In vivo imaging of mice auricle vessels using adaptive optical confocal fluorescence microscope

Facilitated with stochastic parallel gradient descent(SPGD) algorithm for wavefront sensorless correcting aberrations, an adaptive optics(AO) confocal fluorescence microscopy is developed and used to record fluorescent signals in vivo. Vessels of mice auricle at 80, 100 and 120 μm depth are obtained, and image contrast and fluorescence intensity are significantly improved with AO correction. The typical 10%–90% rise-time of the metric value measured is 5.0 s for a measured close-loop bandwidth of 0.2 Hz. Therefore, the AO confocal microscopy implemented with SPGD algorithm for robust AO corrections will be a powerful tool for study of vascular dynamics in future.     

Label-free 3D imaging of microstructure, blood, and lymphatic vessels within tissue beds in vivo

This Letter reports the use of an ultrahigh resolution optical microangiography (OMAG) system for simultaneous 3D imaging of microstructure and lymphatic and blood vessels without the use of an exogenous contrast agent. An automatic algorithm is developed to segment the lymphatic vessels from the microstructural images based on the fact that the lymph fluid is optically transparent. An OMAG system is developed that utilizes a broadband supercontinuum light source, providing an axial resolution of 2.3 μm and lateral resolution of 5.8 μm, capable of resolving the capillary vasculature and lymphatic vessels innervating microcirculatory tissue beds. Experimental demonstration is performed by showing detailed 3D lymphatic and blood vessel maps, coupled with morphology, within mouse ears in vivo.     

In vivo brain imaging using a portable 3.9 gram two-photon fluorescence microendoscope

We introduce a compact two-photon fluorescence microendoscope based on a compound gradient refractive index endoscope probe, a DC micromotor for remote adjustment of the image plane, and a flexible photonic bandgap fiber for near distortion-free delivery of ultrashort excitation pulses. The imaging head has a mass of only 3.9 g and provides micrometer-scale resolution. We used portable two-photon microendoscopy to visualize hippocampal blood vessels in the brains of live mice.     

In vivo quantitation of water content in muscle tissues by NMR imaging.

The water contents of phantoms and muscle tissues were determined directly from NMR imaging experiments. The method involves the calculation of corrected proton densities using relaxation time determinations and suitable calibration phantoms. Comparison with the values obtained from the oven-dry method yields good agreement in normal rat skeletal tissue and in rats injected with red blood cells from sickle cell patients.     

In vivo interactions of magnetic nanoparticles with the blood-brain barrier

Targeted drug delivery to the brain parenchyma, i.e., in brain tumor patients, by means of magnetically supported carrier delivery through the tight vascular endothelium of the blood-brain barrier is of critical biomedical importance. We were interested in delineating the first steps in successful brain drug delivery, which focuses on the interactions between magnetically guided yet freely blood circulating nanoparticles and the blood-brain barrier. We employed an in vivo model to quantitatively determine changes in cerebrovascular flow rate and volume during magnetically guided exposure of circulating nanoparticles.     

High-resolution in vivo imaging of blood vessels without labeling

We demonstrate that both oxyhemoglobin and deoxyhemoglobin have sequential two-color, two-photon absorption properties that can serve as endogenous contrasts in microvasculature imaging. Using a sensitive modulation transfer technique, we are able to image hemoglobin in red blood cells with micrometer resolution, both in vitro and in vivo. We show that excellent contrast from hemoglobin without any labeling can be obtained in tissue.     

In vivo whole-body imaging of optical agent dynamics using full angle fluorescence diffuse optical tomography

Dynamic fluorescence diffuse optical tomography （FDOT） is important in drug deliver research. In this letter, we first image the metabolic processes of micelles indocyanine green throughout the whole body of a nude mouse using the full-angle FDOT system with line illumination （L-FDOT）. The resolution of L-FDOT is evaluated using phantom experiment. Next, in vivo dynamic tomographic images （100 frames; approximately 170 min） of mouse liver and abdomen are shown and cross-validated by planar fluorescence reflectance imaging in vitro. Results provide evidence on applicability of the tomographic image wholebody biological activities in vivo on minute timescale （approximately 1.7 min） using L-FDOT.     

