Sentinel Lymph Node Imaging Research Articles

Erratum to: Role of intraoperative sentinel node imaging in head and neck cancer

Erratum to: Role of intraoperative sentinel node imaging in head and neck cancer

Synthesis and evaluation of Cy5.5-Rit tracer for specific near-infrared fluorescence imaging of sentinel lymph node

Sentinel lymph nodes biopsy (SLNB) is a critically important technique to determine the metastatic status of primary breast cancer. Here we reported the new use of a conjugate, Cy5.5-Rituximab (Cy5.5-Rit), which is specific toward the CD20 receptor, as an imaging agent for non-invasive near-infrared fluorescence (NIRF) imaging of sentinel lymph nodes (SLN). The conjugate, Cy5.5-Rit, was synthesized with the ratio of dye to Rituximab close to 1.0. Both gel electrophoresis and mass spectrometry analysis confirmed the molecular integrity of Cy5.5-Rit. For in vivo NIRF imaging, the conjugate stayed in SLN as long as 9days post injection. The in vivo imaging results of SLN targeting were also confirmed by in vitro HE stain. In addition, the direct fluorescence signal of dissected lymph node demonstrated that Cy5.5-Rit binds to the surface of lymph node cells. All of these results showed that the conjugate Cy5.5-Rit has potential for non-invasive optical imaging of SLN.

Encapsulated Conjugated Oligomer Nanoparticles for Real-Time Photoacoustic Sentinel Lymph Node Imaging and Targeted Photothermal Therapy.

Noninvasive and nonionizing imaging of sentinel lymph nodes (SLN) is highly desirable for the detection of breast cancer metastasis through sentinel lymph node biopsy. Photoacoustic (PA) imaging is an emerging imaging technique that can serve as a suitable approach for SLN imaging. Herein, novel conjugated oligomer based nanoparticles (NPs) with strong NIR absorption, good biocompatibility, excellent PA contrast, and good photothermal conversion efficiency are reported. Real-time PA imaging of SLN reveals high resolution of the NPs via injection from the left forepaw pad. In addition, the surface functionalized NPs can target breast cancer cells and kill them efficiently and specifically through photothermal therapy upon 808 nm laser irradiation. This work shows great potential of the nanoparticle PA contrast agent to serve as a multifunctional probe for photothermal therapy at SLNs to achieve the inhibition of cancer cell metastasis in the near future.

Preparation study of indocyanine green-rituximab: A new receptor-targeted tracer for sentinel lymph node in breast cancer.

An appropriate receptor-targeted tracer for sentinel lymph node biopsy (SLNB) was prepared. We combined the fluorescence tracer (Indocyanine green, ICG) with Rituximab (a chimeric human/murine monoclonal antibody targeting the CD20 antigen on the surface of lymphocyte) directly to produce a new tracer (ICG-Rituximab). When the new tracer drains to the lymph node, Rituximab will combine with CD20 receptor on the B-cell surface in the lymph node. If the statue of antibody-receptor connection does not reach saturation, the number of Rituximab is less than CD20. With this appropriate injection dose, the new tracer could only stay in sentinel lymph node (SLN) and make it imaging. Positive fluorescence SLN was detected 12 minutes after injection with no other organs imaging. The imaging of SLN was stable and clear for 20–24 hours. Due to SLN stained with more ICG than the lymphatic vessel, the fluorescence situation of SLN would be brighter than the vessel. The surgeon can detect the positive fluorescence SLN easily without following the fluorescence imaging lymphatic vessel. The results of our preliminary study showed that the new tracer might be useful for improving SLN imaging and worth further clinical study. SLNB with the new tracer could be a convenient method for detecting SLN and would become a standard performance in clinical practice.

Sentinel Lymph Node Imaging and Lymphatic Mapping

Sentinel Lymph Node Imaging and Lymphatic Mapping

1060 Magnetic resonance sentinel lymph node imaging in prostate cancer using intraprostatic injection of superparamagnetic iron oxide nanoparticles: The first in-human results

1060 Magnetic resonance sentinel lymph node imaging in prostate cancer using intraprostatic injection of superparamagnetic iron oxide nanoparticles: The first in-human results

Indocyanine green-incorporated exosomes for improved in vivo imaging of sentinel lymph node

For improved physical stability and fast accumulation in sentinel lymph nodes in vivo, indocyanine green (ICG) was incorporated into exosomes (EXOs) to form a novel ICG-based near-infrared fluorescence probe. Compared with free ICG, prepared ICG-TBAI-encapsulated EXOs (ICG/EXOs) smaller than 50 nm had greater physicochemical stability in aqueous solution when exposed to light at 37 °C. In addition, sentinel lymph nodes were visualized within minutes with ICG/EXOs at a low ICG dose (0.05 mg/kg) owing to its well-controlled size distribution. Taken together, the results show that ICG/EXOs are effective biocompatible and sensitive near-infrared probes for real-time sentinel lymph node imaging in vivo.

