430 research outputs found

    Experimental Study on Bioluminescence Tomography with Multimodality Fusion

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    To verify the influence of a priori information on the nonuniqueness problem of bioluminescence tomography (BLT), the multimodality imaging fusion based BLT experiment is performed by multiview noncontact detection mode, which incorporates the anatomical information obtained by the microCT scanner and the background optical properties based on diffuse reflectance measurements. In the reconstruction procedure, the utilization of adaptive finite element methods (FEMs) and a priori permissible source region refines the reconstructed results and improves numerical robustness and efficiency. The comparison between the absence and employment of a priori information shows that multimodality imaging fusion is essential to quantitative BLT reconstruction

    Multimodality Imaging of β-Cells in Mouse Models of Type 1 and 2 Diabetes

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    Objectiveβ-Cells that express an imaging reporter have provided powerful tools for studying β-cell development, islet transplantation, and β-cell autoimmunity. To further expedite diabetes research, we generated transgenic C57BL/6 "MIP-TF" mice that have a mouse insulin promoter (MIP) driving the expression of a trifusion (TF) protein of three imaging reporters (luciferase/enhanced green fluorescent protein/HSV1-sr39 thymidine kinase) in their β-cells. This should enable the noninvasive imaging of β-cells by charge-coupled device (CCD) and micro-positron emission tomography (PET), as well as the identification of β-cells at the cellular level by fluorescent microscopy.Research design and methodsMIP-TF mouse β-cells were multimodality imaged in models of type 1 and type 2 diabetes.ResultsMIP-TF mouse β-cells were readily identified in pancreatic tissue sections using fluorescent microscopy. We show that MIP-TF β-cells can be noninvasively imaged using microPET. There was a correlation between CCD and microPET signals from the pancreas region of individual mice. After low-dose streptozotocin administration to induce type 1 diabetes, we observed a progressive reduction in bioluminescence from the pancreas region before the appearance of hyperglycemia. Although there have been reports of hyperglycemia inducing proinsulin expression in extrapancreatic tissues, we did not observe bioluminescent signals from extrapancreatic tissues of diabetic MIP-TF mice. Because MIP-TF mouse β-cells express a viral thymidine kinase, ganciclovir treatment induced hyperglycemia, providing a new experimental model of type 1 diabetes. Mice fed a high-fat diet to model early type 2 diabetes displayed a progressive increase in their pancreatic bioluminescent signals, which were positively correlated with area under the curve-intraperitoneal glucose tolerance test (AUC-IPGTT).ConclusionsMIP-TF mice provide a new tool for monitoring β-cells from the single cell level to noninvasive assessments of β-cells in models of type 1 diabetes and type 2 diabetes

    Fluorescence molecular tomography: Principles and potential for pharmaceutical research

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    Fluorescence microscopic imaging is widely used in biomedical research to study molecular and cellular processes in cell culture or tissue samples. This is motivated by the high inherent sensitivity of fluorescence techniques, the spatial resolution that compares favorably with cellular dimensions, the stability of the fluorescent labels used and the sophisticated labeling strategies that have been developed for selectively labeling target molecules. More recently, two and three-dimensional optical imaging methods have also been applied to monitor biological processes in intact biological organisms such as animals or even humans. These whole body optical imaging approaches have to cope with the fact that biological tissue is a highly scattering and absorbing medium. As a consequence, light propagation in tissue is well described by a diffusion approximation and accurate reconstruction of spatial information is demanding. While in vivo optical imaging is a highly sensitive method, the signal is strongly surface weighted, i.e., the signal detected from the same light source will become weaker the deeper it is embedded in tissue, and strongly depends on the optical properties of the surrounding tissue. Derivation of quantitative information, therefore, requires tomographic techniques such as fluorescence molecular tomography (FMT), which maps the three-dimensional distribution of a fluorescent probe or protein concentration. The combination of FMT with a structural imaging method such as X-ray computed tomography (CT) or Magnetic Resonance Imaging (MRI) will allow mapping molecular information on a high definition anatomical reference and enable the use of prior information on tissue’s optical properties to enhance both resolution and sensitivity. Today many of the fluorescent assays originally developed for studies in cellular systems have been successfully translated for experimental studies in animals. The opportunity of monitoring molecular processes non-invasively in the intact organism is highly attractive from a diagnostic point of view but even more so for the drug developer, who can use the techniques for proof-of-mechanism and proof-of-efficacy studies. This review shall elucidate the current status and potential of fluorescence tomography including recent advances in multimodality imaging approaches for preclinical and clinical drug development

