Dynamic Near-infrared Imaging Research Articles

A rapid dynamic in vivo near-infrared fluorescence imaging assay to track lung vascular permeability after acute radiation injury.

To develop a dynamic in vivo near-infrared (NIR) fluorescence imaging assay to quantify sequential changes in lung vascular permeability-surface area product (PS) in rodents. Dynamic NIR imaging methods for determining lung vascular permeability-surface area product were developed and tested on non-irradiated and 13 Gy irradiated rats with/without treatment with lisinopril, a radiation mitigator. A physiologically-based pharmacokinetic (PBPK) model of indocyanine green (ICG) pulmonary disposition was applied to in vivo imaging data and PS was estimated. In vivo results were validated by five accepted assays: ex vivo perfused lung imaging, endothelial filtration coefficient (Kf) measurement, pulmonary vascular resistance measurement, Evan's blue dye uptake, and histopathology. A PBPK model-derived measure of lung vascular permeability-surface area product increased from 2.60 ± 0.40 [CL: 2.42-2.78] mL/min in the non-irradiated group to 6.94 ± 8.25 [CL: 3.56-10.31] mL/min in 13 Gy group after 42 days. Lisinopril treatment lowered PS in the 13 Gy group to 4.76 ± 6.17 [CL: 2.12-7.40] mL/min. A much higher up to 5× change in PS values was observed in rats exhibiting severe radiation injury. Ex vivo Kf (mL/min/cm H2O/g dry lung weight), a measure of pulmonary vascular permeability, showed similar trends in lungs of irradiated rats (0.164 ± 0.081 [CL: 0.11-0.22]) as compared to non-irradiated controls (0.022 ± 0.003 [CL: 0.019-0.025]), with reduction to 0.070 ± 0.035 [CL: 0.045-0.096] for irradiated rats treated with lisinopril. Similar trends were observed for ex vivo pulmonary vascular resistance, Evan's blue uptake, and histopathology. Our results suggest that whole body dynamic NIR fluorescence imaging can replace current assays, which are all terminal. The imaging accurately tracks changes in PS and changes in lung interstitial transport in vivo in response to radiation injury.

Erratum: Methods for detecting host genetic modifiers of tumor vascular function using dynamic near-infrared fluorescence imaging: errata.

[This corrects the article on p. 543 in vol. 9, PMID: 29552392.].

Methods for detecting host genetic modifiers of tumor vascular function using dynamic near-infrared fluorescence imaging.

Vascular supply is a critical component of the tumor microenvironment (TME) and is essential for tumor growth and metastasis, yet the endogenous genetic modifiers that impact vascular function in the TME are largely unknown. To identify the host TME modifiers of tumor vascular function, we combined a novel genetic mapping strategy [Consomic Xenograft Model] with near-infrared (NIR) fluorescence imaging and multiparametric analysis of pharmacokinetic modeling. To detect vascular flow, an intensified cooled camera based dynamic NIR imaging system with 785 nm laser diode based excitation was used to image the whole-body fluorescence emission of intravenously injected indocyanine green dye. Principal component analysis was used to extract the spatial segmentation information for the lungs, liver, and tumor regions-of-interest. Vascular function was then quantified by pK modeling of the imaging data, which revealed significantly altered tissue perfusion and vascular permeability that were caused by host genetic modifiers in the TME. Collectively, these data demonstrate that NIR fluorescent imaging can be used as a non-invasive means for characterizing host TME modifiers of vascular function that have been linked with tumor risk, progression, and response to therapy.

Liposomal Encapsulation Enhances In Vivo Near Infrared Imaging of Exposed Phosphatidylserine in a Mouse Glioma Model

We have previously demonstrated that exposed phosphatidylserine (PS) on tumor vascular endothelial cells is highly tumor specific, and development of the PS targeted near infrared (NIR) optical probe enables successful in vivo optical imaging of U87 gliomas in a mouse model. Liposomes have been widely used as a nanovector for delivery of chemotherapeutics and imaging contrast agents due to their high payload and longer circulation time. In the current study, we have fabricated PS-targeted liposomal nanoprobes encapsulating a NIR dye, IRDye® 800CW, aiming to enhance PS-targeted tumor imaging. Hydrophilic 800CW dye was packed into the core of polyethylene glycol (PEG)-coated liposomes functionalized with F(ab’)2 fragments of PGN635, a fully human monoclonal antibody that binds PS. As expected, in vivo dynamic NIR imaging revealed significantly improved tumor/normal contrast (TNR = 20 ± 3; p < 0.01) of subcutaneous U87 gliomas in mice after injection of the liposomal nanoprobes. Markedly enhanced TNR was observed after the tumors were irradiated to increase PS exposure (TNR = 48 ± 6; p < 0.05). Intriguingly, the liposomal nanoprobes, PGN-L-800CW showed distinct biodistribution and pharmacokinetics compared to the 800CW-PGN probes used in our previous study. Our data further suggest the usefulness of PS-targeted imaging probes for sensitive tumor detection and the potential of utilizing liposomal platform for glioma theranostics.