Dendrimer-based sentinel lymph node imaging

Event Abstract Back to Event Dendrimer-based sentinel lymph node imaging Chie Kojima1*, Yuichiro Niki1*, Mikako Ogawa2* and Yasuhiro Magata3* 1 Osaka Prefecture University, Dept. Applied Chemistry, Japan 2 Hokkaido University, Faculty of Pharmaceutical Sciences, Japan 3 Hamamatsu University School of Medicine, Medical Photonics Research Center, Japan Introduction: Dendrimers have highly controllable size and surface properties, which are quite different from linear polymers. Dendrimers are a potent imaging probe, because various kinds of detectable probes can be conjugated to terminal functional groups of a single dendrimer molecule. Previously, we have prepared dendrimers conjugating gadolinium-chelates and radioactive indium-chelates for magnetic resonance imaging (MRI) and singly photon emission computed tomography (SPECT)[1],[2]. A sentinel lymph node is the first lymph node to which cancer cells are spread. Detection of sentinel lymph node is important for cancer therapy and diagnosis. However, there are only a few reports on dendrimer-based imaging agents for sentinel lymph node imaging. In this study, twelve radiolabeled dendrimers with different sizes and different surfaces were prepared as dendrimer imaging agents for SPECT imaging. These dendrimer imaging agents were intradermally injected into rats, followed by the biodistribution analysis and the SPECT imaging of lymph nodes, to obtain knowledge on the optimized dendrimer structure for sentinel lymph node imaging. Results and Discussion: Several chelate molecules (DTPA) were conjugated to amino-terminal polyamidoamine (PAMAM) dendrimers of generation (G) 2, 4, 6 and 8 to obtain cationic dendrimers. The residual terminal amino groups were acetylated (Ac) and carboxylated to obtain nonionic and anionic dendrimers, respectively. These compounds were characterized by NMR, UV-Vis spectrometry and DLS. The size increased with increasing the dendrimer generation, and the zeta potential was largely affected by the terminal group. These dendrimers were labeled with radioactive 111In3+ ions, followed by the intradermal injection into rats. The biodistribution after 1, 6 and 24 h was analyzed. Small dendrimers (G2 and G4) were mostly localized in the kidney. Cationic dendrimers of larger than G4 retained at the injection site. Acetylated dendrimers were flowed into blood. Large and anionic dendrimers (G8-COOH, G6-COOH and G4-COOH) were efficiently distributed in the sentinel lymph node (Fig. 1). The SPECT imaging by injecting G6-COOH succeeded detection of the sentinel lymph nodes (Fig. 2). Fluorescent dye-labeled dendrimers were also prepared, and fluorescent imaging of thin section of the sentinel lymph node was performed. Interestingly, these dendrimers were not recognized by immune cells such as macrophages and T-cells. Thus, it is likely that the medium flow speed of the carboxyl-dendrimers of larger than G4 affected the accumulation of the sentinel lymph node. Conclusion: We succeeded the sentinel lymph node imaging by using carboxy-terminated dendrimers with larger than G4 (larger than 6 nm). These dendrimers are useful for sentinel lymph node biopsy.

Time-lapse imaging of sentinel lymph node using indocyanine green with near-infrared fluorescence imaging in early endometrial cancer.