Laser-induced fluorescence imaging of acetone inside evaporating and burning fuel droplets

Laser-induced fluorescence was used to visualize acetone fields inside individual droplets of pure acetone as well as droplets composed of methanol or 1-propanol initially mixed with acetone. Droplets were supported on a horizontal wire and two vaporization conditions were investigated: (1) slow evaporation in room air and (2) droplet combustion, which leads to substantially faster droplet surface regression rates. Acetone was preferentially gasified, causing its concentration in droplets to drop in time with resultant decreases in acetone fluorescence intensities. Slowly vaporizing droplets did not exhibit large spatial variations of fluorescence within droplets, indicating that these droplets were relatively well mixed. Ignition of droplets led to significant variations in fluorescence intensities within droplets, indicating that these droplets were not well mixed. Ignited droplets composed of mixtures of 1-propanol and acetone showed large time-varying changes in shapes for higher acetone concentrations, suggesting that bubble formation was occurring in these droplets.     

In vitro and in vivo investigations of targeted chemotherapy with magnetic nanoparticles

Magnetic drug targeting is a local drug delivery system. Electromicroscopic pictures document the ferrofluid enrichment in the intracellular space in vitro. In vivo experiments were performed in VX2 tumor-bearing rabbits using magnetic nanoparticles bound to mitoxantrone. High-pressure liquid chromatography (HPLC) analyses after magnetic drug targeting showed an increasing concentration of the chemotherapeutic agent in the tumor region compared to regular systemic chemotherapy.     

In vivo echo-planar imaging of rat spinal cord

An integrated approach to echo-planar imaging of rat spinal cord in vivo with a small field of view (FOV) is presented. This protocol is based on a multishot interleaved echo-planar imaging (EPI) sequence and includes: 1) use of an inductively coupled implantable coil for improved signal-to-noise ratio (SNR); 2) three-dimensional (3D) automatic shimming of the magnetic field over the spinal cord; and 3) post-acquisition data processing using a multireference scan for minimizing image artifacts. Some of the practical issues in implementing this protocol are discussed. This imaging protocol will be useful in characterizing the spinal cord pathology using techniques that are otherwise time-consuming, such as diffusion tensor imaging.     

In vivo visualization of displacement-distribution-derived parameters in q-space imaging

OBJECTIVE: This study aimed to explore the potential of in vivo q-space imaging in the differentiation between different cerebral water components. MATERIALS AND METHODS: Diffusion-weighted imaging was performed in six directions with 32 equally spaced q values and a maximum b value of 6600 s/mm(2). The shape of the signal-attenuation curve and the displacement propagator were examined and compared with a normal distribution using the kurtosis parameter. Maps displaying kurtosis, fast and slow components of the apparent diffusion coefficients, fractional anisotropy and directional diffusion were calculated. The displacement propagator was further described by the full width at half and at tenth maximum and by the probability density of zero displacement P(0). Three healthy volunteers and three patients with previously diagnosed multiple sclerosis (MS) were examined. RESULTS: Simulations indicated that the kurtosis of a signal-attenuation curve can determine if more than one water component is present and that care must be taken to select an appropriate threshold. It was possible to distinguish MS plaques in both signal and diffusional kurtosis maps, and in one patient, plaques of different degree of demyelinization showed different behavior. DISCUSSION: Our results indicate that in vivo q-space analysis is a potential tool for the assessment of different cerebral water components, and it might extend the diagnostic interpretation of data from diffusion magnetic resonance imaging.     

In vivo imaging of the human rod photoreceptor mosaic

Although single cone receptors have been imaged in vivo, to our knowledge there has been no observation of rods in the living normal eye. Using an adaptive optics ophthalmoscope and post processing, evidence of a rod mosaic was observed at 5° and 10° eccentricities in the horizontal temporal retina. For four normal human subjects, small structures were observed between the larger cones and were observed repeatedly at the same locations on different days, and with varying wavelengths. Image analysis gave spacings that agree well with rod measurements from histological data.     