Dynamic near-infrared imaging reveals transient phototropic change in retinal rod photoreceptors

Stiles-Crawford effect (SCE) is exclusively observed in cone photoreceptors, but why the SCE is absent in rod photoreceptors is still a mystery. In this study, we employed dynamic near infrared light imaging to monitor photoreceptor kinetics in freshly isolated frog and mouse retinas stimulated by oblique visible light flashes. It was observed that retinal rods could rapidly (onset: ∼10 ms for frog and 5 ms for mouse; time-to-peak: ∼200 ms for frog and 30 ms for mouse) shift toward the direction of the visible light, which might quickly compensate for the loss of luminous efficiency due to oblique illumination. In contrast, such directional movement was negligible in retinal cones. Moreover, transient rod phototropism could contribute to characteristic intrinsic optical signal (IOS). We anticipate that further study of the transient rod phototropism may not only provide insight into better understanding of the nature of vision but also promise an IOS biomarker for functional mapping of rod physiology at high resolution.

Non-invasive dynamic near-infrared imaging and quantification of vascular leakage in vivo

Preclinical vascular research has been hindered by a lack of methods that can sensitively image and quantify vascular perfusion and leakage in vivo. In this study, we have developed dynamic near-infrared imaging methods to repeatedly visualize and quantify vascular leakage in mouse skin in vivo, and we have applied these methods to transgenic mice with overexpression of vascular endothelial growth factors VEGF-A or -C. Near-infrared dye conjugates were developed to identify a suitable vascular tracer that had a prolonged circulation lifetime and slow leakage into normal tissue after intravenous injection. Dynamic simultaneous imaging of ear skin and a large blood vessel in the leg enabled determination of the intravascular signal (blood volume fraction) from the tissue signal shortly after injection and quantifications of vascular leakage into the extravascular tissue over time. This method allowed for the sensitive detection of increased blood vascularity and leakage rates in K14-VEGF-A transgenic mice and also reliably measured inflammation-induced changes of vascularity and leakage over time in the same mice. Measurements after injection of recombinant VEGF-A surprisingly revealed increased blood vascular leakage and lymphatic clearance in K14-VEGF-C transgenic mice which have an expanded cutaneous lymphatic vessel network, potentially indicating unanticipated effects of lymphatic drainage on vascular leakage. Increased vascular leakage was also detected in subcutaneous tumors, confirming that the method can also be applied to deeper tissues. This new imaging method might facilitate longitudinal investigations of the in vivo effects of drug candidates, including angiogenesis inhibitors, in preclinical disease models.

Near-infrared Optical Imaging of Exposed Phosphatidylserine in a Mouse Glioma Model

Phosphatidylserine (PS) is normally intracellular but becomes exposed on the luminal surface of vascular endothelial cells in tumors. It also becomes exposed on tumors cells responding to therapy. In the present study, we optically imaged exposed PS in vivo using PGN635, a novel monoclonal antibody that binds PS. The F(ab′)2 fragment of PGN635 was labeled with the near-infrared (NIR) dye, IRDye800CW. In vivo dynamic NIR imaging was performed after injection of 800CW-PGN635 into mice bearing radiation-treated or untreated U87 glioma xenografts growing subcutaneously or orthotopically. NIR optical imaging revealed a clear tumor contrast in nonirradiated subcutaneous U87 gliomas after injection of 800CW-PGN635. The tumor contrast was visible as early as 4 hours later and was maximal 24 hours later (tumor-to-normal tissue ratio [TNR] = 2.8 ± 0.7). Irradiation enhanced the tumor contrast at 24 hours (TNR = 4.0 ± 0.3). Similar results were observed for orthotopic gliomas. Localization of 800CW-PGN635 to tumors was antigen specific because 800CW-Aurexis, a control probe of irrelevant specificity, did not localize to the tumors, and preadministration of unlabeled PGN635 blocked the uptake of 800CW-PGN635. Fluorescence microscopy confirmed that 800CW-PGN635 was binding to PS-positive vascular endothelial cells in nonirradiated gliomas. Irradiation of the gliomas increased PS exposure on both tumor vascular endothelial cells and tumor cells and gave rise to an increase in tumor contrast with 800CW-PGN635 that was predictive of the reduction in tumor growth. 800CW-PGN635 may be a useful new imaging probe for detection of exposed PS in tumors responding to therapy.