ObjectiveIndocyanine green with near-infrared fluorescence imaging (NIR-ICG) is a new tracer modality in the limelight used for lymphatic mapping. The advantage of this method is to provide real-time image during surgery. To use ICG for image guided lymph node dissection, a surgeon needs to know initial appearing time and duration.MethodsA 52-year-old woman undertook surgery diagnosed with endometrial cancer. She had no past medical history and her body mass index was 25.3 kg/m2. Preoperative magnetic resonance imaging examination revealed 2.7 cm sized cancerous mass in the endometrial cavity with superficial myometrial invasion without lymph node enlargement. Four mL (1.25 mg/mL) of ICG solution was prepared for injection. For each site, 1 mL of solution was injected superficially, 2–3 mm into the cervical submucosa and another 1 mL was injected deep, 1–2 cm into the stroma of the cervix [12]. We recorded video with 30° 10 mm scope equipped with a specific lens and light source emitting both visible and NIR light (KARL STORZ GmbH & Co. KG, Tuttlingen, Germany).ResultsPelvic lymph node was visualized from around 5 minutes. ICG was dispersed into organs after hysterectomy (53 minutes after ICG injection), yet we could clearly identify sentinel lymph node (SLN). Pathology revealed endometriod adenocarcinoma grade I, myometrial invasion with less than half of myometrium and no lymph node metastasis.ConclusionCervical injection of ICG provides good visualization of SLN from 5 minutes to over an hour. Our film gives an idea about time management to make a plan for surgery and not to miss SNLs.

Biodegradable Nitrogen-Doped Carbon Nanodots for Non-Invasive Photoacoustic Imaging and Photothermal Therapy.

Multifunctional nanoparticles have been widely investigated for biomedical applications, such as imaging, therapy, and drug delivery. Especially, photoactive nanoparticles have received great attention as theranostic agents because of their heat-generating abilities after exposure to laser irradiation. However, photostability and safety issues have been the technical hurdles for further clinical applications. Here, we designed nitrogen (N)-doped carbon nanodots (N-CNDs) that have strong absorption in the near-infrared region, high photostability, and excellent biodegradability. Optimized N-CNDs can be utilized not only as a new photoacoustic (PA) imaging agent but also as a superior photothermal therapy (PTT) agent in vivo because of their strong optical absorption at a specific wavelength. We used N-CNDs to perform in vivo/ex vivo noninvasive PA imaging of sentinel lymph nodes via local delivery and performed PTT for cancer ablation therapy. Finally, biodegradation and renal clearance were confirmed by performing whole-body PA monitoring and a degradation test.

Bright and Stable Near-Infrared Pluronic-Silica Nanoparticles as a Contrast Agent for in vivo Optical Imaging.

Near-infrared (NIR) fluorescent nanostructured materials have emerged as novel contrast agents for non-invasive bioimaging. Here we report a class of polymer-silica nanoparticles doped with a NIR fluorescent dye prepared through a facile one-pot strategy. Hydrophobic NIR fluorescent dyes such as IR 780 iodide could be easily encapsulated into the micellar core by self-assembly of amphiphilic triblock copolymer Pluronic F127. When subsequently adding silane in aqueous solution, nanoparticles with a cross-linked core and a hydrophilic PEG shell were formed. The structure of the as-obtained nanoparticles was confirmed by transmission electron microscopy (TEM) and dynamic light scattering (DLS). The nanoparticles exhibited a well-defined spherical structure with a mean diameter of approximately 30 nm, and excellent monodispersity and stability in aqueous solution. In addition, the photo-stability of IR 780 was significantly improved by encapsulation into the nanoparticles. In vitro MTT assay with cell lines HEK293 and A431 demonstrated that the IR 780 loaded nanoparticles (termed as IR780@NPs) were biocompatible. In vivo sentinel lymph node imaging revealed that the fluorescent intensity and retention time of the IR780@NPs were clearly superior to its constituent free dye, making it amenable to in vivo bioimaging. Further in vivo tumor imaging indicated that IR780@NPs have a longer retention time and much higher accumulation on the tumor site compared to free dye after intravenous administration. Overall this hydrophilic NIR fluorescent contrast agent exhibits excellent photophysical characteristics and low cytotoxicity, and holds a strong promise for a variety of applications including bioimaging and therapy.

