity (77.7 ± 6.4%) and specificity (98.2 ± 1.7%) over other imaging technologies (eg, optical coherence tomography) for tumor margin detection. Additionally, we report longitudinal in vivo imaging of tumor progression and show that the abrupt tumor cell proliferation did not occur until local capillary density and cerebral blood flow reached their peak approximately 2 weeks after tumor implantation. The unique capability of longitudinal multimodality imaging of tumor angiogenesis may provide new insights in tumor biology and in vivo assessment of the treatment effects on anti-angiogenesis therapy for brain cancer.

Synthesis and characterization of 64Cu- and Cy5.5-labeled tetraiodothyroacetic acid derivatives for tumor angiogenesis imaging

It was previously reported that tetraiodothyroacetic acid (tetrac) inhibits angiogenesis by binding to the cell surface receptor for thyroid hormone on integrin αVβ3. Therefore, we synthesized and evaluated two 64Cu-labeled tetrac derivatives and a Cy5.5-labeled tetrac derivative for tumor angiogenesis imaging. Tetrac was structurally modified to conjugate with 1,4,7,10-tetraazacyclododecane-N,N′,N″,N″′-tetraacetic acid (DOTA) via its hydroxy or carboxylic acid end, and the resulting DOTA-conjugated tetrac derivatives were then labeled with 64Cu. Tetrac was also conjugated with Cy5.5 via its carboxylic acid end. All three tetrac derivatives (1–3) exhibited greater inhibitory activity than tetrac against endothelial cell tube formation. The U87MG cell binding of [64Cu]2 showed a time-dependent increase over 24 h and it was inhibited by 38% at 4 h in the presence of tetrac, indicating specificity of [64Cu]2 to the thyroid hormone receptor site on integrin αVβ3. Positron emission tomography (PET) images of U87MG tumor-bearing mice injected with [64Cu]1 and [64Cu]2 revealed that high radioactivity accumulated in the tumors, and that the tumor uptake and tumor-to-nontarget uptake ratio were higher in small tumors than in large tumors. In addition, the Cy5.5-labeled tetrac derivative (3) displayed a strong near-infrared (NIR) signal in the tumors. Taken together, these results suggest that these ligands hold promise as imaging agents for visualization of tumor angiogenesis.

Preliminary biological evaluation of 68Ga-labeled cyclic RGD dimer as an integrin αvβ3-targeting radiotracer for tumor PET imaging

Radiolabeled cyclic arginine-glycine-aspartic acid (RGD) peptides have been widely prepared for noninvasive monitoring of tumor angiogenesis. The aim of this study was to explore and evaluate the feasibility of a novel 68Ga-labeled RGD peptide for tumor angiogenesis imaging. [68Ga]Ga-NOTA-PEG3-β-Glu-RGD2, a cyclic RGD dimer with a symmetric β-glutamate linker, was successfully designed and radiolabeled in high radiochemical yields. A series of experiments in vivo and in vitro were investigated to perform a preliminary evaluation and confirm good target at integrin αvβ3-positive tumor cells. The results suggest that [68Ga]Ga-NOTA-PEG3-β-Glu-RGD2 may be a promising radiotracer for positron emission tomography imaging of tumor angiogenesis.

PP#149 - Preliminary study on 64Cu-labeled tetraiodothyroacetic acid derivative for tumor angiogenesis imaging

PP#149 - Preliminary study on 64Cu-labeled tetraiodothyroacetic acid derivative for tumor angiogenesis imaging

Automated motion-artifact correction in an OCTA image using tensor voting approach.

Optical coherence tomography angiography (OCTA) is a promising tool for imaging subsurface microvascular networks owing to its micron-level resolution and high sensitivity. However, it is not uncommon that OCTA imaging suffers from strip artifacts induced by tissue motion. Although various algorithms for motion correction have been reported, a method that enables motion correction on a single en face OCTA image remains a challenge. In this study, we propose a motion correction approach based on microvasculature detection and broken gap filling. Unlike previous methods using registration to restore disturbed vasculature during motion artifact removal, tensor voting is performed in an individual projected image to connect the broken vasculature. Both simulation and in vivo 3D OCTA imaging of the mouse bladder are performed to validate the effectiveness of this method. A comparison of in vivo images before and after motion correction shows that our method effectively corrects tissue motion artifacts while preserving the continuity of vasculature network. Furthermore, in vivo results of this technique are presented to demonstrate its utility for imaging tumor angiogenesis in the mouse bladder.