    Molecular Imaging in Tumor Angiogenesis and Relevant Drug Research

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    Molecular imaging, including fluorescence imaging (FMI), bioluminescence imaging (BLI), positron emission tomography (PET), single-photon emission-computed tomography (SPECT), and computed tomography (CT), has a pivotal role in the process of tumor and relevant drug research. CT, especially Micro-CT, can provide the anatomic information for a region of interest (ROI); PET and SPECT can provide functional information for the ROI. BLI and FMI can provide optical information for an ROI. Tumor angiogenesis and relevant drug development is a lengthy, high-risk, and costly process, in which a novel drug needs about 10–15 years of testing to obtain Federal Drug Association (FDA) approval. Molecular imaging can enhance the development process by understanding the tumor mechanisms and drug activity. In this paper, we focus on tumor angiogenesis, and we review the characteristics of molecular imaging modalities and their applications in tumor angiogenesis and relevant drug research

    Cerenkov Luminescence Tomography for In Vivo Radiopharmaceutical Imaging

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    Cerenkov luminescence imaging (CLI) is a cost-effective molecular imaging tool for biomedical applications of radiotracers. The introduction of Cerenkov luminescence tomography (CLT) relative to planar CLI can be compared to the development of X-ray CT based on radiography. With CLT, quantitative and localized analysis of a radiopharmaceutical distribution becomes feasible. In this contribution, a feasibility study of in vivo radiopharmaceutical imaging in heterogeneous medium is presented. Coupled with a multimodal in vivo imaging system, this CLT reconstruction method allows precise anatomical registration of the positron probe in heterogeneous tissues and facilitates the more widespread application of radiotracers. Source distribution inside the small animal is obtained from CLT reconstruction. The experimental results demonstrated that CLT can be employed as an available in vivo tomographic imaging of charged particle emitters in a heterogeneous medium

    Investigating the Mechanisms of Breast Cancer Metastasis Using Multimodality Molecular Imaging

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    Introduction: Breast cancer recurrence continues to be a significant challenge in the clinic. Despite successful removal and/or treatment of the original tumour, many patients experience relapse in the breast or at distant sites. Furthermore, the diagnosis of metastatic disease often occurs too late for effective treatment. Methods: In this thesis, we combine iron-based cellular MRI and longitudinal BLI to noninvasively track the fate of cancer cells into overt tumours in the mouse brain. We then apply this imaging model to study the effect of a primary breast tumour on the growth of secondary metastases in an immune competent mouse model. Finally, we utilized dual-luciferase BLI to investigate the potential of self-homing circulating tumour cells (CTCs) as a novel cancer theranostic in both orthotopic and metastatic models of breast cancer. Results: BLI complemented our cellular MRI technologies well by providing longitudinal measures of cancer cell viability. Using in vivo BLI/MRI, we demonstrated the presence of a 4T1 primary tumour significantly enhances total brain tumour burden. Finally, using dual-luciferase BLI, we demonstrated the ability of experimental CTCs to home to and treat primary tumours and disseminated breast cancer lesions. Conclusion: MRI and BLI are complementary technologies to noninvasively study the fate of breast cancer cells, as well as the mechanisms contributing to metastasis including CTR/CTE and tumour self-homing. Furthermore, we provide evidence that CTCs are a novel theranostic platform for the visualization and treatment of pre-established tumour sites throughout the body

    U-SPECT-BioFluo: an integrated radionuclide, bioluminescence, and fluorescence imaging platform

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    Background: In vivo bioluminescence, fluorescence, and single-photon emission computed tomography (SPECT) imaging provide complementary information about biological processes. However, to date these signatures are evaluated separately on individual preclinical systems. In this paper, we introduce a fully integrated bioluminescence-fluorescence-SPECT platform. Next to an optimization in logistics and image fusion, this integration can help improve understanding of the optical imaging (OI) results. Methods: An OI module was developed for a preclinical SPECT system (U-SPECT, MILabs, Utrecht, the Netherlands). The applicability of the module for bioluminescence and fluorescence imaging was evaluated in both a phantom and in an in vivo setting using mice implanted with a 4 T1-luc + tumor. A combination of a fluorescent dye and radioactive moiety was used to directly relate the optical images of the module to the SPECT findings. Bioluminescence imaging (BLI) was compared to the localization of the fluorescence signal in the tumors. Results: Both the phantom and in vivo mouse studies showed that superficial fluorescence signals could be imaged accurately. The SPECT and bioluminescence images could be used to place the fluorescence findings in perspective, e.g. by showing tracer accumulation in non-target organs such as the liver and kidneys (SPECT) and giving a semi-quantitative read-out for tumor spread (bioluminescence). Conclusions: We developed a fully integrated multimodal platform that provides complementary registered imaging of bioluminescent, fluorescent, and SPECT signatures in a single scanning session with a single dose of anesthesia. In our view, integration of these modalities helps to improve data interpretation of optical findings in relation to radionuclide images