Sentinel lymph node imaging guided IMRT for prostate cancer: Individualized pelvic radiation therapy versus RTOG guidelines

Purpose/ObjectivesCurrent Radiation Therapy Oncology Group (RTOG) guidelines for pelvic radiation therapy are based on general anatomic boundaries. Sentinel lymph node (SLN) imaging can identify potential sites of lymph node involvement. We sought to determine how tailored radiation therapy fields for prostate cancer would compare to standard RTOG-based fields. Such individualized radiation therapy could prioritize the most important areas to irradiate while potentially avoiding coverage in areas where critical structures would be overdosed. Individualized radiation therapy could therefore increase the therapeutic index of pelvic radiation therapy. Methods and materialsTen intermediate or high-risk prostate cancer patients received androgen deprivation therapy with definitive radiation therapy, including an SLN imaging–tailored elective nodal volume (ENV). For dosimetric analyses, the ENV was recontoured using RTOG guidelines (RTOG_ENV) and on SLNs alone (SLN_ENV). Separate intensity modulated radiation therapy (IMRT) plans were optimized using RTOG_ENV and SLN_ENV for each patient. Dosimetric comparisons for these IMRT plans were performed for each patient. Dose differences to targets and critical structures among the different IMRT plans were calculated. Distributions of dose parameters were analyzed using non-parametric methods. ResultsSixty percent of patients had SLNs outside of the RTOG_ENV. The larger volume IMRT plans covering SLN imaging–tailored elective nodal volume exhibited no significant dose differences versus plans covering RTOG_ENV. IMRT plans covering only the SLNs had significantly lower doses to bowel and femoral heads. ConclusionsSLN-guided pelvic radiation therapy can be used to either treat the most critical nodes only or as an addition to RTOG guided pelvic radiation therapy to ensure that the most important nodes are included.

Pelvic lymph node dissection in prostate cancer: indications, extent and tailored approaches.

The purpose of this study is to review the current literature concerning the indication of pelvic lymph node dissection (PLND), its extent and complications in prostate cancer (PCa) staging, the available tools, and the future perspectives to assess the risk of lymph node invasion (LNI). A literature review was performed using the Medline, Embase, and Web of Science databases. The search strategy included the terms pelvic lymph nodes, PLND, radical prostatectomy, prostate cancer, lymph node invasion, biochemical recurrence, staging, sentinel lymph node dissection, imaging, and molecular markers. PLND currently represents the gold standard for nodal staging in PCa patients. Available imaging techniques are characterized by poor accuracy in the prediction of LNI before surgery. On the contrary, an extended PLND (ePLND) would result into proper staging in the majority of the cases. Several models based on preoperative disease characteristics are available to assess the risk of LNI. Although ePLND is not associated with a substantial risk of severe complications, up to 10% of the men undergoing this procedure experience lymphoceles. Concerns over potential morbidity of ePLND led many authors to investigate the role of sentinel lymph node dissection in order to prevent unnecessary ePLND. Finally, the incorporation of novel biomarkers in currently available tools would improve our ability to identify men who should receive an ePLND. Nowadays, the most informative tools predicting LNI in PCa patients consist in preoperative clinical nomograms. Sentinel lymph node dissection still remains experimental and novel biomarkers are needed to identify patients at a higher risk of LNI.

Reducing perceived pain levels during nonbreast lymphoscintigraphy.

The aim of this study was to quantify the reduction of perceived pain levels during lymphoscintigraphy for melanoma by altering the pH of the Tc-sulfur colloid to near the physiologic value of 7.40. This is an institutional review board- and Food and Drug Administration-approved randomized, double-blinded, prospective crossover trial, registered with clinicaltrials.org. Before beginning the procedure and after signing informed consent, 60 serial enrollees presenting for sentinel lymph node imaging of melanoma of the thorax and appendicular structures completed a questionnaire addressing background information, administered by a research support nurse.An investigator (N.H.) prepared the injections to be used and labeled them such that no one else could discover which injections contained standard-of-care solution and which contained the pH-altered solution (buffered to near pH 7.40 using sodium bicarbonate).After each injection, the enrollee was asked by a research support nurse to quantify the pain of each injection using a scale of 0 to 10. The injection site location (head, thorax, appendicular structures, and other) was also recorded. Sixty subjects were enrolled in the study, of which 57 had complete data. On average, there was a significant mean (SD) decrease of 1.42 (2.17) points (95% confidence interval, 0.85-2.00) on a pain scale of 0 to 10 when the buffered injections were used as compared with the standard-of-care injections (P < 0.0001). Ordering of injections did not significantly affect perceived pain scores. The use of sodium bicarbonate to buffer the pH of Tc-sulfur colloid to near the physiologic value of 7.40 significantly reduced perceived pain levels during nonbreast lymphoscintigraphy.

Assessment of the performance of small field of view gamma cameras for sentinel node imaging.