Abstract LB-277: Abnormal lymphatic drainage pathway and function in mice with lymph node metastases

Abstract The lymphatic system provides a major route of cancer cell dissemination from the primary lesion site, to regional draining lymph nodes (LNs), through the lymphatic to blood vasculatures, and ultimately to distant sites of metastasis. However, to date there has been no in vivo imaging technique available to demonstrate functional and structural changes of overall lymphatic system in response to tumor growth and metastasis. In order to elucidate whether there are spatial and temporal changes in lymphatic function and architecture during tumor progression, we employed a dynamic near-infrared (NIR) fluorescence imaging technique. C6/Lacz rat glioma cells were implanted intradermally into the tail at 1 to 2 cm caudal to the rectum or in the right hindlimb in balb/c nude mice. Mice with a tumor in the tail were imaged at three weeks post implantation and mice with a tumor in the hindlimb at two and three weeks after tumor inoculation. Dynamic NIR imaging with 200 ms exposure time was conducted after intradermal injection of indocyanine green (ICG) to the base of the mouse tail for a hindlimb tumor model and to the tail 2cm away from the tail tip for a tail tumor model. Our imaging data in mice with a tail tumor show no uptake of fluorophore in the lymphatic capillaries in the skin above the tumor, which is in agreement with previous reports. In addition, our results show greater staining of lymphatic capillary network to the distal tumor periphery, dilated and tortuous collecting lymphatic vessels, and reduced or loss of propulsive lymphatic flow. Moreover, altered lymphatic drainage patterns and abnormal lymphatic flow from the collecting lymphatic vessel to the lymphatic capillaries at the distal tumor margin were detected. In a hindlimb tumor model, the lymphatic drainage pattern transiently changed with progressive disease. Mice with either the inguinal (primary) or axillary (secondary) LN metastasis showed dilated and leaky fluorescent lymphatic vessels, which circumvented the primary tumor and often the inguinal LN with a tumor and drained to the brachial LN. In one mouse with the inguinal and axillary LN metastases, ICG-labeled lymph drained across the midline of the animal body and thus to the left axillary LN. Magnified fluorescent images also show diffuse dye patterns. In addition, reduced lymphatic contractile function was seen in mice with LN metastasis. In summary, we showed in an animal model that gross cancer metastasis to the draining LNs is accompanied by abnormal lymphatic drainage pathway as well as reduced functional lymph propulsion in comparison to tumor-free mice. Therefore, this emerging NIR fluorescence imaging technology can be used to non-invasively and quantitatively detect functional lymphatic changes associated with cancer, which may enable accurate nodal staging of cancer patients and provide new approaches to diagnoses and therapies against cancer metastasis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-277.

A prospective pilot clinical trial evaluating the utility of a dynamic near-infrared imaging device for characterizing suspicious breast lesions

IntroductionCharacterizing and differentiating between malignant tumors, benign tumors, and normal breast tissue is increasingly important in the patient presenting with breast problems. Near-infrared diffuse optical imaging and spectroscopy is capable of measuring multiple physiologic parameters of biological tissue systems and may have clinical applications for assessing the development and progression of neoplastic processes, including breast cancer. The currently available application of near-infrared imaging technology for the breast, however, is compromised by low spatial resolution, tissue heterogeneity, and interpatient variation.Materials and methodsWe tested a dynamic near-infrared imaging schema for the characterization of suspicious breast lesions identified on diagnostic clinical ultrasound. A portable handheld near-infrared tissue imaging device (P-Scan; ViOptix Inc., Fremont, CA, USA) was utilized. An external mechanical compression force was applied to breast tissue. The tissue oxygen saturation and hemoglobin concentration were recorded simultaneously by the handheld near-infrared imaging device. Twelve categories of dynamic tissue parameters were derived based on real-time measurements of the tissue hemoglobin concentration and the oxygen saturation.ResultsFifty suspicious breast lesions were evaluated in 48 patients. Statistical analyses were carried out on 36 out of 50 datasets that satisfied our inclusion criteria. Suspicious breast lesions identified on diagnostic clinical ultrasound had lower oxygenation and higher hemoglobin concentration than the surrounding normal breast tissue. Furthermore, histopathologic-proven malignant breast tumors had a lower differential hemoglobin contrast (that is, the difference of hemoglobin concentration variability between the suspicious breast lesion and the normal breast parenchyma located remotely elsewhere within the ipsilateral breast) as compared with histopathologic-proven benign breast lesions.ConclusionThe proposed dynamic near-infrared imaging schema has the potential to differentiate benign processes from those of malignant breast tumors. Further development and refinement of the dynamic imaging device and additional subsequent clinical testing are necessary for optimizing the accuracy of detection.