Anti-inflammatory/infection PLA nanoparticles labeled with technetium 99m for in vivo imaging

Despite advancements in treatment of infectious diseases, opportunistic pathogens continue to pose a worldwide threat. Identifying a source of infection/inflammation is often challenging which highlights the need of improved diagnostic agents. Using a model of local S. aureus infection, here we evaluated the potential of betamethasone or dexamethasone loaded in poly (lactic acid) nanoparticles and radiolabeled with 99mTc to detect an infection/inflammation site in vivo. A betamethasone and dexamethasone nanoparticles (NPs) with 200 and 220 nm in size, respectively, were created with a 98% 99mTc radiolabeling efficiency. When injected in infected mice, betamethasone NPs presented a higher accumulation in the infected hind paw in comparison with dexamethasone NPs. Our results suggest that this nanosystem may be a valid nanoradiopharmaceutical for the detection of inflammation/infection foci in vivo.

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Graphical abstract Nanoradiopharmaceutical for inflammation

     

In vivo photoacoustic time-of-flight velocity measurement of single cells and nanoparticles

Optical techniques for in vivo measurement of blood flow velocity are not quite applicable for determination of velocity of individual cells or nanoparticles. Here, we describe a photoacoustic time-of-flight method to measure the velocity of individual absorbing objects by using single and multiple laser beams. Its capability was demonstrated in vitro on blood vessel phantom and in vivo on an animal (mouse) model for estimating velocity of gold nanorods, melanin nanoparticles, erythrocytes, leukocytes, and circulating tumor cells in the broad range of flow velocity from 0.1?mm/s to 14?cm/s. Object velocity can be used to identify single cells circulating at different velocities or cell aggregates and to determine a cell's location in a vessel cross-section.     

In vivo video rate multiphoton microscopy imaging of human skin

We present a multiphoton microscopy instrument specially designed for in vivo dermatological use that is capable of imaging human skin at 27 frames per second with 256 pixels × 256 pixels resolution without the use of exogenous contrast agents. Imaging at fast frame rates is critical to reducing image blurring due to patient motion and to providing practically short clinical measurement times. Second harmonic generation and two-photon fluorescence images and videos acquired at optimized wavelengths are presented showing cellular and tissue structures from the skin surface down to the reticular dermis.     

Microscopic fluorescence imaging of bulk defect clusters in KH(2)PO(4) crystals

A microscopic fluorescence imaging system is used to detect optically active centers located inside a transparent dielectric crystal. Defect centers in the bulk of KH(2)PO(4) crystals are imaged based on their near-infrared emission following photoexcitation. The spatial resolution of the system is 1mum in the image plane and 25mum in depth. The experimental results indicate the presence of a large number of optically active defect clusters in different KH(2)PO(4) crystals, whereas the concentration of these clusters depends on the crystal sector and growth method.     

In vivo confocal imaging of fast intrinsic optical signals correlated with frog retinal activation

Using freshly isolated animal retinas, we have conducted a series of experiments to test fast intrinsic optical signals (IOSs) that have time courses comparable to electrophysiological kinetics. In this Letter, we demonstrate the feasibility of in vivo imaging of fast IOSs in intact frogs. A rapid line-scan confocal ophthalmoscope was constructed to achieve high-speed IOS recording. By rejecting out-of-focus background light, the line-scan confocal imager provided the resolution to differentiate individual photoreceptors in vivo. Rapid confocal imaging disclosed robust IOSs with time courses comparable to retinal electroretinogram kinetics. High-resolution IOS images revealed both positive (increasing) and negative (decreasing) light responses, with subcellular complexity.     

Planar laser-induced fluorescence imaging of carbon monoxide using vibrational (infrared) transitions

We report a new imaging diagnostic suitable for measurements of infrared-active molecules, namely infrared planar laser-induced fluorescence (IR PLIF), in which a tunable infrared source is used to excite vibrational transitions in molecules and vibrational fluorescence is collected by an infrared camera. A nanosecond-pulse Nd:YAG-pumped KTP/KTA OPO/OPA system is used to generate 12 mJ of tunable output near 2.35 μm which excites the 2ν band of carbon monoxide (CO); fluorescence resulting from excited CO is collected at 4.7 μm by using an InSb focal plane array. Quantitative, high-SNR PLIF imaging of gas-phase CO is demonstrated at a 10-Hz acquisition rate with a minimum detection limit of 1350 ppm at 300 K. Received: 30 July 1999 / Published online: 16 September 1999