To develop a method for the assessment of small field of view (SFOV) gamma cameras using a novel phantom designed to simulate the localization of sentinel nodes in the presence of a high-activity injection site. The phantom consisted of a cube-shaped acrylic glass support frame. Sixteen acrylic glass plates and nine bars were stacked within the frame to allow a variable configuration of the simulated node depth and node-to-injection site separation. Syringes filled with Tc were used to simulate activity at the injection site and node. Scintigraphic imaging was carried out and the images were assessed subjectively and quantitatively through calculation of the contrast-to-noise ratio. The detection performance of an SFOV gamma camera was then compared with that of a large field of view gamma camera. The detectability studies showed that the SFOV gamma camera could detect low activity in nodes by visual examination of images and with contrast-to-noise ratios ranging from 3 to 62. In particular, the phantom showed the limits of node detection using an SFOV gamma camera over activity ratios less than 1 : 100 and at depths below 45 mm with 25 mm of node-to-injection site separation. Visual subjective assessment of images acquired under the same conditions showed that the SFOV gamma camera was superior to a large field of view camera for the detection of nodes at a node-to-injection site separation of 25 mm. A low-cost phantom has been designed and fabricated that provides a versatile method for the assessment of SFOV gamma cameras intended for sentinel node imaging.

Optimization of dendrimer structure for sentinel lymph node imaging: Effects of generation and terminal group

The detection of the sentinel lymph node (SLN), the first lymph node draining tumor cells, is important in cancer diagnosis and therapy. Dendrimers are synthetic macromolecules with highly controllable structures, and are potent multifunctional imaging agents. In this study, 12 types of dendrimer of different generations (G2, G4, G6, and G8) and different terminal groups (amino, carboxyl, and acetyl) were prepared to determine the optimal dendrimer structure for SLN imaging. Radiolabeled dendrimers were intradermally administrated to the right footpads of rats. All G2 dendrimers were predominantly accumulated in the kidney. Amino-terminal, acetyl-terminal, and carboxyl-terminal dendrimers of greater than G4 were mostly located at the injection site, in the blood, and in the SLN, respectively. The carboxyl-terminal dendrimers were largely unrecognized by macrophages and T-cells in the SLN. Finally, SLN detection was successfully performed by single photon emission computed tomography imaging using carboxyl-terminal dendrimers of greater than G4. From the Clinical EditorThe early detection of tumor cells in the sentinel draining lymph nodes (SLN) is of utmost importance in terms of determining cancer prognosis and devising treatment. In this article, the authors investigated various formulations of dendrimers to determine the optimal one for tumor detection. The data generated from this study would help clinicians to fight the cancer battle in the near future.

γ-Tilmanocept, a New Radiopharmaceutical Tracer for Cancer Sentinel Lymph Nodes, Binds to the Mannose Receptor (CD206).

γ-Tilmanocept ((99m)Tc-labeled-tilmanocept or [(99m)Tc]-tilmanocept) is the first mannose-containing, receptor-directed, radiolabeled tracer for the highly sensitive imaging of sentinel lymph nodes in solid tumor staging. To elucidate the mannose-binding receptor that retains tilmanocept in this microenvironment, human macrophages were used that have high expression of the C-type lectin mannose receptor (MR; CD206). Cy3-labeled tilmanocept exhibited high specificity binding to macrophages that was nearly abolished in competitive inhibition experiments. Furthermore, Cy3-tilmanocept binding was markedly reduced on macrophages deficient in the MR by small interfering RNA treatment and was increased on MR-transfected HEK 293 cells. Finally, confocal microscopy revealed colocalization of Cy3-tilmanocept with the macrophage membrane MR and binding of labeled tilmanocept to MR(+) cells (macrophages and/or dendritic cells) in human sentinel lymph node tissues. Together these data provide strong evidence that CD206 is a major binding receptor for γ-tilmanocept. Identification of CD206 as the γ-tilmanocept-binding receptor enables opportunities for designing receptor-targeted advanced imaging agents and therapeutics for cancer and other diseases.

Synthesis, Characterization, and Application of Core-Shell Co0.16Fe2.84O4@NaYF4(Yb, Er) and Fe3O4@NaYF4(Yb, Tm) Nanoparticle as Trimodal (MRI, PET/SPECT, and Optical) Imaging Agents.