(Invited) Water-Soluble Near-Infrared Fluorophores Emitting over 1000 Nm and Their Application to In Vivo Imaging in the Second Optical Window

Near-infrared (NIR) emitting fluorophores are widely used as bio-imaging probes for non-invasive visualization of deep-tissues at the whole body level, because of the high permeability and low absorption of NIR light in living tissues. Recently much attention has been paid for NIR fluorescence imaging at the wavelengths of 1000-1400 nm (second optical window) to obtain clearer deep-tissue images with high signal to background ratios. This is because that the NIR light with longer wavelengths (1000-1400 nm) is highly permeable with lower scattering compared with the conventional NIR light (700-1000 nm). In the second optical window, there are a very limited number of fluorophores that can be used for NIR fluorescence imaging. To date, single walled carbon nanotubes (SWNTs), PbS quantum dots (QDs) and Ag2S QDs, rare-earth metal doped nanoparticles (NPs) have been reported as NIR fluorophores for in vivo imaging in the second optical window. In this work, we synthesized several types of water-soluble NIR fluorophores, glutathione coated PbS QDs, glutathione coated Ag2S QDs, Er3+-doped NaYF4 nanoparticles (Er3+-NPs) and cholate-capped SWNTs that emit over 1000 nm. For the application of the NIR fluorophores to in vivo imaging, we examined their fluorescence brightness, particle size, and cytotoxicity. We found that among the NIR fluorophores, PbS QDs are the brightest fluorophore (quantum yield, 4 %) with no significant cytotoxicity. The fluorescence of Ag2S QDs, Er3+-NPs, and SWNTs was at least 50 times week compared with that of PbS QDs. We show the capability of the NIR fluorophores for in vivo imaging of cerebral blood vessels, tumor angiogenesis, lymph nodes, and phagocytic cell migration in mice.

Application of cNGR functionalized gold nanoparticle probe in CT imaging of breast cancer angiogenesis

Objective To prepare polyethylene glycol/cyclic asparagines-glycine-arginine functionalized gold nanoparticles (GNPs-PEG@cNGR) and evaluate their effectiveness in CT imaging of breast cancer angiogenesis. Methods The GNPs were synthesized by one-step reduction of chloroauric acid by sodium citrate. The thiolated PEG and cysteine-modified cNGR were coupled to the surface of GNPs through Au-S bonds, respectively. The GNPs-PEG@cNGR was characterized by transmission electron microscopy, Zeta potential/hydration particle size analyzer, and Fourier transform infrared spectrometer. The uptake and CT imaging effect of GNPs-PEG@cNGR were assessed by human umbilical vein endothelial cells (HUVEC) and human hepatoma cells (HepG2) positively expressed for aminopeptidase N (APN/CD13). The in vivo CT imaging effects on tumor angiogenesis and biocompatibility in mice of GNPs-PEG@cNGR were studied by BALB/c mouse model of 4T1 breast cancer. Results A specific CT molecular probe, i.e. GNPs-PEG@cNGR, was successfully constructed, which can target angiogenesis. The probe was spherical, with a hydration particle size of (35.7±1.0) nm and a Zeta potential of (-13.54±1.12) mV, and had good stability and biocompatibility. The GNPs-PEG@cNGR has good CT imaging results and can specifically target CD13-positive HUVEC and HepG2 cells. The CT imaging results in 4T1 breast cancer mice indicated that GNPs-PEG@cNGR could be specifically enriched in the tumor tissue after injection. The CT value of tumors in GNPs-PEG@cNGRz group was higher than that of GNPs-PEG group, and the difference was statistically significant (P<0.05). Conclusions GNPs-PEG@cNGR can specifically target CD13 positive cells and can be used as a CT contrast agent for imaging tumor angiogenesis. Key words: Cyclic asparagines-glycine-arginine; Gold nanoparticles; Breast cancer; Tumor angiogenesis; CT imaging

Tumor angiogenesis targeting and imaging using gold nanoparticle probe with directly conjugated cyclic NGR.

Angiogenesis is a vital process for the growth and metastasis of malignant tumor. Visualization of tumor angiogenesis is thus of great importance in the evaluation of biologic aggressiveness as well as monitoring of the response to anti-angiogenic therapy. Herein, we developed a probe based on gold nanoparticles (GNPs) directly surface-functionalized with a tumor-homing cyclized asparagine–glycine–arginine peptide (SH–cNGR) and carboxylpoly(ethylene glycol)thiol (SH–PEG–COOH) via Au–S bonds. The obtained GNPs–PEG@cNGR probe was used to target the aminopeptidase-N (APN/CD13), which overexpressed in the endothelium of tumor angiogenesis. The CD13 binding affinities of the peptides were assessed by a receptor binding assay based on HUVEC and HepG2 cell (e.g. fluorescence imaging and X-ray computed tomography (CT)). The tumor targeting efficacy and the distribution of the GNPs–PEG@cNGR in vivo were further evaluated in a subcutaneous 4T1 xenograft model by CT imaging and immunohistochemistry study. These results showed that the GNPs–PEG@cNGR rapidly and specifically bound to the tumor vasculature after intravenous injection. Quantitative studies demonstrated that GNPs–PEG@cNGR showed significantly higher and faster tumor uptake after intravenous injection compared to unlabeled GNPs–PEG. Moreover, the distribution of tumor enhancement was consistent with the spatial distribution of angiogenic blood. These results suggest that the designed GNPs–PEG@cNGR probe may serve, in principle, as a promising CT contrast agent for targeted angiogenesis imaging and quantitative analysis.

Molecular Magnetic Resonance and Ultra Sound Imaging of Tumor Angiogenesis

Molecular Magnetic Resonance and Ultra Sound Imaging of Tumor Angiogenesis

A novel molecular agent for glioma angiogenesis imaging.