    Camelid reporter gene imaging: a generic method for in vivo cell tracking

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    BACKGROUND: To combine the sensitivity of bioluminescent imaging (BLI) with the 3D and quantitative properties of pinhole single-photon emission computed tomography (SPECT)/micro-computed tomography (CT) (phSPECT/micro-CT), we generated stable cell lines that express a yellow-fluorescent protein (YFP) and Gaussia luciferase (GLuc) fusion protein (YFP/GLuc). For in vivo phSPECT detection of this YFP/GLuc protein, a nanobody, targeted against yellow and green fluorescent proteins (anti-YFP-Nb), was site specifically labelled with (99m)Tc. METHODS: Human embryonic kidney cells (HEK293T) were cultured and passaged every 3 days. 10E5 cells were transduced with YFP/GLuc-containing vector: both membrane-targeted (MT-YFP/GLuc) and non-targeted (YFP/GLuc) fusion proteins were developed. These vectors were compared against a SKOV-3 cell line stably expressing green fluorescent-firefly luciferase (GFP/Fluc) and HEK293T cells expressing red fluorescent protein in combination with a Gaussia luciferase (Red/GLuc). Transduction efficiencies were scored by fluorescence microscopy, and transduced cells were enriched by fluorescence-activated cell sorting (FACS). GLuc and FLuc functionality was tested in vitro by list-mode BLI. Subsequently, cells were transplanted subcutaneously in athymic (nu/nu) mice (MT-YFP/GLuc: n = 4, YFP/GLuc: n = 6, GFP/FLuc: n = 6, Red/GLuc: n = 4). Labelling efficiency of anti-YFP-Nb was measured using instant thin layer chromatography. One week after transplantation, (99m)Tc-labelled anti-YFP-Nb was injected intravenously and pinhole (ph) SPECT/micro-CT was performed, followed by in vivo BLI. RESULTS: Cells showed high levels of fluorescence after transduction. The cells containing the MT-YFP/GLuc were positive on fluorescence microscopy, with the fluorescent signal confined to the cell membrane. After cell sorting, transduced cells were assayed by BLI and showed a significantly higher light output both in vitro and in vivo compared with non-transduced HEK293T cells. The anti-YFP-Nb labelling efficiency was 98%, and subsequent phSPECT/micro-CT demonstrated visible cell binding and significantly higher transplant-to-muscle ratio for both the MT-YFP/GLuc and YFP/GLuc transplanted cells, compared with the GFP/FLuc and Red/GLuc group. CONCLUSION: This study provides a proof of principle for a nanobody-based cell tracking method, using a YFP/GLuc fusion protein and anti-YFP-Nb in a model of subcutaneously transplanted transduced HEK293T cells

    Multimodality imaging in vivo for preclinical assessment of tumor-targeted doxorubicin nanoparticles.

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    This study presents a new multimodal imaging approach that includes high-frequency ultrasound, fluorescence intensity, confocal, and spectral imaging to improve the preclinical evaluation of new therapeutics in vivo. Here we use this approach to assess in vivo the therapeutic efficacy of the novel chemotherapy construct, HerDox during and after treatment. HerDox is comprised of doxorubicin non-covalently assembled in a viral-like particle targeted to HER2+ tumor cells, causing tumor cell death at over 10-fold lower dose compared to the untargeted drug, while sparing the heart. Whereas our initial proof-of-principle studies on HerDox used tumor growth/shrinkage rates as a measure of therapeutic efficacy, here we show that multimodal imaging deployed during and after treatment can supplement traditional modes of tumor monitoring to further characterize the particle in tissues of treated mice. Specifically, we show here that tumor cell apoptosis elicited by HerDox can be monitored in vivo during treatment using high frequency ultrasound imaging, while in situ confocal imaging of excised tumors shows that HerDox indeed penetrated tumor tissue and can be detected at the subcellular level, including in the nucleus, via Dox fluorescence. In addition, ratiometric spectral imaging of the same tumor tissue enables quantitative discrimination of HerDox fluorescence from autofluorescence in situ. In contrast to standard approaches of preclinical assessment, this new method provides multiple/complementary information that may shorten the time required for initial evaluation of in vivo efficacy, thus potentially reducing the time and cost for translating new drug molecules into the clinic
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