Multimodal nanoparticulate materials are described, offering magnetic, radionuclide, and fluorescent imaging capabilities to exploit the complementary advantages of magnetic resonance imaging (MRI), positron emission tomography/single-photon emission commuted tomography (PET/SPECT), and optical imaging. They comprise Fe3O4@NaYF4 core/shell nanoparticles (NPs) with different cation dopants in the shell or core, including Co0.16Fe2.84O4@NaYF4(Yb, Er) and Fe3O4@NaYF4(Yb, Tm). These NPs are stabilized by bisphosphonate polyethylene glycol conjugates (BP-PEG), and then show a high transverse relaxivity (r2) up to 326 mM–1 s–1 at 3T, a high affinity to [18F]-fluoride or radiometal-bisphosphonate conjugates (e.g., 64Cu and 99mTc), and fluorescent emissions from 500 to 800 nm under excitation at 980 nm. The biodistribution of intravenously administered particles determined by PET/MR imaging suggests that negatively charged Co0.16Fe2.84O4@NaYF4(Yb, Er)-BP-PEG (10K) NPs cleared from the blood pool more slowly than positively charged NPs Fe3O4@NaYF4(Yb, Tm)-BP-PEG (2K). Preliminary results in sentinel lymph node imaging in mice indicate the advantages of multimodal imaging.

A tri-modal molecular imaging agent for sentinel lymph node mapping

IntroductionWe report an “instant kit” method to radiolabel fluorescent-tilmanocept with 68Ga and 99mTc for tri-modal molecular imaging of sentinel lymph nodes (SLNs). MethodsSolutions of sodium acetate, 68GaCl3 and Na99mTcO4 were added successively to a “kit vial” containing lyophilized 800CW-tilmanocept, SnCl2, trehalose and ascorbic acid. After a 30-min incubation, the pH was neutralized with PBS. No purification was required. Radiochemical and fluorescence purity was measured by HPLC and ITLC techniques. In vitro stability was measured by standing gel chromatography (SGC) and ITLC by a 100-fold dilution 0.25h after radiolabeling. In vivo stability was measured by SGC and ITLC after an 11h incubation in human plasma. A dose (0.1nmol, ~1MBq 68Ga, ~25MBq 99mTc) was injected to the footpad of 4 mice. Popliteal SLNs were imaged by PET and fluorescence imaging systems at 0.5, 24, 48, 72h, then excised and assayed for 99mTc. ResultsRadiochemical and fluorescent purity exceeded 98%. The in vitro stability assay demonstrated high irreversibility of both radiolabels and the fluorescent label, and in vivo stability assay demonstrated high stability of the technetium and fluorescent labels to plasma metabolism. Popliteal SLNs were identified by PET and fluorescence imaging within 0.5h of injection. SLN fluorescence intensity remained constant for 72h, when ~1% of the injected dose resided in the SLN. ConclusionsFluorescent-labeled tilmanocept can be radiolabeled with 68Ga and 99mTc by the sequential addition of each generator eluate to a lyophilized kit. The resulting tri-modal agent provides: PET images for pre-operative SLN mapping, fluorescence imaging up to 72hours after injection, and quantitative radiometric measurement of SLN accumulation after excision.

Dual-Modality Noninvasive Mapping of Sentinel Lymph Node by Photoacoustic and Near-Infrared Fluorescent Imaging Using Dye-Loaded Mesoporous Silica Nanoparticles.

The imaging of sentinel lymph nodes (SLNs), the first defense against primary tumor metastasis, has been considered as an important strategy for noninvasive tracking tumor metastasis in clinics. In this study, we developed an imaging contrast system based on fluorescent dye-loaded mesoporous silica nanoparticles (MSNPs) that integrate near-infrared (NIR) fluorescent and photoacoustic (PA) imaging modalities for efficient SLN mapping. By balancing the ratio of dye and nanoparticles for simultaneous optimization of dual-modality imaging (NIR and PA), the dye encapsulated MSNP platform was set up to generate both a moderate NIR emission and PA signals simultaneously. Moreover, the underlying mechanisms of the relevance between optical and PA properties were discovered. Subsequently, dual-modality imaging was achieved to visualize tumor draining SLNs up to 2 weeks in a 4T1 tumor metastatic model. Obvious differences in uptake rate and contrast between metastatic and normal SLNs were observed both in vivo and ex vivo. Based on all these imaging data, it was demonstrated that the dye-loaded MSNPs allow detection of regional lymph nodes in vivo with time-domain NIR fluorescent and PA imaging methods efficiently.