Gliomas are rich in blood vessels and are the most primary and malignant type of brain tumor affecting the central nervous system. A few fluorine-18 (F)-labeled imaging agents can be used for imaging of tumor angiogenesis. In the current study, F-labeled recombinant human endostatin (rh-endostatin) was developed and evaluated as a probe for PET imaging of tumor angiogenesis. F-fluorobenzoyl-endostatin (F-FB-endostatin) was synthesized from radiolabeling of rh-endostatin with N-succinimidyl-4-F-fluorobenzoate produced by a facile module-assisted radiosynthesis procedure. Blocking studies were used to measure the relative affinities of F-FB-endostatin to human glioblastoma U87MG cells in tumor tissues rich with vessels. In addition, biodistribution, metabolic stability, and small-animal PET imaging studies were carried out with F-FB-endostatin using Institute of Cancer Research and U87MG tumor-bearing mice. Noninvasive small-animal PET imaging indicated that F-FB-endostatin showed rapid and good tumor uptake. The probe was rapidly cleared from the blood and most organs, resulting in excellent tumor-to-normal tissue contrasts. Tumor uptake and rapid clearance were further confirmed with biodistribution studies. Metabolite assays showed that the probe was highly stable, making it suitable for in-vivo applications. F-FB-endostatin shows promising in-vivo properties. Therefore, the promising properties of F-FB-endostatin indicate that this probe can be a powerful tool to evaluate the antiangiogenic therapy for gliomas and thus warrants further investigation as a novel PET probe for imaging of tumor angiogenesis.

Magnetic resonance imaging of tumor angiogenesis using dual-targeting RGD10-NGR9 ultrasmall superparamagnetic iron oxide nanoparticles.

Using RGD10-NGR9 dual-targeting superparamagnetic iron oxide nanoparticles to evaluate their potential value in tumor angiogenesis magnetic resonance imaging (MRI) and the biodistribution in vitro and in vivo. Dual-targeting RGD10-NGR9 ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles were designed and synthesized in our previous study. In vitro, prussian blue staining and phenanthroline colorimetry were conducted to evaluate binding affinity and adsorption of dual-targeting USPIO nanoparticles to αvβ3-integrin/APN positive cells. In vivo, a xenograft mouse tumor model was used to evaluate the potential of the dual-targeting nanoparticles as an MRI contrast agent. After intravenous injection, the contrast-to-noise ratio (CNR) values of MR images obtained were calculated at predetermined time-points. The iron level was detected to access the biodistribution and plasma half-time. In vitro, dual-targeting USPIO nanoparticles bound to proliferating human umbilical vein endothelia cells with high specificity. In vivo, contrast MRI of xenograft mice using dual-targeting nanoparticles demonstrated a significant decrease in signal intensity and a greater increase in CNR than standard MRI and facilitated the imaging of tumor angiogenesis in T2*WI. In terms of biodistribution, dual-targeting USPIO nanoparticles increased to 1.83 times in tumor lesions as compared to the control. And the plasma half-time was about 6.2h. A novel RGD10-NGR9 dual-targeting USPIO has a great potential value as a contrast agent for the identification of tumor angiogenesis on MRI, according to the high specific affinity in vitro and in vivo.

Critical Review—Water-Soluble Near-Infrared Fluorophores Emitting over 1000 nm and Their Application to In Vivo Imaging in the Second Optical Window (1000–1400 nm)

Near-infrared (NIR) emitting fluorophores are widely used as bio-imaging probes for non-invasive visualization of deep-tissues at the whole body level, because of the high permeability and low absorption of NIR light in living tissues. Recently much attention has been paid for NIR fluorescence imaging at the wavelengths of 1000–1400 nm (second optical window) to obtain clearer deep-tissue images with high signal to background ratios. This is because that the NIR light with longer wavelengths (1000–1400 nm) is highly permeable with lower scattering compared with the conventional NIR light (700–1000 nm). In the second optical window, there are a very limited number of fluorophores that can be used for NIR fluorescence imaging. To date, single walled carbon nanotubes (SWNTs), PbS quantum dots (QDs) and Ag2S QDs, rare-earth metal doped nanoparticles (NPs) have been reported as NIR fluorophores for in vivo imaging in the second optical window. In this work, we synthesized several types of water-soluble NIR fluorophores, glutathione coated PbS QDs, glutathione coated Ag2S QDs Er3+-doped NaYF4 nanoparticles (Er3+-NPs) and cholate-capped SWNTs that emit over 1000 nm. For the application of the NIR fluorophores to in vivo imaging, we examined their fluorescence brightness, particle size, and cytotoxicity. We found that among the NIR fluorophores, PbS QDs are the brightest fluorophore (quantum yield, 4%) with no significant cytotoxicity. The fluorescence of Ag2S QDs, Er3+-NPs, and SWNTs was at least 50 times week compared with that of PbS QDs. We show the capability of the NIR fluorophores for in vivo imaging of cerebral blood vessels, tumor angiogenesis, lymph nodes, and phagocytic cell migration in mice.